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 Discourses, biological and geological- 
 
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Huxley's Works 
 
 Discourses 
 
 AUTHOR'S EDITION 
 
 Limited to one thousand copies 
 
Photogravure after a portrait of Thomas H. Huxley, 
 
 painted in 1883 by the Honorable John Collier, the 
 
 son-in-law of Professor Huxley. 
 
DISCOURSES 
 
 BIOLOGICAL AND GEOLOGICAL 
 
 ESSAYS 
 
 By Thomas H. Huxley 
 
 D. APPLETON AND COMPANY 
 NEW YORK AND LONDON 
 
Authorized Edition. 
 
 Limited to one thousand copies, 
 of which this is No. A.4.J 
 
 
PREFACE. 
 
 The Mintents of the present volume, with 
 three exceptions, are either popular lectures, or ad- 
 dresses delivered to scientific bodies with which I 
 have been officially connected. I am not sure 
 which gave me the more trouble. For I have not 
 been one of those fortunate persons who are able 
 to regard a popular lecture as a mere hors d'ceuvre, 
 unworthy of being ranked among the serious ef- 
 forts of a philosopher; and who keep their fame 
 as scientific hierophants unsullied by attempts — 
 at least of the successful sort — to be understanded 
 of the people. 
 
 On the contrary, I found that the task of 
 putting the truths learned in the field, the labora- 
 tory and the museum, into language which, with- 
 out bating a Jot of scientific accuracy shall be gen- 
 erally intelligible, taxed such scientific and literary 
 faculty as I possessed to the uttermost; indeed 
 my experience has furnished me with no better 
 corrective of the tendency to scholastic pedantry 
 which besets all those who are absorbed in pur- 
 
vi PREFACE. 
 
 suits remote from the common ways of men, and 
 become habituated to think and speak in the tech- 
 nical dialect of their own little world, as if there 
 were no other. 
 
 If the popular lecture thus, as I believe, finds 
 one moiety of its justification in the self-discipline 
 of the lecturer, it surely finds the other half in its 
 effect on the auditory. For though various sadly 
 comical experiences of the results of my own ef- 
 forts have led me to entertain a verj^ moderate 
 estimate of the purely intellectual value of lec- 
 tures; though I venture to doubt if more than one 
 in ten of an average audience carries away an 
 accurate notion of what the speaker has been 
 driving at; yet is that not equally true of the 
 oratory of the hustings, of the House of Commons, 
 and even of the pulpit? 
 
 Yet the children of this world are wise in their 
 generation; and both the politician and the priest 
 are justified by results. The living voice has an 
 influence over human action altogether independ- 
 ent of the intellectual worth of that which it 
 utters. Many years ago, I was a guest at a great 
 City dinner. A famous orator, endowed with a 
 voice of rare flexibility and power; a born actor, 
 ranging with ease through every part, from refined 
 comedy to tragic unction, was called upon to reply 
 to a toast. The orator was a very busy man, a 
 charming conversationalist and by no means de- 
 spised a good dinner; and, I imagine, rose with- 
 
PREFACE. vii 
 
 out having given a thought to what he was going 
 to say. The rhythmic roll of sound was admirable, 
 the gestures perfect, the earnestness impressive; 
 nothing was lacking save sense and, occasionally, 
 grammar. When the speaker sat down the ap- 
 plause was terrific and one of my neighbours was 
 especially enthusiastic. So when he had quieted 
 down, I asked him what the orator had said. And 
 he could not tell me. 
 
 That sagacious person, John Wesley, is re- 
 ported to have replied to some one who questioned 
 the propriety of his adaptation of sacred words to 
 extremely secular airs, that he did not see why the 
 Devil should be left in possession of all the best 
 tunes. And I do not see why science should not 
 turn to account the peculiarities of human nature 
 thus exploited by other agencies; all the more 
 because science, by the nature of its being, can- 
 not desire to stir the passions, or profit by the 
 weaknesses, of human nature. The most zealous 
 of popular lecturers can aim at nothing more 
 than the awakening of a sympathy for abstract 
 truth, in those who do not really follow his argu- 
 ments; and of a desire to know more and better 
 in the few who do. 
 
 At the same time it must be admitted that the 
 popularisation of science, whether by lecture or 
 essay, has its drawbacks. Success in this depart- 
 ment has its perils for those who succeed. The 
 " people who fail " take their revenge, as we have 
 
viii PREFACE. 
 
 recently had occasion to observe, by ignoring all 
 the rest of a man's work and glibly labelling him 
 a mere populariser. ' If the falsehood were not too 
 glaring, they would say the same of Faraday and 
 Helmholtz and Kelvin. 
 
 On the other hand, of the affliction caused by 
 persons who think that what they have picked up 
 from popular exposition qualiiies them for discuss- 
 ing the great problems of science, it may be said, 
 as the Eadical toast said of the power of the 
 Crown in bygone days, that it " has increased, is 
 increasing, and ought to be diminished." The odd- 
 ities of " English as she is spoke " might be abun- 
 dantly paralleled by those of " Science as she is 
 misunderstood " in the sermon, the novel, and the 
 leading article; and a collection of the grotesque 
 travesties of scientific conceptions, in the shape 
 of essays on such trifles as " the Nature of Life," 
 and the " Origin of All Things," which reach me, 
 from time to time, might well be bound up with 
 them. 
 
 The tenth essay in this volume unfortunately 
 brought me, I will not say into collision, but into 
 a position of critical remonstrance with regard 
 to some charges of physical heterodoxy, brought 
 by my distinguished friend Lord Kelvin, against 
 British Geology. As President of the Geological 
 Society of London at that time (1869), I thought 
 I might venture to plead that we were not such 
 
PRBFACB, ix 
 
 heretics as we seemed to be; and that, even if 
 we were, recantation would not affect the question 
 of evolution. 
 
 I am glad to see that Lord Kelvin has just 
 reprinted his reply to my plea,* and I refer the 
 reader to it. I shall not presume to question any- 
 thing, that on such ripe consideration. Lord Kel- 
 vin has to say upon the physical problems involved. 
 But I may remark that no one can have asserted 
 more strongly than I have done, the necessity of 
 looking to physics and mathematics for help in 
 regard to the earliest history of the globe. (See 
 pp. 108 and 109 of this volume.) 
 
 And I take the opportunity of repeating the 
 opinion, that, whether what we call geological 
 time has the lower limit assigned to it by Lord 
 Kelvin, or the higher assumed by other philoso- 
 phers; whether the germs of all living things have 
 originated in the globe itself, or whether they 
 have been imported on, or in, meteorites from 
 without, the problem of the origin of those suces- 
 sive Faunae and Florae of the earth, the existence 
 of which is fully demonstrated by palseontology, 
 remains exactly where it was. 
 
 For I think it will be admitted, that the germs 
 brought to us by meteorites, if any, were not ova 
 of elephants, nor of crocodiles; nor cocoa-nuts nor 
 acorns; not even eggs of shell-fish and corals; but 
 
 * Popular Lectures and Addresses. II. Macmillan 
 and Co. 1894. 
 
X PREFACE. 
 
 only those of the lowest forms of animal and veg- 
 etable life. Therefore, since it is proved that from 
 a very remote epoch of geological time, the earth 
 has been peopled by a continual succession of the 
 higher forms of animals and plants, these either 
 must have been created, or they have arisen by 
 evolution. And in respect of certain groups of 
 animals, the well-established facts of palaeontology 
 leave no rational doubt that they arose by the 
 latter method. 
 
 In the second place, there are no data what- 
 ever, which justify the biologist in assigning any, 
 even approximately definite, period of time, either 
 long or short, to the evolution of one species from 
 another by the process of variation and selection. 
 In the ninth of the following essays, I have taken 
 pains to prove that the change of animals has 
 gone on at very different rates in different groups 
 of living beings; that some types have persisted 
 with little change from the paleozoic epoch till 
 now, while others have changed rapidly within 
 the limits of an epoch. In 1862 (see below p. 303, 
 304), in 1863 (vol. II., p. 461), and again in 1864 
 {ibid., p. 89 — 91) I argued, not as a matter of 
 speculation, but, from palseontological facts, the 
 bearing of which I believe, up to that time, had 
 not been shown, that any adequate hypothesis of 
 the causes of evolution must be consistent with 
 progression, stationariness, and retrogression, of 
 the same type at different epochs; of different 
 
PREFACE. xi 
 
 types in the same epoch; and that Darwin's hy- 
 pothesis fulfilled these conditions. 
 
 According to that hypothesis, two factors are 
 at work, variation and selection. Next to nothing 
 is known of the causes of the former process; noth- 
 ing whatever of the time required for the produc- 
 tion of a certain amount of deviation from the ex- 
 isting type. And, as respects selection, which op- 
 erates by extinguishing all but a small minority 
 of variations, we have not the slightest means of 
 estimating the rapidity with which it does its 
 work. All that we are Justified in saying is that 
 the rate at which it takes place may vary almost 
 indefinitely. If the famous paint-root of Florida, 
 which kills white pigs but not black ones, were 
 abundant and certain in its action, black pigs 
 might be substituted for white in the course of 
 two or three years. If, on the other hand, it was 
 rare and uncertain in action, the white pigs might 
 linger on for centuries. 
 
 T. H. HUXLET. 
 
 HoDESLEA, Eastbourne, 
 April, 1894. 
 
CONTENTS 
 
 I 
 
 PAOS 
 ON A PIECE OP CHALK [1868] . 1 
 
 (A Lecture delivered to the working men 
 of Norwich during the meeting of the 
 British Association.) 
 
 II 
 
 THE PROBLEMS OP THE DEEP SEA [1873] 37 
 
 III 
 
 ON SOME OP THE RESULTS OP THE EXPEDITION OP H.M.S. 
 
 " CHALLENGER " [1875] 70 
 
 IV 
 
 YEAST [1871] 113 
 
 xiii 
 
xiv CONTENTS 
 
 V 
 
 FAOK 
 ON THE FORMATION OP COAL [1870] 141 
 
 (A Lecture delivered at the Philosophical 
 Institute, Bradford.) 
 
 VI 
 
 ON THE BORDER TERRITORY BETWEEN THE ANIMAL AND 
 
 THE VEGETABLE KINGDOMS [1876] 165 
 
 (A Friday evening Lecture delivered at 
 the Royal Institution.) 
 
 VII 
 
 A LOBSTER; OR, THE STUDY OF ZOOLOGY [1861] . . . 199 
 
 (A Lecture delivered at the South Ken- 
 sington Museum.) 
 
 VIII 
 
 BIOGENESIS AND ABIOGBNESIS [1870] 233 
 
 (The Presidential Address to the Meeting 
 of the British Association for the Ad- 
 vancement of Science at Liverpool.) 
 
 IX 
 
 GEOLOGICAL CONTEMPORANEITY AND PERSISTENT TYPES 
 
 OP LIFE [1862] 275 
 
 (Address to the Geological Society on be- 
 half of the President by one of the Sec- 
 retaries.) 
 
CONTENTS XV 
 
 X 
 
 FAOE 
 GEOLOGICAL REFORM [1869] 308 
 
 (Presidential Address to the Geological 
 Society.) 
 
 XI 
 
 PALiEONTOLOQT AND THE DOCTRINE OF EVOLUTION [1870] 343 
 
 (Presidential Address to the Geological 
 Society.) 
 
ON A PIECE OF CHALK. 
 
 [1868.] 
 
 If a well were sunk at our feet in the midst of 
 the city of Norwich, the diggers would very soon 
 find themselves at work in that white substance 
 almost too soft to be called rock, with which we 
 are all familiar as " chalk." 
 
 Not only here, but over the whole county of 
 Norfolk, the well-sinker might carry his shaft 
 down many hundred feet without coming to the 
 end of the chalk; and, on the sea-coast, where 
 the waves have pared away the face of the land 
 which breasts them, the scarped faces of the high 
 cliffs are often wholly formed of the same material. 
 Northward, the chalk may be followed as far as 
 Yorkshire; on the south coast it appears abruptly 
 in the picturesque western bays of Dorset, and 
 breaks into the Needles of the Isle of Wight; 
 while on the shores of Kent it supplies that long 
 line of white cliffs to which England owes her 
 name of Albion. 
 
 Were the thin soil which covers it all washed 
 187 1 
 
2 ON A PIECE OF CHALK. i 
 
 away, a curved band of white chalk, here broader, 
 and there narrower, might be followed diagonally 
 across England from Lulworth in Dorset, to Flam- 
 borough Head in Yorkshire — a distance of over 
 280 miles as the crow flies. From this band to the 
 North Sea, on the east, and the Channel, on the 
 south, the chalk is largely hidden by other de- 
 posits; but, except in the Weald of Kent and Sus- 
 sex, it enters into the very foundation of all the 
 south-eastern counties. 
 
 Attaining, as it does in some places, a thickness 
 of more than a thousand feet, the English chalk 
 must be admitted to be a mass of considerable 
 magnitude. Nevertheless, it covers but an insig- 
 nificant portion of the whole area occupied by the 
 chalk formation of the globe, much of which has 
 the same general characters as ours, and is found 
 in detached patches, some less, and others more 
 extensive, than the English. Chalk occurs in 
 north-west Ireland; it stretches over a large part 
 of France, — the chalk which underlies Paris being, 
 in fact, a continuation of that of the London basin; 
 it runs through Denmark and Central Europe, and 
 extends southward to North Africa; while east- 
 ward, it appears in the Crimea and in Syria, and 
 may be traced as far as the shores of the Sea of 
 Aral, in Central Asia. If all the points at which 
 true chalk occurs were circumscribed, they would 
 lie within an irregular oval about 3,000 miles in 
 long diameter — the area of which would be as 
 
I ON A PIECE OF CHALK. 3 
 
 great as that of Europe, and would many times 
 exceed that of the largest existing inland sea — 
 the Mediterranean. 
 
 Thus the chalk is no unimportant element in 
 the masonry of the earth's crust, and it impresses 
 a peculiar stamp, varying with the conditions to 
 which it is exposed, on the scenery of the districts 
 in which it occurs. The undulating downs and 
 rounded coombs, covered with sweet-grassed turf, 
 of our inland chalk country, have a peacefully 
 domestic and mutton-suggesting prettiness, but 
 can hardly be called either grand or beautiful. 
 Bnt on our southern coasts, the wall-sided cliffs, 
 many hundred feet high, with vast needles and 
 pinnacles standing out in the sea, sharp and soli- 
 tary enough to serve as perches for the wary cor- 
 morant, confer a wonderful beauty and grandeur 
 upon the chalk headlands. And, in the East^ 
 chalk has its share in the formation of some of 
 the most venerable of mountain ranges, such as 
 the Lebanon. 
 
 What is this wide-spread component of the 
 surface of the earth? and whence did it come? 
 
 You may think this no very hopeful inquiry. 
 You may not unnaturally suppose that the at- 
 tempt to solve such problems as these can lead 
 to no result, save that of entangling the inquirer 
 in vague speculations, incapable of refutation and 
 of' verification. If such were really the case, I 
 
4 ON A PIECE OP CHALK. i 
 
 should have selected some other subject than a 
 " piece of chalk " for my discourse. But, in truth, 
 after much deliberation, I have been unable to 
 think of any topic which would so well enable me 
 to lead you to see how solid is the foundation upon 
 which some of the most startling conclusions of 
 physical science rest. 
 
 A great chapter of the history of the world is 
 written in the chalk. Few passages in the history 
 of man can be supported by such an overwhelm- 
 ing mass of direct and indirect evidence as that 
 which testifies to the truth of the fragment of the 
 history of the globe, which I hope to enable you 
 to read, with your own eyes, to-night. Let me 
 add, that few chapters of human history have a 
 more profound significance for ourselves. I weigh 
 my words well when I assert, that the man who 
 should know the true history of the bit of chalk 
 which every carpenter carries about in his 
 breeches-pocket, though ignorant of all other his- 
 tory, is likely, if he will think his knowledge out 
 to its ultimate results, to have a truer, and there- 
 fore a better, conception of this wonderful 
 universe, and of man's relation to it, than 
 the most learned student who is deep-read in 
 the records of humanity and ignorant of those of 
 Nature. 
 
 The language of the chalk is not hard to learn, 
 not nearly so hard as Latin, if you only want to 
 get at the broad feaitures of the story it has to 
 
I ON A PIECE OF CHALK. 5 
 
 tell; and I propose that we now set to work to 
 spell that story out together. 
 
 We all know that if we " hurn " chalk the 
 result is quicklime. Chalk, in fact, is a compound 
 of carbonic acid gas, and lime, and when you make 
 it very hot the carbonic acid flies away and the 
 lime is left. By this method of procedure we 
 see the lime, but we do not see the carbonic acid. 
 If, on the other hand, you were to powder a little 
 chalk and drop it into a good deal of strong vine- 
 gar, there would be a great bubbling and fizzing, 
 and, finally, a clear liquid, in which no sign of 
 chalk would appear. Here you see the carbonic 
 acid in the bubbles; the lime, dissolved in the 
 vinegar, vanishes from sight. There are a great 
 many other ways of showing that chalk is essen- 
 tially nothing but carbonic acid and quicklime. 
 Chemists enunciate the result of all the experi- 
 ments which prove this, by stating that chalk is 
 almost wholly composed of " carbonate of lime." 
 
 It is desirable for us to start from the knowl- 
 edge of this fact, though it may not seem to help 
 us very far towards what we seek. For carbonate 
 of lime is a widely-spread substance, and is met 
 with under very various conditions. All sorts of 
 limestones are composed of more or less pure car- 
 bonate of lime. The crust which is often de- 
 posited by waters which have drained through 
 limestone rocks, in the form of what are called 
 stalagmites and stalactites, is carbonate of lime. 
 
6 ON A PIECE OP CHALK. i 
 
 Or, to take a more familiar example, the fur on 
 the inside of a tea-kettle is carbonate of lime; 
 and, for anything chemistry tells us to the con- 
 trary, the chalk might be a kind of gigantic fur 
 upon the bottom of the earth-kettle, which is kept 
 pretty hot below. 
 
 Let us try another method of making the chalk 
 tell us its own history. To the unassisted eye 
 chalk looks simply like a very loose and open kind 
 of stone. But it is possible to grind a slice of 
 chalk down so thin that you ean see through it 
 — until it is thin enough, in fact, to be examined 
 .with any magnifying power that may be thought 
 desirable. A thin slice of the fur of a kettle 
 might be made in the same way. If it were 
 examined microscopically, it would show itself to 
 be a more or less distinctly laminated mineral sub- 
 stance, and nothing more. 
 
 But the slice of chalk presents a totally differ- 
 ent, appearance when placed under the microscope. 
 The general mass of it is made up of very minute 
 granules; but, imbedded in this matrix, are in- 
 numerable bodies, some smaller and some larger, 
 but, on a rough average, not more than a hun- 
 dredth of an inch in diameter, having a well-de- 
 .fined shape and structure. A cubic inch of some 
 specimens of chalk may contain hundreds of thou- 
 sands of these bodies, compacted together with in- 
 calculable millions of the granules. 
 
 The examination of a transparent slice gives a 
 
I ON A PIECE OF CHALK. 7 
 
 good notion of the manner in which the com- 
 ponents of the chalk are arranged, and of their 
 relative proportions. But, by rubbing up some 
 chalk with a brush in water and then pouring o£E 
 the milky fluid, so as to obtain sediments of dif- 
 ferent degrees of fineness, the granules and the 
 minute rounded bodies may be pretty well sepa- 
 rated from one another, and submitted to micro- 
 scopic examination, either as opaque or as trans- 
 parent objects. By combining the views obtained 
 in these various methods, each of the rounded 
 bodies may be proved to be a beautifully-con- 
 structed calcareous fabric, made up of a number of 
 chambers, communicating freely with one an- 
 other. The chambered bodies are of various 
 "forms. One of the commonest is something like 
 a badly-grown raspberry, being formed of a num- 
 ber of nearly globular chambers of different sizes 
 congregated together. It is called Globigerina, 
 and some specimens of chalk consist of little else 
 than Globigerince and granules. Let us fix our at- 
 tention upon the Globigerina. It is the spoor of 
 the game we are tracking. If we can learn what 
 it is and what are the conditions of its existence, 
 we shall see our way to the origin and past history 
 of the chalk. 
 
 A suggestion which may naturally enough pre- 
 sent itself is, that these curious bodies are the 
 result of some process .of aggregation which has 
 taken place in the carbonate of lime; that, just 
 
8 ON A PIECE OP CHALK. i 
 
 as in winter, the rime on our windows simulates 
 the most delicate and elegantly arborescent foliage 
 — proving that the mere mineral water may, under 
 certain conditions, assume the outward form of 
 organic bodies — so this mineral substance, carbon- 
 ate of lime, hidden away in the bowels of the earth, 
 has taken the shape of these chambered bodies. 
 I am not raising a merely fanciful and unreal ob- 
 jection. Very learned men, in former days, have 
 even entertained the notion that all the formed 
 things found in rocks are of this nature; and if 
 no such conception is at present held to be admis- 
 sible, it is because long and varied experience has 
 now shown that mineral matter never does assume 
 the form and structure we find in fossils. If any 
 one were to try to persuade you that an oyster- 
 shell (which is also chiefly composed of carbonate 
 of lime) had crystallized out of sea-water, I sup- 
 pose you would laugh at the absurdity. Your 
 laughter would be justified by the fact that all 
 experience tends to show that oyster-shells are 
 formed by the agency of oysters, and in no other 
 way. And if there were no better reasons, we 
 should be justified, on like grounds, in believing 
 that Glohigerina is not the product of anything but 
 vital activity. 
 
 Happily, however, better evidence in proof of 
 the organic nature of the Olohigerince than that 
 of analogy is forthcoming. It so happens that 
 calcareous skeletons, exactly similar to the 
 
I ON A PIECE OP CHALK. 9 
 
 GloUgerincB of the chalk, are being formed, at 
 the present moment, by minute living creatures, 
 which flourish in multitudes, literally more nu- 
 merous than the sands of the sea-shore, over a 
 large extent of that part of the earth's surface 
 which is covered by the ocean. 
 
 The history of the discovery of these living 
 Glohigerinw, and of the part which they play in 
 rock building, is singular enough. It is a dis- 
 covery which, like others of no less scientific im- 
 portance, has arisen, incidentally, out of work 
 devoted to very different and exceedingly practical 
 interests. When men first took to the sea, they 
 speedily learned to look out for shoals and rocks; 
 and the more the burthen of their ships increased, 
 the more imperatively necessary it became for 
 sailors to ascertain with precision the depth of 
 the waters they traversed. Out of this necessity 
 grew the use of the lead and sounding line; and, 
 ultimately, marine-surveying, which is the re- 
 cording of the form of coasts and of the depth 
 of the sea, as ascertained by the sounding-lead, 
 upon charts. 
 
 At the same time, it became desirable to ascer- 
 tain and to indicate the nature of the sea-bottom, 
 since this circumstance greatly affects its goodness 
 as holding ground for anchors. Some ingenious 
 tar, whose name deserves a better fate than the 
 oblivion into which it has fallen, attained this 
 object by " arming " the bottom of the lead with 
 
10 ON A PIECE OP CHALK. i 
 
 a lump of grease, to which more or less of the 
 sand or mud, or broken shells, as the case might 
 be, adhered, and was brought to the surface. But, 
 however well adapted such an apparatus might be 
 for rough nautical purposes, scientific accuracy 
 could not be expected from the armed lead, and 
 to remedy its defects (especially when applied to 
 sounding in great depths) Lieut. Brooke, of the 
 American Navy, some years ago invented a most 
 ingenious machine, by which a considerable por- 
 tion of the superficial layer of the sea-bottom can 
 be scooped out and brought up from any depth to 
 which the lead descends. In 1853, Lieut. Brooke 
 obtained mud from the bottom of the North At- 
 lantic, between Newfoundland and the Azores, at 
 a depth of more than 10,000 feet, or two miles, 
 by the help of this sounding apparatus. The 
 specimens were sent for examination to Ehrenberg 
 of Berlin, and to Bailey of West Point, and those 
 able microscopists found that this deep-sea mud 
 was almost entirely composed of the skeletons of 
 living organisms — the greater proportion of these 
 being just like the GloUgerincB already known to 
 occur in the chalk. 
 
 Thus far, the work had been carried on simply 
 in the interests of science, but Lieut. Brooke's 
 method of sounding acquired a high -commercial 
 value, when the enterprise of laying down the 
 telegraph-cable between this country and the 
 United States was undertaken. For it became a 
 
I ON A PIECE OP CHALK. H 
 
 matter of immense importance to know, not only 
 the depth of the sea over the whole line along 
 which the cable was to be laid, but the exact 
 nature of the bottom, so as to guard against 
 chances of cutting or fraying the strands of that 
 costly rope. The Admiralty consequently ordered 
 Captain Dayman, an old friend and shipmate of 
 mine, to ascertain the depth over the whole line 
 of the cable, and to bring back specimens of the 
 bottom. In former days, such a command as this 
 might have sounded very much like one of the 
 impossible things which the young Prince in the 
 Fairy Tales is ordered to do before he can obtain 
 the hand of the Princess. However, in the months 
 of June and July, 1857, my friend performed the 
 task assigned to him with great expedition and 
 precision, without, so far as I know, having met 
 with any reward of that kind. The specimens of 
 Atlantic mud which he procured were sent to me 
 to be examined and reported upon.* 
 
 The result of all these operations is, that we 
 know the contours and the nature of the surface- 
 soil covered by the North Atlantic for a distance 
 of 1,700 miles from east to west, as well as we 
 
 * See Appendix to Captain Dayman's Deep-sea Sound- 
 ings in the North Atlantic Ocean between Ireland and 
 Newfoundland, made in B.M.8. " Cyclops." Published 
 by order of the Lords Commissioners of the Admiralty, 
 1858. They have since formed the subject of an elabo- 
 rate Memoir by Messrs. Parker and Jones, published in 
 the Philosophical Transactions for 1865. 
 
12 ON A PIECE OP CHALK. i 
 
 know that of any part of the dry land. It is a pro- 
 digious plain — one of the widest and most even 
 plains in the world. If the sea were drained ofE, 
 you might drive a waggon all the way from Va- 
 lentia, on the west coast of Ireland, to Trinity Bay, 
 in Newfoundland. And, except upon one sharp 
 incline about 300 miles from Valentia, I am not 
 quite sure that it would even be necessary to put 
 the skid on, so gentle are the ascents and descents 
 upon that long route. From Valentia the road 
 would lie down-hill for about 200 miles to the 
 point at which the bottom is now covered by 1,700 
 fathoms of sea-water. Then would come the cen- 
 tral plain, more than a thousand miles wide, the 
 inequalities of the surface of which would be hard- 
 ly perceptible, though the depth of water upon it 
 now varies from 10,000 to 15,000 feet; and there 
 are places in which Mont Blanc might be sunk 
 without showing its peak above water. Beyond 
 this, the ascent on the American side commences, 
 and gradually leads, for about 300 miles, to the 
 Newfoundland shore. 
 
 Almost the whole of the bottom of this central 
 plain (which extends for many hundred miles in a 
 north and south direction) is covered by a fine 
 mud, which, when brought to the surface, dries 
 into a greyish white friable substance. You can 
 write with this on a blackboard, if you are so in- 
 clined; and, to the eye, it is quite like very soft, 
 greyish chalk. Examined chemically, it proves to 
 
I ON A PIECE OP CHALK. 13 
 
 be composed almost wholly of carbonate of lime; 
 and if you make a section of it, in the same way 
 as that of the piece of chalk was made, and view 
 it with the microscope, it presents innumerable 
 Globigerinw embedded in a granular matrix. Thus 
 this deep-sea mud is substantially chalk. I say 
 substantially, because there are a good many 
 minor differences; but as these have no bearing on 
 the question immediately before us, — which is the 
 nature of the Glohigerince of the chalk, — ^it is un- 
 necessary to speak of them. 
 
 Glohigerince of every size, from the smallest to 
 the largest, are associated together in the Atlantic 
 mud, and the chambers of many are filled by a soft 
 animal matter. This soft substance is, in fact, the 
 remains of the creature to which the Gldbigerina 
 shell, or rather skeleton, owes its existence — and 
 which is an animal of the simplest imaginable de- 
 scription. It is, in fact, a mere particle of living 
 jelly, without defined parts of any kind — without 
 a mouth, nerves, muscles, or distinct organs, and 
 only manifesting its vitality to ordinary observa- 
 tion by thrusting out and retracting from all parts 
 of its surface, long filamentous processes, which 
 serve for arms and legs. Yet this amorphous par- 
 ticle, devoid of everything which, in the higher 
 animals, we call organs, is capable of feeding, 
 growing, and multiplying; of separating from the 
 ocean the small proportion of carbonate of lime 
 which is dissolved in sea- water; and of building up 
 
14 ON A PIECE OP CHALK. i 
 
 that substance into a skeleton for itself, according 
 to a pattern which can be imitated by no other 
 known agency. 
 
 The notion that animals can live and flourish 
 in the sea, at the vast depths from which apparent- 
 ly living GldbigerincB have been brought up, does 
 not agree very well with our usual conceptions re- 
 specting the conditions of animal life; and it is 
 not so absolutely impossible as it might at first 
 sight appear to be, that the Glohigerinm of the At- 
 lantic sea-bottom do not live and die where they 
 are found. 
 
 As I have mentioned, the soundings from the 
 great Atlantic plain are almost entirely made up 
 of GloMgerince, with the granules which have been 
 mentioned, and some few other calcareous shells; 
 but a small percentage of the chalky mud — per- 
 haps at most some five per cent, of it — is of a 
 different nature, and consists of shells and skele- 
 tons composed of silex, or pure flint. These sili- 
 eious bodies belong partly to the lowly vegetable 
 organisms which are called Diatomacece, and partly 
 to the minute, and extremely simple, animals, 
 termed Radiolaria. It is quite certain that these 
 creatures do not live at the bottom of the ocean, 
 but at its surface — where they may be obtained 
 in prodigious numbers by the use of a properly 
 constructed net. Hence it follows that these sili- 
 cious organisms, though they are not heavier than 
 the lightest dust, must have fallen, in some cases, 
 
I ON A PIECE OP CHALK. 15 
 
 through fifteen thousand feet of water, before 
 they reached their final resting-place on the 
 ocean floor. And considering how large a 
 surface these bodies expose in proportion to 
 their weight, it is probable that they occupy a 
 great length of time in making their burial Jour- 
 ney from the surface of the Atlantic to the 
 bottom. 
 
 But if the Eadiolaria and Diatoms are thus 
 rained upon the bottom of the sea, from the super- 
 ficial layer of its waters in which they pass their 
 lives, it is obviously possible that the GlohigerincB 
 may be similarly derived; and if they were so, 
 it would be much more easy to understand how 
 they obtain their supply of food than it is at pres- 
 ent. Nevertheless, the positive and negative evi- 
 dence all points the other way. The skeletons 
 of the full-grown, deep-sea Gldbigerinm are so 
 remarkably solid and heavy in proportion to their 
 surface as to seem little fitted for floating; and, 
 as a matter of fact, they are not to be found along 
 with the Diatoms and Radiolaria in the uppermost 
 stratum of the open ocean. It has been ob- 
 served, again, that the abundance of Gldbigerince, 
 in proportion to other organisms, of like kind, in- 
 creases with the depth of the sea; and that deep- 
 water Glohigerinw are larger than those which live 
 in shallower parts of the sea; and such facts nega- 
 tive the supposition that these organisms have 
 been swept by currents from the shallows into the 
 
16 ON A PIECE OP CHALK. i 
 
 deeps of the Atlantic. It therefore seems to 
 be hardly doubtful that these wonderful crea- 
 tures live and die at the depths in which they are 
 found.* 
 
 However, the important points for us are, that 
 the living GldbigerincB are exclusively marine ani- 
 mals, the skeletons of which abound at the bot- 
 tom of deep seas; and that there is not a shadow 
 of reason for believing that the habits of the 
 Globigerince of the chalk differed from those of 
 the existing species. Butsif this be true, there 
 is no escaping the conclusion that the chalk itself 
 is the dried mud of an ancient deep sea. 
 
 In working over the soundings collected by 
 Captain Dayman, I was surprised to find that 
 many of what I have called the " granules " of 
 that mud were not, as one might have been tempt- 
 ed to think at first, the mere powder and waste of 
 Globigerince, but that they had a definite form and 
 size. I termed these bodies " coccoliths" and 
 
 * During the cruise of H.M.S. Bulldog, commanded by 
 Sir Leopold M'Clintock, in 1860, living star-fish were 
 brought up, clinging to the lowest part of the sounding- 
 line, from a depth of 1,260 fathoms, midway between 
 Cape Farewell, in Greenland, and the Eockall banks. 
 Dr. Wallich ascertained that the sea-bottom at this point 
 consisted of the ordinary Globigerina ooze, and that the 
 stomachs of the star-fishes were full of Globigerince. This 
 discovery removes all objections to the existence of living 
 Globigerinw at great depths, which are based upon the 
 supposed difficulty of maintaining animal life under such 
 conditions ; and it throws the burden of proof upon those 
 who object to the supposition that the Globigerinw live 
 and die where they are found. 
 
I ON A PIECE OF CHALK. 17 
 
 doubted their organic nature. Dr. Wallich veri- 
 fied my observation, and added the interesting dis- 
 covery that, not unfrequently, bodies similar to 
 these " coccoliths " were aggregated together into 
 spheroids, which he termed " coccospheres." So far 
 as we knew, these bodies, the nature of which 
 is extremely puzzling and problematical, were 
 peculiar to the Atlantic soundings. But, a few 
 years ago, Mr. Sorby, in making a careful examina- 
 tion of the chalk by means of thin sections and 
 otherwise, observed, as Ehrenberg had done before 
 him, that much of its granular basis possesses a 
 definite form. Comparing these formed particles 
 with those in the Atlantic soundings, he found 
 the two to be identical; and thus proved that the 
 chalk, like the surroundings, contains these mys- 
 terious coccoliths and coccospheres. Here was a 
 further and most interesting confirmation, from 
 internal evidence, of the essential identity of the 
 chalk with modern deep-sea mud. Globigerinw, 
 coccoliths, and coccospheres are found as the chief 
 constituents of both, and testify to the general 
 similarity of the conditions under which both have 
 been formed.* 
 
 The evidence furnished by the hewing, facing, 
 
 * I have recently traced out the development of the 
 " coccoliths " from a diameter of TaWtli of an inch up to 
 their largest size (which is about -rAuth), and no longer 
 doubt that they are produced by independent organisms, 
 which, like the Globigerinw, live and die at the bottom 
 of the sea. 
 
 188 
 
18 ON A PIECE OP CHALK. i 
 
 and superposition of the stones of the Pyramids, 
 that these structures were built by men, has no 
 greater weight than the evidence that the chalk 
 was built by Olobigerinw; and the belief that 
 those ancient pyramid-builders were terrestrial 
 and air-breathing creatures like ourselves, is not 
 better based than the conviction that the chalk- 
 makers lived in the sea. But as our belief in the 
 building of the Pyramids by men is not only 
 grounded on the internal evidence afEorded by 
 these structures, but gathers strength from multi- 
 tudinous collateral proofs, and is clinched by the 
 total absence of any reason for a contrary belief; 
 so the evidence drawn from the Glohigerince that 
 the chalk is an ancient sea-bottom, is fortified by 
 innumerable independent lines of evidence; and 
 our belief in the truth of the conclusion to which 
 all positive testimony tends, receives the like nega- 
 tive justification from the fact that no other hy- 
 pothesis has a shadow of foundation. 
 
 It may be worth while briefly to consider a few 
 of these collateral proofs that the chalk was de- 
 posited at the bottom of the sea. The great mass 
 of the chalk is composed, as we have seen, of 
 the skeletons of Glohigerince, and other simple or- 
 ganisms, imbedded in granular matter. Here and 
 there, however, this hardened mud of the ancient 
 sea reveals the remains of higher animals which 
 have lived and died, and left their hard parts in 
 the mud, just as the oysters die and leave their 
 
I ON A PIECE OP CHALK. 19 
 
 shells behind them, in the mud of the pres- 
 ent seas. 
 
 There are, at the present day, certain groups of 
 animals which are never found in fresh waters, 
 being unable to live anywhere but in the sea. 
 Such are the corals; those corallines which are 
 called Polyzoa; those creatures which fabricate 
 the lamp-shells, and are called Brachiopoda; the 
 pearly Nautilus, and all animals allied to it; and 
 all the forms of sea-urchins and star-fishes. Not 
 only are all these creatures confined to salt water 
 at the present day; but, so far as our records of 
 the past go, the conditions of their existence have 
 been the same: hence, their occurrence in any 
 deposit is as strong evidence as can be obtained, 
 that that deposit was formed in the sea. Now 
 the remains of animals of all kinds which have 
 been enumerated, occur in the chalk, in greater or 
 less abundance; while not one of those forms of 
 shell-fish which are characteristic of fresh water 
 has yet been observed in it. 
 
 When we consider that the remains of more 
 than three thousand distinct species of aquatic 
 animals have been discovered among the fossils of 
 the chalk, that the great majority of them are of 
 such forms as are now met with only in the sea, 
 and that there is no reason to believe that any 
 one of them inhabited fresh water — the collateral 
 evidence that the chalk represents an ancient sea- 
 bottom acquires as great force as the proof de- 
 
20 ON A PIECE OP CHALK. i 
 
 rived from the nature of the chalk itself. I think 
 you will now allow that I did not overstate my 
 case when I asserted that we have as strong 
 grounds for believing that all the vast area of 
 dry land, at present occupied by the chalk, was 
 once at the bottom of the sea, as we have for any 
 matter of history whatever; while there is no 
 Justification for any other belief. 
 
 No less certain it is that the time during which 
 the countries we now call south-east England, 
 France, Germany, Poland, Eussia, Egypt, Arabia, 
 Syria, were more or less completely covered by a 
 deep sea, was of considerable duration. We have 
 already seen that the chalk is, in places, more 
 than a thousand feet thick. I think you will 
 agree with me, that it must have taken some 
 time for the skeletons of animalcules of a hun- 
 dredth of an inch in diameter to heap up such 
 a mass as that. I have said that throughout the 
 thickness of the chalk the remains of other ani- 
 mals are scattered. These remains are often in 
 the most exquisite state of preservation. The 
 valves of the shell-fishes are commonly adherent; 
 the long spines of some of the sea-urchins, which 
 would be detached by the smallest Jar, often re- 
 main in their places. In a word, it is certain 
 that these animals have lived and died when the 
 place which they now occupy was the surface of 
 as much of the chalk as had then been deposited; 
 and that each has been covered up by the layer of 
 
1 ON A PIECE OP CHALK. 21 
 
 GloUgerina mud, upon which the creatures im- 
 bedded a little higher up have, in like manner, 
 lived and died. But some of these remains prove 
 the existence of reptiles of vast size in the 
 chalk sea. These lived their time, and had 
 their ancestors and descendants, which as- 
 suredly implies time, reptiles being of slow 
 growth. 
 
 There is more curious evidence, again, that the 
 process of covering up, or, in other words, the 
 deposit of GloUgerina skeletons, did not go on 
 very fast. It is demonstrable that an animal of the 
 cretaceous sea might die, that its skeleton might 
 lie uncovered upon the sea-bottom long enough 
 to lose all its outward coverings and appendages 
 by putrefaction; and that, after this had hap- 
 pened, another animal might attach itself to the 
 dead and naked skeleton, might grow to maturity, 
 and might itself die before the calcareous mud had 
 buried the whole. 
 
 Cases of this kind are admirably described by 
 Sir Charles Lyell. He speaks of the frequency 
 with which geologists find in the chalk a fossilized 
 sea-urchin, to which is attached the lower valve of 
 a Crania. This is a kind of shell-fish, with a 
 shell composed of two pieces, of which, as in the 
 oyster, one is fixed and the other free. 
 
 " The upper valve is almost invariably want- 
 ing, though occasionally found in a perfect state of 
 preservation in the white chalk at some distance. 
 
22 ON A PIECE OF CHALK. I 
 
 In this case, we see clearly that the sea-urchin 
 first lived from youth to age, then died and lost 
 its spines, which were carried away. Then the 
 young Crania adhered to the bared shell, grew 
 and perished in its turn; after which, the upper 
 valve was separated from the lower, before the 
 Echinus became enveloped in chalky mud."* 
 
 A specimen in the Museum of Practical Geol- 
 ogy, in London, still further prolongs the period 
 which must have elapsed between the death of 
 the sea-urchin, and its burial by the GloMgerince. 
 Por the outward face of the valve of a Crania, 
 which is attached to a sea-urchin, (Micraster), is 
 itself overrun by an incrusting coralline, which 
 spreads thence over more or less of the surface 
 of the sea-urchin. It follows that, after the 
 upper valve of the Crania fell off, the surface 
 of the attached valve must have remained exposed 
 long enough to allow of the growth of the whole 
 coralline, since corallines do not live embedded 
 in mud.* 
 
 The progress of knowledge may, one day, en- 
 able us to deduce from such facts as these the 
 maximum rate at which the chalk can have ac- 
 cumulated, and thus to arrive at the minimum 
 duration of the chalk period. Suppose that the 
 valve of the Crania upon which a coralline has 
 fixed itself in the way just described, is so at- 
 
 * Elements of Geology, by Sir Charles Lyell, Bart., 
 F.R.S., p. 23. 
 
I ON A PIECE OP CHALK. 23 
 
 tached to the sea-urchin that no part of it is more 
 than an inch above the face upon which the sea- 
 urchin rests. Then, as the coralline could not 
 have fixed itself, if the Crania had been covered 
 up with chalk mud, and could not have lived had 
 itself been so covered, it follows, that an inch of 
 chalk mud could not have accumulated within the 
 time between the death and decay of the soft parts 
 of the sea-urchin and the growth of thp coralline 
 to the full size which it has attained. If the de- 
 cay of the soft parts of the sea-urchin; the attach- 
 ment, growth to maturity, and decay of the 
 Crania; and the subsequent attachment and 
 growth of the coralline, took a year (which is a low 
 estimate enough), the accumulation of the inch of 
 chalk must have taken more than a year: and the 
 deposit of a thousand feet of chalk must, conse- 
 quently, have taken more than twelve thousand 
 years. 
 
 The foundation of all this calculation is, of 
 course, a knowledge of the length of time the 
 Crania and the coralline needed to attain their 
 full size; and, on this head, precise knowledge is 
 at present wanting. But there are circumstances 
 which tend to show, that nothing like an inch of 
 chalk has accumulated during the life of a Crania; 
 and, on any probable estimate of the length of 
 that life, the chalk period must have had a much 
 longer duration than that thus roughly assigned 
 to it. 
 
24 ON A PIECE OP CHALK. i 
 
 Thus, not only is it certain that the chalk 
 is the mud of an ancient sea-bottom; but it is no 
 less certain, that the chalk sea existed during an 
 extremely long period, though we may not be 
 prepared to give a precise estimate of the length 
 of that period in years. The relative duration is 
 clear, though the absolute duration may not be 
 definable. The attempt to affix any precise date 
 to the period at which the chalk sea began, or 
 ended, its existence, is baffled by difficulties of 
 the same kind. But the relative age of the cre- 
 taceous epoch may be determined with as great 
 ease and certainty as the long duration of that 
 epoch. 
 
 You will have heard of the interesting dis- 
 coveries recently made, in various parts of Western 
 Europe, of flint implements, obviously worked into 
 shape by human hands, under circumstances which 
 show conclusively that man is a very ancient deni- 
 zen of these regions. It has been proved that the 
 whole populations of Europe, whose existence has 
 been revealed to us in this way, consisted of sav- 
 ages, such as the Esquimaux are now; that, in 
 the country which is now France, they hunted the 
 reindeer, and were familiar with the ways of the 
 mammoth and the bison. The physical geography 
 of France was in those days different from what it 
 is now — the river Somme, for instance, having cut 
 its bed a hundred feet deeper between that time 
 and this; and, it is probable, that the climate was 
 
I ON A PIECE OP CHALK. 25 
 
 more like that of Canada or Siberia, than that of 
 Western Europe. 
 
 The existence of these people is forgotten even 
 in the traditions of the oldest historical nations. 
 The name and fame of them had utterly vanished 
 until a few years back; and the amount of physical 
 change vi^hich has been effected since their day 
 renders it more than probable that, venerable as 
 are some of the historical nations, the workers of 
 the chipped flints of Hoxne or of Amiens are to 
 them, as they are to us, in point of antiquity. 
 But, if we assign to these hoar relics of long-van- 
 ished generations of men the greatest age that can 
 possibly be claimed for them, they are not older 
 than the drift, or boulder clay, which, in com- 
 parison with the chalk, is but a very juvenile 
 deposit. You need go no further than your own 
 sea-board for evidence of this fact. At one of the 
 most charming spots on the coast of Norfolk, 
 Cromer, you will see the boulder clay forming a 
 vast mass, which lies upon the chalk, and must 
 consequently have come into existence after it. 
 Huge boulders of chalk are, in fact, included in 
 the clay, and have evidently been brought to the 
 position they now occupy by the same agency as 
 that which has planted blocks of syenite from Nor- 
 way side by side with them. 
 
 The chalk, then, is certainly older than the 
 boulder clay. If you ask how much, I will again 
 take you no further than the same spot upon your 
 
26 ON A PIECE OF CHALK. i 
 
 own coasts for evidence. I have spoken of the 
 boulder clay and drift as resting upon the chalk. 
 That is not strictly true. Interposed between the 
 chalk and the drift is a comparatively insignifi- 
 cant layer, containing vegetable matter. But that 
 layer tells a wonderful history. It is full of 
 stumps of trees standing as they grew. Fir-trees 
 are there with their cones, and hazel-bushes with 
 their nuts; there stand the stools of oak and yew 
 trees, beeches and alders. Hence this stratum is 
 appropriately called the " forest-bed." 
 
 It is obvious that the chalk must have been 
 upheaved and converted into dry land, before the 
 timber trees could grow upon it. As the bolls of 
 some of these trees are from two to three feet in 
 diameter, it is no less clear that the dry land thus 
 formed remained in the same condition for long 
 ages. And not only do the remains of stately 
 oaks and well-grown firs testify to the duration of 
 this condition of things, but additional evidence to 
 the same effect is afforded by the abundant re- 
 mains of elephants, rhinoceroses, hippopotamuses, 
 and other great wild beasts, which it has yielded 
 to the zealous search of such men as the Eev. Mr. 
 Gunn. When you look at such a collection as he 
 has formed, and bethink you that these elephan- 
 tine bones did veritably carry their owners about, 
 and these great grinders crunch, in the dark woods 
 of which the forest-bed is now the only trace, it is 
 impossible not to feel that they are as good evi- 
 
I ON A PIECE OF CHALK. 27 
 
 dence of the lapse of time as the annual rings of 
 the tree stumps. 
 
 Thus there is a writing upon the wall of cliffs 
 at Cromer, and whoso runs may read it. It tells 
 us, with an authority which cannot be impeached, 
 that the ancient sea-bed of the chalk sea was 
 raised up, and remained dry land, until it was 
 covered with forest, stocked with the great game 
 the spoils of which have rejoiced your geologists. 
 How long it remained in that condition cannot be 
 said; but " the whirligig of time brought its re- 
 venges " in those days as in these. That dry land, 
 with the bones and teeth of generations of long- 
 lived elephants, hidden away among the gnarled 
 roots and dry leaves of its ancient trees, sank 
 gradually to the bottom of the icy sea, which cov- 
 ered it with huge masses of drift and boulder clay. 
 Sea-beasts, such as the walrus, now restricted to 
 the extreme north, paddled about where birds had 
 twittered among the topmost twigs of the fir-trees. 
 How long this state of things endured we know 
 not, but at length it came to an end. The up- 
 heaved glacial mud hardened into the soil of mod- 
 ern ISTorfolk. Forests grew once more, the wolf 
 and the beaver replaced the reindeer and the ele- 
 phant; and at length what we call the history of 
 England dawned. 
 
 Thus you have, within the limits of your own 
 county, proof that the chalk can Justly claim a 
 very much greater antiquity than even the oldest 
 
28 ON A PIECE OP CHALK. I 
 
 physical traces of mankind. But we may go fur- 
 ther and demonstrate, by evidence of the same 
 authority as that which testifies to the existence 
 of the father of men, that the chalk is vastly older 
 than Adam himself. The Book of Genesis in- 
 forms us that Adam, immediately upon his crea- 
 tion, and before the appearance of Eve, was placed 
 in the Garden of Eden. The problem of the geo- 
 graphical position of Eden has greatly vexed the 
 spirits of the learned in such matters, but there is 
 one point respecting which, so far as I know, no 
 commentator has ever raised a doubt. This is, 
 that of the four rivers which are said to run out of 
 it, Euphrates and Hiddekel are identical with the 
 rivers now known by the names of Euphrates and 
 Tigris. But the whole country in which these 
 mighty rivers take their origin, and through which 
 they run, is composed of rocks which are either 
 of the same age as the chalk, or of later date. So 
 that the chalk must not only have been formed, 
 but, after its formation, the time required for 
 the deposit of these later rocks, and for their up- 
 heaval into dry land, must have elapsed, before 
 the smallest brook which feeds the swift stream 
 of "the great river, the river of Babylon," began 
 to flow. 
 
 Thus, evidence which cannot be rebutted, and 
 which need not be strengthened, though if time 
 permitted I might indefinitely increase its quan- 
 
I ON A PIECE OP CHALK. 29 
 
 tity, compels you to believe that the earth, from 
 the time of the chalk to the present day, has been 
 the theatre of a series of changes as vast in their 
 amount, as they were slow in their progress. The 
 area on which we stand has been first sea and 
 then land, for at least four alternations; and has 
 remained in each of these conditions for a period 
 of great length. 
 
 Nor have these wonderful metamorphoses of 
 sea into land, and of land into sea, been confined 
 to one corner of England. During the chalk 
 period, or " cretaceous epoch," not one of the 
 present great physical features of the globe was in 
 existence. Our great mountain ranges, Pyrenees, 
 Alps, Himalayas, Andes, have all been upheaved 
 since the chalk was deposited, and the cretaceous 
 sea flowed over the sites of Sinai and Ararat. All 
 this is certain, because rocks of cretaceous, or still 
 later, date have shared in the elevatory movements 
 which gave rise to these mountain chains; and 
 may be found perched up, in some cases, many 
 thousand feet high upon their flanks. And evi- 
 dence of equal cogency demonstrates that, though, 
 in Norfolk, the forest-bed rests directly upon the 
 chalk, yet it does so, not because the period at 
 which the forest grew immediately followed that 
 at which the chalk was formed, but because an 
 immense lapse of time, represented elsewhere by 
 thousands of feet of rock, is not indicated at Cromer. 
 
 I must ask you to .believe that there is no less 
 
30 ON A PIECE OF CHALK. i 
 
 conclusive proof that a still more prolonged suc- 
 cession of similar changes occurred, before the 
 chalk was deposited. Nor have we any reason to 
 think that the first term in the series of these 
 changes is known. The oldest sea-beds preserved 
 to us are sands, and mud, and pebbles, the wear 
 and tear of rocks which were formed in still older 
 oceans. 
 
 But, great as is the magnitude of these physical 
 changes of the world, they have been accompanied 
 by a no less striking series of modifications in its 
 living inhabitants. All the great classes of ani- 
 mals, beasts of the field, fowls of the air, creep- 
 ing things, and things which dwell in the waters, 
 flourished upon the globe long ages before the 
 chalk was deposited. Very few, however, if any, 
 of these ancient forms of animal life were identi- 
 cal with those which now live. Certainly not one 
 of the higher animals was of the same species as 
 any of those now in existence. The beasts of 
 the field, in the days before the chalk, were not 
 our beasts of the field, nor the fowls of the air 
 such as those which the eye of men has seen flying, 
 unless his antiquity dates infinitely further back 
 than we at present surmise. If we could be car- 
 ried back into those times, we should be as one 
 suddenly set down in Australia before it was col- 
 onized. We should see mammals, birds, reptiles, 
 fishes, insects, snails, and the like, clearly recog- 
 nizable as such, and yet not one of them would 
 
I ON A PIECE OF CHALK. 31 
 
 be just the same as those with which we are 
 familiar, and many would be extremely dif- 
 ferent. 
 
 • From that time to the present, the population 
 of the world has undergone slow and gradual, but 
 incessant, changes. There has been no grand 
 catastrophe — no destroyer has swept away the 
 forms of life of one period, and replaced them by 
 a totally new creation: but one species has van- 
 ished and another has taken its place; creatures of 
 one type of structure have diminished, those of 
 another have increased, as time has passed on. 
 And thus, while the differences between the living 
 creatures of the time before the chalk and those 
 of the present day appear startling, if placed side 
 by side, we are led from one to the other by 
 the most gradual progress, if we follow the course 
 of Nature through the whole series of those 
 relics of her operations which she has left behind. 
 It is by the population of the chalk sea that the 
 ancient and the modern inhabitants of the world 
 are most completely connected. The groups 
 which are dying out flourish, side by side, with 
 the groups which are now the dominant forms of 
 life. Thus the chalk contains remains of those 
 strange flying and swimming reptiles, the ptero- 
 dactyl, the ichthyosaurus, and the plesiosaurus, 
 which are found in no later deposits, but abounded 
 in preceding ages. The chambered shells called 
 ammonites and belemnites, which are so charac- 
 
32 ON A PIECE OP CHALK. i 
 
 teristie of the period preceding the cretaceous, in 
 like manner die with it. 
 
 But, amongst these fading remainders of a pre- 
 vious state of things, are some very modern forms 
 of life, looking like Yankee pedlars among a tribe 
 of Eed Indians. Crocodiles of modern type ap- 
 pear; bony fishes, many of them very similar to 
 existing species, almost supplant the forms of 
 fish which predominate in more ancient seas; and 
 many kinds of living shell-fish first become known 
 to us in the chalk. The vegetation acquires a 
 modern aspect. A few living animals are not 
 even distinguishable as species, from those 
 which existed at that remote epoch. The Globi- 
 gerina of the present day, for example, is not 
 different specifically from that of the chalk; and 
 the same may be said of many other Foraminifera. 
 I think it probable that critical and unprejudiced 
 examination will show that more than one species 
 of much higher animals have had a similar lon- 
 gevity; but the only example which I can at pres- 
 ent give confidently is the snake's-head lamp-shell 
 {TerebratuKna caput serpentis), which lives in our 
 English seas and abounded (as TerebratuKna stri- 
 ata of authors) in the chalk. 
 
 The longest line of human ancestry must hide 
 its diminished head before the pedigree of this 
 insignificant shell-fish. We Englishmen are 
 proud to have an ancestor who was present at the 
 Battle of Hastings. The ancestors of Terebratu- 
 
I ON A PIECE OF CHALK. 33 
 
 Una caput serpentis may have been present at a 
 battle of Ichthyosauria in that part of the sea 
 which, when the chalk was forming, flowed over the 
 Site of Hastings. When all around has changed, 
 this Terebratulina has peacefully propagated its 
 species from generation to generation, and stands 
 to this day, as a living testimony to the continuity 
 of the present with the past history of the globe. 
 
 Up to this moment I have stated, so far as I 
 know, nothing but well-authenticated facts, and 
 the immediate conclusions which they force upon 
 the mind. But the mind is so constituted that it 
 does not willingly rest in facts and immediate 
 causes, but seeks always after a knowledge of the 
 remoter links in the chain of causation. 
 
 Taking the many changes of any given spot of 
 the earth's surface, from sea to land and from land 
 to sea, as an established fact, we cannot refrain 
 from asking ourselves how these changes have 
 occurred. And when we have explained them — 
 as they must be explained — by the alternate. slow 
 movements of elevation and depression which 
 have affected the crust of the earth, we go still 
 further back, and ask, Why these movements? 
 
 I am not certain that any one can give you a 
 satisfactory answer to that question. Assuredly I 
 cannot. All that can be said, for certain, is, that 
 such movements are part of the ordinary course of 
 nature, inasmuch as they are going on at the pres- 
 189 
 
34 ON A PIECE OP CHALK. i 
 
 ent time. Direct proof may be given, that some 
 parts of the land of the northern hemisphere are 
 at this moment insensibly rising and others in- 
 sensibly sinking; and there is indirect, but per- 
 fectly satisfactory, proof, that an enormous area 
 now covered by the Pacific has been deepened 
 thousands of feet, since the present inhabitants of 
 that sea came into existence. Thus there is not a 
 shadow of a reason for believing that the physical 
 changes of the globe, in past times, have been af- 
 fected by other than natural causes. Is there any 
 more reason for believing that the concomitant 
 modifications in the forms of the living inhabi- 
 tants of the globe have been brought about in 
 other ways? 
 
 Before attempting to answer this question, let 
 us try to form a distinct mental picture of what 
 has happened in some special case. The crocodiles 
 are animals which, as a group, have a very vast 
 antiquity. They abounded ages before the chalk 
 was deposited; they throng the rivers in warm 
 climates, at the present day. There is a difference 
 in the form of the joints of the back-bone, and in 
 some minor particulars, between the crocodiles of 
 the present epoch and those which lived before 
 the chalk; but, in the cretaceous epoch, as I have 
 already mentioned, the crocodiles had assumed 
 the modern type of structure. Notwithstanding 
 this, the crocodiles of the chalk are not identically 
 the same as those which lived in the times called 
 
I OJT A PIECE OF CHALK. 35 
 
 " older tertiary," which succeeded the cretaceous 
 epoch; and the crocodiles of the older tertiaries 
 are not identical with those of the newer tertia- 
 ries, nor are these identical with existing forms. 
 I leave open the question whether particular spe- 
 cies may have lived on from epoch to epoch. But 
 each epoch has had its peculiar crocodiles; though 
 all, since the chalk, have belonged to the modern 
 type, and differ simply in their proportions, and in 
 such structural particulars as are discernible only 
 to trained eyes. 
 
 How is the existence of this long succession of 
 different species of crocodiles to be accounted for? 
 Only two suppositions seem to be open to us — 
 Either each species of crocodile has been specially 
 created, or it has arisen out of some pre-existing 
 form by the operation of natural causes. Choose 
 your hypothesis; I have chosen mine. I can find 
 no warranty for believing in the distinct creation 
 of a score of successive species of crocodiles in the 
 course of countless ages of time. Science gives 
 no countenance to such a wild fancy; nor can even 
 the perverse ingenuity of a commentator pretend 
 to discover this sense, in the simple words in which 
 the writer of Genesis records the proceedings of 
 the fifth and sixth days of the Creation. 
 
 On the other hand, I see no good reason for 
 doubting the necessary alternative, that all these 
 varied species have been evolved from pre-exist- 
 ing crocodilian forms, by the operation of causes 
 
36 ON A PIECE OF CHALK. i 
 
 as completely a part of the common order of nature 
 as those which have effected the changes of the 
 inorganic world. Few will venture to affirm that 
 the reasoning which applies to crocodiles loses its 
 force among other animals, or among plants. If 
 one series of species has come into existence by 
 the operation of natural causes, it seems folly to 
 deny that all may have arisen in the same way. 
 
 A small beginning has led us to a great ending. 
 If I were to put the bit of chalk with which we 
 started into the hot but obscure flame of burning 
 hydrogen, it would presently shine like the sun. 
 It seems to me that this physical metamorphosis 
 is no false image of what has been the result of 
 our subjecting it to a jet of fervent, though nowise 
 brilliant, thought to-night. It has become lumi- 
 nous, and its clear rays, penetrating the abyss of 
 the remote past, have brought within our ken some 
 stages of the evolution of the earth. And in the 
 shifting " without haste, but without rest " of the 
 land and sea, as in the endless variation of the 
 forms assumed by living beings, we have ob- 
 served nothing but the natural product of the 
 forces originally possessed by the substance of the 
 universe. 
 
II. 
 
 THE PEOBLEMS OF THE DEEP SEA. 
 [1873.] 
 
 On the 21st of December, 1873, H.M.S. Chal- 
 lenger, an eighteen gun corvette, of 3,000 tons bur- 
 den, sailed from Portsmouth harbour for a three, 
 or perhaps four, years' cruise. 'No man-of-war 
 ever left that famous port before with so singular 
 an equipment. Two of the eighteen sixty-eight 
 pounders of the Challenger's armament remained 
 to enable her to speak with effect to sea-rovers, 
 haply devoid of any respect for science, in the re- 
 mote seas for which she is bound; but the main- 
 deck was, for the most part, stripped of its war-like 
 gear, and fitted up with physical, chemical, and 
 biological laboratories; photography had its dark 
 cabin; while apparatus for dredging, trawling, and 
 sounding; for photometers and for thermometers, 
 filled the space formerly occupied by guns and 
 gun-tackle, pistols and cutlasses. 
 
 The crew of the Challenger match her fittings. 
 Captain Nares, his officers and men, are ready to 
 look after the interests of hydrography, work the 
 
 37 
 
38 THE PROBLEMS OP THE DEEP SEA. ii 
 
 sliip, and, if need be, fight her as seamen should; 
 while there is a staff of scientific civilians, under 
 the general direction of Dr. Wyville Thomson, 
 F.E.S. (Professor of Natural History in Edin- 
 burgh University by rights, but at present de- 
 tached for duty in partibus), whose business it is 
 to turn all the wonderfully packed stores of appli- 
 ances to account, and to accumulate, before the 
 ship returns to England, such additions to natural 
 knowledge as shall justify the labour and cost in- 
 volved in the fitting out and maintenance of the 
 expedition. 
 
 Under the able and zealous superintendence of 
 the Hydrographer, Admiral Eichards, every pre- 
 caution which experience and forethought could 
 devise has been taken to provide the expedition 
 with the material conditions of success; and it 
 would seem as if nothing short of wreck or pesti- 
 lence, both most improbable contingencies, could 
 prevent the Challenger from doing splendid work, 
 and opening up a new era in the history of scien- 
 tific voyages. 
 
 The despatch of this expedition is the culmina- 
 tion of a series of such enterprises, gradually in- 
 creasing in magnitude and importance, which the 
 Admiralty, greatly to its credit, has carried out for 
 some years past; and the history of which is given 
 by Dr. "Wyville Thomson in the beautifully illus- 
 trated volume entitled " The Depths of the Sea," 
 published since his departure. 
 
II THE PROBLEMS OP THE DEEP SEA. 39 
 
 " In the spring of the year 1868, my friend Dr. W. B. 
 Carpenter, at that time one of the Vice-Presidents of the 
 Royal Society, was with me in Ireland, where we were 
 working out together the structure and development of 
 the Crinoids. I had long previously had a profound con- 
 viction that the land of promise for the naturalist, the 
 only remaining region where there were endless novelties 
 of extraordinary interest ready to the hand which had the 
 means of gathering them, was the bottom of the deep sea. 
 I had even had a glimpse of some of these treasures, for 
 I had seen, the year before, with Prof. Sars, the forms 
 which I have already mentioned dredged by his son at a 
 depth of 300 to 400 fathoms off the Loffoten Island's. I 
 propounded my views to my fellow-labourer, and we dis- 
 cussed the subject many timies over our microscopes. I 
 strongly urged Dr. Carpenter to use his influence at head- 
 quarters to induce the Admiralty, probably through the 
 Council of the Royal Society, to give us the use of a ves- 
 sel properly fitted with dredging gear and all necessary 
 scientific appartus, that many heavy questions as to the 
 state of things in the depths of the ocean, which were 
 still in a state of uncertainty, might be definitely settled. 
 After full consideration. Dr. Carpenter promised his 
 hearty co-operation, and we agreed that I should write 
 to him on his return to London, indicating generally the 
 results which I anticipated, and sketching out what I 
 conceived to be a promising line of inquiry. The Council 
 of the Royal Society warmly ■ supported the proposal; 
 and I give here in chronological order the short and emi- 
 nently satisfactory correspondence which led to the Ad- 
 miralty placing at the disposal of Dr. Carpenter and my- 
 self the gunboat Lightning, under the command of StalT- 
 Commander May, R.N., in the summer of 1868, for a 
 trial cruise to the North of Scotland, and afterwards to 
 the much wider surveys in H.M.S. Porcupine, Captain 
 Calver, R.N., which were made with the additional asso- 
 
40 THE PROBLEMS OP THE DEEP SEA. ii 
 
 ciation of Mr. Gwyn Jeffreys, in the summers of the 
 years 1869 and 1870." * 
 
 Plain men may be puzzled to understand why 
 Dr. Wyville Thomson, not being a critic, should 
 relegate the " Land of Promise " to the bottom of 
 the deep sea; they may still more wonder what 
 manner of " milk and honey " the Challenger ex- 
 pects to find; and their perplexity may well rise 
 to its maximum, when they seek to divine the man- 
 ner in which that milk and honey are to be got out 
 of so inaccessible a Canaan. I will, therefore, en- 
 deavour to give some answer to these questions in 
 an order the reverse of that in which I have stated 
 them. 
 
 Apart from hooks, and lines, and ordinary 
 nets, fishermen have, from time immemorial, made 
 use of two kinds of implements for getting at sea- 
 creatures which live beyond tide-marks — these are 
 the " dredge " and the " trawl." The dredge is 
 used by oyster-fishermen. Imagine a large bag, 
 the mouth of which has the shape of an elongated 
 parallelogram, and is fastened to an iron frame of 
 the same shape, the two long sides of this rim 
 being fashioned into scrapers. Chains attach the 
 ends of the frame to a stout rope, so that when the 
 bag is dragged along by the rope, the edge of one 
 of the scrapers rests on the ground, and scrapes 
 whatever it touches into the bag. The oyster- 
 
 * The Depths of the Sea, pp. 49-50. 
 
n THE PROBLEMS OF THE DEEP SEA. 41 
 
 dredger takes one of these machines in his boat, 
 and when he has reached the oyster-bed the dredge 
 is tossed overboard; as soon as it has sunk to the 
 bottom the rope is paid out sufficiently to prevent 
 it from pulling the dredge directly upwards, and 
 is then made fast while the boat goes ahead. The 
 dredge is thus dragged along and scrapes oysters 
 and other sea-animals and plants, stones, and 
 mud into the bag. When the dredger judges it 
 to be full he hauls it up, picks out the oys- 
 ters, throws the rest overboard, and begins 
 again. 
 
 Dredging in shallow water, say ten to twenty 
 fathoms, is an easy operation enough; but the 
 deeper the dredger goes, the heavier must be his 
 vessel, and the stouter his tackle, while the opera- 
 tion of hauling up becomes more and more labo- 
 rious. Dredging in 150 fathoms is very hard work, 
 if it has to be carried on by manual labour; but 
 by the use of the donkey-engine to supply power,* 
 and of the contrivances known as " accumulators," 
 to diminish the risk of snapping the dredge rope 
 by the rolling and pitching of the vessel, the 
 
 * The emotional side of the scientific nature has its 
 singularities. Many persons will call to mind a certain 
 philosopher's tenderness over his watch — " the little crea- 
 ture " — which was so singularly lost and found again. 
 But Dr. Wyville Thomson surpasses the owner of the 
 watch in his loving-kindness towards a donkey-engine. 
 " This little engine was the comfort of our lives. Once 
 or twice it was overstrained, and then we pitied the will- 
 ing little thing, panting like an overtaxed horse." 
 
42 THE PROBLEMS OP THE DEEP SEA. n 
 
 dredge has been worked deeper and deeper, until 
 at last, on the 32nd of July, 1869, H.M.S. Porcu- 
 pine being in the Bay of Biscay, Captain Calver, 
 her commander, performed the unprecedented 
 feat of dredging in 2,435 fathoms, or 14,610 feet, a 
 depth nearly equal to the height of Mont Blanc. 
 The dredge " was rapidly hauled on deck at one 
 o'clock in the morning of the 83rd, after an ab- 
 sence of 7i hours, and a journey of upwards of 
 eight statute miles," with a hundred weight and a 
 half of solid contents. 
 
 The trawl is a sort of net for catching those 
 fish which habitually live at the bottom of the sea, 
 such as soles, plaice, turbot, and gurnett. The 
 mouth of the net may be thirty or forty feet wide, 
 and one edge of its mouth is fastened to a beam 
 of wood of the same length. The two ends of 
 the beam are supported by curved pieces of iron, 
 which raise the beam and the edge of the net 
 which is fastened to it, for a short distance, while 
 the other edge of the mouth of the net trails upon 
 the ground. The closed end of the net has the 
 form of a great pouch; and, as the beam is dragged 
 along, the fish, roused from the bottom by the 
 sweeping of the net, readily pass into its mouth 
 and accumulate in the pouch at its end. After 
 drifting with the tide for six or seven hours the 
 trawl is hauled up, the marketable fish are picked 
 out, the others thrown away, and the trawl sent 
 overboard for another operation. 
 
n THE PROBLEMS OP THE DEEP SEA. 43 
 
 More than a thousand sail of well-found trawl- 
 ers are constantly engaged in sweeping the seas 
 around our coast in this way, and it is to them 
 that we owe a very large proportion of our supply 
 of fish. The difficulty of trawling, like that of 
 dredging, rapidly increases with the depth at 
 which the operation is performed; and, until the 
 other day, it is probable that trawling at so great 
 a depth as 100 fathoms was something unheard of. 
 But the first news from the Challenger opens up 
 new possibilities for the trawl. 
 
 Dr. Wyville Thomson writes (" Nature," 
 March 20, 1873):— 
 
 "For the first two or three hauls in very deep water 
 off the coast of Portugal, the dredge came up filled with 
 the usual ' Atlantic ooze,' tenacious and uniform through- 
 out, and the work of hours, in sifting, gave the very 
 smallest possible result. We were extremely anxious to 
 get some idea of the general character of the Fauna, and 
 particularly of the distribution of the higher groups; 
 and after various suggestions for modification of the 
 dredge, it was proposed to try the ordinary trawl. We 
 had a compact trawl, with a 15-feet beam, on board, and 
 we sent it down off Cape St. Vincent at a depth of 600 
 fathoms. The experiment looked hazardous, but, to our 
 great satisfaction, the trawl came up all right and con- 
 tained, with many of the larger invertebrata, several fishes. 
 . . . After the first attempt we tried the trawl several 
 times at depths of 1090, 1525, and, finally, 2125 fathoms, 
 and always with success." 
 
