wm 
 
 ^f'%t.M' 
 
 ^^£^. 
 
 ??». 
 
 m 
 
 
 '<5- •-* ,.■ 
 
 Tl: 
 
 
 m. 
 
 4»-^. #- 
 
 ,^^i^^ 
 
 
 LiV >N; 
 
 ■*t'w« — ■ 
 
 Eim^^ 
 
 rj*. 
 
 ^■^:., 
 
HtiU QJoUege of Agricultttre 
 
 IGtbcata 
 
A *|ufy of the structure of feathers, wi 
 
 3 1924 000 147 953 
 
Cornell University 
 Library 
 
 The original of this book is in 
 the Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924000147953 
 
UNIVERSITY or CALIFORNIA PUBLICATIONS 
 
 IN 
 
 V ZOiOLOGY 
 
 VoL 13vNo. 11, pp. 243-446, pi, ;i3-,37, 7 textfigs^. April 17, 1916 
 
 A STUDY OF THE STRUCTURE OF 
 
 FEATHERS, WITH REFERENCE TO THEIR 
 
 TAXONOMIG SIGNIFICANCE 
 
 BT 
 ASA C. CHANDLER 
 
 USIVEBSITT OP OALIFOBNIA PBESS 
 BEBKEIiET 
 
jnaVEBSlLTr OT oaufornia ptjblications 
 
 Note. — The UnlTeni^ of Calif oniia Bubllcatioiis jare offered in exchange for the pal) 
 cations of learned societies and institutions, nnlTeraities and libraries. Oon>plj$e lists'ii 
 idl the pnhUcatfons of ihe XTnlversity will be sent upon request. 76r sample CopleSi w 
 of puhllcattons or other information, address the Manager of the UnlTerBity Press, Eerkel<i 
 Oalifomla, U. S. A. All matter sent in exchange should he addressed to ^e Ezehi^l 
 Department, IJniTersltjr Zdhrary, Berkeley, Calif omia, IT. S. A. 
 
 OTTO HABSASSOWIIZ, B. TRCBDLAENDEB &; SOHN, 
 
 LEIPZIO. BERLIIT, 
 
 AgMit for the series in American Arch- Agent for the series in American Ar« 
 
 aeology and Ethnology, Classical Philology, aeology and Ethnology, Betany, Cteolol 
 
 Education^ Modem Philology, Philosophy, Geography, Mathematics, Pathdiogy; Fh^ 
 
 Psychology, History. <>logy. Zoology, and JdtemOirs. •- \ 
 
 ZOOIiOOT.— W. E. Bitter and O. A. Kof old. Editors. Price per volnnfe, $3.60; heglnnli 
 
 - with Vol. 11, $5.00. j 
 
 This series contains the contributions from the Sepaxtmentef Zoology, from ij 
 
 Marine Ziaborato^ of the Scripps Institution for Biological JCesearch,>t La: JoC 
 
 Calif omia, and from jfie Calif omia. Museum of Vertebrate Zoology in Berheley. ^ 
 
 Cited as XJtdv. Calif. Publ. Zool. 
 
 Volume 1, 1902-1905, 317 pages, with 28 plates... ....—.. ,~.... ... . $3j 
 
 Volume 2, (Contributions from tile Ziaboratory of the Marine Biological Associa- i 
 
 tion of San Diego), 1904-1906, xvli + 382 pages, with 19 plates...... $3i 
 
 Volume 3, 1906-1907, 383 pages, with 23 plates..; ..:......-. .^.„...-. -..1 — $SJ 
 
 Volume A 1907-1908, 400 pages, with 24 plates ..,......„,...-.._.„l...— ....._. $3. 
 
 Volume^, 1908-1910, 440 pa,ges, with 34 piates...,. .;........ :....,...;&... $S. 
 
 Volume 6, 1908-1911> 478 pages, with 48 plates....^ ......„....,-..,.. $3. 
 
 Volume 7 (Contributions from the Museum of Vertebrate Zoology), 1910-1912 
 
 446 pages, with 12 plates ... -.. ...:.„..„..%,,....,., $3. 
 
 Volume 8, 1911, 357 pages, with 26 plates.... .......:.... $3. 
 
 Volume 9, 1911-1912, 365 pages, vHth 24 piites.^.^ -. $3. 
 
 Volume 10, 1912-1913, 417 pages, with 10 plates...ul.-.— ..-.. $3.1 
 
 Volume 11, 1912-1914, 538 pages, with 26 platesl ...f. ..:-.,. — :..- $5.' 
 
 - Vol. 12. 1. A Study of a Collection of Oeese of the Branta'cg,nadmsis group 
 from the San Joaqnin Valley, Calif omia, by Harry S. Swarthi 
 Pp. 1-24, platpsl-2, 8 textflgs. November, 1913.;................,-.., — .. 
 
 2. Nocturnal Wajdderlngs* ef the Calif omla P<»cket OophM,_by Harold 
 
 C. Bryant. Pp. 26-29, 1 text fig. November, 1913 ....i...... - 
 
 3. The Beptiles of the San Jacinto Area of Southern California, by 
 
 Sarah Bogers Atsatt.^ Pp. 81-50. November, 1913......,_........;....,..... 
 
 4. An Account of the Mammals and Birds of the JCiower Colorado Val- 
 
 ley,^with Espeidal Eeference to the Distributional Prtblems Pre- 
 sented, by Joseph Orinnell. Pp. 51-294, plp.tes 3-13, 9 text flgs. 
 March, 1914 ;.'.._ ; :.— —. .- ■- — 
 
 5. Aplodontia chryseold, 9, New Mountain Beaver, from the, Trinity 
 
 Begion of Northern California, by Louise Eellogg. Pp. 296t296. 
 
 6. A Previously XTndescribed Aplodontia from the Middle North Coast 
 
 of California, ,by WflJter P. Ta:Hor. Pp. 297-300. 
 
 Nos. 5 and « in one cover. April, 1914...... ......_ ; 
 
 7. A Second Species of the Mammalian Genus Microdipodopa from 
 
 OaUfomla, by Joseph GrinneU. Pp. .301-304. AprU, i914..i., 
 
 8. Distribution of Biver Otters in Oaliforqia, with Description of a 
 
 New Subspecies, by Joseph Orinnell. Pp. 305-310, plate 14. Octo- 
 ber, 1914 - ,.^...:.._....:™..........U..., 
 
 9. Four New Pocket Gophers from California, by Joseph GrinneU. Pp. 
 
 311-31(8. November, 1914....... — :.: ~ 
 
 10. Three New Baces of Vespertillonid Bats from Calif omia, by Hilda 
 
 Wood Orinnell., Fp. 317-321. December, 1914...._.-.. 
 
 ili Eutamiaa sonomae, a New Chipmunk from the Inner Northern 
 
 Coast Belt of Calif omia, by Joseph GrinneU. Pp. 321-325, 1 text 
 
 .figure. January, 1915 — . -,-— 
 
 12. Batrachoaeps major and Bufo cognatv^ calif orMcua, New Amphibia 
 
 from Sbntiiem Calif omia, by Charles Lewis Camp. Pp. 327-834. 
 
 April, 1915 .. .. - 
 
UNIVERSrTY OF CALIFORNIA PUBLICATIONS 
 
 IN 
 
 ZOOLOGY 
 
 Vol 13, No. 11, pp. 243-446, pis. 13-37, 7 text figures April 17, 1916 
 
 A STUDY OP THE STRUCTURE OP PEATHERS, 
 
 WITH REFERENCE TO THEIR TAXO- 
 
 NOMIC SIONIPICANCE 
 
 BY 
 
 ASA C. CHANDLER 
 
 CONTENTS 
 
 Page 
 
 Introduction 244 
 
 Object and scope of paper 244 
 
 Acknowledgments 246 
 
 Historical 246 
 
 Nomenclature 248 
 
 Methods 254 
 
 Part I. General Morphology 255 
 
 Plumules 255 
 
 Distribution of plumules 256 
 
 Powder-down 258 
 
 Oil-gland feathers 259 
 
 Nestling feathers 259 
 
 Filoplumes 260 
 
 Contour feathers 263 
 
 Remiges 263 
 
 Rectrices 268 
 
 Unspeclalized contour feathers 269 
 
 Ornamental plumes 272 
 
 Ear coverts 273 
 
 Facial bristles and eyelashes 273 
 
 Facial ruffs 274 
 
 Color production 274 
 
 Isotely in production of colors 274 
 
 Effect of albinism on structural color modifications 279 
 
 Part II. Systematic 280 
 
 Introduction 280 
 
 Intraspeciflc and phylogenetic modifications 280 
 
 Classification adopted 282 
 
 Methods of comparative study 283 
 
 Ratltae 284 
 
 Order Struthioniformes 285 
 
244 University of Calif c^ia Publications in Zoology [Vol. 13 
 
 Page 
 
 Order Rhelformes 288 
 
 Order Casuarilformes 290 
 
 Order Apterygiformes 293 
 
 Carinatae 296 
 
 Order Sphenlsciformes 296 
 
 Order Colymbiformes 298 
 
 Order Procellariiformes 302 
 
 Order Ciconiiformes 307 
 
 Suborder Steganopodes 307 
 
 Suborder Ciconiae 318 
 
 Suborder Ardeae 321 
 
 Suborder Phoenlcopteri 325 
 
 Order Anseriformes 327 
 
 Suborder Anseres 327 
 
 Suborder Palamedeae 330 
 
 Order Falconiformes : 331 
 
 Suborder Cathartae 331 
 
 Suborder Gypogerani 333 
 
 Suborder Acclpltres 334 
 
 Order Galliformes 337 
 
 Suborder Galli , 338 
 
 Suborder Turnices 343 
 
 Order Crypturiformes 345 
 
 Order Gruiformes 348 
 
 Order Charadrilformes 354 
 
 Suborder Laro-limicolae 354 
 
 Suborder Pteroclo-columbae 358 
 
 Order Cuculiformes 363 
 
 Order Coracilformes 368 
 
 Order Passerlformes 380 
 
 General conclusions 385 
 
 Taxonomic value of the structure of feathers 385 
 
 Principal modifications of structure useful in taxonomy 386 
 
 Relationships of groups suggested or corroborated 387 
 
 The phylogenesis of birds as modified by morphology of feathers.... 390 
 Bibliography 392 
 
 INTEODUCTION 
 
 I. Object and Scope op Paper 
 
 Although as a class birds have received more attention from 
 nearly all classes of zoologists than any other group of vertebrate 
 animals, their natural classification presents a great many problems 
 difficult of solution, and no satisfactory phylogenetic arrangement 
 has yet been devised for them. It was with the hope of throwing 
 light on some of the dark places in the taxonomy of birds that the 
 writer attempted the work, the results of which are presented in this 
 
1916] Chandler: Structure of Feathers 245 
 
 paper, since it was believed that the comparative morphology of 
 feathers would almost certainly be of some taxonomic value in estab- 
 lishing the relationships of various groups of birds. 
 
 Since feathers are external and in constant contact with the 
 environment, they would naturally be expected to be among the first 
 structures of the body to feel the influence of environmental changes 
 and shocks, and would still be as liable to change by hybridization, 
 orthogenesis or any other method of evolution, as any of the other 
 structures. 
 
 There are numerous groups of birds, the taxonomic position and 
 phylogenetic relationships of which have been in very great doubt. 
 As far as possible the feathers of these groups have been studied with 
 the hope that the structure of the feathers would reveal relationships 
 that the structure of the other organs would not, on account of 
 parallel adaptations in the latter. Instances in which the morphology 
 of feathers has been found in this study to throw light on doubtful 
 relationships are numerous, for example, in the case of the Phoeni- 
 copteri, Tinamidae, and Pici. 
 
 Provided that birds were found to possess constant and peculiar 
 characters in the structure of their feathers, the results of such 
 work would be of high economic importance in the identification of 
 feathers used commercially, and for the confiscation of feathers 
 illegally used in commerce. This belief, in the course of the work, 
 has been amply justified, and already successful diagnoses of 
 unknown feathers have been made for the United States Customs 
 officers in the port of San Francisco. 
 
 Before undertaking a study of the phylogenetic modifications in 
 feathers, a careful study was made of the structural modifications 
 of feathers in the different parts of the plumage of a single repre- 
 sentative bird, namely. Circus hudsonius (Chandler, 1914). It was 
 discovered that certain general modifications found in this bird in 
 the structure, not only of different feathers, but of different parts 
 of the same feather, occur almost uniformly throughout the class. 
 A discussion of the typical structure of various kinds of feathers, 
 with a considei'ation of the more important modifications of struc- 
 ture correlated with color production, constitutes the first part of 
 this paper, while the second part deals with special group characters, 
 modifications and peculiarities, arranged in systematic order. No 
 attempt has been made to make a systematic study of the morphology 
 of any feathers except those of adult birds — i. e., of teleoptiles. 
 
246 University of California Publications in Zoology [Vol. 13 
 
 1\. Acknowledgments 
 
 To Professor C. A. Kofoid, of the University of California, under 
 whose direct supervision this work was carried on, the writer is 
 especially grateful for his very valuable advice and suggestions, 
 and for his aid in the preparation of this paper. 
 
 The writer is indebted to Dr. Joseph G-rinnell, of the Museum of 
 Vertebrate Zoology of the University of California, for free use of 
 the specimens in the museum. He also wishes to express his appre- 
 ciation of the generous supply of material for study by the American 
 Museum of Natural History in New York, and the United States 
 National Museum in Washington. Grateful acknowledgments are 
 due to Dr. "W. T. Hornaday and Mr. Lee S. Crandall of the New 
 York Zoological Park for saving and sending molted feathers which 
 could not readily be procured from museum specimens. 
 
 Other material was procured from the Memorial Museum in 
 Golden Gate Park, San Francisco, through Mr. W. G. Blunt of 
 the Natural History department. The writer is further indebted 
 to the California Academy of Sciences in San Francisco, for the use 
 of its collection of water birds, and to the Bentley Ostrich Farm of 
 Oakland, California, for the supply of ostrich feathers, and assist- 
 ance in the examination of living birds. 
 
