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DISCOURSES: 
 
 BIOLOGICAL & GEOLOGICAL 
 
 ESSAYS 
 
 THOMAS H. HUXLEY 
 
 ILontion 
 
 MACMILLAN AND CO. 
 1894 
 
Richard Clay and Sons, limited, 
 london and bungay. 
 
PREFACE 
 
 The contents of the present volume, with three 
 exceptions, are either popular lectures, or addresses 
 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 efforts 
 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 
 laboratory and the museum, into language which, 
 without bating a jot of scientific accuracy shall be 
 generally 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 
 
Va PREFACE 
 
 in pursuits remote from the common ways of men, 
 and become habituated to think and speak in the 
 technical 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 efforts have led me to entertain 
 a very moderate estimate of the purely intellectual 
 value of lectures ; 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 indepen- 
 dent 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 flexibihty 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 
 despised a good dinner ; and, I imagine, rose with- 
 
PREFACE VI 1 
 
 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 
 applause 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 reported 
 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 htiman 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 
 popularization 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 
 
via PREFACE 
 
 recently had occasion to observe, by ignoring all 
 the rest of a man's work and glibly labelling him 
 a mere popularizer. 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 qualifies them for discuss- 
 ing the great problems of science, it may be said, 
 as the Radical toast said of the power of the Crown 
 in bygone days, that it " has increased, is increas- 
 ing, and ought to be diminished." The oddities 
 of " English as she is spoke " might be abundantly 
 paralleled by those of " Science as she is misunder- 
 stood " in the sennon, the novel, and the leading 
 article ; and a collection of the grotesque trav- 
 esties 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 
 heretics as we seemed to be ; and that, even if 
 
PREFACE ]X 
 
 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 Kelvin 
 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 mathem.atics, 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 aU hving 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 
 successive Faunae and Florse of the earth, the 
 existence of which is fully demonstrated by 
 paleontology 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 ; not cocoa-nuts nor 
 acorns ; not even eggs of shell-fish and corals ; 
 but only those of the lowest forms of animal and 
 vegetable life. Therefore, since it is proved that, 
 ' Popular Lectures and Addresses. II. Maemillan and Co. 1894. 
 
X PREFACE 
 
 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 paleontology 
 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 paleo- 
 zoic 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 paleonto- 
 logical facts, the bearing of which I believe, up to 
 that time, had not been shown, that any ade- 
 quate hypothesis of the causes of evolution must 
 be consistent with progression, stationariness and 
 retrogression, of the same type at different epochs ; 
 of different types in the same epoch ; and that 
 Darwin's hypothesis fulfilled these conditions. 
 
PEEFACE XI 
 
 According to that hypothesis, two factors are at 
 work, variation and selection. Next to nothing is 
 known of the causes of the former process ; nothing 
 whatever of the time required for the production 
 of a certain amount of deviation from the existing 
 type. And, as respects selection, which operates 
 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. Huxley. 
 
 HODESLEA, EASTBOUKNE, 
 April, 1894. 
 
CONTENTS 
 
 I 
 
 PAGE 
 ON A PIECE OF CHALK [1868] 1 
 
 (A. Lecture delivered to the working men of 
 Norwich during the meeting of the British 
 Association.) 
 
 II 
 
 THE PROBLEMS OF THE DEEP SEA [1873] 37 
 
 III 
 
 on some of the kesolts of the expedition of h.m.s. 
 "challensek" [1875] ... 
 
 IV 
 
 YEAST [1871] . . 110 
 
XIV CONTENTS 
 
 V 
 
 PAGE 
 ON THE FOKMATION OF COAL [1870] 137 
 
 (A Lecture delivered at the Philosophical 
 Institute, Bradford. ) 
 
 VI 
 
 ox THE BORDER TERRITOEY BETWEEN THE ANIMAL AND 
 
 THE VEGETABLE KINGDOMS [1876] 162 
 
 (A Friday evening Lecture delivered at the 
 Eoyal Institution.) 
 
 VII 
 
 A LOBSTER ; OR, THE STUDY OF ZOOLOGY [1861] . . • . . 196 
 
 (A Lecture delivered at the South Kensington 
 Museum. ) 
 
 VIII 
 
 BIOGENESIS AND ABIOGENESIS [1870] 229 
 
 (The Presidential Address to the Meeting of 
 the British Association for the Advance- 
 ment of Science at Liverpool.) 
 
 IX 
 
 GEOLOGICAL CONTEMPORANEITY AND PERSISTENT TYPES 
 
 OF LIFE [1862] . . 272 
 
 (Address to the Geological Society on behalf 
 of the President hy one of the Secretaries. ) 
 
CONTENTS XV 
 
 X 
 
 PACE 
 
 GEOLOGICAL KEFOEM [1869] 305 
 
 (Presidential Address to the Geological 
 Society. ) 
 
 XI 
 
 PAL^ffiONTOLOGY AND THE DOCTRINE OF EVOLUTION [1870] 340 
 
 (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 suppHes that long 
 
 VOL. VIII !E B 
 
2 ON A PIECE OF CHALK I 
 
 line of white cliffs to which England owes her 
 name of Albion. 
 
 Were the thin soil which covers it all washed 
 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 
 deposits ; but, except in the Weald of Kent and 
 Sussex, 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 
 
I ON A PIECE OF CHALK 3 
 
 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 
 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. 
 But on our southern coasts, the wall-sided cliffs, 
 many hundred feet high, with vast needles and 
 pinnacles standing out in the sea, sharp and 
 solitary enough to serve as perches for the wary 
 cormorant, 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 
 attempt to solve such problems as these can lead 
 
 B 2 
 
4 ON A PIECE OP CHALK 1 
 
 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 
 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 fi:agment 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 
 history, is likely, if he will think his knowledge 
 out to its ultimate results, to have a truer, and 
 therefore 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 hvimanity and ignorant of those of 
 Nature. 
 
I ON A PIECE OF CHALK 5 
 
 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 features of the story it has to 
 tell ; and I propose that we now set to work to 
 spell that story out together. 
 
 We all know that if we " burn " 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 
 vinegar, there would be a great bubbHng 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 
 essentially nothing but carbonic acid and quick- 
 lime. Chemists enunciate the result of all the 
 experiments which prove this, by stating that 
 chalk is almost wholly composed of "carbonate 
 of lime." 
 
 It is desirable for us to start from the knowledge 
 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 
 
6 ON A PIECE OF CHALK I 
 
 carbonate of lime. The crust which is often 
 deposited by waters which have drained through 
 limestone rocks, in the form of what are called 
 stalagmites and stalactites, is carbonate of lime. 
 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 can 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 different 
 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 
 hundredth of an inch in diameter, having a well- 
 defined shape and structure. A cubic inch of 
 
I ON A PIECE OF CHALK 7 
 
 some specimens of chalk may contain hundreds of 
 thousands of these bodies, compacted together 
 with incalculable millions of the gi-anules. 
 
 The examination of a transparent slice gives a 
 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 off 
 the milky fluid, so as to obtain sediments of 
 different degrees of fineness, the granules and 
 the minute rounded bodies may be pretty well 
 separated from one another, and submitted to 
 microscopic examination, either as opaque or as 
 transparent objects. By combining the views 
 obtained in these various methods, each of the 
 rounded bodies may be proved to be a beautifully- 
 constructed calcareous fabric, made up of a 
 number of chambers, communicating freely with 
 one another. The chambered bodies are of 
 various forms. One of the commonest is some- 
 thing like a badly-grown raspberry, being formed 
 of a number of nearly globular chambers of 
 different sizes congregated together. It is called 
 Glohigcrina, and some specimens of chalk consist 
 of little else than Glohigcrincc and granules. Let 
 us fix our attention upon the Glohigcrina. 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. 
 
8 ON A PIECE OF CHALK I 
 
 A suggestion which may naturally enough pre- 
 sent itself is, that these curious bodies are the 
 result of some process of aggi-egation which has 
 taken place in the carbonate of lime ; that, just 
 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, 
 carbonate 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 objection. 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 
 admissible, it is because long and varied ex- 
 perience 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 suppose 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 GloUgcrina is not the product of 
 anything but vital activity. 
 
I ON A PIECE OF CHALK 9 
 
 Happily, however, better evidence in proof of 
 the organic nature of the Glohigerinm than that 
 of analogy is forthcoming. It so happens that 
 calcareous skeletons, exactly similar to the 
 Glohigerinm of the chalk, are being formed, at 
 the present moment, by minute living creatures, 
 which flourish in multitudes, literally more 
 numerous 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 
 Glohigerinm, and of the part which they play in 
 rock building, is singular enough. It is a 
 discovery which, like others of no less scientific 
 importance, 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 
 
10 ON A PIECE OF CHALK 1 
 
 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 
 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 
 Atlantic, 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 Glohigerinw 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 
 
I ON A PIECE OF CHALK 11 
 
 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 
 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 Ls 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 oi 
 Atlantic mud which he procured were sent to me 
 to be examined and reported upon.^ 
 
 ' See Appendix to Captain Dayman's Deep-sea Soundings in 
 the North Atlantic Ocean between Ireland and Newfoiundland, 
 madein H.M.S. "Cyclops." Published by order of the Lords 
 Commissioners of the Admiralty, 1858. They have since 
 formed the subject of an elaborate Memoir by Messrs. Parker 
 and Jones, published in the Philosophical Transactions for 
 1865. 
 
12 ON A PIECE OF CHALK I 
 
 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 
 know that of any part of the dry land. It is a 
 prodigious plain — one of the widest and most even 
 plains in the world. If the sea were drained off, 
 you might drive a waggon all the way from 
 Valentia, on the west coast of Ireland, to Trinity 
 Bay, in Newfoundland. And, except upon one 
 sharp incline about 200 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 central plain, more than a thousand miles wide, 
 the inequalities of the surface of which would be 
 hardly 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 
 
1 ON A PIECE OF CHALK 13 
 
 into a greyish white friable substance. You can 
 write with this on a blackboard, if you are so 
 inclined ; and, to the eye, it is quite like very soft, 
 grayish chalk. Examined chemically, it proves to 
 be composed almost wholly of carbonate of Hme ; 
 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 
 Glohigerinm 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 GlohigerincB of the chalk, — it is un- 
 necessary to speak of them. 
 
 GlobigerincB 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 
 description. 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 particle, 
 devoid of everything which, in the higher animals. 
 
14 ON A PIECE OF CHALK I 
 
 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 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 apparently 
 living Glohigerinai 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 Gldbigerinm of the Atlantic 
 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 Glohigerinw, 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 
 silicious bodies belong partly to the lowly vege- 
 table organisms which are called Biatomacem, and 
 partly to the minute, and extremely simple, 
 animals, termed Badiolaria. It is quite certain 
 that these creatures do not live at the bottom of 
 the ocean, but at its siu'face — ^where they may be 
 
I ON A PIECE OF CHALK 15 
 
 obtained in prodigious numbers by the use of a 
 properly constructed net. Hence it follows that 
 these silicious organisms, though they are not 
 heavier than the lightest dust, must have fallen, 
 in some cases, 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 
 journey 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 
 superficial layer of its waters in which they pass 
 their lives, it is obviously possible that the 
 Olohigcrinw may be similarly derived ; and if they 
 were so, it would be much more easy to under- 
 stand how they obtain their supply of food than 
 it is at present. Nevertheless, the positive and 
 negative evidence all points the other way. The 
 skeletons of the full-grown, deep-sea Glohigcrinm 
 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 Badiolaria in the 
 uppermost stratum of the open ocean. It has 
 been observed, again, that the abundance of 
 GlobigeriruB, in proportion to other organisms, of 
 like kind, increases with the depth of the sea ; and 
 
16 ON A PIECE OF CHALK I 
 
 that deep-water GldbigeriTwe are larger than those 
 which live in shallower parts of the sea ; and such 
 facts negative the supposition that these organisms 
 have been swept by currents from the shallows 
 into the deeps of the Atlantic. It therefore seems 
 to be hardly doubtful that these wonderful 
 creatures live and die at the depths in which they 
 are found.'^ 
 
 However, the important points for us are, that 
 the living Glohigerinm are exclusively marine 
 animals, the skeletons of which abound at the 
 bottom of deep seas ; and that there is not a 
 shadow of reason for believing that the habits of 
 the GlobigeriTtce of the chalk differed from those 
 of the existing species. But if 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 tempted 
 
 1 During the cruise of H.M.S. Bulldog, commanded by Sir 
 Leopold M'Clintock, in 1860, living star-iisli were brought up, 
 clinging to the lowest part of the sounding-line, from a depth 
 of 1,260 fathoms, midway between Cape Farewell, in Green- 
 land, and the Eockall banks. Dr. Wallich ascertained that 
 the sea-bottom at this point consisted of the ordinary Globi- 
 gerina ooze, and that the stomachs of the star-fishes were full 
 of Globigerirue. This discovery removes all objections to the 
 existence of living Glohigmnm at great depths, which are based 
 upon the supposed difiiculty of maintaining animal life under 
 such conditions ; and it throws the burden of proof upon those 
 who object to the supposition that the Glohigeriiue live and 
 die where they are found. 
 
I ON A PIECE OP CHALK 17 
 
 to think at first, the mere powder and waste of 
 Gldbigerinoe, but that they had a definite form and 
 size. I termed these bodies " coccoliths,'' and 
 doubted their organic nature. Dr. Wallich verified 
 my observation, and added the interesting dis- 
 covery that, not unfrequently, bodies similar to 
 these '■■ coccoHths '' were aggregated together into 
 spheroids, which he termed " coccosphens." 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 forih. 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. Gloligerincc, 
 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 oat the development of the ' ' cocco- 
 liths " from a diameter of 7-Airth of an inch up to their largest 
 
 vol/. VIII C 
 
18 ON A PIECE OF 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 GlohigerincB ; 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 afforded 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 Globigerinco 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 
 negative justification from the fact that no other 
 hypothesis 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 Glohigerinm, and other simple 
 organisms, imbedded in granular matter. Here 
 and there, however, this hardened mud of the 
 
 size (which is about Tc^nnsth), and no longer doubt that they 
 are produced by independent organisms, which, like the Globi- 
 gerince, live and die at the bottom of the sea, 
 
I ON A PIECE OF CHALK 19 
 
 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 shells behind them, in the mud of the 
 present 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 Nautihts, 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 the 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 
 
 c 2 
 
20 ON A PIKCE OF CHALK I 
 
 one of them inhabited fresh water — the collateral 
 evidence that the chalk represents an ancient sea- 
 bottom acquires as great force as the proof 
 derived 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, Russia, 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 
 hundredth of an inch in diameter to heap up 
 such a mass as that. I have said that through- 
 out the thickness of the chalk the remains of 
 other animals 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 remain in their places. In a word, it is 
 certain that these animals have lived and died 
 
1 ON A PIECE OF CHALK 21 
 
 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 Glohigerina mud, upon which the 
 creatures imbedded 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 
 assuredly 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 Glohigerina 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 happened, another animal might attach itself 
 to the dead and naked skeleton, might giow 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. 
 
22 ON A PIECE OF CHALK I 
 
 " The upper valve is almost invariably wanting, 
 though occasionally found in a perfect state of 
 preservation in the white chalk at some distance. 
 In this case, we see clearly that the sea-urchin 
 first lived from youth to age, then died and lost 
 its spines, which were earned 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 
 Geology, in London, still further prolongs the 
 period which must have elapsed between the 
 death of the sea-urchin, and its burial by the 
 Glohigerinw. For 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, enable 
 us to deduce from such facts as these the maxi- 
 mum rat© at which the chalk can have ac- 
 cumulated, and thus to arrive at the minimum 
 
 ' EMients of Geology, by Sir Charles Lyell, Bart. F.E.S., 
 p. 23. 
 
I ON A PIECE OF CHALK 23 
 
 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 attached 
 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 coralliue 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 the coralline to 
 the full size which it has attained. If the decay 
 of the soft parts of the sea-urchin ; the attachment, 
 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 
 
24 ON A PIECE OF CHALK I 
 
 that life, the chalk period must have had a much 
 longer duration than that thus roughly assigned 
 to it. 
 
 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 cretaceous 
 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 
 denizen 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 
 savages, such as the Esquimaux are now ; that, in 
 the country which is now France, they hunted the 
 reindeer, and were famihar with the ways of the 
 mammoth and the bison. The physical geography 
 of France was in those days different from what it 
 
I ON A PIECE OF CHALK 25 
 
 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 cKmate was 
 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 which 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 reHcs of long-vanished 
 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 se.e 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 
 Norway side by side with them. 
 
26 ON A PIECE OF CHALK I 
 
 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 
 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 appro- 
 priately 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 gi-eat 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. 
 
I ON A PIECE OF CHALK 27 
 
 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 
 evidence 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 revenges " 
 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 covered 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 upheaved 
 glacial mud hardened into the soil of modern 
 Norfolk. Forests grew once more, the wolf and 
 the beaver replaced the reindeer and the elephant ; 
 and at length what we call the history of England 
 dawned. 
 
 Thus you have, within the limits of your own 
 
28 ON A PIECE OF CHALK I 
 
 county, proof that the chalk can justly claim a 
 very much greater antiquity than even the oldest 
 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 informs 
 us that Adam, immediately upon his creation, and 
 before the appearance of Eve, was placed in the 
 Garden of Eden. The problem of the geographical 
 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 com- 
 mentator 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 then- 
 upheaval 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 
 
I ON A PIECE OF CHALK 29 
 
 permitted I might indefinitely increase its quantity, 
 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. 
 
30 ON A PIECE OF CHALK I 
 
 I must ask you to believe that there is no less 
 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 
 animals, beasts of the field, fowls of the air, 
 creeping 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 
 identical 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 carried back into those times, we should 
 be as one suddenly set down in Australia before it 
 was colonized. We should see mammals, birds, 
 reptiles, fishes, insects, snails, and the like, clearly 
 
I ON A PIECE OF CHALK 31 
 
 recognizable as such, and yet not one of them 
 would be just the same as those with which we 
 are familiar, and many, would be extremely 
 different. 
 
 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 
 vanished 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 be- 
 tween 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 con- 
 nected. 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 pterodactyl, the ichthyosaurus, and 
 the plesiosaurus, which are found in no later 
 deposits, but abounded in preceding ages. The 
 
32 ON A PIECE OF CHALK I 
 
 chambered shells called ammonites and belemnites, 
 which are so characteristic of the period pre- 
 ceding the cretaceous, in like manner die with it. 
 
 But, amongst these fading remainders of a 
 previous state of things, are some very modem 
 forms of life, looking like Yankee pedlars among 
 a tribe of Red Indians. Crocodiles of modern 
 type appear; 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 hving shell-fish first 
 become known to us in the chalk. The vegetation 
 acquires a modem 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 
 present give confidently is the snake's-head lamp- 
 shell (Terebrahdina caput scrpentis), which lives in 
 our English seas and abounded (as Terebratulina 
 striata 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 
 
I ON A PIECE OF CHALK 33 
 
 Battle of Hastings. The ancestors of Terebratulina 
 cwput 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. While 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 
 farther 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 
 
 VOL. VIII D 
 
34 ON A PIECE OF CHALK I 
 
 of nature, inasmuch as they are going on at the 
 present time. Direct proof may be given, that 
 some parts of the land of the northern hemisphere 
 are at this moment insensibly rising and others 
 insensibly 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 effected by other than natural causes. Is 
 there any more reason for beheving that the con- 
 comitant modifications in the forms of the living 
 inhabitants 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 hved before 
 the chalk ; but, in the cretaceous epoch, as I have 
 already mentioned, the crocodiles had assumed 
 the modern type of structure. Notwithstand- 
 ing this, the crocodiles of the chalk are not 
 
I ON A PIECE OF CHALK 35 
 
 identically the same as those which lived in the 
 times called " older tertiary," which succeeded the 
 cretaceous epoch ; and the crocodiles of the older 
 tertiaries are not identical with those of the 
 newer tertiaries, nor are these identical with 
 existing forms. I leave open the question whether 
 particular species 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 stnictural 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 pro- 
 ceedings of the fifth and six days of the Creation. 
 
 On the other hand, I see no good reason for 
 doubting the necessary alternative, that aU these 
 varied species have been evolved from pre-existing 
 
 D 2 
 
36 ON A PIECE OF CHALK I 
 
 crocodilian forms, by the operation of causes 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 no- 
 wise brilliant, thought to-night. It has become 
 luminous, 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 
 observed nothing but the natural product of the 
 forces originally possessed by the substance of the 
 universe. 
 
II 
 
 THE PROBLEMS OF THE DEEP SEA 
 
 [1873] 
 
 On the 21st of December, 1872, H.M.S. Challenger, &i^ 
 eighteen gun corvette, of 2,000 tons burden, 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 remote 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 photo- 
 meters and for thermometers, filled the space 
 formerly occupied by guns and gun-tackle, pistols 
 and cutlasses. 
 
38 THE PEOBLEMS OP THE DEEP SEA II 
 
 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 
 ship, and, if need be, fight her as seamen should ; 
 while there is a staff of scientific civilians, under 
 the general direction of Dr. Wjrville Thomson, 
 F.E.S. (Professor of Natural History in Edinburgh 
 University by rights, but at present detached for 
 duty in partibus), whose business it is to turn all 
 the wonderfully packed stores of appliances to 
 account, and to accumulate, before the ship returns 
 to England, such additions to natural knowledge 
 as shall justify the labour and cost involved in the 
 fitting out and maintenance of the expedition. 
 
 Under the able and zealous superintendence of 
 the Hydrographer, Admiral Richards, 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 dispatch 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- 
 
II THE PROBLEMS OF THE DEEP SEA 39 
 
 trated volume entitled " The Depths of the Sea," 
 published since his departure. 
 
 " In the spring of the year 1868, my friend Dr. "W. B. Car- 
 penter, 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 conviction 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 
 hottom 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 Islands. I 
 propounded my views to my fellow-labourer, and we discussed 
 the subject many times over our microscopes. I strongly urged 
 Dr. Carpenter to use his influence at head-quai-tei's to induce the 
 Admiralty, probably through the Council of the Royal Society, 
 to give us the use of a vessel properly fitted with dredging gear 
 and all necessary scientific apparatus, 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 i)romised his hearty co- 
 operation, and we agreed that I should write to him on his 
 return to London, indicating generally the results which I an- 
 ticipated, 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 eminently satisfactoiy correspondence which led 
 to the Admiralty placing at the disposal of Dr. Carpenter and 
 myself the gunboat Lightning, under the command of Staff- 
 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 association of Mr. Gwyn 
 Jeffreys, in the summers of the 3'oars 1869 and 1870." ^ 
 
 1 The Depths of the Sea, pp. 49-50. 
 
40 THE PROBLEMS OF THE DEEP SEA II 
 
 Plain men may be puzzled to understand why 
 Dr. Wyville Thomson, not being a cynic, should 
 relegate the " Land of Promise " to the bottom of 
 the deep sea ; they may still more wonder what 
 mamaer of " milk and honey " the Challenger 
 expects to find; and their perplexity may well 
 rise to its maximum, when they seek to divine the 
 manner in which that milk and honey are to be 
 got out of so inaccessible a Canaan. I will, there- 
 fore, endeavour 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- 
 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 
 
II THE PROBLEMS OF THE DEEP SEA 41 
 
 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 oysters, 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 
 laborious. 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 ,1 and of the contrivances known as " accumu- 
 lators," to diminish the risk of snapping the dredge 
 rope by the rolUng and pitching of the vessel, the 
 dredge has been worked deeper and deeper, until 
 at last, on the 22nd of July, 1869, H.M.S. Porcupine 
 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 
 
 ' The emotional side of the scientific nature has its singi^lari- 
 ties. Many per.sons will call to mind a certain philosopher's 
 tenderness over his watch — "the little creature" — 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 oversti-ained, and then we pitied the 
 mlling little thing, panting like an overtaxed horse. " 
 
42 THE PROBLEMS OF THE DEEP SEA n 
 
 nearly equal to the height of Mont Blanc. The 
 dredge " was rapidly hauled on deck at one o'clock 
 in the morning of the 23rd, after an absence of 
 7| 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 gumett. 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 fi:om 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. 
 
 More than a thousand sail of well-found trawlers 
 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 difiiculty of trawling, Hke that of 
 
II THE PROBLEMS OF THE DEEP SEA 43 
 
 dredging, rapidly increases with the depth at 
 which the operation is performed ; and, until the 
 other day, it is probable that trawHng 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. WyviUe Thomson writes (" Nature," March 
 20, 1873) :— 
 
 "For the firet two or three hauls in veiy deep water off the 
 coast of Portugal, the dredge came up filled with the usual 
 'Atlantic ooze,' tenacious and uniform throughout, 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 distiibution of 
 the higher groups ; and after various suggestions for modification 
 of the dredge, it was proposed to try the oi-dinary 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 gi'eat satisfaction, 
 the trawl came up all right and contained, 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 
 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 netted 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 
 
44 THE PROBLEMS OF THE DEEP SEA n 
 
 off the coral, which is brought up entangled in the 
 cords. A similar contrivance has arisen out of the 
 necessities 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 
 devised an arrangement not unlike that employed 
 by the coral-fishers. He fastened half a dozen 
 swabs, such as are used for dr3dng 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 en- 
 tangled the creatures living there — ^multitudes of 
 which, twisted up in the strands of the swabs, 
 were brought to the surface with the dredge. A 
 further improvement was made by attaching a 
 long iron bar to the bottom of the dredge bag, and 
 fastening large bunches of teased-out hemp to the 
 end of this bar. These "tangles" bring up 
 immense quantities of such animals as have long 
 arms, or spines, or prominences which readily 
 become caught in the hemp, but they are very 
 destructive to the fragile organisms which they 
 
II THE PROBLEMS OF THE DEEP SEA 45 
 
 imprison ; and, now that the trawl can be success- 
 fully worked at the greatest depths, it may be 
 expected to supersede them ; at least, wherever 
 the ground is soft enough to permit of trawHng. 
 
 It is obvious that between the dredge, the trawl, 
 and the tangles, there is Kttle 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 Clmllenger undertakes to 
 explore. And, for the first time in the history of 
 scientific exploration, we have a fair chance of learn- 
 ing 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 modem branch of Biolo- 
 gical Science, and came into existence long after 
 Morphology and Physiology had attained a con- 
 siderable development. This naturally does not 
 imply that, fi'om 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 fi'om those in other regions ; or 
 that those of the hills are different firom 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. Never- 
 theless, it was only after the discovery of America 
 
46 THE PROBLEMS OF THE DEEP SEA n 
 
 that the attention of naturahsts was powerfully 
 drawn to the wonderful differences between the 
 animal population of the central and southern 
 parts of the new woi:ld 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 
 populorum," argues that, since there are innumer- 
 able species of animals in America which do not 
 exist elsewhere, they must have been made and 
 placed there by the Deity : Buffon no less forcibly 
 insists 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 Zoologiae 
 Geographicae Quadrupedum Doifticilia et Migra- 
 tiones sistens," published, in 1777, by the learned 
 Brunswick Professor, Eberhard Zimmermann, who 
 illustrates his work by what he calls a " Tabula 
 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 
 mammals, 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. 
 
II THE PROBLEMS OF THE DEEP SEA 47 
 
 he thinks, obey no such law. The Arctic and 
 Atlantic seas, he says, are as full of fishes and 
 other animals as those of the tropics. It is, there- 
 fore, clear that cold does not affect the dwellers 
 in the sea as it does land animals, and that this 
 inust be the case follows from the fact that sea 
 water, "propter varias quas continet bituminis 
 spiritusque particulas," fi-eezes with much more 
 difficulty 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, according to Zimmermann, the incessant 
 disturbance of the mass of the sea by winds and 
 tides, so mixes up the warm and the cold that 
 hfe is evenly diffused and abundant throughout 
 the ocean. 
 
 In 1810, Risso, in his work on the Ichthyology 
 of Nice, laid the foundation of what has since been 
 termed '' bathymetrical " 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 
 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 
 
48 THE PROBLEMS OF THE DEEP SEA n 
 
 Milne Edwards carried out the principle of distin- 
 guishing the Faunae of different zones of depth 
 much more minutely, in their " Eecherches pour 
 servir k I'Histoire NatureUe du Littoral de la 
 France," pubhshed in 1832. 
 
 They divide the area included between high- 
 water-mark and lowwater-mark 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, 
 scallops, and large starfishes and other animals. 
 Beyond this they seem to think that animal life 
 is absent.^ 
 
 Audouin and Milne Edwards were the first to 
 see the importance of the bearing of a knowledge 
 of the manner in which marine animals are 
 distributed in depth, on geology. They suggest 
 that, by this means, it wiU be 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 
 
 ^ ' ' Enfin plus bas encore, c'est-k-dire alors loin des c8tes, le 
 fond des eaux ne paralt plus gtre habite, du moins dans nos 
 mers, par auciin de ces animaux" (1. c. torn. i. p. 237). The 
 " ces animaux " leaves the meaning of the authors doubtful. 
 
H THE PROBLEMS OF THE DEEP SEA 49 
 
 prove that the shells have been transported into 
 the position 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 in- 
 habitants, inasmuch 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 
 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 
 bringing the importance of distribution in depth 
 into notice ; and his researches in the JEgean Sea, 
 
 ^ In the paper in the Memoirs of the Survey cited further on, 
 Forbes writes ; — 
 
 "In an essay 'On the Association of MoUusca on the 
 British Coasts, considered with reference to Pleistocene 
 Geology,' printed in [the Edinburgh Academic AnmiMlior] 1840, 
 I described the molhisca, as distributed on our shores and seas, 
 in four great zones or regions, usually denominated ' The Lit- 
 toral Zone,' 'The region of Laminarias, ' 'The region of Coral- 
 lines,' and 'The region of Coials.' An extensive series of 
 researches, chiefly conducted 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, in the 
 Norwegian and Lapland seas, have borne out their correctness. 
 The first two of the regions above mentioned had been previ- 
 ously 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 Iris Bcshrivelser og Jagttagelser." 
 
 VOL. VIII E 
 
50 THE PROBLEMS OF THE DEEP SEA II 
 
 and still more his remarkable paper " On the Geo- 
 logical Relations 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 
 lowwater-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 Mgean 
 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 diminished ; 
 until, beyond 300 fathoms, life disappeared alto- 
 gether. Hence it appeared as if descent in the 
 sea had much the same effect on life, as ascent 
 on land. Recent 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 Mgean ; and though, at the 
 time he wrote, one or two observations were 
 extant which might have warned him not to 
 generalize too extensively from his ^gean ex- 
 perience, 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. Never- 
 
II THE PROBLEMS OF THE DEEP SEA 51 
 
 theless, so far as the limit of the range of life in 
 depth goes, Forbes' conclusion has been completely 
 negatived, and the greatest depths yet attained 
 show not even an approach to a " zero of life " : — 
 
 "During the several cruises of H.M. ships Lightning and 
 Pormpiiie 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 characteiistic examples of all the five 
 invertebrate sub-kingdoms. And thus the question of the 
 existence 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 between three and 
 four thousand fathoms ; and if there be nothing in the condi- 
 tions of a depth of 2,500 fathoms to prevent the full develop- 
 ment of a varied Fauna, it is impossible 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 light a still greater diversity of life. 
 
 Fishes came up from a depth of 600 to more than 
 
 ' The Depths of the Sea, p. 30. Kesults of a similar kind, 
 obtained by previous observere, are stated at length in the sixth 
 chapter, pp. 267-280. The dredgings earned out by Count 
 Pourtales, under the authority of Professor Peirce, the Super- 
 intendent of the United States Coast Survey, in the years 
 1867, 1868, and 1869, are particularly 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 aud 
 comprehensive basis for an exploration of the sea bottom on a 
 large scale, opening a new era in zoological and geological 
 research. " 
 
 E 2 
 
52 THE PROBLEMS OF THE DEEP SEA ii 
 
 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." 
 Bivalve and univalve moUusca seem to be rare at 
 the greatest depths; but starfishes, sea urchins, 
 and other echinoderms, zoophytes, sponges, and 
 protozoa abound. 
 