 To the coral-fishers of the Mediterranean, who 
 seek the precious red coral, which grows firmly 
 
44: THE PROBLEMS OP THE DEEP SEA. ii 
 
 fixed to rocks at a depth of sixty to eighty fathoms, 
 both the dredge and the trawl would be useless. 
 They, therefore, have recourse to a sort of frame, 
 to which are fastened long bundles of loosely net- 
 ted hempen cord, and which is lowered by a rope 
 to the depth at which the hempen cords can sweep 
 over the surface of the rocks and break ofE the 
 coral, which is brought up entangled in the cords. 
 A similar contrivance has arisen out of the neces- 
 sities of deep-sea exploration. 
 
 In the course of the dredging of the Porcupine, 
 it was frequently found that, while few objects of 
 interest were brought up within the dredge, many 
 living creatures came up sticking to the outside of 
 the dredge-bag, and even to the first few fathoms 
 of the dredge-rope. The mouth of the dredge 
 doubtless rapidly filled with mud, and thus the 
 things it should have brought up were shut out. 
 To remedy this inconvenience Captain Calver de- 
 vised an arrangement not unlike that employed by 
 the coralrfishers. He fastened half a dozen swabs, 
 such as are used for drying decks, to the dredge. 
 A swab is something like what a birch-broom 
 would be if its twigs were made of long, coarse, 
 hempen yarns. These dragged along after the 
 dredge over the surface of the mud, and entangled 
 the creatures living there — multitudes of wlfich, 
 twisted up in the strands of the swabs, were 
 brought to the surface with the dredge. A fur- 
 ther improvement was made by attaching a long 
 
11 THE PROBLEMS OF. THE DEEP SEA. 45 
 
 iron bar to the bottom of the dredge bag, and fas- 
 tening large bunches of teased-out hemp to the 
 end of this bar. These " tangles " bring up im- 
 mense quantities of such animals as have long 
 arms, or spines, or prominences which readily be- 
 come caught in the hemp, but they are very de- 
 structive to the fragile organisms which they 
 imprison; and, now that the trawl can be suc- 
 cessfully worked at the greatest depths, it may 
 be expected to supersede them; at least, wher- 
 ever the ground is soft enough to permit of trawl- 
 ing. 
 
 It is obvious that between the dredge, the 
 trawl, and the tangles, there is little chance for 
 any organism, except such as are able to burrow 
 rapidly, to remain safely at the bottom of any part 
 of the sea which the Challenger undertakes to ex- 
 plore. And, for the first time in the history of 
 scientific exploration, we have a fair chance of 
 learning what the population of the depths of the 
 sea is like in the most widely different parts of the 
 world. 
 
 And now arises the next question. The means 
 of exploration being fairly adequate, what forms 
 of life may be looked for at these vast depths? 
 
 The systematic study of the Distribution of 
 living beings is the most modern branch of Bio- 
 logical Science, and came into existence long after 
 Morphology and Physiology had attained a con- 
 siderable development. This naturally does not 
 
46 THE PROBLEMS OF THE DEEP SEA. n 
 
 imply that, from the time men began to observe 
 natural phenomena, they were ignorant of the fact 
 that the animals and plants of one part of the 
 world are different from those in other regions; or 
 that those of the hills are different from those of 
 the plains in the same region; or finally that some 
 marine creatures are found only in the shallows, 
 while others inhabit the deeps. Nevertheless, it 
 was only after the discovery of America that the 
 attention of naturalists was powerfully drawn to 
 the wonderful differences between the animal 
 population of the central and southern parts of the 
 new world and that of those parts of the old world 
 which lie under the same parallels of latitude. So 
 far back as 1667 Abraham Mylius, in his treatise 
 " De Animalium origine et migratione popu- 
 lorum," argues that, since there are innumerable 
 species of animals in America which do not exist 
 elsewhere, they must have been made and placed 
 there by the Deity: Buff on no less forcibly in- 
 sists upon the difference between the Faunae of 
 the old and new world. But the first attempt to 
 gather facts of this order into a whole, and to co- 
 ordinate them into a series of generalizations, or 
 laws of Geographical Distribution, is not a century 
 old, and is contained in the " Specimen Zoologiag 
 Geographicse Quadrupedum Domicilia et Migra- 
 tiones sistens," published, in 1777, by the learned 
 Brunswick Professor, Eberhard Zimmermann, who 
 illustrates his work by what he calls a "Tabula 
 
II THE PROBLEMS OP THE DEEP SEA. 47 
 
 Zoographica," which is the oldest distributional 
 map known to me. 
 
 In regard to matters of fact, Zimmermann's 
 chief aim is to show that among terrestrial mam- 
 mals, some occur all over the world, while others 
 are restricted to particular areas of greater or 
 smaller extent; and that the abundance of species 
 follows temperature, being greatest in warm and 
 least in cold climates. But marine animals, he 
 thinks, obey no such law. The Arctic and Atlan- 
 tic seas, he says, are as full of fishes and other 
 animals as those of the tropics. It is, therefore, 
 clear that cold does not affect the dwellers in the 
 sea as it does land animals, and that this must be 
 the case follows from the fact that sea water, 
 " propter varias quas continet bituminis spiritus- 
 que particulas," freezes with much more diificulty 
 than fresh water. On the other hand, the heat of 
 the Equatorial sun penetrates but a short distance 
 below the surface of the ocean. Moreover, accord- 
 ing to Zimmermann, the incessant disturbance of 
 the mass of the sea by winds and tides, so mixes 
 up the warm and the cold that life is evenly dif- 
 fused and abundant throughout the ocean. 
 
 In 1810, Eisso, in his work on the Ichthyology 
 of Nice, laid the foundation of what has since been 
 termed " bathymetrieal " distribution, or distribu- 
 tion in depth, by showing that regions of the sea 
 bottom of different depths could be distinguished 
 by the fishes which inhabit them. There was the 
 
48 THE PROBLEMS OP THE DEEP SEA. n 
 
 littoral region between tide marks with its sand- 
 eels, pipe fishes, and blennies: the seaweed region, 
 extending from lowwater-mark to a depth of 450 
 feet, with its wrasses, rays, and flat fish; and the 
 deep-sea region, from 450 feet to 1500 feet or 
 more, with its file-fish, sharks, gurnards, cod, and 
 sword-fish. 
 
 More than twenty years later, MM. Audouin 
 and Milne Edwards carried out the principle of 
 distinguishing the Faunae of different zones of 
 depth much more minutely, in their " Eecherches 
 pour servir a I'Histoire Naturelle du Littoral de la 
 France," published in 1833. 
 
 They divide the area included between high- 
 water-mark and lowwater-ihark of spring tides 
 (which is very extensive, on account of the great 
 rise and fall of the tide on the Normandy coast 
 about St. Malo, where their observations were 
 made) into four zones, each characterized by its 
 peculiar invertebrate inhabitants. Beyond the 
 fourth region they distinguish a fifth, which is 
 never uncovered, and is inhabited by oysters, scal- 
 lops, and large starfishes and other animals. Be- 
 yond this they seem to think that animal life is 
 absent.* 
 
 Audouin and Milne Edwards were the first to 
 
 * " Enfin plus bas encore, e'est-adire a!ors loin des 
 cOtes, le fond des eaux ne paratt plus etre habitfi, du 
 moins dans nos mers, par aucun de ees aniinaux " (1. e. 
 torn. i. p. 237). The "ees animaux " leaves the meaning 
 of the authors doubtful. 
 
II THE PROBLEMS OP THE DEEP SEA. 49 
 
 see the importance of the hearing of a knowledge 
 of the manner in which marine animals are dis- 
 tributed in depth, on geology. They suggest that, 
 by this means, it will he possible to judge whether 
 a fossiliferous stratum was formed upon the shore 
 of an ancient sea, and even to determine whether 
 it was deposited in shallower or deeper water on 
 that shore; the association of shells of animals 
 which live in different zones of depth will prove 
 that the shells have been transported into the posi- 
 tion in which they are found; while, on the other 
 hand, the absence of shells in a deposit will not 
 justify the conclusion that the waters in which it 
 was formed were devoid of animal inhabitants, in- 
 asmuch as they might have been only too deep for 
 habitation. 
 
 The new line of investigation thus opened by 
 the French naturalists was followed up by the 
 Norwegian, Sars, in 1835, by Edward Forbes, in 
 our own country, in 1840,* and by (Ersted, in 
 
 * In the paper in the Memoirs of the Survey cited fur- 
 ther on, Forbes writes: — 
 
 " In an essay ' On the Association of Alollusca on the 
 British Coasts, considered with reference to Pleistocene 
 Geology,' printed in [the Edinburgh Academic Annual 
 for] 1840, I described the moUusca, as distributed on our 
 shores and seas, in fovrr great zones or regions, usually de- 
 nominated ' The Littoral Zone,' ' The region of Larai- 
 nariae,' ' The region of Corallines,' and ' The region of 
 Corals.' An extensive series of researches, chiefly con- 
 ducted by the members of the committee appointed by 
 the British Association to investigate the marine geology 
 of Britain by means of the dredge, have not invalidated 
 this classification, and the researches of Professor Loven, 
 190 
 
50 THE PROBLEMS OF THE DEEP SEA. n 
 
 Denmark, a few years later. The genius of 
 Forbes, combined with his extensive knowledge of 
 botany, invertebrate zoology, and geology, enabled 
 him to do more than any of his compeers, in bring- 
 ing the importance of distribution in depth into 
 notice; and his researches in the iEgean Sea, and 
 still more his remarkable paper " On the Geo- 
 logical Kelations of the existing Fauna and Flora 
 of the British Isles," published in 1846, in the first 
 volume of the " Memoirs of the Geological Survey 
 of Great Britain," attracted universal attention. 
 
 On the coasts of the British Islands, Forbes 
 distinguishes four zones or regions, the Littoral 
 (between tide marks), the Laminarian (between 
 low water-mark and 15 fathoms), the Coralline 
 (from 15 to 50 fathoms), and the Deep Sea or 
 Coral region (from 50 fathoms to beyond 100 
 fathoms). But, in the deeper waters of the ^ge- 
 an Sea, between the shore and a depth of 300 
 fathoms, Forbes was able to make out no fewer 
 than eight zones of life, in the course of which 
 the number and variety of forms gradually dimin- 
 ished; until, beyond 300 fathoms, life disappeared 
 altogether. Hence it appeared as if descent in the 
 sea had much the same effect on life, as ascent 
 
 in the Norwegian and Lapland seas, have borne out their 
 correctness. The first two of the regions above men- 
 tioned had been previously noticed by Lamouroux, in his 
 account of the distribution (vertically) of sea- weeds, by 
 Audouin and Milne Edwards in their Observations on the 
 Natural History of the coast of France, and by Sars in 
 the preface to his Beskrivelser eg Jagttagelser." 
 
n THE PROBLEMS OP THE DEEP SEA. 51 
 
 on land. Eecent investigations appear to show 
 that Forbes was right enough in his classification 
 of the facts of distribution in depth as they are to 
 be observed in the JEgean; and though, at the 
 time he wrote, one or two observations were ex- 
 tant which might have warned him not to gen- 
 eralize too extensively from his iEgean experi- 
 ence, his own dredging work was so much more 
 extensive and systematic than that of any other 
 naturalist, that it is not wonderful he should have 
 felt justified in building upon it. Nevertheless, 
 so far as the limit of the range of life in depth 
 goes, Forbes' conclusion has been completely nega- 
 tived, and the greatest depths yet attained show 
 not even an approach to a " zero of life ": — 
 
 " During the several cruises of H.M. ships LigMning 
 and Porcupine in the years 1868, 1869, and 1870," says Dr. 
 Wyville Thomson, "fifty-seven hauls of the dredge were 
 taken in the Atlantic at depths beyond 500 fathoms, and 
 sixteen at depths beyond 1,000 fathoms, and, in all cases, 
 life was abundant. In 1869, we took two casts in depths 
 greater than 2,000 fathoms. In both of these life was 
 abundant; and with the deepest cast, 2,435 fathoms, off 
 the mouth of the Bay of Biscay, we took living, well- 
 marked and characteristic examples of all the five inver- 
 tebrate sub-kingdoms. And thus the question of the ex- 
 istence of abundant animal life at the bottom of the sea 
 has been finally settled and for all depths, for there is no 
 reason to suppose that the depth anywhere exceeds be- 
 tween three and four thousand fathoms; and if there be 
 nothing in the conditions of a depth of 2,500 fathoms to 
 prevent the full development of a varied Fauna, it is im- 
 
52 THE PROBLEMS OF THE DEEP SEA. n 
 
 possible to suppose that even an additional thousand 
 fathoms would make any great difference." * 
 
 As Dr. Wyville Thomson's recent letter, cited 
 above, shows, the use of the trawl, at great depths, 
 has brought to life a still greater diversity of life. 
 Fishes came np from a depth of 600 to more than 
 1,000 fathoms, all "in a peculiar condition from 
 the expansion of the air contained in their bodies. 
 On their relief from the extreme pressure, their 
 eyes, especially, had a singular appearance, pro- 
 truding like great globes from their heads." Bi- 
 valve and univalve mollusca seem to be rare at the 
 greatest depths; but starfishes, sea urchins, and 
 other echinoderms, zoophytes, sponges, and pro- 
 tozoa abound. 
 
 It is obvious that the Challenger has the privi- 
 lege of opening a new chapter in the history of 
 the living world. She cannot send down her 
 dredges and her trawls into these virgin depths of 
 the great ocean without bringing up a discovery. 
 Even though the thing itself may be neither 
 "rich nor rare," the fact that it came from that 
 
 * The Depths of the Sea, p. 30. Eesults of a similar 
 kind, obtained by previous observers, are stated at length 
 in the sixth chapter, pp. 267-280. The dredgings car- 
 ried out by Count Pourtales, under the authority of 
 Professor Peiree, the Superintendent of the United States 
 Coast Survey, in the years 1867, 1868, and 1869, are par- 
 ticularly noteworthy, and it is probably not too much to 
 say, in the words of Professor Agassiz, " that we owe to 
 the coast survey the first broad and comprehensive basis 
 for an exploration of the sea bottom on a large scale, 
 opening a new era in zoological and geological research." 
 
n THE PROBLEMS OP THE DEEP SEA. 53 
 
 depth, in that particular latitude and longitude, 
 will he a new fact in distribution, and, as such, 
 have a certain importance. 
 
 But it may he coniidently assumed that the 
 things brought up will very frequently be zoo- 
 logical novelties; or, better still, zoological an- 
 tiquities, which, in the tranquil and little-changed 
 depths of the ocean, have escaped the causes 
 of destruction at work in the shallows, and repre- 
 sent the predominant population of a past age. 
 
 It has been seen that Audouin and Milne 
 Edwards foresaw the general influence of the 
 study of distribution in depth upon the interpreta- 
 tion of geological phenomena. Forbes connected 
 the two orders of inquiry still more closely; and 
 in the thoughtful essay " On the connection be- 
 tween the distribution of the existing Fauna and 
 Flora of the British Isles, and the geological 
 changes which have affected their area, especially 
 during the epoch of the Northern drift," to which 
 reference has already been made, he put forth a 
 most pregnant suggestion. 
 
 In certain parts of the sea bottom in the imme- 
 diate vicinity of the British Islands, as in the 
 Clyde district, among the Hebrides, in the Moray 
 Firth, and in the German Ocean, there are de- 
 pressed arese, forming a kind of submarine valleys, 
 the centres of which are from 80 to 100 fathoms, 
 or more, deep. These depressions are inhabited 
 by assemblages of marine animals, which differ 
 
54. THE PROBLEMS OF THE DEEP SEA. n 
 
 from those found over the adjacent and shallower 
 region, and resemble those which are met with 
 much farther north, on the Norwegian coast. 
 Forbes called these Scandinavian detachments 
 " Northern outliers." 
 
 How did these isolated patches of a northern 
 population get into these deep places? To ex- 
 plain the mystery, Forbes called to mind the 
 fact that, in the epoch which immediately pre- 
 ceded the present, the climate was much colder 
 (whence the name of " glacial epoch " applied to 
 it); and that the shells which are found fossil, or 
 sub-fossil, in deposits of that age are precisely such 
 as are now to be met with only in the Scandi- 
 navian, or still more Arctic, regions. Undoubted- 
 ly, during the glacial epoch, the general population 
 of our seas had, universally, the northern aspect 
 which is now presented only by the " northern out- 
 liers "; just as the vegetation of the land, down to 
 the sea-level, had the northern character which is, 
 at present, exhibited only by the plants which live 
 on the tops of our mountains. But, as the glacial 
 epoch passed awa,y, and the present climatal con- 
 ditions were developed, the northern plants were 
 able to maintain themselves only on the bleak 
 heights, on which southern forms could not com- 
 pete with them. And, in like manner, Forbes sug- 
 gested that, after the glacial epoch, the northern 
 animals then inhabiting the sea became restricted 
 to the deeps in which they could hold their own 
 
n THE PROBLEMS OP THE DEEP SEA. 55 
 
 against invaders from the south, better fitted than 
 they to flourish in the warmer waters of the 
 shallows. Thus depth in the sea corresponded in 
 its efliect upon distribution to height on the land. 
 
 The same idea is applied to the explanation of 
 a similar anomaly in the Fauna of the JSgean: — 
 
 " In the deepest of the regions of depth of the ^gean, 
 the representation of a Northertt Fauna is maintained, 
 partly by identical and partly by representative forms. 
 . . . The presence of the latter is essentially due to the 
 law (of representation of parallels of latitude by zones 
 of depth), whilst that of the former species depended on 
 their transmission from their parent seas during a former 
 epoch, and subsequent isolation. That epoch was doubt- 
 less the newer Pliocene or Glacial Era, when the Mya 
 truncata and other northern forms now extinct in the 
 Mediterranean, and found fossil in the Sicilian tertiaries, 
 ranged into that sea. The changes which there destroyed 
 the shallow water glacial forms, did not affect those liv- 
 ing in the depths, and which still survive." * 
 
 The conception that the inhabitants of local 
 depressions of the sea bottom might be a remnant 
 of the ancient population of the area, which had 
 held their own in these deep fastnesses against an 
 invading Fauna, as Britons and Gaels have held 
 out in Wales and Scotland against encroaching 
 Teutons, thus broached by Forbes, received a 
 wider application than Forbes had dreamed of 
 when the sounding machine first brought up 
 
 • Memoirs of the Qcological Survey of Great Britain, 
 Vol. i. p. 390. 
 
56 THE PROBLEMS OP THE DEEP SEA. ii 
 
 specimens of the mud of the deep sea. As I have 
 pointed out elsewhere,* it at once became obvious 
 that the calcareous sticky mud of the Atlantic 
 was made up, in the main, of shells of Glohigerina 
 and other Foraminifera, identical with those of 
 which the true chalk is composed, and the identity 
 extended even to the presence of those singular 
 bodies, the Coccoliths and Coccospheres, the true 
 nature of which is not yet made out. Here then 
 were organisms, as old as the cretaceous epoch, 
 still alive, and doing their work of rock-making at 
 the bottom of existing seas. What if Glohigerina 
 and the Coccoliths should not be the only sur- 
 vivors of a world passed away, which are hidden 
 beneath three miles of salt water? The letter 
 which Dr. Wyville Thomson wrote to Dr. Car- 
 penter in May, 1868, out of which all these expe- 
 ditions have grown, shows that this query had 
 become a practical problem in Dr. Thomson's 
 mind at that time; and the desirableness of solv- 
 ing the problem is put in the foreground of his 
 reasons for urging the Government to undertake 
 the work of exploration: — 
 
 "Two years ago, M. Sars, Swedish Government In- 
 spector of Fisheries, had an opportunity, in his official 
 capacity, of dredging off the Loffoten Islands at a depth 
 of 300 fathoms. I visited Norway shortly after his re- 
 turn, and had an opportunity of studying with his father, 
 Professor Sars, some of his results. Animal forms were 
 
 • See above, " On a Piece of Chalk," p. 13. 
 
II THE PROBLEMS OF THE DEEP SEA. 57 
 
 abundant; many of them were new to science; and 
 among them was one of surpassing interest, the small 
 crinoid, of which you have a specimen, and which we at 
 once recognised as a degraded type of the Apiocrinidw, 
 an order hitherto regarded as extinct, which attained its 
 maximum in the Pear Enerinites of the Jurassic period, 
 and whose latest .^representative hitherto known was the 
 Bourguettocrinus of the chalk. Some years previously, 
 Mr. Absjornsen, dredging in 200 fathoms in the Hardan- 
 gerfjord, procured several examples of a Starfish {Bri- 
 singa), which seems to find its nearest ally in the fossil 
 genus Protaster. These observations place it beyond a 
 doubt that animal life is abundant in the oeea,n at depths 
 varying from 200 to 300 fathoms, that the forms at these 
 great depths differ greatly from those met with in ordi- 
 nary dredgings, and that, at all events in some eases, 
 these animals are closely allied to, and would seem to be 
 directly descended from, the Fauna of the early tertiaries. 
 " I think the latter result might almost have been an- 
 ticipated; and, probably, further investigation will large- 
 ly add to this class of data, and will give us an oppor- 
 tunity of testing our determinations of the zoological po- 
 sition of some fossil types by an examination of the soft 
 parts of their recent representatives. The main cause of 
 the destruction, the migration, and the extreme modifi- 
 cation of animal types, appears to be change of climate, 
 chiefly depending upon oscillations of the earth's crust. 
 These oscillations do not appear to have ranged, in the 
 Northern portion of the Northern Hemisphere, much be- 
 yond 1,000 feet since the commencement of the Tertiary 
 Epoch. The temperature of deep waters seems to be con- 
 stant for all latitudes at 39°; so that an immense area 
 of the North Atlantic must have had its conditions un- 
 affected by tertiary or post-tertiary oscillations."* 
 
 * The Depths of the Sea, pp. 51-52. 
 
58 THE PROBLEMS OP THE DEEP SEA. ii 
 
 As we shall see, the assumption that the tem- 
 perature of the deep sea is everywhere 39° F. (4° 
 Cent.) is an error, which Dr. Wyville Thomson 
 adopted from eminent physical writers; but the 
 general justice of the reasoning is not affected 
 by this circumstance, and Dr. Thomson's expec- 
 tation has been, to some extent, already veri- 
 fied. 
 
 Thus besides Glohigerina, there are eighteen 
 species of deep-sea Foraminifera identical with 
 species found in the chalk. Imbedded in the 
 chalky mud of the deep sea, in many localities, 
 are innumerable cup-shaped sponges, provided 
 with six-rayed silicious spicula, so disposed that 
 the wall of the cup is formed of a lacework of 
 flinty thread. Not less abundant, in some parts 
 of the chalk formation, are the fossils known as 
 Ventriculites, well described by Dr. Thomson as 
 " elegant vases or cups, with branching root-like 
 bases, or groups of regularly or irregularly spread- 
 ing tubes delicately fretted on the surface with 
 an impressed network like the finest lace "; and 
 he adds, " When we compare such recent forms as 
 Aphrocallistes, Iphiteon, Holtenia, and Ashonema, 
 with certain series of the chalk Ventriculites, there 
 cannot be the slightest doubt that they belong to 
 the same family — in some cases to very nearly al- 
 lied genera." * 
 
 Professor Duncan finds " several corals from 
 * TTw Depths of the Sea, p. 484. 
 
II THE PROBLEMS OP THE DEEP SEA. 59 
 
 the coast of Portugal more nearly allied to chalk 
 forms than to any others." 
 
 The Stalked Crinoids or Feather Stars, so 
 abundant in ancient times, are now exclusively 
 confined to the deep sea, and the late explorations 
 have yielded forms of old affinity, the existence of 
 which has hitherto been unsuspected. The gen- 
 eral character of the group of star fishes imbedded 
 in the white chalk is almost the same as in the 
 modern Fauna of the deep Atlantic. The sea 
 urchins of the deep sea, while none of them are 
 specifically identical with any chalk form, belong 
 to the same general groups, and some closely ap- 
 proach extinct cretaceous genera. 
 
 Taking these facts in conjunction with the 
 positive evidence of the existence, during the 
 Cretaceous epoch, of a deep ocean where now lies 
 the dry land of central and southern Europe, 
 northern Africa, and western and southern Asia; 
 and of the gradual diminution of this ocean during 
 the older tertiary epoch, until it is represented at 
 the present day by such teacupfuls as the Caspian, 
 the Black Sea, and the Mediterranean; the suppo- 
 sition of Dr. Thomson and Dr. Carpenter that 
 what is now the deep Atlantic, was the deep At- 
 lantic (though merged in a vast easterly extension) 
 in the Cretaceous epoch, and that the Glohigerina 
 mud has been accumulating there from that time 
 to this, seems to me to have a great degree of prob- 
 ability. And I agree with Dr. Wyville Thomson 
 
60 THE PROBLEMS OP THE DEEP SEA. ii 
 
 against Sir Charles Lyell (it takes two of us to 
 have any chance against his authority) in de- 
 murring to the assertion that " to talk of chalk 
 having been uninterruptedly formed in the At- 
 lantic is as inadmissible in a geographical as in a 
 geological sense." 
 
 If the word " chalk " is to be used as a strati- 
 graphical term and restricted to Glohigerina mud 
 deposited during the Cretaceous epoch, of course 
 it is improper to call the precisely similar mud of 
 more recent date, chalk. If, on the other hand, 
 it is to be used as a mineralogical term, I do not 
 see how the modern and the ancient chalks are 
 to be separated — and, looking at the matter geo- 
 graphically, I see no reason to doubt that a bor- 
 ing rod driven from the surface of the mud which 
 forms the floor of the mid-Atlantic would pass 
 through one continuous mass of Glohigerina mud, 
 first of modern, then of tertiary, and then of me- 
 sozoic date; the " chalks " of different depths and 
 ages being distinguished merely by the different 
 forms of other organisms associated with the Gldbi- 
 gerincB. 
 
 On the other hand, I think it must be admitted 
 that a belief in the continuity of the modern with 
 the ancient chalk has nothing to do with the 
 proposition that we can, in any sense whatever, 
 be said to be still living in the Cretaceous epoch. 
 When the Challenger's trawl brings up an Ich- 
 thyosaurus, along with a few living specimens 
 
II THE PROBLEMS OF THE DEEP SEA. 61 
 
 of Belemnites, and Turrilites, it may be admitted 
 that she has come upon a cretaceous " outlier." 
 A geological period is characterized not only by 
 the presence of those creatures which lived in 
 it, but by the absence of those which have only 
 come into existence later; and, however large a 
 proportion of true cretaceous forms may be dis- 
 covered in the deep sea, the modern types asso- 
 ciated with them must be abolished before the 
 Fauna, as a whole, could, with any propriety, be 
 termed Cretaceous. 
 
 I have now indicated some of the chief lines of 
 Biological inquiry, in which the Challenger has 
 special opportunities for doing good service, and 
 in following which she will be carrying out the 
 work already commenced by the Lightning and 
 Porcupine in their cruises of 1868 and subsequent 
 years. 
 
 But biology, in the long run, rests upon 
 physics, and the first condition for arriving at a 
 sound theory of distribution in the deep sea, is the 
 precise ascertainment of the conditions of life; or, 
 in other words, a full knowledge of all those phe- 
 nomena which are embraced under the head of the 
 Physical Geography of the Ocean. 
 
 Excellent work has already been done in this 
 direction, chiefly under the superintendence of Dr. 
 Carpenter, by the Lightning and the Porcupine* 
 * Proceedings of tJte Royal Societi/, 1870 and 1872. 
 
G2 THE PROBLEMS OP THE DEEP SEA. n 
 
 and some data of fundamental importance to the 
 physical geography of the sea have been fixed be- 
 yond a doubt. 
 
 Thus, though it is true that sea-water steadily 
 contracts as it cools down to its freezing point, 
 instead of expanding before it reaches its freezing 
 point as fresh water does, the truth has been 
 steadily ignored by even the highest authorities 
 in physical geography, and the erroneous con- 
 clusions deduced from their erroneous premises 
 have been widely accepted as if they were ascer- 
 tained facts. Of course, if sea-water, like fresh 
 water, were heaviest at a temperature of 39° F. 
 and got lighter as it approached 38° F., the water 
 of the bottom of the deep sea could not be colder 
 than 39°. But one of the first results of the 
 careful ascertainment of the temperature at dif- 
 ferent depths, by means of thermometers specially 
 contrived for the avoidance of the errors pro- 
 duced by pressure, was the proof that, below 1000 
 fathoms in the Atlantic, down to the greatest 
 depths yet sounded, the water has a temperature 
 always lower than 38° Fahr., whatever be the 
 temperature of the water at the surface. And 
 that this low temperature of the deepest water is 
 probably the universal rule for the depths of the 
 open ocean is shown, among others, by Captain 
 Chimmo's recent observations in the Indian ocean, 
 between Ceylon and Sumatra, where, the surface 
 water ranging from 85° — 81° Fahr., the tempera- 
 
II THE PROBLEMS OP THE DEEP SEA. 63 
 
 ture at the bottom, at a depth of 2370 to 3656 
 fathoms, was only from 34° to 32° Fahr. 
 
 As the mean temperature of the superficial 
 layer of the crust of the earth may be taken at 
 about 50° Fahr., it follows that the bottom layer 
 of the deep sea in temperate and hot latitudes 
 is, on the average, much colder than either of the 
 bodies with which it is in contact; for the tem- 
 perature of the earth is constant, while that of 
 the air rarely falls so low as that of the bottom 
 water in the latitudes in question; and even when 
 it does, has time to affect only a comparatively 
 thin stratum of the surface water before the re- 
 turn of warm weather. 
 
 How does this apparently anomalous state of 
 things come about? If we suppose the globe to 
 be covered with a universal ocean, it can hardly 
 be doubted that the cold of the regions towards 
 the poles must tend to cause the superficial water 
 of those regions to contract and become specifically 
 heavier. Under these circumstances, it would 
 have no alternative but to descend and spread 
 over the sea bottom, while its place would be 
 taken by warmer water drawn from the adjacent 
 regions. Thus, deep, cold, polar-equatorial cur- 
 rents, and superficial, warmer, equatorial-polar 
 currents, would be set up, and as the former would 
 have a less velocity of rotation from west to east 
 than the regions towards which they travel, they 
 would not be due southerly or northerly currents. 
 
64 THE PROBLEMS OP THE DEEP SEA. n 
 
 but south-westerly in the northern hemisphere, 
 and north-westerly in the southern; while, by a 
 parity of reasoning, the equatorial-polar warm cur- 
 rents would be north-easterly in the northern 
 hemisphere, and south-easterly in the southern. 
 Hence, as a north-easterly current has the same 
 direction as a south-westerly wind, the direction of 
 the northern equatorial-polar current in the extra- 
 tropical part of its course would pretty nearly coin- 
 cide with that of the anti-trade winds. The freez- 
 ing of the surface of the polar sea would not in- 
 terfere with the movement thus set up. For, 
 however bad a conductor of heat ice may be, the 
 unfrozen sea-water immediately in contact with 
 the undersurface of the ice must needs be colder 
 than that further off; and hence will constantly 
 tend to descend through the subjacent warmer 
 water. 
 
 In this way, it would seem inevitable that the 
 surface waters of the northern and southern frigid 
 zones must, sooner or later, find their way to the 
 bottom of the rest of the ocean; and there ac- 
 cumulate to a thickness dependent on the rate at 
 which they absorb heat from the crust of the earth 
 below, and from the surface water above. 
 
 If this hypothesis be correct, it follows that, if 
 any part of the ocean in warm latitudes is shut oflE 
 from the influence of the cold polar underflow, 
 the temperature of its deeps should be less cold 
 than the temperature of corresponding depths in 
 
II THE PROBLEMS OF THE DEEP SEA. 65 
 
 the open sea. Now, in the Mediterranean, Nature 
 offers a remarkable experimental proof of just the 
 kind needed. It is a landlocked sea which runs 
 nearly east and west, between the twenty-ninth 
 and forty-fifth parallels of north latitude. Eough- 
 ly speaking, the average temperature of the air 
 over it is 75° Fahr. in July and 48° in January. 
 
 This great expanse of water is divided by the 
 peninsula of Italy (including Sicily), continuous 
 with which is a submarine elevation carrying less 
 than 1,300 feet of water, which extends from 
 Sicily to Cape Bon in Africa, into two great pools 
 — an eastern and a western. The eastern pool 
 rapidly deepens to more than 12,000 feet, and 
 sends off to the north its comparatively shallow 
 branches, the Adriatic and the iEgean Seas. The 
 western pool is less deep,' though it reaches some 
 10,000 feet. And, just at the western end of the 
 eastern pool communicates by a shallow passage, 
 not a sixth of its greatest depth, with the western 
 pool, so the western pool is separated from the 
 Atlantic by a ridge which runs between Capes 
 Trafalgar and Spartel, on which there is hardly 
 1,000 feet of water. All the water of the Mediter- 
 ranean which lies deeper than about 150 fathoms, 
 therefore, is shut ofE from that of the Atlantic, 
 and there is no communication between the cold 
 layer of the Atlantic (below 1,000 fathoms) and 
 the Mediterranean. Under these circumstances, 
 what is the temperature of the Mediterranean? 
 191 
 
QQ THE PROBLEMS OF THE DEEP SEA. n 
 
 Everywhere below 600 feet it is about 55° Falir.; 
 and consequently, at its greatest depths, it is some 
 20° warmer than the corresponding depths of the 
 Atlantic. 
 
 It seems extremely difficult to account for this 
 difference in any other way, than by adopting 
 the views so strongly and ably advocated by Dr. 
 Carpenter, that, in the existing distribution of 
 land and water, such a circulation of the water of 
 the ocean does actually occur, as theoretically must 
 occur, in the universal ocean, with which we 
 started. 
 
 It is quite another question, however, whether 
 this theoretic circulation, true cause as it may be, 
 is competent to give rise to such movements of 
 sea-water, in mass, as those currents, which have 
 commonly been regarded as northern extensions of 
 the Gulf-stream. I shall not venture to touch 
 upon this complicated problem; but I may take 
 occasion to remark that the cause of a much sim- 
 pler phenomenon — the stream of Atlantic water 
 which sets through the Straits of Gibraltar, east- 
 ward, at the rate of two or three miles an hour 
 or more, does not seem to be so clearly made out 
 as is desirable. 
 
 The facts appear to be that the water of the 
 Mediterranean is very slightly denser than that of 
 the Atlantic (1.0378 to 1.0865), and that the deep 
 water of the Mediterranean is slightly denser than 
 that of the surface; while the deep water of the 
 
II THE PROBLEMS OF THE DEEP SEA. 67 
 
 Atlantic is, if anything, lighter than that of the 
 surface. MoreoTer, while a rapid superficial cur- 
 rent is setting in (always, save in exceptionally 
 violent easterly winds) through the Straits of Gib- 
 raltar, from the Atlantic to the Mediterranean, 
 a deep undercurrent (together with variable side 
 currents) is setting out through the Straits, from 
 the Mediterranean to the Atlantic. 
 
 Dr. Carp&nter adopts, without hesitation, the 
 view that the cause of this indraught of Atlantic 
 water is to be sought in the much more rapid 
 evaporation which takes place from the surface of 
 the Mediterranean than from that of the Atlantic; 
 and thus, by lowering the level of the former, 
 gives rise to an indraught from the latter. 
 
 But is there any sound foundation for the 
 three assumptions involved here? Firstly, that 
 the evaporation from the Mediterranean, as a 
 whole, is much greater than that from the Atlan- 
 tic under corresponding parallels; secondly, that 
 the rainfall over the Mediterranean makes up for 
 evaporation less than it does over the Atlantic; 
 and thirdly, supposing these two questions an- 
 swered affirmatively: Are not these sources of loss 
 in the Mediterranean fully covered by the prodigi- 
 ous quantity of fresh water which is poured into it 
 by great rivers and submarine springs? Consider 
 that the water of the Ebro, the Rhine, the Po, the 
 Danube, the Don, the Dnieper, and the Nile, all 
 flow directly or indirectly into the Mediterranean; 
 
68 THE PROBLEMS OP THE DEEP SEA. li 
 
 that the Tolume of fresh water which they pour 
 into it is so enormous that fresh water may some- 
 times be baled up from the surface of the sea off 
 the Delta of the Nile, while the land is not yet in 
 sight; that the water of the Black Sea is half fresh, 
 and that a current of three or four miles an hour 
 constantly streams from it Mediterraneanwards 
 through the Bosphorus; — consider, in addition, 
 that no fewer than ten submarine springs of fresh 
 water are known to burst up in the Mediterranean, 
 some of them so large that Admiral Smyth calls 
 them " subterranean rivers of amazing volume and 
 force "; and it would seem, on the face of the 
 matter, that the sun must have enough to do to 
 keep the level of the Mediterranean down; and 
 that, possibly, we may have to seek for the cause 
 of the small superiority in saline contents of the 
 Mediterranean water in some condition other than 
 solar evaporation. 
 
 Again, if the Gibraltar indraught is the effect 
 of evaporation, why does it go on in winter as well 
 as in summer? 
 
 All these are questions more easily asked than 
 answered; but they must be answered before we 
 can accept the Gibraltar stream as an example 
 of a current produced by indraught with any com- 
 fort. 
 
 The Mediterranean is not included in the Chal- 
 lenger's route, but she will visit one of the most 
 promising and little explored of hydro-graphical 
 
II THE PROBLEMS OF THE DEEP SEA. 69 
 
 regions — the North Pacific, between Polynesia 
 and the Asiatic and American shores; and doubt- 
 less the store of observations upon the currents 
 of this region, which she will accumulate, when 
 compared with what we know of the North Atlan- 
 tic, will throw a powerful light upon the present 
 obscurity of the Gulf-stream problem. 
 
in. 
 
 ON SOME OF THE RES-ULTS OP THE 
 EXPEDITION OF H.M.S. CHALLENGER. 
 
 [1875.] 
 
 In May, 1873, I drew attention * to the im- 
 portant problems connected with the physics and 
 natural history of the sea, to the solution of which 
 there was every reason to hope the cruise of H.M.S. 
 Challenger would furnish important contributions. 
 The expectation then expressed has not been dis- 
 appointed. Eeports to the Admiralty, papers 
 communicated to the Eoyal Society, and large col- 
 lections which have already been sent home, have 
 shown that the Challenger's staff have made ad- 
 mirable use of their great opportunities; and that, 
 on the return of the expedition in 1874, their per- 
 formance will be fully up to the level of their 
 promise. Indeed, I am disposed to go so far as 
 to say, that if nothing more came of the Chal- 
 lenger's expedition than has hitherto been yielded 
 by her exploration of the nature of the sea bottom 
 at great depths, a full scientific equivalent of the 
 
 * See the preceding Essay. 
 70 
 
Ill EXPEDITION OF THE " CHALLBNaER." n 
 
 trouble and expense of her equipment would have 
 been obtained. 
 
 In order to justify this assertion, and yet, at the 
 same time, not to claim more for Professor Wyville 
 Thomson and his colleagues than is their due, I 
 must give a brief history of the observations which 
 have preceded their exploration of this recondite 
 field of research, and endeavour to make clear what 
 was the state of knowledge in December, 1873, 
 and what new facts have been added by the scien- 
 tific staff of the Challenger. So far as I have been 
 able to discover, the first successful attempt to 
 bring up from great depths more of the sea bot- 
 tom than would adhere to a sounding-lead, was 
 made by Sir John Eoss, in the voyage to the Arctic 
 regions which he undertook in 1818. In the Ap- 
 pendix to the narrative of that voyage, there 
 will be found an account of a very ingenious ap- 
 paratus called " clams " — a sort of double scoop — 
 of his own contrivance, which Sir John Ross had 
 made by the ship's armourer; and by which, 
 being in Bafiin's Bay, in 72° 30' N. and 77° 15' W., 
 he succeeded in bringing up from 1,050 fathoms 
 (or 6,300 feet), " several pounds " of a " fine green 
 mud," which formed the bottom of the sea in this 
 region. Captain (now Sir Edward) Sabine, who 
 accompanied Sir John Eoss on this cruise, says of 
 this mud that it was " soft and greenish, and that 
 the lead sunk several feet into it." A similar 
 " fine green mud " was found to compose the sea 
 
72 EXPBDITIOK OP THE "CHALLENGER." iii 
 
 bottom in Davis Straits by Goodsir in 1845. 
 Nothing is certainly known of the exact nature of 
 the mud thus obtained, but we shall see that the 
 mud of the bottom of the Antarctic seas is de- 
 scribed in curiously similar terms by Dr. Hooker, 
 and there is no doubt as to the composition of this 
 deposit. 
 
 In 1850, Captain Penny collected in Assist- 
 ance Bay, in Kingston Bay, and in Melville Bay, 
 which lie between 73° 45' and 74° 40' K, speci- 
 mens of the residuum left by melted surface ice, 
 and of the sea bottom in these localities. Dr. 
 Dickie, of Aberdeen, sent these materials to Ehren- 
 berg, who made out * that the residuum of the 
 melted ice consisted for the most part of the 
 silicious cases of diatomaceous plants, and of the 
 silicious spicula of sponges; while, mixed with 
 these, were a certain number of the equally sili- 
 cious skeletons of those low animal organisms, 
 which were termed Polycistinece by Ehrenberg, but 
 are now known as Eadiolaria. 
 
 In 1856, a very remarkable addition to our 
 knowledge of the nature of the sea bottom in high 
 northern latitudes was made by Professor Bailey 
 of West Point. Lieiitenant Brooke, of the United 
 States Navy, who was employed in surveying the 
 Sea of Kamschatka, had succeeded in obtaining 
 specimens of the sea bottom from greater depths 
 
 * Vrher neve Anschnuiingen des kleinsten ndrdltchen 
 Polarlebens. — Monatsberichte d. K. Akad. Berlin, 1853. 
 
Ill EXPEDITION OF fl^HE "CHALLENGER." Y3 
 
 than any hitherto reached, namely from SjT'OO 
 fathoms (16,200 feet) in 56° 46' N., and 168° 18' 
 E.; and from 1.700 fathoms (10,200 feet) in 60° 
 15' N., and 170° 53' E. On examining these mi- 
 croscopically. Professor Bailey found, as Ehren- 
 berg had done in the case of mud obtained on the 
 opposite side of the Arctic region, that the fine 
 mud was made up of shells of. Diatomacew, of spi- 
 cula of sponges, and of Radiolaria, with a small 
 admixture of mineral matters, but without a trace 
 of any calcareous organisms. 
 
 Still more complete information has been ob- 
 tained concerning the nature of the sea bottom 
 in the cold zone around the south pole. Between 
 the years 1839 and 1843, Sir James Clark Eoss 
 executed his famous Antarctic expedition, in the 
 course of which he penetrated, at two widely dis- 
 tant points of the Antarctic zone, into the high 
 latitudes of the shores of Victoria Land and of 
 Graham's Land, and reached the parallel of 80° S. 
 Sir James Boss was himself a naturalist of no 
 mean acquirements, and Dr. Hooker,* the present 
 President of the Eoyal Society, accompanied him 
 as naturalist to the expedition, so that the obser- 
 vations upon the fauna and flora of the Antarctic 
 regions made during this cruise were sure to have 
 a peculiar value and importance, even had not the 
 attention of the voyagers been particularly direct- 
 ed to the importance of noting the occurrence of 
 * [Now Sir Joseph Hooker. 1894.] 
 
74: EXPEDITION OP THE "CHALLENGER." in 
 
 the minutest forms of animal and vegetable life in 
 the ocean. 
 
 Among the scientific instructions for the voy- 
 age drawn up by a committee of the Royal Society, 
 however, there is a remarkable letter from Von 
 Humboldt to Lord Minto, then First Lord of the 
 Admiralty, in which, among other things, he 
 dwells upon the significance of the researches into 
 the microscopic composition of rocks, and the dis- 
 covery of the great share which microscopic organ- 
 isms take in the formation of the crust of the 
 earth at the present day, made by Ehrenberg in 
 the years 1836-39. Ehrenberg, in fact, had shown 
 that the extensive beds of " rotten-stone " or 
 " Tripoli " which occur in various parts of the 
 world, and notably at Bilin in Bohemia, consisted 
 of accumulations of the silicious cases and skele- 
 tons of DiatomacecB, sponges, and Radiolariaj he 
 had proved that similar deposits were being formed 
 bj' DiatomacecB, in the pools of the Thiergarten 
 in Berlin and elsewhere, and had pointed out that, 
 if it were commercially worth while, rotten-stone 
 might be manufactured by a process of diatom- 
 culture. Observations conducted at Cuxhaven in 
 1839, had revealed the existence, at the surface of 
 the waters of the Baltic, of living Diatoms and 
 Badiolaria of the same species as those which, in 
 a fossil state, constitute extensive rocks of tertiary 
 age at Caltanisetta, Zante, and Oran, on the shores 
 of the Mediterranean. 
 
Ill EXPEDITION OP THE "CHALLENGER." 75 
 
 Moreover, in the fresh-water rotten-stone beds 
 of Eilin, Ehrenherg had traced out the metamor- 
 phosis, effected apparently by the action of perco- 
 lating water, of the primitively loose and friable 
 deposit of organized particles, in which the silex 
 exists in the hydrated or soluble condition. The 
 silex, in fact, undergoes solution and slow redepo- 
 sition, until, in ultimate result, the excessively 
 fine-grained sand, each particle of which is a skele- 
 ton, becomes converted into a dense opaline stone, 
 with only here and there an indication of an or- 
 ganism. 
 
 From the consideration of these facts, Ehren- 
 berg, as early as the year 1839, had arrived at the 
 conclusion that rocks, altogether similar to those 
 which constitute a large part of the crust of the 
 earth, must be forming, at the present day, at the 
 bottom of the sea; and he threw out the sugges- 
 tion that even where no trace of organic structure 
 is to be found in the older rocks, it may have been 
 lost by metamorphosis.* 
 
 The results of the Antarctic exploration, as 
 stated by Dr. Hooker in the " Botany of the Ant- 
 arctic Voyage," and in a paper which he read be- 
 fore the British Association in 1847, are of the 
 
 * Veber die noch jetzt zahXreich lebende Thierarten dor 
 KreideMldung und den Organismus der PolytJialamien. 
 Abhandlungen der Kon. Akad. der Wissenchaften. 1839. 
 Berlin. 1841. I am afraid that this remarkable paper 
 has been somewhat overlooked in the recent discussions 
 of the relation of ancient rocks to modern deposits. 
 
76 EXPEDITION OP THE "CHALLENGER." ill 
 
 greatest importance in connection with these 
 views, and they are so clearly stated in the former 
 work, which is somewhat inaccessible, that I make 
 no apology for quoting them at length — 
 
 "The waters and the ice of the South Polar Ocean 
 were alike found to abound with microscopic vegetables 
 belonging to the order Diatomacew. Though much too 
 small to be discernible by the naked eye, they occurred 
 in such countless myriads as to stain the berg and the 
 pack ice wherever they were washed by the swell of the 
 sea; and, when enclosed in the congealing surface of the 
 water, they imparted to the brash and pancake ice a pale 
 ochreous colour. In the open ocean, northward of the 
 frozen zone, this order, though no doubt almost univer- 
 sally present, generally eludes the search of the natural- 
 ist; except when its species are congregated amongst 
 that mucous scum which is sometimes seen floating on 
 the waves, and of whose real nature we are ignorant; or 
 when the coloured contents of the marine animals who 
 feed on these Algse are examined. To the south, how- 
 ever, of the belt of ice which encircles the globe, between 
 the parallels of 50° and 70° S., and in the waters com- 
 prised between that belt and the highest latitude ever 
 attained by man, this vegetation is very conspicuous, 
 from the contrast between its colour and the white snow 
 and ice in which it is imbedded. Insomuch, that in the 
 eightieth degree, all the surface ice carried along by the 
 currents, the sides of every berg, and the base of the 
 great Victoria Barrier itself, within reach of the swell, 
 were tinged brown, as if the polar waters were charged 
 with oxide of iron. 
 
 "As the majority of these plants consist of very sim- 
 ple vegetable cells, enclosed in indestructible silex (as 
 other Algse are in carbonate of lime), it is obvious that 
 
Ill EXPEDITION OP THE "CHALLENGER." YT 
 
 the death and decomposition of such multitudes must 
 form sedimentary deposits, proportionate in their extent 
 to the length and exposure of the coast against which 
 they are washed, in thickness to the power of such agents 
 as the winds, currents, and sea, which sweep them more 
 energetically to certain positions, and in purity, to the 
 depth of the water and nature of the bottom. Hence 
 we detected their remains along every icebound shore, 
 in the depths of the adjacent ocean, between 80 and 400 
 fathoms. Off Victoria Barrier (a perpendicular wall of 
 ice between one and two hundred feet above the level 
 of the sea) the bottom of the ocean was covered with a 
 stratum of pure white or green mud, composed princi- 
 pally of the silicious shells of the Diatomacew. These, 
 on being put into water, rendered it cloudy like milk, 
 and took many hours to subside. In the very deep 
 water off Victoria and Graham's Land, this mud was 
 particularly pure and fine; but towards the shallow 
 shores there existed a greater or less admixture of dis- 
 integrated rock and sand; so that the organic com- 
 pounds of the bottom frequently bore but a small pro- 
 portion to the inorganic." . . . 
 
 " The universal existence of such an invisible vegeta- 
 tion as that of the Antarctic Ocean, is a truly wonderful 
 fact, and the more from its not being accompanied by 
 plants of a high order. During the years we spent there, 
 I had been accustomed to regard the phenomena of life 
 as differing totally from what obtains throughout all 
 other latitudes, for everything living appeared to be of 
 animal origin. The ocean swarmed with Molliisca, and 
 particularly entomostracous Crustacea, small whales, and 
 porpoises; the sea abounded with penguins and seals, 
 and the air with birds; the animal kingdom was ever 
 present, the larger creatures preying on the smaller, and 
 these again on smaller still; all seemed carnivorous. 
 The herbivorous were not recognised, because feeding 
 
78 EXPEDITION OF THE "CHALLENGER." in 
 
 on a microscopic herbage, of whose true nature I had 
 formed an erroneous impression. It is, therefore, with 
 -no little satisfaction that I now class the Diatomacew 
 with plants, probably maintaining in the South Polar 
 Ocean that balance between the vegetable and the ani- 
 mal kingdoms which prevails over the surface of our 
 globe. Nor is the sustenance and nutrition of the ani- 
 mal kingdom the only function these mikute productions 
 may perform; they may also be the purifiers of the 
 vitiated atmosphere, and thus execute in the Antarctic 
 latitudes the office of our trees and grass turf in the tem- 
 perate regions, and the broad leaves of the palm, &c., in 
 the tropics." . . . 
 
 With respect to the distribution of the Diato- 
 macew, Dr. Hooker remarks: — 
 
 " There is probably no latitude between that of Spitz- 
 bergen and Victoria Land, where some of the species of 
 either country do not exist: Iceland, Britain, the Medi- 
 terranean Sea, North and South America, and the South 
 Sea Islands, all possess Antarctic Diatomacew. The sili- 
 cious coats of species only known living in the waters 
 of the South Polar Ocean, have, during past ages, con- 
 tributed to the formation of rocks; and thus they out- 
 live several successive creations of organized beings. The 
 phonolite stones of the Rhine, and the Tripoli stone, con- 
 tain species identical with what are now contributing to 
 form a sedimentary deposit (and perhaps, at some future 
 period, a bed of rock) extending in one continuous stra- 
 tum for 400 measured miles. I allude to the shores of 
 the Victoria Barrier, along whose coast the soundings 
 examined were invariably charged with diatomaceous re- 
 mains, constituting a bank which stretches 200 miles 
 north from the base of Victoria Barrier, while the aver- 
 age depth of water above it is 300 fathoms, or 1,800 feet. 
 
m EXPEDITION OF THE "CHALLENGER." 79 
 
 Again, some of the Antarctic species hare been detected 
 floating in the atmosphere which overhangs the wide 
 ocean between Africa and America. The knowledge of 
 this marvellous fact we owe to Mr. Darwin, who, when 
 he was at sea off the Cape de Verd Islands, collected an 
 impalpable powder which fell on Captain Fitzroy's ship. 
 He transmitted this dust to Ehrenberg, who ascertained 
 it to consist of the silicious coats, chiefly of American 
 Diatomacew, which were being wafted through the upper 
 region of the air, when some meteorological phenomena 
 checked them in their course and deposited them on the 
 ship and surface of the ocean. 
 
 " The existence of the remains of many species of this 
 order (and amongst them some Antarctic ones) in the 
 volcanic ashes, pumice, and seorise of active and extinct 
 volcanoes (those of the Mediterranean Sea and Ascen- 
 sion Island, for instance) is a fact bearing immediately 
 upon the present subject. Mount Erebus, a volcano 12,- 
 400 feet high, of the first class in dimensions and ener- 
 getic action, rises at once from the ocean in the seventy- 
 eighth degree of south latitude, and abreast of the 
 Diatomacew bank, which reposes in part on its base. 
 Hence it may not appear preposterous to conclude that, 
 as Vesuvius receives the waters of the Mediterranean, 
 with its fish, to eject them by its crater, so the subter- 
 ranean and subaqueous forces which maintain Mount 
 Erebus in activity may occasionally receive organic mat- 
 ter from the bank, and disgorge it, together with those 
 volcanic products, ashes and pumice. 
 
 " Along the shores of Graham's Land and the South 
 Shetland Islands, we have a parallel combination of 
 igneous and aqueous action, accompanied with an equally 
 copious supply of Diatomacew. In the Gulf of Erebus 
 and Terror, fifteen degrees north of Victoria Land, and 
 placed on the opposite side of the globe, the soundings 
 were of a similar nature with those of the Victoria Land 
 
80 EXPEDITION OP THE "CHALLENGER." m 
 
 and Barrier, and the sea and iee as full of Diatomacew. 
 This was not only proved by the deep sea lead, but by 
 the examination of bergs which, once stranded, had 
 floated off and become reversed, exposing an accumu- 
 lation of white friable mud frozen to their bases, which 
 abounded with these vegetable remains." 
 
 The Challenger has explored the Antarctic seas 
 in a region intermediate between those examined 
 by Sir James Eoss's expedition; and the observa- 
 tions made by Dr. Wyville Thomson and his col- 
 leagues in every respect confirm those of Dr. 
 Hooker: — 
 
 " On the 11th of February, lat. 60° 52' S., long. Sp" 
 20' E., and March 3, lat. 53° 55' S., long. 108° 35' E., the 
 sounding instrument came up filled with a very fine 
 cream-coloured paste, which scarcely effervesced with 
 acid, and dried into a very light, impalpable, white pow- 
 der. This, when examined under the microscope was found 
 to consist almost entirely of the frustules of Diatoms, 
 some of them wonderfully perfect in all the details of their 
 ornament, and many of them broken up. The species of 
 Diatoms entering into this deposit have not yet been 
 worked up, but they appear to be referable chiefly to the 
 genera Fragillaria, Coscinodiscus, Chaetoceros, Asterom- 
 plialus, and Dictyocha, with fragments of the separated 
 rods of a singular silicious organism, with which we were 
 unacquainted, and which made up a large proportion of 
 the finer matter of this deposit. Mixed with the Diatoms 
 there were a few small Globigerinw, some of the tests 
 and spicules of Radiolarians, and some sand particles; 
 but these foreign bodies were in too small proportion to 
 affect the formation as consisting practically of Diatoms 
 alone. On the 4th of February, in lat 52° 29' S., long. 
 
Ill EXPEDITION OP THE "CHALLENGER." 81 
 
 71° 36' E., a little to the north of the Heard Islands, the 
 tow-net, dragging a few fathoms below the surface, came 
 up nearly filled with a pale yellow gelatinous mass. This 
 was found to consist entirely of Diatoms of the same spe- 
 cies as those found at the bottom. By far the most 
 abundant was the little bundle of silieious rods, fastened 
 together loosely at one end, separating from one another 
 at the other end, and the whole bundle loosely twisted 
 into a, spindle. The rods are hollow, and contain the 
 characteristic endochrome of the Dlatomaoew. Like the 
 Globigerina ooze, then, which it succeeds to the south- 
 ward in a band apparently of no great width, the ma- 
 terials of this silieious deposit are derived entirely from 
 the surface and intermediate depths. It is somewhat 
 singular that Diatoms did not appear to be in such large 
 numbers on the surface over the Diatom ooze as they 
 were a little further north. This may perhaps be ac- 
 counted for by our not having struck their belt of depth 
 with the tow-net; or it is possible that when we found 
 it on the 11th of February the bottom deposit was 
 really shifted a, little to the south by the warm current, 
 the excessively fine floceulent Mbris of the Diatoms tak- 
 ing a certain time to sink. The belt of Diatom ooze is 
 certainly a little further to the southward in long. 83° E., 
 in the path of the reflux of the Agulhas current, than 
 in long. 108° E. 
 
 " All along the edge of the ice-pack — everywhere, in 
 fact, to the south of the two stations — on the 11th of 
 February on our southward voyage, and on the 3rd of 
 March on our return, we brought up fine sand and gray- 
 ish mud, with small pebbles of quartz and felspar, and 
 small fragments of mica-slate, chlorite-slate, clay-slate, 
 gneiss, and granite. This deposit, I have no doubt, was 
 derived from the surface like the others, but in this case 
 by the melting of icebergs and the precipitation of for- 
 eign matter contained in the ice. 
 193 
 
82 EXPEDITION OP THE "CHALLENGER." m 
 
 " We never saw any trace of gravel or sand, or any 
 material necessarily derived from land, on an iceberg. 
 Several showed vertical or irregular fissures filled with 
 discoloured ice or snow; but, when looked at closely, the 
 discoloration proved usually to be very slight, and the 
 effect at a distance was usually due to the foreign ma- 
 terial filling the fissure reflecting light less perfectly than 
 the general surface of the berg. I conceive that the 
 upper surface of one of these great tabular southern ice- 
 bergs, including by far the greater part of its bulk, and 
 culminating in the portion exposed above the surface of 
 the sea, was formed by the piling up of successive layers 
 of snow during the period, amounting perhaps to several 
 centuries, during which the ice-cap was slowing forcing 
 itself over the low land and out to sea over a long extent 
 of gentle slope, until it reached a depth considerably 
 above 200 fathoms, when the lower specific weight of the 
 ice caused an upward strain which at length overcame the 
 cohesion of the mass, and portions were rent oflf and 
 floated away. If this be the true history of the forma- 
 tion of these icebergs, the absence of all land dibris in 
 the portion exposed above the surface of the sea is readily 
 understood. If any such exist, it must be confined to 
 the lower part of the berg, to that part which has at one 
 time or other moved on the floor of the ice-cap. 
 
 " The Icebergs, when they are first dispersed, float in 
 from 200 to 250 fathoms. When, therefore, they have 
 been drifted to latitudes of 65° or 64° S., the bottom of 
 the berg just reaches the layer at which the temperature 
 of the water is distinctly rising, and it is rapidly melted, 
 and the mud and pebbles with which it is more or less 
 charged are precipitated. That this precipitation takes 
 place all over the area where the icebergs are breaking 
 up, constantly, and to a considerable extent, is evident 
 from the fact of the soundings beilig entirely composed 
 of such deposits; for the Diatoms, Globigerince, and ra- 
 
Ill EXPEDITION OP THE "CHALLENGER." 83 
 
 diolarians are present on the surface in large numbers; 
 and unless the deposit from the Ice were abundant it 
 would soon be covered and masked by a layer of the 
 exuvia of surface organisms." 
 
 The observations which have been detailed 
 leave no doubt that the Antarctic sea bottom, from 
 a little to the soiith of the fiftieth parallel, as far 
 as 80° S., is being covered by a fine deposit of 
 silicious mud, more or less mixed, in some parts, 
 with the ice-borne debris of polar lands and with 
 the ejections of volcanoes. The silicious particles 
 which constitute this mud, are derived, in part, 
 from the diatomaceous plants and radiolarian ani- 
 mals which throng the surface, and, in part, from 
 the spicula of sponges which live at the bottom. 
 The evidence respecting the corresponding Arctic 
 area is less complete, but it is sufficient to justify 
 the conclusion that an essentially similar silicious 
 cap is being formed around the northern pole. 
 
 There is no doubt that the constituent parti- 
 cles of this mud may agglomerate into a dense 
 rock, such as that formed at Oran, on the shores of 
 the Mediterranean, which is made up of similar 
 materials. Moreover, in the case of fresh-water 
 deposits of this kind, it is certain that the action 
 of percolating water may convert the originally 
 soft and friable, fine-grained sandstone into a 
 dense, semi-transparent opaline stone, the sili- 
 cious organized skeletons being dissolved, and the 
 silex re-deposited in an amorphous state. Wheth- 
 
84 EXPEDITION OF THE "CHALLENGER." in 
 
 er such a metamorphosis as this occurs in subma- 
 rine deposits, as well as in those formed in fresh 
 water, does not appear; but there seems no reason 
 to doubt that it may. And hence it may not be 
 hazardous to conclude that very ordinary meta- 
 morphic agencies may convert these polar caps 
 into a form of quartzite. 
 
 In the great intermediate zone, occupying some 
 110° of latitude, which separates the circumpolar 
 Arctic and Antarctic areas of silicious deposit, the 
 Diatoms and Radiolaria of the surface water and 
 the sponges of the bottom do not die out, and, so 
 far as some forms are concerned, do not even 
 appear to diminish in total number; though, on a 
 rough estimate, it would appear that the propor- 
 tion of Radiolaria to Diatoms is much greater than 
 in the colder seas. Nevertheless the composition 
 of the deep-sea mud of this intermediate zone is 
 entirely diiferent from that of the circumpolar 
 regions. 
 
 The first exact information respecting the na- 
 ture of this mud at depths greater than 1,000 
 fathoms was given by Ehrenberg, in the account 
 which he published in the " Monatsberichte " of 
 the Berlin Academy for the year 1853, of the 
 soundings obtained by Lieut. Berryman, of the 
 United States Navy, in the North Atlantic, be- 
 tween Newfoundland and the Azores. 
 
 Observations which confirm those of Ehrenberg 
 
Ill EXPEDITION OF THE "CHALLENGER." 85 
 
 in all essential respects have been made by Profes- 
 sor Bailey, myself, Dr. Wallich, Dr. Carpenter, 
 and Professor Wyville Thomson, in their earlier 
 cruises; and the continuation of the Glohigerina 
 ooze over the South Pacific has been proved by the 
 recent work of the Challenger, by which it is also 
 shown, for the first time, that, in passing from the 
 equator to high southern latitudes, the number 
 and variety of the Foraminifera diminishes, and 
 even the Gldbigerince become dwarfed. And this 
 result, it will be observed, is in entire accordance 
 with the fact already mentioned that, in the sea 
 of Kamschatka, the deep-sea mud was found by 
 Bailey to contain no calcareous organisms. 
 
 Thus, in the whole of the " intermediate zone," 
 the silicious deposit which is being formed there, 
 as elsewhere, by the accumulation of sponge- 
 spicula, Radiolaria, and Diatoms, is obscured -and 
 overpowered by the immensely greater amount of 
 calcareous sediment, which arises from the aggre- 
 gation of the skeletons of dead Foraminifera. 
 The similarity of the deposit, thus composed of a 
 large percentage of carbonate of lime, and a small 
 percentage of silex, to chalk, regarded merely as a 
 kind of rock, which was first pointed out by Eh- 
 renberg,* is now admitted on all hands; nor can 
 
 • The following passages in Ehrenberg's memoir on 
 The Organisms in the Chalk which are still living (1839), 
 are conclusive: — 
 
 " 7. The dawning period of the existing living organic 
 creation, if such a period is distinguishable (which is 
 
86 EXPEDITION OP THE "CHALLENGER." ill 
 
 it be reasonably doubted, that ordinary meta- 
 morphic agencies are competent to convert the 
 " modern chalk " into hard limestone or even into 
 crystalline marble. 
 
 Ehrenberg appears to have taken it for granted 
 that the GloMgerince and other Foraminifera which 
 are found in the deep-sea mud, live at the great 
 depths in which their remains are found; and he 
 supports this opinion by producing evidence that 
 the soft parts of these organisms are preserved, 
 and may be demonstrated by removing the cal- 
 careous matter with dilute acids. In 1857, the 
 evidence for and against this conclusion appeared 
 to me to be insufhcient to warrant a positive con- 
 clusion one way or the other, and I expressed my- 
 
 doubtful), can only be supposed to have existed on the 
 other side of, and below, the chalk formation; and thus, 
 either the chalk, with its widespread and thick beds, 
 must enter into the series of newer formations; or some 
 of the accepted four great geological periods, the quater- 
 nary, tertiary, and secondary formations, contain or- 
 ganisms which still live. It is more probable, in the pro- 
 portion of 3 to 1, that the transition or primary period 
 is not different, but that it is only more difficult to ex- 
 amine and understand, by reason of the gradual and pro- 
 longed chemical decomposition and metamorphosis of 
 many of its organic constituents." 
 
 " 10. By the mass-forming Infusoria and Polytliala- 
 mia, secondary are not distinguishable from tertiary for- 
 mations; and, from what has been said, it is possible 
 that, at this very day, rock masses are forming in the 
 sea, and being raised by volcanic agencies, the constitu- 
 tion of which, on the whole, is altogether similar to that 
 of the chalk. The chalk remains distinguishable by its 
 organic remains as a formation, but not as a kind of 
 rock." 
 
in EXPEDITION OE THE "CHALLBNGBE." 87 
 
 self in my report to the Admiralty on Captain Day- 
 man's soimdings in the following terms :^ 
 
 " When we consider the immense area over which this 
 deposit is spread, the depth at which its formation is 
 going on, and its similarity to chalk, and still more to 
 such rocks as the marls of Caltanisetta, the question, 
 whence are all these organisms derived! becomes one of 
 high scientific interest. 
 
 "Three answers have suggested themselves: — 
 
 " In accordance with the prevalent view of the limita- 
 tion of life to comparatively small depths, it is imagined 
 either: 1, that these organisms have drifted into their 
 present position from shallower waters; or 2, that they 
 habitually live at the surface of the ocean, and only fall 
 down into their present position. 
 
 " 1. I conceive that the first supposition is negatived 
 by the extremely marked zoological peculiarity of the 
 deep-sea fauna. 
 
 " Had the GlobigerincB been drifted into their present 
 position from shallow water, we should find a very large 
 proportion of the characteristic inhabitants of shallow 
 waters mixed with them, and this would the more cer- 
 tainly be the case, as the large Glohigerinm, so abundant 
 in the deep-sea soundings, are, in proportion to their size, 
 more solid and massive than almost any other Foramini- 
 fera. But the fact is that the proportion of other Fora- 
 minifera is exceedingly small, nor have I found as yet, 
 in the deep-sea deposits, any such matters as fragments 
 of molluscous shells, of Echini, &c., which abound in shal- 
 low waters, and are quite as likely to be drifted as the 
 heavy Glohigerinm. Again, the relative proportions of 
 young and fully formed GloMgerinm seem inconsistent 
 with the notion that they have travelled far. And it 
 seems difficult to imagine why, had the deposit been ac- 
 cumulated in this way, Coscinodisci should so almost en- 
 tirely represent the Diatomacew. 
 
88 EXPEDITION OP THE "CHALLENGER." iii 
 
 " 2. The second hypothesis is far more feasible, and is 
 strongly supported by the fact that many Polycistinew 
 [Radiolaria] and Coscinodisci are well known to live 
 at the surface of the ocean. Mr. Macdonald, Assistant- 
 Surgeon of H.M.S. Herald, now in the South-Western 
 Pacific, has lately sent home some very valuable obser- 
 vations on living forms of this kind, met with in the 
 stomachs of oceanic moUusks, and therefore certainly in- 
 habitants of the superficial layer of the ocean. But it 
 is a singular circumstance that only one of the forms 
 figured by Mr. Macdonald is at all like a. Glohigerina, 
 and there are some peculiarities about even this which 
 make me greatly doubt its affinity with that genus. 
 The form, indeed, is not unlike that of a Olohigerina, but 
 it is provided with long radiating processes, of which I 
 have never seen any trace in Globigerina. Did they ex- 
 ist, they might explain what otherwise is a great objec- 
 tion to this view, viz., how is it conceivable that the 
 heavy Globigerina should maintain itself at the surface 
 of the water? 
 
 " If the organic bodies in the deep-sea soundings have 
 neither been drifted, nor have fallen from above, there 
 remains but one alternative — they must have lived and 
 died where they are. 
 
 " Important objections, however, at once suggest 
 themselves to this view. How can animal life be con- 
 ceived to exist under such conditions of light, tempera- 
 ture, pressure, and aeration as must obtain at these vast 
 depths? 
 
 " To this one can only reply that we know for a cer- 
 tainty that even very highly-organized animals do con- 
 tinue to live at a depth of 300 and 400 fathoms, inasmuch 
 as they have been dredged up thenee; and that the dif- 
 ference in the amount of light and heat at 400 and at 
 2,000 fathoms is probably, so to speak, very far less than 
 the difl'erence in complexity of organisation between 
 
in EXPEDITION OP THE "CHALLENGER." 89 
 
 these animals and the humbler Protozoa and Protophyta 
 of the deep-sea soundings. 
 
 " I confess, though as yet far from regarding it proved 
 that the GloMgerince live at these depths, the balance 
 of probabilities seems to me to incline in that direction. 
 And there is one circumstance which weighs strongly in 
 my mind. It may be taken as a law that any genus of 
 animals which is found far back in time is capable of 
 living under a great variety of circumstances as regards 
 light, temperature, and pressure. Now, the genus Globi- 
 gerina is abundantly represented in the cretaceous epoch, 
 and perhaps earlier. 
 
 " I abstain, however, at present from drawing any 
 positive conclusions, preferring rather to await the result 
 of more extended observations." * 
 
 Dr. Wallich, Professor Wyville Thomson, and 
 Dr. Carpenter concluded that the GloMgerince live 
 at the bottom. Dr. Wallich writes in 1862—" By 
 sinking very fine gauze nets to considerable depths, 
 I have repeatedly satisfied myself that Globigerina 
 does not occur in the superficial strata of the 
 ocean."! Moreover, having obtained certain liv- 
 ing star-fish from a depth of 1,360 fathoms, and 
 found their stomachs full of " fresh-looking Olohi- 
 gerincB " and their debris — he adduces this fact in 
 support of his belief that the GlobigerincB live at 
 the bottom. 
 
 On the other hand, Miiller, Haeckel, Major 
 
 * Appendix to Report on Deep-sea Soundings in the 
 Atlantic Ocean, by Lieut.-Commander Joseph Dayman. 
 1857. 
 
 t The North Atlantic Sea-bed, p. 137. 
 