 III. HiSTOEICAL 
 
 The first thorough and reliable work on feathers was done by 
 Nitzsch, a German ornithologist. This work was edited and pub- 
 lished by Burmeister, and later translated into English and published 
 in the Transactions of the Ray Society in 1876, a few of the miscon- 
 ceptions of the original author being rectified in the process. 
 
 This work, though dealing primarily with pterylography, contains 
 the first approximately accurate account of the structure of feathers 
 to be found in the whole literature of the subject, and may justly 
 stand as a masterpiece. Following Nitzsch, a number of works on 
 the development and structure of feathers appeared, among which 
 may be mentioned especially Clement (1876), Studer (1878), Jeffries 
 (1884), Klee (1886), Davies (1889), and Strong (1902); and, more 
 particularly on structure, Wray (1887b), Pycraft (1893), and 
 Maseha (1904). Many other less general but highly valuable • papers 
 
1916] Chandler: Structure of Feathers 247 
 
 on the structure and development of feathers have appeared, but 
 need not be mentioned here. 
 
 Throughout the literature, no general attempt has been made to 
 use differences in the morphology of the minute structures of feath- 
 ers as taxonomic or diagnostic characters. In a few cases where 
 feathers differ maeroscopically and obviously from the usual type, 
 as in cassowaries and penguins, they have been considered as of 
 taxonomic value, and the presence or absence, or degree of develop- 
 ment, of the aftershaft has been so used. Jeffries (1884) realized 
 that differences in the microscopic structures of feathers existed in 
 different groups of birds, as shown by the following quotation from 
 the paper cited: "The minute structures of these (wing and tail 
 feathers) vary in different groups of birds, as I havp myself observed, 
 and has, I believe, been pointed out by Schroeder, though I have not 
 seen his paper." In Newton's Dictionary of Birds, under the article 
 on "Feather", is a similar statement as follows: "Cilia which are 
 not furnished with hooks frequently have shapes which may possibly 
 prove to be characteristic of different groups of birds". 
 
 The only actual investigation of group differences in the micro- 
 scopic structure of feathers was done by Mascha (1904). His work 
 is accurate and suggestive as far as it goes, but he dealt only with 
 the remiges of a very limited number of species, and, as would be 
 expected from such a restricted survey, he missed entirelj' the taxo- 
 nomic value of certain of the most characteristic features in the 
 microscopic structure of feathers, and contributed but little towards 
 our knowledge of the systematic and phylogenetie value of feather 
 structures. 
 
 In recent years considerable work has been done by zoologists in 
 the study of the morphology and the taxonomic value of other 
 integumentary structures of vertebrates, and their results point to 
 the fact that such structures, though constantly in contact with the 
 environment, and subject to more external influences than any other 
 organs of the body, nevertheless possess phylogenetie characters which 
 are remarkably constant and easily recognizable. 
 
 The work of Toldt (1912) on the hair of mammals, like Mascha 's 
 (1904) work on feathers, though only a beginning, is careful and 
 accurate as far as it goes, and is highly suggestive in that it points 
 the way to a field which is still almost untouched. Work along 
 similar lines on the scales of reptiles has been done by Stehli (1910). 
 His study was rather a general treatise on a few types, designed 
 
248 University of California Publications in Zoology [Vol. 13 
 
 in part to show the relation of the scalation to the segmentation of 
 the musculature, but his description and figures indicate that modifi- 
 cations of taxonomie value undoubtedly exist in the scales of reptiles. 
 The scales of fishes have received more attention than any of the 
 structures in other groups which in a general way are analogous, 
 and these are the only integumentary growths, the morphologic modi- 
 fications of which have heretofore been actually applied to taxonomie 
 and phylogenetic problems. A series of papers by T. D. A. Cockerell 
 (1909-1913) deals with the actual taxonomie application of scale 
 structures, and gives keys to families and genera based on these char- 
 acters. Cockerell (1911c and 1912) has shown that the scales of 
 coeciliids also show characters which are of value in classification. 
 
 In view of the fact that all these integumentary structures of 
 vertebrates are homologous, or at least in a general way analogous, 
 to each other, and that investigations of them, in a general way, 
 present similar problems, and are governed by the same limitations, 
 and in fact frequently overlap each other, it seems to the writer that 
 a common name should be applied to the study of them. For this 
 study, which shall include the study of the development, morphology, 
 and phylogenesis of vertebrate scales, hair, and feathers, and any 
 other homologous or analogous structures, the writer wishes to sug- 
 gest the name Epiphyology (based upon ein^veLv^ to grow upon) as a 
 general term for the "study of outgrowths". In creating this term 
 it is admitted that the formation is not perfectly valid etymologically. 
 
 IV. NOMENCLATUEE AND DEFINITIONS 
 
 It is unfortunate that in the literature of feathers there has been 
 a very notable lack of uniformity in the use and meaning of terms, 
 resulting in no little confusion and inconvenience, considerably more 
 so among German writers, however, than among others. After a 
 careful study of the history and usage of the nomenclature of feathers, 
 the writer has selected a terminology which, taking all points of 
 view into consideration, seems to be the most logical and widely 
 applicable. These terms have been selected with regard (1) to the 
 general usage, (2) to convenience, (3) to priority. It seems advisable 
 to give a list of the terms here used to describe feathers, with their 
 definitions, and in the case of terms which have been used inac- 
 curately, the names of some of the authors who have used them in 
 the sense here accepted. The more important synonyms are also given, 
 
1916] 
 
 Chandler: Structure of Feathers 
 
 249 
 
 with their chief adherents in the ease of terms not commonly used 
 as alternatives. In a few cases new terms had to be coined, or old 
 ones re-defined, but it is hoped that the terminology here used will 
 meet with the approval of other workers, and come into general 
 
 out.v. 
 
 aftersh. 
 
 Fig. A. Typical contour feather. Abbreviations: aftersli., aftersliaft; cal., 
 calamus; doivn. str., downy structure; in. v., inner vane; out. v., 
 outer vane; pen. sir., pennaceous structure; sh., shaft. 
 
 use, a thing which would go a long way towards establishing sim- 
 plicity and clearness in the description of feathers and their struc- 
 tures. The terminology suggested is as follows: 
 
 TERiis or Orientation. In speaking of a feather, or any of its structures, 
 "dorsal" and "ventral" are used as intrinsic terms, i. e., with refer- 
 ence to the feather itself, regardless of its position on the bird, dor- 
 sal meaning, therefore, the side of the feather which is usually exposed, 
 or that opposite the superior umbilicus, which is considered to be 
 upon the ventral side Lateral is used with reference to the dorso- 
 
250 University of California Publications in Zoology [Vol. 13 
 
 ventral lines as here defined. Inner and outer, as applied to vanes, are 
 used to mean respectively the vanes adjacent to and away from the 
 next overlapping feather. Proximal and distal, as applied to entire 
 barbules or vanules, refer respectively to those on the side of the 
 ramus nearer to and away from the base of the feather. In all other 
 cases, proximal and distal are used intrinsically with reference to the 
 structure to which they apply; for example, the proximal part of a 
 barb is the less remote, and the distal part the more remote, from the 
 junction with the shaft. Inner and basal are sometimes used synony- 
 mously with proximal, while outer and terminal are likewise used in 
 place of distal. 
 Contour Featheks (fig. A). The feathers which form the contour of a bird's 
 body, growing only in the pterylae, and always with well-developed 
 shafts and calami. Eyelashes, ear-coverts, etc., and the semi-plumes of 
 Nitzsch (1867) are considered as modified contour feathers. German 
 synonym: Konturfedern. 
 
 Plumules. Small, downy feathers, more or less concealed, and with shaft 
 never highly developed. They grow either in the apteria or pterylae, 
 or both, often arranged in a definite manner around the contour feath- 
 ers; absent in some birds (Nitzsch, 1867; Coues, 1884; Evans, 1899, et 
 al.). Synonym: down or down feathers, a term for plumules which is 
 objectionable on account of its loose application not only to plumules, 
 but to any feather or part of feather possessing downy structure. Oer- 
 man synonyms: Dunen (Gadow, 1891); Plaumfedern (Wiedersheim, 
 1909). 
 
 FiLOPLUMES. Degenerate, hairlike feathers growing at the base of contour 
 feathers, composed of a slender quill not differentiated into shaft and 
 calamus, and much reduced vanes, the latter usually consisting of only a 
 few barbs and barbules at the extreme tip. German synonyms: Haar- 
 federn, Fadenfedern. 
 
 Down, or Downy Steuotuee (fig. A). That type of feather structure which 
 is produced by elongated, filamentous barbules, as opposed to a pen- 
 naceous structure (fig. A), which is produced by differentiated distal 
 and proximal barbules or modifications of them, i. e., pennaceous bar- 
 bules, as here used. German synonym.: Dunen. 
 
 Quill (fig. A). The main stem of a feather, including both shaft and cala- 
 mus (Coues, 1884; Beebe, 1906, et al.). Synonyms: main stem (Nitzsch, 
 1867), scapus (Nitzsch, 1867; Sundevall, 1886; Pycraft, 1893), primary 
 quill (Mascha, 1905). German synonyms: Kiel (G-adow, 1891), Haupt- 
 klel (Mascha, 1904). 
 
 Calamus (fig. A). The hollow basal portion of the quill, proximal to the 
 superior umbilicus. Synonym: barrel (Newton, 1899), tube (Nitzsch, 
 1867). German synonym: Spule, of general use. 
 
 Infeeioe Umbilicus. The proximal end of the calamus, where the papilla 
 finally closes after the maturity of the feather. 
 
 SuPEEioE Umbilicus. The pore at the distal end of the calahius, at the junc- 
 tion of shaft and aftershaft, or, in some feathers, where the Inner and 
 outer vanes meet. Synonym: umblllciform pit (Nitzsch, 1867; Newton, 
 1899). German synonym: 'SSIa.'bei (Gadow, 1891). 
 
^^^^] Chandler: Structure of Feathers 251 
 
 Shaft (fig. A). The portion of the quill distal to the superior umbilicus 
 upon which are borne the vanes. Synonyms: rhachis, used generally as 
 an alternative in heavier scientific writing. German synonym: Schaft, 
 of general use. 
 
 Aftershaft (fig. A). The ventral counterpart of the shaft plus its vanes 
 ("plate", see below), springing from the ventral lip of the superior 
 umbilicus, sometimes vestigial or absent. Synonyms: hyporhachis, used 
 as is rhachis for shaft; accessory plume (Sundevall, 1886). German 
 synonyms: Afterschaft, Nebensohaft (Gadow, 1891); Afterteder (Studer, 
 1878), Afterschaft, only its shaft (Studer, 1878). 
 
 Plate. A convenient term used by Mascha (1905), to designate the shaft 
 with both its vanes. Synonym: vexillum (Clement, 1876). German 
 synonym.: Flache (Mascha, 1904). 
 
 Vane (fig. A). That portion of the feather borne on one side of the shaft, 
 composed of barbs, usually with barbules. Inner vane, that which is 
 overlapped by the outer vane of the adjacent feather. Synonym: vexil- 
 lum, web, common alternatives (the vexillum of Clement, 1876, equals 
 plate), pogonium (Sundevall, 1886). German synonym: Fahne, of 
 general use. 
 
 Bakb (fig. B). A ramus or primary branch of the shaft plus its barbules 
 (Beebe, 1906; Headley, 1895, et at); has been loosely used by many 
 authors to designate either the ramus alone, or the ramus with its 
 barbules. German synonyms: words used for ramus also loosely used 
 for barb; also Fiedern erster Ordnung (Haecker, 1896); Fiedern (Ahl- 
 born, 1896). 
 
 r- dist. van. 
 
 js^ms^^m 
 
 .ihir'-fMii 
 
 ■^-- vil. 
 
 — prox. van. 
 
 Fig. B. Proximal half of barb of duck. Abbreviations: dist. v., distal vanule; 
 prox. roi(.. proximal vanule: ;■.. ramus: viJ., villi. 
 
 Ramus (figs. B and C). A primary branch of the shaft, forming the main 
 stem or lamella of a barb, upon which are normally borne barbules. 
 Synonym: barb (see above); secondary quill (Mascha, 1905). German 
 synonyms: Aeste (Nitzsch, 1867; Gadow, 1891; Wiedersheim, 1909); 
 Strahlen (Studer, 1878; Davies, 1889): Fiederlamelle (Ahlborn, 1896); 
 Pasern (Cuvier, 1809); sekundare Kiele (Mascha, 1904). 
 
252 
 
 University of California Publications in Zoology [Vol. 13 
 
 d. ridge 
 
 Fig. C. Cross-section of hypothetical barb. Ab- 
 breviations: dist. I., distal ledge; 
 d. ridge, dorsal ridge; gr., groove for 
 insertion of distal barbule; prox. I., 
 proximal ledge; v. ridge, ventral ridge. 
 
 Ventral Ridge (figs. B and C). A horny keel on 
 the ventral side of the ramus, usually nar- 
 row, though sometimes very highly developed 
 (Strong, 1902; Mascha, 1905). German syno- 
 ridee '^ytn: Hornleiste (Mascha, 1904). 
 
 Ledge (fig. C). Longitudinal grooved ledges on 
 
 the lateral sides of some rami, into which 
 
 ^10- C the barbules fit and which tend to hold them 
 
 in place. Indefinitely called "ridges" or "longitudinal ridges" by Mascha 
 
 (1905). German synonym: Gesims (Mascha, 1904). 
 
 Baebule (figs. D, E and F). A branch of a ramus, collectively forming 
 the vanules. Pennaceous barbules are those which are differentiated 
 into a proximal and distal series which interlock by means of booklets, 
 unless the structure has been secondarily simplified. The proximal 
 barbules (fig. D) are those which are borne on the side of the ramus 
 nearest the base of the feather. The distal barbules (fig. E) those 
 which are borne on the side nearest the tip. Downy barbules (fig. F) 
 are those which are relatively long and filamentous, with no interlocking 
 device. Synonym: radius, a common alternative; tertiary fibers (Mascha, 
 1905); hook fibers (= distal barbules) and curved fibers (^ proximal 
 barbules) (Mascha, 1904). German synonyms: Strahlen (Nitzsch, 1867; 
 Gadow, 1891; Wiedersheim; secundare Strahlen (Studer, 1878); Fieder- 
 chen (Ahlborn, 1896); tertiare Fasem (Mascha, 1904); Hakenfasem 
 (= distal barbules) and Bogenfasern (= proximal barbules) (Mascha, 
 1904). 
 
 r-n. h r-tl. r^ pen. 
 