 It is obvious that the Gliallengcr has the 
 privilege 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 
 depth, in that particular latitude and longitude, 
 will be a new fact in distribution, and, as such, 
 have a certain importance. 
 
 But it may be confidently assumed that the 
 things brought up will very frequently be zoo- 
 logical novelties; or, better still, zoological 
 antiquities, which, in the tranquil and little- 
 changed depths of the ocean, have escaped the 
 causes of destruction at work in the shallows, and 
 represent 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- 
 
II THE PEOBLEMS OF THE DEEP SEA 53 
 
 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 areae, 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 
 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 
 explain 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 
 
54 THE PROBLEMS OF THE DEEP SEA ii 
 
 as are now to be met with only in the Scandinavian, 
 or still more Arctic, regions. Undoubtedly, during 
 the glacial epoch, the general population of our 
 seas had, universally, the northern aspect which 
 is now presented only by the " northern outliers "; 
 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 away, 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 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 effect upon distribution to height on the 
 land. 
 
 The same idea is applied to the explanation of 
 a similar anomaly in the Fauna of the Mgean : — 
 
 " In the deepest of the regions of depth of the Mgeaji, the 
 representation of a Northern 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 
 
II THE PROBLEMS OF THE DEEP SEA 55 
 
 epoch was doubtless the newer Pliocene or Glacial Era, when the 
 Mya truncata and other northern forms now extinct in the 
 Mediteri'anean, 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 living 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 in Scotland against encroaching 
 Teutons, thus broached by Forbes, received a 
 ■ wider application than Forbes had dreamed of 
 when the sounding machine first brought up 
 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 Gldbigeriiia 
 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 Glohigcrina 
 
 ' Memoirs of the Geological Survey of Great Britain, Vol. i. 
 p. 390. 
 
 ' See above, "On a Piece of Chalk,'' p. 13. 
 
56 THE PROBLEMS OF THE DEEP SEA n 
 
 and the Coccoliths should not be the only sur- 
 Tivors of a world passed away, which are hidden 
 beneath three miles of salt water? The letter 
 which Dr. W)rville Thomson wrote to Dr. Car- 
 penter in May, 1868, out of which aU 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 
 solving the problem is put in the foreground of 
 his reasons for urging the Government to under- 
 take the work of exploration : — 
 
 " Two years ago, M. Sars, Swedish GoTemment Ii^ertw of 
 Fisheries, had an opportnnity, in his ofBeial capacity, of dredg- 
 ing off the Loffoten Islands at a depth of 300 fathoms. I 
 visited Norway shortly after his return, and had an opportnnity 
 of studying with his father, Professor Sars, some of bis results. 
 Animal forms were 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 Encrinites of the Jurassic period, and whose latest 
 representative hitherto known was the Sourgiicttocrimis of the 
 chalk. Some years previously, Mr. Ahsjomsen, dredging in 200 
 fathoms in the Hardangerfjord, procured several examples of » 
 Starfish [Brisinga), 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 ocean at depths 
 varying from 200 to 300 fathoms, that the forms at these great 
 depths differ greatly from those met with in ordinary dredgings, 
 and that, at all events in some cases, 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 antici- 
 
II THE PROBLEMS OF THE DEEP SEA 57 
 
 pated ; and, probably, further investigation will largely add to 
 this class of data, and will give us an opportunity of testing 
 our determinations of the zoological position of some fossil 
 types by an examination of the soft parts of their recent 
 representatives. The main cause of the destruction, the migra- 
 tion, and the extreme modification of animal types, appear 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 
 beyond 1,000 feet since the commencement of the Tertiary 
 Epoch. The temperature of deep waters seems to be constant 
 for all latitudes at 39° ; so that an immense area of the North 
 Atlantic must have had its conditions unaffected by tertiary or 
 post-tertiary oscillations. " ' 
 
 As we shall see, the assumption that the tem- 
 perature of the deep sea is everjTvhere 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 expectation 
 has been, to some extent, aheady verified. 
 
 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 locali- 
 ties, are innumerable cup-shaped sponges, pro- 
 vided with six-rayed sihcious 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 
 
 1 TTie Depths of the Sea, pp. 51-52. 
 
58 THE PEOBLEMS OF THE DEEP SEA n 
 
 Dr. Thomson as " elegant vases or cups, with 
 branching root-hke bases, or groups of regularly 
 or irregularly spreading tubes delicately fretted 
 on the surface with an impressed network like 
 the finest lace " ; and he adds, " When we com- 
 pare such recent forms as Aphrocallistes, Fphiteon, 
 Holtenia, and Askonema, 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 allied genera." ^ 
 
 Professor Duncan finds " several corals from 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 
 general 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 approach 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, 
 
 1 The Depths of the Sea, p. 484. 
 
II THE PROBLEMS OF THE DEEP SEA 59 
 
 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 teacup- 
 fuls as the Caspian, the Black Sea, and the 
 Mediterranean; the supposition of Dr. Thomson 
 and Dr. Carpenter that what is now the deep 
 Atlantic, was the deep Atlantic (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 probability. And 
 I agree with Dr. Wyville Thomson against Sir 
 Charles Lyell (it takes two of us to have any 
 chance against his authority) in demurring to the 
 assertion that " to talk of chalk having been 
 uninterruptedly formed in the Atlantic is as 
 inadmissible in a geographical as in a geological 
 sense." 
 
 If the word " chalk " is to be used as a 
 stratigraphical 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 modem and the ancient 
 chalks are to be separated — and, looking at the 
 matter geographically, I see no reason to doubt 
 that a boring rod driven from the surface of the 
 mud which forms the floor of the mid- Atlantic 
 
60 THE PEOBLEMS OF THE DEEP SEA II 
 
 would pass through one continuous mass of 
 Globigerina mud, first of modern, then of tertiary, 
 and then of mesozoic date; the "chalks" of 
 different depths and ages being distinguished 
 merely by the different forms of other organisms 
 associated with the Glohigerince. 
 
 On the other hand, I think it must be admitted 
 that a belief in the continuity of the modem 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 
 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 discovered in the deep sea, the modem types 
 associated 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 carrjdng out the 
 work already commenced by the Lightning and 
 
II THE PKOBLEMS OF THE DEEP SEA 61 
 
 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 
 phenomena 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} 
 and some data of fundamental importance to the 
 physical geography of the sea have been fixed 
 beyond 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 eiToneous con- 
 clusions deduced from their eiToneous premises 
 have been widely accepted as if they were 
 ascertained facts. Of course, if sea-water, like 
 fresh water, were heaviest at a temperature of 
 39° F. and got lighter as it approached 32° 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 
 1 Proceedings of the Boyal Society, 1870 and 1872 
 
62 THE PROBLEMS OF THE DEEP SEA n 
 
 at dilEferent depths, by means of thermometers 
 specially contrived for the avoidance of the errors 
 produced 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- 
 ture at the bottom, at a depth of 2270 to 2656 
 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 
 return 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 
 
II THE PROBLEMS OF THE DEEP SEA 63 
 
 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 currents, 
 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, but 
 south-westerly in the northern hemisphere, and 
 north-westerly in the southern ; while, by a parity 
 of reasoning, the equatorial-polar warm currents 
 would be north-easterly in the northern hemi- 
 sphere, 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 
 coincide with that of the anti-trade winds. The 
 freezing of the surface of the polar sea would not 
 interfere 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. 
 
64 THE PROBLEMS OF THE DEEP SEA ii 
 
 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 
 off from the influence of the cold polar underflow, 
 the temperature of its deeps should be less cold 
 than the temperature of corresponding depths in 
 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. Eoughly 
 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 1,200 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 .^gean Seas. The 
 western pool is less deep, though it reaches some 
 10,000 feet. And, just as the western end of the 
 
II THE PROBLEMS OF THE DEEP SEA 65 
 
 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 off 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?. 
 Everywhere below 600 feet it is about 55° Fahr. ; 
 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 
 
 VOL. VIII F 
 
66 THE PROBLEMS OF THE DEEP SEA li 
 
 upon this complicated problem ; but I may take 
 occasion to remark that the cause of a much 
 simpler phenomenon— =the stream of Atlantic 
 water which sets through the Straits of Gibraltar, 
 eastward, 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 shghtly denser than that of 
 the Atlantic (1-0278 to 1-0265), and that the deep 
 water of the Mediterranean is slightly denser than 
 that of the surface ; while the deep water of the 
 Atlantic is, if anything, lighter than that of the 
 surface. Moreover, while a rapid superficial cur- 
 rent is setting in (always, save in exceptionally 
 violent easterly winds) through the Straits of 
 Gibraltar, 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. Carpenter 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, 
 
II THE PROBLEMS OF THE DEEP SEA 67 
 
 is much greater than that from the Atlantic 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 answered affirm- 
 atively : Are not these sources of loss in the 
 Mediterranean fuUy covered by the prodigious 
 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 ; 
 that the volume 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 Mediten-anean, 
 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. 
 
 F 2 
 
68 THE PROBLEMS OF THE DEEP SEA n 
 
 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 
 comfort. 
 
 The Mediterranean is not included in the 
 Challenger's route, but she will visit one of the 
 most promising and little explored of hydro- 
 graphical regions — the North Pacific, between 
 Polynesia and the Asiatic and American shores ; 
 and doubtless the store of observations upon the 
 currents of this region, which she will accumulate, 
 when compared with what we know of the North 
 Atlantic, will throw a powerful light upon the 
 present obscurity of the Gulf-stream problem. 
 
Ill 
 
 ON SOME OF THE EESULTS OF THE 
 EXPEDITION OF H.M.S. GHAZLENGEB 
 
 [1875] 
 
 In May, 1873, I drew attention ^ to the im- 
 portant problems connected with the physics 
 and natural history of the sea, to the solu- 
 tion 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 disappointed. Reports to 
 the Admiralty, papers communicated to the Royal 
 Society, and large collections which have already 
 been sent home, have shown that the Challenger's 
 staff have made admirable use of their sTeat 
 opportunities ; and that, on the return of the 
 expedition in 1874, their performance will be fully 
 up to the level of their promise. Indeed, I am 
 disposed to go so far as to saj', that if nothing 
 more came of the Challenger's expedition than 
 
 ' Sec tho preceding Essay. 
 
70 EXPEDITION OF THE "CHALLENGER" m 
 
 has hitherto been yielded by her exploration of 
 the nature of the sea bottom at great depths, a 
 full scientific equivalent of the trouble and ex- 
 pense 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 WyviUe 
 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, 
 1872, and what new facts have been added by the 
 scientific staff of the ChMllenger. So far as I have 
 been able to discover, the first successful attempt 
 to bring up from gi'eat depths more of the sea 
 bottom than would adhere to a sounding-lead, was 
 made by Sir John Ross, in the voyage to the 
 Arctic regions which he undertook in 1818. In 
 the Appendix to the narrative of that voyage, 
 there will be found an account of a very ingenious 
 apparatus 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 Baffin'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 Ross on this cmise, says of 
 this mud that it was " soft and greenish, and that 
 
Ill EXPEDITION OP THE "CHALLENGER" 71 
 
 the lead sunk several feet into it." A similar 
 " fine green mud " was found to compose the sea 
 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 Assistance 
 Bay, in Kingston Bay, and in MelviUe Bay, 
 which lie between 73° 45' and 74° 40' N., 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 
 Ehrenberg, 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 
 silicious skeletons of those low animal organisms, 
 which were termed Polycistinem by Ehrenberg, but 
 are now known as Radiolaria. 
 
 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. Lieutenant Brooke, of the United 
 States Navy, who was employed in surveying the 
 
 ^ Ueber ncue Ansclmuuiiqen des Tdeiiisten nordlichcn Polar- 
 ?ci(!)is.— Monatsljerichte d. K. Akad. Berlin, 1853. 
 
72 EXPEDITION OF THE "CHALLENGER" III 
 
 Sea of Kamschatka, had succeeded in obtaining 
 specimens of the sea bottom from greater depths 
 than any hitherto reached, namely from 2,700 
 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 microscopically, 
 Professor Bailey found, as Ehrenberg 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 Biatomacm, of spicula 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 Ross 
 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 Eoss was himself a naturalist of no 
 mean acquirements, and Dr. Hooker,^ the present 
 President of the Royal 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 
 
 1 rNow Sir Joseiih Hooker. 1894.] 
 
Ill EXPEDITION OF THE " CHALLENGEE " 73 
 
 attention of the voyagers been particularly directed 
 to the importance of noting the occurrence of the 
 minutest forms of animal and vegetable life in the 
 ocean. 
 
 Among the scientific instructions for the voyage 
 drawn up by a committee of the Eoyal 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 " Tripoh " 
 which occur in various parts of the world, and 
 notably at Bilin in Bohemia, consisted of accumu- 
 lations of the silicious cases and skeletons of Diato- 
 macem, sponges, and Badiolaria ; he had proved 
 that similar deposits were being formed by 
 Diatomacece, in the pools of the Thiergarten in 
 Berhn 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 
 
74 EXPEDITION OF THE " CHALLENGER " m 
 
 a fossil state, constitute extensive rocks of tertiary 
 age at Caltanisetta, Zante, and Oran, on the 
 shores of the Mediterranean. 
 
 Moreover, in the fresh-water rotten-stone beds 
 of Bilin, Ehrenberg 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 
 skeleton, becomes converted into a dense opaline 
 stone, with only here and there an indication of an 
 organism. 
 
 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.^ 
 
 ' Vcbcr die noch jetzf zahlrcich Ubende Thierarien der Kreide- 
 bildung und den Organismus der Polylhalamien. AbhandluTigen 
 der Kon. Alead. der JJ'issencJiaften. 1839. Berlin. 1841. I am 
 afvaid that thLs remarkable paper has been somewhat overlooked 
 in the recent discussions of the relation of ancient rocks to 
 modem deposits. 
 
Ill EXPEDITION OF THE " CHALLENGER " 75 
 
 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 
 before the British Association in 1847, are of the 
 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 Viatomaceoe. Though much too small to be discernible 
 by the naked eye, they occui-red 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 universally 
 present, generally eludes the search of the naturalist; 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 Alg£e are examined. To 
 the south, however, of the belt of ice which encircles the globe, 
 between the parallels of 50° and 70° S., and in the watera 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 eveiy 
 berg, and the base of the great Victoria Barrier itself, within 
 reach of the swell, were tinged brown, as if the polar waters 
 wore charged with oxide of iron. 
 
 "As the majority of these plants consist of very simple vege- 
 table cells, enclosed in indestructible silex (as other Alga; are in 
 carbonate of lime), it is obvious that the death and decomposi- 
 
76 EXPEDITION OF THE "CHALLENGER HI 
 
 tion of such multitudes must form sedimentary deposits, propor- 
 tionate 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 eveiy icebound shore, in the depths 
 of the adjacent ocean, between 80 and 400 fathoms.. Off 
 Victoria Barrier (a pei'pendicular 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 pi-incipally of the silicious shells of the Diaiomaceai. 
 These, on being put into water, rendered it cloudy like milk, 
 and took many hours to subside. In the very deep water oft 
 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 disintegrated rock and sand ; so that the 
 organic compounds of the bottom frequently bore but a small 
 proportion to the inorganic." . . . 
 
 " The universal existence of such an invisible vegetation as 
 that of the Antarctic Ocean, is a tmly 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 MoUtisca, and 
 particularly entomostracous Cntstacca, small whales, and por- 
 poises ; 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 recog- 
 nised, because feeding 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 Dialomaceoc with 
 plants, probably maintaining in the South Polar Ocean that 
 balance between the vegetable and the animal kingdoms which 
 prevails over the surface of our globe. Nor is the su.stenance 
 and nutritioii of the animal Icingdom the only function these 
 
Ill EXPEDITION OF THE " CHALLENGER " 77 
 
 minute productions may perfonn ; they may also be the purifiers 
 of the vitiated atmosphere, and thus execute in the Antarctic 
 latitudes the office of our trees and gi'ass turf in the temperate 
 regions, and the broad leaves of the jialm, &o., in the 
 tropics." .... 
 
 With respect to the distribution of the 
 Biatomaccw, Dr. Hooker remarks : — 
 
 " There is probably no latitude between that of Spitzbergen 
 and Victoria Land, where some of the species of either country 
 do not exist : Iceland, Britain, the Mediterranean Sea, North and 
 South America, and the South Sea Islands, all possess Antarctic 
 Diatomacece. The silicious coats of species only known living 
 in the waters of the South Polar Ocean, have, during past 
 ages, contributed to the formation of rocks ; and thus they out- 
 live several successive creations of organized beings. The 
 phonolite stones of the Khine, and the Tripoli stone, contain 
 species identical with what are now contributing to form a sedi- 
 mentary deposit (and perhaps, at some future period, a bed of 
 rock) extending in one continuous stratum for 400 measured 
 miles. I allude to the shores of the Victoria Bai-rier, along 
 whose coast the soundings examined were invariably charged 
 with diatomaceous remains, constituting a bank which stretches 
 200 miles north from the base of Victoria Bamer, while the 
 average depth of water above it is 300 fathoms, or 1, 800 feet. 
 Again, some of the Antarctic species have 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 Diatoinacece, 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 
 
78 EXPEDITION OF THE " CHALLENGER " m 
 
 (and amongst them some Antarctic ones) in the volcanic ashes, 
 pumice, and scoriae of active and extinct volcanoes (those of the 
 Mediterranean Sea and Ascension Island, for instance) is a fact 
 hearing immediately upon the present subject. Mount Erebus, 
 a volcano 12,400 feet high, of the first class in dimensions and 
 energetic action, rises at once from the ocean in the seventy- 
 eighth degree of south latitude, and abreast of the Diatomacem 
 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 
 ciuter, so the subterranean and subaqueous forces which maintain 
 Mount Erebus in activity may occasionally receive organic 
 matter 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 otDiatom- 
 acece. 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 and Barrier, and the sea and ice as full of Diatomaceie, 
 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 accumulation 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 
 colleagues in every respect confirm those of Dr. 
 Hooker : — 
 
 " On the 11th of February, lat. 60° 62' S., long. 80° 20' E., 
 and March 3, lat. 53° 55' S., long. 108° 35' E., the sounding 
 
Ill EXPEDITION OF THE "CHALLENGER" 79 
 
 instrument came up filled with a very fine cream-coloured paste, 
 which scarcely effervesced with acid, and dried into a very light, 
 impalpable, white powder. 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 Fragil- 
 laria, C'oscinodisiytis, Choetoceros, Asteromphahis, 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 Globigeri'iue, 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., 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 species as those found at the bottom. By far the 
 most abundant was the little bundle of silicious 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 endochromo 
 of the Diatomacece. Like the GloMgerina ooze, then, which it 
 succeeds to the southward in a band apparently of no great 
 width, the materials of this silicious deposit are derived entirely 
 from the surface and intermediate depths. It is somewhat 
 singular that Diatoms did not appear to be in such large num- 
 bers oh the surface over the Diatom ooze as they were a little 
 further north. This may perhaps be accounted 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 Febniary the bottom 
 deposit was really shifted a little to the south by the warm 
 current, the excessively fine flocculent debris of the Diatoms 
 taking a certain time to sink. The belt of Diatom ooze is 
 certainly a little further to the southward in long. 83° E., in 
 
80 EXPEDITION OF THE " CHALLENGER " m 
 
 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 grayish mud, with small pebbles of 
 quartz and felspar, and small fragments of mioa-slate, chlorite- 
 slate, clay-slate, gneiss, and granite. This deposit, I have no 
 doubt, was derived from the surface like the othere, but in this 
 case by the melting of icebergs and the precipitation of foreign 
 matter contained in the ice. 
 
 ' ' We never saw any trace of gravel or sand, or any material 
 necessarily derived from land, on an iceberg. Several showed 
 vertical or iiTegular 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 material filling the fissure reflecting light less per- 
 fectly than the general surface of the berg. I conceive that 
 the upper suiface of one of these great tabular southern ice- 
 bergs, including by far the gi'eater part of its bulk, and culmin- 
 ating 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 slowly 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 off and floated 
 away. If this be the true history of the formation of these 
 icebergs, the absence of all land lUiris 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 
 
Ill EXPEDITION OF THE "CHALLENGER" 81 
 
 rising, and it is rapidly melted, and the mud and pebbles witli 
 which it is more or less charged are precipitated. That this 
 precipitation take's 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 being entirely composed of such 
 deposits ; for the Diatoms, Globigeriiue, and radiolarians 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 south 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 ddbris 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 
 animals which throng the surface, and, in part, 
 from the spicula of sponges which live at the 
 bottom. The evidence respecting the correspond- 
 ing 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 particles 
 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 freshwater 
 deposits of this kind, it is certain that the action 
 
 VOL. vin G 
 
82 EXPEDITION OF THE " CHALLENGER " III 
 
 of percolating water, may convert the originally 
 soft and friable, fine-grained sandstone into a 
 dense, semi-transparent opaline stone, the silicious 
 organized skeletons being dissolved, and the silex 
 re-deposited in an amorphous state. Whether 
 such a metamorphosis as this occurs in submarine 
 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 different from that of the circumpolar 
 regions. 
 
 The first exact information respecting the 
 nature of this mud at depths greater than 1,000 
 fathoms was given by Ehrenberg, in the account 
 which he published in the " Monatsberichte " of 
 
Ill EXPEDITION OF THE " CHALLENGER " 83 
 
 the Berlin Academy for the year 1853, of the 
 .soundings obtained by Lieut. Berryman, of the 
 United States Navy, in the North Atlantic, 
 between Newfoundland and the Azores. 
 
 Observations which confirm those of Ehrenberg 
 in aU essential respects have been made by 
 Professor Bailey, myself, Dr. Wallich, Dr. Car- 
 penter, 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 lati- 
 tudes, the number and variety of the Foraminifera 
 diminishes, and even the Glohigerince become 
 dwarfed. And this result, it will be observed, is 
 in entire accordance with the fact already men- 
 tioned that, in the sea of Kamschatka, the deep- 
 sea mud was found by Bailey to contain no cal- 
 careous 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, Badiolaria, 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 
 
 G 2 
 
84 EXPEDITION OF THE " CHALLENGER " ill 
 
 kind of rock, which was first pointed out by 
 Ehrenberg/ is now admitted on all hands ; nor 
 can 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 gi-anted 
 that the Globigerinm 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 
 
 ^ The following passages in Elirenberg's memoir on Tlui 
 Organisms in the Chalk which are still living (1839), are con- 
 clusive : — 
 
 ' ' 7. The dawning period of the existing living organic creation, 
 if such a period is distinguishable (which is doubtful), can only 
 be supposed to have existed on the other side of, and below, the 
 chalk foi-mation ; and thus, either the chalk, with its wide- 
 spread and thick beds, must enter into the series of newer 
 formations ; or some of the accepted four great geological periods, 
 the quaternary, tertiary, and secondary formations, contain 
 organisms which still live. It is more probable, in the propor- 
 tion of 3 to 1, that the transition or primary period is not 
 different, but that it is only more difficult to examine and 
 understand, by reason of the gradual and prolonged chemical 
 decomposition and metamoi-phosis of many of its organic 
 constituents. " 
 
 "10. By the mass-forming Infusoria and Polythalamia, 
 secondary are not distinguishable from tertiary formations ; 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 constitution 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. " 
 
Ill EXPEDITION OF THE " CHALLENGER " 85 
 
 evidence for and against this conclusion appeared 
 to me to be insuflScient to warrant a positive con- 
 clusion one way or the other, and I expressed 
 myself in my report to the Admiralty on Captain 
 Dayman's soundings 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 organ- 
 isms derived ? hecomes one of high scientific interest. 
 
 "Three answers have suggested themselves : — • 
 
 "In accordance with the prevalent view of the limitation 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 hahitually 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 Glohigeriiue been drifted into their present position 
 from shallow water, we should find a very large proportion of 
 the characteristic inhabitants of shallow watei-s mixed with 
 them, and this would the more certainly be the case, as the 
 large GloUgerince, so abundant in the deep-sea soundings, are, 
 in proportion to their size, more solid and massive than almost 
 any other Foraminifera. But the fact is that the proportion of 
 other Foraminifera 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 shallow 
 waters, and are quite as likely to be drifted as the heavy OloM- 
 gerince. Again, the relative proportions of young and fully 
 formed Gloiigerince seem inconsistent with the notion that they 
 have travelled far. And it seems difficult to imagine why, had 
 the deposit been accumulated in this way, Coscinodisci should 
 so almost entirely represent the Diatmnacea:. 
 
 "2. The second hypothesis is far more feasible, and is 
 strongly supported by the fact that many Pohjcistineoe. [Eadiola- 
 
86 EXPEDITION OF THE " CHALLENGER " iii 
 
 ria] and Coscinodisci are well known to live at the sui'face of the 
 ocean. Mr. Macdonald, Assistant-Surg«on of H.M.S. Herald, 
 now in the South-Western Pacific, has lately sent home some 
 veiy valuable observations on living forms of this kind, met 
 with in the stomachs of oceanic moUusks, and therefore cei'tainly 
 inhabitants 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 Globigerina, and there are some 
 peculiarities about even this which make me gi'eatly doubt its 
 affinity with that genus. The form, indeed, is not unlike 
 that of a Globigerina, but it is provided with long radiating 
 processes, of which I have never seen any trace in Globigerina. 
 Did they exist, they might explain what otherwise is a great 
 objection 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 conceived to exist 
 under such conditions of light, temperature, pressure, and 
 aeration as must obtain at these vast depths ? 
 
 ' ' To this one can only reply that we know for a certainty 
 that even very highly-organized animals do continue to live at 
 a depth of 300 and 400 fathoms, inasmuch as they have been 
 dredged up thence ; and that the diiference in the amount of 
 light and heat at 400 and at 2,000 fathoms is probably, so to 
 speak, very far less than the difiference in complexity of organi- 
 sation between these animals and tlie humbler Protozoa and 
 Protophyta of the deep-sea soundings. 
 
 " I confess, though as yet far from regarding it proved that 
 the Glolngerinai 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 circum- 
 stances as regards light, temperatiire, and pressure. Now, the 
 
Ill EXPEDITION OF THE " CHALLENGER " 87 
 
 genus Gloligerina 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 Gldbigcrinoi live 
 at the bottom. Dr. Wallich writes in 1862 — " By 
 sinking very fine gauze nets to considerable depths, 
 I have repeatedly satisfied myself that Gldbigerina 
 does not occur in the superficial strata of the 
 ocean." ^ Moreover, having obtained certain living 
 star-fish fi-om a depth of 1,260 fathoms, and found 
 their stomachs full of " fresh-looking Glohigerincc " 
 and their Mbris—he adduces this fact in support 
 of his belief that the Glohigerincc live at the 
 bottom. 
 
 On the other hand, MliUei", Haeckel, Major 
 Owen, Mr. Gwyn Jeffries, and other observers, 
 found that Glohigerincc, with the allied genera 
 Orhulina and Pulvinulina, sometimes occur abund- 
 antly at the surface of the sea, the shells of these 
 pelagic forms being not unfrequently 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 
 recent work of the Challenger fully confirms Major 
 Owen's statement. In the paper recently pub- 
 
 ^ Appendix to Report on Deep-sea Soundings in the Atlantic 
 Ocean, by Lieut. -Commander Joseph Dayman. 1857. 
 - The Noj-th AtlmUic Seabed, p. 137. 
 
88 EXPEDITION OF THE "CHALLENGER" iii 
 
 lished in the proceedings of the Royal Society,^ 
 from which a quotation has already been made, 
 Professor Wyrille 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 Glotigerina ooze lived on 
 the bottom, and that the occurrence of individuals on the surface 
 was accidental and exceptional ; but after going into the thing 
 carefully, and considering the mass of evidence which has been 
 accumulated 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 exception, 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 examination of the 
 soundings a constant use of the tow-net, usually 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 Oloiigerince. They are more abundant and of 
 a larger size in wanner 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 variety, the typical GloUgerina 
 hulloides, is represented. The living Oloiigerince from the tow- 
 net are singularly different in appearance from the dead shells 
 we find at the bottom. The shell is cigar 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 
 
 1 "Preliminary Notes on the Nature of the Sea-bottom pro- 
 cured 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 Hoy al Society, Nov. 26, 1874. 
 
Ill EXPEDITION OF THE "CHALLENGER 89 
 
 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 some- 
 times 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 different 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 ran together, of 
 the same yellow sarcode stuck against one side, the remainder of 
 the chamber being empty. No definite arrangement and no 
 approacTi to straeture 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, apparently irregularly, in the sarcode. Wo 
 never have been able to detect, in any of the large number of 
 Globigerince which we have examined, the least ti'ace of pseudo- 
 podia, or any extension, in any form, of the sarcode 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 arc broken off' by the slightest touch. In fresh 
 examples from the surface, the dots indicating the origin of the 
 lost spines may almost always be made out with a high power. 
 There are never spines on the Globigerince from the bottom, 
 even in the shallowest water." 
 
 There can now be no doubt, therefore, that 
 Globigerince live at the top of the sea ; but the 
 question may still be raised whether they do not 
 also hve at the bottom. In favour of this view, it 
 has been urged that the shells of the Glohigerince 
 of the surface never possess such thick walls as 
 
90 EXPEDITION OF THE " CHALLENGER" in 
 
 those which are found at the bottom, but I confess 
 that I doubt the accuracy of this statement. 
 Again, the occurrence of minute GlohigerincB 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 Salpm 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 Gldbigerina ooze, and the fact, if it be one, 
 that animals living at the bottom use them as 
 food, be considered as conclusive evidence that 
 the Globigerinw live at the bottom. Such as die 
 at the surface, and even many of those which are 
 swallowed by other animals, may retain much of 
 their protoplasmic matter when they reach the 
 depths at which the temperature sinks to 34° or 
 32° Fahrenheit, where decomposition must become 
 exceedingly slow. 
 
 Another consideration appears to me to be in 
 favour of the view that the GlobigerincB 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 
 
Ill EXPEDITION OF THE " CHALLENGER " 91 
 
 in the North Atlantic. According to Dr. Wallich 
 (" The North Atlantic Sea Bed," p. 157) Glohi- 
 gerina is the prevaHing form in the deposits 
 between 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 Glohigerince become 
 dwarfed and almost disappear between 50° and 
 55° S. On the other hand, in the sea of 
 Kamschatka, the Glohigerince have vanished in 
 56° N., so that the persistence of the Globigerina 
 ooze in high latitudes, in the North Atlantic, 
 would seem to depend on the northward curve of 
 the isothermals peculiar to this region ; and it is 
 difficult to understand how the formation of 
 Globigerina ooze can be affected by this climatal 
 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 
 material of the sea-bottom in the intermediate 
 zone, throughout both the Atlantic and Pacific 
 Oceans, and the Indian Ocean, at depths from a 
 few hundred to over two thousand fathoms, is 
 established. But it is not the only extensive 
 deposit, which is now taking place. In 1853, 
 Count Pourtal^s, an officer of the United States 
 Coast Survey, which has done so muck., for 
 
92 EXPEDITION OF THE " CHALLENGER m 
 
 scientific hydrography, observed, that the mud 
 forming the sea-bottom at depths of one hundred 
 and fifty fathoms, in 31° 32' N, 79° 35' W., oflf 
 the Coast of Florida, was " a mixture, in about 
 equal proportions, of Glohigerince and black sand, 
 probably greensand, as it makes a green mark 
 when crushed on paper." Professor Bailey, 
 examining these grains microscopically, found 
 that they were casts of the interior cavities of 
 Foraminifcra, consisting of a mineral known as 
 Glauconite, which is a silicate of iron and alumina. 
 In these casts the minutest cavities and finest 
 tubes in the Foraminifer were sometimes repro- 
 duced 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 Foraminifcra 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 
 
tli EXPEDITION OF THE " CHALLENGER " 93 
 
 character in the course of the Agulhas current, 
 near the Cape of Good Hope, and in some other 
 locahties 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 Pacific. But what are the conditions 
 which determine its occurrence, and whence the 
 silex, the 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," greensand 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 kno^vn of the surface fauna, 
 have brought to light the remarkable fact, that 
 while the surface and the shallows abound with 
 
94 EXPEDITION OF THE "CHALLENGER" ill 
 
 Fm-aminifera 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 2,000 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 
 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 
 thousands of miles away from the embouchure of 
 any river, the sea-bottom, at depths approaching 
 to and beyond 3,000 fathoms, no longer consists of 
 GldbigeHna ooze, but of an excessively fine red clay. 
 