90 EXPEDITION OP THE "CHALLENGER." m 
 
 Owen, Mr. Gwyn Jeffries, and other observers, 
 found that Qlobigerince, with the allied genera 
 Orbulina and Pulvinulina, sometimes occur abund- 
 antly at the surface of the sea, the shells of these 
 pelagic forms being not nnfrequently provided 
 with the long spines noticed by Macdonald; and 
 in 1865 and 1866, Major Owen more especially 
 insisted on the importance of this fact. The re- 
 cent work of the Challenger fully confirms Major 
 Owen's statement. In the paper recently pub- 
 lished in the proceedings of the Royal Society,* 
 from which a quotation has already been made. 
 Professor Wyville Thomson says: — 
 
 " I had formed and expressed a very strong opinion 
 on the matter. It seemed to me that the evidence was 
 conclusive that the Foraminifera which formed the GloH- 
 gerina ooze lived on the bottom, and that the occurrence 
 of individuals on the surface was accidental and excep- 
 tional; but after going into the thing carefully, and con- 
 sidering the mass of evidence which has been accumu- 
 lated by Mr. Murray, I now admit that I was in error; 
 and I agree with him that it may be taken as proved 
 that all the materials of such deposits, with the excep- 
 tion, of course, of the remains of animals which we now 
 know to live at the bottom at all depths, which occur in 
 the deposit as foreign bodies, are derived from the surface. 
 
 " Mr. Murray has combined with a careful examina- 
 tion of the soundings a constant use of the tow-net, usu- 
 
 *" Preliminary Notes on the Nature of the Sea-bottom 
 procured by the soundings of H.M.S. Challenger during 
 her cruise in the Southern Seas, in the early part of the 
 year 1874." — Proceedings of the Royal Society, Nov. 26. 
 1874. 
 
in EXPEDITION OP THE "CHALLBNaER." 91 
 
 ally at the surface, but also at depths of from ten to one 
 hundred fathoms; and he finds the closest relation to 
 exist between the surface fauna of any particular locality 
 and the deposit which is taking place at the bottom. In 
 all seas, from the equator to the polar ice, the tow-net 
 contains Olobigerinw. They are more abundant and of 
 a larger size in warmer seas; several varieties, attaining 
 a large size and presenting marked varietal characters, 
 are found in the intertropical area of the Atlantic. In 
 the latitude of Kerguelen they are less numerous and 
 smaller, while further south they are still more dwarfed, 
 and only one vai-iety, the typical OloHgerina buUoides, 
 is represented. The living Globigerina; from the tow-net 
 are singularly different in appearance from the dead 
 shells we find at the bottom. The shell is clear and 
 transparent, and each of the pores which penetrate it is 
 surrounded by a raised crest, the crest round adjacent 
 pores coalescing into a roughly hexagonal network, so 
 that the pores appear to lie at the bottom of a hexagonal 
 pit. At each angle of this hexagon the crest gives off 
 a delicate flexible calcareous spine, which is sometimes 
 four or five times the diameter of the shell in length. 
 The spines radiate symmetrically from the direction of 
 the centre of each chamber of the shell, and the sheaves 
 of long transparent needles crossing one another in differ- 
 ent directions have a very beautiful effect. The smaller 
 inner chambers of the shell are entirely filled with an 
 orange-yellow granular sarcode; and the large terminal 
 chamber usually contains only a small irregular mass, 
 or two or three small masses run together, of the same 
 yellow sarcode stuck against one side, the remainder of 
 the chamber being empty. No definite arrangement and 
 no approach to structure was observed in the sarcode, 
 and no differentiation, with the exception of round 
 bright-yellow oil-globules, very much like those found 
 in some of the radiolarians, which are scattered, appar- 
 
92 EXPEDITION OP THE "CHALLENGER." m 
 
 ently irregularly, in the sareode. We never have been 
 
 able to detect, in any of the large number of GloWgerinw 
 
 which we have examined, the least trace of pseudopodia, 
 
 or any extension, in any form, of the sareode beyond the 
 
 shell. 
 
 ******** 
 
 " In specimens taken with the tow-net the spines are 
 very usually absent; but that is probably on account of 
 their extreme tenuity; they are broken off by the slight- 
 est touch. In fresh examples from the surface, the dots 
 indicating the origin of the lost spines may almost al- 
 ways be made out with a high power. There are never 
 spines on the GloMgerinw from the bottom, even in the 
 shallowest water." 
 
 There can now be no doubt, therefore, that 
 GlobigerincB live at the top of the sea; but the 
 question may still be raised whether they do not 
 also live at the bottom. In favour of this view, it 
 has been urged that the shells of the Globigerinw 
 of the surface never possess such thick walls as 
 those which are found at the bottom, but I con- 
 fess that I doubt the accuracy of this statement. 
 Again, the occurrence of minute Glohigerince in all 
 stages of development, at the greatest depths, is 
 brought forward as evidence that they live in situ. 
 But considering the extent to which the surface 
 organisms are devoured, without discrimination of 
 young and old, by Salpw and the like, it is not 
 wonderful that shells of all ages should be among 
 the rejectamenta. Nor can the presence of the 
 soft parts of the body in the shells which form 
 the GloUgerina ooze, and the fact, if it be one, that 
 
m EXPEDITION OF THE "CHALLENGER." 93 
 
 animals living at the bottom use them as food, he 
 considered as conclusive evidence that the Glohi- 
 gerince live at the bottom. Such as die at the 
 surface, and even many of those which are swal- 
 lowed by other animals, may retain much of their 
 protoplasmic matter when they reach the depths at 
 which the temperature sinks to 34° or 32° Fahren- 
 heit, where decomposition must become exceeding- 
 ly slow. 
 
 Another consideration appears to me to be in 
 favour of the view that the Glohigerinw and their 
 allies are essentially surface animals. This is the 
 fact brought out by the Challenger's work, that 
 they have a southern limit of distribution, which 
 can hardly depend upon anything but the tem- 
 perature of the surface water. And it is to be 
 remarked that this southern limit occurs at a 
 lower latitude in the Antarctic seas than it does 
 in the North Atlantic. According to Dr. Wallich 
 (" The North Atlantic Sea Bed," p. 157) Gloli- 
 gerina is the prevailing form in the deposits be- 
 tween the Faroe Islands and Iceland, and be- 
 tween Iceland and East Greenland — or, in other 
 words, in a region of the sea-bottom which lies 
 altogether north of the parallel of 60° N.; while 
 in the southern seas, the GloMgerince become 
 dwarfed and almost disappear between 50° and 
 55°. On the other hand, in the sea of Ivams- 
 chatka, the Globigerince have vanished in 56° N., 
 so that the persistence of the Glohigerina ooze in 
 
94 EXPEDITION OP THE "CHALLENGER." in 
 
 high latitudes, in the North Atlantic, would seem 
 to depend on the northward curve of the isother- 
 mals peculiar to this region; and it is difficult to 
 understand how the formation of Glohigerina ooze 
 can be affected by this climatical peculiarity unless 
 it be effected by surface animals. 
 
 Whatever may be the mode of life of the 
 Foraminifera, to which the calcareous element of 
 the deep-sea " chalk " owes its existence, the fact 
 that it is the chief and most widely spread ma- 
 terial of the sea-bottom in the intermediate zone, 
 throughout both the Atlantic and Pacific Oceans, 
 and the Indian Ocean, at depths from a few hun- 
 dred to over two thousand fathoms, is established. 
 But it is not the only extensive deposit which is 
 now taking place. In 1853, Count Pourtales, an 
 officer of the United States Coast Survey, which 
 has done so much for scientific hydrography, ob- 
 served, that the mud forming the sea-bottom at 
 depths of one hundred and fifty fathoms, in 31° 
 33' N., 79° 35' W., off the Coast of Florida, was 
 " a mixture, in about equal proportions, of Gloii- 
 gerince and black sand, probably greensand, as 
 it makes a green mark when crushed on paper." 
 Professor Bailey, examining these grains micro- 
 scopically, found that they were casts of the inte- 
 rior cavities of Foraminifera, consisting of a min- 
 eral known as Glauconite, which is a silicate of 
 iron and alumina. In these casts the minutest 
 cavities and finest tubes in the Poraminifer were 
 
Ill EXPEDITION OF THE "CHALLENGER." 95 
 
 sometimes reproduced in solid counterparts of the 
 glassy mineral; while the calcareous original had 
 been entirely dissolved away. 
 
 Contemporaneously with these observations, 
 the indefatigable Ehrenberg had discovered that 
 the " greensands " of the geologist were largely 
 made up of casts of a similar character, and proved 
 the existence of Foraminifera at a very ancient 
 geological epoch, by discovering such casts in a 
 greensand of Lower Silurian age, which occurs 
 near St. Petersburg. 
 
 Subsequently, Messrs Parker and Jones dis- 
 covered similar casts in process of formation, the 
 original shell not having disappeared, in specimens 
 of the sea-bottom of the Australian seas, brought 
 home by the late Professor Jukes. And the 
 Challenger has observed a deposit of a similar 
 character in the course of the Agulhas current, 
 near the Cape of Good Hope, and in some other 
 localities not yet defined. 
 
 It would appear that this infiltration of Fora- 
 minifera shells with Glauconite does not take place 
 at great depths, but rather in what may be termed 
 a sublittoral region, ranging from a hundred to 
 three hundred fathoms. It cannot be ascribed 
 to any local cause, for it takes place, not only over 
 large areas in the Gulf of Mexico and the Coast of 
 Florida, but in the South Atlantic and in the Pa- 
 cific. But what are the conditions which deter- 
 mine its occurrence, and whence the silex, the 
 
96 EXPEDITION OF THE "CHALLENGER." iii 
 
 iron, and the alumina (with perhaps potash and 
 some other ingredients in small quantity) of which 
 the Glauconite is composed, proceed, is a point on 
 which no light has yet been thrown. For the 
 present we must be content with the fact that, in 
 certain areas of the " intermediate zone," green- 
 sand is replacing and representing the primitively 
 calcareo-silicious ooze. 
 
 The investigation of the deposits which are 
 now being formed in the basin of the Mediterra- 
 nean, by the late Professor Edward Forbes, by 
 Professor Williamson, and more recently by Dr. 
 Carpenter, and a comparison of the results thus 
 obtained with what is known of the surface fauna, 
 have brought to light the remarkable fact, that 
 while the surface and the shallows abound with 
 Foraminifera and other calcareous shelled organ- 
 isms, the indications of life become scanty at 
 depths beyond 500 or 600 fathoms, while almost 
 all traces of it disappear at greater depths, and at 
 1,000 to 3,000 fathoms the bottom is covered with 
 a fine clay. 
 
 Dr. Carpenter has discussed the significance of 
 this remarkable fact, and he is disposed to attri- 
 bute the absence of life at great depths, partly 
 to the absence of any circulation of the water of 
 the Mediterranean at such depths, and partly to 
 the exhaustion of the oxygen of the water by the 
 organic matter contained in the fine clay, which 
 he conceives to be formed by the finest particles 
 
ra EXPEDITION OP THE "CHALLENGER," 97 
 
 of the mud brought down by the rivers which 
 flow into the Mediterranean. 
 
 However this may be, the explanation thus 
 offered of the presence of the fine mud, and of the 
 absence of organisms which ordinarily live at the 
 bottom, does not account for the absence of the 
 skeletons of the organisms which undoubtedly 
 abound at the surface of the Mediterranean; and 
 it would seem to have no application to the re- 
 markable fact discovered by the Challenger, that 
 in the open Atlantic and Pacific Oceans, in the 
 midst of the great intermediate zone, and thou- 
 sands of miles away from the embrouchure of 
 any river, the sea-bottom, at depths approaching 
 to and beyond 3,000 fathoms, no longer consists of 
 Globigerina ooze, but of an excessively fine red 
 clay. 
 
 Professor Thomson gives the following account 
 of this capital discovery: — 
 
 " According to our present experience, the deposit of 
 Globigerina ooze is limited to water of a certain depth, 
 the extreme limit of the pure eharacteristie formation 
 being placed at a depth of somewhere about 2,250 fath- 
 oms. Crossing from these shallower regions occupied by 
 the ooze into deeper soundings, we find, universally, that 
 the calcareous formation gradually passes into, and is 
 finally replaced by, an extremely fine pure clay, which 
 occupies, speaking generally, all depths below 2,500 fath- 
 oms, and consists almost entirely of a silicate of the red 
 oxide of iron and alumina. The transition is very slow, 
 and extends over several hundred fathoms of increasing 
 depth; the shells gradually lose their sharpness of out- 
 193 
 
98 EXPEDITION OF THE "CHALLENGER." iii 
 
 line, and assume a kind of ' rotten ' look and » brownish 
 colour, and become more and more mixed with a fine 
 amorphous red-brown powder, which increases steadily 
 in proportion until the lime has almost entirely disap- 
 peared. This brown matter is in the finest possible state 
 of subdivision, so fine that when, after sifting it to sepa- 
 rate any organisms it might contain, we put it into jars 
 to settle, it remained for several days in suspension, giv- 
 ing the water very much the appearance and colour of 
 chocolate. 
 
 " In indicating the nature of the bottom on the charts, 
 we came, from experience and without any theoretical 
 considerations, to use three terms for soundings in deep 
 water. Two of these, Gl. oz. and r. el., were very defi- 
 nite, and indicated strongly-marked formations, with ap- 
 parently but few characters in common; but we fre- 
 quently got soundings which we could not exactly call 
 ' Globigerina ooze ' or ' red clay,' and before we were fully 
 aware of the nature of these, we were in the habit of 
 indicating them as 'grey ooze' (gr. oz.). We now rec- 
 ognise the ' grey ooze ' as an intermediate stage between 
 the Olobigerina ooze and the red clay; we find that on 
 one side, as it were, of an ideal line, the red clay contains 
 more and more of the material of the calcareous ooze, 
 while on the other, the ooze is mixed with an increasing 
 proportion of ' red clay.' 
 
 " Although we have met with the same phenomenon 
 so frequently, that we were at length able to predict the 
 nature of the bottom from the depth of the soundings 
 with absolute certainty for the Atlantic and the Southern 
 Sea, we had, perhaps, the best opportunity of observing 
 it in our first section across the Atlantic, between Tene- 
 riffe and St. Thomas. The first four stations on this 
 section, at depths from 1,525 to 2,220 fathoms, show 
 Olobigerina ooze. From the last of these, which is about 
 300 miles from Teneriffe, the depth gradually increases 
 
in EXPEDITION OP THE "CHALLENGEE." 99 
 
 to 2,740 fathoms at 500, and 2,950 fathoms at 750 miles 
 from Teneriffe. The bottom in these two soundings 
 might have been called • grey ooze,' for although its na- 
 ture has altered entirely from the GloMgerina ooze, the 
 red clay into which it is rapidly passing still contains a 
 considerable admixture of carbonate of lime. 
 
 " The depth goes on increasing to a distance of 1,150 
 miles from TenerifiFe, when it reaches 3,150 fathoms; 
 there the clay is pure and smooth, and contains scarcely 
 a trace of lime. From this great depth the bottom grad- 
 ually rises, and, with decreasing depth, the grey colour 
 and the calcareous composition of the ooze return. Three 
 soundings in 2,050, 1,900, and 1,950 fathoms on the 
 ' Dolphin Rise ' gave highly characteristic examples of 
 the GloMgerina formation. Passing from the middle pla- 
 teau of the Atlantic into the western trough, with depths 
 a little over 3,000 fathoms, the red clay returned in all 
 its purity; and our last sounding, in 1,420 fathoms, be- 
 fore reaching Sombrero, restored the OloMgerina ooze 
 with its peculiar associated fauna. 
 
 " This section shows also the wide extension and the 
 vast geological Importance of the red clay formation. 
 The total distance from Teneriffe to Sombrero is about 
 2,700 miles. Proceeding from east to west, we have — 
 About 80 miles of volcanic mud and sand. 
 " 350 " GloMgerina ooze, 
 " 1,050 " red clay, 
 " 330 " GloMgerina ooze, 
 " 850 " red clay, 
 " 40 " GloMgerina ooze; 
 giving a total of 1,900 miles of red clay to 720 miles of 
 GloMgerina ooze. 
 
 " The nature and origin of this vast deposit of clay is 
 a question of the very greatest interest; and although I 
 think there can be no doubt that it is in the main solved, 
 yet some matters of detail are still involved in difficulty. 
 
100 EXPEDITION OF THE "CHALLENGER." m 
 
 My first impression was tliat it might be the most mi- 
 nutely divided material, the ultimate sediment produced 
 by the disintegration of the land, by rivers and by the 
 action of the sea on exposed coasts, and held in suspen- 
 sion and distributed by ocean currents, and only making 
 itself manifest in places unoccupied by the Globigerina 
 ooze. Several circumstances seemed, however, to nega- 
 tive this mode of origin. The formation seemed too uni- 
 form; wherever we met with it, it had the same charac- 
 ter, and it only varied in composition in containing less 
 or more carbonate of lime. 
 
 "Again, we were gradually becoming more and more 
 convinced that all the important elements of the Globi- 
 gerina ooze lived on the surface, and it seemed evident 
 that, so long as the condition on the surface remained the 
 same, no alteration of contour at the bottom could possi- 
 bly prevent its accumulation; and the surface conditions 
 in the Mid-Atlantic were very uniform, a moderate cur- 
 rent of a very equal temperature passing continuously 
 over elevations and depressions, and everywhere yielding 
 to the tow-net the ooze-forming Foraminifera in the 
 same proportion. The Mid-Atlantic swarms with pelagic 
 MoUusca, and, in moderate depths, the shells of these are 
 constantly mixed with the Globigerina ooze, sometimes 
 in number sufficient to make up a considerable portion 
 of its bulk. It is clear that these shells must fall in 
 equal number upon the red clay, but scarcely a trace 
 of one of them is ever brought up by the dredge on the 
 red clay area. It might be possible to explain the ab- 
 sence of shell-secreting animals living on the bottom, on 
 the supposition that the nature of the deposit was inju- 
 rious to them; but then the idea of a current sufficiently 
 strong to sweep them away is negatived by the extreme 
 fineness of the sediment which is being laid down; the 
 absence of surface shells appears to be intelligible only 
 on the supposition that they are in some way removed. 
 
Ill EXPEDITION OP THE "CHALLENGER." IQl 
 
 " We conclude, therefore, that the ' red clay ' is not 
 an additional substance introduced from without, and 
 occupying certain depressed regions on account of some 
 law regulating its deposition, but that it is produced by 
 the removal, by some means or other, over these areas, 
 of the carbonate of lime, which forms probably ^bout 98 
 per cent, of the material of the OloMgerina ooze. We 
 can trace, indeed, every successive stage in the removal 
 of the carbonate of lime in descending the slope of the 
 ridge or plateau where the Olobigerlna ooze is forming, 
 to the region of the clay. We find, first, that the shells 
 of pteropods and other surface Mollusca which are con- 
 stantly falling on the bottom, are absent, or, if a few 
 remain, they are brittle and yellow, and evidently de- 
 caying rapidly. These shells of Mollusca decompose more 
 easily and disappear sooner than the smaller, and appar- 
 ently more delicate, shells of rhizopods. The smaller 
 Foraminifera now give way, and are found in lessening 
 proportion to the larger; the coccoliths first lose their 
 thin outer border and then disappear; and the clubs of 
 the rhabdoliths get worn out of shape, and are last seen, 
 under a high power, as infinitely minute cylinders scat- 
 tered over the field. The larger Foraminifera are at- 
 tacked, and instead of being vividly white and delicately 
 sculptured, they become brown and worn, and finally 
 they break up, each according to its fashion; the cham- 
 ber-walls of Globigerina fall into wedge-shaped pieces, 
 which quickly disappear, and a thick rough crust breaks 
 away from the surface of OrbuUna, leaving a thin inner 
 sphere, at first beautifully transparent, but soon becom- 
 ing opaque and crumbling away. 
 
 " In the meantime the proportion of the amorphous 
 ' red clay ' to the calcareous elements of all kinds in- 
 creases, until the latter disappear, with the exception of 
 a few scattered shells of the larger Foraminifera, which 
 are still found even in the most characteristic samples of 
 the ' red clay.' 
 
102 EXPEDITION OF THE "CHALLENGER." ra 
 
 "There seems to be no room left for doubt tbat the 
 red clay is essentially the insoluble residue, the ash, as it 
 were, of the calcareous organisms which form the Globi- 
 gerina ooze, after the calcareous matter has been by 
 some means removed. An ordinary mixture of calcareous 
 Foraminifera with the shells of pteropods, forming a fair 
 sample of Globigerina ooze from near St. Thomas, was 
 carefully washed, and subjected by Mr. Buchanan to the 
 action of weak acid; and he found that there remained 
 after the carbonate of lime had been removed, about 1 per 
 cent, of a reddish mud, consisting of silicia, alumina, and 
 the red '■ oxide of iron. This experiment has been fre- 
 quently repeated with different samples of Globigerina 
 ooze, and always with the result that a small proportion 
 of a red sediment remains, which possesses all the char- 
 acters of the red clay. 
 
 ******** 
 
 " It seems evident from the observations here record- 
 ed, that clay, which we have hitherto looked upon as 
 essentially the product of the disintegration of older 
 rocks, may be, under certain circumstances, an organic 
 formation like chalk; that, as a matter of fact, an area 
 on the surface of the globe, which we have shown to be 
 of vast extent, although we are still far from having 
 ascertained its limits, is being covered by such a deposit 
 at the present day. 
 
 "It is impossible to avoid associating such a forma- 
 tion with the fine, smooth, homogeneous clay and schists, 
 poor in fossils, but showing worm-tubes and tracks, and 
 bunches of doubtful branching things, such as Oldhamia, 
 silicious sponges, and thin-shelled peculiar shrimps. Such 
 formations, more or less metamorphosed, are very fa- 
 miliar, especially to the student of palseozoic geology, 
 and they often attain a vast thickness. One is inclined, 
 from the great resemblance between them in composition 
 and in the general character of the included fauna, to 
 
Ill EXPEDITION OP THE " CHALLENGER." 103 
 
 suspect that these may be organic formations, like the 
 modern red clay of the Atlantic and Southern Sea, accu- 
 mulations of the insoluble ashes of shelled creatures. 
 
 " The dredging in the red clay on the 13th of March 
 was unusually rich. The bag contained examples, those 
 with calcareous shells rather stunted, of most of the char- 
 acteristic deep-water groups of the Southern Sea, includ- 
 ing Umbellularia, Euplectella, Pterocrinus, Brisinga, 
 Ophioglypha, Pourtalesia, and one or two Molliisca. This 
 is, however, very rarely the case. Generally the red clay 
 is barren, or contains only a very small number of forms." 
 
 It must be admitted that it is very difficult, at 
 present, to frame any satisfactory explanation of 
 the mode of origin of this singular deposit of red 
 clay. 
 
 I cannot say that the theory put forward ten- 
 tatively, and with much reservation by Professor 
 Thomson, that the calcareous matter is dissolved 
 out by the relatively fresh water of the deep cur- 
 rents from the Antarctic regions, appears satisfac- 
 tory to me. Nor do I see my way to the accept- 
 ance of the suggestion of Dr. Carpenter, that the 
 red clay is the result of the decomposition of previ- 
 ously-formed greensand. At present there is no 
 evidence that greensand casts are ever formed at 
 great depths; nor has it been proved that Glaucon- 
 ite is decomposable by the agency of water and 
 carbonic acid. 
 
 I think it probable that we shall have to wait 
 some time for a sufficient explanation of the ori- 
 gin of the abyssal red clay, no less than for that 
 
104 EXPEDITION OF THE "CHALLENGEE." iii 
 
 of the sublittoral greensand in the intermediate 
 zone. But the importance of the estabUshment 
 of the fact that these various deposits are being 
 formed in the ocean, at the present day, re- 
 mains the same, whether its rationale be under- 
 stood or not. 
 
 Tor, suppose the globe to be evenly covered 
 with sea, to a depth say of a thousand fathoms — 
 then, whatever might be the mineral matter com- 
 posing the sea-bottom, little or no deposit would 
 be formed upon it, the abrading and denuding ac- 
 tion of water, at such a depth, being exceedingly 
 slight. Next, imagins sponges, Radiolaria, Fora- 
 minifera, and diatomaceous plants, such as those 
 which now exist in the deep-sea, to be introduced: 
 they would be distributed according to the same 
 laws as at present, the sponges (and possibly some 
 of the Foraminifera) covering the bottom, while 
 other Foraminifera, with the Radiolaria and Dia- 
 tomacecB, would increase and multiply in the sur- 
 face waters. In accordance with the existing 
 state of things, the Radiolaria and Diatoms would 
 have a universal distribution, the latter gathering 
 most thickly in the polar regions, while the Fora- 
 minifera would be largely, if not exclusively, eon- 
 fined to the intermediate zone; and, as a conse- 
 quence of this distribution, a bed of " chalk " 
 would begin to form in the intermediate zone, 
 while caps of silieious rock would accumulate on 
 the circumpolar regions. 
 
Ill EXPEDITION OP THE "CHALLENGER." 105 
 
 Suppose, further, that a part of the intermedi- 
 ate area were raised to within two or three hun- 
 dred fathoms of the surface — for anything that we 
 know to the contrary, the change of level might 
 determine the substitution of greensand for the 
 " chalk "; while, on the other hand, if part of the 
 same area were depressed to three thousand 
 fathoms, that change might determine the substi- 
 tution of a different silicate of alumina and iron — 
 namely, clay — for the " chalk " that would other- 
 wise be formed. 
 
 , If the Challenger hypothesis, that the red clay 
 is the residue left by dissolved Foraminiferous 
 skeletons, is correct, then all these deposits alike 
 would be directly, or indirectly, the product of liv- 
 ing organisms. But Just as a silicious deposit may 
 be metamorphosed into opal or quartzite, and 
 chalk into marble, so known metamorphoric agen- 
 cies may metamorphose clay into schist, clay-slate, 
 slate, gneiss, or even granite. And thus, by the 
 agency of the lowest and simplest of organisms, 
 our imaginary globe might be covered with strata, 
 of all the chief kinds of rock of which the known 
 crust of the earth is composed, of indefinite thick- 
 ness and extent. 
 
 The bearing of the conclusions which are now 
 either established or highly probable, respecting 
 the origin of silicious, calcareous, and clayey rocks, 
 and their metamorphic derivatives, upon the arch- 
 
106 EXPEDITION OP THE " CHALLENGER. " ill 
 
 sealogy of the earth, the elucidation of which is 
 the ultimate object of the geologist, is of no small 
 importance. 
 
 A hundred years ago the singular insight of 
 Linnaeus enabled him to say that " fossils are not 
 the children but the parents of rocks,"* and the 
 whole effect of the discoveries made since his time 
 has been to compile a larger and larger comment- 
 ary upon this text. It is, at present, a perfectly 
 tenable hypothesis that all silicious and calcareous 
 rocks are either directly, or indirectly, derived 
 from material which has, at one time or other, 
 formed part of the organized framework of living 
 organisms. Whether the same generalization may 
 be extended to aluminous rocks, depends upon the 
 conclusion to be drawn from the facts respecting 
 the red clay areas brought to light by the Challen- 
 ger. If we accept the view taken by Wyville 
 Thomson and his colleagues — that the red clay 
 is the residuum left after the calcareous matter of 
 the Globigerince ooze has been dissolved away — 
 then clay is as much a product of life as lime- 
 
 * " Petrificata montium calcariorum non filii sed pa- 
 rentes sunt, cum omnis calx oriatur ab animalibus." — 
 Systema Naturw, Ed. xii., t. lii., p. 154. It must be 
 recollected that Linnaeus included silex, as well as lime- 
 stone, under the name of " calx," and that he would prob- 
 ably have arranged Diatoms among animals, as part of 
 " chaos." Ehrenberg quotes another even more pithy 
 passage, which I have not been able to find in any edition 
 of the Systema accessible to me : " Sic lapides ab animali- 
 bus, nee vice versa. Sic rupes saxei non primaevi, sed 
 temporis iilise." 
 
m EXPEDITION OE THE "CHALLENGER." 107 
 
 stone, and all known derivatives of clay may have 
 formed part of animal bodies. 
 
 So long as the Gldbigerinm, actually collected at 
 the surface, have not been demonstrated to con- 
 tain the elements of clay, the Challenger hypo- 
 thesis, as I may term it, must be accepted with re- 
 serve and provisionally, but, at present, I cannot 
 but think that it is more probable than any other 
 suggestion which has been made. 
 
 Accepting it provisionally, we arrive at the 
 remarkable result that all the chief known con- 
 stituents of the crust of the earth may have formed 
 part of living bodies; that they may be the " ash " 
 of protoplasm; that the " rupes saxei " are not 
 only " temporis," but " vitce filiw "j and, conse- 
 quently, that the time during which life has been 
 active on the globe may be indefinitely greater 
 than the period, the commencement of which is 
 marked by the oldest known rocks, whether fos- 
 siliferous or unfossiliferous. 
 
 And thus we are led to see where the solution 
 of a great problem and apparent paradox of geol- 
 ogy may lie. Satisfactory evidence now exists 
 that some animals in the existing world have been 
 derived by a process of gradual modification from 
 pre-existing forms. It is undeniable, for example, 
 that the evidence in favour of the derivation of the 
 horse from the later tertiary Hipparion, and that, 
 of the Hipparion from Anchitherium, is as com- 
 plete and cogent as such evidence can reasonably 
 
108 EXPEDITION OF THE "CHALLENGER." in 
 
 be expected to be; and the further investigations 
 into the history of the tertiary mammalia are 
 pushed, the greater is the accumulation of evi- 
 dence having the same tendency. So far from 
 palaeontology lending no support to the doctrine 
 of evolution — as one sees constantly asserted — 
 that doctrine, if it had no other support, would 
 have been irresistibly forced upon us by the palse- 
 ontological discoveries of the last twenty years. 
 
 If, however, the diverse forms of life which 
 now exist have been produced by the modification 
 of previously existing less divergent forms, the 
 recent and extinct species, taken as a whole, must 
 fall into series which must converge as we go back 
 in time. Hence, if the period represented by the 
 rocks is greater than, or co-extensive with, that 
 during which life has existed, we ought, some- 
 where among the ancient formations to arrive at 
 the point to which all these series converge, or 
 from which, in other words, they have diverged — 
 the primitive undifferentiated protoplasmic living 
 things, whence the two great series of plants and 
 animals have taken their departure. 
 
 But, as a matter of fact, the amount of conver- 
 gence of series, in relation to the time occupied by 
 the deposition of geological formations, is extra- 
 ordinarily small. Of all animals the higher Verie- 
 hrata are the most complex; and among these the 
 carnivores and hoofed animals (Ungulata) are 
 highly differentiated. jSTevertheless, although the 
 
Ill EXPEDITION OF THE "CHALLENGER." 109 
 
 different lines of modification of the Carnivora 
 and those of the Ungulata, respectively, approach 
 one another, and, although each group is repre- 
 sented by less differentiated forms in the older ter- 
 tiary rocks than at the present day, the oldest 
 tertiary rocks do not bring us near the primitive 
 form of either. If, in the same way, the conver- 
 gence of the varied forms of reptiles is measured 
 against the time during which their remains are 
 preserved — which is represented by the whole of 
 the tertiary and mesozoic formations— the amount 
 of that convergence is far smaller than that of the 
 lines of mammals, between the present time and 
 the beginning of the tertiary epoch. And it is a 
 broad fact that, the lower we go in the scale of 
 organization, the fewer signs are there of con- 
 vergence towards the primitive form from whence 
 all must have diverged, if evolution be a fact. 
 Nevertheless, that it is a fact in some cases is 
 proved, and I, for one, have not the courage to 
 suppose that the mode in which some species have 
 taken their origin is different from that in which 
 the rest have originated. 
 
 What, then, has become of all the marine ani- 
 mals which, on the hypothesis of evolution, must 
 have existed in myriads in those seas, wherein the 
 many thousand feet of Cambrian and Laurentian 
 rocks now devoid, or almost devoid, of any trace of 
 life were deposited? 
 
 Sir Charles- Lyell long ago suggested that the 
 
110 EXPEDITION OP THE "CHALLENGER." iii 
 
 azoic character of these ancient formations might 
 be due to the fact that they had undergone exten- 
 sive metamorphosis; and readers of the " Princi- 
 ples of Geology " will be familiar with the ingeni- 
 ous manner in which he contrasts the theory of 
 the Gnome, who is acquainted only with the in- 
 terior of the earth, with those of ordinary philoso- 
 phers, who know only its exterior. 
 
 The metamorphism contemplated by the great 
 modern champion of rational geology is, mainly, 
 that brought about by the exposure of rocks to 
 subterranean heat; and where no such heat could 
 be shown to have operated, his opponents assumed 
 that no metamorphosis could have taken place. 
 But the formation of greensand, and still more 
 that of the " red clay " (if the Challenger hypothe- 
 sis be correct) affords an insight into a new kind of 
 metamorphosis— not igneous, but aqueous — by 
 which the primitive nature of the deposit may be 
 masked as completely as it can be by the agency of 
 heat. And, as Wyville Thomson suggests, in the 
 passage I have quoted above (p. 17), it further, en- 
 ables us to assign a new cause for the occurrence, 
 so puzzling hitherto, of thousands of feet of unfos- 
 siliferous fine-grained schists and slates, in the 
 midst of formations deposited in seas which cer- 
 tainly abounded in life. If the great deposit of 
 "red clay" now forming in the eastern valley of 
 the Atlantic were metamorphosed into slate and 
 then upheaved, it would constitute an " azoic " 
 
HI EXPEDITION OF THE "CHALLENGER." m 
 
 rock of enormous extent. And yet that rock is 
 now forming in the midst of a sea which swarms 
 with living beings, the great majority of which are 
 provided with calcareous or silieious shells and 
 skeletons; and, therefore, are such as, up to this 
 time, we should have termed eminently pre- 
 servable. 
 
 Thus the discoveries made by the Challenger 
 expedition, like all recent advances in our knowl- 
 edge of the phenomena of biology, or of the 
 changes now being effected in the structure of the 
 surface of the earth, are in accordance with, and 
 lend strong support to, that doctrine of Uniform- 
 itarianism, which, fifty years ago was held only by 
 a small minority of English geologists — Lyell, 
 Scrope, and De la Beche — but now, thanks to the 
 long-continued labours of the first two, and main- 
 ly to those of Sir Charles Lyell, has gradually 
 passed from the position of a heresy to that of 
 catholic doctrine. 
 
 Applied within the limits of the time regis- 
 tered by the known fraction of the crust of the 
 earth, I believe that uniformitarianism is unas- 
 sailable. The evidence that, in the enormous 
 lapse of time between the deposition of the lowest 
 Laurentian strata and the present day, the forces 
 which have modified the surface of the crust of 
 the earth were different in kind, or greater in the 
 intensity of their action, than those which are now 
 occupied in the same work, has yet to be produced. 
 
112 EXPEDITION OP THE "CHALLENGER." in 
 
 Such evidence as we possess all tends in the con- 
 trary direction, and is in favour of the same slow 
 and gradual changes occurring then as now. 
 
 But this conclusion in no wise conflicts with 
 the deductions of the physicist from his no less 
 clear and certain data. It may be certain that 
 this globe has cooled down from a condition in 
 which life could not have existed; it may be cer- 
 tain that, in so cooling, its contracting crust must 
 have undergone siidden convulsions, which were 
 to our earthquakes as an earthquake is to the vi- 
 bration caused by the periodical eruption of a 
 Geyser; but in that case, the earth must, like oth- 
 er respectable parents, have sowed her wild oats, 
 and got through her turbulent youth, before we, 
 her children, have any knowledge of her. 
 
 So far as the evidence afforded by the super- 
 ficial crust of the earth goes, the modern geologist 
 can, ex animo, repeat the saying of Hutton, " We 
 find no vestige of a beginning — no prospect of 
 an end." However, he will add, with Hutton, 
 " but in thus tracing back the natural operations 
 which have succeeded each other, and mark to us 
 the course of time past, we come to a period in 
 which we cannot see any further." And if he 
 seek to peer into the darkness of this period, 
 he will welcome the light proffered by physics and 
 mathematics. 
 
IV. 
 YEAST. 
 [1871.] 
 
 It has been known, from time immemorial, 
 that the sweet liquids which may be obtained by 
 expressing the juices of the fruits and stems of 
 various plants, or by steeping malted barley in hot 
 water, or by mixing honey with water — are liable 
 to undergo a series of very singular changes, if 
 freely exposed to the air and left to themselves, in 
 warm weather. However clear and pellucid the 
 liquid may have been when first prepared, however 
 carefully it may have been freed, by straining and 
 filtration, from even the finest visible impurities, 
 it will not remain clear. After a time it will be- 
 come cloudy and turbid; little bubbles will be 
 seen rising to the surface, and their abundance will 
 increase until the liquid hisses as if it were sim- 
 mering on the fire. By degrees, some of the solid 
 particles which produce the turbidity of the liquid 
 194 113 
 
114 YEAST. IV 
 
 collect at its surface into a scum, which is blown 
 up by the emerging air-bubbles into a thick, foamy 
 froth. Another moiety sinks to the bottom, and 
 accumulates as a muddy sediment, or " lees." 
 
 When this action has continued, with more or 
 less violence, for a certain time, it gradually mod- 
 erates. The evolution of bubbles slackens, and 
 finally comes to an end; scum and lees alike set- 
 tle at the bottom, and the fi^iid is once more clear 
 and transparent. But it has acquired properties 
 of which no trace existed in the original liquid. 
 Instead of being a mere sweet fluid, mainly com- 
 posed of sugar and water, the sugar has more or 
 less completely disappeared; and it has acquired 
 that peculiar smell and taste which we call 
 " spirituous." Instead of being devoid of any ob- 
 vious effect upon the animal economy, it has be- 
 come possessed of a very wonderful influence on 
 the nervous system; so that in small doses it ex- 
 hilarates, while in larger it stupefies, and may even 
 destroy life. 
 
 Moreover, if the original fluid is put into a still, 
 and heated moderately, the first and last product 
 of its distillation is simple water; while, when the 
 altered fluid is subjected to the same process, the 
 matter which is first condensed in the receiver is 
 found to be a clear, volatile substance, which is 
 lighter than water, has a pungent taste and smell, 
 possesses the intoxicating powers of the fluid in 
 an eminent degree, and takes fire the moment it 
 
IV YEAST. 115 
 
 is brought in contact with a flame. The Alche- 
 mists called this volatile liquid, which they ob- 
 tained from wine, " spirits of wine," just as they 
 called hydrochloric acid " spirits of salt," and as 
 we, to this day, call refined turpentine " spirits of 
 turpentine." As the " spiritus," or breath, of a 
 man was thought to be the most refined and sub- 
 tle part of him, the intelligent essence of man was 
 also conceived as a sort of breath, or spirit; and, 
 by analogy, the most refined essence of anything 
 was called its " spirit." And thus it has come 
 about that we use the same word for the soul of 
 man and for a glass of gin. 
 
 At the present day, however, we even more 
 commonly use another name for this peculiar 
 liquid — namely, " alcohol," and its origin is not 
 less singular. The Dutch physician. Van Hel- 
 mont, lived in the latter part of the sixteenth and 
 the beginning of the seventeenth century — in the 
 transition period between alchemy and chemistry 
 — and was rather more alchemist than chemist. 
 Appended to his " Opera Omnia," published in 
 1707, there is a very needful " Clavis ad obscuri- 
 orum sensum referendum," in which the following 
 passage occurs: — 
 
 " Alcohol. — Chymicis est liquor aut pulvis summ6 
 subtilisatus, voeabulo Orientalibus quoque, cum primie 
 Habessinis, familiari, quibus cohol speeiatim pulverem 
 impalpabilem ex antimonio pro oeulis tingendis denotat 
 . . . Hodie autem, ob analogiam, quivis pulvis tenerior, 
 ut pulvis oeulorum eaneri summ6 subtilisatus alcoliol 
 
116 YEAST. IV 
 
 audit, baud aliter ac spiritus rectificatlssimi alcolisati 
 dicuntur." 
 
 Similarly, Eobert Boyle speaks of a fine powder 
 as "alcohol"; and, so late as the middle of the 
 last century, the English lexicographer, Nathan 
 Bailey, defines " alcohol " as " the pure substance 
 of anything separated from the more gross, a very 
 fine and impalpable powder, or a very pure, well- 
 rectified spirit." But, by the time of- the publi- 
 cation of Lavoisier's " Traite Elementaire de 
 Chimie," in 1789, the term " alcohol," " alkohol," 
 or " alkool " (for it is spelt in all three ways), 
 which Van Helmont had applied primarily to a 
 fine powder, and only secondarily to spirits of 
 wine, had lost its primary meaning altogether; 
 and, from the end of the last century until now, it 
 has, I believe, been used exclusively as the denota- 
 tion of spirits of wine, and bodies chemically allied 
 to that substance. 
 
 The process which gives rise to alcohol in a 
 saccharine fluid is known to us as "fermenta- 
 tion""; a term based upon the apparent boiling up 
 or " effervescence " of the fermenting liquid, and 
 of Latin origin. 
 
 Our Teutonic cousins call the same process 
 "gahren," "gasen," "goschen," and " gischen "; 
 but, oddly enough, we do not seem to have re- 
 tained their verb or their substantive denoting 
 the action itself, though we do use names identical 
 with, or plainly derived from, theirs for the scum 
 
IV YEAST. 117 
 
 and lees. These are called, in Low German, 
 " gascht " and " gischt "; in Anglo-Saxon 
 " gest," " gist," and " yst," whence our " yeast." 
 Again, in Low German and in Anglo-Saxon there 
 is another name for yeast, having the form 
 " barm," or " heorm "; and, in the Midland Coun- 
 ties, " barm " is the name by which yeast is still 
 best known. In High German, there is a third 
 name for yeast, " hef e," which is not represented 
 in English, so far as I know. 
 
 All these words are said by philologers to be 
 derived from roots expressive of the intestine mo- 
 tion of a fermenting substance. Thus " hefe " 
 is derived from "heben," to raise; "barm" from 
 " beren " or " baren," to bear up; " yeast," " yst," 
 and " gist " have all to do with seething and foam, 
 with " yeasty " waves, and " gusty " breezes. 
 
 The same reference to the swelling up of the 
 fermenting substance is seen in the Gallo-Latin 
 terms " levure " and " leaven." 
 
 It is highly creditable to the ingenuity of our 
 ancestors that the peculiar property of fermented 
 liquids, in virtue of which they " make glad the 
 heart of man," seems to have been known in the 
 remotest periods of which we have any record^ 
 All savages take to alcoholic fluids as if they were 
 to the manner born. Our Vedic forefathers in- 
 toxicated themselves with the juice of the 
 " soma "; Noah, by a not unnatural reaction 
 against a superfluity of water, appears to have 
 
118 YEAST. IV 
 
 taken the earliest practicable opportunity of quali- 
 fying that which he was obliged to drink; and 
 the ghosts of the ancient Egyptians were solaced 
 by pictures of banquets in which the wine-cup 
 passes round, graven on the walls of their tombs. 
 A knowledge of the process of fermentation, there- 
 fore, was in all probability possessed by the pre- 
 historic populations of the globe; and it must have 
 become a matter of great interest even to primaeval 
 wine-bibbers to study the methods by which fer- 
 mented liquids could be surely manufactured. 
 No doubt it was soon discovered that the most 
 certain, as well as the most expeditious, way of 
 making a sweet juice ferment was to add to it a 
 little of the scum, or lees, of another fermenting 
 juice. And it can hardly be questioned that this 
 singular excitation of fermentation in one fluid, by 
 a sort of infection, or inoculation, of a little fer- 
 ment taken from some other fluid, together with 
 the strange swelling, foaming, and hissing of the 
 fermented substance, must have always attracted 
 attention from the more thoughtful. Neverthe- 
 less, the commencement of the scientific analysis 
 of the phenomena dates from a period not earlier 
 than the first half of the seventeenth century. 
 
 At this time, Van Helmont made a first step, 
 by pointing out that the peculiar hissing and bub- 
 bling of a fermented liquid is due, not to the evo- 
 lution of common air (which he, as the inventor 
 of the term " gas " calls " gas ventosum "), but 
 
IV YEAST. 119 
 
 to that of a peculiar kind of air such as is occasion- 
 ally met with in caves, mines, and wells, and which 
 he calls " gas sylvestre." 
 
 But a century elapsed before the nature of this 
 "gas sylvestre," or, as it was afterwards called, 
 " fixed air," was clearly determined, and it was 
 found to be identical with that deadly " choke- 
 damp " by which the lives of those who descend 
 into old wells, or mines, or brewers' vats, are 
 sometimes suddenly ended; and with the poison- 
 ous aeriform fluid which is produced by the com- 
 bustion of charcoal, and now goes by the name of 
 carbonic acid gas. 
 
 During the same time it gradually became 
 evident that the presence of sugar was essential to 
 the production of alcohol and the evolution of 
 carbonic acid gas, which are the two great and 
 conspicuous products of fermentation. And final- 
 ly, in 1787, the Italian chemist, Fabroni, made 
 the capital discovery that the yeast ferment, the 
 presence of which is necessary to fermentation, is 
 what he termed a " vegeto-animal " substance; 
 that is, a body which gives off ammoniacal salts 
 when it is burned, and is, in other ways, similar 
 to the gluten of plants and the albumen and 
 casein of animals. 
 
 These discoveries prepared the way for the 
 illustrious Frenchman, Lavoisier, who first ap- 
 proached the problem of fermentation with a com- 
 plete conception of the nature of the work to 
 
120 YEAST. IV 
 
 be done. The words in which he expresses this 
 conception, in the treatise on elementary chem- 
 istry to which reference has already been made, 
 mark the year 1789 as the commencement of a 
 revolution of not less moment in the world of sci- 
 ence than that which simultaneously burst over 
 the political world, and soon engulfed Lavoisier 
 himself in one of its mad eddies. 
 
 " We may lay it down as an incontestable axiom that, 
 in all the operations of art and nature, nothing is cre- 
 ated; an equal quantity of matter exists both before and 
 after the experiment: the quality and quantity of the 
 elements remain precisely the same, and nothing takes 
 place beyond changes and modifications in the combina- 
 tions of these elements. Upon this principle the whole 
 are of performing chemical experiments depends ; we must 
 always suppose an exact equality between the elements 
 of the body examined and those of the products of its 
 
 " Hence, since from must of grapes we procure alcohol 
 and carbonic acid, I have an undoubted right to suppose 
 that must consists of carbonic acid and alcohol. From 
 these premisses we have two modes of ascertaining what 
 passes during vinous fermentation: either by determin- 
 ing the nature of, and the elements which compose, the 
 fermentable substances; or by accurately examining the 
 products resulting from fermentation; and it is evident 
 that the knowledge of either of these must lead to accu- 
 rate conclusions concerning the nature and composition 
 of the other. From these considerations it became neces- 
 sary accurately to determine the constituent elements of 
 the fermentable substances; and for this purpose I did 
 not make use of the compound juices of fruits, the 
 rigorous analysis of which is perhaps impossible, but 
 
IV YEAST. 121 
 
 made choice of sugar, which is easily analysed, and the 
 nature of which I have already explained. This sub- 
 stance is a true vegetable oxyd, with two bases, composed 
 of hydrogen and carbon, brought to the state of an oxyd 
 by means of a certain proportion of oxygen; and these 
 three elements are combined in such a way that a, very 
 slight force is sufficient to destroy the equilibrium of 
 their connection." 
 
 After giving the details of his analysis of sugar 
 and of the products of fermentation, Lavoisier 
 continues : — 
 
 " The effect of the vinous fermentation upon sugar is 
 thus reduced to the mere separation of its elements into 
 two portions; one part is oxygenated at the expense of 
 the other, so as to form carbonic acid; while the other 
 part, being disoxygenated in favour of the latter, is con- 
 verted into the combustible substance called alkohol; 
 therefore, if it were possible to re-unite alkohol and car- 
 bonic acid together, we ought to form sugar." * 
 
 Thus Lavoisier thought he had demonstrated 
 that the carbonic acid and the alcohol which are 
 produced by the process of fermentation, are 
 equal in weight to the sugar which disappears; 
 but the application of the more refined methods of 
 modern chemistry to the investigation of the pro- 
 ducts of fermentation by Pasteur, in 1860, proved 
 that this is not exactly true, and that there is a 
 deficit of from 5 to 7 per cent, of the sugar which 
 
 * Elements of Chemistry. By M. Lavoisier. Trans- 
 lated by Robert Kerr. Second Edition, 1793 (pp. 186- 
 196). 
 
122 YEAST. IV 
 
 is not covered by the alcohol and carbonic acid 
 evolved. The greater part of this deficit is ac- 
 counted for by the discovery of two substances, 
 glycerine and succinic acid, of the existence of 
 which Lavoisier was unaware, in the fermented 
 liquid. But about IJ per cent, still remains to 
 be made good. According to Pasteur, it has been 
 appropriated by the yeast, but the fact that such 
 appropriation takes place cannot be said to be 
 actually proved. 
 
 However this may be, there can be no doubt 
 that the constituent elements of fully 98 per cent, 
 of the sugar which has vanished during fermenta- 
 tion have simply undergone rearrangement; like 
 the soldiers of a brigade, who at the word of com- 
 mand divide themselves into the independent regi- 
 ments to which they belong. The brigade is 
 sugar, the regiments are carbonic acid, succinic 
 acid, alcohol, and glycerine. 
 
 From the time of Fabroni, onwards, it has been 
 admitted that the agent by which this surprising 
 rearrangement of the particles of the sugar is 
 effected is the yeast. But the first thoroughly 
 conclusive evidence of the necessity of yeast for 
 the fermentation of sugar was furnished by Ap- 
 pert, whose method of preserving perishable arti- 
 cles of food excited so much attention in France 
 at the beginning of this century. Gay-Lussac, in 
 his " Memoire sur la Fermentation," * alludes to 
 • Annales de Chimie, 1810. 
 
IT YEAST, 123 
 
 Appert's method of preserving beer-wort unfer- 
 mented for an indefinite time, by simply boiling 
 the wort and closing the vessel in which the boil- 
 ing fluid is contained, in such a way as thoroughly 
 to exclude air; and he shows that, if a little yeast 
 be introduced into such wort, after it has cooled, 
 the wort at once begins to ferment, even though 
 every precaution be taken to exclude air. And 
 this statement has since received full confirmation 
 from Pasteur. 
 
 On the other hand, Schwann, Schroeder and 
 Dusch, and Pasteur, have amply proved that air 
 may be allowed to have free access to beer-wort, 
 without exciting fermentation, if only efficient pre- 
 cautions are taken to prevent the entry of particles 
 of yeast along with the air. 
 
 Thus, the truth that the fermentation of a 
 simple solution of sugar in water depends upon 
 the presence of yeast, rests upon an unassailable 
 foundation; and the inquiry into the exact nature 
 of the substance which possesses such a wonderful 
 chemical infiuence becomes profoundly inter- 
 esting. 
 
 The first step towards the solution of this 
 problem was made two centuries ago by the patient 
 and painstaking Dutch naturalist, Leeuwenhoek, 
 who in the year 1680 wrote thus: — 
 
 " Saepissime examinavi fermentum cerevisise, semper- 
 que hoc ex globulis per materiam pellucidam fluitantibua, 
 quam cerevlsiam esse censui, constare observavi: vidi 
 
124: YEAST. IT 
 
 etiam evidentissime, unumquemque hujus fermenti glo- 
 bulum denuo ex sex distinctis globulis constare, accurate 
 eidem quantitate et formae, cui globulis sanguinis nostri, 
 respondentibus. 
 
 " Verum talis mihi de horum origine et formatione 
 conceptus formabam; globulis nempe ex quibus farina 
 Tritici, Hordei, Avenae, Fagotritici, se constat aquae calore 
 dissolvi et aquae commisceri; hac, vero aqua, quam cere- 
 visiam vocare licet, refrigescente, multos ex minimis par- 
 ticulis in eerevisia eoadunari, et hoe pacto efiieere parti- 
 culam sive globulum, quae sexta pars est globuli faecis, et 
 iterum sex ex hisce globulis conjungi." * 
 
 Thus Leeuwenhoek discovered that yeast con- 
 sists of globules floating in a fluid; but he thought 
 that they were merely the starchy particles of the 
 grain from which the wort was made, rearranged. 
 He discovered the fact that yeast had a definite 
 structure, biit not the meaning of the fact. A 
 century and a half elapsed, and the investigation 
 of yeast was recommenced almost simultaneously 
 by Cagniard de la Tour in France, and by Schwann 
 ■ and Kiitzing in Germany. The French observer 
 was the first to publish his results; and the sub- 
 ject received at his hands and at those of his col- 
 league, the botanist Turpin, full and satisfactory 
 investigation. 
 
 The main conclusions at which they arrived 
 are these. The globular, or oval, corpuscles which 
 float so thickly in the yeast as to make it muddy, 
 though the largest are not more than one two- 
 
 * Leeuwenhoek, Arcana Naturw Detecta. Ed. Nov., 
 1721. 
 
IV YEAST. 125 
 
 thousandth of an inch in diameter, and the small- 
 est may measure less than one seven-thousandth 
 of an inch, are living organisms. They multiply 
 with great rapidity by giving ofE minute buds, 
 which soon attain the size of their parent, and 
 then either become detached or remain linited, 
 forming the compound globules of which Leeu- 
 wenhoek speaks, though the constancy of their 
 arrangement in sixes existed only in the worthy 
 Dutchman's imagination. 
 
 It was very soon made out that these yeast 
 organisms, to which Turpin gave the name of 
 Torula cerevisice, were more nearly allied to the 
 lower Fungi than to anything else. Indeed Tur- 
 pin, and subsequently Berkeley and Hoffmann, 
 believed that they had traced the development of 
 the Torula into the well-known and very common 
 mould — the Penicillium glaucum. Other observ- 
 ers have not succeeded in verifying these state- 
 ments; and my own observations lead me to be- 
 lieve, that while the connection between Torula 
 and the moulds is a very close one, it is of a dif- 
 ferent nature from that which has been supposed. 
 I have never been able to trace the development 
 of Torula into a true mould; but it is quite easy to 
 prove that species of true mould, such as Peni- 
 cillium, when sown in an appropriate nidus, such 
 as a solution of tartrate of ammonia and yeast-ash, 
 in water, with or without sugar, give rise to 
 Torulce, similar in all respects to T. cerevisice, 
 
126 YEAST. IV 
 
 except that they are, on the average, smaller. 
 Moreover, Bail has observed the development of a 
 Torula larger than T. cerevisice, from a Mucor, a 
 mould allied to Penicillium. 
 
 It follows, therefore, that the Torulce, or organ- 
 isms of yeast, are veritable plants; and conclusive 
 experiments have proved that the power which 
 causes the rearrangement of the molecules of the 
 sugar is intimately connected with the life and 
 growth of the plant. In fact, whatever arrests the 
 vital activity of the plant also prevents it from 
 exciting fermentation. 
 
 Such being the facts with regard to the nature 
 of yeast, and the changes which it effects in 
 sugar, how are they to be accounted for? Before 
 modern chemistry had come into existence, Stahl, 
 stumbling, with the stride of genius, upon the con- 
 ception which lies at the bottom of all modern 
 views of the process, put forward the notion that 
 the ferment, being in a state of internal motion, 
 communicated that motion to the sugar, and thus 
 caused its resolution into new substances. And 
 Lavoisier, as we have seen, adopts substantially 
 the same view. But Fabroni, full of the then 
 novel conception of acids and bases and double 
 decompositions, propounded the hypothesis that 
 sugar is an oxide with two bases, and the ferment 
 a carbonate with two bases; that the carbon of 
 the ferment unites with the oxygen of the sugar, 
 and gives rise to carbonic acid; while the sugar, 
 
IT YEAST. 127 
 
 uniting with the nitrogen of the ferment, pro- 
 duces a new suhstance analogous to opium. This 
 is decomposed by distillation, and gives rise to 
 alcohol. Next, in 1803, Thenard propounded a 
 hypothesis which partakes somewhat of the na- 
 ture of both Stahl's and Fabroni's views. " I do 
 not believe with Lavoisier," he says, " that all the 
 carbonic acid formed proceeds from the sugar. 
 How, in that case, could we conceive the action of 
 the ferment on it? I think that the first portions 
 of the acid are due to a combination of the carbon 
 of the ferment with the oxygen of the sugar, and 
 that it is by carrying off a portion of oxygen from 
 the last that the ferment causes the fermentation 
 to commence — the equilibrium between the prin- 
 ciples of the sugar being disturbed, they combine 
 afresh to form carbonic acid and alcohol." 
 
 The three views here before us may be familiar- 
 ly exemplified by supposing the sugar to be a card- 
 house. According to Stahl, the ferment is some- 
 body who knocks the table, and shakes the card- 
 house down; according to Fabroni, the ferment 
 takes out some cards, but puts others in their 
 places; according to Thenard, the ferment simply 
 takes a card out of the bottom story, the result of 
 which is that all the others fall. 
 
 As chemistry advanced, facts came to light 
 which put a new face upon Stahl's hypothesis, and 
 gave it a safer foundation than it previously pos- 
 sessed. The general nature of these phenomena 
 
128 YEAST. IV 
 
 may be thus stated: — A body A, without giving 
 to, or taking from, another body B, any material 
 particles, causes B to decompose into other sub- 
 stances, C, D, E, the sum of the weights of which 
 is equal to the weight of B, which decomposes. 
 
 Thus, bitter almonds contain two substances, 
 amygdalin and synaptase, which can be extracted, 
 in a separate state, from the bitter almonds. The 
 amygdalin thus obtained, if dissolved in water, 
 undergoes no change; but if a little synaptase be 
 added to the solution, the amygdalin splits up 
 into bitter almond oil, prussic acid, and a kind of 
 sugar. 
 
 A short time after Cagniard de la Tour dis- 
 covered the yeast plant, Liebig, struck with the 
 similarity between this and other such processes 
 and the fermentation of sugar, put forward the 
 hypothesis that yeast contains a substance which 
 acts upon sugar, as synaptase acts upon amygda- 
 lin. And as the synaptase is certainly neither or- 
 ganized nor alive, but a mere chemical substance, 
 Liebig treated Cagniard de la Tour's discovery 
 with no small contempt, and, from that time to 
 the present, has steadily repudiated the notion that 
 the decomposition of the sugar is, in any sense, the 
 result of the vital activity of the Torula. But, 
 though the notion that the Torula is a creature 
 which eats sugar and excretes carbonic acid and 
 alcohol, which is not unjustly ridiculed in the 
 most surprising paper that ever made its appear- 
 
IV YEAST. 129 
 
 anee in a grave scientific journal,* may be un- 
 tenable, the fact that the Torulw are alive, and 
 that yeast does not excite fermentation unless it 
 contains living Torulm, stands fast. Moreover, of 
 late years, the essential participation of living or- 
 ganisms in fermentation other than the alcoholic, 
 has been clearly made out by Pasteur and other 
 chemists. 
 
 However, it may be asked, if there is any neces- 
 sary opposition between the so-called " vital " and 
 the strictly physico-chemical views of fermenta- 
 tion? It is quite possible that the living Torula 
 may excite fermentation in sugar, because it con- 
 stantly produces, as an essential part of its vital 
 manifestations, some substance which acts upon 
 the sugar, just as the synaptase acts upon the 
 amygdalin. Or it may be, that, without the for- 
 mation of any such special substance, the physical 
 condition of the living tissue of the yeast plant is 
 
 * " Das entrathselte Geheimnisa der geistigen Gahrung 
 (Vorlaufige briefliche Mittheilung) " is the title of an 
 anonymous contribution to Wohler and Liebig's Annalen 
 der Pharmacie for 1839, in which a somewhat Rabelaisian 
 imaginary description of the organisation of the " yeast 
 animals " and of the manner in which their functions 
 are performed, is given with a circumstantiality worthy 
 of the author of Gulliver's Travels. As a specimen of 
 the writer's humour, his account of what happens when 
 fermentation comes to an end may suffice. " Sobald nam- 
 lich die Thiere keinen Zucker mehr vorfinden, so fressen 
 sie sich gegenseitig selbst auf, was durch eine eigene 
 Manipulation gesehieht; alles wird verdaut bis auf die 
 Eier, welche unverandert durch den Darmkanal hinein- 
 gehen; man hat zuletzt wieder gahrungsfahige Hefe, 
 namlioh den Saamen der Thiere, der iibrig bleibt." 
 195 
 
130 YEAST. IT 
 
 suiRcient to effect that small disturbance of the 
 equilibrium of the particles of the sugar, which 
 Lavoisier thought sufficient to effect its decompo- 
 sition. 
 
 Platinum in a very fine state of division — 
 known as platinum black, or noir de platine — has 
 the very singular property of causing alcohol to 
 change into acetic acid with great rapidity. The 
 vinegar plant, which is closely allied to the yeast 
 plant, has a similar effect upon dilute alcohol, 
 causing it to absorb the oxygen of the air, and be- 
 come converted into vinegar; and Liebig's emi- 
 nent opponent, Pasteur, who has done so much 
 for the theory and the practice of vinegar-making, 
 himself suggests that in this case — 
 
 " La cause du ph6nom6ne physique qui accompagne la 
 vie de la plante reside dans un 6tat physique propre, ana- 
 logue a celui du noir de platine. Mais il est essentiel de 
 remarquer que eet 6tat physique de la plante est 6troite- 
 ment 116 avee la vie de cette plante." * 
 
 Now, if the vinegar plant gives rise to the oxi- 
 dation of alcohol, on account of its merely physical 
 constitution, it is at any rate possible that the 
 physical constitution of the yeast plant may exert 
 a decomposing influence on sugar. 
 
 But, without presuming to discuss a question 
 which leads us into the very arcana of chemistry, 
 
 * Etudes 8ur les Mycodermes, Comptes-Rendus, liv., 
 1862. 
 
IV YEAST. 131 
 
 the present state of speculation upon the modus 
 operandi of the yeast plant in producing fermenta- 
 tion is represented, on the one hand, by the Stahl- 
 ian doctrine, supported by Liebig, according to 
 which the atoms of the sugar are shaken into new 
 combinations, either directly by the Torulce, or in- 
 directly, by some substance formed by them; and, 
 on the .other hand, by the Thenardian doctrine, 
 supported by Pasteur, according to which the yeast 
 plant assimilates part of the sugar, and, in so do- 
 ing, disturbs the rest, and determines its resolution 
 into the products of fermentation. Perhaps the 
 two views are not so much opposed as they seem at 
 first sight to be. 
 
 But the interest which attaches to the influ- 
 ence of the yeast plants upon the medium in which 
 they live and grow does not arise solely from its 
 bearing upon the theory of fermentation. So 
 long ago as 1838, Turpin compared the Torulw to 
 the ultimate elements of the tissues of animals and 
 plants — " Les organes elementaires de leurs tissus, 
 comparables aux petits vegetaux des levures ordi- 
 naires, sont aussi les decompositeurs des substances 
 qui les environnent." 
 
 Almost at the same time, and, probably, 
 equally guided by his study of yeast, Schwann was 
 engaged in those remarkable investigations into 
 the form and development of the ultimate struc- 
 tural elements of the tissues of animals, which led 
 him to recognise their fundamental identity with 
 
132 YEAST. IV 
 
 the ultimate structural elements of yegetable or- 
 ganisms. 
 
 The yeast plant is a mere sac, or " cell," con- 
 taining a semi-fluid matter, and Schwann's micro- 
 scopic analysis resolved all living organisms, in the 
 long run, into an aggregation of such sacs or cells, 
 variously modified; and tended to show, that all, 
 whatever their ultimate complication, begin their 
 existence in the condition of such simple cells. 
 
 In his famous " Mikroskopische Untersuchun- 
 gen " Schwann speaks of TorulcB as a " cell "; and, 
 in a remarkable note to the passage in which he 
 refers to the yeast plant, Schwann says: — 
 
 " I have been unable to avoid mentioning fermenta- 
 tion, because it is the most fully and exactly known oper- 
 ation of cells, and represents, in the simplest fashion, the 
 process which is repeated by every cell of the living 
 body." 
 
 In other words, Schwann conceives that every 
 cell of the living body exerts an influence on the 
 matter which surrounds and permeates it, anal- 
 ogous to that which a Torula exerts on the sac- 
 charine solution by which it is bathed. A won- 
 derfully suggestive thought, opening up views of 
 the nature of the chemical processes of the living 
 body, which have hardly yet received all the de- 
 velopment of which they are capable. 
 
 Kant defined the special peculiarity of the liv- 
 ing body to be that the parts exist for the sake of 
 the whole, and the whole for the sake of the parts. 
 
IV YEAST. 133 
 
 But when Turpin and Schwann resolved the Uv- 
 ing body into an aggregation of quasi-independent 
 cells, each, like a Torula, leading its own life and 
 having its own laws of growth and development, 
 the aggregation being dominated and kept work- 
 ing towards a definite end only by a certain har- 
 mony among these units, or by the superaddition of 
 a controlling apparatus, such as a nervous system, 
 this conception ceased to be tenable. The cell 
 lives for its own sake, as well as for the sake of 
 the whole organism; and the cells which float in 
 the blood, live at its expense, and profoundly 
 modify it, are almost as much independent organ- 
 isms as the Torulce which float in beer-wort. 
 
 Schwann burdened his enunciation of the " cell 
 theory " with two false suppositions; the one, that 
 the structures he called " nucleus " * and " cell- 
 wall " are essential to a cell; the other, that cells 
 are usually formed independently of other cells; 
 but, in 1839, it was a vast and clear gain to arrive 
 at the conception, that the vital functions of all 
 the higher animals and plants are the resultant of 
 the forces inherent in the innumerable minute 
 cells of which they are composed, and that each of 
 them is, itself, an equivalent of one of the lowest 
 and simplest of independent living beings — the 
 Torula. 
 
 * [Later investigations have thrown an entirely new 
 light upon the structure and the functional importance 
 of the nucleus; and have proved that Schwann did not 
 over-estimate its importance. 1894.] 
 
134 YEAST. vr 
 
 From purely morphological investigations, 
 Turpin and Schwann, as we have seen, arrived at 
 the notion of the fundamental unity of structure 
 of living heings. And, before long the researches 
 of chemists gradually led up to the conception of 
 the fundamental unity of their composition. 
 
 So far back as 1803, Thenard pointed out, in 
 most distinct terms, the important fact that yeast 
 contains a nitrogeneous " animal " substance; and 
 that such a substance is contained in all ferments. 
 Before him, Fabroni and Fourcroy speak of the 
 " vegeto-animal " matter of yeast. In 1844 Mul- 
 der endeavoured to demonstrate that a peculiar 
 substance, which he called " protein," was essen- 
 tially characteristic of living matter. 
 
 In 1846, Pay en writes: — 
 
 " Enfin, une loi sans exception me semble apparaltre 
 dans les faits nombreux que j'ai observes et conduire 4 
 envisager sous un nouveau jour la vie v6g6tale; si je ne 
 m'abuse, tout ce que dans les tissus v6g6taux la vue di- 
 recte oft amplifiee nous permet de diseemer sous la forme 
 de cellules et de vaisseaux, ne reprgsente autre chose que 
 les enveloppes proteetrices, les rfiservoirs et les conduits, a 
 I'aide desquels les corps animes qui les secr6tent et les 
 fagonnent, se logent, puisent et charrient leurs aliments, 
 dfiposent et isolent les matifires excr§t6es." 
 
 And again: — 
 
 "Afin de completer ajourd'hui I'enonce du fait gene- 
 ral, je rappellerai que les corps, dou6 des fonctions ac- 
 complies dans les tissus des plantes, sont formfis des ele- 
 ments qui constituent, en proportion peu variable, les 
 
IV YEAST. 135 
 
 organismes anlmaux; qu'ainsi I'on est conduit a recon- 
 naltre une immense unitg de composition 616mentaire 
 dans tous les corps vivants de la nature." * 
 
 In the year (1846) in which these remarkable 
 passages were published, the eminent German bot- 
 anist, Von Mohl, invented the word " protoplasm," 
 as a name for one portion of those nitrogenous 
 contents of the cells of living plants, the close 
 chemical resemblance of which to the essential 
 constituents of living animals is so strongly in- 
 dicated by Payen. And through the twenty-five 
 years that have passed, since the matter of life was 
 first called protoplasm, a host of investigators, 
 among whom Cohn, Max Schulze, and Kiihne 
 must be named as leaders, have accumulated evi- 
 de'nce, morphological, physiological, and chemical, 
 in favour of that " immense unite de composition 
 elementaire dans tous les corps vivants de la na- 
 ture," into which Payen had, so early, a clear in- 
 sight. 
 
 As far back as 1850, Cohn wrote, apparently 
 without any knowledge of what Payen had said 
 before him: — 
 
 " The protoplasm of the botanist, and the contractile 
 substance and sarcode of the zoologist, must be, if not 
 identical, yet in a high degree analogous substances. 
 Hence, from this point of view, the difference between 
 animals and plants consists in this; that, in the latter, 
 the contractile substance, as a primordial utricle, is en- 
 
 *"M6m. sur les D6veloppements des V6g6taux," &c. 
 — Mi,m. PrisenUes, ix. 1846. 
 
136 YEAST. IV 
 
 closed within an inert cellulose membrane, which permits 
 it only to exhibit an internal motion, expressed by the 
 phenomena of rotation and circulation, while, in the for- 
 mer, it is not so enclosed. The protoplasm in the form 
 of the primordial utricle is, as it were, the animal ele- 
 ment in the plant, but which is imprisoned, and only 
 becomes free in the animal; or, to strip off the metaphor 
 which obscures simple thought, the energy of organic 
 ' vitality which is manifested in movement is especially 
 exhibited by a nitrogenous contractile substance, which 
 in plants is limited and fettered by an inert membrane, 
 in animals not so." * 
 
 In 1868, thinking that an unteehnical state- 
 ment of the views current among the leaders of 
 biological science might be interesting to the gen- 
 eral public, I gave a lecture embodying them in 
 Edinburgh. Those who have not made the mis- 
 take of attempting to approach biology, either by 
 the high a priori road of mere philosophical specu- 
 lation, or by the mere low a posteriori lane ofEered 
 by the tube of a microscope, but have taken the 
 trouble to become acquainted with well-ascer- 
 tained facts and with their history, will not need 
 to be told that in what I had to say " as regards 
 protoplasm " in my lecture " On the Physical 
 Basis of Life " (Vol. I. of these Essays, p. 130), 
 there was nothing new; and, as I hope, nothing 
 that the present state of knowledge does not jus- 
 tify us in believing to be true. Under these cir- 
 cumstances, my surprise may be imagined, when 
 
 * Cohn, Ueber Protococcus pluvialis," in the Vova 
 Acta for 1850. 
 
rv YEAST. 137 
 
 I found, that the mere statement of facts and of 
 views, long familiar to me as part of the common 
 scientific property of Continental workers, raised a 
 sort of storm in this country, not only by exciting 
 the wrath of unscientific persons whose pet pre- 
 judices they seemed to touch, but by giving rise to 
 quite superfluous explosions on the part of some 
 who should have been better informed. 
 