 Fig. D. Diagrammatic distal barbule. Abbreviations: 6., base; d. oil., dorsal 
 cilia; fl., flange; h., booklets; n., nucleus; pen., pennulum; v. oil., 
 ventral cilia; v. t., ventral teeth. 
 
 Fig. E. Diagrammatic proximal barbule. Abbreviations:. 6., base; d. sp., 
 dorsal spines; fl., flange; «., nucleus; pen., pennulum; v. t., ven- 
 tral teeth. 
 
1916] 
 b. 
 
 Chandler: Structure of Feathers 
 pen.. 
 
 253 
 
 Fig. F. Diagrammatic downy barbule. Abbreviations: attach., attachment 
 with barb; 6., base; internod., internode; nod., node; pen., pennu- 
 lum; pr., prongs; vil., villi. 
 
 Vanule (fig. B). A new term here used to designate collectively all the 
 barbules of either the distal or the proximal series, bearing the same 
 relation to the barb that the vane bears to the feather plate. Hitherto 
 referred to only as the "vane" of the barb. 
 
 Base (figs. D, E and P). The proximal portion of a barbule, which is 
 more or less lamelliform; in distal barbules the portion proximal to 
 the booklet cells, in proximal barbules the portion proximal to the 
 bend occurring just beyond the ventral teeth, and in down barbules 
 the short flattened portion at the junction with the ramus. Synonym: 
 lamella (Newton, 1899). Otherwise referred to only by descriptive 
 phrases. German synonym: Anfangsteil (Mascha, 1904). 
 
 Pennulum (figs. D, E and F). A new term here used to designate the 
 more or less attenuated distal portion of a barbule, bearing the hook- 
 lets and cilia, or, in the case of down, the nodes. Synonym: tip (Chand- 
 ler, 1914). Otherwise referred to only by descriptive phrases. German 
 synonym: Endteil (Mascha, 1904). 
 
 Flange (fig. D and E). The thickened dorsal edge of the bases of pen- 
 naceous barbules, generally recurved In proximal barbules, and fre- 
 quently so in distal barbules also (Wray, 1887). Synonym: recurved 
 margin (Strong, 1902), and other descriptive phrases. German syno- 
 nym: Rinne (Mascha, 1904). 
 
 Dorsal Spines (fig. E). Recurved spines on the flange of proximal bar- 
 bules, opposite the ventral teeth. Synonym,: toothlike processes 
 (Mascha, 1905). German synonym: Zahnforsatze (Mascha, 1904). 
 
 Baebicbls (figs. D and E). Outgrowths of the cells of the linear series form- 
 ing pennaceous barbules, usually projections from the anterior dorsal 
 or ventral corners of the cells. Used by Nitzsch (1867) and Pycraft 
 (1893) to designate cilia only, but more commonly used in the broader 
 sense here accepted. Synonym: cilia (sometimes used in this broad 
 sense). German synonyms: Hakchen, Wimpern, of general use. 
 
 HooKLETS (fig. D). "Ventral barbicels which are strongly hooked at the 
 tip, occurring only on the proximal portion of the pennulum of distal 
 barbules. Hooklet-bearing cells never possess dorsal barbicels. German 
 synonym: Hakchen, (Gadow, 1891; Nitzsch, 1867); Haken (Mascha, 
 1904). 
 
 CtLiA (fig. D). Pennular barbicels, dorsal or ventral, occurring on distal 
 barbules distal to the booklets, and often on proximal barbules of the 
 outer vane of highly developed feathers. German synonym: Wimpern 
 (Nitzsch, 1867; Mascha, 1904): Hakchen (Studer, 1878). 
 
254 University of California Publications in Zoology [Vol. 13 
 
 Ventral Teeth (figs. D and E). Anteriorly projecting, ventral, basilar bar- 
 bicels of both distal and proximal barbules of nearly all birds, often 
 lobate or leaflike in distal barbules, usually toothlike in proximal bar- 
 bules. Synonym: toothlike processes (Wray, 1887); ventral lobes 
 (Mascha, 1905). German synonym: ventrale Lappen (Mascha, 1904). 
 
 Flexulks (pi. 17, fig. lOe). A new term used to designate the curved bar- 
 bicels occurring on the dorsal edge of the bases of distal and proximal 
 barbules of the trunk feathers in some groups of birds (see p. 272). 
 Hitherto apparently unknown. 
 
 Nodes (fig. F). The junction of the cells of the pennulum of down bar- 
 bules, usually characterized by swellings or outgrowths of some sort. 
 
 Prongs (fig. F). Short, spiny outgrowths at the nodes of the down of 
 many birds, differing from other barbicels in that three or more may 
 occur on the distal end of a single cell, whereas there are never more 
 than two cilia or other kinds of barbicels on a single cell. 
 
 V. Methods 
 
 After experimenting with various methods of preparing feathers 
 for microscopic study, especially the barbules, it was found that in 
 most cases the examination of dry mounts of barbs and barbules 
 gave entirely satisfactory results. This was at the same time so 
 simple, and took so little time in preparation, that it was possible 
 to examine the microscopic structures of the feathers of a very large 
 series of birds, and thereby to determine with considerable precision 
 the constancy and uniformity of characters in various groups. 
 
 The barbs were first studied under the microscope with their 
 vanules intact. The vanules were then spread backward in order 
 to separate the barbules for individual study, this being done by 
 merely drawing the barb, tip first, between the thumb and forefinger. 
 With a scalpel some of the barbules from each vanule were scraped 
 off from the region of the barbule which it was desired to study, 
 and mounted dry under a cover glass. In this way a considerable 
 number of individual barbules could be separated, and as they would 
 lie in all sorts of positions, their general form could be studied 
 readily from such a preparation. The morphology of heavily pig- 
 mented structures could be studied more easily when mounted in 
 balsam. In some cases also barbules were mounted in balsam in 
 order to determine whether certain appearances were due merely 
 to pigmentation, or to structural modification, and to determine 
 the effect of oils of low refractive index on color-producing mechan- 
 isms. The methods of treating individual birds and groups of birds 
 to determine their epiphyologic characters will be discussed at the 
 beginning of Part II. 
 
^^^^] Chandler: Structure of Feathers 255 
 
 Part I 
 GENERAL MORPHOLOGY 
 
 I. Plumules 
 1. Unspecialized Plumules 
 
 a) Occurrence and Distribution. — As remarked above,, from a 
 general survey of the feathers of a large number of species of birds, 
 it is evident that certain generalizations regarding feather structures 
 may be made. It is the intention of this portion of the paper to 
 describe the general characters of various kinds of feathers, and to 
 discuss briefly the range of modifications exhibited by them and their 
 several parts. 
 
 , — Plumules are small downy feathers which are usually completely 
 covered iTy the contour feathers in adult birds. Their distribution 
 on the body differs a great deal in different kinds of birds. They 
 may be (1) evenly distributed over the whole body, both in the ap- 
 teria, and in the pterylae between the contour feathers; (2) sparsely 
 or unevenly scattered over the whole body; (3) confined to 
 the apteria; (4) confined to the pterylae (only in Tinamidae) ; or 
 (5) absent entirely. The table on page 256 shows the nature of the 
 distribution of plumules in the various groups of birds, the data 
 being derived from Gadow (1891), Beddard (1898), and others. 
 
 In looking over this table jit seems evident that a uniform dis- 
 tribution of plumules is to be considered a primitive condition, yet 
 in all of the ratite birds, which have usually been considered the 
 most primitive, they are absent entirely. It seems te-«ie that this 
 may be explained in one of two ways: either that the ratite birds 
 have degenerated from a higher type and have lost their plumules 
 concomitant with a simplification of their contour feathers from a 
 pennaceous to a downy type, or that the ratite birds show a condition 
 of plumage more primitive than any other birds, and that in the 
 course of evolution the downy contour feathers of these birds devel- 
 oped along two separate lines, one leading to the soft, fluffy, almost 
 shaftless'. plumules in both pterylae and apteria, the other to the 
 highly specialized contour feathers in the pterylae only.\ Further 
 
256 University of California Publications in Zoology [Vol. 13 
 
 DISTRIBUTION OP PLUMULES 
 
 3 
 ■ae !>. 
 
 Group g| J, -3 
 
 S vL S * .2 
 ox? o ^ f< 
 jM (3 ly "^ * 
 
 S 03 "d "if ^ 
 
 [=£ &£ <i 
 
 Struthioniformes 
 
 Rhelformes 
 
 Casuariiformes 
 
 Crypturiformes 
 
 Apterygiformes 
 
 Spheniseifonnes + 
 
 Colymbiformes + 
 
 Procellariiformes .... + 
 
 Clconllformes 
 
 Steganopodes + 
 
 Ardeae + 
 
 Clconiae + 
 
 Plioenicopteri + 
 
 Anserlformes :. + 
 
 Falconiformes + 
 
 Galliformes + 
 
 Opisthocomi + 
 
 Mesaenatldes +(?) 
 
 Gruiformes +or + 
 
 Charadriiformes 
 Laro-llmlcolae 
 
 Alcidae + 
 
 Others + 
 
 Pteroclo-Columbae 
 
 Cuculiformes 
 
 Psittaci .~. + 
 
 Cucull 
 
 Coraciiformes 
 
 Coraciae 
 
 Alcedinidae + 
 
 All others 
 
 Striges + 
 
 Caprlmulgi + 
 
 Mlcropodii + 
 
 Trochilldae 
 
 Colli and Trogones 
 
 Passerif ormes and 
 Pici 
 
 CO a 
 
 + 
 + 
 + 
 
 +, very large 
 
 -, or rudimentary 
 
 + 
 + 
 +, rudimentary in Diomedea 
 
 +, or rudimentary 
 
 + 
 
 variable 
 
 +, well-developed 
 
 -, rudimentary in a few genera 
 
 +, - in Pandion and Cathartidae 
 
 +, large or small 
 
 + 
 
 variable, usually present 
 
 + 
 + 
 small or rudimentary 
 
 +, large 
 
 -. or rudimentary 
 
 +, often rudimentary 
 -, rudimentary in Aluco 
 small or - 
 
 + 
 + 
 
 +, not highly developed 
 
 evolution, if this hypothesis be true, resulted in the segregation of 
 contour feathers into tracts, and the reduction of plumules, first 
 between the contour feathers, and finally on the whole body, culmi- 
 
1^1^] Chandler: Structure of Feathers 257 
 
 nating iiir1;lfH~c<^ditKffl^found in passerine birds and allied forms. 
 There-is further evidence in support of the latter alternative in that, 
 so far as I have been able to discover, 'flloplumes also are totally absent 
 in the Eatitae, while, so far as is known, they are present, associated 
 with contour feathers, in all other groups of birds. 
 
 b) Structure. — In general structure plumules are jemarkably con- 
 stant^not'only on different parts of the body, but also throughout the 
 entire class of birds. On different parts of the body of an individual 
 the only appreciable modification is in size, the plumules of the larger 
 apteria usually being the largest. 
 
 The quill in plumules is invariably short and inconspicuous. 
 The calamus, which is hollow and barrel-shaped, having a more or 
 less inflated appearance, is usually entirely imbedded in the skin. 
 The shaft is always short and poorly developed, very soon breaking 
 up entirely into barbs in a more or less fan-shaped manner, and it 
 is plainly evident, in the majority of cases, that the thin, flat, more 
 or less subtriangular shaft is to be looked upon merely as a basal 
 coalescence of the barbs. The plumules possess an aftershaft in 
 groups which are characterized by the presence of an aftershaft in 
 the cbntour feathers, even if only rudimentary in the latter. Since 
 many of the birds which lack an aftershaft are also devoid of plu- 
 mules, it is rare to find the latter with a single shaft. Owls, which 
 lack an aftershaft on the contour feathers, with the exception of a 
 rudimentary one in Aluco, have plumules with only one shaft, a 
 dense cluster of barbs springing from the sides and ventral lips of 
 the superior umbilicus. Pelecanus was stated by Nitzsch (1867), 
 and restated by other authors, to have plumules with no shafts. This 
 is not strictly true. Pelecanus erythrorhynchus has plumules with 
 two fairly well-developed shafts, equivalent to each other, about 
 1.6 mm. long, which possess a brown pigment, the rest of the 
 plumule being unpigmented. In Phalacocofax (P. penicillatus), how- 
 ever, the plumules almost lack a shaft, the latter structure being 
 so rudimentary that it is actually wider than long. In the Tetrao- 
 nidae and some other galliform birds, where the aftershaft of the 
 contour feathers has its shaft very highly developed with two dis- 
 tinct vanes, the plumules have the shaft likewise developed. In 
 Lophortyx, for instance, both shafts of the plumules reach a length 
 of six or seven millimeters, in spite of the small size of the feathers. 
 As pointed out by me (1914), the shaft and aftershaft of plumules. 
 
258 University of California Publications in Zoology [Vol. 13 
 
 when both present, are nearly equivalent in size and are practically 
 indistinguishable from each other either by structure or position. 
 
 The rami of plumules are extremely long, slender, filamentous, 
 and very numerous, the cellular structure not apparent, and with 
 no edges or dorsal or ventral ridges. The barbules are always of 
 downy type, and have the same structure as the downy barbules 
 of the contour feathers, being of the type found on the aftershaft 
 when this differs from the downy portion of the feather plate, as in 
 gallinaceous birds. As a rule the downy barbules of the plumules 
 are longer and more numerous than those of the contour feathers 
 of the same species, but the difference is often inappreciable. In 
 some genera, e. g., in Circus, the barbules of the plumule are more 
 slender than those of the down of contour feathers, and more flexible. 
 The result of the close setting and great length of both rami and 
 barbules, and of their slender, flexible nature, characteristic of most 
 plumules, is a very dense, cottony structure which eminently serves 
 its purpose as a water-proof, heat-insulating covering for the body, 
 as pointed out by me (1914). It is significant that plumules, almost 
 without exception, reach a high development and have a uniform 
 distribution in all water birds. 
 