Ill EXPEDITION OF THE " CHALLENGER " 95 
 
 Professor Thomson gives the following account 
 of this capital discovery : — 
 
 " According to our present experience, the deposit of Ghhi- 
 gerina ooze is limited to water of a certain depth, the extreme 
 limit of the pure characteristio formation heing placed at a depth 
 of somewhere ahout 2, 250 fathoms. Crossing from these shal- 
 lower regions occupied by the ooze into deeper soundings, we 
 find, univereally, that the calcareous formation gi'adually passes 
 into, and is finally replaced by, an extremely fine pure clay, 
 which occupies, speaking generally, all depths below 2,500 
 fathoms, and consists almost entirely of a silicate of the red 
 oxide of iron and alumina. The transition is veiy slow, and 
 extends over several hundred fathoms of increasing depth ; the 
 shells gradually lose their sharpness of outline, and assume a 
 kind of ' rotten ' look and a 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 disappeared. This brown matter is in the finest possible 
 state of subdivision, so fine that when, after sifting it to separate 
 any organisms it might contain, we put it into jars to settle, it 
 remained for days in suspension, giving 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 considera- 
 tions, to Use three terms for soundings in deep water. Two of 
 these, Gl. oz. and r. cl., were very definite, and indicated 
 strongly -marked formations, with apparently but few charactera 
 in common ; but we frequently 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 recognise the 
 ' grey ooze ' as an intermediate stage between the Globigerina 
 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 oozo, while on the other, the ooze is mixed 
 with an increasing proportion of ' red clay. ' 
 
96 EXtEDITlON OF THE '' CHALLENGER ' ill 
 
 ' "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 cer- 
 tainty for the Atlantic and the Southern Sea, we had, perhaps, 
 the best opportunity of observing it in our first section across 
 the Atlantic, between Teneriffe and St. Thomas. The first four 
 stations on this section, at depths from 1,525 to 2,220 fathoms, 
 show Globigerina ooze. From the last of these, which is about 
 300 miles from Teneriffe, the depth gradually increases 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 
 ' gi'ey ooze, ' for although its nature has altered entirely from the 
 Olobigerina 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 Teneriffe, 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 gradually rises, and, with decreas- 
 ing depth, the grey colour and the calcareous composition of the 
 oozereturn. Three soundings in 2, 050, 1,900, and 1,950 fathoms 
 on the ' Dolphin Rise ' gave highly characteristic examples of 
 the Globigerina formation. Passing from the middle plateau of 
 the Atlantic into the western trough, with depths a little over 
 3, 000 fathoms, the red clay returned in aU its purity ; and our 
 last sounding, in 1,420 fathoms, before reaching Sombrero, 
 restored the Globigerina 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 mUes. Pro- 
 ceeding fi'om east to west, we have — 
 
 About 80 miles of volcanic mud and sand. 
 
 „ 350 
 
 , Globigerina ooze, 
 
 „ 1,050 
 
 , red clay, 
 
 „ 330 
 
 , Globigerina ooze 
 
 , 850 
 
 , red clay, 
 
 „ 40 
 
 , Globigerina ooze ; 
 
 giving a total of 1,900 miles of red clay to 720 miles of Globi- 
 
 gerina ooze. 
 
 
Ill EXPEDITION OF THE " CHALLENGER " 97 
 
 " The nature and origin of this vast deposit of clay is a ques- 
 tion of the very greatest interest ; and although I think there 
 can be no douht that it is in the main solved, yet some matters 
 of detail are still involved in diflSculty. My iirst impression 
 was that it might be the most minutely 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 suspension and distributed by ocean currents, and only 
 making itself manifest in places unoccupied by the Olohigerina 
 ooze. Several cii-cumstances seemed, however, to negative this 
 mode of origin. The formation seemed too unifonn : wherever 
 we met with it, it had the same character, and it only varied in 
 composition in containing less or more carbonate of lime. 
 
 " Again, we were gradually becoming more and more con- 
 vinced that all the important elements of the Gflobigerijia 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 possibly prevent its accumulation ; 
 and the surface conditions in the Mid -Atlantic were very 
 uniform, a moderate current 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 
 MoUiisca, and, in moderate depths, the shells of these are con- 
 stantly mixed with the Glohigerina ooze, sometimes in number 
 sufficient to make up a considerable portion of its bulk. It is 
 clear that these shells must fall in equal numbers 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 absence of shell-secreting animals living on the bottom, on 
 the supposition that the nature of the deposit was injurious to 
 them ; but then the idea of a current sufficiently sti'ong 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. 
 
 "We conclude, therefore, that the 'red clay' is not an addi- 
 tional substance introduced from without, and occupying certain 
 
 VOL. VIII H 
 
98 EXPEDITION OF THE "CHALLENGER" m 
 
 depressed regions on account of some law regulating its deposi- 
 tion, but that it is produced by the removal, by some means or 
 other, over these areas, of the carbonate of lime, which forms 
 probably about 98 per cent, of the material of the Globigerina 
 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 Globigerina ooze is forming, to 
 the region of the clay. We find, first, that the shells of 
 pteropods and other surface MoUusca which are constantly 
 falling on the bottom, are absent, or, if a few remain, they 
 are brittle and yellow, and evidently decaying rapidly. These 
 shells of MoUusca decompose more easily and disappear sooner 
 than the smaller, and apparently 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 scattered over 
 the field. The larger Foraminifera are attacked, 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 chamber-walls of Globigerina fall into wedge- 
 shaped pieces, which quickly disappear, and a thick rough crast 
 breaks away from the surface of Orbulina, leaving a thin inner 
 sphere, at fii-st beautifully transparent, but soon becoming 
 opaque and crumbling away. 
 
 ' ' In the meantime the proportion of the amorphous ' red 
 clay' to the calcareous elements of all kinds increases, 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. ' 
 
 "There seems to be no room left for doubt that the red clay 
 is essentially the insoluble residue, the ash, as it were, of the 
 calcareous organisms which form the Globigerina 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. 
 
Ill EXPEDITION OF THE "CHALLENGER" 99 
 
 Buclianan to the action of weak acid ; and he fovmd that there 
 remained after the carbonate of lime had been removed, about 
 1 per cent, of a reddish mud, consisting of silica, alnmina, and 
 the red oxide of iron. This experiment has been frequently 
 repeated with different samples of Globigerina ooze, and always 
 with the result that a, small proportion of a red sediment re- 
 mains, which possesses all the characters of the red clay. " 
 ***** 
 
 " It seems evident from the observations here recorded, 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 formation with 
 the fine, smooth, homogeneous clays 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 familiar, especially to the student of 
 palseozoic geology, and they often attain a vast thickness. One 
 is inclined, from the gi-eat resemblance between them in com- 
 position and in the general character of the included fauna, to 
 suspect that these may be organic formations, like the modern 
 red clay of the Atlantic and Southern Sea, accumulations 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 cal- 
 careous shells rather stunted, of most of the characteristic deep- 
 water groups of the Southern Sea, including Umbellularia, - 
 Eiiplectella, Ptcrocrinus, Brisinga, OphioglypJia, Pmirtalesia, 
 and one or two Mollusca. This is, however, very rarely the 
 case. Generally the red clay is barren, or contains only a veiy 
 small number of forms. 
 
 It must be admitted that it is very difficult, at 
 
 H 2 
 
100 EXPEDITION OF THE "CHALLENGER" in 
 
 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 
 tentatively, and with much reservation by Pro- 
 fessor Thomson, that the calcareous matter is 
 dissolved out by the relatively fresh water of the 
 deep currents from the Antarctic regions, appears 
 satisfactory to me. Nor do I see my way to the 
 acceptance of the suggestion of Dr. Carpenter, that 
 the red clay is the result of the decomposition of 
 previously-formed greensand. At present there is 
 no evidence that greensand casts are ever formed 
 at great depths; nor has it been proved that 
 Glauconite 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 origin 
 of the abyssal red clay, no less than for that of the 
 sublittoral greensand in the intermediate zone. 
 But the importance of the establishment of the 
 fact that these various deposits are being formed 
 in the ocean, at the present day, remains the same, 
 whether its rationale be understood or not. 
 . For, suppose the globe to be evenly covered with 
 sea, to a depth say of a thousand fathoms — then, 
 whatever might be the mineral matter composing 
 the sea-bottom, little or no deposit would be 
 formed upon it, the abrading and denuding action 
 of water, at such a depth, being exceedingly slight. 
 
Ill EXPEDITION OF THE "CHALLENGER" 101 
 
 Next, imagine sponges, Badiolaria, Foraminifera, 
 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 Sadiolaria and Diatomacem, 
 would increase and multiply in the surface waters. 
 In accordance with the existing state of things, 
 the Badiolaria and Diatoms would have a universal 
 distribution, the latter gathering most thickly in 
 the polar regions, while the Foraminifera would 
 be largely, if not exclusively, confined to the inter- 
 mediate zone ; and, as a consequence of this distri- 
 bution, a bed of " chalk " would begin to form in 
 the intermediate zone, while caps of silicious rock 
 would accumulate on the circumpolar regions. 
 
 Suppose, further, that a part of the intermediate 
 area were raised to within two or three hundred 
 fathoms of the surface — for anjrthing that we know 
 to the contrary, the change of level might deter- 
 mine 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 
 
102 EXPEDITION OF THE "CHALLENGER" III 
 
 skeletons, is correct, then all these deposits alike 
 would be directly, or indirectly, the product of 
 living organisms. But just as a silicious deposit 
 may be metamorphosed into opal or quartzite, and 
 chalk into marble, so known metamorphic agencies 
 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 
 archaeology 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 
 
 1 "Petrificata monthun calcariorum non filii sed parentes 
 sunt, cum omnis calx oriatur ab animalibus." — Systema Naturce, 
 Ed. xii,, t. iii., p. 154. It must be recollected that LinnEeus 
 included silex, as well as limestone, under the name of " calx," 
 and that he would probably 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 
 animalibus, nee vice versa. Sic ruiies saxei non primuevi, sed 
 temporis filise." 
 
Ill EXPEDITION OF THE "CHALLENGER" 108 
 
 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 sihcious 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 organ- 
 isms. 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 
 Challenger. 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 Gldbigerinm ooze has been dissolved 
 away— then clay is as much a product of life as 
 limestone, and all known derivatives of clay may 
 have formed part of animal bodies. 
 
 So long as the Glohigerince, 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 
 reserve 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 " o'upes saxei " 
 
104 EXPEDITION OF THE "CHALLENGER" ill 
 
 axe not only " temporis," but " vitce filice " ; and, 
 consequently, 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 fossiliferous or unfossiliferous. 
 
 And thus we are led to see where the solution 
 of a great problem and apparent paradox of 
 geology 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 
 complete and cogent as such evidence can reason- 
 ably be expected to be ; and the further investiga- 
 tions into the history of the tertiary mammalia are 
 pushed, the greater is the accumulation of evidence 
 having the same tendency. So far from palae- 
 ontology 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 palseonto- 
 logical 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 
 
Ill EXPEDITION OF THE " CHALLENGER " 105 
 
 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 
 Vertebrata are the most complex ; and among 
 these the carnivores and hoofed animals ( Ungulata) 
 are highly differentiated. Nevertheless, although 
 the different lines of modification of the Carnwora 
 and those of the Ungulata, respectively, approach 
 one another, and, although each group is repre- 
 sented by less differentiated forms in the older 
 tertiary 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 
 
106 EXPEDITION OF, THE " CHALLENGER " m 
 
 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 
 animals which, on the hypothesis of evolution, 
 must have existed in myriads in those seas, wherein 
 the many thousand feet of Cambrian and Lauren- 
 tian rocks now devoid, or almost devoid, of any 
 trace of life were deposited ? 
 
 Sir Charles Lyell long ago suggested that the 
 azoic character of these ancient formations might 
 be due to the fact that they had undergone 
 extensive metamorphosis; and readers of the 
 " Principles of Geology " will be familiar with the 
 ingenious manner in which he contrasts the theory 
 of the Gnome, who is acquainted only with the 
 interior of the earth, with those of ordinary 
 philosophers, 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 as- 
 sumed that no metamorphosis could have taken 
 
Ill EXPEDITION OF THE " CHALLENGER " 107 
 
 place. But the formation of greensand, and still 
 more that of the "red clay" (if the Challenger 
 hypothesis be correct) affords an insight into a 
 new kind of metamorphosis — not igneous, but 
 aqueous — by which the primitive nature of a 
 deposit may be masked as completely as it can be 
 by the agency of heat. And, as WyviUe Thomson 
 suggests, in the passage I have quoted above (p. 
 17), it further enables us to assign a new cause 
 for the occurrence, so puzzling hitherto, of 
 thousands of feet of unfossiliferous fine-grained 
 schists and slates, in the midst of formations 
 deposited in seas which certainly abounded in life. 
 If the great deposit of " red clay " now forming in 
 the eastern vaUey of the Atlantic were meta- 
 morphosed into slate and then upheaved, it would 
 constitute an " azoic " 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 
 silicious shells and skeletons ; and, therefore, are 
 such as, up to this time, we should have termed 
 eminently preservable. 
 
 Thus the discoveries made by the Challenger 
 expedition, like all recent advances in our 
 knowledge 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 Uniformitarianism, which, fifty 
 
108 EXPEDITION OF THE " CHALLENGER " III 
 
 years ago, was held only by a small minority of 
 English geologists — LyeU, Scrope, and De la Beche 
 — ^but now, thanks to the long-continued labours 
 of the first two, and mainly 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 registered 
 by the known fraction of the crust of the earth, 
 I believe that uniformitarianism is unassailable. 
 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. Such 
 evidence as we possess all tends in the contrary 
 direction, and is in favour of the same slow and 
 gradual changes occurring then as now. 
 
 But this conclusion in nowise 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 certain that, 
 in so cooling, its contracting crust must have 
 undergone sudden convulsions, which were to our 
 earthquakes as an earthquake is to the vibration 
 caused by the periodical eruption of a Geyser ; but 
 in that case, the earth must, like other respectable 
 parents, have sowed her wild oats, and got through 
 
Ill EXPEDITION OF THE "CHALLENGER" 109 
 
 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, m animo, repeat the saying of Hutton, " We 
 find no vestige of a beginning — no prospect of an 
 end." However, he wiU 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 ex- 
 pressing 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 
 iiltration, from even the finest visible impurities, 
 it wiU not remain clear. After a time it will 
 become cloudy and turbid ; little bubbles wiU 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 soHd 
 particles which produce the turbidity of the liquid 
 
IV YEAST 111 
 
 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 
 moderates. The evolution of bubbles slackens, 
 and finally comes to an end ; scum and lees ahke 
 settle at the bottom, and the fluid is once more 
 clear and transparent. But it has acquired 
 properties of which no trace existed in the 
 original hquid. Instead of being a mere sweet 
 fluid, mainly composed 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 obvious effect upon the animal economy, it 
 has become possessed of a very wonderful influence 
 on the nervous system ; so that in small doses it 
 exhilarates, while in larger it stupefies, and may 
 even destroy life. 
 
 Moreover, if the original fluid is put into a stUl, 
 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 cleaj, volatile substance, which is 
 fighter 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 
 
112 YEAST IV 
 
 is brought in contact with a flame. The Al- 
 chemists called this volatile liquid, which they 
 obtained 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 
 subtle 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 any- 
 thing 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 Helmont, 
 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 obscuriorum 
 sensum referendum," in which the following 
 passage occurs : — 
 
 "Alcohol. — Chymicis est liquor aut pulvis summ^ subtili- 
 satus, vocabulo Orientalibus quoque, cum primis Habessinis, 
 familiari, quibus cohol speciatim pulverem impalpabilem ex 
 antimonio pro oculis tingendis denotat . . . Hodie autem, ob 
 analogiam, quivis pulvis tenerior ut pulvis oculorum cancri 
 
IV YEAST 113 
 
 summfe subtilisatus alcohol audit, baud aliter ao spiritiis rectifl- 
 catissimi alcolisati dicuntur. " 
 
 Similarly, Robert Boyle speaks of a fine powder 
 as " alcohol " ; and, so late as the middle of the 
 last century, the EngHsh lexicographer, Nathan 
 Bailey, defines " alcohol " as " the pure substance 
 of anything separated firom the more gross, a very 
 fine and impalpable powder, cJr a very pure, well- 
 rectified spirit." But, by the time of the publi- 
 cation of Lavoisier's " Traite El^mentaire 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 denotation 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 " fermentation " ; 
 a term based upon the apparent boihng 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 
 retained their verb or their substantive denot- 
 ing the action itself, though we do use names 
 identical with, or plainly derived from, theirs for 
 
 VOL. VIII I 
 
114 YEAST IV 
 
 the scum 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 " beorm " ; and, in the Midland Counties, 
 " barm " is the name by which yeast is still best 
 known. In High German, there is a third name 
 for yeast, "hefe," 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 
 motion 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 bom. Our Vedic forefathers 
 intoxicated themselves with the juice of the 
 " soma " ; Noah, by a not unnatural reaction 
 against a superfluity of water, appears to have 
 
IV 
 
 YEAST 115 
 
 taken the earliest practicable opportunity of 
 qualifying 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, therefore, was in all probability 
 possessed by the prehistoric 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 fermented 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 httle ferment 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. Nevertheless, the commence- 
 ment 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 Hehnont made a first step, 
 by pointing out that the peculiar hissing and 
 bubbling of a fermented hquid is due, not to the 
 evolution of common air (which he, as the inventor 
 
 I 2 
 
116 YEAST IV 
 
 of the term " gas," calls " gas ventosum "), but to 
 that of a peculiar kind of air such as is occasionally 
 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 poisonous 
 aeriform fluid which is produced by the combus- 
 tion 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 finally, 
 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 
 
IV YEAST 117 
 
 complete conception of the nature of the work to 
 be done. The words in which he expresses this 
 conception, in the treatise on elementary chemistry 
 to which reference has already been made, mark 
 the year 1789 as the commencement of a revolu- 
 tion of not less moment in the world of science 
 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 created ; an ei^ual 
 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 combinations of these elements. Upon this priuciple the 
 whole art 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 analysis. 
 
 " 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 fer- 
 mentation : either by determining the nature of, and the elements 
 which compose, the fermentable substances ; or by accurately ex- 
 amining the products resulting from fermentation ; and it is evi- 
 dent that the knowledge of either of these must lead to accurate 
 conclusions concerning the nature and composition of the other. 
 From these considerations it became necessaiy accurately to 
 determine the constituent elements of the fermentable sub- 
 stances ; and for this purpose I did not make use of the com- 
 pound juices of fruits, the rigorous analysis of which is perhaps 
 impossible, but 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 
 
118 YEAST IV 
 
 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 ec^uilibiium 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 converted into the combustible substance 
 called alkohol ; therefore, if it were possible to re-unite alkohol 
 and carbonic 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 
 products 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 is not covered by the alcohol and 
 carbonic acid evolved. The greater part of this 
 deficit is accounted for by the discovery of two 
 substances, glycerine and succinic acid, of the 
 existence of which Lavoisier was unaware, in the 
 
 1 Elements of Chemistry. By M. Lavoisier. Translated by 
 Robert Kerr. Second Edition, 1793 (pp. 186—196). 
 
IV YEAST 119 
 
 fermented liquid. But about 1| 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 
 fermentation have simply undergone rearrange- 
 ment ; like the soldiers of a brigade, who at the 
 word of command divide themselves into the 
 independent regiments 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 
 Appert, whose method of preserving perishable 
 articles of food excited so much attention in 
 France at the beginning of this century. Gay- 
 Lussac, in his " Memoire sur la Fermentation," ^ 
 alludes to Appert's method of preserving beer- 
 wort unfermented for an indefinite time, by 
 simply boiling the wort and closing the vessel 
 in which the boiling fluid is contained, in such 
 a way as thoroughly to exclude air; and he 
 ^ Annates de Chimie, 1810. 
 
120 YEAST IV 
 
 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 efiicient 
 precautions 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 influence becomes profoundly 
 interesting. 
 
 The first step towards the solution of this 
 problem was made two centuries ago by the patient 
 and painstaking Dutch naturahst, Leeuwenhoek, 
 who in the year 1680 wrote thus : — 
 
 "Ssepissime examinavi fermentum cerevisiae, semperque hoc 
 ex globulis per materiam pellucidam fluitantibus, quam cere- 
 visiam esse eensui, constare observavi : vidi etiam evidentissime, 
 unumquemque hujus fermenti globulum denuo ex sex distinetis 
 globulis constare, accurate eidem quantltate et formse, cui 
 globulis sanguinis nostri, respondentibus. 
 
 " Terum talis mihi de horum origine et formatione conceptus 
 formabam ; globulis nempe ex quibus farina Tritici, Hoi-dei, 
 Avense, Fagotritici, se constat aquse calore dissolvi et aquoe com- 
 
IV 
 
 YEAST 121 
 
 misceri ; hac, vero aqua, quam oerevisiam vocare licet, refriges- 
 cente, multos ex minimis particulis in cerevisia coadimaii, et hoc 
 pacto efBcere particulam sive globulum, quae sexta pars est 
 globuli fecis, et iterum sex ex hisce globulis conjungi." ' 
 
 Thus Leeuwenhoek discovered that yeast con- 
 sists of globules floating in a fluid ; hut 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, hut 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 
 colleague, 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- 
 thousandth of an inch in diameter, and the 
 smallest may measure less than one seven- 
 thousandth of an inch, are hving organisms. They 
 multiply with great rapidity by giving off minute 
 buds, which soon attaia the size of their parent, 
 and then either become detached or remain 
 united, forming the compound globules of which 
 ' Leeuwenhoek, Arcana Naturm Detecta. Ed. Nov., 1721. 
 
122 YEAST IV 
 
 Leeuwenhoek 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 cerevisim, were more nearly allied to the 
 lower Fungi than to anything else. Indeed 
 Turpin, and subsequently Berkeley and Hofimann, 
 believed that they had traced the development of 
 the Torula into the weU-known and very common 
 mould — the Penicillium glaucum. Other observers 
 have not succeeded in verifying these statements ; 
 and my own observations lead me to believe, that 
 while the connection between Torula and the 
 moulds is a very close one, it is of a different 
 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, wiljh or without sugar, give rise to 
 Torulce, similar in all respects to T. cerevisicB, 
 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 
 organisms of yeast, are veritable plants ; and con- 
 clusive experiments have proved that the power 
 
IV YEAST 123 
 
 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, 
 stumbhng, with the stride of genius, upon the con- 
 ception which Hes at the bottom of all modern views 
 of the process, put forward the notion that the 
 ferment, being in a state of internal motion, com- 
 municated 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, fall 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, 
 uniting with the nitrogen of the ferment, pro- 
 duces a new substance analogous to opium. This 
 is decomposed by distOlation, and gives rise to 
 alcohol. Next, in 1803, Th^nard propounded a 
 hypothesis which partakes somewhat of the nature 
 of both Stahl's and Fabroni's views. " I do not 
 beheve with Lavoisier," he says, " that all the 
 
124 YEAST 
 
 IV 
 
 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 por- 
 tions 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 be- 
 tween the principles of the sugar being disturbed, 
 they combine afresh to form carbonic acid and 
 alcohol." 
 
 The three views here before us may be familiarly 
 exemphfied 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 
 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, 
 
IT YEAST 125 
 
 amygdalin and STuaptase, 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 s^Tiaptase 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 amj'gdalin. 
 And as the s\Tiaptase is certainly neither organized 
 nor aUve, but a mere chemical substance, Liebig 
 treated Cagniard de la Tour's discovery with no 
 small contempt, and, from that time to the pre- 
 sent, has steadily repudiated the notion that the 
 decomposition of the sugar is, in any sense, the 
 result of the vital activity of the TorvAa,. But, 
 though the notion that the Tarv.la 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- 
 ance in a grave scientific journal,^ may be un- 
 
 1 " Das entrathsclte Geheinmiss der geistigen Gahnuig (Vor- 
 lanfige liriefliche Mittieilnng) " is the title of an anonymous 
 contribution to 'Wbliler and Liebig's Annalen. der Pharmaeie 
 for 1839, in which a somewhat Babelaisian imaginary descrip- 
 tion of the organisation of the "yeast animals " and of the 
 manner in which their functions are performed, is given with a 
 
126 YEAST IV 
 
 tenable, the fact that the Torulce are alive, and 
 that yeast does not excite fermentation unless it 
 contains living Torulce, stands fast. Moreover, of 
 late years, the essential participation of hving 
 organisms in fermentation other than the alcoholic, 
 has been clearly made out by Pasteur and other 
 chemists. 
 
 However, it may be asked, is there any necessary 
 opposition between the so-called " vital " and the 
 strictly physico-chemical views of fennentati'on ? 
 It is quite possible that the living Torula may 
 excite fermentation in sugar, because it constantly 
 produces, as an essential part of its vital manifeSr 
 tations, some substance which acts upon the sugar, 
 just as the sjmaptase acts upon the amygdalin. 
 Or it may be, that, without the formation of any 
 such special substance, the physical condition of 
 the living tissue of the yeast plant is sufficient to 
 effect that small disturbance of the equilibrium of 
 the particles of the sugar, which Lavoisier thought 
 sufficient to effect its decomposition. 
 
 Platinum in a very fine state of division — 
 known as platinum black, or noir de platine — has 
 
 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 namlich die Thiere keinen Zucker mehr vorfinden, so 
 fressen sie sich gegenseitig selbst auf, was durch eine eigene 
 Manipulation geschieht; alles wird verdant bis auf die Eier, 
 welche unverandert durch den Darmkanal hineingehen ; man 
 hat zuletzt wieder gahrungsfahige Hefe, namlich den Saamen 
 der Thiere, der iibrig bleibt." 
 
IV YEAST 127 
 
 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 
 become converted into vinegar ; and Liebig's 
 eminent 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 phenomtae physique qui acoompague la vie de 
 la plante reside dans un etat physique propre, analogue h, celni 
 du noir de platine. Mais il est essentiel de remarquer que cet 
 dtat physique de la plante est etroitement lie avec la vie de 
 cette plante." ^ 
 
 Now, if the vinegar plant gives rise to the oxi- 
 dation of alcohol, on account of its merely phy- 
 sical 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, 
 the present state of speculation upon the modus 
 ojperandi of the yeast plant in producing fermenta- 
 tion is represented, on the one hand, by the 
 Stahhan doctrine, supported by Liebig, according 
 to which the atoms of the sugar are shaken into 
 new combinations, either directly by the Torulm, 
 or indirectly, by some substance formed by them ; 
 
 ^ Mudes sur les Mycodermes, Comptes-Rendus, liv., 1862. 
 
128 YEAST IV 
 
 and, on the other hand, by the Th^nardian doc- 
 trine, supported by Pasteur, according to which 
 the yeast plant assimilates part of the sugar, and, 
 in so doing, disturbs the rest, and determines its 
 resolution into the products of fermentation. Per- 
 haps the two views are not so much opposed as 
 they seem at first sight to be. 
 
 But the interest which attaches to the influence 
 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 Torwlce to the 
 ultimate elements of the tissues of animals and 
 plants — " Les organes elementaires de leurs tissus, 
 comparables aux petits v^gdtaux des levures 
 ordinaires, sont aussi les d^compositeurs des sub- 
 stances qui les environnent." 
 
 Almost at the same time, and, probably, equally 
 guided by his study of yeast, Schwann was en- 
 gaged in those remarkable investigations into the 
 form and development of the ultimate structural 
 elements of the tissues of animals, which led him 
 to recognise their fundamental identity with the 
 ultimate structural elements of vegetable organ- 
 isms. 
 
 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, 
 
IV YEAST 129 
 
 whatever their ultimate complication, begin their 
 existence in the condition of such simple cells. 
 
 In his famous " Mikroskopische Untersuchun- 
 gen " Schwann speaks of Torula 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 fermentation, 
 because it is the most fully and exactly known operation of cells, 
 and represents, in the simplest fashion, the process which is 
 repeated by evei-y 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, ana- 
 logous to that which a Torula exerts on the 
 saccharine solution by which it is bathed. A 
 wonderfully suggestive thought, opening up views 
 of the nature of the chemical processes of the 
 living body, which have hardly yet received all 
 the development of which they are capable. 
 
 Kant defined the special peculiarity of the living 
 body to be that the parts exist for the sake of the 
 whole and the whole for the sake of the parts. 
 But when Turpin and Schwann resolved the living 
 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 
 harmony among these units, or by the superaddition 
 
 VOL. VIII K 
 
130 YEAST IV 
 
 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 Tondm 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 " ceU- 
 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 Tonda. 
 
 From purely morphological investigations, Tur- 
 pin and Schwann, as we have seen, arrived at the 
 notion of the fundamental unity of structure of 
 living beings. 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 
 
 ^ [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.] 
 
IV YEAST 131 
 
 most distinct terms, the important fact that yeast 
 contains a nitrogenous "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 Mulder 
 endeavoured to demonstrate that a peculiar sub- 
 stance, which he called " protein," was essentially 
 characteristic of living matter. 
 In 1846, Payen writes : — 
 
 "Enfin, uue loi sans exception me semble apparaitre dans 
 les faits nonibreux que j'ai obsei'ves et conduire a envisage! sous 
 un nouveau jour la vie vegetale ; si je ue ni'abuse, tout ce que 
 dans les tissus vegetaux la vue directe oil amplifiee nous permet 
 de discerner sous la forme de cellules et de vaisseaux, ne represente 
 auti-e chose que les enveloppes protectiices, les reservoirs et les 
 conduits, h, I'aide desquels les corps animes qui les secretent et les 
 fa9onnent, se logent, puisent et charrient leurs aliments, deposeut 
 et isolent les matieres excretees. " 
 
 And again : — 
 
 " Afin de completer aujourd'liui I'euonce du fait general, je 
 rappellerai que les corps, doud des fonctions accomplies dans 
 les tissus des plantes, sont formes des elements qui constituent, 
 en proportion peu variable, les organismes animaux ; qu'ainsi 
 Ton est conduit h, reconnaitre une immense unite de composition 
 elementaire dans tous les coi-ps vivants de la nature." ^ 
 
 In the year (1846) in which these remarkable 
 passages were published, the eminent German 
 botanist, Von Mohl, invented the word " proto- 
 plasm," as a name for one portion of those nitro- 
 genous contents of the cells of hving plants, the 
 
 ' "Mem. sur les Developpements des Vegetaux," &o. — 3fem. 
 Priseniies. ix. 1846. 
 
 K 2 
 
132 YEAST IV 
 
 close chemical resemblance of which to the essen- 
 tial constituents of hving animals is so strongly 
 indicated by Payen. And through the twenty- 
 five years that have passed, since the matter of 
 hfe was first called protoplasm, a host of investi- 
 gators, among whom Cohn, Max Schulze, and 
 Kuhne must be named as leaders, have accum- 
 ulated evidence, morphological, physiological, and 
 chemical, in favour of that " immense unite de 
 composition ^lementaire dans tous les corps vivants 
 de la nature," into which Payen had, so early, a 
 clear insight. 
 