 Dr. Stirling, for example, made my essay the 
 subject of a special critical lecture,* which I have 
 read with much interest, though I confess, the 
 meaning of much of it remains as dark to me as 
 does the " Secret of Hegel " after Dr. Stirling's 
 elaborate revelation of it. Dr. Stirling's method 
 of dealing with the subject is peculiar. "Proto- 
 plasm" is a question of history, so far as it is a 
 name; of fact, so far as it is a thing. Dr. Stirling 
 has not taken the trouble to refer to the original 
 authorities for his history, which is consequently a 
 travesty; and still less has he concerned himself 
 with looking at the facts, but contents himself 
 with taking them also at second-hand. A most 
 amusing example of this fashion of dealing with 
 scientific statements is furnished by Dr. Stirling's 
 remarks upon my account of the protoplasm of the 
 nettle hair. That account was drawn up from 
 careful and often-repeated observation of the facts. 
 Dr. Stirling thinks he is offering a valid criticism, 
 
 * Subsequently published under the title of " As re- 
 gards Protoplasm." 
 
]^38 YEAST. IV 
 
 when he says that my valued friend Professor 
 Strieker gives a somewhat different statement 
 about protoplasm. But why in the world did not 
 this distinguished Hegelian look at a nettle hair 
 for himself, before venturing to speak about the 
 matter at all? Why trouble himself about what 
 either Strieker or I say, when any tyro can see the 
 facts for himself, if he is provided with those not 
 rare articles, a nettle and a microscope? But I 
 suppose this would have been "AufMdrung" — a 
 recurrence to the base common-sense philosophy 
 of the eighteenth century, which liked to see be- 
 fore it believed, and to understand before it criti- 
 cised. Dr. Stirling winds up his paper with the 
 following paragraph:^ 
 
 "In short, the whole position of Mr. Huxley, (1) that 
 all organisms consist alike of the same life-matter, (2) 
 which life-matter is, for its part, due only to chemistry, 
 must be pronounced untenable — nor less untenable (3) 
 the materialism he would found on it." 
 
 The paragraph contains three distinct asser- 
 tions concerning my views, and just the same num- 
 ber of utter misrepresentations of them. That 
 which I have numbered (1) turns on the ambigu- 
 ity of the word " same," for a discussion of which 
 I would refer Dr. Stirling to a great hero of " Auf- 
 Iddrung ," Archbishop Whately; statement num- 
 ber (3) is, in my judgment, absurd, and certainly I 
 have never said anything resembling it; while, as 
 to number (3), one great object of my essay was 
 
IV YEAST. 139 
 
 to show that what is called " materialism " has no 
 sound philosophical basis! 
 
 As we have seen, the study of yeast has led in- 
 vestigators face to face with problems of immense 
 interest in pure chemistry, and in animal and 
 vegetable morphology. Its physiology is not less 
 rich in subjects for inquiry. Take, for example, 
 the singular fact that yeast will increase indefi- 
 nitely when grown in the dark, in water containing 
 only tartrate of ammonia, a small percentage of 
 mineral salts, and sugar. Out of these materials 
 the TorulcB will maniifacture nitrogenous proto- 
 plasm, cellulose, and fatty matters, in any quan- 
 tity, although they are wholly deprived of those 
 rays of the sun, the influence of which is essential 
 to the growth of ordinary plants. There has been 
 a great deal of speculation lately, as to how the liv- 
 ing organisms buried beneath two or three thou- 
 sand fathoms of water, and therefore in all prob- 
 ability almost deprived of light, live. If any of 
 them possess the same powers as yeast (and the 
 same capacity for living without light is exhibited 
 by some other fungi) there would seem to be no 
 difficulty about the matter. 
 
 Of the pathological bearings of the study of 
 yeast, and other such organisms, I have spoken 
 elsewhere. It is certain that, in some animals, 
 devastating epidemics are caused by fungi of low 
 order — similar to those of which Torula is a sort of 
 offshoot. It is certain that such diseases are pro- 
 
140 YEAST. IV 
 
 pagated by contagion and infection, in just the 
 same way as ordinary contagious and infectious 
 diseases are propagated. Of course, it does not 
 follow from this, that all contagious and infectious 
 diseases are caused by organisms of as definite and 
 independent a character as the Torula; but, I 
 think, it does follow that it is prudent and wise to 
 satisfy one's self in each particular case, that the 
 "germ theory" cannot and will not explain the 
 facts, before having recourse to hypotheses which 
 have no equal support from analogy. 
 
V. 
 
 ON THE FOKMATION OF COAL. 
 [1870.] 
 
 The lumps of coal in a coal-scuttle very often 
 have a roughly cubical form. If one of them be 
 picked out and examined with a little care, it will 
 be found that its six sides are not exactly alike. 
 Two opposite sides are comparatively smooth and 
 shining, while the other four are much rougher, 
 and are marked by lines which run parallel with 
 the smooth sides. The coal readily splits along 
 these lines, and the split surfaces thus formed are 
 parallel with the smooth faces. In other words, 
 there is a sort of rough and incomplete stratifica- 
 tion in the lump of coal, as if it were a book, the 
 leaves of which had stuck together very closely. 
 
 Sometimes the faces along which the coal splits 
 are not smooth, but exhibit a thin layer of dull, 
 charred-looking substance, which is known as 
 " mineral charcoal." 
 
 Occasionally one of the faces of a lump of coal 
 will present impressions, which are obviously those 
 of the stem, or leaves, of a plant; but though hard 
 
 141 
 
142 ON THE FORMATION OP COAL. t 
 
 mineral masses of pyrites, and even fine mud, may 
 occur here and there, neither sand nor pebbles 
 are met with. 
 
 When the coal burns, the chief ultimate pro- 
 duets of its combustion are carbonic acid, water, 
 and ammoniacal products, which escape up the 
 chimney; and a greater or less amount of residual 
 earthy salts, which take the form of ash. These 
 products are, to a great extent, such as would re- 
 sult from the burning of so much wood. 
 
 These properties of coal may be made oxit with- 
 out any very refined appliances, but the micro- 
 scope reveals something more. Black and opaque 
 as ordinary coal is, slices of it become transparent 
 if they are cemented in Canada balsam, and 
 rubbed down very thin, in the ordinary way of 
 making thin sections of non-transparent bodies. 
 But as the thin slices, made in this way, are very 
 apt to crack and break into fragments, it is better 
 to employ marine glue as the cementing material. 
 By the use of this substance, slices of considerable 
 size and of extreme thinness and transparency may 
 be obtained.* 
 
 Now let us suppose two such slices to be pre- 
 pared from our lump of coal — one parallel with 
 the bedding, the other perpendicular to it; and 
 let us call the one the horizontal, and the other 
 
 * My assistant in the Museum of Practical Geology, 
 Mr. Newton, invented this excellent method of obtaining 
 thin slices of coal. 
 
r ON THE FORMATION OF COAL. I43 
 
 the vertical, section. The horizontal section will 
 present more or less rounded yellow patches and 
 streaks, scattered irregularly through the dark 
 brown, or blackish, ground substance; while the 
 vertical section will exhibit mere elongated bars 
 and granules of the same yellow materials, dis- 
 posed in lines which correspond, roughly, with 
 the general direction of the bedding of the coal. 
 
 This is the microscopic structure of an ordi- 
 nary piece of coal. But if a great series of coals, 
 from different localities and seams, or even from 
 different parts of the same seam, be examined, 
 this structure will be found to vary in two direc- 
 tions. In the anthracitic, or stone-coals, which 
 burn like coke, the yellow matter diminishes, and 
 the ground substance becomes more predominant, 
 blacker, and more opaque, until it becomes im- 
 possible to grind a section thin enough to be trans- 
 lucent; while, on the other hand, in such as the 
 " Better-Bed " coal of the neighbourhood of Brad- 
 ford, which burns with much flame, the coal is of 
 a far lighter colour, and transparent sections are 
 very easily obtained. In the browner parts of this 
 coal, sharp eyes will readily detect multitudes of 
 curious little coin-shaped bodies, of a yellowish 
 brown colour, embedded in the dark brown ground 
 substance. On the average, these little brow:n 
 bodies may have a diameter of about one-twentieth 
 of an inch. They lie with their flat surfaces near- 
 ly parallel with the two smooth faces of the block 
 
144 ON THE FORMATION OP COAL. T 
 
 in which they are contained; and, on one side of 
 each, there may be discerned a figure, consisting 
 of three straight linear marks, which radiate from 
 the centre of the disk, but do not quite reach its 
 circumference. In the horizontal section these 
 disks are often converted into more or less com- 
 plete rings; while in the vertical sections they 
 appear like thick hoops, the sides of which have 
 been pressed together. The disks are, therefore, 
 flattened bags; and favourable sections show that 
 the three-rayed marking is the expression of three 
 clefts, which penetrate one wall of the bag. 
 
 The sides of the bags are sometimes closely ap- 
 proximated; but, when the bags are less flattened, 
 their cavities are, usually, filled with numerous, 
 irregularly rounded, hollow bodies, having the 
 same kind of wall as the large ones, but not more 
 than one seven-hundredth of an inch in diameter. 
 
 In favourable specimens, again, almost the 
 whole ground substance appears to be made up 
 of similar bodies — more or less carbonized or 
 blackened — and, in these, there can be no doubt 
 that, with the exception of patches of mineral 
 charcoal, here and there, the whole mass of the 
 coal is made up of an accumulation of the larger 
 and of the smaller sacs. 
 
 But, in one and the same slice, every transition 
 can be observed from this structure to that which 
 has been described as characteristic of ordinary 
 coal. The latter appears to rise out of the former. 
 
V ON THE FORMATION OF COAL. I45 
 
 by the breaking up and increasing carbonization 
 of the larger and the smaller sacs. And, in the 
 anthracitie coals, this process appears to have gone 
 to such a length, as to destroy the original struc- 
 ture altogether, and to replace it by a completely 
 carbonized substance. 
 
 Thus coal may be said, speaking broadly, to be 
 composed of two constituents: firstly, mineral 
 charcoal; and, secondly, coal proper. The nature 
 of the mineral charcoal has long since been de- 
 termined. Its structure shows it to consist of the 
 remains of the stems and leaves of plants, reduced 
 a little more than their carbon. Again, some of 
 the coal is made up of the crushed and flattened 
 bark, or outer coat, of the stems of plants, the in- 
 ner wood of which has completely decayed away. 
 But what I may term the " saccular matter " of 
 the coal, which, either in its primary or in its de- 
 graded form, constitutes by far the greater part of 
 all the bituminous coals I have examined, is cer- 
 tainly not mineral charcoal; nor is its structure 
 that of any stem or leaf. Hence its real nature is, 
 at first, by no means apparent, and has been the 
 subject of much discussion. 
 
 The first person who threw any light upon the 
 problem, as far as I have been able to discover, 
 was the well-known geologist. Professor Morris. 
 It is now thirty-four years since he carefully de- 
 scribed and figured the coin-shaped bodies, or 
 
 larger sacs, as I have called them, in a note ap- 
 196 
 
146 ON THE FORMATION OF COAL. v 
 
 pended to the famous paper " On the Coalbrook- 
 dale Coal-Field," published at that time, by the 
 present President of the Geological Society, Mr. 
 Prestwich. "With much sagacity. Professor Mor- 
 ris divined the real nature of these bodies, and 
 boldly affirmed them to be the spore-cases of a 
 plant allied to the living club-mosses. 
 
 But discovery sometimes makes a long halt; 
 and it is only a few years since Mr. Carruthers de- 
 termined the plant (or rather one of the plants) 
 which produces these spore-cases, by finding the 
 discoidal sacs still adherent to the leaves of the 
 fossilized cone which produced them. He gave 
 the name of Flemingites gracilis to the plant of 
 which the cones form a part. The branches and 
 stem of this plant are not yet certainly known, but 
 there is no sort of doubt that it was closely allied 
 to the Lepidodendron, the remains of which abound 
 in the coal formation. The Lepidodendra were 
 shrubs and trees which put one more in mind of 
 an Araucaria than of any other familiar plant; 
 and the ends of the fruiting branches were ter- 
 minated by cones, or catkins, somewhat like the 
 bodies so named in a fir, or a willow. These coni- 
 cal fruits, however, did not produce seeds; but the 
 leaves of which they were composed bore upon 
 their surfaces sacs full of spores or sporangia, such 
 as those one sees on the under surface of a bracken 
 leaf. Now, it is these sporangia of the Lepidoden- 
 droid plant Flemingites which were identified by 
 
V ON THE FORMATION OF COAL. 147 
 
 Mr. Carruthers with the free sporangia described 
 by Professor Morris, which are the same as the 
 large sacs of which I have spoken. And, more 
 than this, there is no doubt that the small sacs are 
 the spores, which were originally contained in the 
 sporangia. 
 
 The living club-mosses are, for the most part, 
 insignificant and creeping herbs, which, superfi- 
 cially, very closely resemble true mosses, and none 
 of them reach more than two or three feet in 
 height. But, in their essential structure, they very 
 closely resemble the earliest Lepidodendroid trees 
 of the coal: their stems and leaves are similar; so 
 are their cones; and no less like are the sporangia 
 and spores; while even in their size, the spores of 
 the Lepidodendron and those of the existing Lyco- 
 podium, or club-moss, very closely approach one 
 another. 
 
 Thus, the singular conclusion is forced upon 
 us, that the greater and the smaller sacs of the 
 " Better-Bed " and other coals, in which the primi- 
 tive structure is well preserved, are simply the 
 sporangia and spores of certain plants, many of 
 which were closely allied to the existing club- 
 mosses. And if, as I believe, it can be demon- 
 strated that ordinary coal is nothing but " saccu- 
 lar " coal which has undergone a certain amount 
 of that alteration which, if continued, would con- 
 vert it into anthracite; then, the conclusion is ob- 
 vious, that the great mass of the coal we burn is 
 
148 ON THE FORMATION OP COAL. v 
 
 the result of the accumulation of the spores and 
 spore-cases of plants, other parts of which have 
 furnished the carbonized stems and the mineral 
 charcoal, or have left their impressions on the sur- 
 faces of the layer. 
 
 Of the multitudinous speculations which, at 
 various times, have been entertained respecting 
 the origin and mode of formation of coal, several 
 appear to be negatived, and put out of court, by 
 the structural facts the significance of which I 
 have endeavoured to explain. These facts, for 
 example, do not permit us to suppose that coal is 
 an accumulation of peaty matter, as some have 
 held. 
 
 Again, the late Professor Quekett was one of 
 the first observers who gave a correct description 
 of what I have termed the " saccular " structure 
 of coal; and, rightly perceiving that this structure 
 was something quite different from that of any 
 known plant, he imagined that it proceeded from 
 some extinct vegetable organism which was pecu- 
 liarly abundant amongst the coal-forming plants. 
 But this explanation is at once shown to be un- 
 tenable when the smaller and the larger sacs are 
 proved to be spores or sporangia. 
 
 Some, once more, have imagined that coal was 
 of submarine origin; and though the notion is 
 amply and easily refuted by other considerations, 
 it may be worth while to remark, that it is impos- 
 sible to comprehend how a mass of light and resin- 
 
V ON THE FORMATION OP COAL. 149 
 
 ous spores should have reached the bottom of the 
 sea, or should have stopped in that position if they 
 had got there. 
 
 At the same time, it is proper to remark that I 
 do not presume to suggest that all coal must needs 
 have the same structure; or that there may not 
 be coals in which the proportions of wood and 
 spores, or spore-cases, are very different from those 
 which I have examined. All I repeat is, that none 
 of the coals which have come under my notice 
 have enabled me to observe such a difference. 
 But, according to Principal Dawson, who has so 
 sedulously examined the fossil remains of plants in 
 North America, it is otherwise with the vast accu- 
 mulations of coal in that country. 
 
 " The true eoal," says Dx. Dawson, " consists princi- 
 pally of the flattened bark of Sigillarioid and otlier trees, 
 intermixed with leaves of Ferns and Cordaites, and other 
 herbaceous debris, and with fragments of decayed wood, 
 constituting ' mineral charcoal,' all these materials hav- 
 ing manifestly alike grown and accumulated where we 
 find them." * 
 
 When I had the pleasure of seeing Principal 
 Dawson in London last summer, I showed him 
 my sections of coal, and begged him to re-examine 
 some of the American coals on his return to Can- 
 ada, with an eye to the presence of spores and 
 sporangia, such as I was able to show him in our 
 English and Scotch coals. He has been good 
 * Acadian Geology, 2nd edition, p. 138. 
 
150 ON THE FORMATION OF COAL. v 
 
 enough to do so; and in a letter dated September 
 26th, 1870, he informs me that— 
 
 " Indications of spore-cases are rare, except in certain 
 coarse shaly coals and portions of coals, and in the roofs 
 of the seams. The most marked case I have yet met with 
 is the shaly coal referred to as containing Sporangites in 
 my paper on the conditions of accumulation of coal 
 (' Journal of the Geological Society,' vol. xxii. pp. 115, 
 139, and 165). The purer coals certainly consist prin- 
 cipally of cubical tissues with some true woody matter, 
 and the spore-cases, &c., are chiefly in the coarse and 
 shaly layers. This is my old doctrine in my two papers 
 in the ' Journal of the Geological Society,' and I see 
 nothing to modify it. Your observations, however, make 
 it probable that the frequent clear spots in the eannels 
 are spore-cases." 
 
 Dr. Dawson's results are the more remarkable, 
 as the numerous specimens of British coal, from 
 various localities, which I have examined, tell one 
 tale as to the predominance of the spore and spo- 
 rangium element in their composition; and as it is 
 exactly in the finest and purest coals, such as the 
 " Better-Bed " coal of Lowmoor, that the spores 
 and sporangia obviously constitute almost the en- 
 tire mass of the deposit. 
 
 Coal, such as that which has been described, is 
 always found in sheets, or " seams," varying from 
 a fraction of an inch to many feet in thickness, 
 enclosed in the substance of the earth at very 
 various depths, between beds of rock of different 
 kinds. As a rule, every seam of coal rests upon a 
 
V OK -THE FORMATION OP COAL. 151 
 
 thicker, or thinner, bed of clay, which is known 
 as " under-clay." These alternations of beds of 
 coal, clay, and rock may be repeated many times, 
 and are known as the "coal-measures"; and in 
 some regions, as in South Wales and in Note 
 Scotia, the coal-measures attain a thickness of 
 twelve or fourteen thousand feet, and enclose 
 eighty or a hundred seams of coal, each with its 
 under-clay, and separated from those above and 
 below by beds of sandstone and shale. 
 
 The position of the beds which constitute the 
 coal-measures is infinitely diverse. Sometimes 
 they are tilted up vertically, sometimes they are 
 horizontal, sometimes curved into great basins; 
 sometimes they come to the surface, sometimes 
 they are covered up by thousands of feet of rock. 
 But, whatever their present position, there is 
 abundant and conclusive evidence that every 
 under-clay was once a surface soil. ISTot only do 
 carbonized root-fibres frequently abound in these 
 under-clays; but the stools of trees, the trunks of 
 which are broken off and confounded with the 
 bed of coal, have been repeatedly found passing 
 into radiating roots, still embedded in the under- 
 clay. On many parts of the coast of England, 
 what are commonly known as " submarine for- 
 ests " are to be seen at low water. They consist, 
 for the most part, of short stools of oak, beech, and 
 fir trees, still fixed by their long roots in the bed 
 of blue clay in which they originally grew. If 
 
152 ON THE FORMATION OF COAL. v 
 
 one of these submarine forest beds should be grad- 
 ually depressed and covered up by new deposits, it 
 would present just the same characters as an 
 under-clay of the coal, if the Sigillaria and Lepi- 
 dodendron of the ancient world were substituted 
 for the oak, or the beech, of our own times. 
 
 In a tropical forest, at the present day, the 
 trunks of fallen trees, and the stools of such trees 
 as may have been broken by the violence of storms, 
 remain entire for but a short time. Contrary to 
 what might be expected, the dense wood of the 
 tree decays, and suffers from the ravages of in- 
 sects, more swiftly than the bark. And the travel- 
 ler, setting his foot on a prostrate trunk, finds that 
 it is a mere shell, which breaks under his weight, 
 and lands his foot amidst the insects or the rep- 
 tiles, which have sought food or refuge within. 
 
 The trees of the coal-forest present parallel 
 conditions. When the fallen trunks which have 
 entered into the composition of the bed of coal are 
 identifiable, they are mere double shells of 
 bark, flattened together in consequence of the de- 
 struction of the woody core; and Sir Charles Lyell 
 and Principal Dawson discovered, in the hollow 
 stools of coal trees of Nova Scotia, the remains of 
 snails, millipedes, and salamander-like creatures, 
 embedded in a deposit of a diiferent character 
 from that which surrounded the exterior of the 
 trees. Thus, in endeavouring to comprehend the 
 formation of a seam of coal, we must try to picture 
 
V ON THE FORMATION OF COAL. 153 
 
 to ourselves a thick forest, formed for the most 
 part of trees like gigantic club-mosses, mares'- 
 tails, and tree-ferns, with here and there some 
 that had more resemblance to our existing yews 
 and fir-trees. "We must suppose that, as the sea- 
 sons rolled by, the plants grew and developed their 
 spores and seeds; that they shed these in enormous 
 quantities, which accumulated on the ground be- 
 neath; and that, every now and then, they added 
 a dead frond or leaf; or, at longer intervals, a rot- 
 ten branch, or a dead trunk, to the mass. 
 
 A certain proportion of the spores and seeds no 
 doubt fulfilled their obvious function, and, carried 
 by the wind to unoccupied regions, extended the 
 limits of the forest; many might be washed away 
 by rain into streams, and be lost; but a large por- 
 tion must have remained, to accumulate like 
 beech-mast, or acorns, beneath the trees of a mod- 
 ern forest. 
 
 But, in this case, it may be asked, why does 
 not our English coal consist of stems and leaves 
 to a much greater extent than it does? What is 
 the reason of the predominance of the spores and 
 spore-cases in it? 
 
 A ready answer to this question is afforded by 
 the study of a living full-grown club-moss. Shake 
 it upon a piece of paper, and it emits a cloud of 
 fine dust, which falls over the paper, and is the 
 well-known Lycopodium powder. Now this pow- 
 der used to be, and I believe still is, employed for 
 
154 ON THE FORMATION OP COAL. v 
 
 two objects which seem, at first sight, to have no 
 particular connection with one another. It is, or 
 was, employed in making lightning, and in making 
 pills. The coats of the spores contain so much 
 resinous matter, that a pinch of Lycopodium pow- 
 der, thrown through the flame of a candle, burns 
 with an instantaneous flash, which has long done 
 duty for lightning on the stage. And the same 
 character makes it a capital coating for pills; for 
 the resinous powder prevents the drug from being 
 wetted by the saliva, and thus bars the nauseous 
 flavour from the sensitive papillae of the tongue. 
 
 But this resinous matter, which lies in the 
 walls of the spores and sporangia, is a substance 
 not easily altered by air and water, and hence tends 
 to preserve these bodies, just as the bituminized 
 cerecloth preserves an Egyptian mummy; while 
 on the other hand, the merely woody stem and 
 leaves tend to rot, as fast as the wood of the mum- 
 my's coffin has rotted. Thus the mixed heap of 
 spores, leaves, and stems in the coal-forest would 
 be persistently searched by the long-continued ac- 
 tion of air and rain; the leaves and stems would 
 gradually be reduced to little but their carbon, or, 
 in other words, to the condition of mineral char- 
 coal in which we find them; while the spores and 
 sporangia remained as a comparatively unaltered 
 and compact residuum. 
 
 There is, indeed, tolerably clear evidence that 
 the coal must, under some circumstances, have 
 
T ON THE FORMATION OP COAL. I55 
 
 been converted into a substance hard enough to 
 be rolled into pebbles, while it yet lay at the sur- 
 face of the earth; for in some seams of coal, the 
 courses of rivulets, which must have been living 
 water, while the stratum in which their remains 
 are found was still at the surface, have been ob- 
 served to contain rolled pebbles of the very coal 
 through which the stream has cut its way. 
 
 The structural facts are such as to leave no 
 alternative but to adopt the view of the origin of 
 such coal as I have described, which has just been 
 stated; but, happily, the process is not without 
 analogy at the present day. I possess a specimen 
 of what is called " white coal " from Australia. 
 It is an inflammable material, burning with a 
 bright flame, and having much the consistence 
 and appearance of oat-cake, which, I am informed, 
 covers a considerable area. It consists, almost 
 entirely, of a compacted mass of spores and spore- 
 cases. But the fine particles of blown sand which 
 are scattered through it, show that it must have 
 accumulated, subaerially, upon the surface of a 
 soil covered by a forest of cryptogamous plants, 
 probably tree-ferns. 
 
 As regards this important point of the subae- 
 rial region of coal, I am glad to find myself in en- 
 tire accordance with Principal Dawson, who bases 
 his conclusions upon other, but no less forcible, 
 considerations. In a passage, which is the con- 
 tinuation of that already cited, he writes: — 
 
156 ON THE POJRMATION OP COAL. v 
 
 " (3) The mieroseopieal structure and chemical com- 
 position of the beds of eannel coal and earthy bitumen, 
 and of the more highly bituminous and carbonaceous 
 shale, show them to have been of the nature of the fine 
 vegetable mud which accumulates in the ponds and shal- 
 low lakes of modern swamps. When such fine vegetable 
 sediment is mixed, as is often the ease, with clay, it be- 
 comes similar to the bituminous limestone and calcareo- 
 bituminous shales of the coal-measures. (4) A few of the 
 under-clays, which support beds of coal, are of the nature 
 of the vegetable mud above referred to; but the greater 
 part are argillo-arenaceous in composition, with little 
 vegetable matter, and bleached by the drainage from 
 them of water containing the products of vegetable de- 
 cay. They are, in short, loamy or clay soils, and must 
 have been sufficiently above water to admit of drainage. 
 The absence of sulphurets, and the occurrence of car- 
 bonate of iron in connection with them, prove that, when 
 they existed as soils, rain-water, and not sea-water, per- 
 colated them. (5) The coal and the fossil forests present 
 many evidences of subaerial conditions. Most of the 
 erect and prostrate trees had become hollow shells of 
 bark before they were finally embedded, and their wood 
 had broken into cubical pieces of mineral charcoal. 
 Land-snails and galley-worms (Xylobitis) crept into them, 
 and they became dens, or traps, for reptiles. Large quan- 
 tities of mineral charcoal occur on the surface of all the 
 large beds of coal. None of these appearances could have 
 been produced by subaqueous action. (C) Though the 
 roots of the Sigillarla bear more resemblance to the 
 rhizomes of certain aquatic plants; yet, structurally, 
 they are absolutely identical with the roots of Cycads, 
 which the stems also resemble. Further, the SUjillariw 
 grew on the same soils which supported Conifers, Lepiflo- 
 dendra, Cordaites, and Ferns — plants which could not 
 have grown in water. Again, with the exception perhaps 
 
V ON THE- FORMATION OF COAL. 15Y 
 
 of some Pinnulariw and Asterophyllites, there is a re- 
 markable absence from the coal measures of any form of 
 properly aquatic vegetation. (7) The occurrence of ma- 
 rine, or brackish-water animals, in the roofs of coal-beds, 
 or even in the coal itself, affords no evidence of subaque- 
 ous accumulation, since the same thing occurs in the 
 ease of modern submarine forests. For these and other 
 reasons, some of which are more fully stated in the 
 papers already referred to, while I admit that the areas 
 of coal accumulation were frequently submerged, I must 
 maintain that the true coal is a subaiirial accumulation 
 by vegetable growth on soils, wet and swampy it is true, 
 but not submerged." 
 
 I am almost disposed to doubt whether it is 
 necessary to make the concession of " wet and 
 swampy "; otherwise, there is nothing that I know 
 of to be said against this excellent conspectus of the 
 reasons for believing in the subaerial origin of coal. 
 
 But the coal accumulated upon the area cov- 
 ered by one of the great forests of the carbonifer- 
 ous epoch would, in course of time, have been 
 wasted away by the small, but constant, wear and 
 tear of rain and streams, had the land which sup- 
 ported it remained at the same level, or been 
 gradually raised to a greater elevation. And, no 
 doubt, as much coal as now exists has been de- 
 stroyed, after its formation, in this way. What 
 are now known as coal districts owe their import- 
 ance to the fact that they were areas of slow de- 
 pression, during a greater or less portion of the 
 carboniferous epoch; and that, in virtue of this 
 circumstance, Mother Earth was enabled to cover 
 
158 ON THE FORMATION OP COAL, v 
 
 up her vegetable treasures, and preserve them 
 from destruction. 
 
 Wherever a coal-field now exists, there must 
 formerly have been free access for a great river, or 
 for a shallow sea, bearing sediment in the shape of 
 sand and mud. When the coal-forest area became 
 slowly depressed, the waters must have spread 
 over it, and have deposited their burden upon the 
 surface of the bed of coal, in the form of layers, 
 which are now converted into shale, or sandstone. 
 Then followed a period of rest, in which the super- 
 incumbent shallow waters became completely 
 filled up, and finally replaced, by fine mud, which 
 settled down into a new under-clay, and furnished 
 the soil for a fresh forest growth. This flourished, 
 and heaped up its spores and wood into coal, until 
 the stage of slow depression recommenced. And, 
 in some localities, as I have mentioned, the pro- 
 cess was repeated until the first of the alternating 
 beds had sunk to near three miles below its origi- 
 nal level at the surface of the earth. 
 
 In reflecting on the statement, thus briefly 
 made, of the main facts connected with the origin 
 of the coal formed during the carboniferous epoch, 
 two or three considerations suggest themselves. 
 
 In the first place, the great phantom of geo- 
 logical time rises before the student of this, as of 
 all other, fragments of the history of our earth — 
 springing irrepressibly out of the facts, like the 
 Djin from the Jar which the fishermen so incau- 
 
V ON THE FORMATION OF COAL. 159 
 
 tiously opened; and like the Djin again, being va- 
 porous, shifting, and indefinable, but unmistakably- 
 gigantic. However modest the bases of one's cal- 
 culation may be, the minimum of time assignable 
 to the coal period remains something stupendous. 
 Principal Dawson is the last person likely to be 
 guilty of exaggeration in this matter, and it will be 
 well to consider what he has to say about it: — 
 
 "The rate of accumulation of coal was very slow. 
 The climate of the period, in the northern temperate zone, 
 was of such a character that the true conifers show rings 
 of growth, not larger, nor much less distinct, than those 
 of many of their modern congeners. The Sigillariw and 
 Calamites were not, as often supposed, composed wholly, 
 or even principally, of lax and soft tissues, or necessarily 
 short-lived. The former had, it is true, a very thick 
 inner bark; but their dense woody axis, their thick and 
 nearly imperishable outer bark, and their scanty and 
 rigid foliage, would indicate no very rapid growth or 
 decay. In the case of the Sigillariw, the variations in 
 the leaf-scars in different parts of the trunk, the inter- 
 calation of new ridges at the surface representing that 
 of new woody wedges in the axis, the transverse marks 
 left by the stages of upward growth, all indicate that 
 several years must have been required for the growth of 
 stems of moderate size. The enormous roots of these 
 trees, and the condition of the coal-swamps, must have 
 exempted them from the danger of being overthrown by 
 violence. They probably fell in successive generations 
 from natural decay; and making every allowance for 
 other materials, we may safely assert that every foot of 
 thickness of pure bituminous coal implies the quiet 
 growth and fall of at least fifty generations of Sioillarim, 
 and therefore an undisturbed condition of forest growth 
 
160 ON THE FORMATION OF COAL. v 
 
 enduring through many centuries. Further, there is evi- 
 dence that an immense amount of loose parenchymatous 
 tissue, and even of wood, perished by decay, and we do 
 not know to what extent even the most durable tissues 
 may have disappeared in this way; so that, in many coal- 
 seams, we may have only a very small part of the vege- 
 table matter produced." 
 
 Undoubtedly the force of these reflections is 
 not diminished when the bituminous coal, as in 
 Britain, consists of accumulated spores and spore- 
 cases, rather than of stems. But, suppose we 
 adopt Principal Dawson's assumption, that one 
 foot of coal represents fifty generations of coal 
 plants; and, further, make the moderate supposi- 
 tion that each generation of coal plants took ten 
 years to come to maturity — then, each foot-thick- 
 ness of coal represents five hundred years. The 
 superimposed beds of coal in one coal-field may 
 amount to a thickness of fifty or sixty feet, and 
 therefore the coal alone, in that field, represents 
 500 X 50 = 25,000 years. But the actual coal is 
 but an insignificant portion of the total deposit, 
 which, as has been seen, may amount to between 
 two and three miles of Yertical thickness. Sup- 
 pose it be 12,000 feet — which is 340 times the 
 thickness of the actual coal — is there any reason 
 why we should believe it may not have taken 240 
 times as long to form? I know of none. But, in 
 this case, the time which the coal-field represents 
 would be 25,000 X 340 = 6,000,000 years. As 
 affording a definite chronology, of course such cal- 
 
V ON THE FORMATION OP COAL. 161 
 
 culations as these are of no value; but they have 
 much use in fixing one's attention upon a possible 
 minimum. A man may be puzzled if he is asked 
 how long Rome took a-building; but he is proverb- 
 ially safe if he af&rms it not to have been built in 
 a day; and our geological calculations are all, at 
 present, pretty much on that footing. 
 
 A second consideration which the study of the 
 coal brings prominently before the mind of any 
 one who is familiar with paleontology is, that the 
 coal Flora, viewed in relation to the enormous 
 period of time which it lasted, and to the still 
 vaster period which has elapsed since it flourished, 
 underwent little change while it endured, and in 
 its peculiar characters differs strangely little from 
 that which at present exists. 
 
 The same species of plants are to be met with 
 throughout the whole thickness of a coal-field, and 
 the youngest are not sensibly different from the 
 oldest. But more than this. Notwithstanding 
 that the carboniferous period is separated from us 
 by more than the whole time represented by the 
 secondary and tertiary formations, the great types 
 of vegetation were as distinct then as now. The 
 structure of the modern club-moss furnishes a 
 complete explanation of the fossil remains of the 
 Lepidodendra, and the fronds of some of the an- 
 cient ferns are hard to distinguish from existing 
 ones. At the same time, it must be remembered, 
 
 that there is nowhere in the world, at present, any 
 197 
 
162 ON THE FORMATION OP COAL. T 
 
 forest which bears more than a rough analogy with 
 a coal-forest. The types may remain, but the de- 
 tails of their form, their relative proportions, their 
 associates, are all altered. And the tree-fern 
 forest of Tasmania, or New Zealand, gives one 
 only a faint and remote image of the vegetation of 
 the ancient world. 
 
 Once more, an invariably recurring lesson of 
 geological history, at whatever point its study is 
 taken up: the lesson of the almost infinite slow- 
 ness of the modification of living forms. The 
 lines of the pedigrees of living things break off 
 almost before they begin to converge. 
 
 Finally, yet another curious consideration. 
 Let us suppose that one of the stupid, salamander- 
 like Labyrinthodonts, which pottered, with much 
 belly and little leg, like Falstaff in his old age, 
 among the coal-forests, could have had thinking 
 power enough in his small brain to reflect upon the 
 showers of spores which kept on falling through 
 years and centuries, while perhaps not one in ten 
 million fulfilled its apparent purpose, and repro- 
 duced the organism which gave it birth: surely he 
 might have been excused for moralizing upon the 
 thoughtless and wanton extravagance which Na- 
 ture displayed in her operations. 
 
 But we have the advantage over our shovel- 
 headed predecessor — or possibly ancestor — and 
 can perceive that a certain vein of thrift runs 
 through this apparent prodigality. Nature is 
 
V ON THE FORMATION OP COAL. 163 
 
 never in a hurry, and seems to have had always 
 before her eyes the adage, " Keep a thing long 
 enough, and you will find a use for it." She has 
 kept her beds of coal many millions of years with- 
 out being able to find much use for them; she has 
 sent them down beneath the sea, and the sea-beasts 
 could make nothing of them; she has raised them 
 up into dry land, and laid the black veins bare, 
 and still, for ages and ages, there was no living 
 thing on the face of the earth that could see any 
 sort of value in them; and it was only the other 
 day, so to speak, that she turned a new creature out 
 of her workshop, who by degrees acquired suffi- 
 cient wits to make a fire, and then to discover that 
 the black rock would burn. 
 
 I suppose that nineteen hundred years ago, 
 when Julius Caasar was good enough to deal with 
 Britain as we have dealt with New Zealand, the 
 primaeval Briton, blue 'with cold and woad, may 
 have known that the strange black stone, of which 
 he found lumps here and there in his wanderings, 
 would burn, and so help to warm his body and 
 cook his food. Saxon, Dane, and Norman 
 swarmed into the land. The English people grew 
 into a powerful nation, and Nature still waited for 
 a full return of the capital she had invested in the 
 ancient club-mosses. The eighteenth century ar- 
 rived, and with it James Watt. The brain of that 
 man was the spore out of which was developed the 
 modern steam-engine, and all the prodigious trees 
 
164 ON THE FORMATION OP COAL. v 
 
 and branches of modern industry which have grown 
 out of this. But coal is as much an essential con- 
 dition of this growth and development as carbonic 
 acid is for that of a club-moss. Wanting coal, we 
 could not have smelted the iron needed to make 
 our engines, nor have worked our engines when 
 we had got them. But take away the engines, and 
 the great towns of Yorkshire and Lancashire van- 
 ish like a dream. Manufactures give place to 
 agriculture and pasture, and not ten men can live 
 where now ten thousand are amply supported. 
 
 Thus, all this abundant wealth of money and 
 of vivid life is Nature's interest upon her invest- 
 ment in club-mosses, and the like, so long ago. 
 But what becomes of the coal which is burnt in 
 yielding this interest? Heat comes out of it, light 
 comes out of it; and if we could gather together 
 all that goes up the chimney, and all that remains 
 in the grate of a thoroughly-burnt coal-fire, we 
 should find ourselves in possession of a quantity of 
 carbonic acid, water, ammonia, and mineral mat- 
 ters, exactly equal in weight to the coal. But 
 these are the very matters with which Nature sup- 
 plied the club-mosses which made the coal. She 
 is paid back principal and interest at the same 
 time; and she straightway invests the carbonic 
 acid, the water, and the ammonia in new forms of 
 life, feeding with them the plants that now live. 
 Thrifty Nature! Surely no prodigal, but most 
 notable of housekeepers! 
 
VI. 
 
 ON THE BOEDER TEREITOEY BE- 
 TWEEN" THE ANIMAL AND THE 
 VEGETABLE KINGDOMS. 
 
 [1876.] 
 
 In the whole history of science there is nothing 
 more remarkable than the rapidity of the growth 
 of biological knowledge within the last half-cen- 
 tury, and the extent of the modification which has 
 thereby been effected in some of the fundamental 
 conceptions of the naturalist. 
 
 In the second edition of the " Regne Animal," 
 published in 1838, Cuvier devotes a special section 
 to the " Division of Organised Beings into Animals 
 and Vegetables," in which the question is treated 
 with that comprehensiveness of knowledge and 
 clear critical judgment which characterise his 
 writings, and justify us in regarding them as re- 
 presentative expressions of the most extensive, if 
 not the profoundest, knowledge of his time. He 
 tells us that living beings have been subdivided 
 from the earliest times into animated beings, which 
 possess sense and motion, and inanimated beings^ 
 
 185 
 
166 ANIMALS AND PLANTS. vi 
 
 which are devoid of these functions and simply 
 vegetate. 
 
 Although the roots of plants direct themselves 
 towards moisture, and their leaves towards air and 
 light, — although the parts of some plants exhibit 
 oscillating movements without any perceptible 
 cause, and the leaves of others retract when 
 touched, — yet none of these movements justify the 
 ascription to plants of perception or of will. 
 From the mobility of animals, Cuvier, with his 
 characteristic partiality for teleological reasoning, 
 deduces the necessity of the existence in them of 
 an alimentary cavity, or reservoir of food, whence 
 their nutrition may be drawn by the vessels, which 
 are a sort of internal roots; and, in the presence 
 of this alimentary cavity, he naturally sees the 
 primary and the most important distinction be- 
 tween animals and plants. 
 
 Following out his teleological argument, Cu- 
 vier remarks that the organisation of this cavity 
 and its appurtenances must needs vary according 
 to the nature of the aliment, and the operations 
 which it has to undergo, before it can be converted 
 into substances fitted for absorption; while the 
 atmosphere and the earth supply plants with 
 juices ready prepared, and which can be absorbed 
 immediately. As the animal body required to be 
 independent of heat and of the atmosphere, there 
 were no means by which the motion of its fluids 
 could be produced by internal causes. Hence 
 
VI ANIMALS AND PLANTS. 167 
 
 arose the second great distinctive character of ani- 
 mals, or the circulatory system, which is less im- 
 portant than the digestive, since it was unneces- 
 sary, and therefore is absent, in the more simple 
 animals. 
 
 Animals further needed muscles for locomo- 
 tion and nerves for sensibility. Hence, says Cu- 
 vier, it was necessary that the chemical composi- 
 tion of the animal body should be more compli- 
 cated than that of the plant; and it is so, inas- 
 much as an additional substance, nitrogen, enters 
 into it as an essential element; while, in plants, 
 nitrogen is only accidentally joined with the three 
 other fundamental constituents of organic beings 
 — carbon, hydrogen, and oxygen. Indeed, he 
 afterwards affirms that nitrogen is peculiar to ani- 
 mals; and herein he places the third distinction 
 between the animal and the plant. The soil and 
 the atmosphere supply plants with water, com- 
 posed of hydrogen and oxygen; air, consisting of 
 nitrogen and oxygen; and carbonic acid, contain- 
 ing carbon and oxygen. They retain the hydro- 
 gen and the carbon, exhale the superfluous oxygen, 
 and absorb little or no nitrogen. The essential 
 character of vegetable life is the exhalation of oxy- 
 gen, which is eifected through the agency of light. 
 Animals, on the contrary, derive their nourish- 
 ment either directly or indirectly from plants. 
 They get rid of the superfluous hydrogen and car- 
 bon, and accumulate nitrogen. The relations of 
 
168 ANIMALS AND PLANTS. vi 
 
 plants and animals to the atmosphere are therefore 
 inverse. The plant withdraws water and carbonic 
 acid from the atmosphere, the animal contributes 
 both to it. Eespiration — that is, the absorption 
 of oxygen and the exhalation of carbonic acid — is 
 the specially animal function of animals, and con- 
 stitutes their fourth distinctive character. 
 
 Thus wrote Cuvier in 1828. But, in the 
 fourth and fifth decades of this century, the great- 
 est and most rapid revolution which biological sci- 
 ence has ever undergone was effected by the appli- 
 cation of the modern microscope to the investiga- 
 tion of organic structure; by the introduction of 
 exact and easily manageable methods of conduct- 
 ing the chemical analysis of organic compounds; 
 and finally, by the employment of instruments of 
 precision for the measurement of the physical 
 forces which are at work in the living economy. 
 
 That the semi-fluid contents (which we now 
 term protoplasm) of the cells of certain plants, 
 such as the Charm, are in constant and regular 
 motion, was made out by Bonaventura Corti a 
 century ago; but the fact, important as it was, 
 fell into oblivion, and had to be rediscovered by 
 Treviranus in 1807. Eobert Brown noted the 
 more complex motions of the protoplasm in the 
 cells of Tradescantia in 1831; and now such move- 
 ments of the living substance of plants are well 
 known to be some of the most widely-prevalent 
 phenomena of vegetable life. 
 
VI ANIMALS AND PLANTS. 169 
 
 Agardh, and other of the botanists of Cuvier's 
 generation, who occupied themselves with the 
 lower plants, had observed that, under particular 
 circumstances, the contents of the cells of certain 
 water-weeds were set free, and moved about with 
 considerable velocity, and with all the appearances 
 of spontaneity, as locomotive bodies, which, from 
 their similarity to animals of simple organisation, 
 were called " zoospores." Even as late as 1845, 
 however, a botanist of Schleiden's eminence dealt 
 very sceptically with these statements; and his 
 scepticism was the more justified, since Ehren- 
 berg, in his elaborate and comprehensive work on 
 the Infusoria, had declared the greater number of 
 what are now recognised as locomotive plants to 
 be animals. 
 
 At the present day, innumerable plants and 
 free plant cells are known to pass the whole or part 
 of their lives in an actively locomotive condition, 
 in no wise distinguishable from that of one of the 
 simpler animals; and, while in this condition, 
 their movements are, to all appearances, as spon- 
 taneous — as much the product of volition — as 
 those of such, animals. 
 
 Hence the teleological argument for Cuvier's 
 first diagnostic character — the presence in animals 
 of an alimentary cavity, or internal pocket, in 
 which they can carry about their nutriment — has 
 broken down, so far, at least, as his mode of stat- 
 ing it goes. And, with the advance of micro- 
 
170 ANIMALS AND PLANTS. vi 
 
 scopic anatomy, the universality of the fact itself 
 among animals has ceased to be predicable. Many 
 animals of even complex structure, v?hich live 
 parasitieally within others, are wholly devoid of 
 an alimentary cavity. Their food is provided for 
 them, not only ready cooked, but ready digested, 
 and the alimentary canal, become superfluous, has 
 disappeared. Again, the males of most Kotifers 
 have no digestive apparatus; as a German natu- 
 ralist has remarked, they devote themselves entire- 
 ly to the " Minnedienst," and are to be reckoned 
 among the few realisations of the Byronic ideal of 
 a lover. Finally, amidst the lowest forms of ani- 
 mal life, the speck of gelatinous protoplasm, which 
 constitutes the whole body, has no permanent di- 
 gestive cavity or mouth, but takes in its food any- 
 where; and digests, so to speak, all over its body. 
 
 But although Cuvier's leading diagnosis of 
 the animal from the plant will not stand a strict 
 test, it remains one of the most constant of the dis- 
 tinctive characters of animals. And, if we sub- 
 stitute for the possession of an alimentary cavity, 
 the power of taking solid nutriment into the body 
 and there digesting it, the definition so changed 
 will cover all animals, except certain parasites, 
 and the few and exceptional cases of non-parasitic 
 animals which do not feed at all. On the other 
 hand, the definition thus amended will exclude all 
 ordinary vegetable organisms. 
 
 Ouvier himself practically gives up his second 
 
VI ANIMALS AND PLANTS. 171 
 
 distinctive mark when he admits that it is want- 
 ing in the simpler animals. 
 
 The third distinction is based on a completely 
 erroneous conception of the chemical difEerences 
 and resemblances between the constituents of ani- 
 mal and vegetable organisms, for which Cuvier is 
 not responsible, as it was current among con- 
 temporary chemists. It is now established that 
 nitrogen is as essential a constituent of vegetable 
 as of animal living matter; and that the latter is, 
 chemically speaking, just as complicated as the 
 former. Starchy substances, cellulose and sugar, 
 once supposed to be exclusively confined to plants, 
 are now known to be regular and normal products 
 of animals. Amylaceous and saccharine sub- 
 stances are largely manufactured, even by the 
 highest animals; cellulose is widespread as a con- 
 stituent of the skeletons of the lower animals; 
 and it is probable that amyloid substances are uni- 
 versally present in the animal organism, though 
 not in the precise form of starch. 
 
 Moreover, although it remains true that there 
 is an inverse relation between the green plant in 
 sunshine and the animal, in so far as, under these 
 circumstances, the green plant decomposes car- 
 bonic acid and exhales oxygen, while the animal 
 absorbs oxygen and exhales carbonic acid; yet, the 
 exact researches of the modern chemical investi- 
 gators of the physiological processes of plants have 
 clearly demonstrated the fallacy of attempting to 
 
172 ANIMALS AND PLANTS. ti 
 
 draw any general distinction between animals and 
 vegetables on this ground. In fact, the difference 
 vanishes with the sunshine, even in the case of the 
 green plant; which, in the dark, absorbs oxygen 
 and gives out carbonic acid like any animal.* On 
 the other hand, those plants, such as the fungi, 
 which contain no chlorophyll and are not green, 
 are always, so far as respiration is concerned, in 
 the exact position of animals. They absorb oxy- 
 gen and give out carbonic acid. 
 
 Thus, by the progress of knowledge, Cuvier's 
 fourth distinction between the animal and the 
 plant has been as completely invalidated as the 
 third and second; and even the first can be re- 
 tained only in a modified form and subject to ex- 
 ceptions. 
 
 But has the advance of biology simply tended 
 to break down old distinctions, without establish- 
 ing new ones? 
 
 With a qualification, to be considered present- 
 ly, the answer to this question is undoubtedly in 
 the afiirmative. The famous researches of 
 Schwann and Schleiden in 1837 and the following 
 years, founded the modern science of histology, or 
 
 * There is every reason to believe that living plants, 
 like living animals, always respire, and, in respiring, ab- 
 sorb oxygen and give off carbonic acid; but, that in 
 green plants exposed to daylight or to the electric light, 
 the quantity o{ oxygen evolved in consequence of the de- 
 composition of carbonic acid by a special apparatus which 
 green plants possess exceeds that absorbed in the con- 
 current respiratory process. 
 
Ti ANIMALS AND PLANTS. 173 
 
 that branch of anatomy which deals with the ulti- 
 mate visible structure of organisms, as revealed by 
 the microscope; and, from that day to this, the 
 rapid improvement of methods of investigation, 
 and the energy of a host of accurate observers, 
 have given greater and greater breadth and firm- 
 ness to Schwann's great generalisation, that a fun- 
 damental unity of structure obtains in animals 
 and plants; and that, however diverse may be the 
 fabrics, or tissues, of which their bodies are com- 
 posed, all these varied structures result from the 
 metamorphosis of morphological units (termed 
 cells, in a more general sense than that in which 
 the word " cells " was at first employed), which 
 are not only similar in animals and in plants re- 
 spectively, but present a close resemblance, when 
 those of animals and those of plants are compared 
 together. 
 
 The contractility which is the fundamental 
 condition of locomotion, has not only been discov- 
 ered to exist far more widely among plants than 
 was formerly imagined; but, in plants, the act of 
 contraction has been found to be accompanied, as 
 Dr. Burdon Sanderson's interesting investigations 
 have shown, by a disturbance of the electrical 
 state of the contractile substance, comparable to 
 that which was found by Du Bois Eeymond to be 
 a concomitant of the activity of ordinary muscle 
 in animals. 
 
 Again, I know of no test by which the reaction 
 
174 ANIMALS AND PLANTS. vi 
 
 of the leaves of the Sundew and of other plants to 
 stimuli, so fully and carefully studied by Mr. Dar- 
 win, can be distinguished from those acts of con- 
 traction following upon stimuli, which are called 
 " reflex " in animals. 
 
 On each lobe of the bilobed leaf of Venus's fly- 
 trap {Dionwa muscipula) are three delicate fila- 
 ments which stand out at right angle from the sur- 
 face of the leaf. Touch one of them with the end 
 of a fine human hair and the lobes of the leaf in- 
 stantly close together * in virtue of an act of con- 
 traction of part of their substance, just as the body 
 of a snail contracts into its shell when one of its 
 " horns " is irritated. 
 
 The reflex action of the snail is the result of 
 the presence of a nervous system in the animal. 
 A molecular change takes place in the nerve of the 
 tentacle, is propagated to the muscles by which the 
 body is retracted, and causing them to retract, 
 the action of retraction is brought about. Of 
 course the similarity of the acts does not necessa- 
 rily involve the conclusion that the mechanism by 
 which they are effected is the same; but it sug- 
 gests a suspicion of their identity which needs 
 careful testing. 
 
 The results of recent inquiries into the struc- 
 ture of the nervous system of animals converge to- 
 wards the conclusion that the nerve fibres, which 
 we have hitherto regarded as ultimate elements of 
 * Darwin, Insectivorous Plants, p. 289. 
 
VI ANIMALS AND PLANTS. 175 
 
 nervous tissue, are not such, but are simply the 
 visible aggregations of vastly more attenuated fila- 
 ments, the diameter of which dwindles down to 
 the limits of our present microscopic vision, great- 
 ly as these have been extended by modern improve- 
 ments of the microscope; and that a nerve is, in its 
 essence, nothing but a linear tract of specially 
 modified protoplasm between two points of an or- 
 ganism — one of which is able to affect the other 
 by means of the communication so established. 
 Hence, it is conceivable that even the simplest liv- 
 ing being may possess a nervous system. And 
 the question whether plants are provided with a 
 nervous system or not, thus acquires a new aspect, 
 and presents the histologist and physiologist with 
 a problem of extreme difficulty, which must be at- 
 tacked from a new point of view and by the aid 
 of methods which have yet to be invented. 
 
 Thus it must be admitted that plants may be 
 contractile and locomotive; that, while locomo- 
 tive, their movements may have as much appear- 
 ance of spontaneity as those of the lowest animals; 
 and that many exhibit actions comparable to those 
 which are brought about by the agency of a ner- 
 vous system in animals. And it must be allowed 
 to be possible that further research may reveal 
 the existence of something comparable to a nerv- 
 ous system in plants. So that I know not where 
 we can hope to find any absolute distinction be- 
 tween animals and plants, unless we return to 
 
176 ANIMALS AND PLANTS. vi 
 
 their mode of nutrition, and inquire whether cer- 
 tain differences of a more occult character than 
 those imagined to exist by Cuvier, and which cer- 
 tainly hold good for the vast majority of animals 
 and plants, are of universal application. 
 
 A bean may be supplied with water in which 
 salts of ammonia and certain other mineral salts 
 are dissolved in due proportion; with atmospheric 
 air containing its ordinary minute dose of carbonic 
 acid; and with nothing else but sunlight and heat. 
 Under these circumstances, unnatural as they are, 
 with proper management, the bean will thrust 
 forth its radicle and its plumule; the former will 
 grow down into roots, the latter grow up into the 
 stems and leaves of a vigorous bean-plant; and 
 this plant will, in due time, iiower and pxoduce its 
 crop of beans, just as if it were grown in the gar- 
 den or in the field. 
 
 The weight of the nitrogenous protein com- 
 pounds, of the oily, starchy, saccharine and woody 
 substances contained in the full-grown plant and 
 its seeds, will be vastly greater than the weight of 
 the same substances contained in the bean from 
 which it sprang. But nothing has been supplied 
 to the bean save water, carbonic acid, ammonia, 
 potash, lime, iron, and the like, in combination 
 with phosphoric, sulphuric, and other acids. 
 Neither protein, nor fat, nor starch, nor sugar, nor 
 any substance in the slightest degree resembling 
 them, has formed part of the food of the bean. 
 
VI ANIMALS AND PLANTS. 177 
 
 But the weights of the carbon, hydrogen, oxygen, 
 nitrogen, phosphorus, sulphur, and other ele- 
 mentary bodies contained in the bean-plant, and in 
 the seeds which it produces, are exactly equivalent 
 to the weights of the same elements which have 
 disappeared from the materials supplied to the 
 bean during its growth. Whence it follows that 
 the bean has taken in only the raw materials of its 
 fabric, and has manufactured them into bean- 
 stuffs. ' 
 
 The bean has been able to perform this great 
 chemical feat by the help of its green colouring 
 matter, or chlorophyll; for it is only the green 
 parts of the plant which, under the influence of 
 sunlight, have the marvellous power of decom- 
 posing carbonic acid, setting free the oxygen and 
 laying hold of the carbon which it contains. In 
 fact, the bean obtains two of the absolutely in- 
 dispensable elements of its substance from two 
 distinct sources; the watery solution, in which its 
 roots are plunged, contains nitrogen but no car- 
 bon; the air, to which the leaves are exposed, con- 
 tains carbon, but its nitrogen is in the state of a 
 free gas, in which condition the bean can make no 
 use of it * and the chlorophyll f is the apparatus 
 
 * I purposely assume that the air with which the bean 
 is supplied in the ease stated contains no ammoniacal 
 salts. 
 
 t The recent researches of Pringsheim have raised a 
 host of questions as to the exact share taken by chloro- 
 phyll in the chemical operations which are effected by 
 the green parts of plants. It may be that the ehloro- 
 198 
 
178 ANIMALS AND PLANTS. vi 
 
 by which the carbon is extracted from the atmo- 
 spheric carbonic acid — the leaves being the chief 
 laboratories in which this operation is effected. 
 
 The great majority of conspicuous plants are, 
 as everybody knows, green; and this arises from 
 the abundance of their chlorophyll. The few 
 which contain no chlorophyll and are colourless, 
 are unable to extract the carbon which they re- 
 quire from atmospheric carbonic acid, and lead a 
 parasitic existence upon other plants; but it by no 
 means follows, often as the statement has been 
 repeated, that the manufacturing power of plants 
 depends on their chlorophyll, and its interaction 
 with the rays of the sun. On the contrary, it is 
 easily demonstrated, as Pasteur first proved, that 
 the lowest fungi, devoid of chlorophyll, or of any 
 substitute for it, as they are, nevertheless possess 
 the characteristic manufacturing powers of plants 
 in a very high degree. Only it is necessary that 
 they should be supplied with a different kind of 
 raw material; as they cannot extract carbon from 
 carbonic acid, they must be furnished with some- 
 thing else that contains carbon. Tartaric acid is 
 such a substance; and if a single spore of the com- 
 monest and most troublesome of moulds — Peni- 
 cillium — ^be sown in a saucerful of water, in which 
 tartrate of ammonia, with a small percentage of 
 phosphates and sulphates is contained, and kept 
 
 phyll is only a constant concomitant of the actual de- 
 oxidising apparatus. 
 
VI ANIMALS AND PLANTS. 179 
 
 warm, whether in the dark or exposed to light, 
 it will, in a short time, give rise to a thick crust 
 of mould, which contains many million times 
 the weight of the original spore, in protein com- 
 pounds and cellulose. Thus we have a very wide 
 basis of fact for the generalisation that plants 
 are essentially characterised by their manufac- 
 turing capacity — ^by their power of working up 
 mere mineral matters into complex organic com- 
 pounds. 
 
 Contrariwise, there is a no less wide foundation 
 for the generalisation that animals, as Cuvier puts 
 it, depend directly or indirectly upon plants for 
 the materials of their bodies; that is, either they 
 are herbivorous, or they eat other animals which 
 are herbivorous. 
 
 But for what constituents of their bodies are 
 animals thus dependent upon plants? Certainly 
 not for their horny matter; nor for chondrin, 
 the proximate chemical element of cartilage; nor 
 for gelatine; nor for syntonin, the constituent of 
 muscle; nor for their nervous or biliary sub- 
 stances; nor for their amyloid matters; nor, neces- 
 sarily, for their fats. 
 
 It can be experimentally demonstrated that 
 animals can make these for themselves. But that 
 which they cannot make, but must, in all known 
 cases, obtain directly or indirectly from plants, is 
 the peculiar nitrogenous matter, protein. Thus 
 the plant is the ideal proletaire of the living world, 
 
180 ANIMALS AND PLANTS. vi 
 
 the worker who produces; the animal, the ideal 
 aristocrat, who mostly occupies himself in consum- 
 ing, after the manner of that noble representative 
 of the line of Zahdarm, whose epitaph is written in 
 " Sartor Eesartus." 
 
 Here is our last hope of finding a sharp line of 
 demarcation between plants and animals; for, as 
 I have already hinted, there is a border territory 
 between the two kingdoms, a sort of no-man's- 
 land, the inhabitants of which certainly cannot be 
 discriminated and brought to their proper allegi- 
 ance in any other way. 
 
 Some months ago, Professor Tyndall asked me 
 to examine a drop of infusion of hay, placed under 
 an excellent and powerful microscope, and to tell 
 him what I thought some organisms visible in it 
 were. I looked and observed, in the first place, 
 multitudes of Bacteria moving about with their 
 ordinary intermittent spasmodic wriggles. As to 
 the vegetable nature of these there is now no 
 doubt. Not only does the close resemblance of the 
 Bacteria to unquestionable plants, such as the 
 Oscillatoriw and the lower forms of Fungi, justify 
 this conclusion, but the manufacturing test settles 
 the question at once. It is only needful to add a 
 minute drop of fluid containing Bacteria to water 
 in which tartrate, phosphate, and sulphate of am- 
 monia are dissolved; and, in a very short space of 
 time, the clear fluid becomes milky by reason of 
 their prodigious multiplication, which, of course, 
 
VI ANIMALS AND PLANTS. ISl 
 
 implies the manufacture of living Bacterium-stufE 
 out of these merely saline matters. 
 
 But other active organisms, very much larger 
 than the Bacteria, attaining in fact the compara- 
 tively gigantic dimensions of ^jnr^^ °^ ^^ ^^'^^ °^ 
 more, incessantly crossed the field of view. Each 
 of these had a body shaped like a pear, the small 
 end being slightly incurved and produced into a 
 long curved filament, or cilium, of extreme tenuity. 
 Behind this, from the concave side of the incurva- 
 tion, proceeded another long cilium, so delicate as 
 to be discernible only by the use of the highest 
 powers and careful management of the light. In 
 the centre of the pear-shaped body a clear round 
 space could occasionally be discerned, but not 
 always; and careful watching showed that this 
 clear vacuity appeared gradually, and then shut up 
 and disappeared suddenly, at regular intervals. 
 Such a structure is of common occurrence among 
 the lowest plants and animals, and is known as a 
 contractile vacuole. 
 
 The little creature thus described sometimes 
 propelled itself with great activity, with a curious 
 rolling motion, by the lashing of the front cilium, 
 while the second cilium trailed behind; sometimes 
 it anchored itself by the hinder cilium and was 
 spun round by the working of the other, its mo- 
 tions resembling those of an anchor buoy in a 
 heavy sea. Sometimes, when two were in full 
 career towards one another, each would appear 
 
182 ANIMALS AND. PLANTS. vi 
 
 dexterously to get out of the other's way; some- 
 times a crowd would assemble and jostle one an- 
 other, with as much semblance of individual ef- 
 fort as a spectator on the Grands Mulets might 
 observe with a telescope among the specks repre- 
 senting, men in the valley of Chamounix. 
 
 The spectacle, though always surprising, was 
 not new to me. So my reply to the question put 
 to me was, that these organisms were what biolo- 
 gists call Monads, and though they might be ani- 
 mals, it was also possible that they might, like the 
 Bacteria, be plants. My friend received my ver- 
 dict with an expression which showed a sad want 
 of respect for authority. He would as soon be- 
 lieve that a sheep was a plant. Naturally piqued 
 by this want of faith, I have thought a good deal 
 over the matter; and, as I still rest in the lame 
 conclusion I originally expressed, and must even 
 now confess that I cannot certainly say whether 
 this creature is an animal or a plant, I think it 
 may be well to state the grounds of my hesitation 
 at length. But, in the first place, in order that I 
 may conveniently distinguish this " Monad " from 
 the multitude of other things which go by the 
 same designation, I must give it a name of its own. 
 I think (though, for reasons which need not be 
 stated at present, I am not quite sure) that it is 
 identical with the species Monas lens, as defined 
 by the eminent French microscopist Dujardin, 
 though his magnifying power was probably insuffi- 
 
VI ANIMALS, AND PLANTS. 183 
 
 cient to enable him to see that it is curiously like 
 a much larger form of monad which he has named 
 Heteromita. I shall, therefore, call it not Monas, 
 but Heteromita lens. 
 
 I have been unable to devote to my Heteromita 
 the prolonged study needful to work out its whole 
 history, which would involve weeks, or it may he 
 months, of unremitting attention. But I the less 
 regret this circumstance, as some remarkable ob- 
 servations recently published by Messrs.- Dallinger 
 and Drysdale * on certain Monads, relate, in part, 
 to a form so similar to my Heteromita lens, that 
 the history of the one may be used to illustrate 
 that of the other. These most patient and pains- 
 taking observers, who employed the highest attain- 
 able powers of the miscroscope and, relieving one 
 another, kept watch day and night over the same 
 individual monads, have been enabled to trace out 
 the whole history of their Heteromita; which they 
 found in infusions of the heads of fishes of the Cod 
 tribe. 
 
 Of the four monads described and figured by 
 these investigators, one, as I have said, very closely 
 resembles Heteromita lens in every particular, ex- 
 cept that it has a separately distinguishable cen- 
 tral particle or "nucleus," which is not certainly 
 to be made out in Heteromita lens; and that noth- 
 
 * " Researches in the Life-history of a Cereomonad : a 
 Lesson in Biogenesis " ; and " Further Researches in the 
 Life-history of the Mona,ds."— Monthly Microscopical 
 Journal, 1873. 
 
184 ANIMALS AND PLANTS. vi 
 
 ing is said by Messrs. Dallinger and Drysdale of 
 the existence of a contractile vacuole in this mo- 
 nad, though they describe it in another. 
 
 Their Heteromita, however, multiplied rapidly 
 by fission. Sometimes a transverse constriction 
 appeared; the hinder half developed a new cilium, 
 and the hinder cilium gradually split from its base 
 to its free end, until it was divided into two; a 
 process which, considering the fact that this fine 
 filament cannot be much more than xinjVTSTr^^ °^ 
 an inch in diameter, is wonderful enough. The 
 constriction of the body extended inwards until 
 the two portions were united by a narrow isthmus; 
 finally, they separated and each swam away by it- 
 self, a complete Heteromita, provided with its two 
 cilia. Sometimes the constriction took a longitu- 
 dinal direction, with the same ultimate result. In 
 each case the process occupied not more than six 
 or seven minutes. At this rate, a single Hete- 
 romita would give rise to a thousand like itself in 
 the course of an hour, to about a million in two 
 hours, and to a number greater than the generally 
 assumed number of human beings now living in 
 the world in three hours; or, if we give each Hete- 
 romita an hour's enjoyment of individual exist- 
 ence, the same result will be obtained in about a 
 day. The apparent suddenness of the appearance 
 of multitudes of such organisms as these, in any 
 nutritive fluid to which one obtains access, is thus 
 easily explained. 
 
VI ANIMALS AND PLANTS. 185 
 
 During these processes of multiplication by 
 fission, the Heteromita remains active; but some- 
 times another mode of fission occurs. The body 
 becomes rounded and quiescent, or nearly so; and, 
 while in this resting state, divides into two por- 
 tions, each of which is rapidly converted into an 
 active Heteromita. 
 
 A still more remarkable phenomenon is that 
 kind of multiplication which is preceded by the 
 union of two monads, by a process which is termed 
 conjugation. Two active Heteromitoe become ap- 
 plied to one another, and then slowly and gradu- 
 ally coalesce into one body. The two nuclei run 
 into one; and the mass resulting from the conju- 
 gation of the two Heteromitoe, thus fused together, 
 has a triangular form. The two pairs of cilia are 
 to be seen, for some time, at two of the angles, 
 which answer to the small ends of the conjoined 
 monads; but they ultimately vanish, and the twin 
 organism, in which all visible traces of organisa- 
 tion have disappeared, falls into a state of rest. 
 Sudden wave-like movements of its substance next 
 occur; and, in a short time, the apices of the tri- 
 angular mass burst, and give exit to a dense yel- 
 lowish, glairy fiuid, filled with minute granules. 
 This process, which, it will be observed, involves 
 the actual confluence and mixture of the substance 
 of two distinct organisms, is effected in the space 
 of about two hours. 
 
 The authors whom I quote say that they " can- 
 
186 AKIMALS AND PLANTS. vi 
 
 not express " the excessive minuteness of the gran- 
 ules in question, and they estimate their diameter 
 at less than goo^floft th of an inch. Under the high- 
 est powers of the microscope, at present applicable, 
 such specks are hardly discernible. Nevertheless, 
 particles of this size are massive when compared to 
 physical molecules; whence there is no reason to 
 doubt that each, small as it is, may have a mole- 
 cular structure sufficiently complex to give rise to 
 the phenomena of life. And, as a matter of fact, 
 by patient watching of the place at which these in- 
 finitesimal living particles were discharged, our 
 observers assured themselves of their growth and 
 development into new monads. In about four 
 hours from their being set free, they had attained 
 a sixth of the length of the parent, with the char- 
 acteristic cilia, though at first they were quite mo- 
 tionless; and, in four hours more, they had at- 
 tained the dimensions and exhibited all the activ- 
 ity of the adult. These inconceivably minute par- 
 ticles are therefore the germs of the Heteromita; 
 and from the dimensions of these germs it is easily 
 shown that the body formed by conjugation may, 
 at a low estimate, have given exit to thirty thou- 
 sand of them; a result of a matrimonial process 
 whereby the contracting parties, without a meta- 
 phor, " become one flesh," enough to make a Mal- 
 thusian despair of the future of the Universe. 
 
 I am not aware that the investigators from 
 whom I have borrowed this history have endeav- 
 
VI ANIMALS AND PLANTS. 187 
 
 oured to ascertain whether their monads take solid 
 nutriment or not; so that though they help us 
 Tery much to fill up the blanks in the history of 
 my Heteromita, their observations throw no light 
 on the problem we are trying to solve — Is it an 
 animal or is it a plant? 
 
 Undoubtedly it is possible to bring forward 
 very strong arguments in favour of regarding Hete- 
 romita as a plant. 
 
 For example, there is a Fungus, an obscure and 
 almost microscopic mould, termed Peronospora in- 
 festans. Like many other Fungi, the Peronosporce 
 are parasitic upon other plants; and this particu- 
 lar Peronospora happens to have attained much no- 
 toriety and political importance, in a way not with- 
 out a parallel in the career of notorious politicians, 
 namely, by reason of the frightful mischief it has 
 done to mankind. For it is this Fungus which is 
 the cause of the potato disease; and, therefore, 
 Peronospora infestans (doubtless of exclusively 
 Saxon origin, though not accurately known to be 
 so) brought about the Irish famine. The plants 
 afflicted with the malady are found to be infested 
 by a mould, consisting of fine tubular filaments, 
 termed hyphcB, which burrow through the sub- 
 stance of the potato plant, and appropriate to 
 themselves the substance of their host; while, at 
 the same time, directly or indirectly, they set up 
 chemical changes by which even its woody frame- 
 work becomes blackened, sodden, and withered. 
 