 2. Powder-down 
 
 Occurring as a frequent modification of plumules is the so-called 
 "powder-down", a description of which was given by me (1914) in 
 the ease of Circus hudsonius. Powder-down, according to Gadow 
 (1891), occurs in the following birds: All Ardeae, Balaeniceps, 
 Bhinochetus, Eurypyga, Mesites, Tinamidae, a few Falconiformes, 
 some Psittaci, Podargus, Leptosoma, Coracias, and only one passerine 
 genus, Artamus. I have also found it in the burrowing owl, Speotyto 
 cunicularia. 
 
 Although sometimes found scattered promiscuously among the 
 plumules, as in Gypaetus and many parrots, powder-down is usually 
 found in more or less well-defined patches. As Gadow (1891) sug- 
 gests, the occurrence of powder-down in such diverse groups of birds, 
 and the wide variety of situations in which it is found on individuals, 
 make it appear that typical plumules, at different times and in 
 different groups, may be modified into powder-down, as the result 
 of some unknown stimulation. 
 
^^^^] Chandler: Structure of Feathers 259 
 
 3. Oil-gland Feathers 
 
 In the majority of birds the oil-gland, occurring on the rump, 
 is furnished with a circlet of feathers at or near its apex, while in 
 others the sides of the glandular swelling are furnished with small 
 feathers and the apical circlet is missing. The presence or absence 
 of this circlet has been used extensively as a taxonomic character. 
 When present the feathers constituting the circlet are of modified 
 plumule type. In Circus hudsonius, for instance, the shaft is entirely 
 missing, the calamus splitting immediately into several divisions, 
 which further split into barbs (see Chandler, 1914). There is evi- 
 dence, in Circus at least, that the feathers in the circlet are definite 
 in number. 
 
 4. Nestling Feathers 
 
 Although no thorough systematic study of the microscopic struc- 
 ture of nestling feathers has been attempted, a brief survey of a 
 few diverse types brings out some interesting facts. The highest 
 development of nestling feathers is displayed in ostriches, in which 
 there is a well-formed calamus. The distal portion of a number of 
 the barbs is more or less expanded and flattened (pi. 13, fig. 2d), 
 giving the plumage of the chick a very coarse, bristly appearance. 
 The barbules are numerous, and similar in structure to those of the 
 teleoptiles, only very much shorter. In rheas, as in ostriches, barbules 
 are borne only on the basal portion of the barbs, the tips being 
 hairlike. 
 
 In carinate birds the structure of the down barbules of nestling 
 feathers is nearly always less specialized than that of the down of 
 adults. In penguins the minute structure of the neossoptiles or 
 nestling feathers is exactly similar to that of the down of the tel- 
 eoptiles (pi. 34, fig. 96), the barbules being filamentous with short, 
 sharp prongs at the nodes (see Studer, 1878). In ducks, e. g.. Anas 
 platyrhynchos, the nestling down differs widely from that of the 
 adults (pi. 35, fig. 104), being exactly similar in form to the down 
 of penguins. The barbules are short and filamentous, with a series of 
 prongs at the nodes, those nearer the tip of the barbules being more 
 prominent than those near the base (compare pi. 35, fig. 104, with 
 pi. 34, fig. 96). The yellow color so characteristic of ducklings is due 
 entirely to structural interference of light. In rails, although the 
 adult down is widely different from that of either ducks or penguins, 
 the nestling down is very similar to that of both these birds, the char- 
 
260 University of California Publications in Zoology [Vol. 13 
 
 acteristic, black color being due to a uniform distribution of pigment, 
 even in the prongs, thus differing markedly from the adults. The 
 nestling down of Phalacocorax is hardly distinguishable from that 
 described for the other water birds, some of the feathers being black, 
 due to an even distribution of pigment in the barbs and barbules, a 
 few remaining white. In gallinaceous birds, e. g., Dendragapus, the 
 nestling down is not quite so primitive, the barbules being longer, 
 with slightly swollen nodes and very inconspicuous prongs, but with 
 evenly distributed pigment. 
 
 From an examination of these few types, it may be safely con- 
 eluded that neossoptiles show a much narrower range of modification 
 in the minute structure of their down than do the teleoptiles, whether 
 plumules or contour feathers. The fact that the structure of adult 
 down in penguins is similar to the nestling down of not only pen- 
 guins, but also of ducks, rails, and cormorants, may be an argument 
 in favor of the primitive nature of the former birds. 
 
 II. FiLOPLUMES 
 
 1. Occurrence and Distribution 
 
 Filoplumes are in some ways the most remarkable modifications 
 of feathers found on birds. Although with a very few exceptions 
 they are excessively slender and very difficult to see with the naked 
 eye, and never developd in sufficient number to be of any possible 
 mechanical use as a covering or support, these inconspicuous feathers 
 are remarkably constant, in some degree of development, in all birds 
 except the ratites. Nitzseh (1867) states that they are probably 
 present in all birds, as he has never looked for them in vain, when 
 the necessary trouble has been taken to find them. This statement, 
 though generally accepted by ornithologists, needs further corrobora- 
 tion. I have been unable to find them in the dried skins of a number 
 of birds, though they may have been present, but so reduced as to 
 be very difficult to discern amongst the other feathers. Such an 
 apparent lack of filoplumes occurred in two species of Pelecanus (P. 
 erythrorhynchus and P. calif omicus) , in Aechmophoriis occidentalis, 
 and other species. It may be stated positively that they are not 
 present in ostriches or cassowaries, and probably not in any of the 
 ratite birds. Nitzseh (1867) described filoplumes from cassowaries, 
 stating that they were coarse, much flattened structures, very differ- 
 ent from the filoplumes of other birds, and this has been widely 
 quoted by other authors. Thorough examination of ostriches, both 
 
■^^■^^^ Chandler: Structure of Feathers 261 
 
 young and adult, as well as of the back and breast of a cassowary, 
 failed to show any filoplumes whatever. What Nitzsch very probably 
 mistook for filoplumes are the tips of feathers just growing out, which 
 give exactly the appearance described by him for filoplumes. 
 
 When present these anomalous feathers are always associated 
 with contour feathers, though not always accompanying all feathers 
 of this type; in Circus hudsonius, for instance, they could be found 
 only in the dorsal, lumbar, and caudal tracts. When present they 
 grow out in groups from the dorsal side of the socket of the contour 
 feather with which they are associated. There may be only one or 
 two of these in a group, or as many as ten in some water birds, ac- 
 cording to Nitzsch (1867). In Circus hudsonius there are from five 
 to eight in a bundle, no two in a bundle usually being of the same 
 length. 
 
 2. Structure 
 
 As shown by Pycraft (1909), filoplumes are really degenerate 
 feathers, only the barbs of the extreme tip of the feather becoming 
 attached to the slender shaft. The other barbs are formed more or 
 less perfectly, but through a defect in development never become 
 attached to the shaft. Nitzsch reports a case in which some downy 
 barbs and barbules were found near the base of the filoplumes in a 
 specimen of "Gallus bankiva domestica." It is very probable that 
 this was an abnormal case in which the development was not arrested 
 as usual, or it may have been a filoplume which had not completed 
 its development, and had not yet lost its deciduous barbs. 
 
 Unlike either plumules or contour feathers, filoplumes never have 
 the quill divided into calamus and shaft, the base not becoming hollow 
 and pithy, and the superior umbilicus being absent. The only differ- 
 entiation at the base of a filoplume is a slight widening and flattening 
 (see Chandler, 1914, pi. 16 fig. 2). 
 
 As a rule, full-grown filoplumes have exceedingly slender shafts, 
 often ridged and pitted to give a silvery appearance like a fiber 
 of silk, and they are naked except at the extreme tip, where a few 
 rudimentary barbules are borne directly on the shaft, or on two 
 or three rami which may be given off. In some species they are 
 pigmented, e. g., in the robin, Planesticus migratorius, while in closely 
 allied species, e. g., the bluebird, Sialia mexicana occidentalis, they 
 have the typical, unpigmented, silvery color. 
 
262 University of California PiMications in Zoology [Vol. 13 
 
 Although, usually entirely covered by the contour feathers, 
 filoplumes are occasionally developed to an extraordinary degree. 
 In many passerine birds they may be seen with a hand-lens project- 
 ing beyond the tips of the contour feathers on the nape, while in 
 other closely allied species they may not be exposed at all. In 
 Planesticus migratorius and Sialia mexicana occidentalis, for example, 
 they are plainly visible in the unruffled plumage, while in Hylocichla 
 guttata they are not exposed at all. In many genera of Pycnonotidae 
 they are long and hairlike, giving a conspicuously hairy appearance 
 to the plumage in the region of the nape and upper back. 
 
 The only place in which I have found filoplumes really conspicuous 
 is in the plumeige of cormorants, more or less in all of the species 
 examined, especially on the neck and upper back, although to some 
 extent on the breast, belly, and rump as well. In these birds many 
 of the filoplumes are long and largely exposed, and have the vanes 
 developed to a very unusual extent. In males they are pure white and 
 show up conspicuously as white streaks against the deep greenish- 
 black color of the contour feathers, while in females they are buffy 
 brown and inconspicuous against the brown plumage. Although 
 their development is very variable, some of them have barbs borne 
 on the terminal four-fifths of the shaft, though there are only about 
 15 per centimeter on each side, i. e., they are 0.6 mm. or more apart. 
 They are set at a very sharp angle with the shaft, so that they make 
 narrow but fairly dense vanes. The barbs bear very numerous 
 barbules, about 35 per millimeter on each side. They are of a filament- 
 ous downy type, but only 0.02 mm. long, and not spread apart to form 
 broad vanules. Although the barbules of the plumules of these 
 species are filamentous, with practically no indication of nodes except 
 at the extreme tip, the nodes on the barbules of the filoplumes are 
 characterized by well-developed sharp prongs, thus resembling the 
 nestling feathers. Though far from what would be expected, filo- 
 plumes are by no means conspicuously developed in allied families 
 of Steganopodes ; in fact, I have searched in vain for them in dried 
 skins of Pelecanus erythrorhytichus and P. calif ornicus, Plotus an- 
 hinga and Phaetkon longicavda. Since filoplumes occur in the most 
 diverse group of birds, and yet attain such a variable degree of 
 development in birds within the same order, it is a natural presump- 
 tion that they are of some use in the economy of nature, and are not 
 
1916] Chandler: Structure of Feathers 263 
 
 merely vestigial or rudimentary structures. No suggestion of a pos- 
 sible use has yet been made. 
 
 III. Contour Feathers 
 
 Under contour feathers, in their various forms and modifications, 
 may be included practically all of the diverse kinds of plumage ordi- 
 narily displayed on the body of a bird. In this category come all 
 remiges, rectrices, coverts, and exposed body-feathers, except in a 
 few instances where filoplumes or plumules are exposed, as in cormor- 
 ants and on the neck of Pelecanus respectively ; also ear-coverts, eye- 
 lashes, rictal and other bristles, and all sorts of ornamental crests 
 and plumes, and other modified feather structures, such as the brush 
 of a turkey, the "wires" of some birds of paradise, the lyre of 
 Menura, etc. Their variety of form is almost limitless, yet they are 
 all modifications of the same fundamental structure. A discussion 
 of the various important types of feathers in a typical bird of fiight 
 has been made for Circus hudsonius by me, (1914) and it is only 
 necessary here to generalize on the conditions found there, and show 
 along what lines phylogenetic modifications of this type have taken 
 place in the whole series of birds. 
 
 i. Bemiges 
 
 a) Shaft. — The most highly specialized feathers, those in which 
 the structure reaches its height of perfection, are the remiges, espe- 
 cially the primaries, of strong-flying birds. These feathers, in all 
 flying birds, have a well-developed quill, differentiated into a hollow 
 calamus and a stiff shaft which is more or less rectangular in cross- 
 section, an.d usually has a groove running along the ventral side, 
 generally quite pronounced at the superior umbilicus and becoming 
 obliterated towards the tip of the feather. The condition of the 
 groove varies to a considerable extent in different groups of birds, in 
 some being broad and shallow, in some narrow and deep, and with all 
 gradations between in others. In the remiges of ostriches the ventral 
 groove of the shaft reaches its maximum size, the shaft in this case 
 being in the form of a half -cylinder, convex above and concave below, 
 while in some of the higher birds, e. g., Coccyzus, there is no groove 
 whatever. These facts at first glance would indicate that a large, 
 wide-open ventral groove is a primitive character, that the absence 
 
264 University of California Publications in Zoology [Vol. 13 
 
 of a groove is a specialized condition, and that the condition of the 
 groove in the shaft could be used to some extent as a gauge of 
 specialization. This, however, does not hold, since a wide variation 
 can be found, not only within a single group, but in the different 
 feathers of a single species. In less specialized wing quills of a 
 female ostrich, for instance, the shaft has a totally different ap- 
 pearance from that found in the plumes of the male ; in the former 
 the shaft is convex above and below, with only a narrow, insignificant 
 groove. In Coccyzus, as mentioned above, there is no ventral groove, 
 while in Geococcyx, of the same family, there is a broad, shallow 
 groove. In the penguins there is not only no groove, but a median 
 keel is developed both above and below on the very broad, flat shaft. 
 In cassowaries, where the remex quills are reduced to bare, stout 
 spines, there is no groove, and the shaft is subcircular in cross-section. 
 Aftershafts are never developed on remiges. 
 
 h) Vanes and Barbs. — ^The vanes of remiges of flight birds are 
 never quite equal, the outer vane always being narrower than the 
 inner, very conspicuously so on the outer primaries, often subequal 
 on the inner secondaries. In many of the best birds of flight, espe- 
 cially those which soar and glide to a considerable extent, there is a 
 further modification of the vanes of some of the outer primaries, in 
 that more or less of the distal portion is narrowed down or "incised" 
 so that the tips of these feathers, when the wing is spread, are 
 separated from one another like spread fingers. In the columbid 
 genus Drepanoptila, the feather plate is bifurcated, there being dis- 
 tally two shafts and four vanes. This anomalous condition, character- 
 istic of the trunk feathers of other genera of the same group of 
 Columbidae, must be regarded as a recent, heritable mutation. 
 