 As far back as 1850, Cohn wrote, apparently 
 without any knowledge of what Payen had said 
 before him : — 
 
 " The protojilasm of the botanist, and the contractile sub- 
 stance and sarcode of the zoologist, must he, 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 enclosed 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 former, it 
 is not so enclosed. The protoplasm in the form of the primordial 
 utricle is, as it were, the animal element 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. " ^ 
 
 1 Cohn, " Ueber Protococcus pluvialis," in the Nova Acta for 
 1850. 
 
IV YEAST 133 
 
 In 1868, thinking that an untechnical state- 
 ment of the views current among the leaders of 
 biological science might be interesting to the 
 general 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 cb priori road of mere philosophical specu- 
 lation, or by the mere low A posteriori lane offered 
 by the tube of a microscope, but have taken the 
 trouble to become acquainted with well-ascertained 
 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, no- 
 thing that the present state of knowledge does 
 not justify us in believing to be true. Under these 
 circumstances, my surprise may be imagined, when 
 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 
 
 ' Subsequently published under the title of "As regards 
 Protoplasm." 
 
134 YEAST 
 
 IV 
 
 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, 
 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 "Aiifklarung " — a recurrence 
 to the base common-sense philosophy of the 
 eighteenth century, which liked to see before it 
 
IV YEAST 135 
 
 believed, and to understand before it criticised 
 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 pro- 
 nounced untenable — nor less untenable (3) the materialism he 
 would found on it. " 
 
 The paragraph contains three distinct assertions 
 concerning my views, and just the same number of 
 utter misrepresentations of them. That which I 
 have numbered (1) turns on the ambiguity of the 
 word " same," for a discussion of which I would 
 refer Dr. Stirling to a great hero of "Aufkldrung" 
 Archbishop Whately; statement number (2) 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 to show that 
 what is called " materialism " has no sound philo- 
 sophical 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 wiU increase indefin- 
 itely 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 Tondm will manufacture nitrogenous proto- 
 
136 YEAST IV 
 
 plasm, cellulose, and fatty matters, in any quantity, 
 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 heen a 
 great deal of speculation lately, as to how the 
 living organisms huried beneath two or three 
 thousand fathoms of water, and therefore in all 
 probability almost deprived of Hght, live. If any 
 of them possess the same powers as yeast (and 
 the same capacity for living without light is ex- 
 hibited 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 
 propagated 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 FOEMATION 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 aUke. 
 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 
 stratification 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," 
 
138 ON THE FOEMATION OF COAL v 
 
 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 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 
 products 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 result from the burning of so much 
 wood. 
 
 These properties of coal may be made out 
 without any very refined appliances, but the 
 microscope 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.^ 
 
 ' My assistant in the Museum of Practical Geology, Mr. 
 Newton, invented this excellent method of obtaining thin slices 
 of coal. 
 
V ON THE FORMATION OF COAL 139 
 
 Now let us suppose two such slices to be 
 prepared 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 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, 
 disposed in lines which correspond, roughly, with 
 the general direction of the bedding of the coal. 
 
 This is the microscopic structure of an ordinary 
 piece of coal. But if a great series of coals, from 
 different locahties and seams, or even from 
 different parts of the same seam, be examined, 
 this structure wiU be found to vary in two 
 directions. In the anthracitic, or stone-coals, which 
 burn like coke, the yellow matter diminishes, 
 and the ground substance becomes more pre- 
 dominant, blacker, and more opaque, until it be- 
 comes impossible to grind a section thin enough 
 to be translucent ; while, on the other hand, in 
 such as the " Better-Bed " coal of the neighbour- 
 hood of Bradford, which bums 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 
 
140 ON THE FORMATION OF COAL v 
 
 dark brown ground substance. On the average, 
 these httle brown bodies may have a diameter of 
 about one-twentieth of an inch. They he with 
 their flat surfaces nearly parallel with the two 
 smooth faces of the block in which they are con- 
 tained ; 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 complete rings ; while 
 in the vertical sections they appear like thick 
 hoops, the sides of which have been pressed to- 
 gether. 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 
 approximated; 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 
 
V ON THE FORMATION OF COAL 141 
 
 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, by the breaking-up and increasing car- 
 bonization of the larger and the smaller sacs. 
 And, in the anthracitic coals, this process appears 
 to have gone to such a length, as to destroy the 
 original structure 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 
 determined. 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 inner 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 degraded form, constitutes by far the 
 greater part of all the bituminous coals I have 
 examined, is certainly 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. 
 
142 ON THE FORMATION OF COAL v 
 
 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 
 described and figured the coin-shaped bodies, or 
 larger sacs, as I have called them, in a note 
 appended to the famous paper " On the Coal- 
 brookdale Coal-Field," published at that time, 
 by the present President of the Geological Society, 
 Mr. Prestwich. With much sagacity. Professor 
 Monis 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 
 determined 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 
 fossihzed 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 
 LepidodeTwLra 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 terminated by cones, or catkins, 
 somewhat like the bodies so named in a fir, or a 
 
V ON THE FORMATION OF COAL 143 
 
 willow. These conical fruits, however, did not 
 produce seeds; but the leaves of which they 
 were composed bore upon their surfaces sacs fuU 
 of spores or sporangia, such as those one sees on 
 the under surface of a bracken leaf Now, it is 
 these sporangia of the Lepidodendroid plant 
 Flejningites which were identified by 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, super- 
 ficially, 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 LepidodeTidron and those of 
 the existing Lycopodium, 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 
 primitive structure is weU preserved, are simply 
 the sporangia and spores of certain plants, many 
 
144 ON THE FORMATION OF COAL v 
 
 of which were closely aUied to the existing, club- 
 mosses. And if, as I believe, it can be demon- 
 strated that ordinary coal is nothing but 
 " saccular " coal which has undergone a certain 
 amount of that alteration which, if continued, 
 would convert it into anthracite ; then, the con- 
 clusion is obvious, that the great mass of the 
 coal we burn is the result of the accumulation of 
 the spores and spore-cases of plants, other parts of 
 which have famished the carbonized stems and 
 the mineral charcoal, or have left their impressions 
 on the surfaces 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 
 peculiarly abundant amongst the coal-forming 
 plants. But this explanation is at once shown to 
 
V ON THE FORMATION OF COAL 145 
 
 be untenable 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 
 impossible to comprehend how a mass of light 
 and resinous 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. AH I repeat is, that 
 none of the coals which have come under my 
 notice have enabled me to observe such a dif- 
 ference. But, according to Principal Dawson, who 
 has so sedulously examined the fossil remains 
 of plants in North America, it is otherwise 
 with the vast accumulations of coal in that 
 country. 
 
 "The true coa]," says Dr. Dawson, "consists principally of 
 the flattened bark of SigiUarioid and other trees, intei-mixed 
 with leaves of Ferns and Cordaites, and other herbaceous cUbris, 
 and with fragments of decayed wood, constituting ' mineral char- 
 coal,' all these materials having manifestly alike grown and 
 accumulated where we find them." ' 
 
 '■ Acadian Geology, 2nd edition, p. 138. 
 VOL. vin L 
 
146 ON THE FORMATION OF COAL v 
 
 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 
 Canada, 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 
 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 
 slialy 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 con- 
 ditions of accumulation of coal (" Journal of the Geological 
 Society," vol. xxii. pp. 115, 139, and 165). The purer coals cer- 
 tainly consist principally 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 cannels 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 
 sporangium 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 entire mass of the deposit. 
 
 Coal, such as that which has been described, is 
 
V ON THE FORMATION OF COAL 147 
 
 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 
 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 Nova 
 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. Not 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 
 
 L 2 
 
148 ON THE FORMATION OF COAL v 
 
 commonly known as " submarine forests " 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 one of 
 these submarine forest beds should be gradually 
 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 
 Zepidodendron of the ancient world were sub- 
 stituted 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. Con- 
 trary to what might be expected, the dense wood 
 of the tree decays, and suffers firom the ravages of 
 insects, more swiftly than the bark. And the 
 traveller, 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 reptiles, which have sought food or refuge 
 within. 
 
 The trees of the coal forests 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 
 destruction of the woody core; and Sir Charles 
 
V ON THE FORMATION OF COAL 149 
 
 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 different 
 character from that which surrounded the exterior 
 of the trees. Thus, in endeavouring to compre- 
 hend the formation of a seam of coal, we must try 
 to picture 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 
 seasons roUed by, the plants grew and developed 
 their spores and seeds; that they shed these in 
 enormous quantities, which accumulated on the 
 ground beneath ; and that, every now and then, 
 they added a dead frond or leaf; or, at longer 
 intervals, a rotten branch, or a dead trunk, to 
 the mass. 
 
 A certain proportion of the spores and seeds no 
 doubt fulfilled their obvious function, and, car- 
 ried by the wind to unoccupied regions, ex- 
 tended the limits of the forest ; many might be 
 washed away by rain into streams, and be lost ; 
 but a large portion must have remained, to 
 accumulate Hke beech-mast, or acorns, beneath 
 the trees of a modem 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 
 
150 ON THE FORMATION OF COAL v 
 
 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 Hving 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 powder 
 used to be, and I believe still is, employed for two 
 objects which seem, at first sight, to have no par- 
 ticular 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 
 mummy'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 
 
V ON THE FORMATION OF COAL 151 
 
 action 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 
 been converted into a substance hard enough to 
 be rolled into pebbles, while it yet lay at the 
 surface 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 observed 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 con- 
 sistence 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 
 
152 ON THE FORMATION OF COAL V 
 
 have accumulated, subaijrially, upon the surface 
 of a soil covered by a forest of cryptogamous 
 plants, probably tree-ferns. 
 
 As regards this important point of the subaerial 
 region of coal, I am glad to find myself in entire 
 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 : — 
 
 "(3) The microscopical stractuie and chemical composition 
 of the beds of cannel 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 shallow lakes of modern swamps. When such 
 fine vegetable sediment is mixed, as is often the case, with clay, 
 it becomes 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 vege- 
 table 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 decay. 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 occurence of 
 carbonate of iron in connection with them, prove that, when 
 they existed as soils, rain-water, and not sea-water, percolated 
 them. (5) The coal and the fossil forests present many evi- 
 dences 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 (Xylohius) 
 crept into them, and they became dens, or traps, for reptiles. 
 Large quantities 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. (6) Though the roots of 
 
V ON THE FORMATION OF COAL 153 
 
 the Sigillaria bear more resemblance to the rhizomes of certain 
 aquatic plants ; yet, stnicturally, they are absolutely identical 
 with the roots of Cycads, which the stems also resemble. 
 Further, the Sigillarim grew on the same soils which supported 
 Conifers, Lepidodendra, Cordailes, and Ferns — plants which 
 could not have gi'own in water. Again, with the exception 
 perhaps of some Pinnularice and Asterophyllilea, there is a 
 remarkable absence from the coal measures of any fomi of 
 properly aquatic vegetation. (7) The occurrence of marine, or 
 brackish-water animals, in the roofs of coal-beds, or even in the 
 coal itself, affords no evidence of subaqueous accumulation, 
 since the same thing occurs in the case of modern submarine 
 forests. For these and other reasons, some of which are more 
 fully stated in the papers already refen-ed to, while I admit that 
 the areas of coal accumulation were frequently submerged, I 
 must maintain that the time coal is a subaerial 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 covered 
 by one of the great forests of the carboniferous 
 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 supported 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 destroyed, after 
 its formation, in this way. What are now known 
 
154 ON THE FOEMATION OF COAL v 
 
 as coal districts owe their importance to the fact 
 that they were areas of slow depression, during a 
 greater or less portion of the carhoniferous epoch ; 
 and that, in virtue of this circumstance, Mother 
 Earth was enabled to cover 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 
 superincumbent 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 process 
 was repeated until the first of the alternating 
 beds had sunk to near three miles below its 
 original 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 them- 
 selves. 
 
V ON THE FORMATION OF COAL 155 
 
 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- 
 tiously opened ; and like the Djin again, being 
 vaporous, shifting, and indefinable, but unmis- 
 takably gigantic. However modest the bases of 
 one's calculation 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 veiy slow. The 
 climate of the period, in the northern temperate zone, was of 
 such a character that the true conifois show rings of growth, 
 not larger, nor much less distinct, than those of many of their 
 modern congener's. The Sigillariee and Calamiles were not, as 
 often supposed, composed wholly, or even principally, of lax 
 and soft tissues, or necessarily short-lived. The former had, it 
 is time, 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 Sigillariai, the variations in the leaf-scars in 
 different parts of the trunk, the intercalation 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 
 
156 ON THE FORMATION OF COAL v 
 
 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 Sigillariai, 
 and therefore an undisturbed condition of forest growth enduring 
 through many centuries. Further, there is evidence 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 vegetable 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 supposition that 
 each generation of coal plants took ten years to 
 come to maturity — then, each foot-thickness of 
 coal represents five hundred years. The super- 
 imposed beds of coal ia 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 vertical thickness. Suppose it be 
 12,000 feet — which is 240 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 
 
V ON THE FORMATION OF COAL 157 
 
 time which the coal-field represents would be 
 25,000 X 240 = 6,000,000 years. As affording a 
 definite chronology, of course such calculations 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 proverbially safe 
 if he affirms it not to have been built in a day ; 
 and our geological calculations are aU, 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 palaeontology 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 exist. 
 
 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 ancient 
 
158 ON THE FORMATION OF COAL v 
 
 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 
 forest which bears more than a rough analogy with 
 a coaJ-forest. The types may remain, but the 
 details 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 rnight have been excused for moralizing upon 
 the thoughtless and wanton extravagance which 
 Nature displayed in her operations. 
 
 But we have the advantage over our shovel- 
 
V ON THE FORMATION OF COAL 159 
 
 headed predecessor — or possibly ancestor — and can 
 perceive that a certain vein of thrift runs through 
 this apparent prodigality. Nature is never in a 
 hurry, and seems to have had always before her eyes 
 the adage, " Keep a thing long enough, and you 
 win find a use for it." She has kept her beds of 
 coal many millions of years without 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 sufficient wits 
 to make a fire, and then to discover that the black 
 rock would burn. 
 
 I suppose that nineteen hundred years ago, 
 when Julius Caesar 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 bum, and so help to warm his 
 body and cook his food. Saxon, Dane, and 
 Norman swarmed into the land. The EngHsh 
 people grew into a powerful nation, and Nature 
 stiU waited for a full return of the capital she 
 
160 ON THE FORMATION OF COAL v 
 
 had invested in the ancient club-mosses. The 
 eighteenth century arrived, and with it James 
 Watt. The brain of that man was the spore out of 
 which was developed the modem steam-engine, and 
 all the prodigious trees and branches of modem in- 
 dustry which have grown out of this. But coal is 
 as much an essential condition 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 g^reat towns of 
 Yorkshire and Lancashire vanish 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 hfe is Nature's interest upon her investment 
 in club-mosses, and the like, so long ago. But 
 what becomes of the coal which is burnt in yield- 
 ing 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 
 matters, exactly equal in weight to the coal. But 
 these are the very matters with which Nature 
 supplied the club-mosses which made the coal 
 
V ON THE FORMATION OF COAL 161 
 
 She is paid back principal and interest at the 
 same time ; and she straightway invests the car- 
 bonic 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 ! 
 
 w 
 
VI 
 
 ON THE BOEDER TERRITORY BETWEEN 
 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- 
 century, and the extent of the modification which 
 has thereby been effected in some of the funda- 
 mental conceptions of the naturalist. 
 
 In the second edition of the " Regne Animal," 
 published in 1828, 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 sub- 
 
VI ANIMALS AND PLANTS 163 
 
 divided from the earKest times into animated 
 beings, which possess sense and motion, and inani- 
 mated beings, 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 charac- 
 teristic partiality for teleological reasoning, de- 
 duces 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, Cuvier 
 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 
 
 ' ir 2 
 
164 ANIMALS AND PLANTS VI 
 
 were no means by which the motion of its fluids 
 could be produced by internal causes. Hence 
 arose the second great distinctive character of 
 animals, or the circulatory system, which is less 
 important than the digestive, since it was un- 
 necessary, and therefore is absent, in the more 
 simple animals. 
 
 Animals further needed muscles for loco- 
 motion and nerves for sensibility. Hence, says 
 Cuvier, it was necessary that the chemical compo- 
 sition of the animal body should be more compli- 
 cated than that of the plant ; and it is so, inasmuch 
 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 after- 
 wards affirms that nitrogen is peculiar to animals ; 
 and herein he places the third distinction between 
 the animal and the plant. The soil and the 
 atmosphere supply plants with water, composed of 
 hydrogen and oxygen ; air, consisting of nitrogen 
 and oxygen ; and carbonic acid, containing carbon 
 and oxygen. They retain the hydrogen and the 
 carbon, exhale the superfluous oxygen, and absorb 
 little or no nitrogen. The essential character of 
 vegetable life is the exhalation of oxygen, which 
 is effected through the agency of light. Animals, 
 on the contrary, derive their nourishment either 
 directly or indii-ectly from plants. They get rid of 
 
VI ANIMALS AND PLANTS 165 
 
 the superfluous hydrogen and carbon, and accumu- 
 late nitrogen. The relations of 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. 
 Respiration — that is, the absorption of oxygen and 
 the exhalation of carbonic acid — is the specially 
 animal function of animals, and constitutes their 
 fourth distinctive character. 
 
 Thus wrote Cuvier in 1828. But, in the fourth 
 and fifth decades of this century, the greatest and 
 most rapid revolution which biological science has 
 ever undergone was effected by the application of 
 the modern microscope to the investigation of 
 organic structure ; by the introduction of exact 
 and easily manageable methods of conducting the 
 chemical analysis of organic compounds; and 
 finally, by the employment of instruments of pre- 
 cision 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 Ghar<x, 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. Robert Brown noted the 
 more complex motions of the protoplasm in the 
 cells of Tradesmntia in 1831 ; and now such move- 
 ments of the living substance of plants are well 
 
166 ANIMALS AND PLANTS vi 
 
 known to be some of the most widely-prevalent 
 phenomena of vegetable life. 
 
 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 Inftisoria, 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 appearance, as spontaneous 
 — 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 
 
VI ANIMALS AND PLANTS 167 
 
 broken down, so far, at least, as his mode of stating 
 it goes. And, with the advance of microscopic 
 anatomy, the universality of the fact itself among 
 animals has ceased to be predicable. Many 
 animals of even complex structure, which live 
 parasitically 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 
 Rotifers have no digestive apparatus ; as a German ■ 
 naturalist has remarked, they devote themselves 
 entirely 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 animal life, the speck of gelatinous 
 protoplasm, which constitutes the whole body, has 
 no permanent digestive cavity or mouth, but takes 
 in its food anywhere ; and digests, so to speak, all 
 over its body. 
 
 But although Cuvier's leading diagnosis of the 
 animal from the plant wiU 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 
 
168 ANIMALS AND PLANTS vi 
 
 hand, the definition thus amended will exclude all 
 ordinary vegetable organisms. 
 
 Cuvier himself practically gives up his second 
 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 differences 
 and resemblances between the constituents of 
 animal 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 substances 
 are largely manufactured, even by the highest 
 animals ; cellulose is widespread as a constituent 
 of the skeletons of the lower animals; and it is 
 probable that amyloid substances are universally 
 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 cai'bonic acid ; yet. 
 
VI ANIMALS AND PLANTS 169 
 
 the exact researches of the modern chemical in- 
 vestigators of the physiological processes of plants 
 have clearly demonstrated the fallacy of attempt- 
 ing to 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 oxygen 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 iirst can be re- 
 tained only in a modified form and subject to 
 exceptions. 
 
 But has the advance of biology simply tended 
 to break down old distinctions, without establish- 
 ing new ones ? 
 
 With a qualification, to be considered presently, 
 the answer to this question is undovibtedly in the 
 affirmative. The famous researches of Schwann 
 
 ' There is every reason to believe that living plants, like living 
 animals, always respire, and, in respiring, absorb oxygen and 
 give off carbonic acid ; but, that in green plants exposed 
 to daylight or to the electric light, the quantity of oxygen 
 evolved in consequence of the decomposition of carbonic acid 
 by a special appajatus which gi'een plants possess exceeds that 
 absorbed in the concurrent respiratory process. 
 
170 ANIMALS AND PLANTS vi 
 
 and Schleiden in 1837 and the following years, 
 founded the modern science of histology, or that 
 branch of anatomy which deals with the ultimate 
 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 firmness to 
 Schwann's great generalisation, that a fundamental 
 unity of structure obtains in animals and plants ; 
 and that, however diverse may be the fabrics, or 
 tissues, of which their bodies are composed, all 
 these varied structures result from the meta- 
 morphosis 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 respectively, but 
 present a close resemblance, when those of animals 
 and those of plants are compared together. 
 
 The contractility which is the fundamental con- 
 dition of locomotion, has not only been discovered 
 to exist far more widely among plants than was 
 formerly imagined ; but, in plants, the act of con- 
 traction 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 Reymond to be a 
 concomitant of the activity of ordinary muscle in 
 animals. 
 
VI ANIMALS AND PLANTS 171 
 
 Again, I know of no test by which the reaction 
 of the leaves of the Sundew and of other plants to 
 stimuli, so fully and carefully studied by Mr. 
 Darwin, can be distinguished from those acts of 
 contraction following upon stimuli, which are 
 called " reflex " in animals. 
 
 On each lobe of the bilobed leaf of Venus's fly- 
 trap (DioncBa muscipula) are three delicate filaments 
 which stand out at right angle from the surface of 
 the leaf. Touch one of them with the end of a 
 fine human hair and the lobes of the leaf instantly 
 close together ^ in virtue of an act of contraction 
 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 contract, 
 the act of retraction is brought about. Of course 
 the similarity of the acts does not necessarily in- 
 volve the conclusion that the mechanism by 
 which they are effected is the same; but it 
 suggests a suspicion of their identity which needs 
 careful testing. 
 
 The results of recent inquiries into the structure 
 of the nervous system of animals converge towards 
 the conclusion that the nerve fibres, which we 
 ^ Danvin, Insectivorous Plants, p. 289. 
 
172 ANIMALS AND PLANTS vi 
 
 have hitherto regarded as ultimate elements of 
 nervous tissue, are not such, but are simply the 
 visible aggregations of vastly more attenuated 
 filaments, the diameter of which dwindles down to 
 the limits of our present microscopic vision, greatly 
 as these have been extended by modem 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 
 organism — one of which is able to affect the other 
 by means of the communication so established. 
 Hence, it is conceivable that even the simplest 
 living 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 difiiculty, which must be 
 attacked from a new point of view and by the aid 
 of methods which have yet to be invented. 
 
 Thus it must be atlmitted that plants may be 
 contractile and locomotive ; that, while locomotive, 
 their movements may have as much appearance 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 
 nervous system in animals. And it must be 
 allowed to be possible that further research may 
 reveal the existence of something comparable to a 
 nervous system in plants. So that I know not 
 where we can hope to find any absolute distinction 
 
VI ANIMALS AND PLANTS 173 
 
 between animals and plants, unless we return to 
 their mode of nutrition, and inquire whether 
 certain 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 stem and leaves of a vigorous bean-plant ; and 
 this plant will, in due time, flower and produce its 
 crop of beans, just as if it were grown in the 
 garden 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 
 
174 ANIMALS AND PLANTS 
 
 VI 
 
 of the food of the bean. But the weights of the 
 carbon, hydrogen, oxygen, nitrogen, phosphorus, 
 sulphur, and other elementary 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 manu- 
 factured 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 
 lajdng 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 carbon ; 
 the air, to which the leaves are exposed, contains 
 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 ^ is the apparatus by 
 
 1 I purposely assume that the air irith which the bean is 
 supplied in the case stated contains no ammoniacal salts. 
 
 '■' The recent researches of Pringsheim have raised a host of 
 questions as to the exact share taken by chlorophyll in the 
 chemical operations which are effected by the gi-een parts of 
 plants. It may be that the chlorophyll is only a constant con- 
 comitant of the actual deoxidising apparatus. 
 
VI ANIMALS AND PLANTS 175 
 
 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 un- 
 able to extract the carbon which they require 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 sub- 
 stitute 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 car- 
 bonic acid, they must be furnished with something 
 else that contains carbon. Tartaric acid is such a 
 substance ; and if a single spore of the commonest 
 and most troublesome of moulds — Penicillium — be 
 sown in a saucerful of water, in which tartrate of 
 ammonia, with a small percentage of phosphates 
 and sulphates is contained, and kept warm, whether 
 in the dark or exposed to light, it will, in a 
 short time, give rise to a thick crust of mould, 
 
176 ANIMALS AND PLANTS vi 
 
 which contains many miUion times the weight of 
 the original spore, in protein compounds and 
 cellulose. Thus we have a very wide basis of fact 
 for the generalisation that plants are essentially 
 characterised by their manufacturing capacity — by 
 their power of working up mere mineral matters 
 into complex organic compounds. 
 
 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, 
 necessarily, 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 proUtaire of the living 
 world, the worker who produces ; the animal, the 
 ideal aristocrat, who mostly occupies himself in 
 consuming, after the manner of that noble repre- 
 
VI ANIMALS AND PLANTS 177 
 
 sentative 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 
 allegiance in any other way. 
 
 Some months ago. Professor TjTidall 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 Oscillatorice and the lower forms 
 of Fungi, justify this conclusion, but the manu- 
 facturing 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 ammonia are dissolved ; 
 and, in a very short space of time, the clear fluid 
 becomes milky by reason of their prodigious 
 multiplication, which, of course, implies the 
 manufacture of living Bacterium-stuff out of 
 these merely saline matters. 
 
 VOL. VIII N 
 
178 ANIMALS AND PLANTS vi 
 
 But other active organisms, very much larger 
 than the Bacteria, attaining in fact the com- 
 paratively gigantic dimensions of -g^nnr of an 
 inch or 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 incurvation, proceeded another long cdium, 
 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; some- 
 times it anchored itself by the hinder cilium and 
 was spun round by the working of the other, its 
 motions resembling those of an anchor buoy in a 
 heavy sea. Sometimes, when two were in fiill 
 career towards one another, each would appear 
 dexterously to get out of the other's way ; some- 
 times a crowd would assemble and jostle one 
 
VI ANIMALS AND PLANTS 179 
 
 another, with as much semblance of individual 
 effort as a spectator on the Grands Mulcts 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 
 biologists call Monads, and though they might be 
 animals, it was also possible that they might, 
 like the Bacteria, be plants. My friend received 
 ray verdict with an expression which showed a 
 sad want of respect for authority. He would as 
 soon believe 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 insufficient to enable him 
 to see that it is curiously like a much larger 
 
 N 2 
 
180 ANIMALS AND PLANTS vi 
 
 form of monad whicli 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 be 
 months, of unremitting attention. But I the less 
 regret this circumstance, as some remarkable 
 observations recently published by Messrs. Dal- 
 linger 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 painstaking observers, who employed the 
 highest attainable powers of the microscope 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, except that it has a separately dis- 
 tinguishable central particle or " nucleus," which 
 is not certainly to be made out in Heteromita 
 lens ; and that nothing is said by Messrs. Dallinger 
 
 1 " Researches in the Life-history of a Cercomonad : a Lesson 
 in Biogenesis"; and "Further Researches in the Life-history 
 of the Monads." — Monthly MicroscopicalJownal, 1873. 
 
VI ANIMALS AND PLANTS 181 
 
 and Diysdale of the existence of a contractile 
 vacuole in this monad, though they describe it in 
 another. 
 
 Their Heteromita, how^ever, 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 
 To 0^0 of ^n 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 itself, a complete Heteromita, 
 provided with its two cilia. Sometimes the con- 
 striction took a longitudinal direction, with the 
 same ultimate result. In each case the process 
 occupied not more than six or seven minutes. 
 At this rate, a single Heteromita 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 Heteromita an hour's 
 enjoyment of individual existence, 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. 
 
182 ANIMALS AND PLANTS 
 
 VI 
 
 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 
 portions, 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 Heteromitw become applied 
 to one another, and then slowly and gradually coa- 
 lesce into one body. The two nuclei run into one ; 
 and the mass resulting from the conjugation of the 
 two Heteromitm, thus fused together, has a tri- 
 angular form. The two pairs of cilia are to be 
 seen, for some time, at two of the angles, which 
 answer to the smaU ends of the conjoined monads ; 
 but they ultimately vanish, and the twin organ- 
 ism, in which all visible traces of organisation 
 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 triangular mass burst, and give exit to a 
 dense yellowish, glairy fluid, filled with minute 
 granules. This process, which, it wiU be observed, 
 involves the actual confluence and mixture of the 
 substance of two distinct organisms, is efiected in 
 the space of about two hours. 
 
 The authors whom I quote say that they 
 
VI ANIMALS AND PLANTS 183 
 
 " cannot express " the excessive minuten'ess of the 
 granules in question, and they estimate their 
 diameter at less than awinrTr of ^^ inch. Under 
 the highest powers of the microscope, at present 
 apphcable, 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 molecular 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 infinitesimal 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 characteristic cilia, 
 though at first they were quite motionless ; and, 
 in four hours more, they had attained the dimen- 
 sions and exhibited all the activity of the adult. 
 These inconceivably minute particles are therefore 
 the germs of the Heteromita ; and fi-om 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 thousand of 
 them ; a result of a matrimonial process whereby 
 the contracting parties, without a metaphor, " be- 
 come one flesh," enough to make a Malthusian 
 despair of the future of the Universe. 
 
 I am not aware that the investigators from 
 
184 ANIMALS AND PLANTS 
 
 VI 
 
 wliom I "have borrowed this history have en- 
 deavoured to ascertain whether their monads take 
 soHd nutriment or not ; so that though they help 
 us very 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 
 Heteromita as a plant. 
 
 For example, there is a Fungus, an obscure and 
 almost microscopic mould, termed Perono^ora 
 infestans. Like many other Fungi, the Perono- 
 sporce are parasitic upon other plants; and this 
 particular Peronospora happens to have attained 
 much notoriety and political importance, in a way 
 not without a parallel in the career of notorious 
 pohticians, 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 hypJice, which burrow through 
 the substance 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 
 
VI ANIMALS AND PLANTS 185 
 
 framework becomes blackened, sodden, and 
 withered. 
 
 In structure, however, the Peronospora is as 
 much a mould as the common Penicillium ; and 
 just as the Penicillium multiplies by the breaking 
 up of its hyphas into separate rounded bodies, the 
 spores ; so, in the Peronospora, certain of the 
 hyphse grow out into the air through the interstices 
 of the superficial cells of the potato plant, and 
 develop spores. Each of these hjrphje 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 con- 
 tents of the spore divide into six or eight separate 
 portions. 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 cihum vibrates 
 actively, and effects the locomotion of the organ- 
 
186 ANIMALS AND PLANTS vi 
 
 ism, while the other trails behind ; the whole 
 body rolling on its axis with its pointed end 
 forwards. 
 
 The eminent botanist, De Bary, who was not 
 thinking of our problem, tells us, in describing the 
 movements of these "Zoospores," 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 
 observed in microscopic animals." 
 
 After swarming about in this way in the 
 moisture 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 dis- 
 appear, it assumes a spherical form, and surrounds 
 itself with a distinct, though delicate, membranous 
 coat. A protuberance then grows out fi-om one 
 side of the sphere, and rapidly increasing in length, 
 assumes the character of a h3?pha. 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 
 myceUum, in the substance of the plant, destroying 
 the tissues with which it comes in contact. As 
 these processes of multipHcation take place very 
 rapidly, millions of spores are soon set fi-ee from a 
 single infested plant ; and, from their minuteness, 
 
VI ANIMALS AND PLANTS 187 
 
 they are readily transported by the gentlest 
 breeze. Since, again, the zoospores set free from 
 each spore, in virtue of their powers of locomotion, 
 swiftly disperse themselves over the surface, it is 
 no 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 
 simply because it affords an example of an organ- 
 ism, which, in one stage of its existence, is truly a 
 " Monad," indistinguishable by any important 
 character from our Heteromita, and exti:0,ordinarily 
 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 
 
188 ANIMALS AND PLANTS vi 
 
 ordinary way. This process obviously corresponds 
 with the conjugation and subsequent setting free 
 of germs in the Heteromita. 
 
 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, selected 
 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 \is, therefore, take a case which is not open 
 to these objections. 
 