188 ANIMALS AND PLANTS. vi 
 
 In structure, however, the Peronospora is as 
 much a mould as the common Penicilliumj and 
 just as the PenicilKum multipUes by the breaking 
 up of its hyphse into separate rounded bodies, the 
 spores; so, in the Peronospora, certain of the 
 hyphse grow out into the air through the inter- 
 stices of the superficial cells of the potato plant, 
 and develop spores. Each of these hyphse usually 
 gives off several branches. The ends of the 
 branches dilate and become closed sacs, which 
 eventually drop off as spores. The spores falling 
 on some part of the same potato plant, or carried 
 by the wind to another, may at once germinate, 
 throwing out tubular prolongations which become 
 hyphse, and burrow into the substance of the plant 
 attacked. But, more commonly, the contents 
 of the spore divide into six or eight separate por- 
 tions. The coat of the spore gives way, and each 
 portion then emerges as an independent organism, 
 which has the shape of a bean, rather narrower at 
 one end than the other, convex on one side, and 
 depressed or concave on the opposite. From the 
 depression, two long and delicate cilia proceed, 
 one shorter than the other, and directed forwards. 
 Close to the origin of these cilia, in the substance 
 of the body, is a regularly pulsating, contractile 
 vacuole. The shorter cilium vibrates actively, 
 and effects the locomotion of the organism, while 
 the other trails behind; the whole body rolling on 
 its axis with its pointed end forwards. 
 
VI ANIMALS AND PLANTS. 189 
 
 The eminent botanist, De Bary, who was not 
 thinking of our problem, tells us, in describing the 
 movements of these " Zoopores," that, as they 
 swim about, " foreign bodies are carefully avoided, 
 and the whole movement has a deceptive likeness 
 to the voluntary changes of place which are ob- 
 served in microscopic animals." 
 
 After swarming about in this way in the moist- 
 ure on the surface of a leaf or stem (which, film 
 though it may be, is an ocean to such a fish) for 
 half an hour, more or less, the movement of the 
 zoospore becomes slower, and is limited to a slow 
 turning upon its axis, without change of place. 
 It then becomes quite quiet, the cilia disappear, 
 it assumes a spherical form, and surrounds itself 
 with a distinct, though delicate, membranous coat. 
 A protuberance then grows out from one side 
 of the sphere, and rapidly increasing in length, 
 assumes the character of a hypha. The latter 
 penetrates into the substance of the potato plant, 
 either by entering a stomate, or by boring through 
 the wall of an epidermic cell, and ramifies, as a my- 
 celium, in the substance of the plant, destroying 
 the tissues with which it comes in contact. As 
 these processes of multiplication take place very 
 rapidly, millions of spores are soon set free from 
 a single infested plant; and, from their minute- 
 ness, they are readily transported by the gentlest 
 breeze. Since, again, the zoospores set free from 
 each spore, in virtue of their powers of locomotion, 
 
190 ANIMALS AND PLANTS. vi 
 
 swiftly disperse themselves over the surface, it is 
 BO wonder that the infection, once started, soon 
 spreads from field to field, and extends its ravages 
 over a whole country. 
 
 However, it does not enter into my present 
 plan to treat of the potato disease, instructively as 
 its history bears upon that of other epidemics; and 
 I have selected the case of the Peronospora sim- 
 ply because it affords an example of an organism, 
 which, in one stage of its existence, is truly a 
 " Monad," indistinguishable by any important 
 character from our Heteromita, and extraordinarily 
 like it in some respects. And yet this " Monad " 
 can be traced, step by step, through the series of 
 metamorphoses which I have described, until it 
 assumes the features of an organism, which is as 
 much a plant as is an oak or an elm. 
 
 Moreover, it would be possible to pursue the 
 analogy farther. Under certain circumstances, a 
 process of conjugation takes place in the Perono- 
 spora. Two separate portions of its protoplasm 
 become fused together, surround themselves with 
 a thick coat, and give rise to a sort of vegetable 
 egg called an oospore. After a period of rest, the 
 contents of the oospore break up into a number 
 of zoospores like those already described, each of 
 which, after a period of activity, germinates in the 
 ordinary way. This process obviously corresponds 
 with the conjugation and subsequent setting free 
 of germs in the Heteromita. 
 
VI ANIMALS AND PLANTS. 191 
 
 But it may be said that the Peronospora is, 
 after all, a questionable sort of plant; that it seems 
 to be wanting in the manufacturing power, select- 
 ed as the main distinctive character of vegetable 
 life, or, at any rate, that there is no proof that 
 it does not get its protein matter ready made from 
 the potato plant. 
 
 Let us, therefore, take a case which is not open 
 to these objections. 
 
 There are some small plants known to botanists 
 as members of the genus Cohochcete, which, with- 
 out being truly parasitic, grow upon certain water- 
 weeds, as lichens grow upon trees. The little 
 plant has the form of an elegant green star, the 
 branching arms of which are divided into cells. 
 Its greenness is due to its chlorophyll, and it un- 
 doubtedly has the manufacturing power in full de- 
 gree, decomposing carbonic acid and setting oxy- 
 gen free, binder the influence of sunlight. But 
 the protoplasmic contents of some of the cells of 
 which the plant is made up occasionally divide, by 
 a method similar to that which effects the division 
 of the contents of the Peronospora spore; and the 
 severed portions are then set free as active monad- 
 like zoospores. Each is oval and is provided at 
 one extremity with two long active cilia. Pro- 
 pelled by these, it swims about for a longer or 
 shorter time, but at length comes to a state of 
 rest and gradually grows into a Coleoclicete. More- 
 over, as in the Peronospora, conjugation may take 
 
192 ANIMALS AND PLANTS. vi 
 
 place and result in an oospore; the contents of 
 which divide and are set free as monadiform 
 germs. 
 
 If the whole history of the zoospores of Perono- 
 spora and of Coleochcete were unknown, they would 
 undoubtedly he classed among " Monads " with 
 the same right as Heteromita; why then may not 
 Heteromita be a plant, even though the cycle of 
 forms through which it passes shows no terms 
 quite so complex as those which occur in Perono- 
 spora and Coleochcete? And, in fact, there are 
 some green organisms, in every respect charac- 
 teristically plants, such as Chlamydomonas, and 
 the common Volvox, or so-called " Globe animal- 
 cule," which run through a cycle of forms of just 
 the same simple character as those of the Hete- 
 romita. 
 
 The name of Chlamydomonas is applied to cer- 
 tain microscopic green bodies, each of which con- 
 sists of a protoplasmic central substance invested 
 by a structureless sac. The latter contains cellu- 
 lose, as in ordinary plants; and the chlorophyll 
 which gives the green colour enables the Chlamy- 
 domonas to decompose carbonic acid and fix carbon 
 as they do. Two long cilia protrude through the 
 cell-wall, and effect the rapid locomotion of this 
 " monad," which, in all respects except its mobil- 
 ity, is characteristically a plant. Under ordinary 
 circumstances, the Chlamydomonas multiplies by 
 simple fission, each splitting into two or into four 
 
VI ANIMALS AND PLANTS. 193 
 
 parts, which separate and become independent or- 
 ganisms. Sometimes, however, the Chlamydo- 
 monas divides into eight parts, each of which is 
 provided with four instead of two cilia. These 
 " zoospores " conjugate in pairs, and give rise to 
 quiescent bodies, which multiply by division, and 
 eventually pass into the active state. 
 
 Thus, so far as outward form and the general 
 character of the cycle of modifications, through 
 which the organism passes in the course of its life, 
 are concerned, the resemblance between Chlamy- 
 domonas and Heteromita is of the closest descrip- 
 tion. And on the face of the matter there is no 
 ground for refusing to admit that Heteromita may 
 be related to Chlamydomonas, as the colourless 
 fungus is to the green alga. Volvox may be com- 
 pared to a hollow sphere, the wall of which is 
 made up of coherent Chlamydomonads; and which 
 progresses with a rotating motion effected by the 
 paddling of the multitudinous pairs of cilia which 
 project from its surface. Each Yolvox-raonaA, 
 moreover, possesses a red pigment spot, like the 
 simplest form of eye known among animals. The 
 methods of fissive multiplication and of conjuga- 
 tion observed in the monads of this locomotive 
 globe are essentially similar to those observed in 
 Chlamydomonas; and, though a hard battle has 
 been fought over it, Volvox is now finally surren- 
 dered to the Botanists. 
 
 Thus there is really no reason why Heteromita 
 199 
 
194 ANIMALS AND PLANTS. vi 
 
 may not be a plant; and this conclusion would be 
 very satisfactory, if it were not equally easy to 
 show that there is really no reason why it should 
 not be an animal. For there are numerous or- 
 ganisms presenting the closest resemblance to 
 Heteromita, and, like it, grouped under the general 
 name of "Monads," which, nevertheless, can be 
 observed to take in solid nutriment, and which, 
 therefore, have a virtual, if not an actual, mouth 
 and digestive cavity, and thus come under Cu- 
 vier's definition of an animal. Numerous forms 
 of such animals have been described by Ehren- 
 berg, Dujardin, H. James Clark, and other writers 
 on the Infusoria. Indeed, in another infusion 
 of hay in which my Heteromita lens occurred, 
 there were innumerable such infusorial animal- 
 cules belonging to the well-known species Colpoda 
 cucuUus.* 
 
 Full-sized specimens of this animalcule attain a 
 length of between ^^th or j^^th of an inch, so 
 that it may have ten times the length and a thou- 
 sand times the mass of a Heteromita. In shape, it 
 it not altogether unlike Heteromita. The small 
 end, however, is not produced into one long cilium, 
 but the general surface of the body is covered with 
 small actively vibrating ciliary organs, which are 
 only longest at the small end. At the point which 
 answers to that from which the two cilia arise in 
 
 * Excellently described by Stein, almost all of whose 
 statements I have verified. 
 
VI ANIMALS AND PLANTS. 195 
 
 Heteromita, there is a conical depression, the 
 mouth; and, in young specimens, a tapering fila- 
 ment, which reminds one of the posterior cilium 
 of Heteromita, projects from this region. 
 
 The body consists of a soft granular proto- 
 plasmic substance, the middle of which is occupied 
 by a large oval mass called the " nucleus "; while, 
 at its hinder end, is a " contractile vacuole," con- 
 spicuous by its regular rhythmic appearances and 
 disappearances. Obviously, although the Colpoda 
 is not a monad, it differs from one only in subor- 
 dinate details. Moreover, under certain condi- 
 tions, it becomes quiescent, encloses itself in a deli- 
 cate case or cyst, and then divides into two, four, or 
 more portions, which are eventually set free and 
 swim about as active Colpodce. 
 
 But this creature is an unmistakable animal, 
 and full-sized Colpodce may be fed as easily as one 
 feeds chickens. It is only needful to diffuse very 
 finely ground carmine through the water in which 
 they live, and, in a very short time, the bodies of 
 the Colpodce are stuffed with the deeply-coloured 
 granules of the pigment. 
 
 And if this were not sufficient evidence of the 
 animality of Colpoda, there comes the fact that it 
 is even more similar to another well-known ani- 
 malcule, Paramcecium, than it is to a monad. 
 But Paramcecium is so huge a creature compared 
 with those hitherto discussed — it reaches yts^^ ^^ 
 an inch or more in length — ^that there is no diffi- 
 
196 ANIMALS AND PLANTS. ti 
 
 culty in making out its organisation in detail; 
 and in proving that it is not only an animal, but 
 that it is an animal which possesses a somewhat 
 complicated organisation. For example, the sur- 
 face layer of its body is different in structure from 
 the deeper parts. There are two contractile vacu- 
 oles, from each of which radiates a system of ves- 
 sel-like canals; and not only is there a conical de- 
 pression continuous with a tube, which serve as 
 mouth and gullet, but the food ingested takes a 
 definite course, and refuse is rejected from a defi- 
 nite region. Nothing is easier than to feed these 
 animals, and to watch the particles of indigo or 
 carmine accumulate at the lower end of the gullet. 
 From this they gradually project, surrounded by 
 a ball of water, which at length passes with a jerk, 
 oddly simulating a gulp, into the pulpy central 
 substance of the body, there to circulate up one 
 side and down the other, until its contents are 
 digested and assimilated. Nevertheless, this com- 
 plex animal multiplies by division, as the monad 
 does, and like the monad, undergoes conjugation. 
 It stands in the same relation to Heteromita on 
 the animal side, as Coleochwte does on the plant 
 side. Start from either, and such an insensible 
 series of gradations leads to the monad that it is 
 impossible to say at any stage of the progress where 
 the line between the animal and the plant must 
 be drawn. 
 
 There is reason to think that certain organisms 
 
VI ANIMALS AND PLANTS. 197 
 
 which pass through a monad stage of existence, 
 such as the Myxomycetes, are, at one time of their 
 lives, dependent upon external sources for their 
 protein matter, or are animals; and, at another 
 period, manufacture it, or are plants. And seeing 
 that the whole progress of modern investigation is 
 in favour of the doctrine of continuity, it is a fair 
 and probable speculation — though only a specu- 
 lation — that, as there are some plants which can 
 manufacture protein out of such apparently in- 
 tractable mineral matters as carbonic acid, water, 
 nitrate of ammonia, metallic and earthy salts; 
 while others need to be supplied with their carbon 
 and nitrogen in the somewhat less raw form of 
 tartrate of ammonia and allied compounds; so 
 there may be yet others, as is possibly the case 
 with the true parasitic plants, which can only 
 manage to put together materials still better pre- 
 pared — still more nearly approximated to protein 
 — until we arrive at such organisms as the Psoro- 
 spermicB and the Panhistophyton, which are as 
 much animal as vegetable in structure, but are ani- 
 mal in their dependence on other organisms for 
 their food. 
 
 The singular circumstance observed by Meyer, 
 that the Torula of yeast, though an indubitable 
 plant, still flourishes more vigorously when sup- 
 plied with the complex nitrogenous substance, pep- 
 sin; the probability that the Peronospora is nour- 
 ished directly by the protoplasm of the potato- 
 
198 ANIMALS AND PLANTS. vi 
 
 plant; and the wonderful facts which have recent- 
 ly been brought to light respecting insectivorous 
 plants, all favour this view; and tend to the con- 
 clusion that the difference between animal and 
 plant is one of degree rather than of kind, and 
 that the problem whether, in a given case, an 
 organism is an animal or a plant, may be essen- 
 tially insoluble. 
 
VII. 
 
 A LOBSTEE; OE, THE STUDY OP 
 ZOOLOGY. 
 
 [1861.] 
 
 Natural History is the name familiarly ap- 
 plied to the study of the properties of such natural 
 bodies as minerals, plants, and animals; the sci- 
 ences which embody the knowledge man has ac- 
 quired upon these subjects are commonly termed 
 Natural Sciences, in contradistinction to other so- 
 called " physical " sciences; and those who de- 
 vote themselves especially to the pursuit of such 
 sciences have been and are commonly termed 
 " Naturalists." 
 
 Linnaeus was a naturalist in this wide sense, 
 and his " Systema Naturae " was a work upon 
 natural history, in the broadest acceptation of 
 the term; in it, that great methodising spirit em- 
 bodied all that was known in his time of the dis- 
 tinctive characters of minerals, animals, and 
 plants. But the enormous stimulus which Lin- 
 naeus gave to the investigation of nature soon ren- 
 
 199 
 
200 THE STUDY OP ZOOLOaY. vii 
 
 dered it impossible that any one man should write 
 another " Systema Naturae," and extremely diffi- 
 cult for any one to become even a naturalist such 
 as Linnseus was. 
 
 Great as have been the advances made by all 
 the three branches of science, of old included 
 under the title of natural history, there can be no 
 doubt that zoology and botany have grown in an 
 enormously greater ratio than mineralogy; and 
 hence, as I suppose, the name of " natural history " 
 has gradually become more and more definitely at- 
 tached to these prominent divisions of the subject, 
 and by " naturalist " people have meant more and 
 more distinctly to imply a student of the structure 
 and function of living beings. 
 
 However this may be, it is certain that the ad- 
 vance of knowledge has gradually widened the dis- 
 tance between mineralogy and its old associates, 
 while it has drawn zoology and botany closer to- 
 gether; so that of late years it has been found con- 
 venient (and indeed necessary) to associate the 
 sciences which deal with vitality and all its phe- 
 nomena under the common head of " biology; " 
 and the biologists have come to repudiate any 
 blood-relationship with their foster-brothers, the 
 mineralogists. 
 
 Certain broad laws have a general application 
 throughout both the animal and the vegetable 
 worlds, but the ground common to these kingdoms 
 of nature is not of very wide extent, and the multi- 
 
VII THE STUDY OP ZOOLOGY, 201 
 
 plicity of details is so great, that the student of 
 living beings finds himself obliged to devote his 
 attention exclusively either to the one or the other. 
 If he elects to study plants, under any aspect, we 
 know at once what to call him. He is a botanist, 
 and his science is botany. But if the investigation 
 of animal life be his choice, the name generally 
 applied to him will vary according to the kind of 
 animals he studies, or the particular phenomena of 
 animal life to which he confines his attention. If 
 the study of man is his object, he is called an 
 anatomist, or a physiologist, or an ethnologist; but 
 if he dissects animals, or examines into the mode 
 in which their functions are performed, he is a 
 comparative anatomist or comparative physiologist. 
 If he turns his attention to fossil animals, he is a 
 palaeontologist. If his mind is more particularly 
 directed to the specific description, discrimination, 
 classification, and the distribution of animals, he is 
 termed a zoologist. 
 
 For the purpose of the present discourse, how- 
 ever, I shall recognise none of these titles save the 
 last, which I shall employ as the equivalent of 
 botanist, and I shall use the term zoology as 
 denoting the whole doctrine of animal life, in con- 
 tradistinction to botany, which signifies the whole 
 doctrine of vegetable life. 
 
 Employed in this sense, zoology, like botany, is 
 divisible into three great but subordinate sciences, 
 morphology, physiology, and distribution, each of 
 
202 THE STUDY OF ZOOLOGY. tii 
 
 which may, to a very great extent, be studied in- 
 dependently of the other. 
 
 Zoological morphology is the doctrine of ani- 
 mal form or structure. Anatomy is one of its 
 branches; development is another; while classifi- 
 cation is the expression of the relations which dif- 
 ferent animals bear to one another, in respect of 
 their anatomy and their development. 
 
 Zoological distribution is the study of animals 
 in relation to the terrestrial conditions which ob- 
 tain now, or have obtained at any previous epoch 
 of the earth's history. 
 
 Zoological physiology, lastly, is the doctrine of 
 the functions or actions of animals. It regards 
 animal bodies as machines impelled by certain 
 forces, and performing an amount of work which 
 can be expressed in terms of the ordinary forces of 
 nature. The final object of physiology is to de- 
 duce the facts of morphology, on the one hand, 
 and those of distribution on the other, from the 
 laws of the molecular forces of matter. 
 
 Such is the scope of zoology. But if I were to 
 content myself with the enunciation of these dry 
 definitions, I should ill exemplify that method of 
 teaching this branch of physical science, which it 
 is my chief business to-night to recommend. Let 
 us turn away then from abstract definitions. Let 
 us take some concrete living thing, some animal, 
 the commoner the better, and let us see how the 
 application of common sense and common logic 
 
VII THE STUDY OF ZOOLOGY. 203 
 
 to the obvious facts it presents, inevitably leads ns 
 into all these branches of zoological science. 
 
 I have before me a lobster. When I examine 
 it, what appears to be the most striking character 
 it presents? Why, I observe that this part which 
 we call the tail of the lobster, is made up of six dis- 
 tinct hard rings and a seventh terminal piece. If 
 I separate one of the middle rings, say the third, I 
 find it carries upon its under surface a pair of 
 limbs or appendages, each of which consists of a 
 stalk and two terminal pieces. So that I can rep- 
 resent a transverse section of the ring and its 
 appendages upon the diagram board in this way. 
 
 If I now take the fourth ring, I find it has the 
 same structure, and so have the fifth and the sec- 
 ond; so that, in each of these divisions of the tail, 
 I find parts which correspond with one another, a 
 ring and two appendages; and in each appendage 
 a stalk and two end pieces. These corresponding 
 parts are called, in the technical language of anat- 
 omy, " homologous parts." The ring of the third 
 division is the " homologue " of the ring of the 
 fifth, the appendage of the former is the homo- 
 logue of the appendage of the latter. And, as 
 each division exhibits corresponding parts in cor- 
 responding places, we say that all the divisions are 
 constructed upon the same plan. But now let 
 us consider the sixth division. It is similar to, 
 and yet different from, the others. The ring is 
 essentially the same as in the other divisions; but 
 
204 THE STUDY OP ZOOLOGY. vii 
 
 the appendages look at first as if they were very 
 different; and yet when we regard them closely^ 
 what do we find? A stalk and two terminal divi- 
 sions, exactly as in the others, but the stalk is very 
 short and very thick, the terminal divisions are 
 very broad and flat, and one of them is divided 
 into two pieces. 
 
 I may say, therefore, that the sixth segment is 
 like the others in plan, but that it is modified in 
 its details. 
 
 The first segment is like the others, so far as its 
 ring is concerned, and though its appendages dif- 
 fer from any of those yet examined in the simplic- 
 ity of their structure, parts corresponding with the 
 stem and one of the divisions of the appendages 
 of the other segments can be readily discerned in 
 them. 
 
 Thus it appears that the lobster's tail is com- 
 posed of a series of segments which are funda- 
 mentally similar, though each presents peculiar 
 modifications of the plan common to all. But 
 when I turn to the forepart of the body I see, at 
 first, nothing but a great shield-like shell, called 
 technically the " carapace," ending in front in a 
 sharp spine, on either side of which are the curi- 
 ous compound eyes, set upon the ends of stout 
 movable stalks. Behind these, on the under side 
 of the body, are two pairs of long feelers, or anten- 
 nae, followed by six pairs of jaws folded against 
 one another over the mouth, and five pairs of 
 
VII THE STUDY OP ZOOLOGY. 205 
 
 legs, the foremost of these being the great pinch- 
 ers, or claws, of the lobster. 
 
 It looks, at first, a little hopeless to attempt to 
 find in this complex mass a series of rings, each 
 with its pair of appendages, such as I have shown 
 you in the abdomen, and yet it is not difficult to 
 demonstrate their existence. Strip off the legs, 
 and you will find that each pair is attached to a 
 very definite segment of the under wall of the 
 body; but these segments, instead of being the 
 lower part of free rings, as in the tail, are such 
 parts of rings which are all solidly united and 
 bound together; and the like is true of the Jaws, 
 the feelers, and the eye-stalks, every pair of which 
 is borne upon its own special segment. Thus the 
 conclusion is gradually forced upon us, that the 
 body of the lobster is composed of as many rings as 
 there are pairs of appendages, namely, twenty in 
 all, but that the six hindmost rings remain free 
 and movable, while the fourteen front rings be- 
 come firmly soldered together, their backs forming 
 one continuous shield — the carapace. 
 
 Unity of plan, diversity in execution, is the 
 lesson taught by the study of the rings of the body, 
 and the same instruction is given still more em- 
 phatically by the appendages. If I examine the 
 outermost jaw I find it consists of three distinct 
 portions, an inner, a middle, and an outer, mount- 
 ed upon a common stem; and if I compare this 
 jaw with the legs behind it, or the jaws in front of 
 
206 THE STUDY OF ZOOLOGY. vii 
 
 it, I find it quite easy to see, that, in the legs, it is 
 the part of the appendage which corresponds with 
 the inner division, which becomes modified into 
 what we know familiarly as the "leg," while the 
 middle division disappears, and the outer division 
 is hidden under the carapace. Nor is it more diffi- 
 cult to discern that, in the appendages of the tail, 
 the middle division appears again and the outer 
 vanishes; while, on the other hand, in the fore- 
 most jaw, the so-called mandible, the inner divi- 
 sion only is left; and, in the same way, the parts of 
 the feelers and of the eye-stalks can be identified 
 with those of the legs and jaws. 
 
 But whither does all this tend? To the very 
 remarkable conclusion that a unity of plan, of the 
 same kind as that discoverable in the tail or ab- 
 domen of the lobster, pervades the whole organisa- 
 tion of its skeleton, so that I can return to the dia- 
 gram representing any one of the rings of the 
 tail, which I drew upon the board, and by adding a 
 third division to each appendage, I can use it as a 
 sort of scheme or plan of any ring of the body. I 
 can give names to all the parts of that figure, and 
 then if I take any segment of the body of the 
 lobster, I can point out to you exactly what modi- 
 fication the general plan has undergone in that 
 particular segment; what part has remained mova- 
 ble, and what has become fixed to another; what 
 has been excessively developed and metamor- 
 phosed and what has been suppressed. 
 
VII THE STUDY OP ZOOLOGY. 207 
 
 But I imagine I hear the question. How is all 
 this to be tested? No doubt it is a pretty and in- 
 genious way of looking at the structure of any 
 animal; but is it anything more? Does Nature 
 acknowledge, in any deeper way, this unity of plan 
 we seem to trace? 
 
 The objection suggested by these questions is a 
 very valid and important one, and morphology 
 was in an unsound state so long as it rested upon 
 the mere perception of the analogies which obtain 
 between fully formed parts. The unchecked in- 
 genuity of speculative anatomists proved itself 
 fully competent to spin any number of contradic- 
 tory hypotheses out of the same facts, and endless 
 morphological dreams threatened to supplant sci- 
 entific theory. 
 
 Happily, however, there is a criterion of mor- 
 phological truth, and a sure test of all homologies. 
 Our lobster has not always been what we see it; 
 it was once an egg, a semifluid mass of yolk, not so 
 big as a pin's head, contained in a transparent 
 membrane, and exhibiting not the least trace of 
 any one of those organs, the multiplicity and com- 
 plexity of which, in the adult, are so surprising. 
 After a time, a delicate patch of cellular membrane 
 a,ppeared upon one face of this yolk, and that 
 patch was the foundation of the whole creature, 
 the clay out of which it would be moulded. 
 Gradually investing the yolk, it became subdivided 
 by transverse constrictions into segments^ the fore- 
 
208 THE STUDY OF ZOOLOaY. vii 
 
 runners of the rings of the hody. Upon the ven- 
 tral surface of each of the rings thus sketched out, 
 a pair of bud-like prominences made their appear- 
 ance — the rudiments of the appendages of the 
 ring. At first, all the appendages were alike, but, 
 as they grew, most of them became distinguished 
 into a stem and two terminal divisions, to which, 
 in the middle part of the body, was added a third 
 outer division; and it was only at a later period, 
 that by the modification, or absorption, of certain 
 of these primitive constituents, the limbs acquired 
 their perfect form. 
 
 Thus the study of development proves that the 
 doctrine of unity of plan is not merely a fancy, 
 that it is not merely one way of looking at the 
 matter, but that it is the expression of deep-seated 
 natural facts. The legs and jaws of the lobster 
 may not merely be regarded as modifications of a 
 common type, — in fact and in nature they are so, — 
 the leg and the jaw of the young animal being, at 
 first, indistinguishable. 
 
 These are wonderful truths, the more so be- 
 cause the zoologist finds them to be of universal ap- 
 plication. The investigation of a polype, of a 
 snail, of a fish, of a horse, or of a man, would have 
 led us, though by a less easy path, perhaps, to ex- 
 actly the same point. Unity of plan everywhere 
 lies hidden under the mask of diversity of structure 
 — the complex is everywhere evolved out of the 
 simple. Every animal has at first the form of an 
 
vn THE STUDY OF ZOOLOGY, 209 
 
 egg, and every animal and every organic part, in 
 reaching its adult state, passes through conditions 
 common to other animals and other adult parts; 
 and this leads me to another point. I have hither- 
 to spoken as if the lobster were alone in the world, 
 but, as I need hardly remind you, there are myri- 
 ads of other animal organisms. Of these, some, 
 such as men, horses, birds, fishes, snails, slugs, 
 oysters, corals, and sponges, are not in the least 
 like the lobster. But other animals, though they 
 may differ a good deal from the lobster, are yet 
 either very like it, or are like something that is 
 like it. The crayfish, the rock lobster, and the 
 prawn, and the shrimp, for example, however dif- 
 ferent, are yet so like lobsters, that a child would 
 group them as of the lobster kind, in contradistinc- 
 tion to snails and slugs; and these last again would 
 form a kind by themselves, in contradistinction to 
 cows, horses, and sheep, the cattle kind. 
 
 But this spontaneous grouping into " kinds " is 
 the first essay of the human mind at classification, 
 or the calling by a common name of those things 
 that are alike, and the arranging them in such a 
 manner as best to suggest the sum of their like- 
 nesses and unlikenesses to other things. 
 
 Those kinds which include no other subdivi- 
 sions than the sexes, or various breeds, are tailed, 
 in technical language, species. The English lob- 
 ster is a species, our crayfish is another, our prawn 
 
 is another. In other countries, however, there are 
 200 
 
210 THE STUDY OF ZOOLOGY. th 
 
 lobsters, crayfish, and prawns, very like ours, and 
 yet presenting sufficient differences to deserve dis- 
 tinction. Naturalists, therefore, express this re- 
 semblance and this diversity by grouping them as 
 distinct species of the same " genus." But the 
 lobster and the crayfish, though belonging to dis- 
 tinct genera, have many features in common, and 
 hence are grouped together in an assemblage which 
 is called a family. More distant resemblances 
 connect the lobster with the prawn and the crab, 
 which are expressed by putting all these into the 
 same order. Again, more remote, but still very 
 definite, resemblances unite the lobster with the 
 woodlouse, the king crab, the water flea, and the 
 barnacle, and separate them from all other ani- 
 mals; whence they collectively constitute the 
 larger group, or class, Crustacea. But the Crusta- 
 cea exhibit many peculiar features in common with 
 insects, spiders, and centipedes, so that these are 
 grouped into the still larger assemblage or " prov- 
 ince " Articulata; and, finally, the relations which 
 these have to worms and other lower animals, are 
 expressed by combining the whole vast aggregate 
 into the sub-kingdom of Annulosa. 
 
 If I had worked my way from a sponge instead 
 of a lobster, I should have found it associated, by 
 like ties, with a great number of other animals into 
 the sub-kingdom Protozoa; if I had selected a 
 fresh-water polype or a coral, the members of what 
 naturalists term the sub-kingdom Coelenterata, 
 
Til THE STUDY OF ZOOLOGY. 211 
 
 would have grouped themselves around my type; 
 had a snail been chosen, the inhabitants of all uni- 
 valve and bivalve, land and water, shells, the lamp 
 shells, the squids, and the sea-mat would have 
 gradually linked themselves on to it as members 
 of the same sub-kingdom of Mollusca; and finally, 
 starting from man, I should have been compelled 
 to admit first, the ape, the rat, the horse, the dog, 
 into the same class; and then the bird, the croco- 
 dile, the turtle, the frog, and the fish, into the 
 same sub-kingdom of Vertebraia. 
 
 And' if I had followed out all these various lines 
 of classification fully, I should discover in the end 
 that there was no animal, either recent or fossil, 
 which did not at once fall into one or other of 
 these sub-kingdoms. In other words, every ani- 
 mal is organised upon one or other of the five, or 
 more, plans, the existence of which renders our 
 classification possible. And so definitely and pre- 
 cisely marked is the structure of each animal, that, 
 in the present state of our knowledge, there is not 
 the least evidence to prove that a form, in the 
 slightest degree transitional between any of the 
 two groups Vertebrata, Annulosa, Mollusca, and 
 Ccelenterata, either exists, or has existed, during 
 that period of the earth's history which is recorded 
 by the geologist.* ll^evertheless, you must not for 
 a moment suppose, because no such transitional 
 
 [* The different grouping necessitated by later knowl- 
 edge does not affect the principle of the argument. — 
 1894.] 
 
212 THE STUDY OP ZOOLOGY. vii 
 
 forms are known, that the members of the sub- 
 kingdoms are disconnected from, or independent 
 of, one another. On the contrary, in their earliest 
 condition they are all similar, and the primordial 
 germs of a man, a dog, a bird, a fish, a beetle, a 
 snail, and a polype are, in no essential structural 
 respects, distinguishable. 
 
 In this broad sense, it may with truth be said, 
 that all living animals, and all those dead faunaa 
 which geology reveals, are bound together by an 
 all-pervading unity of organisation, of the same 
 character, though not equal in degree, to that 
 which enables us to discern one and the same plan 
 amidst the twenty different segments of a lobster's 
 body. Truly it has been said, that to a clear eye 
 the smallest fact is a window through which the 
 Infinite may be seen. 
 
 Turning from these purely morphological con- 
 siderations, let us now examine into the manner in 
 which the attentive study of the lobster impels us 
 into other lines of research. 
 
 Lobsters are found in all the European seas; 
 but on the opposite shores of the Atlantic and in 
 the seas of the southern hemisphere they do not 
 exist. They are, however, represented in these 
 regions by very closely allied, but distinct forms — 
 the Homarus Americanus and the Homarus Capen- 
 sis: so that we may say that the European has 
 one species of Homarus; the American, another; 
 the African, another; and thus the remarkable 
 
VII THE STUDY OF ZOOLOaY. 213 
 
 facts of geographical distribution begin to dawn 
 upon us. 
 
 Again, if we examine the contents of the 
 earth's crust, we shall find in the latter of those de- 
 posits, which have served as the great burying 
 grounds of past ages, numberless lobster-like ani- 
 mals, but none so similar to our living lobster as to 
 make zoologists sure that they belonged even to 
 the same genus. If we go still further back in 
 time, we discover, in the oldest rocks of all, the re- 
 mains of animals, constructed on the same general 
 plan as the lobster, and belonging to the same 
 great group of Crustacea; but for the most part 
 totally different from the lobster, and indeed from 
 any other living form of crustacean; and thus we 
 gain a notion of that successive change of the 
 animal population of the globe, in past ages, 
 which is the most striking fact revealed by ge- 
 ology. 
 
 Consider now, where our inquiries have led us. 
 We studied our type morphologically when we 
 determined its anatomy and its development, and 
 when comparing it, in these respects, with other 
 animals, we made out its place in a system of classi- 
 fication. If we were to examine every animal in 
 a similar manner, we should establish a complete 
 body of zoological morphology. 
 
 Again, we investigated the distribution of our 
 type in space and in time, and, if the like had 
 been done with every animal, the sciences of geo- 
 
214 THE STUDY OF ZOOLOGY. vn 
 
 graphical and geological distribution would have 
 attained their limit. 
 
 But you will observe one remarkable circum- 
 stance, that, up to this point, the question of the 
 life of these organisms has not come under con- 
 sideration. Morphology and distribution might 
 be studied almost as well, if animals and plants 
 were a peculiar kind of crystals, and possessed 
 none of those functions which distinguish living 
 beings so remarkably. But the facts of morphol- 
 ogy and distribution have to be accounted for, and 
 the science, the aim of which it is to account for 
 them, is Physiology. 
 
 Let us return to our lobster once more. If we 
 watched the creature in its native element, we 
 should see it climbing actively the submerged 
 rocks, among which it delights to live, by means of 
 its strong legs; or swimming by powerful strokes 
 of its great tail, the appendages of the sixth Joint 
 of which are spread out into a broad fan-like pro- 
 peller: seize it, and it will show you that its great 
 claws are no mean weapons of offence; suspend a 
 piece of carrion among its haunts, and it will 
 greedily devour it, tearing and crushing the flesh 
 by means of its multitudinous jaws. 
 
 Suppose that we had known nothing of the 
 lobster but as an inert mass, an organic crystal, if 
 I may use the phrase, and that we could suddenly 
 see it exerting all these powers, what wonderful 
 new ideas and new questions would arise in our 
 
VII THE STUDY OF ZOOLOGY. 215 
 
 minds! The great new question would be, " How 
 does all this take place?" The chief new idea 
 would be, the idea of adaptation to purpose, — the 
 notion, that the constituents of animal bodies are 
 not mere unconnected parts, but organs working 
 together to an end. Let us consider the tail of 
 the lobster again from this point of view. Mor- 
 phology has taught us that it is a series of segments 
 composed of homologous parts, which undergo 
 various modifications — beneath and through which 
 a common plan of formation is discernible. But 
 if I look at the same part physiologically, I 
 see that it is a most beautifully constructed or- 
 gan of locomotion, by means of which the ani- 
 mal can swiftly propel itself either backwards or 
 forwards. 
 
 But how is this remarkable propulsive machine 
 made to perform its functions? If I were sud- 
 denly to kill one of these animals and to take out 
 all the soft parts, I should find*the shell to be per- 
 fectly inert, to have no more power of moving it- 
 self than is possessed by the machinery of a mill 
 when disconnected from its steam-engine or water- 
 wheel. But if I were to open it, and take out the 
 viscera only, leaving the white flesh, I should per- 
 ceive that the lobster could bend and extend its 
 tail as well as before. If I were to cut ofE the tail, 
 I should cease to find any spontaneous motion in 
 it; but on pinching any portion of the flesh, I 
 should observe that it underwent a very curious 
 
216 THE STUDY OP ZOOLOGY. vii 
 
 change — each fibre becoming shorter and thicker. 
 By this act of contraction, as it is termed, the 
 parts to which the ends of the fibre are attached 
 are, of course, approximated; and according to the 
 relations of their points of attachment to the cen- 
 tres of motions of the different rings, the bend- 
 ing or the extension of the tail results. Close 
 observation of the newly-opened lobster would 
 soon show that all its movements are due to the 
 same cause — the shortening and thickening of 
 these fleshy fibres, which are technically called 
 muscles. 
 
 Here, then, is a capital fact. The movements 
 of the lobster are due to muscular contractility. 
 But why does a muscle contract at one time and 
 not at another? Why does one whole group of 
 muscles contract when the lobster wishes to ex- 
 tend his tail, and another group when he desires 
 to bend it? What is it originates, directs, and 
 controls the motive power? 
 
 Experiment, the great instrument for the ascer- 
 tainment of truth in physical science, answers this 
 question for us. In the head of the lobster there 
 lies a small mass of that peculiar tissue which is 
 known as nervous substance. Cords of similar 
 matter connect this brain of the lobster, directly 
 or indirectly, with the muscles. Now, if these 
 communicating cords are cut, the brain remaining 
 entire, the power of exerting what we call vol- 
 untary motion in the parts below the section 
 
VII THE STUDY OF ZOOLOaY. 217 
 
 is destroyed; and, on the other hand, if, the 
 cords remaining entire, the brain mass be de- 
 stroyed, the same voluntary mobility is equally 
 lost. Whence the inevitable conclusion is, that 
 the power of originating these motions resides in 
 the brain and is propagated along the nervous 
 cords. 
 
 In the higher animals the phenomena which 
 attend this transmission have been investigated, 
 and the exertion of the peculiar energy which re- 
 sides in the nerves has been found to be accompa- 
 nied by a disturbance of the electrical state of 
 their molecules. 
 
 If we could exactly estimate the signification 
 of this disturbance; if we could obtain the value 
 of a given exertion of nerve force by determining 
 the quantity of electricity, or of heat, of which it 
 is the equivalent; if we could ascertain upon what 
 arrangement, or other condition of the molecules 
 of matter, the manifestation of the nervous and 
 muscular energies depends (and doubtless science 
 will some day or other ascertain these points), 
 physiologists would have attained their ultimate 
 goal in this direction; they would have determined 
 the relation of the motive force of animals to the 
 other forms of force found in nature; and if the 
 same process had been successfully performed 
 for all the operations which are carried on in, 
 and by, the animal frame, physiology would 
 be perfect, and the facts of morphology and dis- 
 
218 THE STUDY OP ZOOLOGY. tii 
 
 tribution would be deducible from the laws which 
 physiologists had established, combined with those 
 determining the condition of the surrounding uni- 
 verse. 
 
 There is not a fragment of the organism of this 
 humble animal whose study would not lead us 
 into regions of thought as large as those which I 
 have briefly opened up to you; but what I have 
 been saying, I trust, has not only enabled you to 
 form a conception of the scope and purport of 
 zoology, but has given you an imperfect example 
 of the manner in which, in my opinion, that sci- 
 ence, or indeed any physical science, may be best 
 taught. The great matter is, to make teaching 
 real and practical, by fixing the attention of the 
 student on particular facts; but at the same time 
 it should be rendered broad and comprehensive, 
 by constant reference to the generalisations of 
 which all particular facts are illustrations. The 
 lobster has served as a type of the whole animal 
 kingdom, and its anatomy and physiology have 
 illustrated for us some of the greatest truths of 
 biology. The student who has once seen for 
 himself the facts which I have described, has had 
 their relations explained to him, and has 
 clearly comprehended them, has, so far, a knowl- 
 edge of zoology, which is real and genuine, how- 
 ever limited it may be, and which is worth more 
 than all the mere reading knowledge of the 
 science he could ever acquire. His zoological 
 
VII THE STUDY OP ZOOLOGY. 219 
 
 information is, so far, knowledge and not mere 
 hearsay. 
 
 And if it were my business to fit you for the 
 certificate in zoological science granted by this de- 
 partment, I should pursue a course precisely simi- 
 lar in principle to that which I haye taken to- 
 night. I should select a fresh-water sponge, a 
 fresh-water polype or a Cyanwa, a fresh-water 
 mussel, a lobster, a fowl, as types of the five 
 primary divisions of the animal kingdom. I 
 should explain their structure very fully, and 
 show how each illustrated the great principles 
 of zoology. Having gone very carefully and 
 fully over this ground, I should feel that you had 
 a safe foundation, and I should then take you 
 in the same way, but less minutely, over simi- 
 larly selected illustrative types of the classes; and 
 then I should direct your attention to the special 
 forms enumerated under the head of types, in 
 this syllabus, and to the other facts there men- 
 tioned. 
 
 That would, speaking generally, be my plan. 
 But I have undertaken to explain to you the best 
 mode of acquiring and communicating a knowl- 
 edge of zoology, and you may therefore fairly ask 
 me for a more detailed and precise account of the 
 manner in which I should propose to furnish you 
 with the information I refer to. 
 
 My own impression is, that the best model for 
 all kinds of training in physical science is that 
 
220 THE STUDY OF ZOOLOGY". vii 
 
 afforded by the method of teaching anatomy, in 
 use in the medical schools. This method consists 
 of three elements — lectures, demonstrations, and 
 examinations. 
 
 The object of lectures is, in the first place, to 
 awaken the attention and excite the enthusiasm of 
 the student; and this, I am sure, may be effected 
 to a far greater extent by the oral discourse and 
 by the personal influence of a respected teacher 
 than in any other way. Secondly, lectures have 
 the double use of guiding the student to the salient 
 points of a subject, and at the same time forcing 
 him to attend to the whole of it, and not merely to 
 that part which takes his fancy. And lastly, lec- 
 tures afford the student the opportunity of seek- 
 ing explanations of those difficulties which will, 
 and indeed ought to, arise in the course of his 
 studies. 
 
 What books shall I read? is a question con- 
 stantly put by the student to the teacher. My 
 reply usually is, " None: write your notes out care- 
 fully and fully; strive to understand them thor- 
 oughly; come to me for the explanation of any- 
 thing you cannot understand; and I would rather 
 you did not distract your mind by reading." 
 A properly composed course of lectures ought 
 to contain fully as much matter as a student 
 can assimilate in the time occupied by its deliv- 
 ery; and the teacher should always recollect that 
 his business is to feed, and not to cram the Intel- 
 
VII THE STUDY OP ZOOLOGY. 221 
 
 leet. Indeed, I believe that a student who gains 
 from a course of lectures the simple habit of 
 concentrating his attention upon a definitely lim- 
 ited series of facts, until they are thoroughly mas- 
 tered, has made a step of immeasurable impor- 
 tance. 
 
 But, however good lectures may be, and how- 
 ever extensive the course of reading by which 
 they are followed up, they are but accessories 
 to the great instrument of scientific teaching 
 — demonstration. If I insist unweariedly, nay 
 fanatically, upon the importance of physical sci- 
 ence as an educational agent, it is because the 
 study of any branch of science, if properly con- 
 ducted, appears to me to fill up a void left by all 
 other means of education. I have the greatest 
 respect and love for literature; nothing would 
 grieve me more than to see literary training other 
 than a very prominent branch of education: in- 
 deed, I wish that real literary discipline were 
 far more attended to than it is; but I cannot 
 shut my eyes to the fact, that there is a vast 
 difference between men who have had a purely 
 literary, and those who have had a sound scien- 
 tific training. 
 
 Seeking for the cause of this difference, I im- 
 agine I can find it in the fact that, in the world 
 of letters, learning and knowledge are one, and 
 books are the source of both; whereas in science, 
 as in life, learning and knowledge are distinct, and 
 
222 THE STUDY OF ZOOLOGY. vii 
 
 the study of things, and not of books, is the source 
 of the latter. 
 
 All that literature has to bestow may be ob- 
 tained by reading and by practical exercise in writ- 
 ing and in speaking; but I do not exaggerate 
 when I say, that none of the best gifts of science 
 are to be won by these means. On the contrary, 
 the great benefit which a scientific education be- 
 stows, whether as training or as knowledge, is de- 
 pendent upon the extent to which the mind of the 
 student is brought into immediate contact with 
 facts — upon the degree to which he learns the 
 habit of appealing directly to Nature, and of ac- 
 quiring through his senses concrete images of 
 those properties of things, which are, and always 
 will be, but approximately expressed in human 
 language. Our way of looking at Nature, and of 
 speaking about her, varies from year to year; but 
 a fact once seen, a relation of cause and effect once 
 demonstratively apprehended, are possessions 
 which neither change nor pass away, but, on the 
 contrary, form fixed centres, about which other 
 truths aggregate by natural affinity. 
 
 Therefore, the great business of the scientific 
 teacher is, to imprint the fundamental, irrefraga- 
 ble facts of his science, not only by words upon 
 the mind, but by sensible impressions upon the 
 eye, and ear, and touch of the student, in so com- 
 plete a manner that every term used, or law enun- 
 ciated, should afterwards call up vivid images of 
 
Til THE STUDY OP ZOOLOGY. 223 
 
 the particular structural, or other, facts which fur- 
 nished the demonstration of the law, or the illus- 
 tration of the term. 
 
 Now this important operation can only be 
 achieved by constant demonstration, which may 
 take place to a certain imperfect extent during a 
 lecture, but which ought also to be carried on 
 independently, and which should be addressed to 
 each individual student, the teacher endeavouring, 
 not so much to show a thing to the learner, as to 
 make him see it for himself. 
 
 I am well aware that there are great practical 
 difficulties in the way of efEectual zoological dem- 
 onstrations. The dissection of animals is not alto- 
 gether pleasant, and requires much time; nor is it 
 easy to secure an adequate supply of the needful 
 specimens. The botanist has here a great advan- 
 tage; his specimens are easily obtained, are clean 
 and wholesome, and can be dissected in a private 
 house as well as anywhere else; and hence, I be- 
 lieve, the fact that botany is so much more readily 
 and better taught than its sister science. But, be 
 it difficult or be it easy, if zoological science is to be 
 properly studied, demonstration, and, consequent- 
 ly, dissection, must be had. Without it, no man 
 can have a really sound knowledge of animal organ- 
 isation. 
 
 A good deal may be done, however, without 
 actual dissection on the student's part, by demon- 
 stration upon specimens and preparations; and in 
 
221 THE STUDY OF ZOOLOGY. vn 
 
 all probability it would not be very difficult, were 
 the demand sufficient, to organise collections of 
 such objects, sufficient for all the purposes of ele- 
 mentary teaching, at a comparatively cheap rate. 
 Even without these, much might be effected, if the 
 zoological collections, which are open to the public, 
 were arranged according to what has been termed 
 the " typical principle "; that is to say, if the 
 specimens exposed to public view were so selected 
 that the public could learn something from them, 
 instead of being, as at present, merely confused by 
 their multiplicity. For example, the grand or- 
 nithological gallery at the British Museum con- 
 tains between two and three thousand species of 
 birds, and sometimes five or six specimens of a 
 species. They are very pretty to look at, and 
 some of the cases are, indeed, splendid; but I will 
 undertake to say, that no man but a professed or- 
 nithologist has ever gathered much information 
 from the collection. Certainly, no one of the tens 
 of thousands of the general public who have 
 walked through that gallery ever knew more about 
 the essential peculiarities of birds when he left 
 the gallery than when he entered it. But 
 if, somewhere in that vast hall, there were a 
 few preparations, exemplifying the leading struc- 
 tural peculiarities and the mode of develop- 
 ment of a common fowl; if the types of the 
 genera, the leading modifications in the skeleton, 
 in the plumage at various ages, in the mode of 
 
VII THE STUDY OF ZOOLOGY. 225 
 
 nidification, and the like, among birds, were dis- 
 played; and if the other specimens were put 
 away in a place where the men of science, to 
 whom they are alone useful, could have free ac- 
 cess to them, I can conceive that this collection 
 might become a great instrument of scientific edu- 
 cation. 
 
 The last implement of the teacher to which I 
 have adverted is examination — a means of educa- 
 tion now so thoroughly understood that I need 
 hardly enlarge upon it. I hold that both written 
 and oral examinations are indispensable, and, by 
 requiring the description of specimens, they may 
 be made to supplement demonstration. 
 
 Such is the fullest reply the time at my dis- 
 posal will allow me to give to the question — how 
 may a knowledge of zoology be best acquired and 
 communicated ? 
 
 But there is a previous question which may 
 be moved, and which, in fact, I know many are 
 inclined to move. It is the question, why should 
 teachers be encouraged to acquire a knowledge of 
 this, or any other branch of physical science? 
 What is the use, it is said, of attempting to 
 make physical science a branch of primary edu- 
 cation? Is it not probable that teachers, in pur- 
 suing such studies, will be led astray from the ac- 
 quirement of more important but less attractive 
 knowledge? And, even if they can learn some- 
 thing of science without prejudice to their use- 
 201 
 
226 THE STUDY OP ZOOLOGY. vii 
 
 fulness, what is the good of their attempting to 
 instil that knowledge into boys whose real busi- 
 ness is the acquisition of reading, writing, and 
 arithmetic ? 
 
 These questions are, and will be, very common- 
 ly asked, for they arise from that profound igno- 
 rance of the value and true position of physical sci- 
 ence, which infests the minds of the most highly 
 educated and intelligent classes of the community. 
 But if I. did not feel well assured that they are 
 capable of being easily and satisfactorily answered; 
 that they have been answered over and over again; 
 and that the time will come when men of liberal 
 education will blush to raise such questions — I 
 should be ashamed of my position here to-night. 
 "Without doubt, it is your great and very important 
 function to carry out elementary education; with- 
 out question, anything that should interfere with 
 the faithful fulfilment of that duty on your part 
 would be a great evil; and if I thought that your 
 acquirement of the elements of physical science, 
 and your communication of those elements to your 
 pupils, involved any sort of interference with your 
 proper duties, I should be the first person to pro- 
 test against your being encouraged to do anything 
 of the kind. 
 
 But is it true that the acquisition of such a 
 knowledge of science as is proposed, and the com- 
 munication of that knowledge, are calculated to 
 weaken your usefulness? Or may I not rather ask. 
 
vn THE STUDY OP ZOOLOGY. 227 
 
 is it possible for you to discharge your functions 
 properly without these aids? 
 
 "What is the purpose of primary intellectual 
 education? I apprehend that its first object is to 
 train the young in the use of those tools where- 
 with men extract knowledge from the ever-shift- 
 ing succession of phenomena which pass before 
 their eyes; and that its second object is to inform 
 them of the fundamental laws which have been 
 found by experience to govern the course of things, 
 so that they may not be turned out into the world 
 naked, defenceless, and a prey to the events they 
 might control. 
 
 A boy is taught to read his own and other lan- 
 guages, in order that he may have access to in- 
 finitely wider stores of knowledge than could ever 
 be opened to him by oral intercourse with his fel- 
 low men; he learns to write, that his means of com- 
 munication with the rest of mankind may be in- 
 definitely enlarged, and that he may record and 
 store up the knowledge he acquires. He is taught 
 elementary mathematics, that he may understand 
 all those relations of number and form, upon which 
 the transactions of men, associated in complicated 
 societies, are built, and that he may have some 
 practice in deductive reasoning. 
 
 All these operations of reading, writing, and 
 ciphering, are intellectual tools, whose use should, 
 before all things, be learned, and learned thor- 
 oughly; so that the youth may be enabled to make 
 
228 - THE STUDY OF ZOOLOGY. vii 
 
 his life that which it ought to be, a continual pro- 
 gress in learning and in wisdom. 
 
 But, in addition, primary education endeavours 
 to fit a boy out with a certain equipment of posi- 
 tive knowledge. He is taught the great laws of 
 morality; the religion of his sect; so much history 
 and geography as will tell him where the great 
 countries of the world are, what they are, and how 
 they have become what they are. 
 
 Without doubt all these are most fitting and 
 excellent things to teach a boy; I should be very 
 sorry to omit any of them from any scheme of 
 primary intellectual education. The system is ex- 
 cellent, so far as it goes. 
 
 But if I regard it closely, a curious reflection 
 arises. I suppose that, fifteen hundred years ago, 
 the child of any well-to-do Roman citizen was 
 taught just these same things; reading and writing 
 in his own, and, perhaps, the Greek tongue; the 
 elements of mathematics; and the religion, moral- 
 ity, history, and geography current in his time. 
 Furthermore, I do not think I err in affirming, 
 that, if such a Christian Eoman boy, who had fin- 
 ished his education, could be transplanted into one 
 of our public schools, and pass through its course 
 of instruction, he would not meet with a single un- 
 familiar line of thought; amidst all the new facts 
 he would have to learn, not one would suggest a 
 different mode of regarding the universe from that 
 current in his own time. 
 
Til THE STUDY OP ZOOLOGY. 229 
 
 And yet surely there is some great difference 
 between the civilisation of the fourth century and 
 that of the nineteenth, and still more between the 
 intellectual habits and tone of thought of that day 
 and this? 
 
 And what has made this difference? I answer 
 fearlessly — the prodigious development of physi- 
 cal science within the last two centuries. 
 
 Modern civilisation rests upon physical science; 
 take away her gifts to our own country, and our 
 position among the leading nations of the world 
 is gone to-morrow; for it is physical science only 
 that makes intelligence and moral energy stronger 
 than brute force. 
 
 The whole of modern thought is steeped in 
 science; it has made its way into the works of our 
 best poets, and even the mere man of letters, who 
 affects to ignore and despise science, is uncon- 
 sciously impregnated with her spirit, and indebted 
 for his- best products to her methods. I believe 
 that the greatest intellectual revolution mankind 
 has yet seen is now slowly taking place by her 
 agency. She is teaching the world that the ulti- 
 mate court of appeal is observation and experi- 
 ment, and not authority; she is teaching it to esti- 
 mate the value of evidence; she is creating a firm 
 and living faith in the existence of immutable 
 moral and physical laws, perfect obedience to 
 which is the highest possible aim of an intelligent 
 being. 
 
230 THE STUDY OF ZOOLOGY. vn 
 
 But of all this your old stereotyped system of 
 education takes no note. Physical science, its 
 methods, its problems, and its difficulties, will 
 meet the poorest boy at every turn, and yet we 
 educate him in such a manner that he shall enter 
 the world as ignorant of the existence of the 
 methods and facts of science as the day he 
 was born. The modern world is full of artillery; 
 and we turn out our children to do battle in it, 
 equipped with the shield and sword of an ancient 
 gladiator. 
 
 Posterity will cry shame on us if we do not 
 remedy this deplorable state of things. Nay, if we 
 live twenty years longer, our own consciences will 
 cry shame on us. 
 
 It is my firm conviction that the only way to 
 remedy it is to make the elements of physical sci- 
 ence an integral part of primary education. I 
 have endeavoured to show you how that may be 
 done for that branch of science which it is my 
 business to pursue; and I can but add, that I 
 should look upon the day when every schoolmaster 
 throughout this land was a centre of genuine, how- 
 ever rudimentary, scientific knowledge, as an 
 epoch in the history of the country. 
 
 But let me entreat you to remember my last 
 words. Addressing myself to you, as teachers, I 
 would say, mere book learning in physical science 
 is a sham and a delusion — what you teach, unless 
 you wish to be impostors, that you must first 
 
VII THE STUDY OF ZOOLOGY. 231 
 
 know; and real knowledge in science means per- 
 sonal acquaintance with the facts, be they few or 
 many.* 
 
 * It has been suggested to me that these words may 
 be taken to imply a discouragement on my part of any 
 sort of scientific instruction which does not give an ac- 
 quaintance with the facts at first hand. But this is not 
 my meaning. The ideal of scientific teaching is, no doubt, 
 a system by which the scholar, sees every fact for himself, 
 and the teacher supplies only the explanations. Circum- 
 stances, however, do not often allow of the attainment 
 of that ideal, and we must put up with the next best 
 system — one in which the scholar takes a good deal on 
 trust from a teacher, who, knowing the facts by his o\^ti 
 knowledge, can describe them with so much vividness as 
 to enable his audience to form competent ideas concerning 
 them. The system which I repudiate is that which allows 
 teachers who have not come into direct contact with the 
 leading facts of a science to pass their second-hand infor- 
 mation on. The scientific virus, like vaccine lymph, if 
 passed through too long a succession of organisms, will 
 lose all its effect in protecting the young against the in- 
 tellectual epidemics to which they are exposed. 
 
 [The remarks on p. 224 applied to the Natural His- 
 tory Collection of the British Museum in 1861. The vis- 
 itor to the Natural History Museum in 1894 need go no 
 further than the Great Hall to see the realisation of my 
 hopes by the present Director.] 
 
VIII. 
 BIOGENESIS AND ABIOGENESIS. 
 
 (the presidential address to the BRITISH 
 
 ASSOCIATION POR THE ADVANCEMENT OF SCIENCE 
 
 FOR 1870.) 
 
 It has long been the custom for the newly in- 
 stalled President of the British Association for the 
 Advancement of Science to take advantage of the 
 elevation of the position in which the suffrages of 
 his colleagues had, for the time, placed him, and, 
 casting his eyes around the horizon of the scientific 
 world, to report to them what could be seen from 
 his watch tower; in what directions the multitu- 
 dinous divisions of the noble army of the improvers 
 of natural knowledge were marching; what im- 
 portant strongholds of the great enemy of us all, 
 ignorance, had been recently captured; and, also, 
 with due impartiality, to mark where the advanced 
 posts of science had been driven in, or a long-con- 
 tinued siege had made no progress. 
 
 I propose to endeavour to follow this ancient 
 precedent, in a manner suited to the limitations of 
 232 
 
VIII BIOGENESIS AND ABIOGENESIS. 233 
 
 my knowledge and of my capacity. I shall not 
 presume to attempt a panoramic survey of the 
 world of science, nor even to give a sketch of what 
 is doing in the one great province of biology, with 
 some portions of which my ordinary occupations 
 render me familiar. But I shall endeavour to put 
 before you the history of the rise and progress of 
 a single biological doctrine; and I shall try to give 
 some notion of the fruits, both intellectual and 
 practical, which we owe, directly or indirectly, 
 to the working out, by seven generations of pa- 
 tient and laborious investigators, of the thought 
 which arose, more than two centuries ago, in the 
 mind of a sagacious and observant Italian natu- 
 ralist. 
 
 It is a matter of everyday experience that it is 
 difficult to prevent many articles of food from be- 
 coming covered with mould; that fruit, sound 
 enough to all appearance, often contains grubs at 
 the core; that meat, left to itself in the air, is 
 apt to putrefy and swarm with maggots. Even 
 ordinary water, if allowed to stand in an open ves- 
 sel, sooner or later becomes turbid and full of 
 living matter. 
 
 The philosophers of antiquity, interrogated as 
 to the cause of these phenomena, were provided 
 with a ready and a plausible answer. It did not 
 enter their minds even to doubt that these low 
 forms of life were generated in the matters in 
 which they made their appearance. Lucretius, 
 
234: BIOGENESIS AND ABIOGENESIS. viii 
 
 who had drunk deeper of the scientific spirit than 
 any poet of ancient or modern times except Goethe, 
 intends to speak as a philosopher, rather than as a 
 poet, when he writes that " with good reason the 
 earth has gotten the name of mother, since all 
 things are produced out of the earth. And many 
 living creatures, even now, spring out of the earth, 
 taking form by the rains and the heat of the 
 sun." * The axiom of ancient science, " that the 
 corruption of one thing is the birth of another," 
 had its popular embodiment in the notion that a 
 seed dies before the young plant springs from it; 
 a belief so wide-spread and so fixed, that Saint 
 Paul appeals to it in one of the most splendid out- 
 bursts of his fervid eloquence: — 
 
 " Thou fool, that which thou sowest is not 
 quickened, except it die." f 
 
 The proposition that life may, and does, pro- 
 ceed from that which has no life, then, was held 
 alike by the philosophers, the poets, and the people, 
 of the most enlightened nations, eighteen hundred 
 years ago; and it remained the accepted doctrine 
 of learned and unlearned Europe, through the 
 
 * It is thus that Mr. Munro renders 
 " Linquitur, ut merito matemum nomen adepta 
 Terra sit, e terra quoniara sunt euncta creata. 
 Multaque nunc etiam exsistant animalia terris 
 Imbribus et calido solis eoncreta vapore." 
 
 De Eerum Natura, lib. v. 793-796. 
 But would not the meaning of the last line be better 
 rendered " Developed in rain-water and in the warm va- 
 pours raised by the sun " ? 1 1 Corinthians xv. 36. 
 
Till BlOaENBSIS AND ABIOGBNESIS. 235 
 
 Middle Ages, down even to the seventeenth cen- 
 tury. 
 
 It is commonly counted among the many 
 merits of our great countryman, Harvey, that he 
 was the first to declare the opposition of fact to 
 venerahle authority in this, as in other matters; 
 but I can discover no justification for this wide- 
 spread notion. After careful search through the 
 " Exercitationes de Generatione," the most that 
 appears clear to me is, that Harvey believed all ani- 
 mals and plants to spring from what he terms a 
 " primordium vegetale" a phrase which may now- 
 adays be rendered " a vegetative germ "; and this, 
 he says, is " oviforme," or " egg-like "; not, he is 
 careful to add, that it necessarily has the shape of 
 an egg, but because it has the constitution and 
 nature of one. That this " primordium oviforme " 
 must needs, in all cases, proceed from a living par- 
 ent is nowhere expressly maintained by Harvey, 
 though such an opinion may be thought to be im- 
 plied in one or two passages; while, on the other 
 hand, he does, more than once, use language which 
 is consistent only with a full belief in spontaneous 
 or equivocal generation.* In fact, the main con- 
 
 * See the following passage in Exercitatio I.: — "Item 
 sponte nascentia dicuntur; non quod ex pntrcdine ori- 
 unda sint, sad quod casu, naturae sponte, et sequivoca (ut 
 aiunt) generatione, a parentibus sui dissimilibus proveni- 
 ant." Again, in De Uteri Meiribranis : — " In cunctorum 
 viventium generatione (sieut diximus) hoc solenne est, 
 ut ortum ducunt a primordio aliquo, quod turn materiam 
 turn eflBeiendi potestatem in se habet: sitque adeo id, ex 
 
236 BIOGENESIS AND ABIOGENESIS. Tin 
 
 cern of Harvey's wonderful little treatise is not 
 with generation, in the physiological sense, at all, 
 but with development; and his great object is the 
 establishment of the doctrine of epigenesis. 
 
 The first distinct enunciation of the hypothesis 
 that all living matter has sprung from pre-existing 
 living matter, came from a contemporary, though a 
 junior, of Harvey, a native of that country, fertile 
 in men great in all departments of human activity, 
 which was to intellectual Europe, in the sixteenth 
 and seventeenth centuries, what Germany is in the 
 nineteenth. It was in Italy, and from Italian 
 teachers, that Harvey received the most important 
 part of his scientific education. And it was a 
 student trained in the same schools, Francesco 
 Eedi — a man of the widest knowledge and most 
 versatile abilities, and distinguished alike as 
 scholar, poet, physician, and naturalist; — who, just 
 two hundred and two years ago, published his " Es- 
 perienze intorno alia Generazione degl' Insetti," 
 and gave to the world the idea, the growth of 
 which it is my purpose to trace. Eedi's book went 
 through five editions in twenty years; and the ex- 
 treme simplicity of his experiments, and the clear- 
 ness of his arguments, gained for his views, and for 
 their consequences, almost universal acceptance. 
 
 quo et a quo quicquid nascitur, ortum suum dueat. Tale 
 primordium in animalibus {sive ab aliis generantibua 
 proveniant, sive sponte, aut ex putredine nascentur) est 
 humor in tunica aliqua aut putami ne oonclusus." Com- 
 pare also what Eedi has to say respecting Harvey's opin- 
 ions, Esperienze, p. 11. 
 
TUi BIOGENESIS AND ABIOGBNESIS. 237 
 
 Eedi did not trouble himself much with specu- 
 lative considerations, but attacked particular cases 
 of what was supposed to be " spontaneous genera- 
 tion " experimentally. Here are dead animals, or 
 pieces of meat, says he; I expose them to the air 
 in hot weather, and in a few days they swarm with 
 maggots. You tell me that these are generated 
 in the dead flesh; but if I put similar bodies, while 
 quite fresh, into a jar, and tie some fine gauze 
 over the top of the jar, not a maggot makes its ap- 
 pearance, while the dead substances, nevertheless, 
 putrefy just in the same way as before. It is ob- 
 vious, therefore, that the maggots are not gener- 
 ated by the corruption of the meat; and that the 
 cause of their formation must be a something 
 which is kept away by gauze. But gauze will not 
 keep away aeriform bodies, or fluids. This some- 
 thing must, therefore, exist in the form of solid 
 particles too big to get through the gauze. Nor is 
 one long left in doubt what these solid particles 
 are; for the blow-flies, attracted by the odour of 
 the meat, swarm round the vessel, and, urged by a 
 powerful but in this case misleading instinct, lay 
 eggs out of which maggots are immediately 
 hatched, upon the gauze. The conclusion, there- 
 fore, is unavoidable; the maggots are not gen- 
 erated by the meat, but the eggs which give rise to 
 them are brought through the air by the flies. 
 
 These experiments seem almost childishly 
 simple, and one wonders how it was that no one 
 
238 BIOGENESIS AND ABIOGBNESIS. vni 
 
 ever thought of them before. Simple as they are, 
 however, they are worthy of the most careful study, 
 for every piece of experimental work since done, 
 in regard to this subject, has been shaped upon 
 the model furnished by the Italian philosopher. 
 As the results of his experiments were the same, 
 however varied the nature of the materials he 
 used, it is not wonderful that there arose in Redi's 
 mind a presumption, that, in all such cases of the 
 seeming production of life from dead matter, the 
 real explanation was the introduction of living 
 germs from without into that dead matter.* And 
 
 * " Pure contentandomi sempre in questa ed in cias- 
 cuna altro eosa, da ciascuno pift savio, la. dove io difet- 
 tuosamente parlassi, esser corretto; non taeero, ehe per 
 molte osservazioni molti volti da me fatte, mi sento in- 
 clinato a credere che la terra, da quelle prime piante, e 
 da quei primi animali in poi, che ella nei primi giorni del 
 mondo produsse per comandemento del sovrano ed omni- 
 potente Fattore, non abbia mai pift prodotto da ae mede- 
 sima n6 erba n6 albero, ng animale alcuno perfetto o im- 
 perfetto che ei se fosse; e che tutto quello, che ne' tempi 
 trapassati 6 nato e che ora naacere in lei, o da lei veg- 
 giamo, venga tutto dalla semenza reale e vera delle piante, 
 e degli animali stessi, i quali col mezzo del proprio seme 
 la lore Bpezie conservano. E se bene tutto giorno seor- 
 ghiamo da' cadaveri degli animali, e da tutte quante le 
 maniere dell' erbe, e de' fiori, e dei frutti imputriditi, e 
 corrotti naseere vermi infiniti — 
 
 ' Nonne vides qusecunque mora, fluidoque ealore 
 Corpora tabeseunt in parva animalia verti ' — 
 To mi sento, dico, inclinato, a credere che tutti quei vermi 
 si generino dal seme paterno; e che le carni, e 1' erbe, 
 e r altre cose tutte putrefatte, o putrefattibili non fac- 
 ciano altra parte, n& abbiano altro ufizio nella genera- 
 zione degl' insetti, se non d'apprestare un luogo o un 
 nido proporzionato, in cui dagli animali nel tempo della 
 
viii BIOGENESIS AND ABIOGBNESIS. 239 
 
 thus the hypothesis that living matter always arises 
 by the agency of pre-existing living matter, took 
 definite shape; and had, henceforward, a right to 
 be considered and a claim to be refuted, in each 
 particular case, before the production of living 
 matter in any other way could be admitted by 
 careful reasoners. It will be necessary for me to 
 refer to this hypothesis so frequently, that, to save 
 circumlocution, I shall call it the hypothesis of 
 Biogenesis ; and I shall term the contrary doctrine 
 — that living matter may be produced by not liv- 
 ing matter — the hypothesis of Ahiogenesis. 
 
 In the seventeenth century, as I have said, the 
 latter was the dominant view, sanctioned alike by 
 antiquity and by authority; and it is interesting to 
 observe that Eedi did not escape the customary tax 
 upon a discoverer of having to defend himself 
 against the charge of impugning the authority of 
 the Scriptures; * for his adversaries declared that 
 the generation of bees from the carcass of a dead 
 lion is affirmed, in the Book of Judges, to have 
 
 figliatura sieno portati, e partoritl 1 vermi, o 1' uova o 
 1' altre semenze del vermi, i quali tosto ehe nati sono, 
 trovano in esso nido un suffieiente alimento abilissimo 
 per nutricarsi: e se in quello non son portate dalle 
 madri queste auddette semenze, niente mai, e replieata- 
 mente niente, vi s' ingegneri e nasca." — Eedi, Esperienze, 
 pp. 14-16. 
 
 * " Molti, e molti altri aneora vi potrei annoverare, se 
 non fossi chiamato a rispondere alle rampogne di alcuni, 
 ehe bruseamente mi rammentano ci6, che si legge nel 
 eapitolo quattordiceaimo del sacrosanto Libro de' giu- 
 dici . . ."' — Redi, loo. cit. p. 45. 
 