 Usually more or less of the basal portion of the vanes of remiges, 
 as well as of other contour feathers, is downy in character, though 
 often the innermost portion of even the most basal barbs may have 
 pennaceous or transitional barbules, a larger and larger portion be- 
 coming downy as the superior umbilicus is approached (fig. A). In 
 flightless birds various kinds of reduction of the vanes of remiges 
 takes place. In ostriches the remiges are developed in the male as 
 ornamental plumes, in cassowaries they are reduced to stiff, bare spines, 
 with the vanes absent entirely, while in penguins and most other 
 flightless birds they are reduced to the condition of the trunk feathers, 
 and are barely, if at all, distinguishable from them. 
 
1916] Chandler: Structure of Feathers 265 
 
 Although the narrowness of the outer vane in the primaries is 
 brought about partially by an actual shortness of the barb, it is 
 accentuated by the relatively narrower angle which the barbs of the 
 outer vane make with the shaft. In all but the most generalized 
 remiges, there is a tendency for the barbs of the outer vane to be 
 inserted farther apart on the shaft, but at a more acute angle than 
 those of the inner vane. As a rule, the number of barbs per unit of 
 measure changes in a very definite manner, following a mathematical 
 curve analogous to some of those worked out by Pearl (1907) for 
 growth in the whorls of leaves of the aquatic plant Ceratophyllum. 
 Beginning at the tip there is a slight decrease in number per unit 
 of measure, then a very slowly accelerating increase for the greater 
 length of the feather, terminating in a very quickly accelerating in- 
 crease as the superior umbilicus is approached, accompanied by a 
 transition to a downy form. It is interesting to note in this con- 
 nection that the change in number of barbuies per unit of measure 
 on the barbs follows a very similar curve, and probably varies with a 
 similar mathematical equation. 
 
 The barbs of remiges, with the exception of the meager basal 
 downy structure already mentioned, are always highly developed in 
 birds of flight, consisting of a thin lamelliform ramus bearing highly 
 developed distal and proximal vanules (Fig. B). The pith of the 
 ramus, as shown by Mascha (1904), is composed either of a single 
 dorso-ventral plate of cells, one cell in thickness, or of a network of 
 cells, more than one cell in thickness (Fig. C). 
 
 "Without exception, the rami of the inner vane are narrower than 
 those of the outer, though often almost imperceptibly so. Distal to 
 the notch of the incised primaries this difference is especially notice- 
 able, the rami of the outer vane being often as deep as the shaft, 
 while those of the inner vane are less than half as deep. In the 
 majority of birds where the rami are not as deep as the shaft, there 
 are fine ridges on the shaft from the insertion of the ramus to the 
 ventral edge. As pointed out by me (1914), the deep type of ramus 
 is probably the more primitive condition. 
 
 The ventral edges of the rami (fig. C) are produced into horny 
 keels, usually with no evident cell structure, known as the ventral 
 ridges (see Pycraft, 1893; Mascha, 1904; and Stubbs, 1910). Al- 
 though in the great majority of birds this ridge forms only a nar- 
 row, inconspicuous border for the ramus, in a few birds it is extra- 
 
266 University of California Publications in Zoology [Vol. 13 
 
 ordinarily developed as a very thin, translucent film, which bends 
 distally and overlaps the following ramus, giving a smooth, glazed 
 appearance to the under surface of the feather which is conspicuous 
 at the most casual glance. It is thus developed in all of the Anseres, 
 (pi. 33, fig. 28a), and in a number of gallinaceous birds, though in 
 the latter it is by no means constant, being present, for instance, in 
 Bonasa, but absent in Lophortyx. The ventral ridge of the outer 
 vanes of some groups of birds, e. g., Anseres, Falconidae, and some 
 Ciconiae, is further modified by being furnished with irregular villi 
 (fig. C, and pi. 21, fig. 286) on the ventral edge. The rami of the 
 inner vane always have the ventral edge entire or nearly so. 
 
 As shown by Mascha (1904), rami are furnished with a lateral 
 "ledge" which is grooved for the reception of the bases of the bar- 
 bules (fig. C). These are much more highly developed and efficient 
 in some birds than in others, often making it very difficult to scrape 
 off the barbules without tearing off with them a part of the barb to 
 which they remain attached. 
 
 c) Barbides. — The interlocking barbules of a typical remex are 
 of four distinct types, the distal and proximal barbules of the inner 
 vane, and the distal and proximal barbules of the outer vane. 
 
 It is unnecessary here to enter into a discussion of the typical 
 structure of distal and proximal barbules, or of their manner of 
 interlocking. An excellent description of this is given by Pycraft 
 (1893), and a few additional facts of interest are added by Mascha 
 (1904). There are, however, a number of minor details of structure 
 of both distal and proximal barbules which are almost uniformly 
 different in all birds in the inner and outer vane, although apparently 
 this fact has escaped the notice of all previous observers. As a rule 
 the bases of the distal barbules of the outer vane are longer and 
 relatively narrower than those of distal barbules of inner vanes, but 
 this is not always true, the chief difference lying in the pennula. 
 On the inner vane the pennulum of distal barbules as a rule is longer 
 than it is in the outer vane, with fewer booklets, but a larger num- 
 ber of cells with cilia (compare pi. 16, fig. 8a, with fig. 8c and see 
 text-figure P). The most conspicuous difference lies in the dorsal 
 cilia on the proximal portion of the pennulum. Almost without excep- 
 tion, distal barbules of the inner vanes of remiges are characterized 
 by the specialized development of the first two (pi. 20, fig. 20a), 
 and often to a less extent of the third, dorsal cilia (pi. 20, fig. 23a) . 
 These specialized cilia are developed as stout, conspicuous, lobate, or 
 
1916] Chandler: Structure of Feathers 267 
 
 thomlike projections, which are directed more or less distad, i. e., 
 toward the tip of the feather (see plates). In the Falconidae they 
 differ from the other dorsal cilia only in being slightly stouter and 
 more thornlike (pi. 23, figs. 36a, 37a, 38a, 39a, 40a) ; in owls they 
 are well developed but not differentiated from the other cilia (pi. 32, 
 fig. 84a) ; while in a few birds, e. g. trogons (pi. 31, fig. 80a), they 
 are absent entirely. On the outer vane, on the other hand, the dorsal 
 cilia of the proximal portion of the pennulum are always absent, 
 at least on the first two or three cells; very frequently no dorsal 
 cilia whatever are present. Usually, however, following the proximal 
 two or three cells, rudimentary barbicels begin to appear, and these 
 become more and more pronounced distad, the reverse condition to 
 that found on the inner vane. With the exception of these few 
 details, the structure of distal barbules of both inner and outer 
 vanes is usually alike, and both show the same group characteristics. 
 The proximal barbules (fig. B) of the two vanes are nearly always 
 exactly similar in more or less of the basal portion of the barbs, but 
 in the majority of birds they differ in the more distal portion of the 
 barb, sometimes only at the tip, more frequently in from one-third 
 to two-thirds of the terminal portion. Those of the inner vane, and 
 those which are similar to them on the outer vane, have rather long 
 slender bases, considerably longer than the bases of the distals, a 
 series of three to six ventral teeth of differing degrees of develop- 
 ment in different birds, and more or less filamentous pennula with 
 only very rudimentary barbicels if any at all. With a few excep- 
 tions, notably most of the cieoniiform birds, the more distal proximals 
 of the outer vane differ decidedly from the others in the development 
 of a series of ventral barbicels, these being formed as an increased 
 number of ventral teeth, accompanied by a change in form. In 
 many birds these ventral barbicels, homologous to the booklets and 
 ventral cilia of distal barbules, are very large and numerous and 
 highly conspicuous, e. g., in gallinaceous and falconid birds (pi. 23, 
 fig. 38c, and pi. 24, fig. 42e). Perhaps the greatest development is 
 that found in Ceryle alcyon (pi. 31, fig. 79a). In many passerine 
 birds, e. g., in all the Tyrranidae, the outer half of the barbs under- 
 goes a very sudden and conspicuous change from plain to barbieelled 
 proximal barbules (compare plate 33, fig. 92d with plate 33, fig. 93a), 
 this sudden transition including a very marked reduction in the size 
 of the base, and a concomitant simplification of the distal barbules, 
 the booklets of which become obsolete. This change in structure 
 
268 University of California Publications in Zoology [Vol. 13 
 
 produces the fringe, or edge, usually of a paler color, so frequently 
 found on the remiges and coverts of passerine birds. 
 
 Usually the structure of barbules, except for variations already 
 mentioned, varies but little on different portions of the same barb or 
 of the same feather. At the base of the barb there is a decided 
 shortening of both kinds of barbules, while at the tip the change is 
 in the nature of a loss of the perfection of structure. Usually, also, 
 the distal barbules of the inner vane have the specialized dorsal 
 cilia better developed on the terminal than on the basal portion 
 of the barb. 
 
 Surveying the entire class of birds, we find that the pennaceous 
 barbules vary considerably in the different orders and suborders, 
 though usually being fairly constant within the lesser groups, except 
 where modified for color production, or other conspicuous effect. 
 Differences occur in size and shape of the bases, position of nuclei, 
 form of pennulum, and nature of all the different types of barbicels. 
 In tinamous alone a most remarkable modification of the typical 
 vanules occurs in the solid secondary fusion of the pennula of the 
 proximal barbules, except at the extreme tip of the barbule, to form 
 a limiting bar parallel to the barb (pi. 25, figs. 49& and e). Though 
 this surprising modification is absolutely characteristic of all tinamous, 
 not only of the remiges, but of all the other pennaceous contour 
 feathers, I have found no suggestion of it in any other birds, and 
 I have been unable to find any reference to it in the literature. 
 
 2. Bectrices 
 
 "With this brief survey of the conditions found in the remiges of 
 birds, we may now turn to the other groups of contour feathers. 
 Next to the remiges, the most highly developed feathers of the body, 
 in birds of strong and graceful flight, are the reetriees. The macro- 
 scopic form of the tail and of its individual feathers varies con- 
 siderably, and the microscopic structure is far more subject to modifi- 
 cations for special functions than it is in the remiges. In normal 
 reetriees, used in flight for steering and balancing, the structure is 
 very similar to that of the inner remiges, and it is interesting to 
 note that in the middle tail feathers both vanes have a type of struc- 
 ture of barbules similar to that characteristic of the outer vane of 
 remiges. In ratite birds there are no specialized reetriees among 
 the Casuariiformes or the Apterygiformes, while in the Struthioni- 
 formes and the Rheiformes the reetriees are large and developed as 
 
131^] Chandler: Structure of Feathers 269 
 
 ornamental plumes. In penguins and Colymbiformes they are indis- 
 tinct. In a few birds, e. g., Menura, they are transformed into an 
 ornament, although it is more frequently the upper tail coverts that 
 are modified to produce an ornamental tail. In woodpeckers, swifts, 
 and a number of other birds the reetrices have the plate undeveloped 
 at the tip, and the bare shafts enlarged as stout spines to aid in 
 climbing or bracing against a steep surface. Like the remiges, the 
 reetrices never possess aftershafts. 
 
 3. Unspecialized Contour Feathers 
 
 Passing now to the coverts, we find that in them there is a com- 
 plete transition from the remex type of structure to that found in 
 the contour feathers of the trunk, the greater coverts being more 
 like the former, some of the lesser ones very much like the latter. 
 We may pass at once, therefore, to a discussion of the morphology 
 of the trunk feathers. 
 
 a) Aftershafts. — These feathers in the majority of birds are char- 
 acterized by the presence of an aftershaft, and the presence or ab- 
 sence of this structure has been considered of considerable taxonomic 
 importance. The condition of the aftershaft in the various groups 
 of birds is given in the table on page 256. 
 
 A great deal of variation exists, as will be seen, within single 
 suborders or even families. Within the Eatitae there is an extreme 
 variation from a total absence in the ostriches, rheas and Apteryx, 
 to a maximum size, practically equivalent to the main shaft, in 
 cassowaries and emus. Various types of aftershafts occur in carinate 
 birds, the most common form being one with a very short shaft and 
 long, spreading barbs, very similar in form to plumules. In many 
 gallinaceous birds, e. g., in the Tetraonidae, the aftershaft reaches 
 a very high degree of development, its shaft being frequently three- 
 fourths of the length of the main shaft, with its vanes coherent and 
 of even width throughout (fig. A). The usual type in passerine 
 birds, on the other hand, is very different; the shaft is extremely 
 short, with a few short rudimentary barbs near the base, followed 
 by four to eight very long, free barbs, entirely disconnected from 
 each other. The barbs and barbules of aftershafts are always of 
 downy structure, the minute characteristics of the barbules being 
 usually the same as those of the down of the main feather plate, 
 but there are a number of exceptions to this, e. g., in the gallinaceous 
 and passerine birds. In such cases the structure is less specialized 
 
270 University of California Publications in Zoology [Vol. 13 
 
 than that of the down of the feather proper, and differs in not 
 possessing certain specialized characteristics, such as the detachable 
 rings at the nodes found in the more basal barbules of gallinaceous 
 birds (pi. 36, fig. 108), and the fimbriae which characterize the base 
 of the inner barbules in passerine birds (pi. 37, figs. 114 and 115). 
 
 h) Down. — In all but especially modified contour feathers, a vary- 
 ing proportion of the feather plate is downy, the transition from the 
 downy to the pennaceous portion being sometimes gradual, but more 
 frequently abrupt, as shown in text — figure A, the line of demarcation 
 varying a great deal in different feathers. In the lower belly feathers 
 and tail coverts of some birds, e. g., Leptoptilus, the downy struc- 
 ture pervades the entire feather, producing the "semiplumes" of 
 Nitzsch (1867) and others. In Leptoptilus these are the feathers 
 from which the true "marabou" of commerce is derived. Feathers 
 very similar to these are developed in the lower belly region of 
 turkeys, these being employed very extensively as a substitute for 
 "marabou". 
 
 The minute structure of the down varies to a large extent in 
 different groups of birds, the nodes and intemodes both displaying 
 peculiarities which are highly characteristic of different groups 
 (pis. 34-37). 
 