 There are some small plants known to botanists 
 as members of the genus Goleochmte, 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 undoubtedly has the manufacturing power in 
 full degree, decomposing carbonic acid'and setting 
 oxygen free, under 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 ciha. Pro- 
 pelled by these, it swims about for a longer or 
 
VI ANIMALS AND PLANTS 189 
 
 shorter time, but at length comes to a state of 
 rest and gradually grows into a Coleochcete. 
 Moreover, as in the Peronosjpora, conjugation may 
 take 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 GokocluBte were unknown, they would 
 undoubtedly be 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 
 animalcule,'' which run through a cycle of forms 
 of just the same simple character as those of 
 Heteromita. 
 
 The name of Chlamydomonas is applied to certain 
 microscopic green bodies, each of which consists of 
 a protoplasmic central substance invested by a 
 structureless sac. The latter contains cellulose, as 
 in ordinary plants; and the chlorophyll which 
 gives the green colour enables the Chlamydomonas 
 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 mobihty, is 
 
190 ANIMALS AND PLANTS vi 
 
 characteristically a plant. Under ordinary cir- 
 cumstances, the Chlamydomonas multiplies by 
 simple fission, each splitting into two or into four 
 parts, which separate and become independent 
 organisms. Sometimes, however, the Chlamy- 
 domonas 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 
 Chlamydomonas and Heteromita is of the closest 
 description. 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 Fofeoa;-monad, 
 moreover, possesses a red pigment spot, like the 
 simplest form of eye known among animals. The 
 methods of fissive multiplication and of conjugation 
 observed in the monads of this locomotive globe 
 are essentially similar to those observed in Chlamy- 
 domonas; and, though a hard battle has been 
 
VI ANIMALS AND PLANTS 191 
 
 fought over it, Volvox is now finally surrendered to 
 the Botanists. 
 
 Thus there is really no reason why Heteromita 
 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 
 organisms 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 Cuvier's 
 definition of an animal. Numerous forms of such 
 animals have been described by Ehrenberg, 
 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 animalcules 
 belonging to the well-known species Colpoda 
 cucullus} 
 
 Full-sized specimens of this animalcule attain a 
 length of between -^^ or ^^^ of an inch, so that it 
 may have ten times the length and a thousand 
 times the mass of a Heteromita. In shape, it is 
 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 
 
 ' Excellently described by Stein, almost all of whose state- 
 ments I have verified. 
 
192 ANIMALS AND PLANTS vi 
 
 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 Heteromita, there is a conical depression, 
 the mouth ; and, in young specimens, a tapering 
 filament, 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 conditions, 
 it becomes quiescent, incloses itself in a delicate 
 case or cyst, and then divides into two, four, or 
 more portions, which are eventually set free and 
 swim about as active Golpodm. 
 
 But this creature is an unmistakable animal, 
 and full-sized Golpodce 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 hve, and, in a very short time, the bodies of 
 the Golpodm are stuffed with the deeply-coloured 
 granules of the pigment. 
 
 And if this were not sufiicient evidence of the 
 animality of Colpoda, there comes the fact that it 
 is even more similar to another weU-knowm 
 animalcule, Paramcecium, than it is to a monad. 
 
VI ANIMALS AND PLANTS 193 
 
 But Parammcium is so huge a creature compared 
 with those hitherto discussed — it reaches yiu of 
 an inch or more in length — ^that there is no dififi- 
 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 
 compHcated organisation. For example, the sur- 
 face layer of its body is different in structure from 
 the deeper parts. There are two contractile 
 vacuoles, from each of which radiates a system of 
 vessel-hke canals ; and not only is there a conical 
 depression continuous with a tube, which serve as 
 mouth and gullet, but the food ingested takes a 
 definite course, and refiise is rejected from a 
 definite 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, sur- 
 rounded 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 cir- 
 culate up one side and down the other, until its 
 contents are digested and assimilated. Neverthe- 
 less, this complex animal multiplies by division, as 
 the monad does, and, Hke the monad, undergoes 
 conjugation. It stands in the same relation to 
 Heteromita on the animal side, as Coleochmte 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 
 VOL. VIII 
 
194 ANIMALS AND PLANTS VI 
 
 progress where the Hne between the animal and 
 the plant must be drawn. 
 
 There is reason to think that certain organisms 
 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, metalUc and earthy salts ; while 
 others need to be suppHed 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 prepared — still more 
 nearly approximated to protein — until we arrive at 
 such organisms as the Psorospermim and the Pan- 
 histophyton, which are as much animal as vegetable 
 in structure, but are animal 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 most vigorously when supplied 
 with the complex nitrogenous substance, pepsin; 
 
VI ANIMALS AND PLANTS 195 
 
 the probability that the Peronospora is nourished 
 directly by the protoplasm of the potato-plant; 
 and the wonderful facts which have recently been 
 brought to light respecting insectivorous plants, all 
 favour this view ; and tend to the conclusion 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 essentially insoluble. 
 
vn 
 
 A LOBSTER; OR, THE STUDY OF 
 ZOOLOGY 
 
 [1861] 
 
 Natural History is the name familiarly applied 
 to the study of the properties of such natural 
 bodies as minerals, plants, and animals; the 
 sciences which embody the knowledge man has 
 acquired upon these subjects are commonly termed 
 Natural Sciences, in contradistinction to other so- 
 called " physical " sciences ; and those who devote 
 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 
 distinctive characters of minerals, animals, and 
 
Vli THE STUDY OF ZOOLOGY 197 
 
 plants. But the enormous stimulus which 
 Linnseus gave to the investigation of nature soon 
 rendered it impossible that any one man should 
 write another " Systema Naturae," and extremely 
 difficult 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 
 attached 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 
 advance of knowledge has gradually widened the 
 distance 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 
 convenient (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 
 
198 THE STUDY OF ZOOLOGY 
 
 Vll 
 
 worlds, but the ground common to these kingdoms 
 of nature is not of very wide extent, and the 
 multipHcity 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 apphed 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 ethno- 
 logist; but if he dissects animals, or examines 
 into the mode in which their functions are per- 
 formed, he is a comparative anatomist or com- 
 parative physiologist. If he turns his attention to 
 fossil animals, he is a palaeontologist. If his mind 
 is more particularly directed to the specific de- 
 scription, discrimination, classification, and distri- 
 bution 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 
 
VII THE STUDY OF ZOOLOGY 199 
 
 divisible into three great but subordinate sciences, 
 morphology, physiology, and distribution, each of 
 which may, to a very great extent, be studied in- 
 dependently of the. other. 
 
 Zoological morphology is the doctrine of animal 
 form or structure. Anatomy is one of its branches ; 
 development is another ; while classification is the 
 expression of the relations which different 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 obtain 
 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 
 deduce 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 
 
200 THE STUDY OF ZOOLOGY vil 
 
 cominoner the better, and let us see how the appli- 
 cation of common sense and common logic to the 
 obvious facts it presents, inevitably leads us into 
 all these branches of zoological ecience. 
 
 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 distinct 
 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 re- 
 present 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 second ; 
 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 
 anatomy, "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 
 corresponding 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. 
 
VII THE STUDY OF ZOOLOGY 201 
 
 and yet different from, the others. The ring is 
 essentially the same as in the other divisions ; but 
 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 
 divisions, 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 differ 
 from any of those yet examined in the simplicity 
 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 curious 
 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 antennse, 
 
202 THE STUDY OF ZOOLOGY vil 
 
 followed by six pairs of jaws folded against one 
 another over the mouth, and five pairs of legs, the 
 foremost of these being the great pinchers, 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 parts 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, mounted 
 
VII THE STUDY OF ZOOLOGY 203 
 
 upon a common stem ; and if I compare this jaw 
 with the legs behind it, or the jaws in front of 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 
 difficult 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 
 foremost jaw, the so-called mandible, the inner 
 division 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 
 abdomen of the lobster, pervades the whole organ- 
 isation of its skeleton, so that I can return to the 
 diagram 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 
 movable, and what has become fixed to another ; 
 
204 THE STUDY OF ZOOLOGY vii 
 
 what has been excessively developed and metamor- 
 phosed and what has been suppressed. 
 
 But I imagine I hear the question, How is all 
 this to be tested ? No doubt it is a pretty and 
 ingenious 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 fuUy 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 
 scientific 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 
 complexity of which, in the adult, are so surprising. 
 After a time, a delicate patch of cellular membrane 
 appeared 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. 
 
VII THE STUDY OF ZOOLOGY 205 
 
 Gradually investing the yolk, it became subdivided 
 by transverse constrictions into segments, the 
 forerunners of the rings of the body. Upon the 
 ventral surface of each of the rings thus sketched 
 out, a pair of bud-like prominences made their ap- 
 pearance — 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 hmbs 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 because 
 the zoologist finds them to be of universal applica- 
 tion. 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 exactly the 
 same point. Unity of plan everywhere Hes hidden 
 under the mask of diversity of structure — the 
 
206 THE STUDY OF ZOOLOGY vii 
 
 coipplex is everywhere evolved out of the simple. 
 Every animal has at first the form of an 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 hitherto 
 spoken as if the lobster were alone in the world, 
 but, as I need hardly remind you, there are 
 myriads 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 cray fish, the rock lobster, and the 
 prawn, and the shrimp, for example, however 
 different, are yet so like lobsters, that a child 
 would group them as of the lobster kind, in contra- 
 distinction to snails and slugs ; and these last again 
 would form a kind by themselves, in contradis- 
 tinction 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 subdivisions 
 than the sexes, or various breeds, are called, in 
 technical language, species. The English lobster 
 
Vii THE STUDY OF ZOOLOGY 207 
 
 is a species, our cray fish is another, our prawn is 
 another. In other countries, however, there are 
 lobsters, cray fish, and prawns, very hke 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 cray fish, 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 fi:om all other animals ; 
 whence they collectively constitute the larger 
 group, or class, Crustacea. But the Cnistacea 
 exhibit many peculiar features in common with 
 insects, spiders, and centipedes, so that these are 
 grouped into the still larger assemblage or " pro- 
 vince" 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 Anmdosa. 
 
 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 
 
208 THE STUDY OF ZOOLOGY vil 
 
 what naturalists term the sub-kingdom Ccelenterata, 
 would have grouped themselves around my type ; 
 had a snail been chosen, the inhabitants of all 
 univalve and bivalve, land and water, shells, the 
 lamp shells, the squids, and the sea-mat would 
 have gradually linked themselves on to it as mem- 
 bers of the same sub-kingdom of Mollusca; and 
 finally, starting from man, I should have been com- 
 pelled to admit first, the ape, the rat, the horse, 
 the dog, into the same class ; and then the bird, 
 the crocodile, the turtle, the frog, and the fish, 
 into the same sub-kingdom of Vertebrata. 
 
 And if I had followed out all these various Unes 
 of classification fiiUy, 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 animal 
 is organised upon one or other of the five, or more, 
 plans, the existence of which renders our classifi- 
 cation possible. And so definitely and precisely 
 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 sHghtest degree transitional between any of 
 the two groups Vertebrata, Annulosa, Mollusca, 
 and Co&lenterata, either exists, or has existed, 
 during that period of the earth's history which is 
 recorded by the geologist.^ Nevertheless, you 
 must not for a moment suppose, because no such 
 
 [' The different grouping necessitated by later knowledge 
 does not affect the principle of the argument. — 1894.] 
 
VII THE STUDY OF ZOOLOGY 209 
 
 transitional forms are known, that the members of 
 the sub-kingdoms are disconnected from, or inde- 
 pendent 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 faunae 
 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 alHed, but distinct forms — 
 the Homanis Americanus and the Homarus 
 Oapcnsis : so that we may say that the European 
 has one species of Homarus ; the American, 
 another ; the African, another ; and thus the 
 
 VOL. VIII p 
 
210 
 
 THE STUDY OF ZOOLOGY 
 
 remarkable 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 deposits, 
 which have served as the great burying grounds of 
 past ages, numberless lobster-like animals, but 
 none so similar to our Hving 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 remains 
 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 
 geology. 
 
 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 
 classification. If we were to examine every 
 animal in a similar manner, we should estabhsh a 
 complete body of zoological morphology. 
 
 Again, we investigated the distribution of our 
 type in space and in time, and, if the hke had 
 been done with every animal, the sciences of geo- 
 
Vll THE STUDY OF ZOOLOGY 211 
 
 graphical and geological distribution would have 
 attained their Kmit. 
 
 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 morphology 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 chmbing 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-hke 
 propeller : seize it, and it will show you that its 
 great claws are no mean weapons of offence ; sus- 
 pend 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 
 
 p -2 
 
212 THE STUDY OF ZOOLOGY VII 
 
 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. 
 Morphology 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 organ of locomotion, by means of 
 which the animal 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 
 itself 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 off the 
 tan, 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 
 
VII THE STUDY OF ZOOLOGY 213 
 
 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 
 centres of motions of the different rings, the 
 bending 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 technicallj^ called 
 muscles. 
 
 Here, then, is a capital fact. The movements 
 of the lobster are due to muscular contractiUty. 
 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, it 
 these communicating cords are cut, the brain 
 remaining entire, the power of exerting what we 
 call voluntary motion in the parts below the sec- 
 
214 THE STUDY OF ZOOLOGY vil 
 
 tion is destroyed ; and, on the other hand, if, the 
 cords remaining entire, the brain mass be destroyed, 
 the same voluntary mobihty 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 pecuhar energy which 
 resides in the nerves has been found to be accom- 
 panied 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 wiU 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 success- 
 fully performed for all the operations which are 
 carried on in, and by, the animal frame, physiology 
 would be perfect, and the facts of morphology 
 
VII THE STUDY OF ZOOLOGY 215 
 
 and distribution would be deducible from the 
 laws which physiologists had estabhshed, com- 
 bined with those determining the condition of the 
 surrounding universe. 
 
 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 
 science, or indeed any physical science, may be 
 best taught. The great matter is, to make 
 teaching real and practical, by fixing the atten- 
 tion 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 knowledge of zoology, which is real and 
 genuine, however limited it may be, and which is 
 worth more than all the mere reading knowledge 
 of the science he could ever acquire. His zoologi- 
 
216 THE STUDY OF ZOOLOGY vil 
 
 cal infonnation 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 
 department, I should pursue a course precisely 
 similar in principle to that which I have taken 
 to-night. I should select a fresh-water sponge, 
 a fresh-water polype or a Cyancea, 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 similarly 
 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 know- 
 ledge 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 
 
VII THE STUDY OF ZOOI.OOY 217 
 
 afforded by the method of teaching anatomy, in 
 use in the medical schools. This method con- 
 sists 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 ara sure, may be 
 effected to a far greater extent by the oral dis- 
 course 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, lectures afford the student the oppor- 
 tunity of seeking 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 
 carefully and fully ; strive to understand them 
 thoroughly; come to me for the explanation of 
 anything 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 delivery; 
 and the teacher should always recollect that his 
 business is to feed, and not to cram the intellect. 
 
218 THE STUDY OF ZOOLOPxY vn 
 
 Indeed, I believe that a student who gains 
 from a course of lectures the simple habit of 
 concentrating his attention upon a definitely 
 limited series of facts, until they are thoroughly 
 mastered, has made a step of immeasurable 
 importance. 
 
 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 
 science as an educational agent, it is because 
 the study of any branch of science, if properly 
 conducted, 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 train- 
 ing other than a very prominent branch of 
 education : indeed, I wish that real literary dis- 
 cipline 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 
 scientific, training. 
 
 Seeking for the cause of this difference, I 
 imagine 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 
 
VII THE STUDY OF ZOOLOOY 219 
 
 distinct, and the study of things, and not of 
 books, is the source of the latter. 
 
 All that literature has to bestow may be obtained 
 by reading and by practical exercise in writing 
 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 bestows, 
 whether as training or as knowledge, is dependent 
 ujjon 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 acquiring 
 through his senses concrete images of those pro- 
 perties of things, which are, and always will be, 
 but approximatively expressed in human language. 
 Our wajr of looking at Nature, and of speaking 
 about her, varies from year to j'ear; but a fact 
 once seen, a relation of cause and effect, once 
 demonstrativel}' apprehended, are possessions 
 which neither change nor pass away, but, on the 
 contrary, form fixed centres, about which other 
 truths aggregate by natural afiinity. 
 
 Therefore, the great business of the scientific 
 teacher is, to imprint the fundamental, irrefragable 
 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 complete 
 a manner, that every term used, or law enunciated, 
 should afterwards call up vivid images of the 
 
220 THE STUDY OF ZOOLOGY vn 
 
 particular structural, or other, facts which furnished 
 the demonstration of the law, or the illustration 
 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 effectual zoological 
 demonstrations. The dissection of animals is not 
 altogether pleasant, and requires much time ; nor 
 is it easy to secure an adequate supply of the 
 needful specimens. The botanist has here a 
 great advantage ; his specimens are easily ob- 
 tained, are clean and wholesome, and can be 
 dissected in a private house as well as anywhere 
 else ; and hence, I believe, 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 scieilce is to be properly studied, 
 demonstration, and, consequently, dissection, must 
 be had. Without it, no man can have a really 
 sound knowledge of animal organisation. 
 
 A good deal may be done, however, without 
 actual dissection on the student's part, by demon- 
 stration upon specimens and preparations ; and in 
 
VII THE STUDY OF ZOOLOGY 221 
 
 all probability it would not be very difficult, were 
 the demand sufficient, to organise collections of 
 such objects, sufficient for all the purposes of 
 elementary 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 ornithological gallery at 
 the British Museum contains 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 ornithologist has 
 ever gathered much information from the col- 
 lection. Certainly, no one of the tens of thousands 
 of the general public who have walked through 
 that gallery ever knew more about the essential 
 pecuharities of birds when he left the gallery 
 than when he entered it. But if, somewhere in 
 that vast hall, there were a few preparations, 
 exempUfying the leading structural pecuharities 
 and the mode of development of a common fowl ; 
 if the types of the genera, the leading modifica- 
 tions in the skeleton, in the plumage at various 
 
222 THE STUDY OF ZOOLOGY vn 
 
 ages, in the mode of nidification, and the like, 
 among birds, were displayed ; 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 access to them, I can conceive 
 that this collection might become a great instru- 
 ment of scientific education. 
 
 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 know- 
 ledge of this, or any other branch of physical 
 science ? What is the use, it is said, of attempt- 
 ing to make physical science a branch of primary 
 education ? Is it not probable that teachers, in 
 pursuing such studies, will be led astray from the 
 acquirement of more important but less attractive 
 knowledge ? And, even if they can learn some- 
 thing of science without prejudice to their useful- 
 
VII THE STUDY OF ZOOLOGY 223 
 
 ness, 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 commonly 
 asked, for they arise from that profound ignorance 
 of the value and true position of physical science, 
 which infests the minds of the most highly edu- 
 cated 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 wiU 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 
 
224 THE STUDY OF ZOOLOGY vii 
 
 ask, 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 
 languages, in order that he may have access to 
 infinitely wider stores of knowledge than could 
 ever be opened to him by oral intercourse with his 
 fellow men ; he learns to write, that his means of 
 communication with the rest of mankind may be 
 indefinitely 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 
 
Til THE STUDY OF ZOOLOGY 225 
 
 make his life that which it ought to be, a con- 
 tinual progress in learning and in wisdom. 
 
 But, in addition, primary education endeavours 
 to fit a boy out with a certain equipment of 
 positive knowledge. He is taxight 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 
 excellent, 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 Eoman 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 Roman boy, who had 
 finished 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 unfamiliar 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. 
 
 VOL, VIII Q 
 
226 THE STUDY OF ZOOLOGY vil 
 
 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 un- 
 consciously impregnated with her spirit, and in- 
 debted 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 ultimate court of appeal is observation and 
 experiment, and not authority ; she is teaching it 
 to estimate the value of evidence ; she is creating 
 a firm and living faith in the existence of immut^ 
 able moral and physical laws, perfect obedience to 
 which is the highest possible aim of an intelligent 
 being. 
 
VII THE STUDY OF ZOOLOGY 227 
 
 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 
 bom. The modem 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 
 science 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, 
 however 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 miist first 
 
 Q 2 
 
228 THE STUDY OF ZOOLOGY vil 
 
 know; and real knowledge in science means 
 personal acquaintance with, the facts, be they 
 few or many.^ 
 
 1 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 acquaintance 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. Circumstances, 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 own know- 
 ledge, 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 information on. The scientific 
 virus, like vaccine lymph, if passed through too long a succes- 
 sion of organisms, will lose all its effect in protecting the young 
 against the intellectual epidemics to which they are exposed. 
 
 [The remarks on p. 222 applied to the Natural History Collec- 
 tion of the British Museum in 1861. The visitor 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 FOR THE ADVANCEMENT OF SCIENCE 
 
 FOE 1870) 
 
 It has long been the custom for the newly 
 installed 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 
 important 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-continued siege had n^ade no progress. 
 
230 BIOGENESIS AND ABIOGENESIS vill 
 
 1 propose to endeavour to follow this ancient 
 precedent, in a manner suited, to the limitations of 
 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 
 patient and laborious investigators, of the 
 thought which arose, more than two centuries 
 ago, in the mind of a sagacious and observant 
 Italian naturahst. 
 
 It is a matter of everyday experience that it is 
 difficult to prevent many articles of food from 
 becoming 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 
 vessel, sooner or later becomes turbid and fuU 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 
 
VIII BIOGENESIS AND ABIOGENESIS 231 
 
 life were generated in the matters in which they 
 made their appearance. Lucretius, 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 outbursts of his 
 fervid eloquence : — 
 
 " Thou fool, that which thou sowest is not 
 quickened, except it die."^ 
 
 The proposition that life may, and does, proceed 
 from that which has no life, then, was held alike 
 by the philosophers, the poets, and the people, of 
 
 ' It is thus that Mr. Munro renders 
 
 "Linquitur, ut merito maternum nomen adepta 
 Terra sit, ■) terra quoniam sunt cuncta areata. 
 Multaque nunc etiam exsistant animalia terris 
 Imbribus et calido solis concreta vapore." 
 
 De Merum 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 vapours 
 raised by the sun " ? - \ Corinthians xv. 36, 
 
232 BIOGENESIS AND ABIOGENESIS viii 
 
 the most enlightened nations, eighteen hundred 
 years ago ; and it remained the accepted doctrine 
 of learned and unlearned Europe, through the 
 Middle Ages-, down even to the seventeenth 
 century. 
 
 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 venerable 
 authority in this, as in other matters ; but I can 
 discover no justification for this widespread 
 notion. After careful search through the " Exer- 
 citationes de Generatione," the most that appears 
 clear to me is, that Harvey believed all animals 
 and plants to spring from what he terms a " prim- 
 ordium vegetale" a phrase which may nowadays 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 Qgg, but 
 because it has the constitution and nature of one. 
 That this " immordium oviforme " must needs, in 
 all cases, proceed from a living parent is nowhere 
 expressly maintained by Harvey, though such an 
 opinion may be thought to be implied 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 concern of Harvey's 
 
 ' See the following passage in Exereitatio I. : — "Item sponU 
 nascentia dicuntur ; non quod ex putredine oriunda sint, sed 
 quod easu, natures sponte, et sequivood (ut aiunt) generatione, a 
 
Tin BIOGENESIS AND ABIOGENESIS 233 
 
 wonderfial little treatise is not with generation, in 
 the physiological sense, at all, but with develop- 
 ment ; 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 import- 
 ant part of his scientific education. And it was 
 a student trained in the same schools, Francesco 
 Redi — a man of the widest knowledge and most 
 versatile abilities, distinguished alike as scholar, 
 poet, physician, and naturalist — who, just two 
 hundred and two years ago, published his " Esper- 
 ienze intorno alia Generazione degl' Insetti," and 
 gave to the world the idea, the growth of which it 
 is my purpose to trace. Redi's book went through 
 five editions in twenty years; and the extreme 
 
 parentibus sui dissimilitus proveniant." Again, in Do Uteri 
 Memhranis : — "In cunctorum viventium generatione (sicnt 
 diximus) hoc .solenne est, ut ortum ducunt a primordio aliquo, 
 quod turn materiam turn efficiendi potestatem in se habet : 
 sitque adeo id, ex qno et a quo quicquid nascitur, ortum suum 
 ducat. Tale primordium in animalibus (sive ab aliis gcnerantibus 
 proveniant, sive sponte, aut ex putredine nasocntur) est humor 
 in tnnicS aliqua aut putami ne conclusus." Compare also 
 ■what Redi has to say respecting Harvey's opinions, Esperienze, 
 p. 11. 
 
234 BIOGENESIS AND ABIOGENESIS vill 
 
 simplicity of his experiments, and the clearness 
 of his arguments, gained for his views, and 
 for their consequences, almost universal accept- 
 ance. 
 
 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 appearance, while the dead substances, never- 
 theless, putrefy just in the same way as before. 
 It is obvious, therefore, that the maggots are not 
 generated by the corruption of the meat ; and that 
 the cause of their formation must be a some- 
 thing which is kept away by gauze. But gauze 
 will not keep away aeriform bodies, or fluids. 
 This something 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, therefore, is un- 
 
VIII BIOGENESIS AND ABIOGENESIS 235 
 
 avoidable ; the maggots are not generated 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 
 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 aU 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.^ 
 
 ^ ' ' Pure contentandomi sempre in questa ed in ciascuna altro 
 cosa, da oiascuno piu savio, Ih, dove io difettuosamente parlassi, 
 esser corretto ; non tacero, che per molte osservazioni molti volti 
 da me fatte, mi sento inclinato a credere che la ten'a, da quelle 
 prime piante, e da quei primi animali in poi, che ella nei primi 
 giorni del mondo produsse per comandemento del sovrano ed 
 omnipotente Fattore, non abbia mai piii prodotto da se medesima 
 lie erba nk albero, ne animale alcuno pcrfetto o imperfetto che 
 ei se fosse ; e che tutto quello, che ne' tempi trapassati e nato 
 e che ora nascere in lei, o da lei veggiamo, venga tutto dalla 
 semenza reale e vera delle piante, e degli animali stessi, i quali 
 col mezzo del proprio seme la loro spezie conservano. E se bene 
 tutto giorno scorghiamo da' cadaveri degli animali, e da tutte 
 quante le maniere dell' erbe, e dc' fiori, e dei fratti imputriditi, 
 e corrotti nascere vermi infiniti — 
 
 ' Nonne vides qucecnnque moi-a, fluidoque calore 
 
 Corpora tabescunt in parva animalia verti ' — 
 
 Io mi sento, dico, inclinato, a credere che tutti quei vermi si 
 
236 BIOGENESIS AND ABIOGENESIS vm 
 
 And 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 Hving 
 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 
 living 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 Redi 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 
 
 generino dal seme paterno ; e che le carni, e 1' eibe, e 1' altre 
 cose tutte putrefatte, o putrefattibili non facciano altra parte, 
 nk abbiano altro ufizio nella generazione degl' insetti, se non 
 d'apprestare un luogo o un nido proporzionato, in cui dagli 
 animali nel tempo della figliatura sieno portati, c partoriti i 
 vermi, o 1' nova o 1' altre semenze dei vermi, i quali tosto chc 
 nati sono, trovano in esso nido un sufficiente alimento abilissimo 
 per nutricarsi : e se in quelle non son portate dalle madri queste 
 suddette semenze, niente mai, e replicatamente niente, vis'in- 
 gegneri e nasca." — Kedi, Esperieme, pp. 14-16. 
 
 ^ " Molti, e molti altri ancora vi potrei annoverare, se non 
 fossi chiamato a rispondere alle rampogne di alcnni, che brusca- 
 mente mi rammentano ci6, che si legge nel capitolo quattor- 
 dicesimo del sacrosanto Libre de' giudici. . . . " — Redi, loc. cit. 
 p. 45. 
 
VIII BIOGENESIS AND ABIOGENESIS 237 
 
 the generation of bees from the carcase of a dead 
 lion is afifirmed, in the Book of Judges, to have 
 been the origin of the famous riddle with which 
 Samson perplexed the Philistines : — 
 
 " Out of the eater came forth meat, 
 And out of the strong came forth sweetness. 
 
 Against all odds, however, Redi, 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 Redi'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 
 generated 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 
 
238 BIOGENESIS AND ABIOGENESIS vill 
 
 of parasites within the animal body in the same 
 
 way.i 
 
 1 The passage (Sspericnze, p. 129) is worth quoting in full :— 
 " Se dovessi palesarvi il mio sentimento crederei che i frutti, 
 i leguml, gli alberi e le foglie, in due nianiere inverminassero. 
 Una, perchfe venendo i bachi per di fuora, e cercando 1' alimento, 
 col rodere ci aprono la strada, ed arrivano alia piii interna 
 midoUa de' frutti e de' legni. L'altra maniera si t, che io per 
 me stimerei, che non fosse gran fatto disdicevole il credere, che 
 quell' anima o quella virtu, la quale genera i fieri ed i frutti 
 nelle piante viventi, sia quella stessa che generi ancora i bachi 
 di esse piante. E chi sk forse, che molti frutti degli alberi non 
 sieno prodotti, non per un fine primario e principale, ma bensi 
 per un ufBzio secondario e servile, destinato alia generazione^ di 
 que' vermi, servendo a loro in vece di matrice, in cui dimorino 
 un prefisso e determinato tempo ; il quale arrivato escan fuora a 
 godere il sole. 
 
 " Io m' immagino, che questo mio pensiero non vipan-a total- 
 mente un paradosso ; mentre farete riflessione a quelle tante 
 sorte di galle, di gallozzole, di coccole, di ricci, di calici, di 
 cornettiedi lappole, che son produtte daUe quercel, dalle farnie, 
 da' cerri, da' suyheri, da' lecci e da altri simili alberi da ghianda ; 
 imperciocche in quelle gallozzole, e particolarmente nelle pii 
 grosse, che si chiamano coronati, ne' rioci capelluti, che ciuffoli 
 da' nostri contadini son detti ; nei ricci legnosi del cerro,_ ne' 
 ricci stellati della querela, nelle galluzze della foglia del leccio si 
 vede cvidentissimamente, che la prima e principale intenzione 
 della natura e fonnare dentro di quelle un animale volante ; 
 vedendosi nel centre della gallozzola un novo, che col crescere e col 
 maturarsi di essa gallozzola va crescendo e maturando anch' 
 egli, e cresce altresi a suo tempo quel verme, che nell' novo si 
 racchiude ; il qual verme, quando la gallozzola e finita di matu- 
 rare e che e venuto il termine destinato al suo nascimento, 
 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, opor dir meglio 
 sospettava, che forse la gallozzola nascesse, perche arrivando la 
 mosca nel tempo della primavera, e facendo una piccolissima 
 fessura ne' rami piu teneri della querela, in quella fessura nas- 
 condesse uno de suoi semi, il quale fosse cagione che sbocoiasse 
 fuora la gallozzola ; e die mai non si vedessero gaUe o gallozzole 
 o rioci cornetti o calici o coccole, se non in que' rami, ne' quali 
 le mosche avessero depositate le loro semenze ; e mi dava ad 
 intendcre, che le gallozzole fossero una malattia cagionata nelle 
 
VIII BIOGENESIS AND ABIOGENESIS 239 
 
 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- 
 genesis as against Ahiogenesis ; and I shall imme- 
 diately proceed, in the first place, to inquire how 
 far subsequent investigation has borne him out in 
 so doing. 
 
 But Redi also thought that there were two 
 modes of Biogenesis. By the one method, which 
 is that of common and ordinary occurrence, the 
 living parent gives rise to offspring which passes 
 through the same cycle of changes as itself — Hke 
 gives rise to like; and this has been termed 
 Homogenesis. By the other mode, the living 
 parent was supposed to give rise to offspring 
 which passed through a totally dilferent 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 off- 
 spring being altogether, and permanently, unlike 
 the parent. The term Heterogenesis, however, 
 has unfortunately been used in a different sense, 
 and M. Milne-Edwards has therefore substituted 
 for it Xenogenesis, which means the generation of 
 something foreign. After discussing Redi's hypo- 
 thesis of universal Biogenesis, then, I shall go 
 
 querce dalle punture delle mosche, in quella giusa stessa che 
 dalle pmituie d' altri animaletti simiglievoli veggiamo crescere 
 de' tumori ne' coi'pi degli animali." 
 