240 BIOGENESIS AND ABIOGBNESIS. Tin 
 
 been the origin of the famous riddle with which 
 Samson perplexed the Philistines: — 
 " Out of the eater eame forth meat, 
 And out of the strong came forth sweetness." 
 
 Against all odds, however, Eedi, strong with 
 the strength of demonstrable fact, did splendid 
 battle for Biogenesis; but it is remarkable that 
 he held the doctrine in a sense which, if he had 
 lived in these times, would have infallibly caused 
 him to be classed among the defenders of " spon- 
 taneous generation." " Omne vivum ex vivo," 
 "no life without antecedent life," aphoristically 
 sums up Eedi's doctrine; but he went no further. 
 It is most remarkable evidence of the philosophic 
 caution and impartiality of his mind, that although 
 he had speculatively anticipated the manner in 
 which grubs really are deposited in fruits and in 
 the galls of plants, he deliberately admits that the 
 evidence is insufficient to bear him out; and he 
 therefore prefers the supposition that they are gen- 
 erated by a modification of the living substance of 
 the plants themselves. Indeed, he regards these 
 vegetable growths as organs, by means of which 
 the plant gives rise to an animal, and looks upon 
 this production of specific animals as the final 
 cause of the galls and of, at any rate, some fruits. 
 And he proposes to explain the occurrence of para- 
 sites within the animal body in the same way.* 
 
 *The passage (Esperienze, p. 129) is worth quoting 
 in full: — 
 
 " Se dovessi palesarvi il mio sentimento crederei che 
 
vni BIOGENESIS AND ABIOGENESIS. 241 
 
 It is of great importance to apprehend Eedi's 
 position rightly; for the lines of thought he laid 
 down for us are those upon which naturalists have 
 been working ever since. Clearly, he held Bio- 
 
 i frutti, i legumi, gli alberi e le foglie, in due maniere 
 inverminassero. Una, perche venendo i bachi per di 
 fuora, e ceicando 1' alimento, col rodere ci aprono la 
 strada, ed arrivano alia pid interna midolla de' frutti e 
 de' legni. L'altra maniera si 6, che io per me stimerei, 
 che non fosse gran fatto disdicevole il credere, che quell' 
 anima o quella virtil, la quale genera i fiori ed i frutti 
 nelle piante viventi, sia quella stessa clie generi aneora 
 i bachi di esse piante. E chi sa forse, che molti frutti 
 degli alberi non sieno prodotti, non per un fine primario 
 6 principale, ma bensi per un uffizio seeondario e servile, 
 destinato alia generazione di que' vermi, servendo a loro 
 in vece di matrice, in eui dimorino un prefisso e deter- 
 minato tempo; il quale arrivato escan fuora a godere 
 il sole. 
 
 " Io m' immagino, che questo mio pensiero non vi 
 parra totalmente un paradosso; mentre farete riflessione 
 a quelle tante sorte di galle, di gallozzole, di coccole, di 
 ricci, di ealici, di cornetti ed i lappole, che son produtte 
 dalle quereel, dalle farnie, da' cerri, da' sugheri, da' leeei 
 e da altri simili alberi da ghianda ; imperciocehfi in quelle 
 gallozzole, e partieolarmente nelle pifi grosse, che si chia- 
 mano coronati, ne' rieci eapelluti, che ciufToli da' nostri 
 contadini son detti; nei ricei legnosi del cerro, ne' ricci 
 stellati della querela, nelle galluzze della foglia del leccio 
 si vede evidentissimamente, che la prima e principale in- 
 tenzione della natura 6 formare dentro di quelle un ani- 
 male volante; vedendosi nel centro della gallozzola un 
 uovo, che col erescere e col maturarsi di essa gallozzola 
 va crescendo e maturando anch' egli, e eresce altresi a 
 suo tempo quel verme, che nell' uovo si racehiude; il qual 
 verme, quando la gallozzola 6 finita di maturare e che 6 
 venuto il termine destinato al suo naseimento, diventa, 
 di verme che era, una mosca. . . . Io vi confesso in- 
 genuamente, che prima d'aver fatte queste mie esperienze 
 intorno alia generazione degl' insetti mi dava a credere, 
 o per dir meglio sospettava, che forse la gallozzola nas- 
 cesse, perch6 arrivando la mosca nel tempo della priraa- 
 vera, e facendo una piceolissima fessura ne' rami piil 
 202 
 
242 BIOGENESIS AND ABIOGENBSIS. vni 
 
 genesis as against AUogenesis ; and I shall imme- 
 diately proceed, in the first place, to inquire how 
 far subsequent investigation has borne him out in 
 BO doing. 
 
 But Eedi also thought that there were two 
 modes of Biogenesis. By the one method, which is 
 that of common and ordinary occurrence, the liv- 
 ing parent gives rise to offspring which passes 
 through the same cycle of changes as itself — like 
 gives rise to like; and this has been termed Homo- 
 genesis. By the other mode, the living parent was 
 supposed to give rise to offspring which passed 
 through a totally different series of states from 
 those exhibited by the parent, and did not return 
 into the cycle of the parent; this is what ought to 
 be called Heterogenesis, the offspring being alto- 
 gether, and permanently, unlike the parent. The 
 term Heterogenesis, however, has unfortunately 
 been used in a different sense, and M. Milne-Ed- 
 wards has therefore substituted for it Xenogenesis, 
 which means the generation of something foreign. 
 After discussing Eedi's hypothesis of universal 
 Biogenesis, then, I shall go on to ask how far the 
 
 teneri della querela, in quella fessura nascondesse uno 
 de suoi semi, il quale fosse cagione che sbocciasse fuora 
 la gallozzola ; e che mai non si vedessero galle o gallozzole 
 o ricei o eornetti o caliei o eoeeole, se non in que' rami, 
 ne' quali le mosche avessero depositate le loro semenze; 
 e mi dava ad intendere, che le gallozzole fossero una ma- 
 lattia cagionata nelle queree dalle punture delle mosche, 
 in quella giusa stessa che dalle punture d' altri animaletti 
 eimiglievoli veggiamo creseere de' tumori ne' corpi degli 
 animali." 
 
VIII BIOGENESIS AND ABIOGENESIS. 243 
 
 growth of science justifies his other hypothesis of 
 Xenogenesis. 
 
 The progress of the hypothesis of Biogenesis 
 was triumphant and unchecked for nearly a cen- 
 tury. The application of the microscope to anat- 
 omy in the hands of Grew, Leeuwenhoek, Swam- 
 merdam, Lyonnet, Vallisnieri, Reaumur, and oth- 
 er illustrious investigators of nature of that day, 
 displayed such a complexity of organisation in the 
 lowest and minutest forms, and everywhere re- 
 vealed such a prodigality of provision for their 
 multiplication by germs of one sort or another, 
 that the hypothesis of Abiogenesis began to appear 
 not only untrue, but absurd; and, in the middle 
 of the eighteenth century, when Needham and 
 Buffon took up the question, it was almost univer- 
 sally discredited.* 
 
 But the skill of the microscope makers of the 
 eighteenth century soon reached its limit. A 
 microscope magnifying 400 diameters was a chef 
 d'ceuvre of the opticians of that day; and, at the 
 same time, by no means trustworthy. But a mag- 
 
 * Needham, writing in 1750, says: — 
 
 " Les naturalistes modernes s'aecordent unaninement 
 a gtablir, eomme une vfiritS certaine, que toute plante 
 vient de sa semenee spgcifique, tout animal d'un oeuf ou 
 de quelque chose d'analogue prgexlstant dans la plante, 
 ou dans I'animal de m6me esp6ce qui I'a produit." — Nou- 
 velles Observations, p. 169. 
 
 " Les naturalistes ont gfingralemente eru que les ani- 
 maux mieroscopiques 6taient engendrfis par des oeufs 
 transportgs dans I'air, ou dgposfis dans des eaux dor- 
 mantes par des insectes volans." — IMd. p. 176. 
 
244 BIOGENESIS AND ABIOGENESIS. vm 
 
 nifying power of 400 diameters, even when defini- 
 tion reaches the exquisite perfection of our modern 
 achromatic lenses, hardly suffices for the mere dis- 
 cernment of the smallest forms of life. A speck, 
 only ]jV^^ °^ ^^ ^^^^ ^^ diameter, has, at ten 
 inches from the eye, the same apparent size as 
 an object -rrruT*"^ °^ ^^ ^^^^ ^^ diameter, when 
 magnified 400 times; but forms of living matter 
 abound, the diameter of which is not more than 
 fijwny^^ of an inch. A filtered infusion of hay, 
 allowed to stand for two days, will swarm with 
 living things among which any which reaches the 
 diameter of a human red blood-corpuscle, or about 
 s 2^6 ^^ °^ ^^ inch, is a giant. It is only by bear- 
 ing these facts in mind, that we can deal fairly 
 with the remarkable statements and speculations 
 put forward by BufEon and Needham in the middle 
 of the eighteenth century. 
 
 When a portion of any animal or vegetable 
 body is infused in water, it gradually softens and 
 disintegrates; and, as it does so, the water is found 
 to swarm with minute active creatures, the so- 
 called Infusorial Animalcules, none of which can 
 be seen, except by the aid of the microscope; while 
 a large proportion belong to the category of small- 
 est things of which I have spoken, and which 
 must have looked like mere dots and lines under 
 the ordinary microscopes of the eighteenth cen- 
 tury. 
 
 Led by various theoretical considerations which 
 
VIII BIOGENESIS AND ABIOGENBSIS. 245 
 
 I cannot now discuss, but which looked promising 
 enough in the lights of their time, BufEon and 
 Needham doubted the applicability of Redi's hypo- 
 thesis to the infusorial animalcules, and Need- 
 ham very properly endeavoured to put the question 
 to an experimental test. He said to himself, If 
 these infusorial animalcules come from germs, 
 their germs must exist either in the substance in- 
 fused, or in the water with which the infusion is 
 made, or in the superjacent air. Now the vitality 
 of all germs is destroyed by heat. Therefore, if 
 I boil the infusion, cork it up carefully, cementing 
 the cork over with mastic, and then heat the whole 
 vessel by heaping hot ashes over it, I must needs 
 kill whatever germs are present. Consequently, if 
 Redi's hypothesis hold good, when the infusion is 
 taken away and allowed to cool, no animalcules 
 ought to be developed in it; whereas, if the ani- 
 malcules are not dependent on pre-existing germs, 
 but are generated from the infused substance, they 
 ought, by and by, to make their appearance. 
 Needham found that, under the circumstances in 
 which he made his experiments, animalcules al- 
 ways did arise in the infusions, when a suffi- 
 cient time had elapsed to allow for their develop- 
 ment. 
 
 In much of his work Needham was associated 
 with Buffon, and the results of their experiments 
 fitted in admirably with the great French natural* 
 ist's hypothesis of " organic molecules," according 
 
246 BIOGENESIS AND ABIOGENESIS. Tin 
 
 to which life is the indefeasible property of cer- 
 tain indestructible molecules of matter, which ex- 
 ist in all living things, and have inherent activities 
 by which they are distinguished from not living 
 matter. Each individual living organism is 
 formed by their temporary combination. They 
 stand to it in the relation of the particles of water 
 to a cascade, or a whirlpool; or to a mould, into 
 which the water is poured. The form of the or- 
 ganism is thus determined by the reaction between 
 external conditions and the inherent activities of 
 the organic molecules of which it is composed; 
 and, as the stoppage of a whirlpool destroys noth- 
 ing but a form, and leaves the molecules of the 
 water, with all their inherent activities intact, so 
 what we call the death and putrefaction of an ani- 
 mal, or of a plant, is merely the breaking up of the 
 form, or manner of association, of its constituent 
 organic molecules, which are then set free as infu- 
 sorial animalcules. 
 
 It will be perceived that this doctrine is by no 
 means identical with Ahiogenesis, with which it is 
 often confounded. On this hypothesis, a piece of 
 beef, or a handful of hay, is dead only in a limited 
 sense. The beef is dead ox, and the hay is dead 
 grass; but the " organic molecules " of the beef or 
 the hay are not dead, but are ready to manifest 
 their vitality as soon as the bovine or herbaceous 
 shrouds in which they are imprisoned are rent by 
 the macerating action of water. The hypothesis, 
 
VIII BIOGENESIS AND ABIOGENBSIS. 247 
 
 therefore, must be classified under Xenogenesis, 
 rather than under Abiogenesis. Such as it was, I 
 think it will appear, to those who will be just 
 enough to remember that it was propounded be- 
 fore the birth of modern chemistry, and of the 
 modern optical arts, to be a most ingenious and 
 suggestive speculation. 
 
 But the great tragedy of Science — the slaying 
 of a beautiful hypothesis by an ugly fact — which is 
 so constantly being enacted under the eyes of philo- 
 sophers, was played, almost immediately, for the 
 benefit of Buffon and Needham. 
 
 Once more, an Italian, the Abbe Spallanzani, a 
 worthy successor and representative of Eedi in his 
 acuteness, his ingenuity, and his learning, subject- 
 ed the experiments and the conclusions of Need- 
 ham to a searching criticism. It might be true 
 that Needham's experiments yielded results such 
 as he had described, but did they bear out his argu- 
 ments? Was it not possible, in the first place, he 
 had not completely excluded the air by his corks 
 and mastic? And was it not possible, in the sec- 
 ond place, that he had not sufficiently heated his 
 infusions and the superjacent air? Spallanzani 
 joined issue with the English naturalist on both 
 these pleas, and he showed that if, in the first 
 place, the glass vessels in which the infusions were 
 contained were hermetically sealed by fusing their 
 necks, and if, in the second place, they were ex- 
 posed to the temperature of boiling water for 
 
248 BIOGENESIS AND ABIOGENESIS. tiu 
 
 three-quarters of an hour^* no animalcules ever 
 made their appearance within them. It must be 
 admitted that the experiments and arguments of 
 Spallanzani furnish a complete and a crushing 
 reply to those of Needham. But we all too often 
 forget that it is one thing to refute a proposition, 
 and another to prove the truth of a doctrine which, 
 implicitly or explicitly, contradicts that propo- 
 sition, and the advance of science soon showed 
 that though Needham might be quite wrong, it 
 did not follow that Spallanzani was quite right. 
 
 Modern Chemistry, the birth of the latter half 
 of the eighteenth century, grew apace, and soon 
 found herself face to face with the great problems 
 which biology had vainly tried to attack without 
 her help. The discovery of oxygen led to the lay- 
 ing of the foundations of a scientific theory of re- 
 spiration, and to an examination of the marvellous 
 interactions of organic substances with oxygen. 
 The presence of free oxygen appeared to be one 
 of the conditions of the existence of life, and of 
 those singular changes in organic matters which 
 are known as fermentation and putrefaction. The 
 question of the generation of the infusory animal- 
 cules thus passed into a new phase. For what 
 might not have happened to the organic matter of 
 the infusions, or to the oxygen of the air, in Spall- 
 anzani's experiments? What security was there 
 that the development of life which ought to have 
 * See Spallanzani, Opere, vi. pp. 42 and 51. 
 
VIII BIOGENESIS AND ABIOGENBSIS, 249 
 
 taken place had not been checked or prevented by 
 these changes? 
 
 The battle had to be fought again. It was 
 needful to repeat the experiments under conditions 
 which would make sure that neither the oxygen of 
 the air, nor the composition of the organic matter, 
 was altered in such a manner as to interfere with 
 the existence of life. 
 
 Schulze and Schwann took up the question 
 from this point of view in 1836 and 1837. The 
 passage of air through red-hot glass tubes, or 
 through strong sulphuric acid, does not alter the 
 proportion of its oxygen, while it must needs arrest, 
 or destroy, any organic matter which may be con- 
 tained in the air. These experimenters, therefore, 
 contrived arrangements by which the only air 
 which should come into contact with a boiled infu- 
 sion should be such as had either passed through 
 red-hot tubes or through strong sulphuric acid. 
 The result which they obtained was that an infu- 
 sion so treated developed no living things, while, if 
 the same infusion was afterwards exposed to the 
 air, such things appeared rapidly and abundantly. 
 The accuracy of these experiments has been alter- 
 nately denied and affirmed. Supposing them to 
 be accepted, however, all that they really proved 
 was that the treatment to which the air was sub- 
 jected destroyed something that was essential to 
 the development of life in the infusion. This 
 " something " might be gaseous, fluid, or solid; 
 
250 BIOGEKESIS AND ABIOGBNESIS. Tin 
 
 that it consisted of germs remained only an hypo- 
 thesis of greater or less probability. 
 
 Contemporaneously with these investigations a 
 remarkable discovery was made by Cagniard de la 
 Tour. He found that common yeast is composed 
 of a vast accumulation of minute plants. The fer- 
 mentation of must, or of wort, in the fabrication of 
 wine and of beer, is always accompanied by the 
 rapid growth and multiplication of these Torulce. 
 Thus, fermentation, in so far as it was accom- 
 panied by the development of microscopical organ- 
 isms in enormous numbers, became assimilated to 
 the decomposition of an infusion of ordinary ani- 
 mal or vegetable matter; and it was an obvious 
 suggestion that the organisms were, in some way 
 or other, the causes both of fermentation and of 
 putrefaction. The chemists, with Berzelius and 
 Liebig at their head, at first laughed this idea to 
 scorn; but in 1843, a man then very young, who 
 has since performed the unexampled feat of attain- 
 ing to high eminence alike in Mathematics, Phy- 
 sics, and Physiology — I speak of the illustrious 
 Helmholtz — reduced the matter to the test of ex- 
 periment by a method alike elegant and conclusive. 
 Helmholtz separated a putrefying or a fermenting 
 liquid from one which was simply putreseible or 
 fermentable by a membrane which allowed the 
 fluids to pass through and become intermixed, but 
 stopped the passage of solids. The result was, that 
 while the putreseible or the fermentable liquids be- 
 
vni BIOGENESIS AND ABIOGENBSIS. 251 
 
 came impregnated with the results of the putres- 
 cence or fermentation which was going on on the 
 other side of the membrane, they neither putrefied 
 (in the ordinary way) nor fermented; nor were any 
 of the organisms which abounded in the ferment- 
 ing or putrefying liquid generated in them. 
 Therefore the cause of the development of these 
 organisms must lie in something which cannot pass 
 through membranes; and as Helmholtz's investi- 
 gations were long antecedent to Graham's re- 
 searches upon colloids, his natural conclusion was 
 that the agent thus intercepted must be a solid 
 material. In point of fact, Helmholtz's experi- 
 ments narrowed the issue to this: that which ex- 
 cites fermentation and putrefaction, and at the 
 same time gives rise to living forms in a ferment- 
 able or putrescible fluid, is not a gas and is not a 
 diffusible fluid; therefore it is either a colloid, or 
 it is matter divided into very minute solid par- 
 ticles. 
 
 The researches of Schroeder and Dusch in 
 1854, and of Schroeder alone, in 1859, cleared up 
 this point by experiments which are simply refine- 
 ments upon those of Eedi. A lump of cotton- 
 wool is, physically speaking, a pile of many thick- 
 nesses of a very fine gauze, the fineness of the 
 meshes of which depends upon the closeness of the 
 compression of the wool. Now, Schroeder and 
 Dusch found, that, in the ease of all the putrefi- 
 able materials which they used (except milk and 
 
252 BIOGENESIS AND ABIOGENESIS. Tin 
 
 yolk of egg), an infusion boiled, and then allowed 
 to come into contact with no air but such as had 
 been filtered through cotton-wool, neither putre- 
 fied, nor fermented, nor developed living forms. 
 It is hard to imagine what the fine sieve formed 
 by the cotton-wool could have stopped except min- 
 ute solid particles. Still the evidence was in- 
 complete until it had been positively shown, first, 
 that ordinary air does contain such particles; and, 
 secondly, that filtration through cotton-wool ar- 
 rests these particles and allows only physically pure 
 air to pass. This demonstration has been fur- 
 nished within the last year by the remarkable ex- 
 periments of Professor Tyndall. It has been a 
 common objection of Abiogenists that, if the doc- 
 trine of Biogeny is true, the air must be thick with 
 germs; and they regard this as the height of ab- 
 surdity. But nature occasionally is exceedingly 
 unreasonable, and Professor Tyndall has proved 
 that this particular absurdity may nevertheless be 
 a reality. He has demonstrated that ordinary air 
 is no better than a sort of stirabout of excessively 
 minute solid particles; that these particles are 
 almost wholly destructible by heat; and that they 
 are strained off, and the air rendered optically 
 pure, by its being passed through cotton-wool. 
 
 It remains yet in the order of logic, though 
 not of history, to show that among these solid de- 
 structible particles, there really do exist germs 
 capable of giving rise to the development of living 
 
vin BIOGENESIS AND ABIOGENESIS. 253 
 
 forms in suitable menstrua. This piece of work 
 was done by M. Pasteur in those beautiful re- 
 searches which will ever render his name famous; 
 and which, in spite of all attacks upon them, ap- 
 pear to me now, as they did seven years ago,* to be 
 models of accurate experimentation and logical 
 reasoning. He strained air through cotton-wool, 
 and found, as Schroeder and Dusch had done, that 
 it contained nothing competent to give rise to the 
 development of life in fluids highly fitted for that 
 purpose. But the important further links in the 
 chain of evidence added by Pasteur are three. In 
 the first place he subjected to microscopic examina- 
 tion the cotton-wool which had served as strainer, 
 and found that sundry bodies clearly recognisable 
 as germs, were among the solid particles strained 
 off. Secondly, he proved that these germs were 
 competent to give rise to living forms by simply 
 sowing them in a solution fitted for their develop- 
 ment. And, thirdly, he showed that the incapacity 
 of air strained through cotton-wool to give rise to 
 life, was not due to any occult change effected in 
 the constituents of the air by the wool, by proving 
 that the cotton-wool might be dispensed with alto- 
 gether, and perfectly free access left between the 
 exterior air and that in the experimental flask. 
 If the neck of the flask is drawn out into a tube 
 
 * Lectures to Working Men on the Causes of the Phe- 
 nomena of Organic Nature, 1863. (See Vol. II. of these 
 
254 BIOGENESIS AND ABIOGBNBSIS. vin 
 
 and bent downwards; and, if, after the contained 
 fluid has been carefully boiled, the tube is heated 
 sufficiently to destroy any germs which may be 
 present in the air which enters as the fluid cools, 
 the apparatus may be left to itself for any time 
 and no life will appear in the fluid. The reason is 
 plain. Although there is free communication be- 
 tween the atmosphere laden with germs and the 
 germless air in the flask, contact between the two 
 takes place only in the tube; and as the germs can- 
 not fall upwards, and there are no currents, they 
 never reach the interior of the flask. But if the 
 tube be broken short off where it proceeds from the 
 flask, and free access be thus given to germs falling 
 vertically out of the air, the fluid, which has re- 
 mained clear and desert for months, becomes, in a 
 few days, turbid and full of life. 
 
 These experiments have been repeated over and 
 over again by independent observers with entire 
 success; and there is one very simple mode of 
 seeing the facts for one's self, which I may as well 
 describe. 
 
 Prepare a solution (much used by M. Pasteur, 
 and often called " Pasteur's solution ") composed 
 of water with tartrate of ammonia, sugar, and 
 yeast-ash dissolved therein.*' Divide it into three 
 portions in as many flasks; boil all three for a 
 
 * Infusion of hay treated in the same way yields simi- 
 lar results; but as it contains organic matter, the argu- 
 ment which follows cannot be based upon it. 
 
VIII BIOGENESIS AND ABIOGBNESIS. 255 
 
 quarter of an hour; and, while the steam is pass- 
 ing out, stop the neek of one with a large plug of 
 cotton-wool, so that this also may be thoroughly 
 steamed. Now set the flasks aside to cool, and, 
 when their contents are cold, add to one of the 
 open ones a drop of filtered infusion of hay which 
 has stood for twenty-four hours, and is consequent- 
 ly full of the active and excessively minute organ- 
 isms known as Bacteria. In a couple of days of or- 
 dinary warm weather the contents of this flask will 
 be milky from the enormous multiplication of Bac- 
 teria. The other flask, open and exposed to the 
 air, will, sooner or later, become milky with Bac- 
 teria, and patches of mould may appear in it; 
 while the liquid in the flask, the neck of which is 
 plugged with cotton-wool, will remain clear for an 
 indefinite time. I have sought in vain for any ex- 
 planation of these facts, except the obvious one, 
 that the air contains germs competent to give rise 
 to Bacteria, such as those with which the first solu- 
 tion has been knowingly and purposely inoculated, 
 and to the moulA-Fungi. And I have not yet been 
 able to meet with any advocate of Abiogenesis who 
 seriously maintains that the atoms of sugar, tar- 
 trate of ammonia, yeast-ash, and water, under no 
 influence but that of free access of air and the ordi- 
 nary temperature, re-arrange themselves and give 
 rise to the protoplasm of Bacterium. But the al- 
 ternative is to admit that these Bacteria arise from 
 germs in the air; and if they are thus propagated, 
 
256 BIOGENESIS AND ABIOGBNESIS. vm 
 
 the burden of proof that other like forms are gen- 
 erated in a different manner, must rest with the 
 assertor of that proposition. 
 
 To sum up the effect of this long chain of evi- 
 dence: — 
 
 It is demonstrable that a fluid eminently fit for 
 the development of the lowest forms of life, but 
 which contains neither germs, nor any protein 
 compound, gives rise to living things in great 
 abundance if it is exposed to ordinary air; while 
 no such development takes place, if the air with 
 which it is in contact is mechanically freed from 
 the solid particles which ordinarily float in it, and 
 which may be made visible by appropriate means. 
 
 It is demonstrable that the great majority of 
 these particles are destructible by heat, and that 
 some of them are germs, or living particles, capable 
 of giving rise to the same forms of life as those 
 which appear when the fluid is exposed to unpuri- 
 fied air. 
 
 It is demonstrable that inoculation of the ex- 
 perimental fluid with a drop of liquid known to 
 contain living particles gives rise to the same 
 phenomena as exposure to unpurified air. 
 
 And it is further certain that these living par- 
 ticles are so minute that the assumption of their 
 suspension in ordinary air presents not the slight- 
 est difficulty. On the contrary, considering their 
 lightness and the wide diffusion of the organisms 
 which produce them, it is impossible to conceive 
 
VIII BIOGENESIS AND ABIOGENESIS. 257- 
 
 that they should not be suspended in the atmo- 
 sphere in myriads. 
 
 Thus the evidence, direct and indirect, in fa- 
 vour of Biogenesis for all known forms of life must, 
 I think, he admitted to be of great weight. 
 
 On the other side, the sole assertions worthy of 
 attention are that hermetically sealed fluids, which 
 have been exposed to great and long-continued 
 heat, have sometimes exhibited living forms of low 
 organisation when they have been opened. 
 
 The first reply that suggests itself is the proba- 
 bility that there must be some error about these 
 experiments, because they are performed on an 
 enormous scale every day with quite contrary re- 
 sults. Meat, fruits, vegetables, the very materials 
 of the most fermentable and putrescible infusions, 
 are preserved to the extent, I suppose I may say, 
 of thousands of tons every year, by a method which 
 is a mere application of Spallanzani's experiment. 
 The matters to be preserved are well boiled in a tin 
 case provided with a small hole, and this hole 
 is soldered up when all the air in the case has been 
 replaced by steam. By this method they may be 
 kept for years without putrefying, fermenting, or 
 getting mouldy. Now this is not because oxygen 
 is excluded, inasmuch as it is now proved that free 
 oxygen is not necessary for either fermentation or 
 putrefaction. It is not because the tins are ex- 
 hausted of air, for Vibriones and Bacteria live, as 
 
 Pasteur has shown, without air or free oxygen. It 
 203 
 
258 BIOGENESIS AND ABIOGENESIS. viii 
 
 is not because the boiled meats or vegetables are 
 not putrescible or fermentable, as those who have 
 had the misfortune to be in a ship supplied with 
 unskilfully closed tins well know. What is it, 
 therefore, but the exclusion of germs? I think 
 that Abiogenists are bound to answer this question 
 before they ask us to consider new experiments of 
 precisely the same order. 
 
 And in the next place, if the results of the ex- 
 periments I refer to are really trustworthy, it 
 by no means follows that Abiogenisis has taken 
 place. The resistance of living matter to heat 
 is known to vary within considerable limits, and 
 to depend, to some extent, upon the chemical 
 and physical qualities of the surrounding me- 
 dium. But if, in the present state of science, 
 the alternative is offered us, — either germs can 
 stand a greater heat than has been supposed, or 
 the molecules of dead matter, for no valid or in- 
 telligible reason that is assigned, are able to re- 
 arrange themselves into living bodies, exactly such 
 as can bei demonstrated to be frequently produced 
 in another way, — I cannot understand how choice 
 can be, even for a moment, doubtful. 
 
 But though I cannot express this conviction of 
 mine too strongly, I must carefully guard myself 
 against the supposition that I intend to suggest 
 that no such thing as Abiogenesis ever has taken 
 place in the past, or ever will take place in the 
 future. With organic chemistry, molecular phy- 
 
VIII BIOGENESIS AND ABIOGENESIS. 259 
 
 sics, and physiology yet in their infancy, and every 
 day making prodigious strides, I think it would be 
 the height of presumption for any man to say that 
 the conditions under which matter assumes the 
 properties we call "vital" may not, some day, 
 he artificially brought together. All I feel justi- 
 fied in affirming is, that I see no reason for be- 
 lieving that the feat has been performed yet. 
 
 And looking back through the prodigious vista 
 of the past, I find no record of the commencement 
 of life, and therefore I am devoid of any means of 
 forming a definite conclusion as to the conditions 
 of its appearance. Belief, in the scientific sense 
 of the word, is a serious matter, and needs strong 
 foundations. To say, therefore, in the admitted 
 absence of evidence, that I have any belief as to 
 the mode in which the existing forms of life have 
 originated, would be using words in a wrong sense. 
 But expectation is perinissible where belief is not; 
 and if it were given me to look beyond the abyss 
 of geologically recorded time to the still more re- 
 mote period when the earth was passing through 
 physical and chemical conditions, which it can no 
 no more see again than a man can recall his in- 
 fancy, I should expect to be a witness of the evo- 
 lution of living protoplasm from not living mat- 
 ter. I should expect to see it appear under forms 
 of great simplicity, endowed, like existing fungi, 
 with the power of determining the formation of 
 new protoplasm from such matters as ammonium 
 
260 BIOGENESIS AND ABIOGENBSIS. viii 
 
 carbonates, oxalates and tartrates, alkaline and 
 earthy phosphates, and water, without the aid of 
 light. That is the expectation to which analogi- 
 cal reasoning leads me; but I beg you once more 
 to recollect that I have no right to call my opinion 
 anything but an act of philosophical faith. 
 
 So much for the history of the progress of 
 Eedi's great doctrine of Biogenesis, which appears 
 to me, with the limitations I have expressed, to 
 be victorious along the whole line at the pres- 
 ent day. 
 
 As regards the second problem offered to us by 
 Eedi, whether Xenogenesis obtains, side by side 
 with Homogenesis, — ^whether, that is, there exist 
 not only the ordinary living things, giving rise to 
 offspring which run through the same cycle as 
 themselves, but also others, producing offspring 
 which are of a totally different character from 
 themselves, — the researches of two centuries have 
 led to a different result. That the grubs found in 
 galls are no product of the plants on which the 
 galls grow, but are the result of the introduction 
 of the eggs of insects into the substance of these 
 plants, was made out by Vallisnieri, Eeaumur, and 
 others, before the end of the first half of the eigh- 
 teenth century. The tapeworms, bladderworms, 
 and flukes continued to be a stronghold of the ad- 
 vocates of Xenogenesis for a much longer period. 
 Indeed, it is only within the last thirty years that 
 the splendid patience of Von Siebold, Van Bene- 
 
vni BIOGBKBSIS AND ABIOGENESIS. 261 
 
 den, Leuckart, Kiichenmeister, and other helmin- 
 thologists, has succeeded in tracing every such 
 parasite, often through the strangest wanderings 
 and metamorphoses, to an egg derived from a par- 
 ent, actually or potentially like itself; and the ten- 
 dency of inquiries elsewhere has all been in the 
 same direction. A plant may throw ofE bulbs, but 
 these, sooner or later, give rise to seeds or spores, 
 which develop into the original form. A ploype 
 may give rise to Medusae, or a pluteus to an Echin- 
 oderm, but the Medusa and the Echinoderm give 
 rise to eggs which produce polypes or plutei, and 
 they are therefore only stages in the cycle of life 
 of the species. 
 
 But if we turn to pathology, it offers us some 
 remarkable approximations to true Xenogenesis. 
 
 As I have already mentioned, it has been known 
 since the time of Vallisnieri and of Eeaumur, that 
 galls in plants, and tumours in cattle, are caused 
 by insects, which lay their eggs in those parts of 
 the animal or vegetable frame of which these mor- 
 bid structures are outgrowths. Again, it is a mat- 
 ter of familiar experience to everybody that mere 
 pressure on the skin will give rise to a corn. Now 
 the gall, the tumour, and the corn are parts of the 
 living body, which have become, to a certain de- 
 gree, independent and distinct organisms. Under 
 the influence of certain external conditions, ele- 
 ments of the body, which should have developed in 
 due subordination to its general plan, set up for 
 
262 BIOGBIfESIS AND ABIOGENESIS. vin 
 
 themselves and apply the noiarishment which they 
 receive to their own purposes. 
 
 From such innocent productions as corns and 
 warts, there are all gradations to the serious tu- 
 mours which, by their mere size and the mechani- 
 cal obstruction they cause, destroy the organism 
 out of which they are developed; while, finally, in 
 those terrible structures known as cancers, the 
 abnormal growth has acquired powers of reproduc- 
 tion and multiplication, and is only morphologic- 
 ally distinguishable from the parasitic worm, the 
 life of which is neither more nor less closely bound 
 up with that of the infested organism. 
 
 If there were a kind of diseased structure, the 
 histological elements of which were capable of 
 maintaining a separate and independent existence 
 out of the body, it seems to me that the shadowy 
 boundary between morbid growth and Xenogenesis 
 would be effaced. And I am inclined to think 
 that the progress of discovery has almost brought 
 us to this point already. I have been favoured by 
 Mr. Simon with an early copy of the last published 
 of the valuable " Eeport-s on the Public Health," 
 which, in his capacity of their medical of&cer, he 
 annually presents to the Lords of the Privy Coun- 
 cil. The appendix to this report contains an in- 
 troductory essay " On the Intimate Pathology of 
 Contagion," by Dr. Burdon-Sanderson, which is 
 one of the clearest, most comprehensive, and well- 
 reasoned discussions of a great question which has 
 
VIII BIOGENESIS AND ABIOGENBSIS. 263 
 
 come under my notice for a long time. I refer 
 you to it for details and for the authorities for the 
 statements I am about to make. 
 
 You are familiar with what happens in yaccina- 
 tion. A minute cut is made in the skin, and an 
 infinitesimal quantity of vaccine matter is inserted 
 into the wound. Within a certain time a vesicle 
 appears in the place of the wound, and the fluid 
 which distends this vesicle is vaccine matter, in 
 quantity a hundred or a thousandfold that which 
 was originally inserted. Now what has taken place 
 in the course of this operation? Has the vaccine 
 matter, by its irritative property, produced a mere 
 blister, the fluid of which has the same irritative 
 property? Or does the vaccine matter contain liv- 
 ing particles, which have grown and multiplied 
 where they have been planted? The observations 
 of M. Chauveau, extended and confirmed by Dr. 
 Sanderson himself, appear to leave no doubt upon 
 this head. Experiments, similar in principle to 
 those of Helmholtz on fermentation and putre- 
 faction, have proved that the active element in the 
 vaccine lymph is non-diffusible and consists of 
 minute particles not exceeding ^j^^-^th of an inch 
 in diameter, which are made visible in the lymph 
 by the microscope. Similar experiments have 
 proved that two of the most destructive of epizoot- 
 ic diseases, sheep-pox and glanders, are also de- 
 pendent for their existence and their propagation 
 upon extremely small living solid particles, to 
 
264 BIOGENESIS AND ABIOGENESIS. vin 
 
 which the title of microzymes is applied. An ani- 
 mal suffering under either of these terrible diseases 
 is a source of infection and contagion to others, 
 for precisely the same reason as a tub of ferment- 
 ing beer is capable of propagating its fermentation 
 by " infection " or " contagion," to fresh wort. In 
 both cases it is the solid living particles which are 
 efficient; the liquid in which they float, and at 
 the expense of which they live, being altogether 
 passive. Now arises the question, are these micro- 
 zymes the results of Eomogenesis, or of Xenogene- 
 sis? are they capable, like the TorulcB of yeast, of 
 arising only by the development of pre-existing 
 germs? or may they be, like the constituents of a 
 nut-gall, the results of a modification and individ- 
 ualisation of the tissues of the body in which they 
 are found, resulting from the operation of certain 
 conditions? Are they parasites in the zoological 
 sense, or are they merely what Virchow has called 
 " heterologous growths " ? It is obvious that this 
 question has the most profound importance, wheth- 
 er we look at it from a practical or from a theoreti- 
 cal point of view. A parasite may be stamped out 
 by destroying its germs, but a pathological product 
 can only be annihilated by removing the condi- 
 tions which give rise to it. 
 
 It appears to me that this great problem will 
 have to be solved for each zymotic disease separate- 
 ly, for analogy cuts two ways. I have dwelt upon 
 the analogy of pathological modification, which is 
 
Till BIOGENESIS AND ABIOGENESIS. • 265 
 
 in favour of the xenogenetic origin of microzymes; 
 but I must now speak of the equally strong analo- 
 gies in favo.ur of the origin of such pestiferous par- 
 ticles by the ordinary process of the generation of 
 like from like. 
 
 It is, at present, a well-established fact that 
 certain diseases, both of plants and of animals, 
 which have all the characters of contagious and in- 
 fectious epidemics, are caused by minute organ- 
 isms. The smut of wheat is a well-known instance 
 of such a disease, and it cannot be doubted that 
 the grape-disease and the potato-disease fall under 
 the same category. Among animals, insects are 
 wonderfully liable to the ravages of contagious and 
 infectious diseases caused by microscopic Fungi. 
 
 In autumn, it is not uncommon to see flies 
 motionless upon a window-pane, with a sort of 
 magic circle, in white, drawn round them. On 
 microscopic examination, the magic circle is found 
 to consist of innumerable spores, which have been 
 thrown off in all directions by a minute fungus 
 called Empusa muscw, the spore-forming filaments 
 of which stand out like a pile of velvet from the 
 body of the fly. These spore-forming filaments 
 are connected with others which fill the interior 
 of the fly's body like so much fine wool, having 
 eaten away and destroyed the creature's viscera. 
 This is the full-grown condition of the Empusa. 
 If traced back to its earliest stages, in flies which 
 are still active, and to all appearance healthy, it 
 
266 BIOGENESIS AND ABIOGBNESIS. vin 
 
 is found to exist in the form of minute corpuscles 
 which float in the blood of the fly. These multi- 
 ply and lengthen into filaments, at the expense of 
 the fly's substance; and when they have at last 
 killed the patient, they grow out of its body and 
 give off spores. Healthy flies shut up with dis- 
 eased ones catch this mortal disease, and perish 
 like the others. A most competent observer, M. 
 Cohn, who studied the development of the Em- 
 pusa very carefully, was Utterly unable to discover 
 in what manner the smallest germs of the Empusa 
 got into the fly. The spores could not be made 
 to give rise to such germs by cultivation; nor were 
 such germs discoverable in the air, or in the food 
 of the fly. It looked exceedingly like a case of 
 Abiogenesis, or, at any rate, of Xenogenesis; and 
 it is only quite recently that the real course of 
 events has been made out. It has been ascer- 
 tained, that when one of the spores falls upon the 
 body of a fly, it begins to germinate, and sends 
 out a process which bores its way through the fly's 
 skin; this, having reached the interior cavities of 
 its body, gives off the minute floating corpuscles 
 which are the earliest stage of the Empusa. The 
 disease is " contagious," because a healthy fly com- 
 ing in contact with a diseased one, from which the 
 spore-bearing filaments protrude, is pretty sure 
 to carry off a spore or two. It is " infectious " be- 
 cause the spores become scattered about all sorts of 
 matter in the neighbourhood of the slain flies. 
 
VIII BIOGENESIS AND ABIOGENESIS. 267 
 
 The silkworm has long been known to be sub- 
 ject to a very fatal and infectious disease called 
 the Muscardine. Audouin transmitted it by inoc- 
 ulation. This disease is entirely due to the devel- 
 opment of a fungus, Botrytis Bassiana, in the 
 body of the caterpillar; and its contagiousness and 
 infectiousness are accounted for in the same way 
 as those of the fly-disease. But, of late years, a 
 still more serious epizootic has appeared among 
 the silkworms; and I, may mention a few facts 
 which will give you some conception of the gravity 
 of the injury which it has inflicted on France 
 alone. 
 
 The production of silk has been for centuries 
 an important branch of industry in Southern 
 France, and in the year 1853 it had attained such 
 a magnitude that the annual produce of the French 
 sericulture was estimated to amount to a tenth of 
 that of the whole world, and represented a money- 
 value of 117,000,000 francs, or nearly five millions 
 sterling. What may be the sum which would 
 represent the money-value of all the industries 
 connected with the working up of the raw silks 
 thus produced, is more than I can pretend to esti- 
 mate. Suffice it to say that the city of Lyons is 
 built upon French silk as much as Manchester was 
 upon American cotton before the civil war. 
 
 Silkworms are liable to many diseases; and, 
 even before 1853, a peculiar epizootic, frequently 
 accompanied by the appearance of dark spots upon 
 
268 BIOGENESIS AND ABIOGENESIS. viii 
 
 the skin (whence the name of " Pebrine " which 
 it has received), had been noted for its mortahty. 
 But in the years following 1853 this malady broke 
 out with such extreme violence, that, in 1858, the 
 silk-crop was reduced to a third of the amount 
 which it had reached in 1853; and, up till within 
 the last year or two, it has never attained half the 
 yield of 1853. This means not only that the great 
 number of people engaged in silk growing are some 
 thirty millions sterling poorer than they might 
 have been; it means not only that high prices 
 have had to be paid for imported silkworm eggs, 
 and that, after investing his money in them, in 
 paying for mulberry-leaves and for attendance, the 
 cultivator has constantly seen his silkworms perish 
 and himself plunged in ruin; but it means that 
 the looms of Lyons have lacked employment, and 
 that, for years, enforced idleness and misery have 
 been the portion of a vast population which, in for- 
 mer days, was industrious and well-to-do. 
 
 In 1858 the gravity of the situation caused the 
 French Academy of Sciences to appoint Commis- 
 sioners, of whom a distinguished naturalist, M. de 
 Quatrefages, was one, to inquire into the nature of 
 this disease, and, if possible, to devise some means 
 of staying the plague. In reading the Egport * 
 made by M. de Quatrefages in 1859, it is exceed- 
 ingly interesting to observe that his elaborate study 
 
 * 
 * Etudes sur les Maladies actuelles des Ters a Sole, 
 p. 53. 
 
VIII BIOGENESIS AND ABIOGENESIS. 269 
 
 of the Pebrine forced the conviction upon his mind 
 that, in its mode of occurrence and propagation, 
 the disease of the silkworm is, in every respect, 
 comparable to the cholera, among mankind. But 
 it differs from the cholera, and so far is a more 
 formidable malady,. in being hereditary, and in be- 
 ing, under some circumstances, contagious as well 
 as infectious. 
 
 The Italian naturalist, Filippi, discovered in 
 the blood of the silkworms affected by this strange 
 disorder a multitude of cylindrical corpuscles, each 
 about -s-ff^fj-jfth of an inch long. These have been 
 carefully studied by Lebert, and named by him 
 Panhistophyton; for the reason that in subjects in 
 which the disease is strongly developed, the cor- 
 puscles swarm in every tissue and organ of the 
 body, and even pass into the undeveloped eggs of 
 the female moth. But are these corpuscles causes, 
 or mere concomitants, of the disease? Some natu- 
 ralists took one view and some another; and it was 
 not until the French Government, alarmed by the 
 continued ravages of the malady, and the ineffi- 
 ciency of the remedies which had been suggested, 
 despatched M. Pasteur to study it, that the ques- 
 tion received its final settlement; at a great sacri- 
 fice, not only of the time and peace of mind of that 
 eminent philosopher, but, I regret to have to add, 
 of his health. 
 
 But the sacrifice has not been in vain. It is 
 now certain that this devastating, cholera-like Pe- 
 
270 BIOGENESIS AND ABIOGENESIS. vm 
 
 brine, is the effect of the growth and multiplica- 
 tion of the Panhistophyton in the silkworm. It is 
 contagious and infectious, because the corpuscles 
 of the Panhistophyton pass away from the bodies 
 of the diseased caterpillars, directly or indirectly, 
 to the alimentary canal of healthy silkworms in 
 their neighbourhood; it is hereditary because the 
 corpuscles enter into the eggs while they are being 
 formed, and consequently are carried within them 
 when they are laid; and for this reason, also, it 
 presents the very singular peculiarity of being in- 
 herited only on the mother's side. There is not 
 a single one of all the apparently capricious and 
 unaccountable phenomena presented by the Pe- 
 brine, but has received its explanation from the 
 fact that the disease is the result of the presence of 
 the microscopic organism Panhistophyton. 
 
 Such being the facts with respect to the Pe- 
 brine, what are the indications as to the method of 
 preventing it? It is obvious that this depends 
 upon the way in which the Panhistophyton is gen- 
 erated. If it may be generated by Abiogenesis, or 
 by Xenogenesis, within the silkworm or its moth, 
 the extirpation of the disease must depend upon 
 the prevention of the occurrence of the conditions 
 under which this generation takes place. But if, 
 on the other hand, the Panhistophyton is an inde- 
 pendent organism, which is no more generated by 
 the silkworm than the mistletoe is generated by 
 the apple-tree or the oak on which it grows, though 
 
viii BIOGENESIS AKDABIO&ENESIS. 271 
 
 it may need the silkworm for its development in 
 the same way as the mistletoe needs the tree, then 
 the indications are totally different. The sole thing 
 to be done is to get rid of and keep away the germs 
 of the Panhistophyton. As might be imagined, 
 from the course of his previons investigations, M. 
 Pasteur was led to believe that the latter was the 
 right theory; and, guided by that theory, he has 
 devised a method of extirpating the disease, which 
 has proved to be completely successful wherever it 
 has been properly carried out. 
 
 There can be no reason, then, for doubting that, 
 among insects, contagious and infectious diseases, 
 of great malignity, are caused by minute organisms 
 which are produced from pre-existing germs, or by 
 homogenesis; and there is no reason, that I know 
 of, for believing that what happens in insects may 
 not take place in the highest animals. Indeed, 
 there is already strong evidence that some- diseases 
 of an extremely malignant and fatal character to 
 which man is subject, are as much the work of 
 minute organisms as is the Pebrine. I refer for 
 this evidence to the very striking facts adduced by 
 Professor Lister in his various well-known publi- 
 cations on the antiseptic method of treatment. It 
 appears to me impossible to rise from the perusal 
 of those publications without a strong conviction 
 that the lamentable mortality which so frequently 
 dogs the footsteps of the most skilful operator, and 
 those deadly consequences of wounds and injuries 
 
272 BIOGENESIS AND ABIOGENESIS. viii 
 
 which seem to haunt the very walls of great hos- 
 pitals, and are, even now, destroying more men 
 than die of bullet or bayonet, are due to the impor- 
 tation of minute organisms into wounds, and their 
 increase and multiplication; and that the surgeon 
 who saves most lives will be he who best works 
 out the practical consequences of the hypothesis of 
 Eedi. 
 
 I commenced this Address by asking you to 
 follow me in an attempt to trace the path which 
 has been followed by a scientific idea, in its long 
 and slow progress from the position of a probable 
 hypothesis to that of an established law of nature. 
 Our survey has not taken us into very attractive 
 regions; it has lain, chiefly, in a land flowing with 
 the abominable, and peopled with mere grubs and 
 mouldiness. And it may be imagined with what 
 smiles and shrugs, practical and serious contempo- 
 raries of Eedi and of Spallanzani may have com- 
 mented on the waste of their high abilities in toil- 
 ing at the solution of problems which, though 
 curious enough in themselves, could be of no con- 
 ceivable utility to mankind. 
 
 Nevertheless, you will have observed that be- 
 fore we had travelled very far upon our road, there 
 appeared, on the right hand and on the left, fields 
 laden with a harvest of golden grain, immediately 
 convertible into those things which the most solid- 
 ly practical men will admit to have value — ^viz., 
 money and life. 
 
VIII BIOGENESIS AND ABIOGENESIS. 273 
 
 The direct loss to France caused by the Pebrine 
 in seventeen years cannot be estimated at less than 
 fifty millions sterling; and if we add to this what 
 Eedi's idea, in Pasteur's hands, has done for the 
 wine-grower and for the vinegar-maker, and try to 
 capitalise its value, we shall find that it will go a 
 long way towards repairing the money losses 
 caused by the frightful and calamitous war of this 
 autumn. And as to the equivalent of Eedi's 
 thought in life, how can we over-estimate the value 
 of that knowledge of the nature of epidemic and 
 epizootic diseases, and consequently of the means 
 of checking, or eradicating them, the dawn of 
 which has assuredly commenced? 
 
 Looking back no further than ten years, it is 
 possible to select three (1863, 1864, and 1869) in 
 which the total number of deaths from scarlet- 
 fever alone amounted to ninety thousand. That is 
 the return of killed, the maimed and disabled be- 
 ing left out of sight. Why, it is to be hoped that 
 the list of killed in the present bloodiest of all wars 
 will not amount to more than this! But the facts 
 which I have placed before you must leave the 
 least sanguine without a doubt that the nature and 
 the causes of this scourge will, one day, be as well 
 understood as those of the Pebrine are now; and 
 that the long-suffered massacre of our innocents 
 will come to an end. 
 
 And thus mankind will have one more admoni- 
 tion that " the people perish for lack of knowl- 
 204 
 
274 BIOGENESIS AND ABIOGENESIS. viii 
 
 edge "; and that the alleviation of the miseries, 
 and the promotion of the welfare, of men must 
 be sought, by those who will not lose their pains, 
 in that diligent, patient, loving study of all the 
 multitudinous aspects of Nature, the results of 
 which constitute exact knowledge, or Science. 
 It is the justification and the glory of this great 
 meeting that it is gathered together for no other 
 object than the advancement of the moiety of 
 science which deals with those phenomena of 
 nature which we call physical. May its en- 
 deavours be crowned with a full measure of 
 success! 
 
IX. 
 
 GEOLOGICAL CONTEMPOEANEITY AND 
 PEKSISTENT TYPES OP LIFE. 
 
 [1863.] 
 
 Meechants occasionally go through a whole- 
 some, though troublesome and not always satisfac- 
 tory, process which they term "taking stock." 
 After all the excitement of speculation, the pleas- 
 ure of gain, and the pain of loss, the trader makes 
 up his mind to face facts and to learn the exact 
 quantity and quality of his solid and reliable pos- 
 sessions. 
 
 The man of science does well sometimes to imi- 
 tate this procedure; and, forgetting for the time 
 the importance of his own small winnings, to re- 
 examine the common stock in trade, so that he may 
 make sure how far the stock of bullion in the cellar 
 ^on the faith of whose existence so much paper 
 has been circulating — is really the solid gold of 
 truth. 
 
 The Anniversary Meeting of the Geological 
 Society seems to be an occasion well suited for an 
 undertaking of this kind — for an inquiry, in fact, 
 
 275 
 
276 GEOLOGICAL CONTEMPORANEITY. ix 
 
 into the nature and the value of the present re- 
 sults of palaeontological investigation; and the 
 more so, as all those who have paid close attention 
 to the late multitudinous discussions in which 
 palaeontology is implicated, must have felt the 
 urgent necessity of some such scrutiny. 
 
 First in order, as the most definite and unques- 
 tionable of all the results of palaeontology, must 
 be mentioned the immense extension and impulse 
 given to botany, zoology, and comparative anatomy, 
 by the investigation of fossil remains. Indeed, 
 the mass of biological facts has been so greatly in- 
 creased, and the range of biological speculation has 
 been so vastly widened, by the researches of the 
 geologist and palteontologist, that it is to be 
 feared there are naturalists in existence who look 
 upon geology as Brindley regarded rivers. " Riv- 
 ers," said the great engineer, " were made to feed 
 canals; " and geology, some seem to think, was 
 solely created to advance comparative anatomy. 
 
 Were such a thought justifiable, it could hard- 
 ly expect to be received with favour by this as- 
 sembly. But it is not justifiable. Your favourite 
 science has her own great aims independent of all 
 others; and if, notwithstanding her steady devo- 
 tion to her own progress, she can scatter such rich 
 alms among her sisters, it should be remembered 
 that her charity is of the sort that does not im- 
 poverish, but " blesseth him that gives and him 
 that takes." 
 
IX GEOLOGICAL CONTEMPORANEITY. 277 
 
 Eegard the matter as we will, however, the 
 facts remain. Nearly 40,000 species of animals 
 and plants have been added to the Systema Na- 
 turae by palaaontological research. This is a living 
 population equivalent to that of a new continent 
 in mere number; equivalent to that of a new hem- 
 isphere, if we take into account the small popula- 
 tion of insects as yet found fossil, and the large 
 proportion and peculiar organisation of many of 
 the Vertebrata. 
 
 But, beyond this, it is perhaps not too much 
 to say that, except for the necessity of interpreting 
 palseontologieal facts, the laws of distribution 
 would have received less careful study; while few 
 comparative anatomists (and those not of the first 
 order) would have been induced by mere love of 
 detail, as such, to study the minutiaa of osteology, 
 were it not that in such minutiaa lie the only keys 
 to the most interesting riddles- offered by the ex- 
 tinct animal world. 
 
 These assuredly are great and solid gains. 
 Surely it is a matter for no small congratulation 
 that in half a century (for palaeontology, though it 
 dawned earlier, came into full day only with Cu- 
 vier) a subordinate branch of biology should have 
 doubled the value and the interest of the whole 
 group of sciences to which it belongs. 
 
 But this is not all. Allied with geology, 
 palaeontology has established two laws of inesti- 
 mable importance: the first, that one and the same 
 
278 GEOLOGICAL CONTEMPORANEITY. ix 
 
 area of the earth's surface has been successively 
 occupied by very different kinds of living be- 
 ings; the second, that the order of succession es- 
 tablished in one locality holds good, approximate- 
 ly, in all. 
 
 The first of these laws is universal and irre- 
 versible; the second is an induction from a vast 
 number of observations, though it may possibly, 
 and even probably, have to admit of exceptions. 
 As a consequence of the second law, it follows 
 that a peculiar relation frequently subsists between 
 series of strata containing organic remains, in dif- 
 ferent localities. The series resemble one another 
 not only in virtue of a general resemblance of the 
 organic remains in the two, but also in virtue of a 
 resemblance in the order and character of the serial 
 succession in each. There is a resemblance of 
 arrangement; so that the separate terms of each 
 series, as well as the whole series, exhibit a corre- 
 spondence. 
 
 Succession implies time; the lower members 
 of an undisturbed series of sedimentary rocks are 
 certainly older than the upper; and when the no- 
 tion of age was once introduced as the equivalent 
 of succession, it was no wonder that correspond- 
 ence in succession came to be looked upon as a 
 correspondence in age, or " contemporaneity." 
 And, indeed, so long as relative age only is spoken 
 of, correspondence in succession is correspondence 
 in age; it is relative contemporaneity. 
 
IS GEOLOGICAL CONTEMPORANEITY. 279 
 
 But it" would have been very much better for 
 geology if so loose and ambiguous a word as " con- 
 temporaneous " had been excluded from her ter- 
 minology, and if, in its stead, some term express- 
 ing similarity of serial relation, and excluding 
 the notion of time altogether, had been employed 
 to denote correspondence in position, in two or 
 more series of strata. 
 
 In anatomy, where such correspondence of po- 
 sition has constantly to be spoken of, it is denoted 
 by the word " homology " and its derivatives; and 
 for Geology (which after all is only the anatomy 
 and physiology of the earth) it might be well to 
 invent some single word, such as " homotaxis " 
 (similarity of order), in order to express an essen- 
 tially similar idea. This, however, has not been 
 done, and most probably the inquiry will at once 
 be made — To what end burden science with a new 
 and strange term in place of one old, familiar, and 
 part of our common language? 
 
 The reply to this question will become obvious 
 as the inquiry into the results of palaeontology is 
 pushed further. 
 
 Those whose business it is to acquaint them- 
 selves specially with the works of palaeontologists, 
 in fact, will be fully aware that very few, if any, 
 would jest satisfied with such a statement of the 
 conclusions of their branch of biology as that which 
 has just been given. 
 
 Our standard repertories of palEeontology .pro- 
 
280 GEOLOGICAL CONTEMPORAKEITY, tx 
 
 fess to teach us far higher things — to disclose the 
 entire succession of living forms upon the surface 
 of the globe; to tell us of a wholly different dis- 
 tribution of climatic conditions in ancient times; 
 to reveal the character of the first of all living ex- 
 istences; and to trace out the law of progress from 
 them to us. 
 
 It may not be unprofitable to bestow on these 
 professions a somewhat more critical examination 
 than they have hitherto received, in order to as- 
 certain how far they rest on an irrefragable basis; 
 or whether, after all, it might not be well for 
 palaeontologists to learn a little more carefully that 
 scientific " ars artium," the art of saying " I don't 
 know." And to this end let us define somewhat 
 more exactly the extent of these pretensions of 
 palaeontology. 
 
 Every one is aware that Professor Bronn's 
 " Untersuchungen " and Professor Pictet's " Tra- 
 ite de Paleontologie " are works of standard 
 authority, familiarly consulted by every working 
 palaeontologist. It is desirable to speak of these 
 excellent books, and of their distinguished authors, 
 with the utmost respect, and in a tone as far as 
 possible removed from carping criticism; indeed, 
 if they are specially cited in this place, it is merely 
 in justification of the assertion that the following 
 proposition, which may be found implicitly, or ex- 
 plicitly, in the works in question, are regarded by 
 the mass of palaeontologists and geologists, not only 
 
IX GEOLOGICAL CONTEMPORANEITY. 281 
 
 on the Continent but in this country, as expressing 
 some of the best-established results of palaeontol- 
 ogy. Thus: — 
 
 Animals and plants began their existence to- 
 gether, not long after the commencement of the 
 deposition of the sedimentary rocks; and then 
 succeeded one another, in such a manner, that 
 totally distinct faunae and florae occupied the whole 
 surface of the earth, one after the other, and during 
 distinct epochs of time. 
 
 A geological formation is the sum of all the 
 strata deposited over the whole surface of the 
 earth during one of these epochs: a geological 
 fauna or flora is the sum of all the species of ani- 
 mals or plants which occupied the whole surface 
 of the globe, during one of these epochs. 
 
 The population of the earth's surface was at 
 firct very similar in all parts, and only from the 
 middle of the Tertiary epoch onwards, began to 
 show a distinct distribution in zones. 
 
 The constitution of the original population, as 
 well as the numerical proportions of its members, 
 indicates a warmer and, on the whole, somewhat 
 tropical climate, which remained tolerably equable 
 throughout the year. The subsequent distribu- 
 tion of living beings in zones is the result of a 
 gradual lowering of the general temperature, 
 which first began to be felt at the poles. 
 
 It is not now proposed to inquire whether these 
 
282 GEOLOGICAL CONTEMPOEANEITY. ix 
 
 doctrines are true or false; but to direct your at- 
 tention to a much simpler though very essential 
 preliminary question — ^What is their logical basis? 
 what are the fundamental assumptions upon which 
 they all logically depend? and what is the evi- 
 dence on which those fundamental propositions de- 
 mand our assent? 
 
 These assumptions are two: the first, that the 
 commencement of the geological record is coeval 
 with the commencement of life on the globe; 
 the second, that geological contemporaneity is the 
 same thing as chronological synchrony. Without 
 the first of these assumptions there would of course 
 be no ground for any statement respecting the 
 commencement of life; without the second, all 
 the other statements cited, every one of which im- 
 plies a knowledge of the state of different parts of 
 the earth at one and the same time, will be no less 
 devoid of demonstration. 
 
 The first assumption obviously rests entirely on 
 negative evidence. This is, of course, the only 
 evidence that ever can be available to prove the 
 commencement of any series of phenomena; but, 
 at the same time, it must be recollected that the 
 value of negative evidence depends entirely on the 
 amount of positive corroboration it receives. If 
 A B wishes to prove an alibi, it is of no use for 
 him to get a thousand witnesses simply to swear 
 that they did not see him in such and such a place, 
 unless the witnesses are prepared to prove that 
 
IX GEOLOGICAL CONTEMPORANEITY. 283 
 
 they must have seen him had he been there. But 
 the evidence that animal life commenced with the 
 Lingula-flags, e.g., would seem to be exactly of 
 this unsatisfactory uncorroborated sort. The 
 Cambrian witnesses simply swear they " haven't 
 seen anybody their way "; upon which the counsel 
 for the other side immediately puts in ten or twelve 
 thousand feet of Devonian sandstones to make oath 
 they never saw a fish or a mollusk, though all the 
 world knows there were plenty in their time. 
 
 But when it is urged that, though the Devo- 
 nian rocks in one part of the world exhibit no fos- 
 sils, in another they do, while the lower Cambrian 
 rocks nowhere exhibit fossils, and hence no living 
 being could have existed in their epoch. 
 
 To this there are two replies: the first that the 
 observational basis of the assertion that the lowest 
 rocks are nowhere fossiliferous is an amazingly 
 small one, seeing how very small an area, in com- 
 parison to that of the whole world, has yet been 
 fully searched; the second, that the argument is 
 good for nothing unless the unfossiliferous rocks 
 in question were not only contemporaneous in the 
 geological sense, but synchronous in the chrono- 
 logical sense. To use the aliii illustration again. 
 If a m.an wishes to prove he was in neither of 
 two places, A and B, on a given day, his witnesses 
 for each place must be prepared to answer for the 
 whole day. If they can only prove that he was 
 not at A in the morning, and not at B in the after- 
 
284 GEOLOGICAL CONTEMPORANEITY. vs. 
 
 noon, the evidence of his absence from both is 
 nil, because he might have been at B in the morn- 
 ing and at A in the afternoon. 
 
 Thus everything depends upon the validity of 
 the second assumption. And we must proceed to 
 inquire what is the real meaning of the word 
 " contemporaneous " as employed by geologists. 
 To this end a concrete example may be taken. 
 
 The Lias of England and the Lias of Germany, 
 the Cretaceous rocks of Britain and the Cretaceous 
 rocks of Southern India, are termed by geologists 
 " Contemporaneous " formations; but whenever 
 any thoughtful geologist is asked whether he 
 means to say that they were deposited synchron- 
 ously, he says, " No, — only within the same great 
 epoch." And if, in pursuing the inquiry, he is 
 asked what may be the approximate value in time 
 of a " great epoch " — whether it means a hundred 
 years, or a thousand, or a million, or ten million 
 years — his reply is, " I cannot tell." 
 
 If the further question be put, whether physi- 
 cal geology is in possession of any method by 
 which the actual synchrony (or the reverse) of any 
 two distant deposits can be ascertained, no such 
 method can be heard of; it being admitted by all 
 the best authorities that neither similarity of min- 
 eral composition, nor of physical character, nor 
 even direct continuity of stratum, are absolute 
 proofs of the synchronism of even approximated 
 sedimentary strata: while, for distant deposits, 
 
IX GEOLOGICAL CONTEMPORANEITY. 285 
 
 there seems to be no kind of physical evidence at- 
 tainable of a nature competent to decide whether 
 such deposits were formed simultaneously, or 
 whether they possess any given difference of an- 
 tiquity. To return to an example already given: 
 All competent authorities will probably assent to 
 the proposition that physical geology does not en- 
 able us in any way to reply to this question — 
 Were the British Cretaceous rocks deposited at the 
 same time as those of India, or are they a million 
 of years younger or a million of years older? 
 
 Is palaeontology able to succeed where physical 
 geology fails? Standard writers on palaeontology, 
 as has been seen, assume that she can. They take 
 it for granted, that deposits containing similar or- 
 ganic remains are synchronous — at any rate in a 
 broad sense; and yet, those who will study the 
 eleventh and twelfth chapters of Sir Henry De La 
 Beche's remarkable " Eesearches in Theoretical 
 Geology," published now nearly thirty years ago, 
 and will carry out the arguments there most lumin- 
 ously stated, to their logical consequences, may 
 very easily convince themselves that even absolute 
 identity of organic contents is no proof of the syn- 
 chrony of deposits, while absolute diversity is no 
 proof of difference of date. Sir Henry De La 
 Beche goes even further, and adduces conclusive 
 evidence to show that the different parts of one 
 and the same stratum, having a similar composi- 
 tion throughout, containing the same organic re- 
 
286 GEOLOGICAL CONTBMPOEANEITY. ix 
 
 mains, and having similar beds above and below it, 
 may yet differ to any conceivable extent in age. 
 
 Edward Forbes was in the habit of asserting 
 that the similarity of the organic contents of dis- 
 tant formations was prima facie evidence, not of 
 their similarity, but of their difference of age; and 
 holding as he did the doctrine of single specific 
 centres, the conclusion was as legitimate as any 
 other; for the two districts must have been occu- 
 pied by migration from one of the two, or from an 
 intermediate spot, and the chances against exact 
 coincidence of migration and of imbedding are 
 infinite. 
 
 In point of fact, however, whether the hypo- 
 thesis of single or of multiple specific centres be 
 adopted, similarity of organic contents cannot pos- 
 sibly afford any proof of the synchrony of the 
 deposits which contain them; on the contrary, it 
 is demonstrably compatible with the lapse of the 
 most prodigious intervals of time, and with the in- 
 terposition of vast changes in the organic and in- 
 organic worlds, between the epochs in which such 
 deposits were formed. 
 
 On what amount of similarity of their faunffi is 
 the doctrine of the contemporaneity of the Euro- 
 pean and of the North American Silurians based? 
 In the last edition of Sir Charles Lyell's " Ele- 
 mentary Geology " it is stated, on the authority of 
 a former President of this Society, the late Daniel 
 Sharpe, that between 30 and 40 per cent, of the 
 
IX GEOLOGICAL CONTEMPORANEITY. 287 
 
 species of Silurian Mollusca are common to both 
 sides of the Atlantic. By way of due allowance 
 for further discovery, let us double the lesser num- 
 ber and suppose that 60 per cent, of the species are 
 common to the North American and the British 
 Silurians. Sixty per cent, of species in common 
 is, then, proof of contemporaneity. 
 
 Now suppose that, a million or two of years 
 hence, when Britain has made another dip be- 
 neath the sea and has come up again, some geolo- 
 gist applies this doctrine, in comparing the strata 
 laid bare by the upheaval of the bottom, say, of 
 St. George's Channel with what may then remain 
 of the Suffolk Crag. Eeaconing in the same way, 
 'he will at once decide the Suffolk Crag and the St. 
 George's Channel beds to be contemporaneous; 
 although we happen to know that a vast period 
 (even in the geological sense) of time, and physical 
 changes of almost unprecedented extent, separate 
 the two. 
 
 But if it be a demonstrable fact that strata con- 
 taining more than 60 or 70 per cent, of species of 
 Mollusca in common, and comparatively close to- 
 gether, may yet be separated by an amount of 
 geological time sufficient to allow of some of the 
 greatest physical changes the world has seen, what 
 becomes of that sort of contemporaneity the sole 
 evidence of which is a similarity of facies, or the 
 identity of half a dozen species, or of a good many 
 genera? 
 
288 GEOLOGICAL CONTEMPORANEITY. ix 
 
 And yet there is no better evidence for the 
 contemporaneity assumed by all who adopt the 
 hypothesis of universal faunae and florae, of a uni- 
 versally uniform climate, and of a sensible cooling 
 of the globe during geological time. 
 
 There seems, then, no escape from the admis- 
 sion that neither physical geology, nor palaeontol- 
 ogy, possesse any method by which the absolute 
 synchronism of. two strata can be demonstrated. 
 All that geology can prove is local order of succes- 
 sion. It is mathematically certain that, in any 
 given vertical linear section of an undisturbed se- 
 ries of sedimentary deposits, the bed which lies 
 lowest is the oldest. In many other vertical linear 
 sections of the same series, of course, correspond- 
 ing beds will occur in a similar order; but, how- 
 ever great may be the probability, no man can say 
 with absolute certainty that the beds in the two 
 sections were synchronously deposited. For areas 
 of moderate extent, it is doubtless true that no 
 practical evil is likely to result from assuming the 
 corresponding beds to be synchronous or strictly 
 contemporaneous; and there are multitudes of 
 accessory circumstances which may fully justify 
 the assumption of such synchrony. But the mo- 
 ment the geologist has to deal with large areas, or 
 with completely separated deposits, the mischief of 
 confounding that " homotaxis " or " similarity of 
 arrangement," which can be demonstrated, with 
 "synchrony" or "identity of date," for which 
 
IX GEOLOaiCAL CONTEMPORANEITY. 289 
 
 there is not a shadow of proof, under the one com- 
 mon term of " contemporaneity " becomes incal- 
 culable, and proves the constant source of gratui- 
 tous speculations. 
 
 For anything that geology or paleontology is 
 able to show to the contrary, a Devonian fauna 
 and flora in the British Islands may have been 
 contemporaneous with Silurian life in North 
 America, and with a Carboniferous fauna and 
 flora in Africa. Geographical provinces and zones 
 may have been as distinctly marked in the Palaeo- 
 zoic epoch as at present, and those seemingly sud- 
 den appearances of new genera and species, which 
 we ascribe to new creation, may be simple results 
 of migration. 
 
 It may be so; it may be otherwise. In the 
 present condition of our knowledge and of our 
 methods, one verdict — " not proven, and not prov- 
 able " — must be recorded against all the grand hy- 
 potheses of the palaeontologist respecting the gen- 
 eral succession of life on the globe. The order 
 and nature of terrestrial life, as a whole, are open 
 questions. Geology at present provides us with 
 most valuable topographical records, but she has 
 not the means of working them into a universal 
 history. Is such a universal history, then, to be 
 regarded as unattainable? Are all the grandest 
 and most interesting problems which offer them- 
 selves to the geological student essentially insolu- 
 ble.? Is he in the position of a scientific Tantalus 
 205 
 
290 GEOLOGICAL CONTBMPOKANEITY. ix 
 
 — doomed always to thirst for a knowledge which 
 he cannot obtain? The reverse is to be hoped; 
 nay, it may not be impossible to indicate the source 
 whence help will come. 
 