 The structure of down often varies a great deal in a single 
 feather, the specific characteristics being always best displayed by 
 barbules on the inner portion of the distal vanule of the basal barbs. 
 Farther distad on either feather or barb, and on the proximal vanules, 
 the structure is often less specialized, and lacks some of the charac- 
 teristic features of the group. This is well displayed in the down 
 of a turkey, where only the inner portion of the distal vanules of 
 barbs on the basal part of the plate possess the peculiar, charac- 
 teristic, detachable rings at the nodes (pi. 36, fig. 108). The struc- 
 ture of the proximal vanules of the same region of the feather often 
 approximates that of the distal vanules, but is never quite so per- 
 fect. The outer barbules of all the barbs, and all the barbules of 
 the more distal barbs, lose the specialization, becoming finally fila- 
 mentous with the nodes very inconspicuous. Though this is the 
 order of reduction of specialization where such reduction takes place, 
 there are some birds in which the downy structure, though highly 
 specialized, is almost uniform, becoming reduced only at the tips of 
 the barbs, as in the Anatidae. As stated above, the structure of 
 the down of aftershafts and plumules, but not of neossoptiles, is 
 
1916] Chandler: Structure of Feathers 271 
 
 similar to that of the proximal vanules of the downy barbs of the 
 feather proper, in case there is any special modification in the distal 
 vanules, as in gallin'aceous birds. 
 
 c) Pennaceous Barhules. — Concerning the pennaceous portion of 
 contour feathers of the trunk, all degrees of development of structure 
 can be found. In ratite birds, as is well known, there is never any 
 pennaceous structure developed, although the bases of the barbules 
 in Bhea (pi. 13, fig. la) are exceptionally well developed for down, 
 and seem to indicate a transition to or from a pennaceous type of 
 barbule. In typical trunk feathers there is no differentiation of 
 inner and outer vanes, and usually the structure is a mere simplifica- 
 tion of that found in the more highly specialized remiges. In the 
 contour feathers of the trunk, as would be expected, the distal bar- 
 bules are of the type of the outer vane of the remiges, and the proxi- 
 mal barbules of the type of the inner vane of the remiges, often in 
 very degenerate form, these types being the ones showing the lesser 
 degree of specialization. In the trunk feathers the conspicuous basal 
 dorsal cilia are seldom developed on distal barbules, and ventral cilia 
 seldom occur on the proximal barbules (pi. 20, figs. 20e and /). In a 
 great many birds these structures in trunk feathers are very much 
 simpler than they are in the remiges, all of the barbicels being very 
 much reduced or even absent. In distal barbules the cilia often 
 disappear entirely, the booklets are reduced to one or two very weak 
 ones, and the ventral teeth are represented only by a very small, 
 inconspicuous projection (pi. 33, fig. 92e) ; the proximal barbules 
 frequently lose the sharp differentiation between base and pennulum, 
 becoming evenly tapering all the way to the tip (pi. 33, fig. 92/). 
 Such modifications are always farther advanced on the breast and 
 belly feathers than on those of the back, the back feathers often 
 being intermediate between the remiges and coverts on the one hand, 
 and the breast and belly feathers on the other. 
 
 In some birds the pennaceous barbules of trunk feathers have 
 special modifications of their own, and, as might be expected, these 
 are usually more conspicuous and better developed on breast than 
 on back feathers. The most peculiar structural modification charac- 
 teristic of trunk feathers only, and the only one which needs special 
 mention here, is the development of curved dorsal barbicels on the 
 base of both distal and proximal barbules (pi. 17, fig. lOe, 12a, b). 
 Since these barbicels are not homologous with any other types of 
 
272 University of California Publications in Zoology [Vol. 13 
 
 barbieels, and are always of the same curved form, they have been 
 given a special name, flexules. 
 
 Though totally absent in the majority of birds they are very 
 characteristic of several groups, namely, Procellariiformes, Grui- 
 formes, and Laro-limicolae (pis. 17, 26 and 28). They are usually 
 not present on some of the basal barbules, but are generally charac- 
 teristic of a considerable portion of the distal vanule, and usually 
 a little less of the proximal vanule. In distal barbules they first 
 develop at the proximal end of the base (pi. 16, fig. 8e) and progress 
 toward the pennulum, ultimately forming a continuous series with a 
 similar series of pennular dorsal barbieels. This, however, does not 
 happen until the booklets are lost, since booklet cells never possess 
 dorsal barbieels of any sort. The result of this is often a conspicuous 
 break in the dorsal series of barbieels on the barbules which still 
 retain the booklets (pi. 26, figs. 52d, e, and /). In proximal bar- 
 bules the flexules develop first at the distal end of the base as a 
 direct continuation of the pennular series (pi. 16, fig. 52g, h). 
 
 4. Ornamental Plumes 
 
 Frequently some of the contour feathers of the trunk are espe- 
 cially modified as ornamental plumes, the variety of form displayed 
 by them being very great. There is hardly any group of contour 
 feathers which may not at one time or another, in different groups, 
 become modified as ornamental plumes. Among such feathers may 
 be mentioned the diverse kinds of crests developed in many birds, 
 the "aigrettes" of various species of herons, the ruffs and tail plumes 
 of pheasants, the gorgeous upper tail coverts of peacocks and tro- 
 gons, and the very great number of feather modifications in the 
 various species of birds of paradise. Nearly all of these modified 
 plumes are produced either by a mere elongation of the feathers 
 concerned, by an even decomposition of the vanes, or, as in the 
 crest of Goura and the upper tail coverts of peacocks, by an uneven 
 decomposition, resulting in the production of ocelli, rackets, etc. 
 
 Although in such decomposed vanes as are found in the 
 "aigrettes" of herons, in the crest feathers of Goura, or in the com- 
 mercial "paradise-plumes" (chiefly the under wing coverts of Para- 
 disea apoda), the barbs are widely separated from each other on 
 the shaft, and appear macroscopically to be devoid of barbules, closer 
 examination shows that a more or less complete series of degenerate 
 barbules are present, closely appressed to the shaft. In very few 
 
1916] Chandler: Structure of Feathers 273 
 
 cases are the barbules lost, except in connection with color pro- 
 duction, or in case of the tips of the barbs being transformed into 
 stiff spines as in the tails of woodpeckers. A farther modification 
 found in contour feathers is the formation of a terminal undivided 
 homy expansion, produced either by the shaft alone, as in certain 
 rail feathers (Bonhote, 1912), by the coalescence of the shaft and 
 both vanes, as in the crown feathers of the curly-headed toucan 
 (Pteroglossus beauharnaisi) , or by the fusion of the shaft with 
 the terminal portion of onlj' the outer vane, as in the "wax tips" 
 of Bombycilla garrula (pi. 33, fig. 95a) . 
 
 5. Ear Coverts 
 
 On the head of most birds there are a number of modifications 
 of contour feathers to serve special functions, and they are won- 
 derfully adapted to serve their particular purpose. 
 
 First among these may be mentioned the ear coverts. The typi- 
 cal structure of these feathers is similar to that described by me 
 (1914) in Circus hudsonius. They are loose-vaned feathers, with 
 the barbs wide apart on the shaft, and the short, awl-shaped, degen- 
 erate pennaceous barbules closely appressed to the barbs, thus pro- 
 ducing a mechanism admirably fitted to catch dust particles and 
 yet not obstruct sound. In birds which have well-developed after- 
 shafts this structure is also present in the ear coverts, but in much 
 modified form. In the Limicolae, herons, hawks, and some others, 
 the aftershaft is greatly developed and almost equals the main 
 feather in both size and structure. In Tetraonidae the aftershaft 
 is reduced to a very small downy pad, scarcely larger than a pin- 
 head, which takes no part in covering the ear. An intermediate 
 condition occurs in Grus, where the basal portion of the aftershaft 
 is densely downy, while a few of the barbs are elongated, with the 
 typical appressed, inconspicuous barbules. In owls and many other 
 coraeiiform and many passerine birds, the ear coverts lack an after- 
 shaft entirely. As has previously been pointed out (Chandler, 1914), 
 the ear coverts are undoubtedly adaptive modifications of contour 
 feathers, which are in a transitional stage of transformation ulti- 
 mately leading to the various kinds of facial bristles and eyelashes. 
 
 6. Facial Bristles and Eyelashes 
 
 The steps in transformation from ordinary contour feathers of 
 the trunk to the highly modified eyelashes of certain birds may 
 
274 University of California Publications in Zoology [Vol. 13 
 
 be traced without a break in such a bird as Circus hudsonius, as 
 has been done by me (1914). As was shown there, after the diminu- 
 tion in number of barbs and reduction of barbules, as is the con- 
 dition in ear coverts, the next step is the complete loss of the terminal 
 barbs and elongation of the shaft into a bristle. Then follows the 
 loss of more and more barbs and stiffening of the shaft, until the 
 latter becomes a stout, unbranched bristle, as in the eyelashes of 
 many birds. Usually rictal, supraorbital, and nasal bristles have 
 some of the barbs still present; in the dense nasal tuft of Corvus 
 the structure is very much like that of ear coverts, except that the 
 barbs are set at a more acute angle with the shaft, thus producing 
 narrower vanes. Comparatively few birds possess eyelashes, but 
 when present they are so modified that in some cases nothing re- 
 mains but the stout, deeply pigmented quill, totally devoid of any 
 barbs or barbules. Such is the case in hornbills, Geococcyx, and 
 some other birds. In birds with aftershafts, although the main 
 shaft is entirely bare, the former is represented by a few small, 
 weak barbs with rudimentary barbules, e. g.. Circus, Cathartes, and 
 some others. 
 
 7. Facial Buffs 
 
 In a few birds, e. g., owls and Circus, facial ruffs are developed, 
 composed of several rows of closely grouped, very compact, curved 
 feathers. The shafts are stiff and inserted almost at right angles to 
 the surface of the body, only the tips being curved so as to lie 
 flat on the contour. The solid compact vanes are made so by the 
 close approximation of the barbs to each other, and by the exceedingly 
 numerous barbules which have well-formed and characteristic bar- 
 bicels, but are short, due to the shortness of the individual cells, an 
 obvious correlation with the close approximation of the barbs. 
 
 IV. Color Production 
 1. Isotely in Production of Colors 
 
 The colors of feathers have been studied by a great many 
 workers, chief among whom may be mentioned Altum (1854a, 1854b), 
 Bogdanow (1856), Fatio (1886), Church (1893), Krukenberg (1882), 
 Gadow (1882), and Strong (1902). As shown by the researches of 
 these men and others, the colors of feathers fall into three cate- 
 
1316] Chandler: Structure of Feathers 275 
 
 gories, namely, pigment colors, structural colors, and compounded 
 colors, produced by combinations of pigment and structure in differ- 
 ent parts of the same barb. 
 
 It is not the purpose of the present chapter to deal with pig- 
 ments or methods of actual color production, except in so far as 
 the morphology of the feather parts is concerned, but to show what 
 different modifications occur in feathers of different groups of birds 
 to produce the same results, i. e., isotely, to use a word coined by 
 Gadow (1911) to mean the attainment of a similar end by different 
 processes in different organisms. 
 
 Colors which are produced by a single pigment, evenly distributed 
 in the rami and barbules, with no objective color effects, seldom in- 
 volve any modification in the morphology of the barbs. For example, 
 in feathers which have light and dark bars in which the colors are 
 of purely pigment origin, there is no appreciable difference in the 
 form of the barbs in the light and dark areas. The only colors 
 which are produced merely by an even distribution of pigment are 
 blacks, browns, including rufous, and lemon yellow. Although red 
 occurs very frequently as a pigment, it is almost always accom- 
 panied by some structural modification. In the Musophagidae there 
 occurs a green pigment, turacoverdin, which is not accompanied by 
 any special structural modification. Grays, tinged with bluish, rang- 
 ing from pale pearl gray to deep slate gray, are usually produced 
 by an uneven distribution of black or dark brown pigment. In 
 gulls and columbid birds, for instance, the characteristic gray colors 
 are produced by conspicuous transverse bars of dark pigment on a 
 transparent background in the barbules (pi. 29, figs. 70c, d). In 
 herons nearly the same effect is obtained by a dilute, even pigmenta- 
 tion in the bases of the barbules, supplemented by elongated unpig- 
 mented pennula (pi. 20, fig. 20e). The same method is employed to 
 produce the hoary color of terns and other birds, except that in this 
 ease the effect of the unpigmented pennula is accentuated by the long, 
 brush-like ventral cilia. A pretty olive-green color is produced in the 
 back feathers of Osmotreron vernans by a combination of slate and 
 lemon yellow, the former being the effect of dark pigment bars in the 
 transparent bases of the barbules, the latter produced by a lemon- 
 yellow pigment in the pennula, which have large blunt ventral cilia 
 (pi. 29, fig. 69a). 
 
 Structural colors, i. e., colors which are produced by modifica- 
 tions of structures causing interference or diffraction of light, may 
 
276 University of California Publications in Zoology t"^"^- ^^ 
 
 be produced by the rami alone, or by the barbules alone. Although 
 the physical principles upon which the color production rests are 
 probably very much the same in all cases, the mechanisms or surfaces 
 for producing it vary to an astonishing extent in different kinds of 
 birds; the same color is by no means always produced in the 
 same way. 
 
 As a rule, white is produced merely by the absence of pigment, 
 the barbules being translucent, or semi-transparent, and producing 
 a white color by the diffusion of light by means of the numerous 
 edges and irregularities of surface of the vanules. In some eases,, 
 however, more complicated mechanisms are resorted to. In Lagopus 
 the barbules from a white feather appear a peculiar fawn-gray color 
 under the microscope by transmitted light, due to the presence of 
 an infinite number of exceedingly small air bubbles in the substance 
 of the barbules (pi. 24, fig. 47ffl). When the latter are broken, (i. e., 
 the homy outer sheath rendered penetrable) and immersed in balsam, 
 the latter substance, which has almost exactly the same refractive 
 index as the substance of the feather, destroys the effect of these 
 bubbles by filling in the air spaces, and it is rendered transparent. 
 In many feathers which have conspicuously white shafts or barbs, 
 all or a portion of the barb is filled with a mass of these minute 
 bubbles, appearing under the microscope dark and opaque by trans- 
 mitted light, but glistening white, like a minature snow bank, by 
 reflected light. Such a phenomenon may be seen on the lower side 
 of the rami of belly feathers of Asnydesmus. 
 