240 BIOGENESIS AND ABIOGENESIS vill 
 
 on to ask how far the growth of science justifies 
 his other hypothesis of Xenogenesis. 
 
 The progress of the hypothesis of Biogenesis 
 was triumphant and unchecked for nearly a 
 century. The appKcation of the microscope to 
 anatomy in the hands of Grew, Leeuwenhoek, 
 Swammerdam, Lyonnet, ValHsnieri, Rdaumur, and 
 other illustrious investigators of nature of that 
 day, displayed such a complexity of organisation 
 in the lowest and minutest forms, and everywhere 
 revealed 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 
 universally 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'ostivre of the opticians of that day; and, at the 
 same time, by no means trustworthy. But a 
 magnifying power of 400 diameters, even when 
 
 ' Needham, writing in 1750, says : — 
 
 ' ' Les naturalistes modernes s'acoordent unaninement h, etablir, 
 comme une verite certaine, que toute plante vient de sa semence 
 specifique, tout animal d'un oeuf ou de quelque chose d'analogue 
 preexistant dans la plante, ou dans I'animal de meme espece qui 
 I'a ^mAmV—Nouvellas Observations, p. 169. 
 
 "Les naturalistes ont generalemente cru que les animaux 
 microscopic^ues ^^taient engendres par des oeufs transportes dans 
 I'air, ou deposes dans des eaux dormantes par des insectes 
 volans." — Ibid. p. 176, 
 
VIII BIOaENESIS AND ABIOGENESIS 241 
 
 definition reaches the exquisite perfection of our 
 modem achromatic lenses, hardly sufiices for the 
 mere discernment of the smallest forms of life. 
 A speck, only -^th of an inch in diameter, has, at 
 ten inches from the eye, the same apparent size 
 as an object loo oo ^^ of ^ii 1^"^^ iii diameter, 
 when magnified 400 times; but forms of living 
 matter abound, the diameter of which is not more 
 than ijji-^Tjih. 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 ^^Vs-th of an inch, is a giant. 
 It is only by bearing these facts in mind, that we 
 can deal fairly with the remarkable statements 
 and speculations put forward by Buffon 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 
 smallest things of which I have spoken, and 
 which must have looked like mere dots and lines 
 under the ordinary microscopes of the eighteenth 
 century. 
 
 Led by various theoretical considerations which 
 
 VOL. VIII R 
 
242 BIOGENESIS AND ABIOGENESIS vill 
 
 I cannot now discuss, but which looked promising 
 enough in the lights of their time, Buffon and 
 Needham doubted the applicability of Redi's 
 hypothesis to the infusorial animalcules, and 
 Needham 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 sub- 
 stance infused, 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 care- 
 fully, 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 animalcules 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 experi- 
 ments, animalcules always did arise in the 
 infusions, when a sufficient time had elapsed to 
 allow for their development. 
 
 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 
 
■nil BIOGENESIS AND ABIOGENESIS 243 
 
 to which, life is the indefeasible property of certain 
 indestructible molecules of matter, which exist 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 
 organism 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 nothing 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 animal, or of a plant, is merely 
 the breaking up of the form, or manner of asso- 
 ciation, of its constituent organic molecules, which 
 are then set free as infusorial animalcules. 
 
 It will be perceived that this doctrine is by no 
 means identical with Aiiogcncsis, with which it is 
 often confounded. On this hypothesis, a piece of 
 beef, or a handful of hay, is dead only in a Hmited 
 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 
 
 E 2 
 
244 BIOGENESIS AND ABIOGENESIS viil 
 
 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 
 before 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 Abb^ Spallanzani, a 
 worthy successor and representative of Redi in his 
 acuteness, his ingenuity, and his learning, sub- 
 jected the experiments and the conclusions of 
 Needham 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 arguments ? 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 
 second place, that he had not sufiiciently heated 
 his infusions and the superjacent air ? Spallan- 
 zani 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 
 
VIII BIOGENESIS AND ABIOGENESIS 245 
 
 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, 
 imphcitly 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 
 respiration, and to an examination of the marvel- 
 lous 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 
 animalcules 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 Spallanzani's experiments ? What security 
 was there that the development of life which ought 
 ^ See Spallanzani, Opere, vi. pp. 42 and 51. 
 
246 BIOGENESIS AND ABIOGENESIS viii 
 
 to have taken place had not been checked or pre- 
 vented by these changes ? 
 
 The battle had to be fought again. It was need- 
 ful 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 propor- 
 tion 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 in- 
 fusion should be such as had either passed through 
 red-hot tubes or through strong sulphuric acid. 
 The result which they obtained was that an in- 
 fusion 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 
 alternately denied and aflSrmed. Supposing them 
 to be accepted, however, all that they really proved 
 was that the treatment to which the air was 
 subjected destroyed something that was essential 
 to the development of life in the infusion. This 
 " something '' might be gaseous, fluid, or solid ; 
 
vm BIOGENESIS AND ABIOGENESIS 247 
 
 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 com- 
 posed of a vast accumulation of minute plants. 
 The fermentation of must, or of wort, in the 
 fabrication of wine and of beer, is always accom- 
 panied by the rapid growth and multiplication of 
 these Torulce. Thus, fermentation, in so far as it 
 was accompanied by the development of micro- 
 scopical organisms in enormous numbers, became 
 assimilated to the decomposition of an infusion of 
 ordinary animal 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 
 attaining to high eminence alike in Mathematics, 
 Physics, and Physiology — I speak of the illustrious 
 Helmholtz — reduced the matter to the test of 
 experiment by a method alike elegant and con- 
 clusive. Helmholtz separated a putrefying or a 
 fermenting liquid from one which was simply 
 putrescible 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 putrescible or the 
 
248 BIOGENESIS AND ABIOGENESIS vill 
 
 fermentable liquids became impregnated with the 
 results of the putrescence 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 fermenting or putrefying liquid 
 generated in them. Therefore the cause of the 
 development of these organisms must lie in some- 
 thing which cannot pass through membranes ; and 
 as Helmholtz's investigations were long antecedent 
 to Graham's researches upon colloids, his natural 
 conclusion was that the agent thus intercepted 
 must be a solid material. In point of fact, 
 Helmholtz's experiments narrowed the issue to 
 this : that which excites fermentation and putre- 
 faction, and at the same time gives rise to living 
 forms in a fermentable 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 particles. 
 
 The researches of Schroeder and Duschin 1854, 
 and of Schroeder alone, in 1859, cleared up this 
 point by experiments which are simply refine- 
 ments upon those of Redi. A lump of cotton-wool 
 is, physically speaking, a pile of many thicknesses 
 of a very fine gauze, the fineness of the meshes of 
 which depends upon the closeness of the compres- 
 sion of the wool. Now, Schroeder and Dusch 
 found, that, in the case of all the putrefiable 
 materials which they used (except milk and yolk 
 
VIII BIOGENESIS AND ABIOGENESIS 249 
 
 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 
 minute solid particles. Still the evidence was 
 incomplete until it had been positively shown, 
 first, that ordinary air does contain such particles ; 
 and, secondly, that filtration through cotton-wool 
 arrests these particles and allows only physically 
 pure air to pass. This demonstration has been 
 furnished within the last year by the remarkable 
 experiments of Professor Tyndall. It has been a 
 common objection of Abiogenists that, if the 
 doctrine of Biogeny is true, the air must be thick 
 with germs ; and they regard this as the height of 
 absurdity. 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 
 destructible particles, there really do exist germs 
 capable of giving rise to the development of living 
 
250 BIOGENESIS AND ABIOGENESIS viii 
 
 forms in suitable menstrua. This piece of work was 
 done by M. Pasteur in those beautiful researches 
 which will ever render his name famous; and 
 which, in spite of all attacks upon them, appear 
 to me now, as they did seven years ago,^ to he 
 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 exam- 
 ination 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 gernos were competent to give rise to living 
 forms by simply sowing them in a solution fitted 
 for their development. 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 eflfected in the constituents of the air by 
 the wool, by proving that the cotton-wool might 
 be dispensed with altogether, and perfectly free 
 access left between the exterior air and that in the 
 experimental flask. If the neck of the flask is 
 dra\\"n out into a tube and bent downwards ; and 
 
 • Lectures to Working Men on the Causes of the Phenomena of 
 Organic Nature, 1863. (See Vol. II. of these Essays.) 
 
VIII BIOGENESIS AND ABIOGENESIS 251 
 
 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 between 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 cannot fall upwards, and 
 there are no currents, they never reach the interior 
 of the flask. But if the tube be broken short ofl 
 where it proceeds from the flask, and free access 
 be thus given to germs falling vertically out of 
 the air, the fluid, which has remained 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 similar 
 results ; but as it contains organic matter, the argument which 
 follows cannot be based upon it. 
 
252 BIOGENESIS AND ABIOGENESIS vill 
 
 quarter of an hour ; and, while the steam is passing 
 out, stop the neck 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 consequently 
 full of the active and excessively minute organisms 
 known as Bacteria. In a couple of days of ordinary 
 warm weather the contents of this flask will be 
 milky from the enormous multiplication of Bacteria. 
 The other flask, open and exposed to the air, will, 
 sooner or later, become milky with Bacteria, 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 explanation 
 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 solution has 
 been knowingly and purposely inoculated, and to 
 the moviH-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 in- 
 fluence but that of free access of air and the ordinary 
 temperature, re-arrange themselves and give rise 
 to the protoplasm of Bacterium. But the alterna- 
 tive is to admit that these Bacteria arise from 
 germs in the air ; and if they are thus propagated, 
 
vm BIOGENESIS AND ABIOGENESIS 253 
 
 the burden of proof that other like forms arc 
 generated in a different manner, must rest with 
 the assertor of that proposition. 
 
 To sum up the effect of this long chain of 
 evidence : — 
 
 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 Hving 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 un- 
 purified 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 
 particles are so minute that the assumption of 
 their suspension in ordinary air presents not the 
 slightest difficulty. On the contrary, considering 
 their hghtness and the wide diffusion of the 
 organisms which produce them, it is impossible to 
 
254 BIOGENESIS AND ABIOGENESIS vill 
 
 conceive that they should not be suspended in the 
 atmosphere in myriads. 
 
 Thus the evidence, direct and indirect, in favour 
 of Biogenesis for all known forms of life must, I 
 think, be 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-con- 
 tinued heat, have sometimes exhibited living 
 forms of low organisation when they have been 
 opened. 
 
 The first reply that suggests itself is the prob- 
 ability that there must be some error about these 
 experiments, because they are performed on an 
 enormous scale every day with quite contrary 
 results. Meat, fruits, vegetables, the very ma- 
 terials 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 Spallan- 
 zani'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 neces- 
 sary, for either fermentation or putrefaction. It 
 is not because the tins are exhausted of air, for 
 
VIII BIOGENESIS AND ABIOGENESIS 255 
 
 Vihriones and Bacteria live, as Pasteur has shown, 
 without air or free oxygen. It 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 
 experiments I refer to are really trustworthy, it 
 by no means follows that Abiogenesis 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 medium. 
 But if, in the present state of science, the alter- 
 native is offered us, — either germs can stand a 
 greater heat than has been supposed, or the mole- 
 cules of dead matter, for no valid or intelligible 
 reason that is assigned, are able to re-arrange 
 themselves into living bodies, exactly such as can 
 be 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 mji-self 
 against the supposition that I intend to suggest 
 that no such thing as Abiogenesis ever has taken 
 
256 BIOGENESIS AND ABIOGENESIS vill 
 
 place in the past, or ever will take place in 
 the future. With organic chemistry, molecular 
 physics, 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, be artificially brought together. All I 
 feel justified in affirming is, that I see no reason 
 for believing 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 permissible where behef is 
 not ; and if it were given me to look beyond the 
 abyss of geologically recorded time to the still 
 more remote period when the earth was passing 
 through physical and chemical conditions, which 
 it can no more see again than a man can recall 
 his infancy, I should expect to be a witness of the 
 evolution of living protoplasm from not hving 
 matter. I should expect to see it appear under 
 
VIII BIOGENESIS AND ABIOGENESIS 257 
 
 forms of great simplicity, endowed, like existing 
 fungi, with the power of determining the formation 
 of new protoplasm from such matters as ammonium 
 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 
 Redi's great doctrine of Biogenesis, which appears 
 to me, with the limitations I have expressed, to 
 be victorious along the whole line at the present 
 day. 
 
 As regards the second problem offered to us by 
 Redi, 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 sub- 
 stance of these plants, was made out by Vallisnieri, 
 Reaumur, and others, before the end of the first 
 half of the eighteenth century. The tapeworms, 
 
 VOL. VIII s 
 
258 BIOGENESIS AND ABIOGENESIS vm 
 
 bladderworms, and flukes continued to be a 
 strongbold of the advocates of Xenogenesis for a 
 much longer period. Indeed, it is only within the 
 last thirty years that the splendid patience of Von 
 Siebold, Van Beneden, Leuckart, Kiichenmeister, 
 and other helminthologists, has succeeded in 
 tracing every such parasite, often through the 
 strangest wanderings and metamorphoses, to an 
 egg derived from a parent, actually or potentially 
 like itself; and the tendency of inquiries else- 
 where has all been in the same direction. A 
 plant may throw off bulbs, but these, sooner or 
 later, give rise to seeds or spores, which develop 
 into the original form. A polype may give rise 
 to Medusae, or a pluteus to an Echinoderm, 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 VaUisnieri 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 morbid structures are outgrowths. 
 Again, it is a matter of familiar experience to 
 everybody that mere pressure on the skin will 
 give rise to a corn. Now the gall, the tumour, 
 
VIII BIOGENESIS AND ABIOGENESIS 259 
 
 and the com are parts of the living body, which 
 have become, to a certain degree, independent and 
 distinct organisms. Under the influence of cer- 
 tain external conditions, elements of the body, 
 which should have developed in due subordination 
 to its general plan, set up for themselves and 
 apply the nourishment which they receive to their 
 own purposes. 
 
 From such innocent productions as corns and 
 warts, there are all gradations to the serious 
 tumours which, by their mere size and the 
 mechanical obstruction they cause, destroy the 
 organism out of which they are developed ; while, 
 finally, in those terrible structures known as 
 cancers, the abnonnal growth has acquired powers 
 of reproduction and multiplication, and is only 
 morphologically 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 Xeno- 
 genesis 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 "Eeports on the 
 
 s 2 
 
260 BIOGENESIS AND ABIOGENESIS vill 
 
 Public Health," which, in his capacity of their 
 medical ofl&cer, he annually presents to the Lords 
 of the Privy Council. The appendix to this 
 report contains an introductory 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 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 vaccina- 
 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 living particles, which have grown and 
 multiplied where they have been planted ? The 
 observations of M. Chauveau, extended and con- 
 firmed by Dr. Sanderson himself, appear to leave 
 no doubt upon this head. Experiments, similar 
 in principle to those of Helmholtz on fermentation 
 and putrefaction, have proved that the active 
 
VIII BIOGENESIS AND ABIOGENESIS 261 
 
 element in the vaccine lymph is non-diffusible, 
 and consists of minute particles not exceeding 
 2 6 0()oth 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 epizootic diseases, sheep-pox and 
 glanders, are also dependent for their existence 
 and their propagation upon extremely small living- 
 solid particles, to which the title of microeymes is 
 applied. An animal 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 fermenting beer is capable of pro- 
 pagating 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 microzymes 
 the results of Hbmogcnesis, or of Xenogcnesis ? are 
 they capable, hke the Torulm 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 individuaHsation 
 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, 
 
262 BIOGENESIS AND ABIOGENESIS vill 
 
 whether we look at it from a practical or from a 
 theoretical point of view. A parasite may be 
 stamped out by destroying its germs, but a patho- 
 logical product can only be annihilated by 
 removing the conditions which give rise to it. 
 
 It appears to me that this great problem will 
 have to be solved for each zymotic disease 
 separately, for analogy cuts two ways. I have 
 dwelt upon the analogy of pathological modifi- 
 cation, which is in favour of the xenogenetic 
 origin of microzymes ; but I must now speak 
 of the equally strong analogies in favour of the 
 origin of such pestiferous particles 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 
 infectious epidemics, are caused by minute organ- 
 isms. The smut of wheat is a well-known instance 
 of svich 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 
 
VIII BIOGENESIS AND ABIOGENESIS 263 
 
 thrown off in all directions by a minute fungus 
 called JEmpusa muscce, 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 
 is found to exist in the form of minute corpuscles 
 which float in the blood of the fly. These multiply 
 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 
 diseased ones catch this mortal disease, and 
 perish like the others. A most competent 
 observer, M. Cohn, who studied the development 
 of the Umpusa 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 ascertained, that when one of the 
 spores falls upon the body of a fly, it begins to 
 
264 BIOGENESIS AND ABIOGENESIS vill 
 
 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 
 earhest stage of the Empusa. The disease is 
 " contagious," because a healthy fly coming 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" 
 because the spores become scattered about all 
 sorts of matter in the neighbourhood of the slain 
 flies. 
 
 The silkworm has long been known to be 
 subject to a very fatal and infectious disease 
 called the Muscardine. Audouin transmitted it 
 by inoculation. This disease is entirely due to 
 the development of a fungus, Botrytis Bassiana, 
 in the body of the caterpillar ; and its contagious- 
 ness 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 
 
VIII BIOGENESIS AND ABIOGENESIS 265 
 
 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 in- 
 dustries connected with the working up of the 
 raw silk thus produced, is more than I can 
 pretend to estimate. 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 the skin (whence the name of " P^brine " 
 which it has received),- had been noted for its 
 mortality. 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 mul- 
 berry-leaves and for attendance, the cultivator has 
 constantly seen his silkworms perish and himself 
 plunged in ruin; but it means that the looms of 
 
266 BIOGENESIS AND ABIOGENESIS vm 
 
 Lyons have lacked employment, and that, for 
 years, enforced idleness and misery have been 
 the portion of a vast population which, in former 
 days, was industrious and well-to-do. 
 
 In 1858 the gravity of the situation caused the 
 French Academy of Sciences to appoint Com- 
 missioners, 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 Report ^ made by M. de Quatrefages in 1859, 
 it is exceedingly interesting to observe that his 
 elaborate study of the P^brine forced the convic- 
 tion 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 here- 
 ditary, and in being, under some circumstances, 
 contagious as weU as infectious. 
 
 The Italian naturahst, Filippi, discovered in the 
 blood of the silkworms affected by this strange 
 disorder a multitude of cylindrical corpuscles, each 
 about ^irWth 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 
 1 Mudes sitr hs Maladies actuelles dcs Vers A Soie, p. 53. 
 
VIII BIOGENESIS AND ABIOGENESIS 267 
 
 the female moth. But are these corpuscles 
 causes, or mere concomitants, of the disease ? 
 Some naturahsts took one view and some another ; 
 and it was not until the French Government, 
 alarmed by the continued ravages of the malady, 
 and the inefficiency of the remedies which had 
 been suggested, despatched M. Pasteur to study it, 
 that the question received its final settlement ; at 
 a great sacrifice, 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, 
 Pebrine, 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 PanMsto'phytmi 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 
 inherited only on the mother's side. There is 
 not a single one of all the apparently capricious 
 and unaccountable phenomena presented by the 
 Pebrine, but has received its explanation from the 
 fact that the disease is the result of the presence 
 of the microscopic organism, Panliistophyton. 
 
268 BIOGENESIS AND ABIOGENESIS vill 
 
 Such being the facts with rpspect to the P^brine, 
 what are the indications as to the method of pre- 
 venting it ? It is obvious that this depends upon 
 the way in which the Panhistophyton is generated. 
 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 tq,kes 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 it may need the silkworm for its develop- 
 ment 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 previous inves- 
 tigations, 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 success- 
 ful 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 
 
VIII BIOGENESIS AND ABIOGENESIS 269 
 
 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 P^brine. I refer for 
 this evidence to the very striking facts adduced 
 by Professor Lister in his various well-known 
 publications on the antiseptic method of treat- 
 ment. 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 which seem to haunt the very walls 
 of great hospitals, and are, even now, destroying 
 more men than die of bullet or bayonet, are due 
 to the importation 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 Redi. 
 
 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 
 
270 BIOGENESIS AND ABIOGENESIS vin 
 
 smiles and shrugs, practical and serious contempo- 
 raries of Redi and of Spallanzani may have com- 
 mented on the waste of their high abilities in 
 toiling 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 before 
 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 solidly practical men will admit to have 
 value — viz., money and hfe. 
 
 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 Redi'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 Redi's thought in hfe, 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 eradi- 
 cating 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 
 
VIII BIOGENESIS AND ABIOGENESIS 271 
 
 which the total number of deaths from scarlet- 
 fever alone amounted to ninety thousand. That 
 is the return of killed, the maimed and disabled 
 being 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 know- 
 ledge " ; 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 dihgent, 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 CONTEMPORANEITY AND 
 PERSISTENT TYPES OF LIFE 
 
 [1862] 
 
 Merchants occasionally go through a wholesome, 
 though troublesome and not always satisfactory, 
 process which they term " taking stock." After 
 all the excitement of speculation, the pleasure 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 possessions. 
 
 The man of science does well sometimes to 
 imitate 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 
 
IX GEOLOGICAL CONTEMPORANEITY 27S 
 
 Society seems to be an occasion well suited for an 
 undertaking of this kind — for an inquiry, in fact, 
 into the nature and value of the present results 
 of palaeontological investigation ; and the more 
 so, as all those who have paid close attention to 
 the late multitudinous discussions in which 
 palseontology 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 an- 
 atomy, by the investigation of fossil remains. 
 Indeed, the mass of biological facts has been so 
 greatly increased, and the range of biological 
 speculation has been so vastly widened, by the 
 researches of the geologist and palaeontologist, 
 that it is to be feared there are naturalists in 
 existence who look upon geology as Brindley 
 regarded rivers. " Rivers," said the great engineer, 
 " were made to feed canals ; " and geology, some 
 seem to "think, was solely created to advance com- 
 parative anatomy. 
 
 Were such a thought justifiable, it could 
 hardly expect to be received with favour by this 
 assembly. But it is not justifiable. Your favourite 
 science has her own great aims independent of all 
 others ; and if, notwithstanding her steady devotion 
 to her own progress, she can scatter such rich 
 alms among her sisters, it should be remembered 
 
 VOL. VIII T 
 
274 GEOLOGICAL CONTEMPORANEITY ix 
 
 that her charity is of the sort that does not 
 impoverish, but " blesseth him that gives and him 
 that takes." 
 
 Regard the matter as we will, however, the 
 facts remain. Nearly 40,000 species of animals 
 and plants have been added to the Systema 
 Naturae by palseontological research. This is a 
 living population equivalent to that of a new 
 continent in mere number ;. equivalent to that of 
 a new hemisphere, if we take into account the 
 small population 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 
 palaeontological 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 minutiae of 
 osteology, were it not that in such minutiae he the 
 only keys to the most interesting riddles offered 
 by the extinct animal world. 
 
 These assuredly are great and solid gains. Surely 
 it is matter for no small congratulation that in 
 half a century (for palaeontology, though it dawned 
 earlier, came into full day only with Cuvier) a 
 subordinate branch of biology should have doubled 
 the value and the interest of the whole group 
 of sciences to which it belongs. 
 
IX GEOLOGICAL CONTEMPOEANEITY 275 
 
 But this is not all. Allied with geology, 
 paleeontology has established two laws of inestim- 
 able importance : the first, that one and the same 
 area of the earth's surface has been successively 
 occupied by very different kinds of living beings ; 
 the second, that the order of succession established 
 in one locality holds good, approximately, 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 
 correspondence. 
 
 Succession implies time ; the lower members 
 of an undisturbed series of sedimentary rocks are 
 certainly older than the upper; and when the 
 notion of age was once introduced as the equiva- 
 lent of succession, it was no wonder that corres- 
 pondence in succession came to be looked upon as 
 a correspondence in age, or " contemporaneity." 
 And, indeed, so long as relative age only is spoken 
 
 T 2 
 
276 GEOLOGICAL CONTEMPORANEITY ix 
 
 of, correspondence in succession is correspondence 
 in age ; it is relative contemporaneity. 
 
 But it would have been very much better for 
 geology if so loose and ambiguous a word as 
 " contemporaneous " had been excluded from her 
 terminology, and if, in its stead, some term 
 expressing similarity of serial relation, and ex- 
 cluding 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 posi- 
 tion 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 themselves 
 specially with the works of palaeontologists, in fact, 
 will be fully aware that very few, if any, would rest 
 satisfied with such a statement of the conclusions 
 
IX GEOLOGICAL CONTEMPORANEITY 277 
 
 of their branch of biology as that which has just 
 been given. 
 
 Our standard repertories of palaeontology profess 
 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 
 existences ; 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 
 ascertain how far they rest on an irrefragable 
 basis ; or whether, after all, it might not be well 
 for palseontologists 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 some- 
 what more exactly the extent of these pretensions 
 of palajontology. 
 
 Every one is aware that Professor Bronn's " Un- 
 tersuchungen " and Professor Pictet's " Traite de 
 Pal^ontologie " are works of standard authority, 
 familiarly consulted by every working palaeontolo- 
 gist. It is desirable to speak of these excellent 
 books, and of their distiaguished authors, with the 
 utmost respect, and in a tone as far as possible re- 
 moved from carping criticism ; indeed, if they are 
 specially cited in this place, it is merely in justifi- 
 cation of the assertion that the following proposi- 
 
278 GEOLOGICAL CONTEMPOEANEITY ix 
 
 tions, which may be found implicitly, or explicitly, 
 in the works in question, are regarded by the mass 
 of palaeontologists and geologists, not only on the 
 Continent but in this country, as expressing some 
 of the best-established results of palaeontology. 
 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 dur- 
 ing 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 geolo- 
 gical fauna or flora is the sum of all the 
 species of animals or plants which occupied the 
 whole surface of the globe, during one of these 
 epochs. 
 
 The population of the earth's surface was at fu-st 
 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 wanner and, on the whole, somewhat 
 tropical climate, which remained tolerably equable 
 throughout the year. The subsequent distribution 
 of living beings in zones is the result of a gradual 
 
IX GEOLOGICAL CONTEMPORANEITY 279 
 
 lowering of the general temperature, which first 
 began to be felt at the poles. 
 
 It is not now proposed to inquire whether these 
 doctrines are true or false ; but to direct your 
 attention 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 evidence 
 on which those fundamental propositions demand 
 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 
 implies 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. 
 
280 GEOLOGICAL CONTEMI'ORANEITY ix 
 
 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 
 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 any- 
 body 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 moUusk, though 
 all the world knows there were plenty in their 
 time. 
 
 But then it is urged that, though the Devonian 
 rocks in one part of the world exhibit no fossils, 
 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 repUes : the first that the 
 observational basis of the assertion that the lowest 
 rocks are nowhere fossihferous 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 unfossihferous rocks 
 in question were not only contemjMraneotis in the 
 geological sense, but synchronous in the chronolo- 
 gical sense. To use the alibi illustration again. 
 
tX GEOLOGICAL CONTEMPORANEITY 281 
 
 If a man 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 
 afternoon, the evidence of his absence from both 
 is nil, because he might have been at B in the 
 morning 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 physical 
 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 
 
282 GEOLOGICAL CONTEMPORANEITY ix 
 
 the best authorities that neither similarity of 
 mineral 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, 
 there seems to be no kind of physical evidence 
 attainable of a nature competent to decide 
 whether such deposits were formed simultan- 
 eously, or whether they possess any given differ- 
 ence of antiquity. To return to an example 
 already given : All competent authorities will 
 probably assent to the proposition that physical 
 geology does not enable 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 organic 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 luminously stated, to their logical 
 consequences, may very easily convince them- 
 selves that even absolute identity of organic 
 
IX GEOLOGICAL CONTEMPORANEITY 283 
 
 contents is no proof of the synchrony 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 composition throughout, 
 containing the same organic remains, 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 
 distant formations was 2Jriin& 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 occupied 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 
 possibly afford any proof of the synchrony of 
 the deposits which contain them ; on the con- 
 trary, it is demonstrably compatible with the 
 lapse of the most prodigious intervals of time, 
 and with the interposition of vast changes in the 
 organic and inorganic worlds, between the epochs 
 in which such deposits were formed. 
 
284 GEOLOGICAL CONTEMPORANEITY IX 
 
 On what amount of similarity of their faunae 
 is the doctrine of the contemporaneity of the 
 European and of the North American Silurians 
 based ? In the last edition of Sir Charles Lyell's 
 "Elementary 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 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 number 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 ajiother dip 
 beneath the sea and has come up again, some 
 geologist apphes 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. Keasoning 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 unpre- 
 cedented extent, separate the two. 
 
 But if it be a demonstrable fact that strata 
 containing more than 60 or 70 per cent, of species 
 
IX GEOLOGICAL CONTEMPORANEITY 285 
 
 of MoUusca in common, and comparatively close 
 together, 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 contem- 
 poraneity the sole evidence of which is a simi- 
 larity of facies, or the identity of half a dozen 
 species, or of a good many genera ? 
 
 And yet there is no better evidence for the 
 contemporaneity assumed by all who adopt the 
 hypothesis of universal faunae and florae, of a 
 universally 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 palaeonto- 
 logy, possesses 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 
 series of sedimentary deposits, the bed which lies 
 lowest is the oldest. In many other vertical 
 linear sections of the same series, of course, cor- 
 responding beds will occur in a similar order; 
 but, however 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 
 
286 GEOLOGICAL CONTEMPORANEITY ix 
 
 be synchronous or strictly contemporaneous ; and 
 there are multitudes of accessory circumstances 
 which may fully justify the assumption of such 
 syBchrony. But the moment the geologist has 
 to' deal with large areas, or with completely 
 separated deposits, the mischief of confounding 
 that " homotaxis " or " similarity of arrangementj" 
 which can be demonstrated, with " s3mchrony " or 
 "identity of date," for which there is not a 
 shadow of proof, under the one common term 
 of " contemporaneity " becomes incalculable, and 
 proves the constant source of gratuitous specu- 
 lations. 
 
 For an3rthing that geology or paleontology are 
 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 Palaeozoic 
 epoch as at present, and those seemingly sudden 
 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 
 provable" — must be recorded against all the 
 grand hypotheses of the palaeontologist respecting 
 the general succession of life on the globe. The 
 
IX GEOLOGICAL CONTEMPORANEITY 287 
 
 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 themselves to the geological student, essenti- 
 ally insoluble ? Is he in the position of a scientific 
 Tantalus — 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 palaeontologist. 
 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 
 guidance, will be securely threaded by the clue 
 furnished 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 
 result 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 
 science term a natural law. Whether such a law 
 
288 GEOLOGICAL CONTEMPORANEITY ix 
 
 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 super- 
 natural power has thought fit to act, is a secondary 
 question, 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 philosopher who, believing in that possi- 
 bility, and having watched the gigantic strides 
 of the biological 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 
 unvarjdng order of that great chain of causes and 
 effects of which all organic 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 successive populations of 
 the globe, which so many 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 geo- 
 logists for the last thirty years.; and if, at the 
 present time, it has seemed desirable to give them 
 more definite and systematic expression, it is be- 
 cause palaeontology is every day assuming a greater 
 importance, and now requires to rest on a basis 
 
IX GEOLOGICAL CONTEMPORANEITY 289 
 
 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 palaeontology 
 now possesses, it may be instructive, assuming 
 for the nonce the general correctness of the 
 ordinary hypothesis of geological contemporaneity, 
 to consider whether the deductions which are 
 ordinarily drawn from the whole body of palse- 
 ontological 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 have 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 palaeontology, 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 
 
 ^ " Le plus grand service qii'on pnisse rendre a la science est 
 d'y faire place.nette avant d'y rien constmire. " — Cuvibk. 
 