 In commencing these remarks, mention was 
 made of the great obligations under which the 
 naturalist lies to the geologist and paleontologist. 
 Assuredly the time will come when these obliga- 
 tions will be repaid tenfold, and when the maze 
 of the world's past history, through which the pure 
 geologist and the pure palaeontologist find no guid- 
 ance, will be securely threaded by the clue fur- 
 nished by the naturalist. 
 
 All who are competent to express an opinion on 
 the subject are, at present, agreed that the mani- 
 fold varieties of animal and vegetable form have 
 not either come into existence by chance, nor re- 
 sult from capricious exertions of creative power; 
 but that they have taken place in a definite order, 
 the statement of which order is what men of sci- 
 ence term a natural law. Whether such a law is 
 to be regarded as an expression of the mode of 
 operation of natural forces, or whether it is simply 
 a statement of the manner in which a supernatural 
 power has thought fit to act, is a secondary ques- 
 tion, so long as the existence of the law and the 
 possibility of its discovery by the human intellect 
 are granted. But he must be a half-hearted phi- 
 losopher who, believing in that possibility, and hav- 
 ing watched the gigantic strides of the biological 
 
IX GEOLOGICAL COKTEMPORANEITy. 291 
 
 sciences during the last twenty years, doubts that 
 science will sooner or later make this further step, 
 so as to become possessed of the law of evolution 
 of organic forms — of the unvarying order of that 
 great chain of causes and effects of which all or- 
 ganic forms, ancient and modern, are the links. 
 And then, if ever, we shall be able to begin to 
 discuss, with profit, the questions respecting the 
 commencement of life, and the nature of the suc- 
 cessive populations of the globe, which so inanj 
 seem to think are already answered. 
 
 The preceding arguments make no particular 
 claim to novelty; indeed they have been floating 
 more or less distinctly before the minds of geolo- 
 gists for the last thirty years; and if, at the pres- 
 ent time, it has seemed desirable to give them 
 more definite and systematic expression, it is be- 
 cause palseontology is every day assuming a greater 
 importance, and now requires to rest on a basis 
 the firmness of which is thoroughly well assured. 
 Among its fundamental conceptions, there must 
 be no confusion between what is certain and what 
 is more or less probable.* But, pending the con- 
 struction of a surer foundation than palseontology 
 now possesses, it may be instructive, assuming for 
 the nonce the general correctness of the ordinary 
 hypothesis of geological contemporaneity, to con- 
 
 * " Le plus grand service qu'on puisse rendre a la 
 science est d'y faire place avant d'y rien construire." — 
 
 CUVIEB. 
 
292 GEOLOGICAL CONTEMPORANEITY. ix 
 
 sider whether the deductions which are ordinarily 
 drawn from the whole body of palseontological facts 
 are justifiable. 
 
 The evidence on which such conclusions are 
 based is of two kinds, negative and positive. The 
 value of negative evidence, in connection with this 
 inquiry, has been so fully and clearly discussed in 
 an address from the chair of this Society,* which 
 none of us has forgotten, that nothing need at 
 present be said about it; the more, as the con- 
 siderations which have been laid before you have 
 certainly not tended to increase your estimation 
 of such evidence. It will be preferable to turn to 
 the positive facts of palasontology, and to inquire 
 what they tell us. 
 
 We are all accustomed to speak of the number 
 and the extent of the changes in the living popu- 
 lation of the globe during geological time as some- 
 thing enormous; and indeed they are so, if we 
 regard only the negative differences which sepa- 
 rate the older rocks from the more modern, and if 
 we look upon specific and generic changes as great 
 changes, which from one point of view, they truly 
 are. But leaving the negative differences out of 
 consideration, and looking only at the positive data 
 furnished by the fossil world from a broader point 
 of view — from that of the comparative anatomist 
 who has made the study of the greater modifica- 
 
 * Anniversary Address for 1851, Quart. Journ. Geol. 
 Soc. vol. vii. 
 
IX GEOLOGICAL CONTEMPORANEITY. 293 
 
 tions of animal form his chief business — a surprise 
 of another kind dawns upon the mind; and under 
 this aspect the smallness of the total change be- 
 comes as astonishing as was its greatness under 
 the other. 
 
 There are two hundred known orders of plants; 
 of these not one is certainly known to exist ex- 
 clusively in the fossil state. The whole lapse of 
 geological time has as yet yielded not a single new 
 ordinal type of vegetable structure.* 
 
 The positive change in passing from the recent 
 to the ancient animal world is greater, but still 
 singularly small. No fossil animal is so distinct 
 from those now living as to require to be arranged 
 even in a separate class from those which contain 
 existing forms. It is only when we come to the 
 orders, which may be roughly estimated at about 
 a hundred and thirty, that we meet with fossil ani- 
 mals so distinct from those now living as to rer 
 quire orders for themselves; and these do not 
 amount, on the most liberal estimate, to more than 
 about 10 per cent, of the whole. 
 
 There is no certainly known extinct order of 
 Protozoa; there is but one among the Coelenterata 
 — that of the rugose corals; there is none among 
 the Mollusca; there are three, the Cystidea, Blas- 
 toidea, and Edrioasterida, among the Echinoderms; 
 and two, the Trilobita and Eurypterida, among the 
 
 * See Hooker's Introductory Essay to the Flora of 
 Tasmania, p. xxiii. 
 
294 GEOLOGICAL CONTEMPORANEITY. ix 
 
 Crustacea; making altogether five for the great 
 sub-kingdom of Annulosa. Among Vertebrates 
 there is no ordinally distinct fossil fish: there is 
 only one extinct order of Amphibia — the Labyrin- 
 thodonts; but there are at least four distinct or- 
 ders of Eeptilia, viz., the Ichthyosauria, Plesiosau- 
 ria, Pterosauria, Dinosauria, and perhaps another 
 or two. There is no known extinct order of Birds, 
 and no certainly known extinct order of Mammals, 
 the ordinal distinctness of the " Toxodontia " be- 
 ing doubtful. 
 
 The objection that broad statements of this 
 kind, after all, rest largely on negative evidence is 
 obvious, but it has less force than may at first be 
 svipposed; for, as might be expected from the cir- 
 cumstances of the case, we possess more abundant 
 positive evidence regarding Fishes and marine Mol- 
 lusks than respecting any other forms of animal 
 life; and yet these offer us, through the whole 
 range of geological time, no species ordinally dis- 
 tinct from those now living; while the far less 
 numerous class of Echinoderms presents three, and 
 the Crustacea two, such orders, though none of 
 these come down later than the Palaeozoic age. 
 Lastly, the Eeptilia present the extraordinary and 
 exceptional phenomenon of as many extinct as ex- 
 isting orders, if not more; the four mentioned 
 maintaining their existence from the Lias to the 
 Chalk inclusive. 
 
 Some years ago one of your Secretaries pointed 
 
IX GEOLOGICAL CONTEMPOBANEITY. 295 
 
 out another kind of positive palasontological evi- 
 dence tending towards the same conclusion — af- 
 forded hy the existence of what he termed "per- 
 sistent types " of vegetable and of animal life.* 
 He stated, on the authority of Dr. Hooker, that 
 there are Carboniferous plants which appear to be 
 generically identical with some now living; that 
 the cone of the Oolitic Araucaria is hardly dis- 
 tinguishable from that of an existing species; that 
 a true Pinus appears in the Purbecke and a Jug- 
 lans in the Chalk; while, from the Bagshot Sands, 
 a Banksia, the wood of which is not distinguish- 
 able from that of species now living in Australia, 
 had been obtained. 
 
 Turning to the animal kingdom, he affirmed 
 the tabulate corals of the Silurian rocks to be 
 wonderfully like those which now exist; while 
 even the families of the Aporosa were all repre- 
 sented in the older Mesozoic rocks. 
 
 Among the MoUusca similar facts were ad- 
 duced. Let it be borne in mind that Avicula, My- 
 tilus, Chiton, Natica, Patella, Trochus, Discina, 
 Orbicula, Lingula, Bhynchonella, and Nautilus, all 
 of which are existing genera, are given without a 
 doubt as Silurian in the last edition of " Siluria "; 
 while the highest forms of the highest Cephalo- 
 pods are represented in the Lias by a genus Belem- 
 
 * See the abstract of a Lecture " On the Persistent 
 Types of Animal Life," in the Notices of the Meetings of 
 the Royal Institution of Great Britain. — June 3, 1859, 
 Vol. iii. p. 151. 
 
296 GEOLOGICAL CONTEMPORANEITY. ix 
 
 noteuthis, which presents the closest relation to the 
 existing Loligo. 
 
 The two highest groups of the Anmilosa, the 
 Insecta and the Arachnida, are represented in the 
 Coal, either by existing genera, or by forms differ- 
 ing from existing genera in quite minor peculiari- 
 ties. 
 
 Turning to the Vertebrata, the only palseozbic 
 Elasmobranch Fish of which we have any complete 
 knowledge is the Devonian and Carboniferous 
 Pleur acanthus, which differs no more from exist- 
 ing Sharks than these do from one another. 
 
 Again, vast as is the number of undoubtedly 
 Ganoid fossil Fishes, and great as is their range in 
 time, a large mass of evidence has recently been 
 adduqed to show that almost all those respecting 
 which we possess sufficient information, are re- 
 ferable to the same sub-ordinal groups as the ex- 
 isting Lepidosteus, Polypterus, and Sturgeon; and 
 that a singular relation obtains between the older 
 and the younger Fishes; the former, the Devo- 
 nian Ganoids, being almost all members of the 
 same sub-order as Polypterus, while the Meso- 
 zoic Ganoids are almost all similarly allied to 
 Lepidosteus.* 
 
 Again, what can be more remarkable than the 
 
 singular constancy of structure preserved through- 
 
 * " Memoirs of the Geological Survey of the United 
 Kingdom. — Decade x. Preliminary Essay upon the Sys- 
 tematic Arrangement of the Fishes of the Devonian 
 Epoch." 
 
IX GEOLOGICAL CONTEMPOEANEITY. 297 
 
 out a vast period of time by the family of the 
 Pycnodonts and by that of the true Coelacanths; 
 the former persisting, with but insignificant modi- 
 fications, from the Carboniferous to the Tertiary 
 rocks, inclusive; the latter existing, with still less 
 change, from the Carboniferous rocks to the Chalk, 
 inclusive? 
 
 Among Reptiles, the highest living group, that 
 of the Crocodilia, is represented, at the early part 
 of the Mesozoic epoch, by species identical in the 
 essential characters of their organisation with 
 those now living, and differing from the latter 
 only in such matters as the form of the articular 
 facets of the vertebral centra, in the extent to 
 which the nasal passages are separated from the 
 cavity of the mouth by bone, and in the propor- 
 tions of the limbs. 
 
 And even as regards the Mammalia, the scanty 
 remains of Triassic and Oolitic species afford no 
 foundation for the supposition that the organisa- 
 tion of the oldest forms differed nearly so much 
 from some of those which now live as these differ 
 from one another. 
 
 It is needless to multiply these instances; 
 enough has been said to justify the statement that, 
 in view of the immense diversity of known animal 
 and vegetable forms, and the enormous lapse of 
 time indicated by the accumulation of fossiliferous 
 strata, the only circumstance to be wondered at is, 
 not that the changes of life, as exhibited by posi- 
 
298 GEOLOGICAL CONTEMPORANEITY. ix 
 
 tive evidence, have been so great, but that they 
 have been so small. 
 
 Be they great or small, however, it is desirable 
 to attempt to estimate them. Let ns, therefore, 
 take each great division of the animal world in 
 succession, and, whenever an order or a family can 
 be shown to have had a prolonged existence, let us 
 endeavour to ascertain how far the later members 
 of the group differ from the earlier ones. If these 
 later members, in all or in many cases, exhibit a 
 certain amount of modification, the fact is, so far, 
 evidence in favour of a general law of change; and, 
 in a rough way, the rapidity of that change will be 
 measured by the demonstrable amount of modifi- 
 cation. On the other hand, it must be recollected 
 that the absence of any modification, while it may 
 leave the doctrine of the existence of a law of 
 change without positive support, cannot possibly 
 disprove all forms of that doctrine, though it may 
 afford a suiScient refutation of many of them. 
 
 The Peotozoa. — The Protozoa are represented 
 throughout the whole range of geological series, 
 from the Lower Silurian formation to the present 
 day. The most ancient forms recently made 
 known by Ehrenberg are exceedingly like those 
 which now exist: no one has ever pretended that 
 the difference between any ancient and any modern 
 Foraminifera is of more than generic value, nor 
 are the oldest Foraminifera either simpler, more 
 
IX GEOLOGICAL CONTEMPORANEITT. 299 
 
 embryonic, or less difEerentiated, than the existing 
 forms. 
 
 The CcELENTEEATA. — The Tabulate Corals 
 have existed from the Silurian epoch to the present 
 day, but I am not aware that the ancient Heliolites 
 possesses a single mark of a more embryonic or 
 less difEerentiated character, or less high organisa- 
 tion, than the existing Heliopora. As for the Apo- 
 rose Corals, in what respect is the Silurian Palceo- 
 cyclus less highly organised or more embryonic 
 than the modern Fungia, or the Liassic Aporosa 
 than the existing members of the same families? 
 
 The Mollusca. — In what sense is the living 
 Waldheimia less embryonic, or more specialised, 
 than the palteozoie Spirifer; or the existing Bhyn- 
 chonelloe, Cranice, Discince, Lingulce, than the 
 Silurian species of the same genera? In what 
 sense can Loligo or Spirula be said to be more spe- 
 cialised, or less embryonic, than Belemnites; or the 
 modern species of Lamellibranch and Gasteropod 
 genera, than the Silurian species of the same 
 genera? 
 
 The Anntjlosa. — The Carboniferous Insecta 
 and Arachnida are neither less specialised, nor 
 more embryonic, than those that now live, nor are 
 the Liassic Cirripedia and Macrura; while several 
 of the Brachyura, which appear in the Chalk, be- 
 long to existing genera; and none exhibit either 
 an intermediate, or an embryonic, character. 
 
 The Vebtebbata. — Among fishes I have re- 
 
300 GEOLOGICAL CONTEMPOEANEITT. ix 
 
 ferred to the Ccelacanthini (comprising the genera 
 Ccelacanthus, Holophagus, Undina, and Macro- 
 poma) as affording an example of a persistent type; 
 and it is most remarkable to note the smallness 
 of the differences between any of these fishes (af- 
 fecting at most the proportions of the body and 
 fins, and the character and sculpture of the scales), 
 notwithstanding their enormous range in time. 
 In all the essentials of its very peculiar structure, 
 the Macropoma of the Chalk is identical with the 
 Coelacanthus of the Coal Look at the genus 
 Lepidotus, again, persisting without a modification 
 of importance from the Liassic to the Eocene for- 
 mations inclusively. 
 
 Or among the Teleostei — in what lespect is the 
 Beryx of the Chalk more embryonic, or less diifer- 
 entiated, than Beryx lineatus of King George's 
 Sound? 
 
 Or to turn to the higher Vertebrata — in what 
 sense are the Liassic Chelonia inferior to those 
 which now exist? How are the Cretaceous Ich- 
 thyosauria, Plesiosauria, or Pterosauria less em- 
 bryonic, or more differentiated, species than those 
 of the Lias? 
 
 Or lastly, in what circumstance is the Phasco- 
 lotherium more embryonic, or of a more genera- 
 lised type, than the modern Opossum; or a Lophio- 
 don, or a Palceotherium, than a modern Tapirus or 
 Hyrax ? 
 
 These examples might be almost indefinitely 
 
IX GEOLOGICAL CONTEMPORANEITY, 301 
 
 multiplied, but surely they are sufficient to prove 
 that the only safe and unquestionable testimony 
 we can procure — positive evidence — fails to dem- 
 onstrate any sort of progressive modification to- 
 wards a less embryonic, or less generalised, type 
 in a great many groups of animals of long-contin- 
 ued geological existence. In these groups there is 
 abundant evidence of variation — none of what is 
 ordinarily understood as progression; and, if the 
 known geological record is to be regarded as even 
 any considerable fragment of the whole, it is incon- 
 ceivable that any theory of a necessarily progres- 
 sive development can stand, for the numerous or- 
 ders and families cited afford no trace of such a 
 process. 
 
 But it is a most remarkable fact, that, while the 
 groups which have been mentioned, and many be- 
 sides, exhibit no sign of progressive modification, 
 there are others, co-existing with them, under the 
 same conditions, in which more or less distinct 
 indications of such a process seem to be traceable. 
 Among such indications I may remind you of the 
 predominance of Holostome Gasteropoda in the 
 older rocks as compared with that of Siphonostone 
 Gasteropoda in the later. A case less open to the 
 objection of negative evidence, however, is that 
 afforded by the Tetrabranchiate Cephalopoda, the 
 forms of the shells and of the septal sutures ex- 
 hibiting a certain increase of complexity in the 
 newer genera. Here, however, one is met at once 
 
302 GEOLOGICAL CONTEMPORANEITY. ix 
 
 with the occurrence of Orthoceras and Baculites at 
 the two ends of the series, and of the fact that one 
 of the simplest genera, Nautilus, is that which 
 now exists. 
 
 The Crinoidea, in the abundance of stalked 
 forms in the ancient formations as compared with 
 their present rarity, seem to present us with a fair 
 case of modification from a more embryonic to- 
 wards a less embryonic condition. But then, on 
 careful consideration of the facts, the objection 
 arises that the stalk, calyx, and arms of the palae- 
 ozoic Crinoid are exceedingly different from the 
 corresponding organs of a larval Comatula; and it 
 might with perfect justice be argued that Adino- 
 crinus and Eucalyptocrinus, for example, depart to 
 the full as widely, in one direction, from the 
 stalked embryo of Comatula, as Comatula itself 
 does in the other. 
 
 The Eehinidea, again, are frequently quoted as 
 exhibiting a gradual passage from a more genera- 
 lised to a more specialised type, seeing that the 
 elongated, or oval, Spatangoids appear after the 
 spheroidal Echinoids. But here it might be ar- 
 gued, on the other hand, that the spheroidal Echin- 
 oids, in reality, depart further from the general 
 plan and from the embryonic form than the elon- 
 gated Spatangoids do; and that the peculiar dental 
 apparatus and the pedicellariee of the former are 
 marks of at least as great differentiation as the 
 petaloid ambulacra and semitte of the latter. 
 
IX GEOLOGICAL CONTEMPORANEITY. 303 
 
 Once more, the prevalence of Macrurous before 
 Brachyurous Podophthalmia is, apparently, a fair 
 piece of evidence in favour of progressive modifi- 
 cation in the same order of Crustacea; and yet the 
 case will not stand much sifting, seeing that the 
 Macrurous Podophthalmia depart as far in one 
 direction from the common type of Podophthal- 
 mia, or from any embryonic condition of the Bra- 
 chyura, as the Brachyura do in the other; and 
 that the middle terms between Macrura and Bra- 
 chyura — the Anomura — are little better repre- 
 sented in the older Mesozoic rocks than the Bra- 
 chyura are. 
 
 None of the cases of progressive modification 
 which are cited from among the Invertebrata ap- 
 pears to me to have a foundation less open to criti- 
 cism than these; and if this be so, no careful reas- 
 oner would, I think, be inclined to lay very great 
 stress upon them. Among the Vertebrata, how- 
 ever, there are a few examples which appear to be 
 far less open to objection. 
 
 It is, in fact, true of several groups of Verte- 
 brata which have lived through a considerable 
 range of time, that the endoskeleton (more par- 
 ticularly the spinal column) of the older genera 
 presents a less ossiiied, and, so far, less differenti- 
 ated, condition than that of the younger genera. 
 Thus the Devonian Ganoids, though almost all 
 members of the same sub-order as Polypterus, and 
 presenting numerous important resemblances to 
 
30i GEOLOGICAL CONTEMPORANEITY. ix 
 
 the existing genus, which possesses biconcave ver- 
 tebras, are, for the most part, wholly devoid of 
 ossified vertebral centra. The Mesozoic Lepido- 
 steidae, again, have, at most, biconcave vertebrae, 
 while the existing Lepidosteus has Salamandroid, 
 opisthoccelous, vertebree. So, none of the Palae- 
 ozoic Sharks have shown themselves to be pos- 
 sessed of ossified vertebrae, while the majority of 
 modern Sharks possess such vertebrse. Again, the 
 more ancient Crocodilia and Lacertilia have verte- 
 brae with the articular facets of their centra flat- 
 tened or biconcave, while the modern members of 
 the same group have them proccelous. But the 
 most remarkable examples of progressive modifica- 
 tion of the vertebral column, in correspondence 
 with geological age, are those afforded by the 
 Pycnodonts among fish, and the Labyrinthodonts 
 among Amphibia. 
 
 The late able ichthyologist Heckel pointed out 
 the fact, that, while the Pycnodonts never possess 
 true vertebral centra, they differ in the degree of 
 expansion and extension of the ends of the bony 
 arches of the vertebrae upon the sheath of the 
 notochord; the Carboniferous forms exhibiting 
 hardly any expansion, while the Mesozoic genera 
 present a greater and greater development, until, 
 in the Tertiary forms, the expanded ends become 
 suturally united so as to form a sort of false verte- 
 bra. Hermann von Meyer, again, to whose lumi- 
 nous researches we are indebted for our present 
 
IX GEOLOGICAL CONTEMPORANEITY. 305 
 
 large knowledge of the organisation of the older 
 Labyrinthodonts, has proved that the Carbonifer- 
 ous Archegosaurus had very imperfectly developed 
 vertebral centra, while the Triassic Mastodon- 
 saurus had the same parts completely ossified.* 
 
 The regularity and evenness of the dentition of 
 the Anoplofherium, as contrasted with that of exist- 
 ing Artiodactyles, and the assumed nearer ap- 
 proach of the dentition of certain ancient Carni- 
 vores to the typical arrangement, have also been 
 cited as exemplifications of a law of progressive de- 
 velopment, but I know of no other cases based on 
 positive evidence which are worthy of particular 
 notice. 
 
 What, then, does an impartial survey of the 
 positively ascertained truths of palaeontology 
 testify in relation to the common doctrines of pro- 
 gressive modification, which suppose that modifi- 
 cation to have taken place by a necessary progress 
 from more to less embryonic forms, or from more 
 to less generalised types, within the limits of the 
 period represented by the fossiliferous rocks? 
 
 It negatives those doctrines; for it either shows 
 us no evidence of any such modification, or demon- 
 strates it to have been very slight; and as to the 
 nature of that modification, it yields no evidence 
 whatsoever that the earlier members of any long- 
 
 * As this Address is passing through the press (March 
 7, 1862), evidence lies before me of the existence of a new 
 Labyrinthodont (Pholidogaster) , from the Edinburgh 
 coal-field with well-ossified vertebral centra. 
 206 
 
306 GEOLOGICAL CONTEMPORANEITY. ix 
 
 continued group were more generalised in struc- 
 ture than the later ones. To a certain extent, in- 
 deed, it may be said that imperfect ossification of 
 the vertebral column is an embryonic character; 
 but, on the other hand, it would be extremely in- 
 correct to suppose that the vertebral columns of 
 the older Vertebrata are in any sense embryonic in 
 their whole structure. 
 
 Obviously, if the earliest fossiliferous rocks 
 now known are coeval with the commencement of 
 life, and if their contents give us any just concep- 
 tion of the nature and the extent of the earliest 
 fauna and flora, the insignificant amount of modi- 
 fication which can be demonstrated to have taken 
 place in any one group of animals, or plants, is 
 quite incompatible with the hypothesis that all liv- 
 ing forms are the results of a necessary process of 
 progressive development, entirely comprised with- 
 in the time represented by the fossiliferous rocks. 
 
 Contrariwise, any admissible hypothesis of pro- 
 gressive modification must be compatible with per- 
 sistence without progression, through indefinite 
 periods. And should an hypothesis eventually be 
 proved to be true, in the only way in which it can 
 be demonstrated, viz., by observation and experi- 
 ment upon the existing forms of life, the conclu- 
 sion will inevitably present itself, that the Palaeo- 
 zoic, Mesozoic, and Cainozoic faunae and florsa, 
 taken together, bear somewhat the same propor- 
 tion to the whole series of living beings which 
 
IX GEOLOGICAL CONTEMPORANEITY. 307 
 
 have occupied this globe, as the existing fauna and 
 flora do to them. 
 
 Such are the results of palsontology as they 
 appear, and haye for some years appeared, to 
 the mind of an inquirer who regards that study 
 simply as one of the applications of the great bio- 
 logical sciences, and who desires to see it placed 
 upon the same sound basis as other branches of 
 physical inquiry. If the arguments which have 
 been brought forward are valid, probably no one, in 
 view of the present state of opinion, will be in- 
 clined to think the time wasted which has been 
 spent upon their elaboration. 
 
X. 
 
 GEOLOGICAL EEFORM. 
 
 [1869.] 
 
 "A great reform in geological speculation seems now 
 to have become necessary." 
 
 " It is quite certain that a great mistake has been 
 made — that British popular geology at the present time 
 is in direct opposition to the principles of Natural Phi- 
 losophy." * 
 
 In reviewing the course of geological thought 
 during the past year, for the purpose of discover- 
 ing those matters to which I might most fitly di- 
 rect your attention in the Address which it now 
 becomes my duty to deliver from the Presidential 
 Chair, the two somewhat alarming sentences which 
 I have just read, and which occur in an able and 
 interesting essay by an eminent natural philoso- 
 pher, rose into such prominence before my mind 
 that they eclipsed everything else. 
 
 It surely is a matter of paramount importance 
 for the British geologists (some of them very popu- 
 
 *0n Geological Time. By Sir W. Thomson, LL.D. 
 Transactions of the Geological Society of Glasgow, vol. iii. 
 308 
 
X GEOLOGICAL REFORM. 309 
 
 lar geologists too) here in solemn annual session 
 assembled, to inquiry whether the severe judgment 
 thus passed upon them by so high an authority as 
 Sir William Thomson is one to which they must 
 plead guilty sans phrase, or whether they are pre- 
 pared to say " not guilty," and appeal for a reversal 
 of the sentence to that higher court of educated 
 scientific opinion to which we are all amenable. 
 
 As your attorney-general for the time being, 
 I thought I could not do better than get up the 
 case with a view of advising you. It is true that 
 the charges brought forward by the other side in- 
 volve the consideration of matters quite foreign 
 to the pursuits with which I am ordinarily occu- 
 pied; but, in that respect, I am only in the posi- 
 tion which is, nine times out of ten, occupied by 
 counsel, who nevertheless contrive to gain their 
 causes, mainly by force of mother-wit and com- 
 mon-sense, aided by some training in other intel- 
 lectual exercises. 
 
 Nerved by such precedents, I proceed to put 
 my pleading before you. 
 
 And the first question with which I propose to 
 deal is, What is it to which Sir W. Thomson refers 
 when he speaks of " geological speculation " and 
 "British popular geology"? 
 
 I find three, more or less contradictory, sys- 
 tems of geological thought, each of which might 
 fairly enough claim these appellations, standing 
 side by side in Britain. I shall call one of them 
 
310 GEOLOGICAL REFORM. x 
 
 Catasteophism, another Unifobmitakianism, 
 the third Evolutionism; and I shall try briefly to 
 sketch the characters of each, that you may say 
 whether the classification is, or is: not, exhaustive. 
 
 By Catasteophism, I mean any form of geo- 
 logical speculation which, in order to account for 
 the phenomena of geology, supposes the operation 
 of forces different in their nature, or immeasur- 
 ably different in power, from those which we at 
 present see in action in the universe. 
 
 The Mosaic cosmogony is, in this sense, cata- 
 strophic, because it assumes the operation of extra- 
 natural power. The doctrine of violent upheavals, 
 debacles, and cataclysms in general, is catastrophic, 
 so far as it assumes that these were brought about 
 by causes which have now no parallel. There was 
 a time when catastrophism might, pre-eminently, 
 have claimed the title of " British popular ge- 
 ology "; and assuredly it has yet many adherents, 
 and reckons among its supporters some of the most 
 honoured members of this Society. 
 
 By Unifoemitaeianism, I mean especially, 
 the teaching of Hutton and of Lyell. 
 
 That great though incomplete work, " The 
 Theory of the Earth," seems to me to be one of 
 the most remarkable contributions to geology 
 which is recorded in the annals of the science. So 
 far as the not-living world is concerned, uniformi- 
 tarianism lies there, not only in germ, but in blos- 
 som and fruit. 
 
X GEOLOGICAL REFORM. 311 
 
 If one asks how it is that Hutton was led to 
 entertain views so far in advance of those prevalent 
 in his time, in some respects; while, in others, 
 they seem almost cnriously limited, the answer ap- 
 pears to me to be plain. 
 
 Hutton was in advance of the geological specu- 
 lation of his time, because, in the first place, he 
 had amassed a vast store of knowledge of the 
 facts of geology, gathered by personal observation 
 in travels of considerable extent; and because, in 
 the second place, he was thoroughly trained in the 
 physical and chemical science of his day, and 
 thus possessed, as much as any one in his time 
 could possess it, the knowledge which is requisite 
 for the just interpretation of geological phenom- 
 ena, and the habit of thought which fits a man 
 for scientific inquiry. 
 
 It is to this thorough scientific training that I 
 ascribe Button's steady and persistent refusal to 
 look to other causes than those now in operation 
 for the explanation of geological phenomena. 
 
 Thus he writes: — "I do not pretend, as he 
 [M. de Luc] does in his theory, to describe the 
 beginning of things. I take things such as I find 
 them at present; and from these I reason with 
 regard to that which must have been." * 
 
 And again: — " A theory of the earth, which 
 has for object truth, can have no retrospect to 
 that which had preceded the present order of the 
 * The Theory of the Earth, vol. i. p. 173, note. 
 
312 GEOLOGICAL EEPORM. x 
 
 world; for this order alone is what we have to 
 reason upon; and to reason without data is noth- 
 ing but delusion. A theory, therefore, which is 
 limited to the actual constitution of this earth can- 
 not be allowed to proceed one step beyond the 
 present order of things." * 
 
 And so clear is he, that no causes beside such 
 as are now in operation are needed to account for 
 the character and disposition of the components of 
 the crust of the earth, that he says, broadly and 
 boldly: — " . . . There is no part of the earth 
 which has not had the same origin, so far as this 
 consists in that earth being collected at the bottom 
 of the sea, and afterwards produced, as land, 
 along with masses of melted substances, by the 
 operation of mineral causes." f 
 
 But other influences were at work upon Hut- 
 ton beside those of a mind logical by nature, and 
 scientific by sound training; and the peculiar turn 
 which his speculations took seems to me to be un- 
 intelligible, unless these be taken into account. 
 The arguments of the French astronomers and 
 mathematicians, which, at the end of the last cen- 
 tury, were held to demonstrate the existence of a 
 compensating arrangement among the celestial 
 bodies, whereby all perturbations eventually re- 
 duced themselves to oscillations on each side of a 
 mean position, and the stability of the solar system 
 
 • TUe Theory of the Earth, vol. i. p. 281. 
 t Ibid. p. 371. 
 
X GEOLOGICAL EEPORM. 313 
 
 was secured, had evidently taken strong hold of 
 Hutton's mind. 
 
 In those oddly constructed periods which seem 
 to have prejudiced many persons against reading 
 his works, but which are full of that peculiar, if 
 unattractive, eloquence which flows from mastery 
 of the subject, Hutton says: — 
 
 " "We have now got to the end of our reasoning; 
 we have no data further to conclude immediately 
 from that which actually is. But we have got 
 enough; we have the satisfaction to find, that in 
 N"ature there is wisdom, system, and consistency. 
 For having, in the natural history of this earth, 
 seen a succession of worlds, we may from this con- 
 clude that there is a system in Nature; in like 
 manner as, from seeing revolutions of the planets, 
 it is concluded, that there is a system by which 
 they are intended to continue those revolutions. 
 But if the succession of worlds is established in 
 the system of nature, it is in vain to look for any- 
 thing higher in the origin of the earth. The re- 
 sult, therefore, of this physical inquiry is, that 
 we find no vestige of a beginning, — no prospect 
 of an end." * 
 
 Yet another influence worked strongly upon 
 Hutton. Like most philosophers of his age, he 
 coquetted with those final causes which have been 
 named barren virgins, but which might be more 
 fitly termed the lietairce of philosophy, so con- 
 * The Theory of the Earth, vol. i. p. 200. 
 
314 GEOLOGICAL EEPORM. x 
 
 stantly have they led men astray. The final cause 
 of the existence of the world is, for Hutton, the 
 production of life and intelligence. 
 
 " We have now considered the globe of this 
 earth as a machine, constructed upon chemical 
 as well as mechanical principles, by which its dif- 
 ferent parts are all adapted, in form, in quality, 
 and in quantity, to a certain endj an end attained 
 with certainty of success; and an end from which 
 we may perceive wisdom, in contemplating the 
 means employed. 
 
 " But is this world to he considered thus merely 
 as a machine, to last no longer than its parts retain 
 their present position, their proper forms and 
 qualities? Or may it not be also considered as an 
 organised body? such as has a constitution in 
 which the necessary decay of the machine is natu- 
 rally repaired, in the exertion of those productive 
 powers by which it had been formed. 
 
 " This is the view in which we are now to ex- 
 amine the globe; to see if there be in the constitu- 
 tion of this world a reproductive operation, by 
 which a ruined constitution may be again repaired, 
 and a duration or stability thus procured to the 
 machine, considered as a world sustaining plants 
 and animals." * 
 
 Kirwan, and the other Philistines of the day, 
 accused Hutton of declaring that his theory im- 
 plied that the world never had a beginning, and 
 * The Theory of the Earth, vol. i. pp. 16, 17. 
 
X GBOLOaiCAL REFORM. 315 
 
 never differed in condition from its present state. 
 Nothing could be more grossly unjust, as he ex- 
 pressly guards hinaself against any such conclusion 
 in the following terms: — 
 
 " But in thus tracing back the natural opera- 
 tions which have succeeded each other, and mark 
 to us the course of time past, we come to a period 
 in which we cannot see any farther. This, how- 
 ever, is not the beginning of the operations which 
 proceed in time and according to the wise economy 
 of this world; nor is it the establishing of that 
 which, in the course of time, had no beginning; 
 it is only the limit of our retrospective view of 
 those operations which have come to pass in time, 
 and have been conducted by supreme intelli- 
 gence." * 
 
 I have spoken of Uniformitarianism as the doc- 
 trine of Hutton and of Lyell. If I have quoted 
 the older writer rather than the newer, it is be- 
 cause his works are little known, and his claims on 
 our veneration too frequently forgotten, not be- 
 cause I desire to dim the fame of his eminent suc- 
 cessor. Few of the present generation of geolo- 
 gists have read Playf air's "Illustrations," fewer 
 still the original " Theory of the Earth "; the more 
 is the pity; but which of us has not thumbed every 
 page of the "Principles of Geology"? I think 
 that he who writes fairly the history of his own 
 progress in geological thought will not be able 
 * The Theory of the Earth, vol. i. p. 223. 
 
316 GEOLOGICAL REFORM. x 
 
 to separate his debt to Hutton from his obligations 
 to Lyell; and the history of the progress of individ- 
 ual geologists is the history of geology. 
 
 No one can doubt that the influence of uni- 
 formitarian views has been enormous, and, in the 
 main, most beneficial and favourable to the pro- 
 gress of sound geology. 
 
 Nor can it be questioned that Uniformitarian- 
 ism has even a stronger title than Catastrophism to 
 call itself the geological speculation of Britain, or, 
 if you will, British popular geology. For it is 
 eminently a British doctrine, and has even now 
 made comparatively little progress on the conti- 
 nent of Europe. Nevertheless, it seems to me to be 
 open to serious criticism upon one of its aspects. 
 
 I have shown how unjust was the insinuation 
 that Hutton denied a beginning to the world. 
 But it would not be unjust to say that he persist- 
 ently in practice, shut his eyes to the existence of 
 that prior and different state of things which, in 
 theory, he admitted; and, in this aversion to look 
 beyond the veil of stratified rocks, Lyell follows 
 him. 
 
 Hutton and Lyell alike agree in their indis- 
 position to carry their speculations a step beyond 
 the period recorded in the most ancient strata now 
 open to observation in the crust of the earth. This 
 is, for Hutton, " the point in which we cannot see 
 any further "; while Lyell tells us, — 
 
 " The astronomer may find good reasons for as- 
 
X GEOLOGICAL REFORM, 317 
 
 cribing the earth's form to the original fluidity 
 of the mass, in times long antecedent to the first 
 introduction of liYing beings into the planet; but 
 the geologist must be content to regard the earliest 
 monuments which it is his task to interpret, as be- 
 longing to a period when the crust had already 
 acquired great solidity and thickness, probably as 
 great as it now possesses, and when volcanic rocks, 
 not essentially differing from those now produced, 
 were formed from time to time, the intensity of 
 volcanic heat being neither greater nor less than 
 it is now." * 
 
 And again, " As geologists, we learn that it is 
 not only the present condition of the globe which 
 has been suited to the accommodation of myriads 
 of living creatures, but that many former states 
 also have been adapted to the organisation and 
 habits of prior races of beings. The disposition of 
 the seas, continents, and islands, and the climates, 
 have varied; the species likewise have been 
 changed; and yet they have all been so modelled, 
 on types analogous to those of existing plants and 
 animals, as to indicate, throughout, a perfect har- 
 mony of design and unity of purpose. To assume 
 that the evidence of the beginning, or end, of so 
 vast a scheme lies within the reach of our philoso- 
 phical inquiries, or even of our speculations, ap- 
 pears to be inconsistent with a just estimate of the 
 relations which subsist between the finite powers 
 * Principles of Geology, vol. ii. p. 211. 
 
318 GEOLOGICAL REFORM. x 
 
 of man and the attributes of an infinite and eter- 
 nal Being." * 
 
 The limitations implied in these passages ap- 
 pear to me to constitute the weakness and the logi- 
 cal defect of TJniformitarianism. No one will im- 
 pute blame to Hutton that, in face of the imper- 
 fect conditions, in his day, of those physical sci- 
 ences which furnish the keys to the riddles of geol- 
 ogy, he should have thought it practical wisdom to 
 limit his theory to an attempt to account for " the 
 present order of things "; but I am at a loss to 
 comprehend why, for all time, the geologist must 
 be content to regard the oldest fossiliferous rocks 
 as the ultima Thule of his science; or what there 
 is inconsistent with the relations between the finite 
 and the infinite mind, in the assumption, that we 
 may discern somewhat of the beginning, or of the 
 end, of this speck in space we call our earth. The 
 finite mind is certainly competent to trace out the 
 development of the fowl within the egg; and I 
 know not on what ground it should find more diffi- 
 culty in unravelling the complexities of the devel- 
 opment of the earth. In fact, as Kant has well re- 
 marked,! the cosmical process is really simpler 
 than the biological. 
 
 * Principles of Geology, vol. ii. p. 613. 
 
 f " Man darf ea sieh also nieht befremden lasaen, wenn 
 ich mieh unterstehe zu sagen, dass eher die Bildung aller 
 HimmelskOrper, die Ursache ihrer Bewegungen, kurz der 
 Ursprung der ganzen gegenwartigen Verfasaung dea 
 Weltbaues werden konnen eingesehen werden, ehe die 
 Erzeugung einea einzigen Krautes oder einer Kaupe aus 
 
X GEOLOGICAL RErOEM. 319 
 
 This attempt to limit, at a particular point, the 
 progress of inductive and deductive reasoning 
 from the things which are, to those which were — 
 this faithlessness to its own logic, seems to me to 
 have cost Unif ormitarianism the place, as the per- 
 manent form of geological speculation, which it 
 might otherwise have held. 
 
 It remains that I should put before you what I 
 understand to be the third phase of geological 
 speculation — namely. Evolutionism. 
 
 I shall not make what I have to say on this head 
 clear, unless I diverge, or seem to diverge, for a 
 while, from the direct path of my discourse, so far 
 as to explain what I take to be the scope of geology 
 itself. I conceive geology to be the history of the 
 earth, in precisely the same sense as biology is 
 the history of living beings; and I trust you will 
 not think that I am overpowered by the influence 
 of a dominant pursuit if I say that I trace a close 
 analogy between these two histories. 
 
 If I study a living being, under what heads 
 does the knowledge I obtain fall? I can learn its 
 structure, or what we call its Anatomt; and its 
 Developmekt, or the series of changes which it 
 passes through to acquire its complete structure. 
 Then I find that the living being has certain pow- 
 ers resulting from its own activities, and the inter- 
 action of these with the activities of other things — 
 
 mechanischen Grunden, deutlich und vollstandig kund 
 werden wird." — Kant's SdmmtUche Werke, Bd. i. p. 220. 
 
320 GEOLOGICAL REFORM. x 
 
 the knowledge of which is Physiology. Beyond 
 this the living being has a position in space and 
 time, which is its Distribution. All these form 
 the body of ascertainable facts which constitute 
 the status quo of the living creature. But these 
 facts have their causes; and the ascertainment of 
 these causes is the doctrine of Etiology. 
 
 If we consider what is knowable about the 
 earth, we shall And that such earth-knowledge — 
 if I may so translate the word geology — falls into 
 the same categories. 
 
 What is termed stratigraphical geology is 
 neither more nor less than the anatomy of the 
 earth; and the history of the succession of the for- 
 mations is the history of a succession of such an- 
 atomies, or corresponds with development, as dis- 
 tinct from generation. 
 
 The internal heat of the earth, the elevation 
 and depression of its crust, its belchings forth of 
 vapours, ashes, and lava, are its activities, in as 
 strict a sense as are warmth and the movements 
 and products of respiration the activities of an ani- 
 mal. The phenomena of the seasons, of the trade 
 winds, of the Gulf -stream, are as much the results 
 of the reaction between these inner activities and 
 outward forces, as are the budding of the leaves in 
 spring and their falling in autumn the effects of 
 the interaction between the organisation of a 
 plant and the solar light and heat. And, as the 
 study of the activities of the living being is called 
 
X GEOLOGICAL REFORM. 321 
 
 its physiology, so are these phenomena the suhject- 
 matter of an analogous telluric physiology, to 
 which we sometimes give the name of meteorology, 
 sometimes that of physical geography, sometimes 
 that of geology. Again, the earth has a place in 
 space and in time, and relations to other bodies in 
 both these respects, which constitute its distribu- 
 tion. This subject is usually left to the astrono- 
 mer; but a knowledge of its broad outlines seems 
 to me to be an essential constituent of the stock of 
 geological ideas. 
 
 All that can be ascertained concerning the 
 structure, succession of conditions, actions, and po- 
 sition in space of the earth, is the matter of fact 
 of its natural history. But, as in biology, there 
 remains the matter of reasoning from these facts to 
 their causes, which is just as much science as the 
 other, and indeed more; and this constitutes geo- 
 logical aetiology. 
 
 Having regard to this general scheme of geo- 
 logical knowledge and thought, it is obvious that 
 geological speculation may be, so to speak, ana- 
 tomical and developmental speculation, so far as it 
 relates to points of stratigraphical arrangement 
 which are out of reach of direct observation; or, it 
 may be physiological speculation so far as it relates 
 to undertermined problems relative to the activi- 
 ties of the earth; or, it may be distributional specu- 
 lation, if it deals with modifications of the earth's 
 place in space; or, finally, it will be setiological 
 207 
 
322 GEOLOGICAL EEPORM. x 
 
 speculation if it attempts to deduce the history of 
 the world, as a whole, from the known properties 
 of the matter of the earth, in the conditions in 
 which the earth has been placed. 
 
 For the purposes of the present discourse I may 
 take this last to be what is meant by "geological 
 speculation." 
 
 Now Uniformitarianism, as we have seen, tends 
 to ignore geological speculation in this sense alto- 
 gether. 
 
 The one point the catastrophists and the uni- 
 formitarians agreed upon, when this Society was 
 founded, was to ignore it. And you will find, if 
 you look back into our records, that our revered 
 fathers in geology plumed themselves a good deal 
 upon the practical sense and wisdom of this pro- 
 ceeding. As a temporary measure, I do not pre- 
 sume to challenge its wisdom; but in all organised 
 bodies temporary changes are apt to produce per- 
 manent effects; and as time has slipped by, alter- 
 ing all the conditions which may have made such 
 mortification of the scientific flesh desirable, I 
 think the effect of the stream of cold water which 
 has steadily flowed over geological speculation with- 
 in these walls has been of doubtful beneficence. 
 
 The art of geological speculation to which I am 
 now referring (geological aetiology, in short) was 
 created, as a science, by that famous philosopher 
 Immanuel Kant, when, in 1775, he wrote his 
 " General Natural History and Theory of the 
 
X GEOLOGICAL REFORM. 323 
 
 Celestial Bodies; or an attempt to account for 
 the Constitutional and the Mechanical Origin of 
 the Universe upon Newtonian principles." * 
 
 In this very remarkable but seemingly little- 
 known treatise,! Kant expounds a complete cos- 
 mogany, in the shape of a theory of the causes 
 which have led to the development of the uni- 
 verse from diffused atoms of matter endowed with 
 simple attractive and repulsive forces. 
 
 " Give me matter," says Kant, " and I will 
 build the world "; and he proceeds to deduce from 
 the simple data from which he starts, a doctrine in 
 all essential respects similar to the well-known 
 " Nebular Hypothesis " of Laplace. J He ac- 
 counts for the relation of the masses and the densi- 
 ties of the planets to their distances from the sun, 
 for the eccentricities of their orbits, for their rota- 
 tions, for their satellites, for the general agreement 
 in the direction of rotation among the celestial 
 bodies, for Saturn's ring, and for the zodiacal light. 
 He finds in each system of worlds indications that 
 the attractive force of the central mass will eventu- 
 ally destroy its organisation, by concentrating upon 
 itself the matter of the whole system; but, as the 
 
 * Grant (History of Physical Astronomy, p. 574) 
 makes but the briefest reference to Kant. 
 
 t " Allgemeine Naturgesehichte und Theorie des Him- 
 mels: Oder Versueh von der Verfassung und dem mecha- 
 nischen Ursprunge des ganzen Weltgebaudes naeh New- 
 ton'schen Grundsatzen abgehandelt." — Kant's Sdmmt- 
 liche Werlce, Bd. i. p. 207. 
 
 J Systf:me du Monde, tome ii. chap. 6. 
 
324 GEOLOGICAL KEFORM. x 
 
 result of this concentration, he argues for the de- 
 velopment of an amount of heat which will dissi- 
 pate the mass once more into a molecular chaos 
 such as that in which it began. 
 
 Kant pictures to himself the universe as once 
 an infinite expansion of formless and diffused mat- 
 ter. At one point of this he supposes a single cen- 
 tre of attraction set up; and, by strict deductions 
 from admitted dynamical principles, shows how 
 this must result in the development of a prodigious 
 central body, surrounded by systems of solar and 
 planetary worlds in all stages of development. In 
 vivid language he depicts the great world-mael- 
 strom, widening the margins of its prodigious eddy 
 in the slow progress of millions of ages, gradually 
 reclaiming more and more of the molecular waste, 
 and converting chaos into cosmos. But what is 
 gained at the margin is lost in the centre; the at- 
 tractions of the central systems bring their constit- 
 uents together, which then, by the heat evolved, 
 are converted once more into molecular chaos. 
 Thus the worlds that are lie between the ruins of 
 the worlds that have been, and the chaotic mate- 
 rials of the worlds that shall be; and in spite of all 
 waste and destruction. Cosmos is extending his 
 borders at the expense of Chaos. 
 
 Kant's further application of his views to the 
 earth itself is to be found in his " Treatise on 
 Physical Geography " * (a term under which the 
 * Kant's SiimmtliKhe Werke, Bd. viii. p. 145. 
 
X GEOLOGICAL REFORM. 325 
 
 then unknown science of geology was included), a 
 subject which he had studied with very great care 
 and on which he lectured for many years. The 
 fourth section of the first part of this Treatise is 
 called " History of the great Changes which the 
 Earth has formerly undergone and is still un- 
 dergoing," and is, in fact, a brief and pregnant es- 
 say upon the principles of geology. Kant gives 
 an account first " of the gradual changes which are 
 now taking place " under the heads of such as 
 are caused by earthquakes, such as are brought 
 about by rain and rivers, such as are effected by 
 the sea, such as are produced by winds and frost; 
 and, finally, such as result from the operations of 
 man. 
 
 The second part is devoted to the " Memorials 
 of the Changes which the Earth has undergone in 
 remote Antiquity." These are enumerated as: — 
 A. Proofs that the sea formerly covered' the whole 
 earth. B. Proofs that the sea has often been 
 changed into dry land and then again into sea. 
 C. A discussion of the various theories of the earth 
 put forward by Scheuchzer, Moro, Bonnet, Wood- 
 ward, White, Liebnitz, Linnaeus, and Buffon. 
 
 The third part contains an " Attempt to give a 
 sound explanation of the ancient history of the 
 earth." 
 
 I suppose that it would be very easy to pick 
 holes in the details of Kant's speculations, whether 
 cosmological, or specially telluric, in their appli- 
 
326 GEOLOGICAL REFORM. x 
 
 cation. But for all that, he seems to me to have 
 been the first person to frame a complete system 
 of geological speculation by founding the doctrine 
 of evolution. 
 
 With as much truth as Hutton, Kant could say, 
 " I take things just as I find them at present, and, 
 from these, I reason with regard to that which 
 must have been." Like Hutton, he is never tired 
 of pointing out that " in Nature there is wisdom, 
 system, and consistency." And, as in these great 
 principles, so in believing that the cosmos has a 
 reproductive operation "by which a ruined con- 
 stitution may be repaired," he forestalls Hutton; 
 while, on the other hand, Kant is true to science. 
 He knows no bounds to geological speculation but 
 those of the intellect. He reasons back to a be- 
 ginning of the present state of things; he admits 
 the possibility of an end. 
 
 I have said that the three schools of geological 
 speculation which I have termed Catastrophism, 
 Uniformitarianism, and Evolutionism, are com- 
 monly supposed to be antagonistic to one another; 
 and I presume it will have become obvious that in 
 my belief, the last is destined to swallow up the 
 other two. But it is proper to remark that each 
 of the latter has kept alive the tradition of pre- 
 cious truths. 
 
 Catasteophism has insisted upon the exist- 
 ence of a practically unlimited bank of force, on 
 which the theorist might draw; and it has cher- 
 
X GEOLOGICAL REFORM. 327 
 
 ished the idea of the development of the earth 
 from a state in which its form, and the forces 
 which it exerted, were very different from those 
 we now know. That such difference of form and 
 power once existed is a necessary part of the doc- 
 trine of evolution. 
 
 Unifoemitaeianism, on the other hand, has 
 with equal justice insisted upon a practically un- 
 limited bank of time, ready to discount any quan- 
 tity of hypothetical paper. It has kept before our 
 eyes the power of the infinitely little, time being 
 granted, and has compelled us to exhaust known 
 causes, before flying to the unknown. 
 
 To my mind there appears to be no sort of 
 necessary theoretical antagonism between Catas- 
 trophism and Uniformitarianism. On the con- 
 trary, it is very conceivable that catastrophes may 
 be part and parcel of uniformity. Let me illus- 
 trate my case by analogy. The working of a clock 
 is a model of uniform action; good time-keeping 
 means uniformity of action. But the striking of 
 the clock is essentially a catastrophe; the ham- 
 mer might be made to blow up a barrel of gun- 
 powder, or turn on a deluge of water; and, by 
 proper arrangement, the clock, instead of marking 
 the hours, might strike at all sorts of irregular 
 periods, never twice alike, in the intervals, force, 
 or number of its blows. Nevertheless, all these 
 irregular, and apparently lawless, catastrophes 
 would be the result of an absolutely uniformita- 
 
328 GEOLOGICAL REFORM. x 
 
 rian action; and we might have two schools of 
 clock-theorists, one studying the hammer and the 
 other the pendulum. 
 
 Still less is there any necessary antagonism 
 between either of these doctrines and that of Evo- 
 lution, which embraces all that is sound in both 
 Catastrophism and Uniformitarianism, while it re- 
 jects the arbitrary assumptions of the one and the, 
 as arbitrary, limitations of the other. Nor is the 
 value of the doctrine of Evolution to the philo- 
 sophic thinker diminished by the fact that it ap- 
 plies the same method to the living and the not- 
 living world; and embraces, in one stupendous an- 
 alogy, the growth of a solar system from molecular 
 chaos, the shaping of the earth from the nebu- 
 lous cubhood of its youth, through innumerable 
 changes and immeasurable ages, to its present 
 form; and the development of a living being from 
 the shapeless mass of protoplasm we term a germ. 
 
 I do not know whether Evolutionism can claim 
 that amount of currency which would entitle it to 
 be called British popular geology; but, more or 
 less vaguely, it is assuredly present in the minds 
 of most geologists. 
 
 Such being the three phases of geological specu- 
 lation, we are now in position to inquire which of 
 these it is that Sir William Thomson calls upon us 
 to reform in the passages which I have cited. 
 
 It is obviously Uniformitarianism which the 
 
X GEOLOGICAL REFORM. 329 
 
 distinguished physicist takes to be the representa- 
 tive of geological speculation in general. And 
 thus a first issue is raised, inasmuch as many per- 
 sons (and those not the least thoughtful among 
 the younger geologists) do not accept strict TJni- 
 formitarianism as the final form of geological 
 speculation. We should say, if Hutton and Play- 
 fair declare the course of the world to have heen 
 always the same, point out the fallacy by all means; 
 but, in so doing, do not imagine that you are prov- 
 ing modern geology to be in opposition to natural 
 philosophy. I do not suppose that, at the present 
 day, any geologist would be found to maintain ab- 
 solute Unif ormitarianism, to deny that the rapidity 
 of the rotation of the earth may be diminishing, 
 that the sun may be waxing dim, or that the earth 
 itself may be cooling. Most of us, I suspect, are 
 Gallios, " who care for none of these things," be- 
 ing of opinion that, true or fictitious, they have 
 made no practical difference to the earth, during 
 the period of which a record is preserved in strati- 
 fied deposits. 
 
 The accusation that we have been running 
 counter to the principles of natural philosophy, 
 therefore, is devoid of foundation. The only ques- 
 tion which can arise is whether we have, or have 
 not, been tacitly making assumptions which are 
 in opposition to certain conclusions which may 
 be drawn from those principles. And this question 
 subdivides itself into two: — the first, are we really 
 
330 GEOLOGICAL REPOEM. x 
 
 contravening such conclusions? the second, if we 
 are, are those conclusions so firmly based that we 
 may not contravene them? I reply in the nega- 
 tive to both these questions, and I will give you 
 my reasons for so doing. Sir William Thomson 
 believes that he is able to prove, by physical rea- 
 sonings, " that the existing state of things on the 
 earth, life on the earth — all geological history 
 showing continuity of life — must be limited with- 
 in some such period of time as one hundred million 
 years " {loc. cit. p. 35). 
 
 The first inquiry which arises plainly is, has it 
 ever been denied that this period may be enough 
 for the purposes of geology? 
 
 The discussion of this question is greatly em- 
 barrassed by the vagueness with which the assumed 
 limit is, I will not say defined, but indicated, — 
 " some such period of past time as one hundred 
 million years." E"ow does this mean that it miay 
 have been two, or three, or four hundred million 
 years? Because this really makes all the differ- 
 ence.* 
 
 I presume that 100,000 feet may be taken as a 
 
 full allowance for the total thickness of stratified 
 
 rocks containing traces of life; 100,000 divided by 
 
 100,000,000 = 0.001. Consequently, the deposit 
 
 of 100,000 feet of stratified rock in 100,000,000 
 
 * Sir William Thomson implies {loc. cit. p. 16) that 
 the precise time is of no consequence : " the principle is 
 the same"; but, as the principle is admitted, the whole 
 discussion turns on its practical results. 
 
X GEOLOGICAL REFORM. 331 
 
 years means that the deposit has taken place at 
 the rate of ^o^^oth of a foot, or, say, -^d of an 
 inch, per annum. 
 
 Well, I do not know that any one is prepared 
 to maintain that, even making all needful allow- 
 ances, the stratified rocks may not have been 
 formed, on an average, at the rate of -^d of an 
 inch per annum. I suppose that if such could be 
 shown to be the limit of world-growth, we could 
 put up with the allowance without feeling that 
 our speculations had undergone any revolution. 
 And perhaps, after all, the qualifying phrase 
 " some such period " may not necessitate the as- 
 sumption of more than y^-g-th or ig-j-g-th or g-Jj-d of 
 an inch of deposit per year, which, of course, 
 would give us still more ease and comfort. 
 
 But, it may be said, that it is biology, and not 
 geology, which asks for so much time — that the 
 succession of life demands vast intervals; but this 
 appears to me to be reasoning in a circle. Biology 
 takes her time from geology. The only reason we 
 have for believing in the slow rate of the change 
 in living forms is the fact that they persist through 
 a series of deposits which, geology informs us, have 
 taken a long while to make. If the geological 
 clock is wrong, all the naturalist will have to 
 do is to modify his notions of the rapidity of 
 change accordingly. And I venture to point out 
 that, when we are told that the limitation of the 
 period during which living beings have inhabited 
 
332 GEOLOGICAL REPOEM. x 
 
 this planet to one, two, or three hundred million 
 years requires a complete revolution in geological 
 speculation, the onus protandi rests on the maker 
 of the assertion, who brings forward not a shadow 
 of evidence in its support. 
 
 Thus, if we accept the limitation of time placed 
 before us by Sir W. Thomson, it is not obvious, 
 on the face of the matter, that we shall have to 
 alter, or reform, our ways in any appreciable de- 
 gree; and we may therefore proceed with much 
 calmness, and indeed much indifference, as to the 
 result, to inquire whether that limitation is justi- 
 fied by the arguments employed in its support. 
 
 These arguments are three in number: — 
 
 1. The first is based upon the undoubted fact 
 that the tides tend to retard the rate of the earth's 
 rotation upon its axis. That this must be so is 
 obvious, if one considers, roughly, that the tides 
 result from the pull which the sun and the moon 
 exert upon the sea, causing it to act as a sort of 
 break upon the rotating solid earth. 
 
 Kant, who was by no means a mere " abstract 
 philosopher," but a good mathematician and well 
 versed in the physical science of his time, not 
 only proved this in an essay of exquisite clearness 
 and intelligibility, now more than a century old,* 
 
 * " Untersuchung der Frage ob die Erde in ihrer Um- 
 drehung um die Achse, wodurch sie die Abweehselung 
 des Tages und der Nacht hervorbringt, einige Veriinde- 
 rung seit den ersten Zeiten ihres Ursprunges erlitten 
 habe, &c."— Kant's Hdmmtliclie Werke, I3d. i. p. 178. 
 
X GEOLOGICAL REFOftM. 333 
 
 but deduced from it some of its more important 
 consequences, such as the constant turning of one 
 face of the moon towards the earth. 
 
 But there is a long step from the demonstration 
 of a tendency to the estimation of the practical 
 value of that tendency, which is all with which we 
 are at present concerned. The facts bearing on 
 this point appear to stand as follows: — 
 
 It is a matter of observation that the moon's 
 mean motion is (and has for the last 3,000 years 
 been) undergoing an acceleration, relatively to the 
 rotation of the earth. Of course this may result 
 from one of two causes: the moon may really 
 have been moving more swiftly in its orbit; or the 
 earth may have been rotating more slowly on its 
 axis. 
 
 Laplace believed he had accounted for this phe- 
 nomenon by the fact that the eccentricity of the 
 earth's orbit has been diminishing throughout 
 these 3,000 years. This would produce a diminu- 
 tion of the mean attraction of the sun on the 
 moon; or, in other words, an increase in the at- 
 traction of the earth on the moon; and, conse- 
 quently, an increase in the rapidity of the orbital 
 motion of the latter body. Laplace, therefore, 
 laid the responsibility of the acceleration upon the 
 moon, and if his views were correct, the tidal re- 
 tardation must either be insignificant in amount, 
 or be counteracted by some other agency. 
 
 Our great astronomer, Adams, however, ap- 
 
334: GEOLOGICAL EEFOKM. x 
 
 pears to haye found a flaw in Laplace's caleiilation, 
 and to have shown that only half the observed re- 
 tardation could be accounted for in the way he 
 had suggested. There remains, therefore, the 
 other half to be accounted for; and here, in the 
 absence of all positive knowledge, three sets of 
 hypotheses have been suggested. 
 
 (a.) M. Delaunay suggests that the earth is at 
 fault, in consequence of the tidal retardation. 
 Messrs. Adams, Thomson, and Tait work out this 
 suggestion, and, " on a certain assumption as to 
 the proportion of retardations due to the sun and 
 moon," find the earth may lose twenty-two seconds 
 of time in a century from this cause.* 
 
 (6.) But M. Dufour suggests that the retarda- 
 tion of the earth (which is hypothetieally assumed 
 to exist) may be due in part, or wholly, to the in- 
 crease of the moment of inertia of the earth by me- 
 teors falling upon its surface. This suggestion 
 also meets with the entire approval of Sir W. 
 Thomson, who shows that meteor-dust, accumulat- 
 ing at the rate of one foot in 4,000 years, would ac- 
 count for the remainder of retardation, f 
 
 (c.) Thirdly, Sir W. Thomson brings forward 
 an hypothesis of his own with respect to the cause 
 of the hypothetical retardation of the earth's ro- 
 tation: — 
 
 "Let us suppose ice to melt from the polar 
 regions (20° round each pole, we may say) to the 
 * Sir W. Thomson, loc. cit. p. 14. t IMd. p. 27. 
 
X GEOLOGICAL EEPORM. 335 
 
 extent of something more than a foot thick, enough 
 to give 1.1 foot of water over those areas, or 
 0.006 of a foot of water if spread over the whole 
 globe, which would, in reality, raise the sea-level 
 by only some such undiscoverable difference 
 as three-fourths of an inch or an inch. This, 
 or the reverse, which we believe might happen 
 any year, and could certainly not be detected 
 without far more accurate observations and cal- 
 culations for the mean sea-level than any hither- 
 to made, would slacken or quicken the earth's 
 rate as a timekeeper by one-tenth of a second per 
 year." * 
 
 I do not presume to throw the slightest doubt 
 upon the accuracy of any of the calculations made 
 by such distinguished mathematicians as those 
 who have made the suggestions I have cited. On 
 the contrary, it is necessary to my argument to as- 
 sume that they are all correct. But I desire to 
 point out that this seems to be one of the many 
 cases in which the admitted accuracy of mathe- 
 matical process is allowed to throw a wholly in- 
 admissible appearance of authority over the re- 
 sults obtained by them. Mathematics may be 
 compared to a mill of exquisite workmanship, 
 which grinds you stuff of any degree of fineness; 
 but, nevertheless, what you get out depends upon 
 what you put in; and as the grandest mill in the 
 world will not extract wheat-flour from peascod, 
 * Sir W. Thomson, loc. cit. p. 27. 
 
336 GEOLOGICAL REFORM. x 
 
 SO pages of formulas will not get a definite result 
 out of loose data. 
 
 In the present instance it appears to be ad- 
 mitted: — 
 
 1. That it is not absolutely certain, after all, 
 whether the moon's mean motion is undergoing 
 acceleration, or the earth's rotation retardation.* 
 And yet this is the key of the whole position. 
 
 2. If the rapidity of the earth's rotation is di- 
 minishing, it is not certain how much of that re- 
 tardation is due to tidal friction, how much to 
 meteors, — how much to possible excess of melting 
 over accumulation of polar ice, during the period 
 covered by observation, which amounts, at the out- 
 side, to not more than 3,600 years. 
 
 3. The efEect of a different distribution of land 
 and water in modifying the retardation caused by 
 tidal friction, and of reducing it, under some cir- 
 cumstances, to a minimum, does not appear to be 
 taken into account. 
 
 4. During the Miocene epoch the polar ice was 
 certainly many feet thinner than it has been dur- 
 ing, or since, the Glacial epoch. Sir W. Thomson 
 tells us that the accumulation of something more 
 than a foot of ice around the poles (which implies 
 the withdrawal of, say, an inch of water from the 
 general surface of the sea) will cause the earth to 
 rotate quicker by one-tenth of a second per annum. 
 
 * It will be understood that I do not wish to deny 
 that the earth's rotation may be und^going retardation. 
 
X GEOLOGICAL REFORM. 337 
 
 It would appear, therefore, that the earth may 
 have been rotating, throughout the whole period 
 which has elapsed from the commencement of the 
 Glacial epoch down to the present time, one, or 
 more, seconds per annum quicker than it rotated 
 during the Miocene epoch. 
 
 But, according to Sir W. Thomson's calcula- 
 tion, tidal retardation will only account for a re- 
 tardation of 33" in a century, or ^^jth (say ^th) 
 of a second per annum. 
 
 Thus, assuming that the accumulation of polar 
 ice since the Miocene epoch has only been sufficient 
 to produce ten times the effect of a coat of ice one 
 foot thick, we shall have an accelerating cause 
 which covers all the loss from tidal action, and 
 leaves a balance of -fths of a second per annum in 
 the way of acceleration. 
 
 If tidal retardation can be thus checked and 
 overthrown by other temporary conditions, what 
 becomes of the confident assertion, based upon the 
 assumed uniformity of tidal retardation, that ten 
 thousand million years ago the earth must have 
 been rotating more than twice as fast as at 
 present, and, therefore, that we geologists are 
 " in direct opposition to the principles of Natural 
 Philosophy" if we spread geological history over 
 that time? 
 
 II. The second argument is thus stated by Sir 
 W. Thomson: — "An article, by myself, published 
 in ' Macmillan's Magazine ' for March, 1863, on the 
 208 
 
338 GEOLOGICAL REFORM. x 
 
 age of the sun's heat, explains results of investiga- 
 tion into various questions as to possibilities re- 
 garding the amount of heat that the sun could 
 have, dealing with it as you would with a stone, or 
 a piece of matter, only taking into account the 
 sun's dimensions, which showed it to be possible 
 that the sun may have already illuminated the 
 earth for as many as one hundred million j^ears, but 
 at the same time rendered it almost certain that he 
 had not illuminated the earth for five hundred 
 millions of years. The estimates here are neces- 
 sarily very vague; but yet, vague as they are, I do 
 not know that it is possible, upon any reasonable 
 estimate founded on known properties of matter, 
 to say that we can believe the sun has really illumi- 
 nated the earth for five hundred million years." * 
 I do not wish to " Hansardise " Sir William 
 Thomson by laying much stress on the fact that 
 only fifteen years ago he entertained a totally differ- 
 ent view of the origin of the sun's heat, and 
 believed that the energy radiated from year to 
 year was supplied from year to year — a doctrine 
 which would have suited Hutton perfectly. But 
 the fact that so eminent a physical philosopher 
 has, thus recently, held views opposite to those 
 which he now entertains, and that he confesses his 
 own estimates to be " very vague," justly entitles 
 us to disregard those estimates, if any distinct 
 facts on our side go against them. However, I am 
 * Log. cit. p. 20. 
 
X GEOLOGICAL REFORM. 339 
 
 not aware that such facts exist. As I have already 
 said, for anything I know, one, two, or three hun- 
 dred millions of years may serve the needs of 
 geologists perfectly well. 
 
 III. The third line of argument is based upon 
 the temperature of the interior of the earth. Sir 
 W. Thomson refers to certain investigations which 
 prove that the present thermal condition of the in- 
 terior of the earth implies either a heating of the 
 earth within the last 30,000 years of as much as 
 100° F., or a greater heating all over the surface at 
 some time further back than 30,000 years, and 
 then proceeds thus: — 
 
 " Now, are geologists prepared to admit that, at 
 some time within the last 30,000 years, there has 
 been all over the earth so high a temperature as 
 that? I presume not; no geologist — no modern ge- 
 ologist — would for a moment admit the hypothe- 
 sis that the present state of underground heat 
 is due to a heating of the surface at so late a 
 period as 30,000 years ago. If that is not admitted 
 we are driven to a greater heat at some time 
 more than 30,000 years ago. A greater heating 
 all over the surface than 100° F. would kill nearly 
 all existing plants and animals, I may safely say. 
 Are modern geologists prepared to say that all life 
 was killed off the earth 50,000, 100,000, or 300,000 
 years ago? For the uniformity theory, the fur- 
 ther back the time of high surface-temperature is 
 put the better; but the further back the time of 
 
340 GEOLOGICAL REFORM. x 
 
 heating, the hotter it must have been. The best 
 for those who draw most largely on time is that 
 which puts it furthest back; and that is the theory 
 that the heating was enough to melt the whole. 
 But even if it was enough to melt the whole, 
 we must still admit some limit, such as fifty mil- 
 lion years, one hundred million years, or two or 
 three hundred million years ago. Beyond that we 
 cannot go." * 
 
 It will be observed that the "limit" is once 
 again of the vaguest, ranging from 50,000,000 
 years to 300,000,000. And the reply is, once 
 more, that, for anything that can be proved to the 
 contrary, one or two hundred million years might 
 serve the purpose, even of a thoroughgoing Hut- 
 tonian uniformitarian, very well. 
 
 But if, on the other hand, the 100,000,000 or 
 200,000,000 years appear to be insufficient for 
 geological purposes, we must closely criticise the 
 method by which the limit is reached. The 
 argument is simple enough. Assuming the earth 
 to be nothing but a cooling mass, the quantity of 
 heat lost per year, supposing the rate of cooling to 
 have been uniform, multiplied by any given num- 
 ber of years, will be given the minimum tempera- 
 ture that number of years ago. 
 
 But is the earth nothing but a cooling mass, 
 " like a hot-water jar such as is used in carriages," 
 or "a globe of sandstone," and has its cooling 
 * hoc. cit. p. 24. 
 
X GEOLOGICAL REFORM. 341 
 
 been uniform? An affirmative answer to both 
 these questions seems to be necessary to the valid- 
 ity of the calculations on which Sir W. Thomson 
 lays so much stress. 
 
 Nevertheless it surely may be urged that such 
 affirmative answers are purely hypothetical, and 
 that other suppositions have an equal right to con- 
 sideration. 
 