 The silvery straw color found on the outer vanes of the sec- 
 ondaries, wing coverts, and scapulars of Plotus anhinga is produced 
 in an absolutely unique way. The proximal barbules and bases of 
 the distal barbules are black, while the tips of the distals are highly 
 modified, inflated, and without pigment, though scattering the light 
 in the same manner as the rami of Asyndesmus (pi. 18, figs. 13c, e). 
 Like the white rami of the latter, they are rendered transparent 
 when pervaded by balsam. 
 
 Yellow is sometimes produced by pigment alone, especially in 
 such yellows as those of orioles and wood-warblers, and is then usu- 
 ally produced by pigment in both rami and barbules. Many yellow 
 feathers, e. g., the straw yellow of the head and neck of Paradisea 
 apoda, possess little if any pigment, and have their color produced 
 by naked rami with longitudinal grooves, or irregular pits. When 
 crushed they are rendered transparent and colorless, and show no 
 
1^16] Chandler: Structure of Feathers 277 
 
 color by reflected light. More frequently, as in the belly of Myiarchus 
 and Tyramnus verticalis, the color is a combination of yellow pig- 
 ment and the same superstructure as described above. 
 
 Orange and red, like yellow, may be produced by pigment alone, 
 by a combination of red pigment and a structural modification, or 
 by a structural modification with an underlying dark pigment. The 
 simplest red is that produced by a diffuse red pigment in both rami 
 and barbules, with no structural modification, as in Cardinalis cardi- 
 nalis. A much deeper and more striking red is produced by a mere 
 glazing or highly polished surface of barbules or naked barbs fiOlled 
 with red pigment, as in the deep red of Nectarinia famosa, or the 
 "wax tips" of the waxwing. It is a common phenomenon for red 
 feathers to be characterized by comparatively widely separated trans- 
 verse ridges of one sort or another on the barbs or barbules. In 
 Eudocimus ruber, Phoenicopterus ruber, and some other species, the 
 barbules are inflated, possess a rather dilute red pigment, and have the 
 margins of the cells conspicuously enlarged as ridges (pi. 20, fig. 26a). 
 In the fiery red crest of Tyrannus verticalis the red pigmented 
 barbs have similar transverse striations, produced by rudimentary 
 scale-like barbules, arrested in their development, and fused with the 
 ramus. In hummingbirds only, so far as I have observed, is red pro- 
 duced by iridescence. In the red gorget feathers of many species of 
 hummingbirds, the color is produced by the greatly developed flange, 
 which is broader than the rest of the base of the barbule. and has no 
 apparent striations (pi. 32, fig. 88d). The underlying color is a 
 very dark olive, quite different from the fuscous brown underlying 
 iridescent green or the rufous brown of iridescent blue, a phenome- 
 non which may be explained by the principle of selective trans- 
 mission and reflection. 
 
 Green is produced in a very large variety of ways. In the 
 Musophagidae alone there is a green pigment, turacoverdin ; in Osmo- 
 treron and a few other birds, some of the feathers appear green 
 from a combination of greenish yellow in the pennula, with some 
 gray or blue color in the bases (pi. 29, flg. 69a). In Melopsittacus 
 a delicate blue-green results from a blue refraction color in the rami, 
 coupled with a greenish-yellow pigment in the barbules. In the 
 vast majority of cases green is an iridescent color, and is the com- 
 monest iridescent color found in birds. The variety of refrangent 
 surfaces is astonishing. In the speculum feathers of ducks, for 
 instance, the cells of the pennula are highly modified into flat, warped 
 
278 University of California Publications in Zoology [Vol. 13 
 
 structures with a very dark pigment (pi. 21, fig. 28i) ; in the green 
 feathers of pheasants and roosters the pennula are modified into 
 spoon-shaped, flat structures with deep pigmentation, with no warp- 
 ing of the individual cells, or constrictions between them (pi. 24, 
 fig. 429^) ; in the peacock, green is produced by barbules which are 
 conspicuously ringed or cross-ridged in both base and pennulum; 
 in hummingbirds by the greatly developed flange of the bases of 
 the barbules (pi. 32, fig. 88d) ; in trogons by smooth, curved bar- 
 bules (pi. 31, fig. 81a), more or less triangular in cross-section, 
 devoid of barbicels of any kind, and entirely given over to the 
 production of color, the effect of tinsel being consequent upon the 
 broken surface, resulting from the irregular curving of the bar- 
 bules; in Nectarinia famosa by short, fiattened barbules, with no 
 barbicels whatever, the entire barbule very closely resembling the 
 pennulum of a green duck feather; and in parrots, coraciids, etc., 
 by the rami alone, in which the greatly developed dorsal ridge is 
 refrangent, the tone of the color varying with the amount of black 
 or brown pigment in the non-refractive barbules. Bronze is produced 
 in manners very similar to those of refraction greens. 
 
 Blue, except the slate blue of Ooura, or bluish-gray as of herons 
 and pigeons, is always a refraction color, produced in nearly all 
 the same ways as is green, but always underlaid by a warmer brown 
 pigment in accordance with the principle of selective reflection. The 
 pretty light blue of Coracias affinis and some other species is pro- 
 duced by a deep violet refraction color in the hexagonal cells of 
 the ramus, each hexagon, or sometimes only scattered ones, being 
 overlaid by a whitish film which is destroyed by scraping or by 
 crushing which is insufficient to destroy the deeper refraction color. 
 In the case of the light blue, the barbules are transparent. 
 
 Various delicate and unusual colors are produced by a combina- 
 tion of structural color in the ramus with a pigment color in the 
 barbules, e. g., in Melopsittacus, already cited, and in the blossom- 
 headed parakeet, Palaeomis cyanocephaltis, in which the delicate 
 changeable color, "resembling the bloom of a peach", is the result 
 of a combination of a blue refraction color in the rami, and a red 
 pigment in the barbules. 
 
 It is apparent from this that a great many different methods 
 have been employed in nature in the acquisition of similar results, 
 totally independent of each other, as much so as are the various 
 types of wings produced in insects, reptiles, birds and mammals. 
 
1916] Chandler: Structure of Feathers 279 
 
 I can think of no more striking example of isotely, the attainment 
 of the same end by different methods in diiJerent groups, than 
 these manifold methods of producing a single color. 
 
 2. Effect of Albinism on Structural Color Modifications 
 
 One of the most remarkable things about the morphology of 
 feathers is the profound change of structure so frequently involved 
 in the production of color effect, in spite of the surprising con- 
 stancy of group characters where no such color modifications occur. 
 It was with extreme interest that the writer examined some of the 
 feathers of an albino mallard, Anas platyrhynchos, to see whether 
 the morphologic modifications involved in the production of the 
 violet speculum would be lost or retained with the lack of pig- 
 ment. It was found that the distal barbules of the outer vane, 
 which in a normal mallard have the pennula highly modified for 
 the production of color (pi. 21, fig. 28a), lacked this modification 
 entirely, and were exactly similar to the normal distal barbules of 
 the outer vane of feathers of this species in which there was no 
 modification for color (pi. 21, fig. 28e). In other words, the con- 
 stitutional factor causing the morphologic specialization of feather 
 structures for the production op color is inseparably bound together 
 with the factor for the accompanying pigment, and if the latter is 
 absent, the feather structures present the normal type of the species 
 in which there are no color modifications. 
 
280 University of California Publications in Zoology I^ot.. 13 
 
 Part II 
 
 SYSTEMATIC 
 
 Introduction 
 
 After making a careful study of the modifications of plumage 
 of a single individual bird of a representative species, namely, Circus 
 hudsonius (Chandler, 1914), and after making a general survey of 
 the entire class of birds to find out in how far the phenomena there 
 found are applicable to birds in general, a systematic study was 
 made of each order of birds in succession to find out what, if any, 
 modifications of feather structure were characteristic of, or peculiar 
 to, the order or other group in question, and to determine the ex- 
 tent of variation to be found in the group, and to work out, if 
 possible, the probable phylogenetic relationships on the basis of 
 feather structure. 
 
 1. Intraspecific and Phylogenetic Modifications 
 
 At the outset it was necessary to determine how much individual, 
 seasonal, or sexual modification in structure might exist within a 
 species. Examination of a series of birds, in any group in which 
 this has been attempted, shows conclusively that the corresponding 
 feathers of any individuals of a species normally show no appreci- 
 able variation from each other, providing the age, sex, season, and 
 other conditions of the specimens be comparable. In other words, 
 comparable specimens of a species possess a definite, typical feather 
 structure which is normally invariable, as much so as are the muscles, 
 bones, or any other system of the body. Abnormalities and wear 
 may produce considerable changes, but they need not be considered 
 at length here. Fault bars in feathers, for instance, resulting from 
 inadequate nutrition or some other unfavorable condition, produce 
 areas of imperfectly formed barbs; albinism, as shown on page 279, 
 inakes a feather which normally possesses a modification in struc- 
 ture for the production of color revert to the normal species type; 
 wear and soiling often give the minute structure a very different 
 appearance; and it is possible that other foreign influences may 
 considerably alter the form and structure of feathers, but these all 
 
1916] Chandler: Structure of Feathers 281 
 
 come under the head of pathogenic conditions, and need no further 
 consideration here. 
 
 Age, seasonal, and sexual variations in feathers occur only when 
 needed for the production of a special result. Just as the greater 
 coverts of a bird may differ in microscopic structure from the middle 
 coverts in order to produce a different macroscopic effect, so in some 
 birds certain of the feathers in the spring plumage may differ from 
 the corresponding ones in the fall plumage, in order to bring about 
 a different total effect. Sexual differences in minute feather struc- 
 ture may likewise exist, but only to produce a macroscopic appear- 
 ance which is a secondary sexual character, e. g., elongated plumes, 
 crests, color effect, etc. Differences in microscopic feather structure 
 are not, in themselves, secondary sexual characters, but are merely 
 employed in the production of more obvious secondary characters. 
 In g, few cases variations in feather structure are employed to pro- 
 duce different effects in different ages, even though in the same 
 seasonal dress, as for instance in many of the orioles, whose plumage 
 pattern in the spring of the second year differs from that of the 
 third year. Such changes are rare and occur only in the first few 
 years; when the ultimate adult plumage is attained, no further age 
 variations occur. 
 
 As a rule, there are no considerable variations in the feather 
 structure of different species of the same genus, except, as in the 
 case of intraspeeific variations, when instrumental in the production 
 of some larger specific difference. Species, of course, are by no 
 means of equal rank, and in subspecies or in slightly differentiated 
 species feather structure, per se, cannot be used as a taxonomic char- 
 acter, although very slight differences in similar feathers do some- 
 times exist in widely different species of a single genus. Moreover, 
 generic differences in feather structure may usually be passed over, 
 since they are ordinarily so slight that they cannot positively be 
 distinguished at all, or only with intensive study, and then only in 
 case it is certain that the portion examined comes from an exactly 
 similar part of a corresponding feather. 
 
 In all groups higher than genera, however, epiphyologic differ- 
 ences may almost always be detected. In other words, it is usually 
 possible to distinguish, by details of feather structure, any feather 
 of a specimen of a given family from any approximately similar 
 feather of a specimen of another family, even if in the same sub- 
 order. The amount of differentiation, however, is extremely vari- 
 
282 University of California Publications in Zoology [Vol. 13 
 
 able, in some cases being scarcely noticeable, while in others it is 
 very apparent. In the Steganopodes, for instance, the difference in 
 feather morphology in some of the different families is very great, 
 while in the families of Passeriformes, which, as a matter of fact, 
 are hardly more than supergenera, it is extremely difficult to dis- 
 tinguish between even widely separated ones. This difference in 
 degree of differentiation also holds true for groups of higher rank. 
 As intimated above, to be comparable the feathers whose parts are 
 to be compared must be approximately similar, since there is fre- 
 quently more variation between different kinds of feathers on a 
 single body than between corresponding feathers of birds of different 
 orders. For example, the barbules of a remex of Larus differ in 
 their minute structure from those of a breast feather of the same 
 genus far more than they differ from those of a remex of a loon, 
 for instance. 
 
 2. Classification Adopted 
 
 The problem of what recognized system of classification to follow 
 in the study of comparative feather morphology presents itself at 
 this point. To the mind of the writer the system which represents 
 most clearly the true relationships of birds according to the present 
 status of our knowledge concerning them, and one that is coming 
 into very general favor with ornithologists in this country as 
 well as in Europe, is that presented by Knowlton and Ridgway 
 in the Birds of the World (1909). This classification, as stated by 
 Knowlton, is essentially the same as that used by Gadow (1891), 
 modified in some details by the later researches of ornithological 
 workers. Although this classification was adopted in the present 
 study as a mere working basis, it was found that as far as feather 
 morphology was concerned it is apparently a more natural grouping 
 than any other; yet, as will be shown in the following pages, there 
 are some possible changes in it suggested by feather structure, and 
 a hypothetical revision of it, based primarily on the latter, will be 
 suggested at the close of this paper. 
 
 In the systematic discussion of the various groups, the grouping 
 and succession used by Knowlton has been used with only two ex- 
 ceptions. The Struthioniformes, Eheiformes, Casuariiformes and 
 Apterygif ormes have been included under a common heading Ratitae, 
 as has usually been done, while the Crypturiformes have been dis- 
 sociated from these and placed immediately after the Galliformes, 
 
^^1^] Chandler: Structure of Feathers 283 
 
 where, according to their epiphyology, they seem to belong. The 
 classification as here used is as follows: 
 
 CLASS AVES 
 
 Subclass Neornithes 
 
 I. Ratitae 
 
 Order Struthlonlformes ' Cf- 
 Rheiformes 
 Casuariiformes 
 Apteryglformes _ ] ,,, 
 
 II. Carlnatae 
 
 Order Sphenisciformes 
 Colymbiformes 
 Procellariiformes 
 Ciconilformes 
 Suborder Steganopodes 
 Ardeae 
 Ciconiae 
 Phoenicopteri 
 Order Anserlformes 
 Suborder Anseres 
 
 Palamedea&v 
 Order Falconlformes 
 Suborder Cathartae 
 Gypogeranl 
 Acclpitres 
 Order Galliformes 
 Suborder Galli 
 
 Turnices 
 Order Crypturlformes 
 Gruiformes 
 Charadriiformes 
 Suborder Laro-llmicolae 
 
 Pteroclo-eolumbae 
 Order Cucullformes 
 Coracliformes 
 Suborder Coraciae 
 Striges 
 Caprimulgl 
 Cypseli 
 Colii 
 Trogones 
 Pici 
 Order Passeriformes 
 
 3. Methods of Comparative Study 
 
 In working over the morphology of feathers in each of the above 
 groups, a brief survey of feather structure was made of a series 
 
284 University of California Publications in Zoology [Vol. 13 
 
 of representative species, representing both the typical and out- 
 lying forms included, and then a species which seemed to be fairly 
 typical for the entire group was selected for careful study, and 
 the minute structure of its remiges and body feathers worked out 
 in detail. So far as possible, except in the Passeriformes, repre- 
 sentatives, usually several, of each included family were examined 
 to determine the constancy of the characters found in the selected 
 type, and where important differences were found in other groups 
 of the same order or suborder, their epiphyology was also worked 
 out in detail. 
 