 •^ Anniversary Address for 1851, Quart. Journ. Gcol. Soe. 
 vol. vii. 
 
 VOL. VIII U 
 
290 GEOLOGICAL CONTEMPORANEITY ix 
 
 something enormous : and indeed they are so, if 
 we regard only the negative differences which 
 separate 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 differ- 
 ences 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 compara- 
 tive anatomist who has made the study of the 
 greater modifications 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 becomes 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 
 fi-om those now living as to require to be arranged 
 even in a sepairate 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 
 
 ^ See Hooter's Introductory Essay to the Flora of Tasmania, 
 p. xxiii. 
 
IX GEOLOGICAL CONTEMPORANEITY 291 
 
 animals so distinct from those now living as to 
 require 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 MoUusca; there are three, the Cystidea, 
 Blastoidea, and Edrioasterida, among the Echino- 
 derms; and two, the Trilobita and Eurypterida, 
 among the 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 Labyrinthodonts ; but there are at least four 
 distinct orders of Reptilia, viz. the Ichthyosauria, 
 Plesiosauria, 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 " Toxo- 
 dontia " being 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 
 supposed ; for, as might be expected from the cir- 
 cumstances of the case, we possess more abundant 
 positive evidence regarding Fishes and marine 
 MoUusks than respecting any other forms of 
 animal life ; and yet these offer us, through the 
 whole range of geological time, no species ordinally 
 
 U 2 
 
292 GEOLOGICAL CONTEMPORANEITY ix 
 
 distinct 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 Reptilia present the extraordinary and excep- 
 tional phenomenon of as many extinct as existing 
 orders, if not more ; the four mentioned maintain- 
 ing their existence from the Lias to the Chalk 
 inclusive. 
 
 Some years ago one of your Secretaries pointed 
 out another kind of positive palseontological 
 evidence tending towards the same conclusion — 
 afforded by the existence of what he termed 
 " persistent 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 
 distinguishable from that of an existing species ; 
 that a true Pinus appears in the Purbecks and a 
 Juglans in the Chalk ; while, from the Bagshot 
 Sands, a Banhsia, the wood of which , is not 
 distinguishable 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 
 
 ^ See the abstract of a Lecture ' ' On the Persistent Types of 
 Animal Life," in the Notices of tlie Meetings of the Boyal 
 Institution of Great Britain. — June 3, 1859, vol. iii. p. 151. 
 
IX GEOLOGICAL CONTEMPORANEITY 293 
 
 even the families of the Aporosa were all repre- 
 sented in the older Mesozoic rocks. 
 
 Among the Mollusca similar facts were adduced. 
 Let it be borne in mind that Avicula, Mytilus, 
 Chiton, Natica, Patella, Trochus, Discina, Orhicula, 
 Lingula, Rhynchonella, 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 Cephalopods 
 are represented in the Lias by a genus Belemno- 
 teuthis, which presents the closest relation to the 
 existing Loligo. 
 
 The two highest groups of the Annulosa, the 
 Insecta and the Arachnida, are represented in the 
 Coal, either by existing genera, or by forms 
 differing from existing genera in quite minor 
 peculiarities. 
 
 Turning to the Vertebrata, the only palaeozoic 
 Elasmobranch Fish of which we have any complete 
 knowledge is the Devonian and Carboniferous 
 PleuracantMis, which differs no more from existing 
 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 adduced to show that almost all those 
 respecting which we possess sufficient information, 
 are referable to the same sub-ordinal groups as 
 the existing Lejoidosteus, Polypterus, and Sturgeon ; 
 and that a singular relation obtains between the 
 
294 GEOLOGICAL CONTEMPORANEITY ix 
 
 older and the younger Fishes ; the former, the 
 Devonian Ganoids, being almost all members of 
 the same sub-order as Polypterus, while the 
 Mesozoic Ganoids are almost all similarly allied 
 to Zepidosteus} 
 
 Again, what can be more remarkable than the 
 singular constancy of structure preserved through- 
 out a vast period of time by the family of the 
 Pycnodonts and by that of the true Ccelacanths : 
 the former persisting, with but insignificant 
 modifications, from the Carboniferous to the 
 Tertiary rocks, inclusive ; the latter existing, 
 with still less change, from the Carboniferous 
 rocks to the Chalk, inclusive ? 
 
 Among Eeptiles, 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 
 fecets 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 pro- 
 portions 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- 
 
 1 ' ' Memoirs of the Geological Survey of the United Kingdom. 
 — Decade x. Preliminary Essay upon the Systematic Arrange- 
 ment of the Fishes of the Devonian Epoch." 
 
IX GEOLOGICAL CONTEMPORANEITY 295 
 
 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 positive 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 us, 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 
 modification. 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 
 
296 GEOLOGICAL CONTEMPORANEITY ix 
 
 it may afford a sufficient refutation of many of 
 them. 
 
 The Protozoa. — 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 
 embryonic, or less differentiated, than the existing 
 forms. 
 
 The Ccelenterata. — The Tabulate Corals have 
 existed from the Silurian epoch to the present 
 day, but I am not aware that the ancient Hdiolites 
 possesses a single mark of a more embryonic or 
 less differentiated character, or less high organisa- 
 tion, than the existing ffeliopora. As for the 
 Aporose Corals, in what respect is the Silurian 
 Palceoeyclus less highly organised or more embry- 
 onic 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 palaeozoic Spirifer ; or the existing 
 Bhynchonellm, Cranim, Siscince, Lingulm, than the 
 Silurian species of the same genera? In what 
 sense can LoUgo or Spirula be said to be more 
 
IX GEOLOGICAL CONTEMPORANEITY 297 
 
 specialised, or less embryonic, than Belemnites; 
 or the modern species of Lamelhbranch and 
 Gasteropod genera, than the Silurian species of 
 the same genera ? 
 
 The Annulosa. — The Carboniferous Insecta 
 and Arachnida are neither less specialised, nor 
 more embryonic, than these that now live, nor are 
 the Liassic Cirripedia and Macrura ; while several 
 of the Brachyura, which appear in the Chalk, 
 belong to existing genera; and none exhibit 
 either an intermediate, or an embryonic, 
 character. 
 
 The VertebeATA. — Among fishes I have 
 referred to the CcElacanthini (comprising the 
 genera Ccelacanthus, Holophagus, Undina, and 
 Macropoma) as affording an example of a persistent 
 type; and it is most remarkable to note the 
 smalhiess of the differences between any of these 
 fishes (affecting 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 pecuUar structure, the Macropoma of the 
 Chalk is identical with the Gwlacantlius of the 
 Coal. Look at the genus Lepidotus, again, per- 
 sisting without a modification of importance 
 from the Liassic to the Eocene formations in- 
 clusivly. 
 
 Or among the Teleostei — in what respect is 
 the Beryx of the Chalk more embryonic, or 
 
298 GEOLOGICAL CONTEMPORANEITY ix 
 
 less differentiated, than Beryx lineattis 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 
 Ichthyosauria, Plesiosauria, or Pterosauria less 
 embryonic, 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 
 Zophiodoii, or a Palceothermm, than a modern 
 Tapirus or ITyrax? 
 
 These examples might be almost indefinitely 
 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 
 towards a less embryonic, or less generalised, type 
 in a great many groups of animals of long- 
 continued 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 inconceivable that any theory of a necessarily 
 progressive development can stand, for the numer- 
 ous orders and families cited afford no trace of 
 such a process. 
 
 But it is a most remarkable fact, that, while the 
 
IX GEOLOGICAL CONTEMPORANEITY 299 
 
 groups which have been mentioned, and many 
 besides, 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 seems 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 
 exhibiting a certain increase of complexity in the 
 newer genera. Here, however, one is met at once 
 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 
 towards 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 Actino- 
 criiius and Eucalyptocrinus, for example, depart to 
 the full as widely, in one direction, from the stalked 
 
300 GEOLOGICAL CONTEMPORANEITY ix 
 
 embryo of Oomatula, as Comatula itself does in 
 the other. 
 
 The Echinidea, 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 
 argued, on the other hand, that the spheroidal 
 Echinoids, in reality, depart further from the 
 general plan and from the embryonic form than 
 the elongated Spatangoids do ; and that the 
 pecuHar dental apparatus and the pedicellarise of 
 the former are marks of at least as great differ- 
 entiation as the petaloid ambulacra and semitse of 
 the latter. 
 
 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 Podophthalmia, 
 or from any embryonic condition of the Brachyura, 
 as the Brachyura do in the other ; and that the 
 middle terms between Macrura and Brachyura — 
 the Anomura — are little better represented in the 
 older Mesozoic rocks than the Brachyura are. 
 
 None of the cases of progressive modification 
 which are cited from among the Invertebrata 
 appear to me to have a foundation less open to 
 
IX GEOLOGICAL CONTEMPORANEITY 301 
 
 criticism than these ; and if this be so, no careful 
 reasoner would, I think, be inclined to lay very 
 great stress upon them. Among the Vertebrata, 
 however, 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 ossified, and, so far, less differ- 
 entiated, 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 re- 
 semblances to the existing genus, which possesses 
 biconclave vertebrae, are, for the most part, wholly 
 devoid of ossified vertebral centra. The Mesozoic 
 Lepidosteidse, again, have, at most, biconcave 
 vertebrae, while the existing Lepidostms has 
 Salamandroid, opisthoccElous, vertebrse. So, none 
 of the Palaeozoic Sharks have shown themselves 
 to be possessed of ossified vertebra, while the 
 majority of modern Sharks possess such vertebrae. 
 Again, the more ancient Crocodilia and Lacertilia 
 have vertebrae with the articular facets of their 
 centra flattened or biconcave, while the modern 
 members of the same group have them procoelous. 
 But the most remarkable examples of progressive 
 modification of the vertebral column, in corre- 
 spondence with geological age, are those afforded 
 
302 GKOLOGICAL CONTEMPORANEITT ix 
 
 by the Pycnodonts among fish, and the Labyrin- 
 thodonts among Amphibia. 
 
 The late able ichthyologist Heckel pointed out 
 the fact, that, while the Pycnodonts never possess 
 brue 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 such 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 vertebra. Hermann von Meyer, again, to 
 whose luminous researches we are indebted for 
 our present large knowledge of the organisation of 
 the older Labyrinthodonts, has proved that the 
 Carboniferous Archegosaurus had very imperfectly 
 developed vertebral centra, while the Triassic 
 Mastodonsaurus had the same parts completely 
 ossified.^ 
 
 The regularity and evenness of the dentition of 
 the Anoplotherium, as contrasted with that of exist- 
 ing Artiodactyles, and the assumed nearer approach 
 of the dentition of certain ancient Carnivores to 
 the typical arrangement, have also been cited as 
 exemplifications of a law of progressive develop- 
 ment, but I know of no other cases based on 
 
 ' As this Address is passing through the press (March 7, 
 1862), evidence lies before me of the existence of a new Laby- 
 rinthodont {Pholidogaster), from the Edinburgh coal-field with 
 well-ossified vertebral centra. 
 
IX GEOLOGICAL CONTEMl'OKANErrY 303 
 
 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 progressive 
 modification, which suppose that modification 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 
 demonstrates 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-continued group were more generalised 
 in structure than the later ones. To a certain 
 extent, indeed, it may be said that imperfect 
 ossification of the vertebral column is an em- 
 bryonic character; but, on the other hand, it 
 would be extremely incorrect 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 conception 
 of the nature and the extent of the earliest fauna 
 and flora, the insignificant amount of modification 
 which can be demonstrated to have taken place in 
 any one group of animals, or plants, is quite in- 
 
304 GEOLOGICAL CONTEMPORANEITY ix 
 
 compatible with the hypothesis that all living 
 forms are the results of a necessary process of 
 progressive development, entirely comprised within 
 the time represented by the fossiliferous rocks. 
 
 Contrariwise, any admissible h3rpothesis of pro- 
 gressive modification must be compatible with 
 persistence without progression, through indefi- 
 nite periods. And should such an hypothesis 
 eventually be proved to be true, in the only 
 way in which it can be demonstrated, viz. 
 by observation and experiment upon the 
 existing forms of life, the conclusion will 
 inevitably present itself, that the Paleeozoic 
 Mesozoic, and Cainozoic faunae and florae, taken 
 together, bear somewhat the same proportion to 
 the whole series of living beings which have 
 occupied this globe, as the existing fauna and 
 flora do to them. 
 
 Such are the results of palaeontology as they 
 appear, and have for some years appeared, to the 
 mind of an inquirer who regards that study simply 
 as one of the applications of the great biological 
 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 inclined to 
 think the time wasted which has been spent upon 
 their elaboration. 
 
X 
 
 GEOLOGICAL REFOEM 
 [1869] 
 
 ' ' A great reform in geological speculation seems now to have 
 become necessary. " 
 
 " It is c^uite certain that a great mistake has been made — that 
 British popular geology at the present time is in direct opposi- 
 tion to the principles of Natural Philosophy. " ^ 
 
 In reviewing the course of geological thought 
 during the past year, for the purpose of discovering 
 those matters to which I might most fitly direct 
 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 
 philosopher, rose into such prominence before my 
 mind that they eclipsed everything else. 
 
 It surely is a matter of paramount importance 
 
 ' On Geological Time. By Sir W. Thomson, LL. D. Trans- 
 actioTis of the Geological Society of Glasgow, vol. iii. 
 
 VOL. VIII X 
 
306 GEOLOGICAL REFORM x 
 
 for the British geologists (some of them very- 
 popular geologists too) here in solemn annual 
 session assembled, to inquire 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 prepared 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 
 involve 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 
 position which is, nine times out of ten, occupied 
 by counsel, who nevertheless contrive to gain 
 their causes, mainly by force of mother- wit and 
 common-sense, aided by some training in other 
 intellectual 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, systems 
 of geological thought, each of which might fairly 
 
X GEOLOGICAL EEFOEM 307 
 
 enough claim these appellations, standing side by 
 side in Britaia. I shall call one of them Cata- 
 STROPHISM, another UNiFOEMiTARiANiSM,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 geology " ; and assuredly it has 
 yet many adherents, and reckons among its sup- 
 porters some of the most honoured members of 
 this Society. 
 
 By Uniformitarianism, 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. 
 
 X 2 
 
308 GEOLOGICAL EEFOEM x 
 
 So far as the not-living world is concerned, uni- 
 formitarianism lies there, not only in germ, but in 
 blossom and fruit. 
 
 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 curiously limited, the 
 answer appears 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, ia 
 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 pheno- 
 mena, 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 
 beginniag 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." ^ 
 
 1 The Theory of the Earth, vol. i. p. 178, note. 
 
X GEOLOGICAL REFORM 309 
 
 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 
 world; for this order alone is what we have to 
 reason upon; and to reason without data is 
 nothing but delusion. A theory, therefore, which 
 is limited to the actual constitution of this earth 
 cannot 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 pro- 
 duced, as land, along with masses of melted 
 substances, by the operation of mineral causes." ^ 
 
 But other influences were at work upon Hutton 
 beside those of a mind logical by nature, and 
 scientific by sound training; and the pecuhar 
 turn which his speculations took seems to me 
 to be unintelligible, unless these be taken into 
 account. The arguments of the French astro- 
 nomers and mathematicians, which, at the end 
 of the last century, were held to demonstrate 
 the existence of a compensating arrangement 
 among the celestial bodies, whereby all pertiirba- 
 1 The Theory of the Earth, vol. i. p. 281. = Ibid. p. 371. 
 
310 GEOLOGICAL REFORM j 
 
 tions eventually reduced themselves to oscilla- 
 tions on each side of a mean position, and the 
 stability of the solar system was secured, had 
 evidently taken strong hold of Button'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 Nature there is wisdom, system, and consist- 
 ency. For having, in the natural history of this 
 earth, seen a succession of worlds, we may from 
 this conclude 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 revolu- 
 tions. But if the succession of worlds is estab- 
 lished in the system of nature, it is in vain to 
 look for anything higher in the origin of the 
 earth. The result, therefore, of this physical 
 inquiry is, that we find no vestige of a begiiming, 
 — 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 
 1 The Theory of the Earth, vol. i. p. 200. 
 
X GEOLOGICAL REFORM 311 
 
 been named ban-en virgins, but which might 
 be more fitly termed the hetairce of philosophy, 
 so constantly 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 
 difierent parts are all adapted, in form, in quality, 
 and in quantity, to a certain end; an end at- 
 tained with certainty or success; and an end 
 from which we may perceive wisdom, in contem- 
 plating the means employed. 
 
 " But is this world to be 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 naturally repaired, in the exertion 
 of those productive powers by which it had 
 been formed. 
 
 " This is the view in which we are now to 
 examine the globe ; to see if there be, in the 
 constitution of this world, a reproductive opera- 
 tion, by which a ruined constitution may be 
 again repaired, and a duration or stabiHty thus 
 procured to the machine, considered as a world 
 sustaining plants and animals."^ 
 
 ' TJie Theory of the Earth, vol. i. pp. 16, 17, 
 
Sl2 GEOLOGICAL REFORM x 
 
 Kirwan, and the other Philistines of the day, 
 accused Hutton of declaring that his theory 
 implied that the world never had a beginning, 
 and never differed in condition from its present 
 state. Nothing could be more grossly unjust, as 
 he expressly guards himself 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 estabhshing 
 of that which, in the course of time, had no 
 beginning; it is only the Hmit of our retrospec- 
 tive view of those operations which have come 
 to pass in time, and have been conducted by 
 supreme intelligence." ^ 
 
 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 
 because I desire to dim the fame of his eminent 
 successor. Few of the present generation of 
 geologists have read Playfair's " Illustrations," 
 fewer still the original " Theory of the Earth " ; the 
 more is the pity ; but which of us has not thumbed 
 ' The Theory of the Earth, vol. i. p. 223. 
 
X GEOLOGICAL REFORM 313 
 
 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 to separate his debt to Hutton from his 
 obUgations to Lyell ; and the history of the pro- 
 gress of individual geologists is the history of 
 geology. 
 
 No one can doubt that the influence of uniform- 
 itarian views has been enormous, and, in the 
 main, most beneficial and favourable to the 
 progress of sound geology. 
 
 Nor can it be questioned that Uniformitarianism 
 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 Uttle progress on the con- 
 tinent 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 
 
314 GEOLOGICAL REFOEM x 
 
 the period recorded in the raost ancient strata 
 now open to observation in the crust of the earth. 
 This is, for Hutton, " the point in which we can- 
 not see any farther " ; while Lyell tells us, — 
 
 "The astronomer may find good reasons for 
 ascribing the earth's form to the original fluidity 
 of the mass, in times long antecedent to the first 
 iatroduction of living beings into the planet ; but 
 the geologist must be content to regard the earliest 
 monuments which it is his task to interpret, as 
 belonging to a period when the crust had aheady 
 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 
 harmony of design and unity of purpose. To 
 1 Principles of Geology, vol. ii. p. 211. 
 
X GEOLOGICAL REFORM 315 
 
 assume that the evidence of the beginning, or end, 
 of so vast a scheme lies within the reach of our 
 philosophical inquiries, or even of our speculations, 
 appears to be inconsistent with a just estimate of 
 the relations which subsist between the finite 
 powers of man and the attributes of an infinite 
 and eternal Being." ^ 
 
 The limitations implied in these passages appear 
 to me to constitute the weakness and the logical 
 defect of Uniformitarianism. No one wiU impute 
 blame to Hutton that, in face of the imperfect 
 condition, in his day, of those physical sciences 
 which furnish the keys to the riddles of geology, 
 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 
 Qgg ; and I know not on what ground it should 
 find more difficulty in unravelling the complexities 
 of the development of the earth. In fact, as Kant 
 
 ' Principles of Geology, vol. ii. p. 613. 
 
316 GEOLOGICAL REFORM x 
 
 has well remarked,^ the cosmical process is really 
 simpler than the biological. 
 
 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 Uniformitarianism the place, as the 
 permanent 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 thise two histories. 
 
 If I study a Uving being, under what heads 
 does the knowledge I obtain fall ? I can learn its 
 structure, or what we call its Anatomy ; and its 
 
 ^ "Man darf es sich also nicht befremden lassen, wenn icli 
 mich unterstehe zu sagen, dass eher die Bildung aller Himmels- 
 kbrper, die Ursaclie ihrer Bewegungen, kurz der Ursprung der 
 ganzen gegenwartigen Verfassung des Weltbaues werden konnen 
 eingesehen werden, ehe die Erzeugung eiues einzigen Krautes oder 
 einer Raupe aus meehanischen Griinden, deutlich und vollstandig 
 kund werden wird." — Kakt's SiimmiUche Werke, Bd. i. p. 220. 
 
X GEOLOGICAL REFORM 317 
 
 Development, or the series of changes which it 
 passes through to acquire its complete structure. 
 Then I find that the living being has certain 
 powers resulting from its own activities, and the 
 interaction of these with the activities of other 
 things — the knowledge of which is Physiology. 
 Beyond this the Hving being has a position in 
 space and time, which is its Distribution. All 
 these form the body of ascertainable facts which 
 constitute the status qioo of the Hving 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 find 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 formations is 
 the history of a succession of such anatomies, or 
 corresponds with development, as distinct 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 
 animal. The phenomena of the seasons, of the 
 trade winds, of the Gulf-stream, are as much the 
 
318 GEOLOGICAL REFORM x 
 
 results of the reaction between these inner 
 activities and outward forces, as are the budding 
 of the leaves in spring and their falhng in autumn 
 the effects of the interaction between the organ- 
 isation of a plant and the solar light and heat. 
 And, as the study of the activities of the living being 
 is called its physiology, so are these phenomena 
 the subject-matter of an analogous telluric physio- 
 logy, 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 con- 
 stitute its distribution. This subject is usually 
 left to the astronomer; 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 posi- 
 tion 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 geological 
 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 
 
X GEOLOGICAL REFORM 319 
 
 which are out of reach of direct observation; or, 
 it may be physiological speculation so fax as it 
 relates to undetermined problems relative to the 
 activities of the earth ; or, it may be distributional 
 speculation, if it deals with modifications of the 
 earth's place in space ; or, finally, it will be a?tio- 
 logical speculation if it attempts to deduce the 
 history of the world, as a whole, fi-om the known 
 properties of the matter of the earth, in the con- 
 ditions 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 
 altogether. 
 
 The one point the catastrophists and the uni- 
 formitarians agreed upon, when this Society was 
 founded, was to ignore it. And you wiU find, if 
 you look back into our records, that our revered 
 fathers in geology plumed themselves a good de^ 
 upon the practical sense and wisdom of this 
 proceeding. As a temporary measure, I do not 
 presume to challenge its wisdom; but in all 
 organised bodies temporary changes are apt to 
 produce permanent effects ; and as time has 
 shpped by, altering aU 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 
 
320 GEOLOGICAL REFORM x 
 
 speculation within these walls has been of doubtful 
 beneficence. 
 
 The sort 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 bis 
 " General Natural History and Theory of the 
 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 cosmo- 
 gony, in the shape of a theory of the causes which 
 have led to the development of the universe 
 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.^ He accounts 
 for the relation of the masses and the densities of 
 the planets to their distances from the sun, for the 
 eccentricities of their orbits, for their rotations, for 
 
 ^ Grant {Sistory of Physical Astronomy, p. 574) makes but 
 the briefest reference to Kant. 
 
 2 " Allgemeine Natuvgesohichfe und Theorje des Himmels ; 
 Oder Versuch von der Verfassung und dem mechanisohen 
 Ursprunge des ganzen Weltgebaudes nach Newton'seben Grand- 
 satzen abgehandelt. " — Kant's Sammtliche Werke, Bd. i. p. 
 207. ' Systime du Monde, tome ii. chap. 6, 
 
X GEOLOGICAL REFORM 321 
 
 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 eventually 
 destroy its organisation, by concentrating upon 
 itself the matter of the whole system ; but, as the 
 result of this concentration, he argues for the 
 development of an amount of heat which will 
 dissipate 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 
 matter. At one point of this he supposes a single 
 centre of attraction set up ; and, by strict deduc- 
 tions 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-maelstrom, 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 attractions of the central systems 
 bring their constituents 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, 
 
 VOL. vin y 
 
322 GEOLOGICAL REFORM x 
 
 and the chaotic materials 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 
 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 
 undergoing," and is, in fact, a brief and pregnant 
 essay upon the principles of geology. Kant gives 
 an account first " of the gi'adual 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 
 ' Kant's Sdmmtliche Werke, Bd. viii. p. 145. 
 
X GEOLOGICAL' REFORM 323 
 
 earth put forward by Scheuchzer, Moro, Bonnet, 
 Woodward, White, Leibnitz, 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- 
 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 consti- 
 tution 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 
 beginning 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 Cata^trophism, 
 Uniformitarianism, and Evolutionism, are com- 
 monly supposed to be antagonistic to one another ; 
 
 T 2 
 
324 GEOLOGICAL REFORM x 
 
 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 
 precious truths. 
 
 Catastrophism has insisted upon the existence 
 of a practically unlimited bank of force, on which 
 the theorist might draw; and it has cherished 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 doctrine of 
 evolution. 
 
 UNiFORMiTARiANiSM:,on the other hand, has with 
 equal justice insisted upon a practically unlimited 
 bank of time, ready to discount any quantity 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 Cata- 
 strophism and Uniformitarianism. On the contrary, 
 it is very conceivable that catastrophes may be 
 part and parcel of uniformity. Let me illustrate 
 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 
 
X GEOLOGICAL REFORM 325 
 
 hammer might be made to blow up a barrel of 
 gunpowder, 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 uniformitarian 
 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 
 Evolution, which embraces all that is sound in 
 both Catastrophism and Uniformitarianism, while 
 it rejects 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 applies 
 the same method to the living and the not-living 
 world ; and embraces, in one stupendous analogy, 
 the growth of a solar system from molecular chaos, 
 the shaping of the earth from the nebulous cub- 
 hood of its youth, through innumerable changes 
 and immeasurable ages, to its present form ; and 
 the development of a living being from the shape- 
 less mass of protoplasm we term a germ. 
 
 I do not know whether Evolutionism can claim 
 that amount of cuiTency which would entitle it 
 to be called British popular geology ; but, more 
 
326 GEOLOGICAL REFORM X 
 
 or less vaguely, it is assuredly present in the 
 minds of most geologists. 
 
 Such being the three phases of geological 
 speculation, 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 
 distinguished physicist takes to be the representa- 
 tive of geological speculation in general. And 
 thus a first issue is raised, inasmuch as many 
 persons (and those not the least thoughtful among 
 tlie younger geologists) do not accept strict Uni- 
 formitarianism as the final form of geological 
 speculation. We should say, if Hutton and 
 Playfair declare the course of the world to have 
 been always the same, point out the fallacy by all 
 means ; but, in so doing, do not imagine that 
 you are proving modern geology to be in opposi- 
 tion to natural philosophy. I do not suppose 
 that, at the present day, any geologist would be 
 found to maintain absolute Uniformitarianism, 
 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 7nay be 
 cooling. Most of us, I suspect, are Gallios, " who 
 care for none of these things," being of opinion 
 that, true or fictitious, they have made no prac- 
 tical difference to the earth, during the period 
 
X GEOLOGICAL EEFOEM 327 
 
 of which a record is preserved in stratified 
 deposits. 
 
 The accusation that we have been running 
 counter to the principles of natural philosophy, 
 therefore, is devoid of foundation. The only 
 question 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 contravening such conclusions ? the 
 second, if we are, are those conclusions so firmly 
 based that we may not contravene them ? I reply 
 in the negative to both these questions, and I 
 wiU give you my reasons for so doing. Sir 
 William Thomson believes that he is able to 
 prove, by physical reasonings, " that the existing 
 state of things on the earth, Ufe on the earth — all 
 geological history showing continuity of life 
 — must be limited within some such period 
 of time as one hundred million years " {loc. 
 cit. p. 25). 
 
 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 
 embarrassed 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." Now does this mean 
 
328 GEOLOGICAL REFORM x 
 
 that it may have been two, or three, or four 
 hundred million years ? Because this really 
 makes all the difference. ^ 
 
 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 = O'OOl. Consequently, the deposit 
 of 100,000 feet of stratified rock in 100,000,000 
 years means that the deposit has taken place 
 at the rate of xoW of a foot, or, say, gJ^ 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 the average, at the rate of -^ 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 aU, the qualifying phrase 
 " some such period " may not necessitate the 
 assumption of more than y^^ or -^^ or -^-^ 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 
 
 ' Sir William Thomson implies (loe. cit. p. 16) that the pre- 
 cise time is of no consequence : "the piinciple is the same"; 
 but, as the principle is admitted, the whole discussion turns on 
 its practical results. 
 
X GEOLOGICAL BEFOEM 329 
 
 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 this planet to one, two, or 
 three hundred million years requires a complete 
 revolution in geological speculation, the onus 
 prohandi 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 
 degree ; and we may therefore proceed with much 
 calmness, and indeed much indifference, as to the 
 result, to inquire whether that limitation is 
 justified by the arguments employed in its 
 support. 
 
 These arguments are three in number: — 
 I. 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 
 
330 GEOLOGICAL EEFOEM x 
 
 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 clear- 
 ness and intelligibility, now more than a century 
 old, ^ but deduced from it some of its more im- 
 portant consequences, such as the constant turn- 
 ing 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. 
 
 ' " Untersuchung der Frage ol) die Erde in ihrer Unidrehung 
 um die Achse, wodurch sie die Abwecliselung des Tages und der 
 Nacht hervorbringt, einige Veriindening seit don ersten Zeitoii 
 ihres Ursprunges erlitten habe, &c." — Kant's Sdmmtliche 
 IFcrke, Bd. i. p. 178. 
 
X GEOLOGICAL REFORM 331 
 
 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 
 attraction of the earth on the moon; and, con- 
 sequently, 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 
 retardation must either be insignificant in amount, 
 or be counteracted by some other agency. 
 
 Our great astronomer, Adams, however, appears 
 to have found a flaw in Laplace's calculation, 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 retardation 
 
 ' Sir W. Thomson, loc. cit. p. 14. 
 
332 GEOLOGICAL EEFORM x 
 
 of the earth (which is hypothetically assumed to 
 exist) may be due in part, or wholly, to the increase 
 of the moment of inertia of the earth by meteors 
 falling upon its surface. This suggestion also 
 meets with the entire approval of Sir W. Thomson, 
 who shows that meteor-dust, accumulating at the 
 rate of one foot in 4,000 years, would account for 
 the remainder of retardation.^ 
 
 (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 
 rotation : — 
 
 "Let us suppose ice to melt from the polar 
 regions (20° round each pole, we may say) to the 
 extent of something more than a foot thick, 
 enough to give I'l 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 calculations for 
 the mean sea-level than any hitherto 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 
 1 Sir W. Thomson, loc. cit. p. 27. Ibid. 
 
X GEOLOGICAL EEFOEM 333 
 
 who have made the suggestions I have cited. On 
 the contrary, it is necessary to my argument to 
 assume 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 
 inadmissible appearance of authority over the 
 results 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 peascods, 
 so pages of formulae will not get a definite result 
 out of loose data. 
 
 In the present instance it appears to be 
 admitted : — 
 
 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 
 diminishing, it is not certain how much of that 
 retardation 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 
 outside, to not more than 2,600 years. 
 
 ' It will be understood tliat I do not wish to deny that the 
 earth's rotation may be undergoing retardation. 
 
334 GEOLOGICAL REFORM x 
 
 3. The effect 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 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 calculation, 
 tidal retardation will only account for a retardation 
 of 22" in a century, or -j^%- (say -J) of a second per 
 annum. 
 
 Thus, assuming that the accumulation of polar 
 ice since the Miocene epoch has only been suffi- 
 cient 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 f of a second per annum 
 in the way of acceleration. 
 
X GEOLOGICAL REFORM 335 
 
 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 1862, on the 
 age of the sun's heat, explains results of investiga- 
 tion into various questions as to possibilities 
 regarding 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 years, 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 illum- 
 inated the earth for five hundred million years." ^ 
 
 ' ioc. cit. p. 20. 
 