 For example, is it not possible that, at the pro- 
 digious temperature which would seem to exist at 
 100 miles below the surface, all the metallic bases 
 may behave as mercury does at a red heat, when it 
 refuses to combine with oxygen; while, nearer the 
 surface, and therefore at a lower temperature, they 
 may enter into combination (as mercury does with 
 oxygen a few degrees below its boiling-point), and 
 so give rise to a heat totally distinct from that 
 which they possess as cooling bodies? And has it 
 not also been proved by recent researches that the 
 quality of the atmosphere may immensely affect its 
 permeability to heat; and, consequently, pro- 
 foundly modify the rate of cooling the globe as a 
 whole? 
 
 I do not think it can be denied that such con- 
 ditions may exist, and may so greatly affect the 
 supply, and the loss, of terrestrial heat as to destroy 
 the value of any calculations which leave them 
 out of sight. 
 
 My functions as your advocate are at an end. 
 I speak with more than the sincerity of a mere 
 
34:2 GEOLOGICAL REFORM. x 
 
 advocate when I express the belief that the case 
 against us has entirely broken down. The cry for 
 reform which has been raised without, is super- 
 fluous, inasmuch as we have long been reforming 
 from within, with all needful speed. And the 
 critical examination of the grounds upon which 
 the very grave charge of opposition to the prin- 
 ciples of Natural Philosophy has been brought 
 against us, rather shows that we have exercised a 
 wise discrimination in declining, for the present, 
 to meddle with our foundations. 
 
XI. 
 
 PALEONTOLOGY AND THE DOCTEINE 
 OF EVOLUTION. 
 
 [1870.] 
 
 It is now eight years since, in the absence of 
 the late Mr. Leonard Horner, who then presided 
 over us, it fell to my lot, as one of the Secretaries 
 of this Society, to draw up the customary Annual 
 Address. I availed myself of the opportunity to 
 endeavour to " take stock " of that portion of the 
 science of biology which is commonly called 
 "paleontology," as it then existed; and, dis- 
 cussing one after another the doctrines held by 
 palaeontologists, I put before you the results of 
 my attempts to sift the well-established from 
 the hypothetical or the doubtful. Permit me 
 briefly to recall to your minds what those results 
 were: — 
 
 1. The living population of all parts of the 
 earth's surface which have yet been examined 
 has undergone a succession of changes which, 
 upon the whole, have been of a slow and gradual 
 character. 
 
 343 
 
344 PALEONTOLOGY AND EVOLUTION. xi 
 
 2. When the fossil remains which are the 
 evidences of these successive changes, as they 
 have occurred in any two more or less distant 
 parts of the surface of the earth, are com- 
 pared, they exhibit a certain broad and general 
 parallelism. In other words, certain forms of 
 life in one locality occur in the same general 
 order of succession as, or are homotaxial with, simi- 
 lar forms in the other locality. 
 
 3. Homotaxis is not to be held identical with 
 synchronism without independent evidence. It 
 is possible that similar, or even identical, faunas 
 and florffi in two different localities may be of 
 extremely different ages, if the term " age " is 
 used in its proper chronological sense. I stated 
 that " geographical provinces, or zones, may have 
 been as distinctly marked in the Palseozoic epoch 
 as at present; and those seemingly sudden appear- 
 ances of new genera and species which we ascribe 
 to new creation, may be simple results of migra- 
 tion." 
 
 4. The opinion that the oldest known fossils 
 are the earliest forms of life has no solid founda- 
 tion. 
 
 5. If we confine ourselves to positively ascer- 
 tained facts, the total amount of change in the 
 forms of animal and vegetable life, since the ex- 
 istence of such forms is recorded, is small. 
 When compared with the lapse of time since 
 the first appearance of these forms, the amount 
 
XI PALEONTOLOGY AND EVOLUTION. 345 
 
 of change is wonderfully small. Moreover, in 
 each great group of the animal and vegetable 
 kingdoms, there are certain forms which I termed 
 Peksistent Types, which have remained, with 
 but very little apparent change, from their first 
 appearance to the present time. 
 
 6. In answer to the question " What, then, does 
 an impartial survey of the positively ascertained 
 truths of palaeontology testify in relation to the 
 common doctrines of progressive modification, 
 which suppose that modification to have taken 
 place by a necessary progress from more to 
 less embryonic forms, from more to less general- 
 ised types, within the limits of the period 
 represented by the fossiliferous rocks? " I reply, 
 " It negatives these doctrines; for it either shows 
 us no evidence of such modification, or demon- 
 strates such modification as has occurred to have 
 been very slight; and, as to the nature of that 
 modification, it yields no evidence whatsoever that 
 the earlier members of any long-continued group 
 were more generalised in structure than the later 
 ones." 
 
 I think that I cannot employ my last opportu- 
 nity of addressing you, officially, more properly — 
 I may say more dutifully — than in revising these 
 old judgments with such help as further knowl- 
 edge and reflection, and an extreme desire to get 
 at the truth, may afford me. 
 
 1. With respect to the first proposition, I may 
 
3i6 PALEONTOLOGY AND EVOLUTION. xi 
 
 remark that whatever may he the ease among the 
 physical geologists, catastrophic palaeontologists 
 are practically extinct. It is now no part of 
 recognised geological doctrine that the species of 
 one formation all died out and were replaced by a 
 brand-new set in the next formation. On the 
 contrary, it is generally, if not universally, agreed 
 that the succession of life has been the result of a 
 slow and gradual replacement of species by species; 
 and that all appearances of abruptness of change 
 are due to breaks in the series of deposits, or other 
 changes in physical conditions. The continuity of 
 living forms has been unbroken from the earliest 
 times to the present day. 
 
 2, 3. The use of the word " homotaxis " instead 
 of " synchronism " has not, so far as I know, found 
 much favour in the eyes of geologists. I hope, 
 therefore, that it is a love for scientific caution, 
 and not mere personal affection for a bantling of 
 my own, which leads me still to think that the 
 change of phrase is of importance, and that the 
 sooner it is made, the sooner shall we get rid of a 
 number of pitfalls which beset the reasoner upon 
 the facts and theories of geology. 
 
 One of the latest pieces of foreign intelligence 
 which has reached us is the information that the 
 Austrian geologists have, at last, succumbed to 
 the weighty evidence which M. Barrande has 
 accumulated, and have admitted the doctrine of 
 colonies. But the admission of the doctrine of 
 
XI PALEONTOLOGY AND EVOLUTION. 3-t7 
 
 colonies implies the further admission that even 
 identity of organic remains is no proof of the 
 synchronism of the deposits which contain 
 them. 
 
 4. The discussions touching the Eozoon, which 
 commenced in 1864, have abundantly justified the 
 fourth proposition. In 1862, the oldest record of 
 life was in the Cambrian rocks; but if the Eozoon 
 be, as Principal Dawson and Dr. Carpenter have 
 shown so much reason for believing, the remains 
 of a living being, the discovery of its true nature 
 carried life back to a period which, as Sir William 
 Logan has observed, is as remote from that during 
 which the Cambrian rocks were deposited, as the 
 Cambrian epoch itself is from the tertiaries. In 
 other words, the ascertained duration of life upon 
 the globe was nearly doubled at a stroke. 
 
 5. The significance of persistent types, and of 
 the small amount of change which has taken place 
 even in those forms which can be shown to have 
 been modified, becomes greater and greater in my 
 eyes, the longer I occupy myself with the biology 
 of the past. 
 
 Consider how long a time has elapsed since the 
 Miocene epoch. Yet at that time there is reason 
 to believe that every important group in every 
 order of the Mammalia was represented. Even the 
 comparatively scanty Eocene fauna yields exam- 
 ples of the orders Cheiroptera, Insectivora, Boden- 
 tia, and Perissodadyla; of Artiodactyla under both 
 
348 PALiEONTOLOGY AND EVOLUTION. xi 
 
 the Euminant and the Porcine modifications; of 
 Carnivora, Cetacea, and Marsupialia. 
 
 Or, if we go back to the older half of the Meso- 
 zoic epoch, how truly surprising it is to find 
 every order of the Reptilia, except the OpMdia, 
 represented; while some groups, such as the 
 Ornithoscelida and the Pterosauria, more special- 
 ised than any which now exist, abounded. 
 
 There is one division of the Amphiiia which 
 offers especially important evidence upon this 
 point, inasmuch as it bridges over the gap between 
 the Mesozoie and the Palaeozoic formations (often 
 supposed to be of such prodigious magnitude), ex- 
 tending, as it does, from the bottom of the Car- 
 boniferous series to the top of the Trias, if not 
 into the Lias. I refer to the Labyrinthodonts. 
 As the Address of 1862 was passing through the 
 press, I was able to mention, in a note, the 
 discovery of a large Labyrinthodont, with well- 
 ossified vertebrEB, in the Edinburgh coal-field. 
 Since that time eight or ten distinct genera of 
 Labyrinthodonts have been discovered in the 
 Carboniferous rocks of England, Scotland, and 
 Ireland, not to mention the American forms 
 described by Principal Dawson and Professor 
 Cope. So that, at the present time, the Labyrin- 
 thodont Fauna of the Carboniferous rocks is more 
 extensive and diversified than that of the Trias, 
 while its chief types, so far as osteology enables 
 us to judge, are quite as highly organised. Thus 
 
XI PALEONTOLOGY AND EVOLUTION. 349 
 
 it is certain that a comparatively highly organised 
 vertebrate type, such as that of the Labyrintho- 
 donts, is capable of persisting, with no considerable 
 change, through the period represented by the vast 
 deposits which constitute the Carboniferous, the 
 Permian, and the Triassic formations. 
 
 The very remarkable results which have been 
 brought to light by the sounding and dredging 
 operations, which have been carried on with such 
 remarkable success by the expeditions sent out by 
 our own, the American, and the Swedish govern- 
 ments, under the supervision of able naturalists, 
 have a bearing in the same direction. These in- 
 vestigations have demonstrated the existence, at 
 great depths in the ocean, of living animals in 
 some cases identical with, in others very similar 
 to, those which are found fossilised in the white 
 chalk. The Gldbigerinw, Cyatholiths, Cocco- 
 spheres, Discoliths in the one are absolutely 
 identical with those in the other; there are 
 identical, or closely analogous, species of Sponges, 
 Echinoderms, and Brachiopods. Off the coast of 
 Portugal, there now lives a species of Beryx, which, 
 doubtless, leaves its bones and scales here and 
 there in the Atlantic ooze, as its predecessor left 
 its spoils in the mud of the sea of the Cretaceous 
 epoch. 
 
 Many years ago * I ventured to speak of the 
 
 * See an article in the Saturday Review, for 1858, on 
 " Chalk, Ancient and Modern." 
 
350 PALEONTOLOGY AND EVOLUTION. xi 
 
 Atlantic mud as "modern chalk," and I know of 
 no fact inconsistent with the view which Professor 
 Wyville Thomson has advocated, that the modern 
 chalk is not only the lineal descendant of the an- 
 cient chalk, bnt that it remains, so to speak, in 
 the possession of the ancestral estate; and that 
 from the Cretaceous period (if not much earlier) 
 to the present day, the deep sea has covered a 
 large part of what is now the area of the Atlantic. 
 But if Glohigerina, and Terebratula caput-serpentis 
 and Beryx, not to mention other forms of animals 
 and of plants, thus bridge over the interval 
 between the present and the Mesozoie periods, is 
 it possible that the majority of other living things 
 underwent a " sea-change into something new and 
 strange " all at once? 
 
 6. Thus far I have endeavoured to expand and 
 to enforce by fresh arguments, but not to modify 
 in any important resp-ect, the ideas submitted to 
 you on a former occasion. But when I come to 
 the propositions touching progressive modifica- 
 tion, it appears to me, with the help of the new 
 light which has broken from various quarters, that 
 there is much ground for softening the somewhat 
 Brutus-like severity with which, in 1862, I dealt 
 with a doctrine, for the truth of which I should 
 have been glad enough to be able to find a good 
 foundation. So far, indeed, as the Invertehrata 
 and the lower Vertelrata are concerned, the facts 
 and the conclusions which are to be drawn from 
 
XI PALEONTOLOGY AND EVOLUTION. 351 
 
 them appear to me to remain what they were. For 
 anything that, as yet, appears to the contrary, the 
 earliest known Marsupials may have been as highly 
 organised as their living congeners; the Permian 
 lizards show no signs of inferiority to those of 
 the present day; the Labyrinthodonts cannot be 
 placed below the living Salamander and Triton; 
 the Devonian Ganoids are closely related to Polyp- 
 terus and to Lepidosiren. 
 
 But when we turn to the higher Vertebrata, 
 the results of recent investigations, however we 
 may sift and criticise them, seem to me to leave a 
 clear balance in favour of the doctrine of the 
 evolution of living forms one from another. 
 Nevertheless, in discussing this question, it is 
 very necessary to discriminate carefully between 
 the diffeient kinds of evidence from fossil re- 
 mains which are brought forward in favour of 
 evolution. 
 
 Every fossil which takes an intermediate place 
 between forms of life already known, may be said, 
 so far as it is intermediate, to be evidence in favour 
 of evolution, inasmuch as it shows a possible road 
 by which evolution may have taken place. But 
 the mere discovery of such a form does not, in it- 
 self, prove that evolution took place by and through 
 it, nor does it constitute more than presumptive 
 evidence in favour of evolution in general. 
 Suppose A, B, C to be three forms, while B is 
 intermediate in structure between A and C. Then 
 
352 PALEONTOLOGY AND EVOLUTION. xi 
 
 the doctrine of evolution ofEers four possible 
 alternatives. A may have become C by way 
 of B; or C may have become A by way of B; or 
 A and C may be independent modifications of 
 B; or A, B, and C may be independent modifica- 
 tions of some unknown D. Take the ease of the 
 Pigs, the AnoplotheridcB, and the Euminants. 
 The Anoplotheridm are intermediate between the 
 first and the last; but this does not tell us whether 
 the Euminants have come from the Pigs, or the 
 Pigs from Euminants, or both from Anoplotheridce, 
 or whether Pigs, Euminants, and AnoplotheridcB 
 alike may not have diverged from some common 
 stock. 
 
 But if it can be shown that A, B, and C exhibit 
 successive stages in the degree of modification, or 
 specialisation, of the same type; and if, further, it 
 can be proved that they occur in successively 
 newer deposits, A being in the oldest and C in 
 the newest, then the intermediate character of B 
 has quite another importance, and I should accept 
 it, without hesitation, as a link in the genealogy 
 of C. I should consider the burden of proof to be 
 thrown upon any one who denied C to have been 
 derived from A by way of B, or in some closely 
 analogous fashion; for it is always probable that 
 one may not hit upon the exact line of filiation, 
 and, in dealing with fossils, may mistake uncles 
 and nephews for fathers and sons. 
 
 I think it necessary to distinguish between the 
 
XI PALEONTOLOGY AND EVOLUTION. 363 
 
 former and the latter classes of intermediate forms, 
 as intercalary types and linear types. When I ap- 
 ply the former term, I merely mean to say that 
 as a matter of fact, the form B, so named, is inter- 
 mediate between the others, in the sense in which 
 the Anoplotherium is intermediate between the 
 Pigs and the Euminants — without either affirming, 
 or denying, any direct genetic relation between 
 the three forms involved. When I apply the latter 
 term, on the other hand, I mean to express the 
 opinion that the forms A, B, and C constitute a 
 line of descent, and that B is thus part of the 
 lineage of C. 
 
 From the time when Cuvier's wonderful re- 
 searches upon the extinct Mammals of the Paris 
 gypsum first made intercalary types known, and 
 caused them to be recognised as such, the number 
 of such forms has steadily increased among the 
 higher Mammalia. Not only do we now know 
 numerous intercalary forms of Ungulata, but M. 
 Gaudry's great monograph upon the fossils of 
 Pikermi (which strikes me as one of the most per- 
 fect pieces of palseontological work I have seen 
 for a long time) shows us, among the Primates, 
 Mesopithecus as an intercalary form between the 
 Semnopitheci and the Macaci; and among the 
 Carnivora, Hycenictis and Ictitherium as intercal- 
 ary, or, perhaps, linear types between the Viverridw 
 and the Hycenidw. 
 
 Hardly any order of the higher Mammalia 
 209 
 
354 PALEONTOLOGY AND EVOLUTION. xi 
 
 stands so apparently separate and isolated from 
 the rest as that of the Cetaceaj though a careful 
 consideration of the structure of the pinnipede 
 Carnivora, or Seals, shows, in them, many an 
 approximation towards the still more completely 
 marine mammals. The extinct Zeuglodon, how- 
 ever, presents us with an intercalary form between 
 the type of the Seals and that of the Whales. 
 The skull of this great Eocene sea-monster, in 
 fact, shows by the narrow and prolonged inter- 
 orbital region; the extensive union of the parietal 
 bones in a sagittal suture; the well-developed nasal 
 bones; the distinct and large incisors implanted 
 in premaxillary bones, which take a full share in 
 bounding the fore part of the gape; the two-fanged 
 molar teeth with triangular and serrated crowns, 
 not exceeding five on each side in each jaw; and 
 the existence of a deciduous dentition — its close 
 relation with the Seals. While, on the other hand, 
 the produced rostral form of the snout, the long 
 symphysis, and the low coronary process of the 
 mandible are approximations to the cetacean form 
 of those parts. 
 
 The scapula resembles that of the cetacean 
 Hyperoodon, but the supra-spinous fossa is larger 
 and more seal-like; as is the humerus, which 
 differs from that of the Cetacea in presenting true 
 articular surfaces for the free jointing of the bones 
 of the fore-arm. In the apparently complete 
 absence of hinder limbs, and in the characters 
 
XI PALEONTOLOGY AND EVOLUTION. 355 
 
 of the vertebral column, the Zeuglodon lies on the 
 cetacean side of the boundary line; so that upon 
 the whole, the Zeuglodonts, transitional as they 
 are, are conveniently retained in the cetacean 
 order. And the publication, in 1864, of M. Van 
 Beneden's memoir on the Miocene and Pliocene 
 Squalodon, furnished much better means than 
 anatomists previously possessed of fitting in 
 another link of the chain which connects the 
 existing Cetacea with Zeuglodon. The teeth are 
 much more numerous, although the molars exhibit 
 the zeuglodont double fang; the nasal bones are 
 very short, and the upper surface of the rostrum 
 presents the groove, filled up during life by the 
 prolongation of the ethmoidal cartilage, which is 
 so characteristic of the majority of the Cetacea. 
 
 It appears to me that, just as among the 
 existing Carnivora, the walruses and the eared 
 seals are intercalary forms between the fissipede 
 Carnivora and the ordinary seals, so the Zeuglo- 
 donts are intercalary between the Carnivora, as a 
 whole, and the Cetacea. Whether the Zeuglodonts 
 are also linear types in their relation to these two 
 groups cannot be ascertained, until we have more 
 definite knowledge than we possess at present re- 
 specting the relations in time of the Carnivora and 
 Cetacea. 
 
 Thus far we have been concerned with the 
 intercalary types which occupy the intervals 
 between Families or Orders of the same class; 
 
356 PALEONTOLOGY AND EVOLUTION. xi 
 
 but the investigations which have been carried 
 on by Professor Gegenbaur, Professor Cope, and 
 myself into the structure and relations of the 
 extinct reptilian forms of the Ornithoscelida (or 
 Dinosauria and Compsognatha) have brought to 
 light the existence of intercalary forms between 
 what have hitherto been always regarded as very 
 distinct classes of the vertebrate sub-kingdom, 
 namely Reptilia and Aves. Whatever inferences 
 may, or may not, be drawn from the fact, it is 
 now an established truth that, in many of these 
 Ornithoscelida, the hind limbs and the pelvis are 
 much more similar to those of Birds than they 
 are to those of Reptiles, and that these Bird-rep- 
 tiles, or Eeptile-birds, were more or less completely 
 bipedal. 
 
 When I addressed you in 1862, I should have 
 been bold indeed had I suggested that palseon- 
 tology would before long show us the possibility 
 of a direct transition from the type of the lizard 
 to that of the ostrich. At the present moment, 
 we have, in the Ornithoscelida, the intercalary type, 
 which proves that transition to be something 
 more than a possibility; but it is very doubtful 
 whether any of the genera of Ornithoscelida with 
 which we are at present acquainted are the actual 
 linear types by which the transition from the 
 lizard to the bird was effected. These, very proba- 
 bly, are still hidden from us in the older for- 
 mations. 
 
XI PALEONTOLOGY AND EVOLUTION. 35Y 
 
 Let lis now endeavour to find some eases of 
 true linear types, or forms which are intermediate 
 between others because they stand in a direct 
 genetic relation to them. It is no easy matter to 
 find clear and unmistakable evidence of filiation 
 among fossil animals; for, in order that such evi- 
 dence should be quite satisfactory, it is necessary 
 that we should be acquainted with all the most 
 important features of the organisation of the 
 animals which are supposed to be thus related, and 
 not merely with the fragments upon which the 
 genera and species of the palaeontologist are so 
 often based. M. Gaudry has arranged the species 
 of Hymnidce, Proboscidea, Ehinocerotidw, and 
 EquidcB in their order of filiation from their earliest 
 appearance in the Miocene epoch to the present 
 time, and Professor Eiitimeyer has drawn up simi- 
 lar schemes for the Oxen and other Ungulata — 
 with what, I am disposed to think, is a fair and 
 probable approximation to the order of nature. 
 But, as no one is better aware than these two 
 learned, acute, and philosophical biologists, all such 
 arrangements must be regarded as provisional, ex- 
 cept in those cases in which, by a fortunate acci- 
 dent, large series of remains are obtainable from a 
 thick and widespread series of deposits. It is easy 
 to accumulate probabilities — hard to make out 
 some particular case in such a way that it will stand 
 rigorous criticism. 
 
 After much search, however, I think that such 
 
358 PALEONTOLOGY AND EVOLUTION. xi 
 
 a case is to be made out in faTOur of the pedigree 
 of the Horses. 
 
 The genus Equus is represented as far back as 
 the latter part of the Miocene epoch; but in de- 
 posits belonging to the middle of that epoch its 
 place is taken by two other genera, Hipparion and 
 Anchitherium; * and, in the lowest Miocene and 
 upper Eocene, only the last genus occurs. A 
 species of Anchitherium was referred by Cuvier to 
 the PalcBotheria under the name of P. aurelianense. 
 The grinding-teeth are, in fact, very similar in 
 shape and in pattern, and in the absence of any 
 thick layer of cement, to those of some species of 
 PalcBotherium, especially Cuvier's Palceotherium 
 minus, which has been formed into a separate 
 genus, Plagiolophus, by Pomel. But in the fact 
 that there are only six full-sized grinders in the 
 lower jaw, the first premolar being very small; 
 that the anterior grinders are as large as, or 
 rather larger than, the posterior ones; that the 
 second premolar has an anterior prolongation; and 
 that the posterior molar of the lower jaw has, as 
 
 * Hermann von Meyer gave the name of AneMthcHum 
 to A. Eequerrw; and in his paper on the subject he takes 
 great pains to ilistinguish the latter as the type of a new 
 genus, from Cuvier's Palwotherimn d'OrUans. But it is 
 precisely the Palwotherinm d'OrUans which is the type 
 of Christol's genus Hipparithermm; and thus, though 
 Hipparitherium is of later date than Anchitherium," it 
 seemed to me to have a sort of equitable right to recog- 
 nition when this Address was written. On the whole, 
 however, it seems most convenient to adopt Anchithe- 
 rium. 
 
xr PALEONTOLOGY AND EVOLUTION. 359 
 
 Cuvier pointed out, a posterior lobe of much 
 smalled size and different form, the dentition of 
 Anchitherium departs from the type of the 
 PalcBotherium, and approaches that of the Horse. 
 Again, the skeleton of Anchitherium is ex- 
 tremely equine. M. Christol goes so far as to say 
 that the description of the bones of the horse, 
 or the ass, current in veterinary works, would fit 
 those of Anchitherium. And, in a general way, 
 this may be true enough; but there are some most 
 important differences, which, indeed, are justly 
 indicated by the same careful observer. Thus the 
 ulna is complete throughout, and its shaft is not a 
 mere rudiment, fused into one bone with the 
 radius. There are three toes, one large in the 
 middle and one small on each side. The femur is 
 quite like that of a horse, and has the character- 
 istic fossa above the external condyle. In the 
 British Museum there is a most instructive 
 specimen of the leg-bones, showing that the fibula 
 was represented by the external malleolus and by 
 a fiat tongue of bone, which extends up from it 
 on the outer side of the tibia, and is closely 
 ankylosed with the latter bone.* The hind toes 
 are three, like those of the fore leg; and the middle 
 
 * I am indebted to M. Gervais for a specimen which 
 indicates that the fibula was complete, at any rate, in 
 some cases; and for a very interesting ramus of a man- 
 dible, which shows that, as in the Palceotlieria, the hind- 
 ermost milk-molar of the lower jaw was devoid of the 
 posterior lobe which exists in the hindermost true molar. 
 
360 PALAEONTOLOGY AND EVOLUTION. xi 
 
 metatarsal bone is much less compressed from side 
 to side than that of the horse. 
 
 In the Hipparion, the teeth nearly resemble 
 those of the Horses, though the crowns of the 
 grinders are not so long; like those of the Horses, 
 they are abundantly coated with cement. The 
 shaft of the ulna is reduced to a mere style, anky- 
 losed throughout nearly its whole length with the 
 radius, and appearing to be little more than a ridge 
 on the surface of the latter bone until it is care- 
 fully examined. The front toes are still three, 
 but the outer ones are more slender than in 
 Anchitlierium, and their hoofs smaller in propor- 
 tion to that of the middle toe; they are, in fact, re- 
 duced to mere dew-claws, and do not touch the 
 ground. In the leg, the distal end of the fibula is 
 so completely united with the tibia that it appears 
 to be a mere process of the latter bone, as in the 
 Horses. 
 
 In Equus, finally, the crowns of the grinding- 
 teeth become longer, and their patterns are slightly 
 modified; the middle of the shaft of the ulna usu- 
 ally vanishes, and its proximal and distal ends 
 ankylose with the radius. The phalanges of the 
 two outer toes in each foot disappear, their meta- 
 carpal and metatarsal bones being left as the 
 " splints." 
 
 The Hipparion has large depressions on the 
 face in front of the*^ orbits, like those for the 
 "larmiers" of many ruminants; but traces of 
 
XI PALEONTOLOGY AND EVOLUTION. 361 
 
 these are to be seen in some of the fossil horses 
 from the Sewalik Hills; and, as Leidy's recent re- 
 searches show, they are preserved in Anchi- 
 therium. 
 
 When we consider these facts, and the further 
 circumstance that the Hipparions, the remains of 
 which have been collected in immense numbers, 
 were subject, as M. Gaudry and others have 
 pointed out, to a great range of variation, it 
 appears to me impossible to resist the conclusion 
 that the types of the Anchitherium, of the 
 Hipparion, and of the ancient Horses consti- 
 tute the lineage of the modern Horses, the Hip- 
 parion being the intermediate stage between the 
 other two, and answering to B in my former illus- 
 tration. 
 
 The process by which the Anchitherium has 
 been converted into Equus is one of specialisation, 
 or of more and more complete deviation from what 
 might be called the average form of an ungulate 
 mammal. In the Horses, the reduction of some 
 parts of the limbs, together with the special modi- 
 fication of those which are left, is carried to a 
 greater extent than in any other hoofed mammals. 
 The reduction is less and the specialisation is less 
 in the Hipparion, and still less in the Anchi- 
 therium; but yet, as compared with other mam- 
 mals, the reduction and specialisation of parts in 
 the Anchitherium remain great. 
 
 Is it not probable then, that, just as in the 
 
362 PALEONTOLOGY AND EVOLUTION. xi 
 
 Miocene epoch, we find an ancestral equine form 
 less modified than Equus, so, if we go back to 
 the Eocene epoch, we shall find some quadruped 
 related to the AncMtherium, as Hipparion is re- 
 lated to Equus, and consequently departing less 
 from the average form? 
 
 I think that this desideratum is very nearly, if 
 not quite, supplied by Plagioloplius, remains of 
 which occur abundantly in some parts of the 
 Upper and Middle Eocene formations. The 
 patterns of the grinding-teeth of Plagiolophus are 
 similar to those of AncMtherium, and their crowns 
 are as thinly covered with cement; but the 
 grinders dimnish in size forwards, and the last 
 lower molar has a large hind lobe, convex outwards 
 and concave inwards, as in Palceotherium. The 
 ulna is complete and much larger than in any of 
 the EquidcB, while it is more slender than in most 
 of the true Palmotheria; it is fixedly united, but 
 not ankylosed, with the radius. There are three 
 toes in the fore limb, the outer ones being slender, 
 but less attenuated than in the Equidce. The 
 femur is more like that of the Palceotheria than 
 that of the horse, and has only a small depression 
 above its outer condyle in the place of the great 
 fossa which is so obvious in the Equidce. The 
 fibula is distinct, but very slender, and its distal end 
 is ankylosed with the tibia. There are three toes 
 on the hind foot having similar proportions to 
 those on the fore foot. The principal metacarpal 
 
XI PALEONTOLOGY AND EVOLUTION. 363 
 
 and metatarsal bones are flatter than they are in 
 any of the Equidce; and the metacarpal bones are 
 longer than the metatarsals, as in the Palmotheria. 
 In its general form, Plagiolophus resembles a 
 very small and slender horse,* and is totally unlike 
 the reluctant, pig-like creature depicted in Cuvier's 
 restoration of his Palwotherium minus in the 
 " Ossemens Fossiles." 
 
 It would be hazardous to say that Plagiolophus 
 is the exact radical form of the Equine quadru- 
 peds; but I do not think there can be any 
 reasonable doubt that the latter animals have 
 resulted from the modification of some quadruped 
 similar to Plagiolophus. 
 
 We have thus arrived at the Middle Eocene 
 formation, and yet have traced back the Horses 
 only to a three-toed stock; but these three-toed 
 forms, no less than the Equine quadrupeds them- 
 selves, present rudiments of the two other toes 
 which appertain to what I have termed the 
 " average " quadruped. If the expectation raised 
 by the splints of the Horses that, in some ancestor 
 of the Horses, these splints would be found to 
 be complete digits, has been verified, we are fur- 
 nished with very strong reasons for looking for a 
 no less complete verification of the expectation 
 that the three-toed Plagiolophus-like " avua " of the 
 
 * Such, at least, is the conclusion suggested by the 
 proportions of the skeleton figured by Cuvier and De 
 Blainville; but perhaps something between a Horse and 
 an' Agouti would be nearest the mark. 
 
364 PALEONTOLOGY AND EVOLUTION. xi 
 
 horse must have had a five-toed "atavus " at some 
 earlier period. 
 
 No such five-toed " atavus," however, has yet 
 made its appearance among the few middle and 
 older Eocene Mammalia which are known. 
 
 Another series of closely affiliated forms, 
 though the evidence they afford is perhaps less 
 complete than that of the Equine series, is pre- 
 sented to us by the Dichdbune of the Eocene epoch, 
 the Cainotherium of the Miocene, and the Tra- 
 gulidce, or so-called "Musk-deer," of the present 
 day. 
 
 The Tragulidm have no incisors in the upper 
 jaw, and only six grinding-teeth on each side of 
 each jaw; while the canine is moved up to the 
 outer incisor, and there is a diastema in the lower 
 jaw. There are four complete toes on the hind 
 foot, but the middle metatarsals usually become, 
 sooner or later, ankylosed into a cannon bone. The 
 navicular and the cuboid unite, and the distal end 
 of the fibula is ankylosed with the tibia. 
 
 In Cainotherium and Dichdbune the upper 
 incisors are fully developed. There are seven 
 grinders; the teeth form a continuous series with- 
 out a diastema. The metatarsals, the naivcular 
 and cuboid, and the distal end of the fibula, 
 remain iree. In the Cainotherium, also, the second 
 metacarpal is developed, but is much shorter than 
 the third, while the fifth is absent or rudimentary. 
 In this respect it resembles Anoplotherium secunda- 
 
XI PALEONTOLOGY AND EVOLUTION. 365 
 
 rium. This circumstance, and the peculiar pattern 
 of the upper molars in Cainofherium, lead me to 
 hesitate in considering it as the actual ancestor 
 of the modern Tragulidce. If Diclidbune has a 
 fore-toed fore foot (though I am inclined to 
 suspect that it resembles Cainofherium), it will 
 be a better representative of the oldest forms of 
 the Traguline series; but Dichohune occurs in the 
 Middle Eocene, and is, in fact, the oldest known 
 artiodactyle mammal. Where, then, must we look' 
 for its five-toed ancestor? 
 
 If we follow down other lines of recent and 
 tertiary Ungulata, the same question presents 
 itself. The Pigs are traceable back through the 
 Miocene epoch to the Upper Eocene, where they 
 appear in the two well-marked forms of Hyopo- 
 potamus and Chceroptamusj but Hyopopotamus ap- 
 pears to have had only two toes. 
 
 Again, all the great groups of the Ruminants, 
 the Bovidce, Antilopidce, C amelopardalidoe, and 
 Cervida, are represented in the Miocene epoch, and 
 so are the Camels. The Upper Eocene Anoplo- 
 therium, which is intercalary between the Pigs 
 and the Tragulidce, has only two, or, at most, 
 three toes. Among the scanty mammals of the 
 Lower Eocene formation we have the perisso- 
 dactyle Ungulata represented by Coryphodon, 
 Hyracotherium, and Pliolophus. Suppose for a 
 moment, for the sake of following out the 
 argument, that Pliolophus represents the primary 
 
366 PALEONTOLOGY AND EVOLUTION. si 
 
 stock of the Perissodactyles, and Dichdbune that 
 of the Artiodactyles (though I am far from saying 
 that such is the ease), then we find, in the earliest 
 fauna of the Eocene epoch to which our investiga- 
 tions carry us, the two divisions of the Ungulata 
 completely differentiated, and no trace of any 
 common stock of both, or of five-toed predecessors 
 to either. With the case of the Horses before us, 
 justifying a belief in the production of new ani- 
 mal forms by modification of old ones, I see no 
 escape from the necessity of seeking for these 
 ancestors of the Ungulata beyond the limits of the 
 Tertiary formations. 
 
 I could as soon admit special creation, at 
 once, as suppose that the Perissodactyles and 
 Artiodactyles had no five-toed ancestors. And 
 when we consider how large a portion of the 
 Tertiary period elapsed before Anchitherium was 
 converted into Equus, it is difficult to escape the 
 conclusion that a large proportion of time anterior 
 to the Tertiary period must have been expended 
 in converting the common stock of the Ungulata 
 into Perissodactyles and Artiodactyles. 
 
 The same moral is inculcated by the study 
 of every other order of Tertiary monodelphous 
 Mammalia. Each of these orders is represented 
 in the Miocene epoch: the Eocene formation, as 
 I have already said, contains Cheiroptera, Insecti- 
 vora, Rodentia, Ungulata, Carnivora, and Cetacea. 
 But the Cheiroptera are extreme modifications 
 
XI PALEONTOLOGY AND EVOLUTION. 367 
 
 of the Insedivora, just as the Cetacea are extreme 
 modifications of the Carnivorous type; and there- 
 fore it is to my mind incredible that monodelphous 
 Insedivora and Carnivora should not have been 
 abundantly developed, along with Ungulata, in 
 the Mesozoic epoch. But if this be the case, 
 how much further back must we go to find the 
 common stock of the monodelphous Mammalia? 
 As to the Didelphia, if we may trust the evidence 
 which seems to be afforded by their very scanty 
 remains, a Hypsiprymnoid form existed at the 
 epoch of the Trias, contemporaneously with a 
 Carnivorous form. At the epoch of the Trias, 
 therefore, the Marswpialia must have already 
 existed long enough to have become differentiated 
 into carnivorous and herbivorous forms. But the 
 Monotremata are lower forms than the Didelphia, 
 which last are intercalary between the Ornitho- 
 delphia and the Monodelphia. To what point of 
 the Palaeozoic epoch, then, must we, upon any 
 rational estimate, relegate the origin of the 
 Monotremata? 
 
 The investigation of the occurrence of the 
 classes and of the orders of the Sauropsida in time 
 points in exactly the same direction. If, as there 
 is great reason to believe, true Birds existed in 
 the Triassic epoch, the ornithoscelidous forms by 
 which Reptiles passed into Birds, must have pre- 
 ceded them. In fact there is, even at present, 
 considerable ground for suspecting the existence 
 
368 PALEONTOLOGY AND EVOLUTION. xi 
 
 of Dinosauria in the Permian formations; but, in 
 that case, lizards must be of still earlier date. 
 And if the very small difEerences which are 
 observable between the Crocodilia of the older 
 Mesozoic formations and those of the present day 
 furnish any sort of approximation towards an esti- 
 mate of the average rate of change among the 
 Sauropsida, it is almost appalling to reflect how far 
 back in Palasozoic times we must go, before we 
 can hope to arrive at that common stock from 
 which the Crocodilia, Lacertilia, Ornithoscelida, 
 and Plesiosauria, which had attained so great a 
 development in the Triassic epoch, must have 
 been derived. 
 
 The Amphibia and Pisces tell the same story. 
 There is not a single class of vertebrated animals 
 which, when it first appears, is represented by 
 analogues of the lowest known members of the 
 same class. Therefore, if there is any truth 
 in the doctrine of evolution, every class must be 
 vastly older than the first record of its appear- 
 ance upon the surface of the globe. But if con- 
 siderations of this kind compel us to place the 
 origin of vertebrated animals at a period 
 sufficiently distant from the Upper Silurian, in 
 which the first Elasmobranchs and Ganoids oc- 
 cur, to allow of the evolution of such fishes 
 as these from a Vertebrate as simple as the 
 AmpMoxus, I can only repeat that it is ap- 
 palling to speculate upon the extent to which 
 
XI PALAEONTOLOGY AND EVOLUTION. 369 
 
 that origin must have preceded the epoch 
 of the first recorded appearance of vertebrate 
 life. 
 
 Such is the further commentary which I have 
 to offer upon the statement of the chief results of 
 palaeontology which I formerly ventured to lay 
 before you. 
 
 But the growth of knowledge in the interval 
 makes me conscious of an omission of considerable 
 moment in that statement, inasmuch as it contains 
 no reference to the bearings of palaeontology upon 
 the theory of the distribution of life; nor takes 
 note of the remarkable manner in which the facts 
 of distribution, in present and past times, accord 
 with the doctrine of evolution, especially in regard 
 to land animals. 
 
 That connection between paleeontology and 
 geology and the present distribution of terrestrial 
 animals, which so strikingly impressed Mr. Darwin, 
 thirty years ago, as to lead him to speak of a " law 
 of succession of types," and of the wonderful re- 
 lationship on the same continent between the 
 dead and the living, has recently received much 
 elucidation from the researches of Gaudry, of 
 Riitimeyer, of Leidy, and of Alphonse Milne- 
 Edwards, taken in connection with the earlier 
 labours of our lamented colleague Falconer; and 
 it has been instructively discussed in the thought- 
 ful and ingenious work of Mr. Andrew Murray 
 210 
 
370 PALEONTOLOGY AND. EVOLUTION. xi 
 
 " On the Geographical Distribution of Mam- 
 mals." * 
 
 I propose to lay before you, as briefly as I can, 
 the ideas to which a long consideration of the 
 subject has given rise in my mind. 
 
 If the doctrine of evolution is sound, one of its 
 immediate consequences clearly is, that the present 
 distribution of life upon the globe is the product 
 of two factors, the one being the distribution 
 which obtained in the immediately preceding 
 epoch, and the other the character and the extent 
 of the changes which have taken place in physical 
 geography between the one epoch and the other; 
 or, to put the matter in another way, the Fauna 
 and Flora of any given area, in any given epoch, 
 can consist only of such forms of life as are directly 
 descended from those which constituted the Fauna 
 and Flora of the same area in the immediately pre- 
 ceding epoch, unless the physical geography (under 
 which I include climatal conditions) of the area 
 has been so altered as to give rise to immigration of 
 living forms from some other area. 
 
 The evolutionist, therefore, is bound to grapple 
 with the following problem whenever it is clearly 
 
 * The paper " On the Form and Distribution of the 
 Landtracts during the Secondary and Tertiary Periods 
 respectively; and on the Effect upon Animal Life which 
 great Changes in Geographical Configuration have prob- 
 ably produced," by Mr. Searles V. Wood, jun., which was 
 published in the Philosophical Magazine, in 1862, was 
 unknown to me when this Address was written. It is 
 well worthy of the most careful study. 
 
XI PALEONTOLOGY AND EVOLUTION. 371 
 
 put before him: — Here are the Faunae of the same 
 area during successive epochs. Show good cause 
 for believing either that these Faunae have been 
 derived from one another by gradual modification, 
 or that the Faunae have reached the area in ques- 
 tion by migration from some area in which they 
 have undergone their development. 
 
 I propose to attempt to deal with this problem, 
 so far as it is exemplified by the distribution of 
 the terrestrial Vertehrata, and I shall endeavour 
 to show you that it is capable of solution in a 
 sense entirely favourable to the doctrine of evo- 
 lution. 
 
 I have elsewhere * stated at length the reasons 
 which lead me to recognise four primary distribu- 
 tional provinces for the terrestrial Vertehrata in the 
 present world, namely, — first, the Novozelanian, 
 or New-Zealand province; secondly, the Australian 
 province, including Australia, Tasmania, and the 
 Negrito Islands; thirdly, Austro-Colunibia, or 
 South America plus North America as far as 
 Mexico; and fourthly, the rest of the world, or 
 Ardogcea, in which province America north of 
 Mexico constitutes one sub-province, Africa south 
 of the Sahara a second, Hindostan a third, and the 
 remainder of the Old World a fourth. 
 
 Now the truth which Mr. Darwin perceived 
 
 * " On the Classification and Distribution of the Alec- 
 toromorphse; " Proceedings of the Zoological Society, 
 1868. 
 
372 PALEONTOLOGY AND EVOLUTION. xi 
 
 and promulgated as " the law of the succession of 
 types " is, that, in all these provinces, the animals 
 found in Pliocene or later deposits are closely 
 affined to those which now inhabit the same pro- 
 vinces; and that, conversely, the forms character- 
 istic of other provinces are absent. North and 
 South America, perhaps,- present one or two 
 exceptions to the last rule, but they are readily 
 susceptible of explanation. Thus, in Australia, the 
 later Tertiary mammals are marsupials (possibly 
 with the exception of the Dog and a Kodent or two, 
 as at present). In Austro-Columbia, the later 
 Tertiary fauna exhibits numerous and varied forms 
 of Platyrrhine Apes, Eodents, Cats, Dogs, Stags, 
 Edentata, and Opossums; but, as at present, no 
 Catarrhine Apes, no Lemurs, no Insedivora, Oxen, 
 Antelopes, Ehinoceroses, nor DidelpMa other than 
 Opossums. And in the widespread Arctogseal 
 province, the Pliocene and later mammals belong 
 to the same groups as those which now exist in 
 the province. The law of succession of types, 
 therefore, holds good for the present epoch as 
 compared with its predecessor. Does it equally 
 well apply to the Pliocene fauna when we com- 
 pare it with that of the Miocene epoch? By 
 great good fortune, an extensive mammalian fauna 
 of the latter epoch has now become known, in 
 four very distant portions of the Arctogseal pro- 
 vince which do not differ greatly in latitude. 
 Thus Falconer and Cautley have made known the 
 
XI PALEONTOLOGY AND EVOLUTION. 373 
 
 fauna of the sub-Himalayas and the Perim Islands; 
 Gaudry that of Attica; many observers that of 
 Central Europe and France; and Leidy that of 
 Nebraska, on the eastern flank of the Eocky 
 Mountains. The results are very striking. The 
 total Miocene fauna comprises many genera and 
 species of Catarrhine Apes, of Bats, of Insedivoraj 
 of Arctogseal types of Rodentiaj of Prohoscideaj of 
 equine, rhinocerotic, and tapirine quadrupeds; of 
 cameline, bovine, antilopine, cervine, and traguline 
 Euminants; of Pigs and Hippopotamuses; of 
 Viverridce and Hymnidm among other Garnivoraj 
 with Edentata allied to the Arctogseal Oryderopus 
 and Manis, and not to the Austro-Columbian 
 Edentates. The only type present in the Miocene, 
 but absent in the existing, fauna of Eastern Arc- 
 togsea, is that of the Didelphidce, which, however, 
 remains in North America. 
 
 But it is very remarkable that while the 
 Miocene fauna of the Arctogseal province, as 
 a whole, is of the same character as the existing 
 fauna of the same province, as a whole, the com- 
 ponent elements of the fauna were differently as- 
 sociated. In the Miocene epoch. North America 
 possessed Elephants, Horses, Ehinoceroses, and a 
 great number and variety of Euminants and Pigs, 
 which are absent in the present indigenous fauna; 
 Europe had its Apes, Elephants, Ehinoceroses, 
 Tapirs, Musk-deer, Giraffes, Hysenas, great Cats, 
 Edentates, and Opossum-like Marsupials, which 
 
374 PALEONTOLOGY AND EVOLUTION. xi 
 
 have equally vanished from its present fauna; 
 and in Northern India, the African types of Hippo- 
 potamuses, Giraffes, and Elephants were mixed 
 up with what are now the Asiatic types of the 
 latter, and with Camels, and Semnopitheeine and 
 Pithecine Apes of no less distinctly Asiatic forms. 
 In fact the Miocene mammalian fauna of 
 Europe and the Himalayan regions contains, asso- 
 ciated together, the types which are at present 
 separately located in the South-African and 
 Indian sub-provinces of Arctogaea. Now there 
 is every reason to believe, on other grounds, that 
 both Hindostan, south of the Ganges, and Africa, 
 south of the Sahara, were separated by a wide 
 sea from Europe and North Asia during the 
 Middle and Upper Eocene epochs. Hence it 
 becomes highly probable that the well-known 
 similarities, and no less remarkable differences, 
 between the present Faunse of India and South 
 Africa have arisen in some such fashion as the 
 following. Some time during the Miocene epoch, 
 possibly when the Himalayan chain was ele- 
 vated, the bottom of the nummulitic sea was 
 upheaved and converted into dry land, in the 
 direction of a line extending from Abyssinia to 
 the mouth of the Ganges. By this means, the 
 Dekhan on the one hand, and South Africa on 
 the other, became connected with the Miocene 
 dry land and with one another. The Miocene 
 mammals spread gradually over this intermediate 
 
XI PALEONTOLOGY AND EVOLUTION. 375 
 
 dry land; and if the condition of its eastern and 
 western ends offered as wide contrasts as the 
 valleys of the Ganges and Arabia do now, many 
 forms which made their way into Africa must 
 have been different from those which reached 
 the Dekhan, while others might pass into both 
 these sub-provinces. 
 
 That there was a continuity of dry land between 
 Europe and North America during the Miocene 
 epoch, appears to me to be a necessary consequence 
 of the fact that many genera of terrestrial mam- 
 mals, such as Castor, Hystrix, Elephas, Mastodon, 
 Equus, Hipparion, AncMtherium, Rhinoceros, Cer- 
 vus, Amphicyon, Hycenarctos, and Machairodus, 
 are common to the Miocene formations of the two 
 areas, and have as yet been found (except per- 
 haps AncMtherium) in no deposit of earlier age. 
 Whether this connection took place by the east, 
 or by the west, or by both sides of the Old World, 
 there is at present no certain evidence, and the 
 question is immaterial to the present argument; 
 but, as there are good grounds for the belief that 
 the Australian provinces and the Indian and 
 South-African sub-provinces were separated by 
 sea from the rest of Arctogsea before the Miocene 
 epoch, so it has been rendered no less probable, 
 by the investigations of Mr. Carrick Moore and 
 Professor Duncan, that Austro-Columbia was sep- 
 arated by sea from Forth America during a large 
 part of the Miocene epoch. 
 
376 PALEONTOLOGY AND EVOLUTION. xi 
 
 It is unfortunate that we have no knowledge 
 of the Miocene mammalian fauna of the Austra- 
 lian and Austro-Columbian provinces; hut, seeing 
 that not a trace of a Platyrrhine Ape, of a Procyo- 
 nine Carnivore, of a characteristically South- 
 American Eodent, of a Sloth, an Armadillo, or an 
 Ant-eater has yet been found in Miocene deposits 
 of Arctogsea, I cannot doubt that they already ex- 
 isted in the Miocene Austro-Columbian province. 
 
 Nor is it less probable that the characteristic 
 types of Australian Mammalia were already de- 
 veloped in that region in Miocene times. 
 
 But Austro-Golumbia presents difficulties from 
 which Australia is free; Camelidce and Tapiridce 
 are now indigenous in South America as they are 
 in Arctogsea; and, among the Pliocene Austro- 
 Columbian mammals, the Arctogseal genera 
 Equus, Mastodon, and Machairodus are numbered. 
 Are these Postmiocene immigrants, or Prsemio- 
 cene natives? 
 
 Still more perplexing are the strange and in- 
 teresting forms Toxodon, Macrauchenia, Typo- 
 therium, and a new Anoplotherioid mammal 
 {Homalodotherium) which Dr. Cunningham sent 
 over to me some time ago from Patagonia. I con- 
 fess I am strongly inclined to surmise that these 
 last, at any rate, are remnants of the popula- 
 tion of Austro-Columbia before the Miocene epoch, 
 and were not derived from Arctogsa by way of 
 the north and east. 
 
XI PALEONTOLOGY AND EVOLUTION. 377 
 
 The fact that this immense fauna of Miocene 
 Arctogsea is now fully and richly represented only 
 in India and in South Africa, while it is shrunk 
 and depauperised in North Asia, Europe, and 
 North America, becomes at once intelligible, if we 
 suppose that India and South Africa had but a 
 scanty mammalian population before the Miocene 
 immigration, while the conditions were highly fa- 
 vourable to the new comers. It is to be supposed 
 that these new regions ofEered themselves to the 
 Miocene Ungulates, as South America and Aus- 
 tralia offered themselves to the cattle, sheep, and 
 horses of modern colonists. But, after these great 
 areas were thus peopled, came the Glacial epoch, 
 during which the excessive cold, to say nothing of 
 depression and ice-covering, must have almost de- 
 populated all the northern parts of Arctogsea, de- 
 stroying all the higher mammalian forms, except 
 those which, like the Elephant and Ehinoceros, 
 could adjust their coats to the altered conditions. 
 Even these must have been driven away from the 
 greater part of the area; only those Miocene mam- 
 mals which had passed into Hindostan and into 
 South Africa would escape decimation by such 
 changes in the physical geography of Arctogsea. 
 And when the northern hemisphere passed into 
 its present condition, these lost tribes of the Mio- 
 cene Fauna were hemmed by the Himalayas, the 
 Sahara, the Eed Sea, and the Arabian deserts, 
 within their present boundaries. 
 
378 PALEONTOLOGY AND EVOLUTION. xi 
 
 Now, on this hypothesis of evolution, there is 
 no sort of difficulty in admitting that the differ- 
 ences between the Miocene forms of the mammal- 
 ian Fauna and those which exist at present are the 
 results of gradual modification; and, since such 
 differences in distribution as obtain are readily 
 explained by the changes which have taken place 
 in the physical geography of the world since the 
 Miocene epoch, it is clear that the result of the 
 comparison of the Miocene and present Faunas is 
 distinctly in favour of evolution. Indeed I may 
 go further. I may say that the hypothesis of 
 evolution explains the facts of Miocene, Pliocene, 
 and Eeeent distribution, and that no other sup- 
 position even pretends to account for them. It 
 is, indeed, a conceivable supposition that every 
 species of Ehinoceros and every species of Hyaena, 
 in the long succession of forms between the Mio- 
 cene and the present species, was separately con- 
 structed out of dust, or out of nothing, by super- 
 natural power; but until I receive distinct evi- 
 dence of the fact, I refuse to run the risk of insult- 
 ing any sane man by supposing that he seriously 
 holds such a notion. 
 
 Let us now take a step further back in time, 
 and inquire into the relations between the Miocene 
 Fauna and its predecessor of the Upper Eocene 
 formation. 
 
 Here it is to be regretted that our materials for 
 forming a judgment are nothing to be compared 
 
XI PAL^ONTOLOGr AND EVOLUTION. 379 
 
 in point of extent or variety with those which are 
 yielded by the Miocene strata. However, what we 
 do know of this Upper Eocene Fauna of Europe 
 gives sufficient positive information to enable us 
 to draw some tolerably safe inferences. It has 
 yielded representatives of Insedivora, of Cheir- 
 optera, of Rodentia, of Carnivora, of artiodactyle 
 and perissodactyle Ungulata, and of opossum-like 
 Marsupials. No Australian type of Marsupial has 
 been discovered in the Upper Eocene strata, nor 
 any Edentate mammal. The genera (except per- 
 haps in the case of some of the Insedivora, Cheir- 
 optera, and Rodentia) are different from those of 
 the Miocene epoch, but present a remarkable gen- 
 eral similarity to the Miocene and recent genera. 
 In several cases, as I have already shown, it has 
 now been clearly made out that the relation be- 
 tween the Eocene and Miocene forms is such that 
 the Eocene form is the less specialised; while its 
 Miocene ally is more so, and the specialisation 
 reaches its maximum in the recent forms of the 
 same type. 
 
 So far as the Upper Eocene and the Miocene 
 Mammalian Faunae are comparable, their relations 
 are such as in no way to oppose the hypothesis 
 that the older are the progenitors of the more 
 recent forms, while, in some cases, they distinctly 
 favour that hypothesis. The period in time and 
 the changes in physical geography represented by 
 the mummulitic deposits are undoubtedly very 
 
380 PALAEONTOLOGY AND EVOLUTION. xi 
 
 great, while the remains of Middle Eocene and 
 Older Eocene Mammals are comparatively few. 
 The general facies of the Middle Eocene Fauna, 
 however, is quite that of the Upper. The Older 
 Eocene pre-mummulitie mammalian Fauna con- 
 tains Bats, two genera of Garnivora, three genera 
 of Ungulata (probably all perissodactyle), and a 
 didelphid Marsupial; all these forms, except per- 
 haps the Bat and the Opossum, belong to genera 
 which are not known to occur out of the Lower 
 Eocene formation. The Coryphodon appears to 
 have been allied to the Miocene and later Tapirs, 
 while Pliolophus, in its skull and dentition, curi- 
 ously partakes of both artiodactyle and perisso- 
 dactyle characters; the third trochanter upon 
 its femur, and its three-toed hind foot, however, 
 appear definitely to fix its position in the latter 
 division. 
 
 There is nothing, then, in what is known of the 
 older Eocene mammals of the Arctogseal province 
 to forbid the supposition that they stood in an 
 ancestral relation to those of the Calcaire Grossier 
 and the Gypsum of the Paris basin, and that our 
 present fauna, therefore, is directly derived from 
 that which already existed in Arctogsea at the 
 commencement of the Tertiary period. But if 
 we now cross the frontier between the Cainozoic 
 and the Mesozoic faunae, as they are preserved 
 within the Arctogteal area, we meet with an 
 astounding change, and what appears to be a 
 
XI PALEONTOLOGY AND EVOLUTION. 381 
 
 complete and unmistakable break in the line of 
 biological continuity. 
 
 Among the twelve or fourteen species of Mam- 
 malia which are said to have been found in the 
 Purbecks, not one is a member of the orders 
 Cheiroptera, Rodentia, Ungulata, or Carnivora, 
 which are so well represented in the Tertiaries. 
 No Insectivora are certainly known, nor any opos- 
 sum-like Marsupials. Thus there is a vast nega- 
 tive difference between the Cainozoic and the 
 Mesozoic mammalian faunae of Europe. But there 
 is a still more important positive difference, in- 
 asmuch as all these Mammalia appear to be 
 Marsupials belonging to Australian groups, and 
 thus appertaining to a different distributional 
 province from the Eocene and Miocene marsupials, 
 which are Austro-Columbian. So far as the im- 
 perfect materials which exist enable a judgment 
 to be formed, the same law appears to have held 
 good for all the earlier Mesozoic Mammalia. Of 
 the Stonesfield slate mammals, one, Amphither- 
 ium, has a definitely Australian character; one, 
 Phascolotherium, may be either Dasyurid or 
 Didelphine; of a third, Stereognathus, nothing 
 can at present be said. The two mammals 
 of the Trias, also, g,ppear to belong to Australian 
 groups. 
 
 Every one is aware of the many curious points 
 of resemblance between the marine fauna of the 
 European Mesozoic rocks and that which now ex- 
 
382 PALiEONTOLOGT AND EVOLUTION. xi 
 
 ists in Australia. But if there was this Austra- 
 lian facies about both the terrestrial and the 
 marine faunse of Mesozoic Europe, and if there 
 is this unaccountable and immense break between 
 the fauna of Mesozoic and that of Tertiary Eu- 
 rope, is it not a very obvious suggestion that, 
 in the Mesozoic epoch, the Australian province 
 included Europe, and that the ArctogEeal province 
 was contained within other limits? The Areto- 
 g£eal province is at present enormous, while the 
 Australian is relatively small. Why should not 
 these proportions have been different during the 
 Mesozoic epoch? 
 
 Thus I am led to think that by far the sim- 
 plest and most rational mode of accounting for 
 the great change which took place in the living 
 inhabitants of the European area at the end of 
 the Mesozoic epoch, is the supposition that it 
 arose from a vast alteration of the physical geog- 
 raphy of the globe; whereby an area long ten- 
 anted by Cainozoic forms was brought into such 
 relations with the European area that migration 
 from the one to the other became possible, and 
 took place on a great scale. 
 
 This supposition relieves us, at once, from the 
 difficulty in which we were left, some time ago, 
 by the arguments which I used to demonstrate 
 the necessity of the existence of all the great 
 types of the Eocene epoch in some antecedent 
 period. 
 
XI PALEONTOLOGY AND EVOLUTION. 383 
 
 It is this Mesozoic continent (which may well 
 have lain in the neighbourhood of what are now 
 the shores of the North Pacific Ocean) which I 
 suppose to have been occupied by the Mesozoic 
 Monodelphia; and it is in this region that I con- 
 ceive they must have gone through the long se- 
 ries of changes by which they were specialised 
 into the forms which we refer to different orders. 
 I think it very probable that what is now South 
 America may have received the characteristic ele- 
 ments of its mammalian fauna during the Meso- 
 zoic epoch; and there can be little doubt that 
 the general nature of the change which took 
 place at the end of the Mesozoic epoch in Europe 
 was the upheaval of the eastern and northern 
 regions of the Mesozoic sea-bottom into a west- 
 ward extension of the Mesozoic continent, over 
 which the mammalian fauna, by which it was al- 
 ready peopled, gradually spread. This invasion 
 of the land was prefaced by a previous invasion of 
 the Cretaceous sea by modern forms of moUusca 
 and fish. 
 
 It is easy to imagine how an analogous change 
 might come about in the existing world. There 
 is, at present, a great difference between the fauna 
 of the Polynesian Islands and that of the west 
 coast of America. The animals which are leaving 
 their spoils in the deposits now forming in these 
 localities are widely different. Hence, if a grad- 
 ual shifting of the deep sea, which at present bars 
 
384 PALiEONTOLOGY AND EVOLUTION. xi 
 
 migration between the easternmost of these isl- 
 ands and America, took place to the westward, 
 while the American side of the sea-bottom was 
 gradually upheaYed, the paleontologist of the fu- 
 ture would find, over the Pacific area, exactly such 
 a change as I am supposing to have occurred in 
 the North- Atlantic area at the close of the Meso- 
 zoic period. An Australian fauna would be found 
 underlying an American fauna, and the transition 
 from the one to the other would be as abrupt as 
 that between the Chalk and lower Tertiaries; and 
 as the drainage-area of the newly formed exten- 
 sion of the American continent gave rise to rivers 
 and lakes, the mammals mired in their mud would 
 differ from those of like deposits on the Australian 
 side, just as the Eocene mammals differ from those 
 of the Purbecks. 
 
 How do similar reasonings apply to the other 
 great change of life — that which took place at the 
 end of the Paleozoic period? 
 
 In the Triassic epoch, the distribution of the 
 dry land and of terrestrial vertebrate life appears 
 to have been, generally, similar to that which 
 existed in the Mesozoic epoch; so that the Triassic 
 continents and their faunse seem to be related to 
 the Mesozoic lands and their faunas, Just as those 
 of the Miocene epoch are related to those of the 
 present day. In fact, as I have recently endeav- 
 oured to prove to the Society, there was an Arcto- 
 gseal continent and an Arctogsal province of dis- 
 
XI PALEONTOLOGY AND EVOLUTION. 385 
 
 tribution in Triassic times as there is now; and 
 the Sauropsida and Marsupialia which constituted 
 that fauna were, I doubt not, the progenitors of 
 the Sauropsida and Marsupialia of the whole 
 Mesozoic epoch. 
 
 Looking at the present terrestrial fauna of 
 Australia, it appears to me to be very probable 
 that it is essentially a remnant of the fauna of the 
 Triassic, or even of an earlier, age; * in which 
 case Australia must at that time have been in con- 
 tinuity with the Arctogseal continent. 
 
 But now comes the further inquiry. Where was 
 the highly differentiated Sauropsidan fauna of the 
 Trias in Palseozoie times? The supposition that 
 the Dinosaurian, Crocodilian, Dicynodontian, and 
 Plesiosaurian types were suddenly created at the 
 end of the Permian epoch may be dismissed, with- 
 out further consideration, as a monstrous and un- 
 warranted assumption. The supposition that all 
 these types were rapidly differentiated out of 
 Lacertilia in the time represented by the passage 
 from the Palseozoic to the Mesozoic formation, ap- 
 pears to me to be hardly more credible, to say 
 nothing of the indications of the existence of Di- 
 nosaurian forms in the Permian rocks which have 
 already been obtained. 
 
 * Since this Address was read, Mr. Krefft has sent us 
 news of the discovery in Australia of a freshwater fish 
 of strangely Palseozoic aspect, and apparently a Ganoid 
 intermediate between Dipterus and Lepidosiren. [The 
 now well-known Ceratodvs. 1894.] 
 211 
 
386 PAL^OKTOLOGY AND EVOLUTION. xt 
 
 For my part, I entertain no sort of doubt that 
 the Eeptiles, Birds, and Mammals of the Trias are 
 the direct descendants of Eeptiles, Birds, and 
 Mammals which existed in the latter part of the 
 Palaeozoic epoch, hut not in any area of the pres- 
 ent dry land which has yet heen explored by the 
 geologist. 
 
 This may seem a bold assumption, but it will 
 not appear unwarrantable to those who reflect 
 upon the very small extent of the earth's surface 
 which has hitherto exhibited the remains of the 
 great Mammalian fauna of the Eocene times. In 
 this respect, the Permian land Vertebrate fauna 
 appears to me to be related to the Triassic much 
 as the Eocene is to the Miocene. Terrestrial rep- 
 tiles have been found in Permian rocks only in 
 three localities; in some spots of France, and re- 
 cently of England, and over a more extensive area 
 in Germany. Who can suppose that the few fos- 
 sils yet found in these regions give any sufficient 
 representation of the Permian fauna? 
 
 It may be said that the Carboniferous forma- 
 tions demonstrate the existence of a vast extent 
 of dry land in the present dry-land area, and that 
 the supposed terrestrial Palasozoie Vertebrate 
 Fauna ought to have left its remains in the Coal- 
 measures, especially as there is now reason to be- 
 lieve that much of the coal was formed by the 
 accumulation of spores and sporangia on dry land. 
 But if we consider the matter more closely, I 
 
XI PALEONTOLOGY AND EVOLUTION. 387 
 
 think that this apparent objection loses its force. 
 It is clear that, during the Carboniferous epoch, 
 the vast area of land which is now covered by 
 Coal-measures must have been undergoing a grad- 
 ual depression. The dry land thus depressed must, 
 therefore, have existed, as such, before the Car- 
 boniferous epoch — in other words, in Devonian 
 times — and its terrestrial population may never 
 have been other than such as existed during the 
 Devonian, or some previous epoch, although much 
 higher forms may have been developed elsewhere. 
 Again, let me say that I am making no gratu- 
 itous assumption of inconceivable changes. It 
 is clear that the enormous area of Pplynesia is, 
 on the whole, an area over which depression has 
 taken place to an immense extent; consequently 
 a great continent, or assemblage of subcontinental 
 masses of land, must have existed at some former 
 time, and that at a recent period, geologically 
 speaking, in the area of the Pacific. But if that 
 continent had contained Mammals, some of them 
 must have remained to tell the tale; and as it is 
 well known that these islands have no indigenous 
 Mammalia, it is safe to assume that none existed. 
 Thus, midway between Australia and South 
 America, each of which possesses an abundant 
 and diversified mammalian fauna, a mass of land, 
 which may have been as large as both put together, 
 must have existed without a mammalian inhab- 
 itant. Suppose that the shores of this great land 
 
388 PALEONTOLOGY AND EVOLUTION. xi 
 
 were fringed, as those of tropical Australia are 
 now, with belts of mangroves, which would extend 
 landwards on the one side, and be buried beneath 
 littoral deposits on the other side, as depression 
 went on; and great beds of mangrove lignite 
 might accumulate over the sinking land. Let 
 upheaval of the whole now take place, in 
 such a manner as to bring the emerging land 
 into continuity with the South-American or 
 Australian continent, and, in course of time, it 
 would be peopled by an extension of the fauna 
 of one of these two regions — ^just as I imagine 
 the European Permian dry land to have been 
 peopled. 
 
 I see nothing whatever against the supposition 
 that distributional provinces of terrestrial life ex- 
 isted in the Devonian epoch, inasmuch as M. Bar- 
 rande has proved that they existed much earlier. 
 I am aware of no reason for doubting that, as 
 regards the grades of terrestrial life contained in 
 them, one of these may have been related to an- 
 other as New Zealand is to Australia, or as Aus- 
 tralia is to India, at the present day. Analogy 
 seems to me to be rather in favour of, than against, 
 the supposition that while only Ganoid fishes in- 
 habited the fresh waters of our Devonian land, 
 Amphibia and Eeptilia, or even higher forms, may 
 have existed, though we have not yet found them. 
 The earliest Carboniferous Amphibia now known, 
 such as Anthracosaurus, are so highly specialised 
 
XI PALEONTOLOGY AND EVOLUTION. 389 
 
 that I can by no means conceive that they have 
 been developed out of piscine forms in the in- 
 terval between the Devonian and the Carbonifer- 
 ous periods, considerable as that is. And I take 
 refuge in one of two alternatives: either they ex- 
 isted in our own area during the Devonian epoch 
 and we have simply not yet found them; or they 
 formed part of the population of some other dis- 
 tributional province of that day, and only entered 
 our area by migration at the end of the Devonian 
 epoch. Whether Eeptilia and Mammalia existed 
 along with them is to me, at present, a perfectly 
 open question, which is just as likely to receive 
 an affirmative as a negative answer from future 
 inquirers. 
 
 Let me now gather together the threads of my 
 argumentation into the form of a connected hypo- 
 thetical view of the manner in which the distri- 
 bution of living and extinct animals has been 
 brought about. 
 
 I conceive that distinct provinces of the distri- 
 bution of terrestrial life have existed since the 
 earliest period at which that life is recorded, and 
 possibly much earlier; and !• suppose, with Mr. 
 Darwin, that the progress of modification of terres- 
 trial forms is more rapid in areas of elevation than 
 in areas of depression. I take it to be certain that 
 Labyrinthodont Amphibia existed in the distribu- 
 tional province which included the dry land de- 
 pressed during the Carboniferous epoch; and 
 
390 PAL^ONTOLOGT AND EVOLUTION. xi 
 
 I conceive that, in some other distributional 
 provinces of that day, which remained in the 
 condition of stationary or of increasing dry 
 land, the various types of the terrestrial Sau- 
 ropsida and of the Mammalia were gradually de- 
 veloping. 
 
 The Permian epoch marks the commencement 
 of a new movement of upheaval in our area, which 
 attained its maximum in the Triassic epoch, when 
 dry land existed in North America, Europe, Asia, 
 and Africa, as it does now. Into this great new 
 continental area the Mammals, Birds, and Eeptiles 
 developed during the Palsezoic epoch spread, and 
 formed the gr^at Triassic Arctogaal province. 
 But, at the end of the Triassic period, the move- 
 ment of depression recommenced in our area, 
 though it was doubtless balanced by elevation 
 elsewhere; modification and development, checked 
 in the one province, went on in that " elsewhere "; 
 and the chief forms of Mammals, Birds, and Eep- 
 tiles, as we know them, were evolved and peopled 
 the Mesozoic continent. I conceive Australia to 
 have become separated from the continent as 
 early as the end of the Triassic epoch, or not 
 much later. The Mesozoic continent must, I con- 
 ceive, have lain to the east, about the shores 
 of the North Pacific and Indian Oceans; and I 
 am inclined to believe that it continued along 
 the eastern side of the Pacific area to what 
 is now the province of Austro-Columbia, the 
 
XI PALEONTOLOGY AND JIVOLUTION. 391 
 
 characteristic iauna of which is probably a rem- 
 nant of the population of the latter part of this 
 period. 
 
 Towards the latter part of the Mesozoie pe- 
 riod the moYement of upheaval around the shores 
 of the Atlantic once more recommenced, and was 
 very probably accompanied by a depression around 
 those of the Pacific. The Vertebrate fauna elabo- 
 rated in the Mesozoie continent moved westward 
 and took possession of the new lands, which gradu- 
 ally increased in extent up to, and in some direc- 
 tions after, the Miocene epoch. 
 
 It is in favour of this hypothesis, I think, that 
 it is consistent with the persistence of a general 
 uniformity in the positions of the great masses of 
 land and water. From the Devonian period, or 
 earlier, to the present day, the four great oceans, 
 Atlantic, Pacific, Arctic, and Antarctic, may have 
 occupied their present positions, and only their 
 coasts and channels of communication have under- 
 gone an incessant alteration. And, finally, the 
 hypothesis I have put before you requires no 
 supposition that the rate of change in organ- 
 ic life has been either greater or less in ancient 
 times than it is now; nor any assumption, either 
 physical or biological, which has not its jus- 
 tification in analogous phenomena of existing 
 nature. 
 
 I have now only to discharge the last duty of 
 
392 PALEONTOLOGY AND EVOLUTION. xi 
 
 my office, which is to thank you, not only for 
 the patient attention with which you have listened 
 to me so long to-day, but also for the uniform 
 kindness with which, for the past two years, you 
 have rendered my endeavours to perform the im- 
 portant, and often laborious, functions of your 
 President a pleasure instead of a burden. 
 
 END OF VOLUME VIII.