336 GEOLOGICAL REFORM X 
 
 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 
 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 
 interior of the earth implies either a heating of 
 the earth within the last 20,000 years of as much 
 as 100° F., or a greater heating all over the surface 
 at some time further back than 20,000 years, and 
 then proceeds thus : — 
 
 " Now, are geologists prepared to admit that, at 
 some time within the last 20,000 years, there has 
 been all over the earth so high a temperature as 
 that ? I presume not ; no geologist — no modern 
 
X GEOLOGICAL REFORM 337 
 
 geologist — would for a moment admit the hypo- 
 thesis that the present state of underground heat 
 is due to a heating of the surface at so late a 
 period as 20,000 years ago. If that is not admitted 
 we are driven to a greater heat at some time more 
 than 20,000 years ago. A greater heating all 
 over the surface than 100° Fahrenheit 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 200,000 years ago ? For the uniformity 
 theory, the further back the time of high surface- 
 temperature is put the better; but the further 
 back the time of 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 milKon 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 60,000,000 
 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. 
 
 ' Loo. cU. p. 24. 
 
 VOL. VIII 5; 
 
338 GEOLOGICAL REFORM X 
 
 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 coohng mass, the quantity of 
 heat lost per year, supposing the rate of cooling to 
 have been uniform, multiplied by any given 
 number of years, will be given the minimum 
 temperature that number of years ago. 
 
 But is the earth nothing but a cooling mass, 
 " hke a hot-water jar such as is used in carriages," 
 or " a globe of sandstone," and has its cooling 
 been uniform ? An affirmative answer to both 
 these questions seems to be necessary to the 
 validity 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 
 consideration. 
 
 For example, is it not possible that, at the 
 prodigious 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 
 
X GEOLOGICAL REFORM 339 
 
 distinct from that which they possess as cooUng 
 bodies? And has it not also been proved by 
 recent researches that the quahty of the atmo- 
 sphere may immensely affect its permeability to 
 heat ; and, consequently, profoundly 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 
 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 principles 
 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 
 " palaeontology," 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 
 
XT PALAEONTOLOGY AND EVOLUTION 341 
 
 has undergone a succession of changes which, 
 upon the whole, have been of a slow and gradual 
 character. 
 
 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, 
 similar 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, faunae 
 and florae 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 Palaeozoic epoch 
 as at present ; and those seemingly sudden ap- 
 pearances of new genera and species which we 
 ascribe to new creation, may be simple results 
 of migration." 
 
 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 
 
342 PALEONTOLOGY AND EVOLUTION xi 
 
 existence of such forms is recorded, is small. 
 When compared with the lapse of time since 
 the first appearance of these forms, the amount 
 of change is wonderfully small. Moreover, in 
 each great group of the animal and vegetable 
 kingdoms, there are certain forms which I termed 
 Persistent 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 
 show us no evidence of siich modification, oi 
 demonstrates such modification as has occurred 
 to have been very slight ; and, as to the nature 
 of that modification, it yields no evidence what- 
 soever that the earlier members of any long-con- 
 tinued 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 know- 
 
XI PALEONTOLOGY AND EVOLUTION 343 
 
 ledge and reflection, and an extreme desire to get 
 at the truth, may afford me. 
 
 1. With respect to the first proposition, I may- 
 remark that whatever may be the case 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 
 
844 PALAEONTOLOGY AND EVOLTfTION xi 
 
 the weighty evidence which M. Barrande has 
 accumulated, and have admitted the doctrine of 
 colonies. But the admission of the doctrine of 
 colonies implies the further admission that even 
 identity of organic remains is no proof of the 
 sjTichronism 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 
 
XI PALEONTOLOGY AND EVOLUTION 345 
 
 comparatively scanty Eocene fauna yields examples 
 of the orders Oheirojptera, Insectivora, Bodentia, and 
 Perissodactyla ; of Artiodactyla under both the 
 Ruminant and the Porcine modifications ; of Garni- 
 vora, 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 Beptilia, except the Ophidia, 
 represented ; while some groups, such as the 
 Ornithoscelida and the Pterosauria, more specialised 
 than any which now exist, abounded. 
 
 There is one division of the Amphibia which 
 offers especially important evidence upon this 
 point, inasmuch as it bridges over the gap between 
 the Mesozoic 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 vertebrae, 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 
 
346 PALvKONTOLOGY AND EVOLUTION xi 
 
 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 
 it is certain that a comparatively highly organised 
 vertebrate type, such as that of the Labjrrintho- 
 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 Globigerinm, 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. 
 
XI PALEONTOLOGY AXD ETOLUTIOX "47 
 
 Many jears ago^ I ventured to speak of the 
 Atlantic mud as " modem chalk," and I know of 
 no fact inconsistent with the view which Professor 
 Wyville Thomson has advocated, that the modem 
 chalk is not only the lineal descendant of the 
 ancient chalk, hut that it remains, so to speak, in 
 the possession of the ancestral estate : and that 
 from the Cretaceous period (if not much earUer) 
 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 Tercbraiuh caput-strpentis 
 and Beryx, not to mention other forms of animal* 
 and of plants, thus bridge over the interval 
 between the present and the Mesozoic periods, is 
 it possible that the majority of other hving 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 respect, 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 
 
 ' Soe an article in the Saturday Review, for 1858, on " Chalk, 
 Ancient and Modern." 
 
348 PALiEONTOLOGT AND EVOLUTION xi 
 
 foundation. So far, indeed, as the Invertehrata and 
 the lower Vertehrata are concerned, the facts and 
 the conclusions which are to be drawn from 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 Polypterus and to Lepidosiren. 
 
 But when we turn to the higher Vertehrata, 
 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 different 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 itself, prove that evolution took place by and 
 through it, nor does it constitute more than pre- 
 
XI PALAEONTOLOGY AND EVOLUTION 849 
 
 sumptive 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 the doctrine of evolution offers 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 case of the 
 Pigs, the Anoplotheridm, and the Ruminants. 
 The AnoplotJieridw are intermediate between the 
 first and the last ; but this does not tell us whether 
 the Ruminants have come from the Pigs, or the 
 Pigs from Ruminants, or both from Anoplotheridm, 
 or whether Pigs, Ruminants, and Anoplotheridce 
 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, fiirther, 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, 
 
350 PALEONTOLOGY AND EVOLUTION xi 
 
 and, in dealing with fossils, may mistake uncles 
 and nephews for fathers and sons. 
 
 I think it necessary to distinguish between the 
 former and the latter classes of intermediate forms, 
 as intercalary types and linear types. When I 
 apply 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 Ruminants — 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 TJngnlata, but M. 
 Gaudry's great monograph upon the fossils of 
 Pikermi (which strikes me as one of the most 
 perfect pieces of palgeontological work I have seen 
 for a long time) shows us, among the Primates, 
 Mesopitheeus as an intercalary form between the 
 Semnopitheei and the Macaci ; and among the 
 Carnivwa, Hymnictis and Ictitherium as intercalary. 
 
XI PALEONTOLOGY AND EVOLUTION 351 
 
 or, perhaps, linear types between the Viverridm 
 and the Hymnidm. 
 
 Hardly any order of the higher Mammalia 
 stands so apparently separate and isolated from 
 the rest as that of the Getacea ; though a cai-efiil 
 consideration of the structure of the pionipede 
 Garnivom, or Seals, shows, in them, many an 
 approximation towards the still more completely 
 marine mammals. The extinct Zctiglodon, how- 
 ever, presents us with an intercalary form between 
 the t3rpe 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 premaxiUary 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 approxi- 
 mations to the cetacean form of those parts. 
 
 The scapula resembles that of the cetacean 
 Byperoodon, but the supra-spinous fossa is larger 
 and more seal-like; as is the humerus, which 
 differs from that of the Getacea in presenting true 
 
352 PALEONTOLOGY AND EVOLUTION xi 
 
 articular surfaces for the free jointing of the 
 bones of the fore-arm. In the apparently com- 
 plete absence of hinder limbs, and in the characters 
 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 
 Squahdon, furnished much better means than 
 anatomists previously possessed of fitting in 
 another link of the chain which connects the 
 existing Getacea with Zeaiglodon. 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 CctcLcea. 
 
 It appears to me that, just as among the 
 existing Oarnivora, 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 Getacea. 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, 
 respecting the relations in time of the Garnivora 
 and Getacea. 
 
XI PALiEONTOLOGY AND EVOLUTION 353 
 
 Thus far we have been concerned with the 
 intercalary types which occupy the intervals 
 between Families or Orders of the same class; 
 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 OmithosctUda (or 
 Binosauria 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 Beptilia 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 hmbs and the pelvis are 
 much more similar to those of Birds than they 
 are to those of EeptUes, and that these Bird- 
 reptiles, or Eeptile-birds, were more or less com- 
 pletely bipedal, 
 
 When I addressed you in 1862, I should have 
 been bold indeed had I suggested that palaeon- 
 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 
 
 VOL. VIII A A 
 
354 PALAEONTOLOGY AND EVOLUTION XI 
 
 lizard to the bird was effected. These, very prob- 
 ably, are still hidden from us in the older for- 
 mations. 
 
 Let us now endeavour to find some cases of 
 true linear tjrpes, 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 
 evidence should be quite satisfactory, it is necessary 
 that we should be acquainted with aU 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 palseontologist are so 
 often based. M. Gaudry has arranged the species 
 of Hymnidce, Prohoscidea, Bhinocerotidce, and Equidce 
 in their order of filiation firom their earliest appear- 
 ance in the Miocene epoch to the present time, and 
 Professor Kutimeyer has drawn up similar schemes 
 for the Oxen and other Ungulata — ^with what, I 
 am disposed to think, is a fair and probable approxi- 
 mation 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, except in those 
 cases in which, by a fortunate accident, 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 
 
XI PAt^ONTOLOGY AND EVOLUTION 355 
 
 particular case in such a way that it will stand 
 rigorous criticism. 
 
 After much search, however, I think that such 
 a case is to be made out in favour of the pedigree 
 of the Horses. 
 
 The genus JEguus is represented as far back as 
 the latter part of the Miocene epoch; but in 
 deposits belonging to the middle of that epoch its 
 place is taken by two other genera, Hipparion and 
 AncMtherium ; ^ and, in the lowest Miocene and 
 upper Eocene, only the last genus occurs. A 
 species of AncMtherium was referred by Cuvier to 
 the Palceotheria under the name of F. 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 
 Paloeotherium, especially Cuvier's PalmotTierium 
 minus, which has been formed into a separate 
 genus, Plagiolophus, by Pomel. But in the fact 
 that there are only six fuU-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 
 
 ' Hennann von Meyer gave the name of ATichiiherium to A. 
 Ezqimrrce ; and in his paper on the subject he takes great pains 
 to distinguish the latter as the type of a new genus, from 
 Cuvier's Palmotherium d'Orleavs. But it is precisely the 
 Palcmtherium d'Orlians which is the type of Christol's genus 
 HipparitJierium ; and thus, though Hipparillicrmm is of later 
 date than AnchitTierium, it seemed- to me to have a sort of 
 eijuitable right to recognition when this Address was written. 
 On the whole, however, it seems most convenient to adopt 
 Anchitherium. 
 
 A A 2 
 
856 PALEONTOLOGY AND EVOLUTION xi 
 
 second premolar has an anterior prolongatita ; and 
 that the posterior molar of the lower jaw has, as 
 Cuvier pointed out, a posterior lobe of much 
 smaller size and diiferent form, the dentition of 
 ATichitherium departs from the type of the 
 Palceotherium, and approaches that of the Horse. 
 
 Again, the skeleton of Anchithei'ium is ex- 
 tremely equine. M. Ghristol 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 Anohitherium. 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 flat 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 
 
 ^ 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 mandible, which shows that, 
 as in the Falceolheria, the hindermost milk-molar of the lower 
 
XI paljEOntoi,ogy and evolution 357 
 
 are three, like those of the fore leg; and the 
 middle 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 mth the 
 radius, and appearing to be little more than a 
 ridge on the surface of the latter bone until it is 
 carefully examined. The front toes are still three, 
 but the outer ones are more slender than in 
 Anchitherium, and their hoofs smaller in proportion 
 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 Eqiius, finally, the crowns of the grinding- 
 teeth become longer, and their patterns are slightly 
 modified ; the middle of the shaft of the ulna 
 usually vanishes, and its proximal and distal ends 
 ankylose with the radius. The phalanges of the 
 two outei- toes in each foot disappear, their meta- 
 carpal and metatarsal bones being left as the 
 " splints." 
 
 jaw was devoid of the posterior lobe which exists in the hinder- 
 most true molar. 
 
358 PALEONTOLOGY AND EVOLUTION XI 
 
 The Hipparion has large depressions on the 
 face in front of the orbits, like those for the 
 " larmiers " of many ruminants ; but traces of 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 AricMthermm, of the 
 Hipparion, and of the ancient Horses consti- 
 tute the lineage of the modern Horses, the Jlip- 
 parion being the intermediate stage between the 
 other two, and answering to B in my former 
 illustration. 
 
 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 AticM- 
 therium ; but yet, as compared with other mam- 
 
XI PALAEONTOLOGY AND EVOLUTION 359 
 
 mals, the reduction and specialisation of parts in 
 the Anchitherimn remain great. 
 
 Is it not probable then, that, just as in the 
 Miocene epoch, we find an ancestral equine form 
 less modified than Uquus, so, if we go back 
 to the Eocene epoch, we shall find some quadruped 
 related to the Anchithcrium, as Hipparion is re- 
 lated to Uquus, and consequently departing less 
 from the average form ? 
 
 I think that this desideratum is very nearly, if 
 not quite, supplied by Plagiolophus, 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 ATichithermm, and their crowns 
 are as thinly covered with cement; but the 
 grinders diminish 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 Uquidce, while it is more slender than in most 
 of the true Palceotheria ; 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 Uquidce. 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 Uquidce. The fibula 
 is distinct, but very slender, and its distal end is 
 
360 PALAEONTOLOGY AND EVOLUTION XI 
 
 ankylosed with the tibia. There are three toes 
 on the hind foot having similar proportions to 
 those on the fore foot. The principal metacarpal 
 and metatarsal bones are flatter than they are in 
 any of the UquidcB ; and the metacarpal bones are 
 longer than the metatarsals, as in the Palmotheria. 
 
 In its general form, Flagiolophus resembles a 
 very small and slender horse,^ and is totally unlike 
 the reluctant, pig-like creature depicted in Cuvier's 
 restoration of his Palceothermm mimes in the 
 " Ossemens Fossiles." 
 
 It would be hazardous to say that Flagiolophus 
 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 Flagiolophus. 
 
 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- 
 
 ' Such, at least, is the conclusion suggested by the proportions 
 of the skeleton figured by Cuvier and De Blainville ; but per- 
 haps something between a Horse and an Agouti would be nearest 
 the mark. 
 
XI PALAEONTOLOGY AND EVOLUTION 361 
 
 nislied with very strong reasons for looking for a 
 no less complete verification of the expectation 
 that the three-toed Plagiolophus-Yike " avus " of the 
 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 presented to 
 us by the Dichohune of the Eocene epoch, the 
 Cainotherium of the Miocene, and the Tragulidw, 
 or so-called " Musk-deer,'' of the present day. 
 
 The TragulidcB 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 Oainothermm and Bichohimc the upper 
 incisors are fully developed. There are seven 
 grinders ; the teeth form a continuous series with- 
 out a diastema. The metatarsals, the navicular 
 and cuboid, and the distal end of the fibula, 
 remain free. In the Cainotherium, also, the second 
 
362 PALEONTOLOGY AND EVOLUTION XI 
 
 metacarpal is developed, but is much shorter than 
 the third, while the fifth is absent or rudimentary. 
 In this respect it resembles Anoplotherium secunda- 
 rium. This circumstance, and the peculiar pattern 
 of the upper molars in Cainotherium, lead me to 
 hesitate in considering it as the actual ancestor 
 of the modern Tragulidm. If Dichdbune has a 
 fore-toed fore foot (though I am incHned to 
 suspect that it resembles Cainotherium), it will 
 be a better representative of the oldest forms of 
 the Traguline series ; but Bichdbune 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 Ung%lata, 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 Hyopopo- 
 tamus and Chosropotamus ; but Hyopotamus appears 
 to have had only two toes. 
 
 Again, all the great groups of the Euminants, 
 the Bovidce, Antilopidce, Camelopardalidce, and 
 Cervidce, are represented in the Miocene epoch, and 
 so are the Camels. The Upper Eocene Anoplo- 
 therium, which is intercalary between the Pigs 
 and the Tragulidw, 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 Goryphodon, 
 
XI PALAEONTOLOGY AND EVOLUTION 363 
 
 Hyracotherium, and Pliolophus. Suppose for a 
 moment, for the sake of following out the 
 argument, that Pliolophus represents the primary 
 stock of the Perissodactyles, and Dichohune that 
 of the Artiodactyles (though I am far from saying 
 that such is the case), 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 
 animal 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 Anchitheriuin was 
 converted into Equus, it is difiicult 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 
 
364 PALJiONTOLOGT AND EVOLUTION XI 
 
 I have already said, contains Cheiroptera, Insecti- 
 vora, Bodentia, Ungulata, Garnivora, and Getacca. 
 But the Gheiroptera are extreme modifications 
 of the Insectivora, just as the Getacea are extreme 
 modifications of the Carnivorous type ; and there- 
 fore it is to my mind incredible that monodelphous 
 Insectivora and Garnivora 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 Bidelphia, 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 Marsupialia must have already 
 existed long enough to have become differentiated 
 into carnivorous and herbivorous forms. But the 
 Monotremata are lower forms than the Bidelphia 
 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 
 
XI PALEONTOLOGY AND EVOLUTION 365 
 
 which Reptiles passed into Birds must have pre- 
 ceded them. In fact there is, even at present, 
 considerable ground for suspecting the existence 
 of Dinosauria in the Permian formations ; but, in 
 that case, lizards must be of still earlier date. 
 And if the very small diiferences which are 
 observable between the Crocodilia of the older 
 Mesozoic formations and those of the present day 
 furnish any sort of approximation towards an 
 estimate of the average rate of change among the 
 Sauropsida, it is almost appalling to reflect how far 
 back in Palaeozoic 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 appearance upon 
 the surface of the globe. But if considerations of 
 this kind compel us to place the origin of ver- 
 tebrated animals at a period sufiiciently distant 
 from the Upper Silurian, in which the first Elas- 
 mobranchs and Ganoids occur, to allow of the 
 evolution of such fishes as these from a Vertebrate 
 
366 PALEONTOLOGY AND EVOLUTION XI 
 
 as simple as the Amphioxus, I can only repeat 
 that it is appalling to Speculate upon the extent 
 to which that origin must have preceded the 
 epoch of the first recorded appearance of verte- 
 brate life. 
 
 Such is the further commentary which I have 
 to ofifer 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 palaeontology 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 
 
XI PALiEONTOLOGY AND EVOLUTION 367 
 
 it has been instructively discussed in the thought- 
 ful and ingenious work of Mr. Andrew Murray 
 " On the Geographical Distribution of Mammals." ^ 
 
 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 
 preceding 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 gTapple 
 
 ' The paper "On the Form and Distribution of the Land- 
 tracts during the Secondary and Tertiary Periods respectively ; 
 and on the Effect upon Animal Life which great Changes in 
 Geographical Configuration have probably 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. 
 
368 PALAEONTOLOGY AND EVOLUTION XI 
 
 with the following problem whenever it is clearly 
 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 Faunse 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 distributijon of 
 the terrestrial Vertebrata, 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 Vertebrata in 
 the present world, namely, — first, the NMozelamia%, 
 or New-Zealand province; secondly, the Austra- 
 lian province, including Australia, Tasmania, and 
 the Negrito Islands ; thirdly, Austro-Cohtnibia, or 
 South America plus North America as far as 
 Mexico; and fourthly, the rest of the world, or 
 Arctogma, 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 and 
 
 ' " On the Classification and Distribution of the Alectoro- 
 morphae ; " Proceedings of the Zoological Society, 1868. 
 
XI PALEONTOLOGY AND EVOLUTION 369 
 
 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 Eodent or two, 
 as at present). In Austro-Columbia, the later 
 Tertiary fauna exhibits numerous and varied forms 
 of Platyrrhine Apes, Rodents, Cats, Dogs, Stags, 
 Edentata, and Opossums ; but, as at present, no 
 Catarrhine Apes, no Lemurs, no Insedivora, Oxen, 
 Antelopes, Rhinoceroses, nor Didel^hia 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 
 
 VOL. VIII B B 
 
370 PALEONTOLOGY AND EVOLUTION XI 
 
 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 Rocky 
 Mountains. The results are very striking. The 
 total Miocene fauna comprises many genera and 
 species of Catarrhine Apes, of Bats, of Insectivora ; 
 of Arctogseal types of Rodentia ; oiProhoscidea ; of 
 equine, rhinocerotic, and tapirine quadrupeds ; of 
 cameline, bovine, antilopine, cervine, and traguline 
 Ruminants; of Pigs and Hippopotamuses; of 
 ViverridcB and Hymnido} among other Oarnivora ; 
 with Edentata allied to the Arctogseal Orycteropus 
 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 Bidelphidm, 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, Rhinoceroses, and a 
 great number and variety of Ruminants and Pigs, 
 which are absent in the present indigenous fauna ; 
 Europe had its Apes, Elephants, Rhinoceroses, 
 Tapirs, Musk-deer, Giraffes, Hyaenas, great Cats, 
 Edentates, and Opossum-Hke Marsupials, which 
 
XI PALEONTOLOGY AND EVOLUTION 371 
 
 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 Semnopithecine 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 Arctogaga. 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 Faunae 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 
 
 B B 2 
 
372 PALAEONTOLOGY AND EVOLUTION XI 
 
 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. 
 
 1 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 
 mammals, such as Castor, Hystrix, Mephas, 
 Mastodon, Eguus, Hipparion, Anchithermm, Rhino- 
 ceros, Cervus, Amphicyon, Hymnarctos, and Machair- 
 odus, are common to the Miocene formations of 
 the two areas, and have as yet been found (except 
 perhaps Anchithermm) 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 argu- 
 ment ; but, as there are good grounds for the 
 belief that the Australian province and the Indian 
 and South- African sub-provinces were separated 
 by sea from the rest of Arctogeea 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 separated by sea from North America during 
 a large part of the Miocene epoch. 
 
Si tALiEONTOLOGY AND EVOLUTION 373 
 
 It IS unfortunate that we have no knowledge of 
 the Miocene mammalian fauna of the Australian 
 and Austro-Columbian provinces ; but, seeing that 
 not a trace of a Platyrrhine Ape, of a Procyonine 
 Carnivore, of a characteristically South-American 
 Eodent, of a Sloth, an Armadillo, or an Ant-eater 
 has yet been found in Miocene deposits of Arc- 
 togsea, I cannot doubt that they already existed 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-Columbia 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 Arctogeeal 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- 
 thermm, and a new Anoplotherioid mammal 
 {Homalodotheriuni) 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 Arctogsea by 
 . way of the north and east. 
 
374 PALAEONTOLOGY AND EVOLUTION xi 
 
 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 
 favourable to the new comers. It is to be supposed 
 that these new regions ofifered themselves to the 
 Miocene Ungulates, as South America and Australia 
 ofifered 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 depres- 
 sion and ice-covering, must have almost depopu- 
 lated all the northern parts of Arctogsea, destroying 
 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 
 mammals 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 Miocene 
 Fauna were hemmed by the Himalayas, the 
 Sahara, the Eed Sea, and the Arabian deserts, 
 mthin their present boundaries. 
 
XI PALEONTOLOGY AND EVOLUTION 375 
 
 Now, on the hypothesis of evolution, there is no 
 sort of difficulty in admitting that the differences 
 between the Miocene forms of the mammalian 
 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 Faunae 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 Kecent distribution, and that no other sup- 
 position even pretends to account for them. It is, 
 indeed, a conceivable supposition that every species 
 of Rhinoceros and every species of Hyaena, in the 
 long succession of forms between the Miocene and 
 the present species, was separately constructed out 
 of dust, or out of nothing, by supernatural power ; 
 but until I receive distinct evidence of the fact, I 
 refuse to run the risk of insulting 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 
 
876 PALEONTOLOGY AND EVOLUTION XI 
 
 in point of extent or variety with those which are 
 jdelded 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 Insectivora, of Cheir- 
 optera, of Rodentia, of Garnivm^a, 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 Insectivora, Cheir- 
 optera, and Rodentia) are different from those of 
 the Miocene epoch, but present a remarkable 
 general 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 
 between 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 numtnulitic deposits are undoubtedly very 
 
XI PALEONTOLOGY AND EVOLUTION 377 
 
 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-nummulitic mammalian Fauna con- 
 tains Bats, two genera of Carnivora, three genera 
 of Ungulata (probably all perissodactyle), and a 
 didelphid Marsupial; all these forms, except 
 perhaps the Bat and the Opossum, belong to 
 genera which are not known to occur out of the 
 Lower Eocene formation. The Goryphodon appears 
 to have been allied to the Miocene and later 
 Tapirs, while Pliolophus, in its skull and dentition, 
 curiously 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 jDf the Tertiary period. But if 
 we now cross the frontier between the Cainozoic 
 and the Mesozoic faunae, as they are preserved 
 within the Arctogaeal area, we meet with an 
 astounding change, and what appears to be a 
 
378 PALEONTOLOGY AND EVOLUTION XI 
 
 complete and uumistakable 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, Bodentia, Ungiilata, or Garnivora, 
 which are so well represented in the Tertiaries. 
 No Insectivora are certainly known, nor any 
 opossum-like Marsupials. Thus there is a vast 
 negative difference between the Cainozoic and 
 the Mesozoic mammalian faunse of Europe. But 
 there is a still more important positive difference, 
 inasmuch 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, appear 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 
 
XI iPALvEONTOLOGY AND EVOLUTION 379 
 
 exists in Australia. But if there was this 
 Australian 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 Europe, is it not a very obvious sugges- 
 tion that, in the Mesozoic epoch, the Australian 
 province included Europe, and that the Arctogseal 
 province was contained within other hmits ? The 
 Arctogseal 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 simplest 
 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 
 geography of the globe ; whereby an area long 
 tenanted 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. 
 
880 PALAEONTOLOGY AND EVOLUTION ti 
 
 It is this Mesozoic continent (wtich 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 
 series 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 
 elements of its mammalian fauna during the 
 Mesozoic 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 
 already peopled, gradually spread. This invasion 
 of the land was prefaced by a previous invasion of 
 the Cretaceous sea by modern forms of mollusca 
 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 gradual 
 shifting of the deep sea, which at present bars 
 
XI PALAEONTOLOGY AND EVOLUTION 381 
 
 migration between the easternmost of these islands 
 and America, took place to the westward, while 
 the American side of the sea-bottom was gradually 
 upheaved, the paleontologist of the future 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 Mesozoic 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 extension 
 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 Palaeozoic 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 faunae seem to be related to the 
 Mesozoic lands and their faunae, just as those of the 
 Miocene epoch are related to those of the present 
 day. In fact, as I have recently endeavoured to 
 prove to the Society, there was an Arctogaeal con- 
 tinent and an Arctogaeal province of distribution 
 in Triassic times as there is now ; and the Saurop- 
 
382 PALEONTOLOGY AND EVOLUTION XI 
 
 sida 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 continuity 
 with the Arctogseal continent. 
 
 But now comes the further inquiry, Where was 
 the highly differentiated Sauropsidan fauna of the 
 Trias in Palaeozoic 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 dififerentiated out of 
 Lacertilia in the time represented by the passage 
 from the Palaeozoic to the Mesozoic formation, 
 appears to me to be hardly more credible, to say 
 nothing of the indications of the existence of 
 Dinosaurian forms in the Permian rocks which 
 have already been obtained. 
 
 For my part, I entertain no sort of doubt that 
 
 the Keptiles, Birds, and Mammals of the Trias are 
 
 the direct descendants of Reptiles, Birds, and 
 
 Mammals which existed in the latter part of the 
 
 ' Since this Address was read, Mr. Krefft has sent us news of 
 the discovery in Australia of a freshwater fish of strangely 
 Palaeozoic aspect, and apparently a Ganoid intei-raediate between 
 Dipterus and Lepidosiren. [The now well-known Ceratodus, 1894.] 
 
XI PALEONTOLOGY AND EVOLUTION 383 
 
 Palaeozoic epoch, but not in any area of the present 
 dry land which has yet been 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 reptiles 
 have been found in Permian rocks only in three 
 localities ; in some spots of France, and' recently 
 of England, and over a more extensive area in 
 Germany. Who can suppose that the few fossils 
 yet found in these regions give any sufficient re- 
 presentation 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 Palaeozoic Vertebrate 
 Fauna ought to have left its remains in the Coal- 
 measures, especially as there is now reason to 
 believe 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 
 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 
 gradual depression. The dry land thus depressed 
 
384 PALAEONTOLOGY AND EVOLUTION XI 
 
 must, therefore, have existed, as such, before the 
 Carboniferous 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 else- 
 where. 
 
 Again, let me say that I am making no 
 gratuitous assumption of inconceivable changes. 
 It is clear that the enormous area of Polynesia 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 in- 
 habitant. Suppose that the shores of this great 
 land were fi:inged, 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 
 
XI PALAEONTOLOGY AND EVOLUTION 385 
 
 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 con- 
 tinuity 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 
 existed in the Devonian epoch, inasmuch as M. 
 Barrande 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 another as New Zealand is to Australia, 
 or as Australia 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 inhabited the fresh waters of our 
 Devonian land. Amphibia and Beptilia, 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 that I can by no means 
 conceive that they have been developed out of 
 piscine forms in the interval between the Devonian 
 and the Carboniferous periods, considerable as that 
 is. And I take refuge in one of two alternatives : 
 either they existed in our own area during the 
 Devonian epoch and we have simply not yet found 
 
 VOL. VIII c 
 
386 PALJiONTOLOGY AND EVOLUTION XI 
 
 them; or they formed part of the population of 
 some other distributional province of that day, 
 and only entered our area by migration at the end 
 of the Devonian epoch. Whether Bcptilia 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 dis- 
 tribution of living and extinct animals has been 
 brought about. 
 
 I conceive that distinct provinces of the distribu- 
 tion of terrestrial life have existed since the earliest 
 period at which that life is recorded, and possibly 
 much earlier; and I suppose, with Mr. Darwin, 
 that the progress of modification of terrestrial 
 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 
 depressed during the Carboniferous epoch ; and 
 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 Sauropsida 
 and of the Mammalia were gradually developing. 
 
 The Permian epoch marks the commencement 
 of a new movement of upheaval in our area, which 
 attained its maximum in the Triassic epoch, when 
 
XI PALEONTOLOGY AND EVOLUTION 387 
 
 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 Palaeozoic epoch spread, and 
 formed the great Triassic Arctogseal 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 Rep- 
 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 conceive, 
 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 characteristic 
 fauna of which is probably a remnant of the popu- 
 lation of the latter part of this period. 
 
 Towards the latter part of the Mesozoic 
 period the movement of upheaval around the 
 shores of the Atlantic once more recommenced, 
 and was very probably accompanied by a de- 
 pression around those of the Pacific. The Verte- 
 brate fauna elaborated in the Mesozoic continent 
 moved westward and took possession of the new 
 
388 PALEONTOLOGY AND EVOLUTION XI 
 
 lands, which gradually increased in extent up to, 
 and in some directions 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 Antarc- 
 tic, may have occupied their present positions, 
 and only their coasts and channels of communi- 
 cation have undergone an incessant alteration. 
 And, finally, the hypothesis I have put before you 
 requires no supposition that the rate of change in 
 organic 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 
 justification in analogous phenomena of existing 
 nature. 
 
 I have now only to discharge the last duty 
 of 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 per- 
 form the important, and often laborious, functions 
 of your President a pleasure instead of a burden. 
 
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