 Since it was obviously not possible to examine more than a few 
 feathers of each bird studied, similar feathers, as far as possible, 
 were studied in each group taken up, namely, both inner and outer 
 vane of a typical remex (i. e., not a highly specialized outer pri- 
 mary or a weakened inner secondary), a back feather, and a breast 
 feather, though in many cases the latter two were so similar that 
 they did not merit separate descriptions. In other words, the method 
 of study of groups has been: (1) a detailed study of represen- 
 tative feathers of a type, and (2) a study of a number of other 
 selected species, to determine the constancy or modifiability of the 
 characters observed in the type, and to discover the presence or 
 absence of further or different modifications. A discussion of the 
 relationships suggested by feather morphology, and a review and 
 summary of the epiphyology is given at the end of the section deal- 
 ing with each group especially treated. 
 
 I. Ratitae 
 
 Although there has been some doubt concerning the natural asso- 
 ciation of all the so-called ratite birds into a single group, as far 
 as feather structure is concerned, this grouping seems to be en- 
 tirely permissible, providing the Crypturiformes, which Knowlton 
 placed with them, be removed. The following characters are com- 
 mon to the entire group, and as far as we know are not present, 
 except as noted, in the adults of any other birds: (1) plumage uni- 
 form, not segregated into pterylae (found only in Sphenisciformes 
 and Palamedeae among carinate birds) ; (2) total absence of differ- 
 entiated plumules and filoplumes; as far as known, both these types 
 of feathers are never missing simultaneously in other birds; (3) en- 
 tire absence of true pennaceous structure in any of the feathers, 
 
1916] Chandler: Structure of Feathers 285 
 
 the barbules in some species being more or less intermediate be- 
 tween a downy and a pennaceous type. 
 
 1. Order STRUTHIONIFORMES 
 PI. 13, Fig. 2 
 
 This group, which includes only the ostriches, of which four 
 closely related species have been described, has a great many 
 peculiar epiphyological characters, most of which, it seems to me, 
 may be considered primitive, rather than secondarily acquired 
 degenerate conditions. They may be enumerated as follows: (1) 
 in common with other Katitae, an even distribution of feathers, 
 the only apterium being the central one on the breast, where there 
 is a callosity developed by the bird's habit of resting on its breast, 
 and the total absence of plumules and filoplumes; (2) the great 
 increase in the number of rectrices and remiges, the latter to 36 or 
 more, considered by Beebe (1904) to be a secondary specialization, 
 though by some considered a primitive character; (3) the projec- 
 tion of the remiges beyond the bone instead of fitting into grooves 
 in it as in all carinate birds; (4) the wide angle of insertion of the 
 phalangeal primaries, which in other birds are attached almost 
 parallel to the long axis of the phalanges; (5) the absence of all 
 but one row of under wing coverts; (6) the total absence of after- 
 shafts; (7) the total absence of a typical pennaceous structure in 
 the feathers. 
 
 a) Struthio camelus 
 
 (1) Remiges 
 
 The feathers of ostriches, as already stated, are all of one type, 
 and not differentiated into contour feathers, plumules, and filo- 
 plumes. The aftershaft is entirely lacking. The rectrices and 
 remiges are developed into very large, curling plumes with loose, 
 drooping vanes, but in their minute structure differ in no essential 
 way from any of the body feathers. 
 
 Shafts relatively stout, usually widely and more or Jess deeply 
 grooved beneath. In male wing plumes, for instance, the groove 
 so deep and prominent as to make the shaft C-shaped in cross- 
 section and shell-like almost to tip. Width of the shaft of a 
 small wing plume, 6 to 7 mm. at the base, tapering gradually all the 
 way to the end; its depth about 4 mm., 3 mm. of which is involved 
 in the groove. 
 
 Barbs, which may reach a length of 15 or 20 cm., usually set 
 
286 University of California Publications in Zoology [Vol. 13 
 
 about 8 per centimeter on each side throughout most of the 
 feather, increasing to about 12 or 14 at the base. Rami not lamel- 
 late as in most carinate birds, but more closely resembling the rami 
 of down; no prominent dorsal or ventral ridges. Iniier and outer 
 vanes undifferentiated. 
 
 Bariules (pi. 13, fig. 2a) differing widely in form from those 
 of any other birds, either ratite or carinate, at once recognizable. 
 Not differentiated either into distal and proximal, or outer vane 
 and innner vane types, nor any considerable difference in structure 
 and form, except length, in different parts of feathers, or in feathers 
 of different parts of the body. Barbules not clearly differentiated 
 into base and pennulum, even to the extent of ordinary down 
 barbules, and further differing frpm the latter in being flat and 
 ribbonlike instead of filamentous, .in this particular approaching 
 pennaceous barbules but differing from them in being bilaterally 
 symmetrical. On best developed barbules, no prongs or barbieels 
 whatever, but small rudimentary prongs, as in barbules of body 
 feathers, on weaker ones at base and tip of barbs. Length of bar- 
 bules from 2.5 to 3.5 mm. ; width, about 0.035 mm., this being 
 comparable with that of pennaceous barbules; on an average about 
 25 to 30 barbules per millimeter on each vanule, thus more widely 
 spaced than usual with ordinary down barbules. 
 
 (2) other Feathers of Adult 
 
 The feathers of back, rump, belly, etc., not differing in any 
 considerable degree from remiges. Barbs set closer, about 12 to 18 
 per centimeter throughout length of feather, usually under 5 cm. 
 long, basal and distal ones usually shorter resulting in doubly 
 tapering form of feathers. Barbules of approximately same form 
 as in remiges (pi. 13, fig. 2b, 2c), those of the less well-developed 
 feathers with rudimentary prongs at the junction of the cells, called 
 "vestigial barbieels" by Beebe (1904). Length variable, less than in 
 remiges, usually under 2 jnm. 
 
 Feathers of head and neck small, with elongated, bare, hairlike 
 shafts. Eyelashes present, in form of stiff, coarse bristles, with a 
 few basal barbs. Specialized ear coverts present, similar in general 
 plan to those of carinate birds, the shaft furnished with a series of 
 stiff and elastic bristle-like barbs, entirely separate from each other, 
 arranged like the tufts of a brush rather than in distinct vanes, and 
 barbules very small, rudimentary, and appressed. In all small 
 feathers of head and neck, including eyelashes and ear coverts, 
 elongated, bristle-like shafts naked, but barbs always with complete 
 series of densely set and very short barbules, only 0.015 to 0.03 mm. 
 long, but of typical ribbon-like form. 
 
 (3) Nestling Feathers 
 The nestling feathers of ostriches have exactly the same type of 
 structure of barbules as teleoptiles, which fact furnishes some 
 evidence that the latter are not degenerated pennaceous barbules 
 but are highly developed downy ones, since down barbules are the 
 only ones ever found in neossoptiles. The barbules of the latter 
 
1^16] Chandler: Structure of Feathers 287 
 
 (pi. 13, fig. 2c) differ only in their shortness, reaching a length 
 of considerably less than 1 mm., the width and flattened ribbon-like 
 form remaining the same. In the nestling feathers many of the 
 barbs bear barbules only near the base, the terminal portion being 
 extended hairlike or expanded into a more or less curled, flattened 
 plate (pi. 13, fig 2d). Duerden (1911) gives an interesting account 
 of the sequence in the plumages of ostriches. 
 
 i) Relationships 
 
 As has been shown, the feather structure of ostriches seems to 
 indicate a primitive rather than a degenerate condition. Their 
 wings, which have no specialized pennaceous remiges, and could 
 have, no lifting function, are used for aiding the bird in running 
 against the wind, as suggested by Beebe (1904). This use is highly 
 suggestive of a possible course of evolution of fiight. When once the 
 remiges had become pennaceous, nothing further would stand in 
 the way of their being used for true flight. Beebe (1904) looks 
 upon this use of the wings as a half return to the lifting function 
 of the wings in the flying ancestors which he assumes for the 
 group, a view which seems to me to involve so complicated a path 
 of evolution as to require very strong positive evidence to support it. 
 The same author remarks that "vestiges of barbicels" can easily 
 be distinguished. He evidently considered the downy feathers of 
 ostriches as being derived from pennaceous feathers, though nothing 
 in their structure or arrangement, it seems to me, need be inter- 
 preted as suggesting this. The barbules, while less specialized 
 than typical pennaceous barbules and more specialized than simple 
 down barbules, are not intermediate, and might be more easily 
 looked upon as marking the end of a short path of evolution of 
 their own, than as degenerate forms of either of the other types. 
 If the contour feathers of ostriches are not derivatives of pennaceous 
 feathers, then ostriches are not descendants of flight birds, and their 
 striking primitive characters need not be looked upon as secondarily 
 acquired. The absence of plumules, flloplumes, and aftershafts, the 
 even distribution of feathers over the entire body, and the similarity 
 of the neossoptiles to the teleoptiles, as well as the general form of 
 the barbules, all suggest the possibility of the ostriches not being 
 derived from birds with pennaceous feathers, and therefore not 
 from flight birds. 
 
288 University of California Publications in Zoology [Vol. 13 
 
 c) Summary 
 
 The ostriches, in addition to the characters common to all Ratitae, 
 have the following characters: 
 
 (1) Aftershaft absent. 
 
 (2) Types of barbules similar on all feathers of both nestling 
 and adult. 
 
 (3) Barbules of elongate, ribbon-like form, more or loss inter- 
 mediate between an ordinary downy and a pennaceous type, but dif- 
 ferent from either, with no differentiation of base and pennulum, 
 and no barbicels except rudimentary prongs in body feathers. 
 
 (4) Possibility of their not being derived from flight birds 
 strongly suggested by epiphyology. 
 
 2. Order RHEIFORMES 
 PI. 13, Fig. 1 
 
 Although grouped as a separate order of the Ratitae, equivalent 
 to any of the other three, the rheas are much more closely related 
 to the ostriches than are either to any others of the Ratitae, espe- 
 cially as regards their epiphyology. 
 
 Rheas agree with ostriches, in addition to the common ratite 
 characters, in (1) the large number of primaries (12 to 16 in Rhea), 
 (2) the reduction of the under wing coverts, they being totally 
 absent in Rhea, (3) the absence of aftershafts, and (4) the type of 
 barbules, which, as in ostriches, are intermediate between downy 
 and pennaceous barbules. The chief differences between the two 
 groups in general epiphyologic characters are: (1) the absence of 
 well-developed rectrices in Rhea, (2) the more obtuse angle made by 
 the attachment of the phalangeal primaries in Rhea; (3) the approach 
 to the carinate type of the relation of the remiges to the arm bones; 
 and (4) the better development of the feathers of the head and neck. 
 
 The details of structure of the feathers, as compared with 
 ostriches on the one hand and carinate birds on the other, are 
 exceedingly interesting. 
 
 a) Rhea americana 
 
 (1) Remex 
 Shaft, unlike its condition on some ostrich feathers, finely ridged 
 and grooved on ventral side, with no large conspicuous groove in 
 middle. As a rule, the shaft not as short or heavy relative to feather 
 as in ostriches. 
 
1916] Chandler: Structure of Feathers 289 
 
 Barbs very similar to those of ostriches, with no perceptible 
 ventral or dorsal ridge, and with barbules attached almost at right 
 angles in an even series almost directly opposite each other, and 
 not at obviously different levels as in pennaeeous feathers. Change 
 in number of barbs per unit of measure from base to tip of feathers 
 considerable; about 20 per centimeter at base of feather, dimin- 
 ishing to only 8 or 9 near tip. 
 
 Inner and outer vanes similar. Bariules considerably advanced 
 over those of ostriches in their greater variability in different 
 feathers and parts of feathers, also in their closer approximation to 
 both a pennaeeous and downy type. Set about 35 per millimeter on 
 each side on basal barbs, and only about 20 per millimeter on terminal 
 ones. No differentiation between distal and proximal barbules. The 
 best developed barbules on basal portion of barbs on terminal halves 
 or remiges (pi. 13, fig. la). Length about 2 mm., the basal one- 
 third, more or less, considerably broadened into specialized base, not 
 bilaterally symmetrical, but furnished with a series of ventral 
 prongs or barbicels, the dorsal edge smooth and unbroken. Pen- 
 nulum cylindrical, with more or less well-developed prongs for its 
 entire length. Development of basal portion into a differentiated 
 unsymmetrical base, with distinctly barbicel-like prongs, and of 
 terminal portion into a filamentous pennulum, shows distinct approxi- 
 mation to pennaeeous barbules, at least much nearer than the simple, 
 ribbon-like barbules of ostriches. 
 
 Barbules from middle part of either vane of same feather (pi. 13, 
 fig. Ic) considerably less specialized. Basal portion much narrower 
 with less distinct barbicels, and a much less obvious distinction be- 
 tween flattened base and filamentous pennulum. 
 
 (2) other Feathers 
 No essential differences from remiges in structure of body feathers, 
 but barbs more numerous. On small rump feather they decrease 
 from 40 per centimeter on each side at base to about 22 at tip, in 
 upper back feather less numerous, 30 per centimeter basally to about 
 13 at tip. In these cases number of barbs per unit of measure 
 apparently increases inversely to size of feather, or, in other words, 
 space between barbs is directly proportional to size of feather. 
 Barbules less differentiated into base and pennulum than in remiges 
 (pi. 13, fig. 1&), and shorter, with decided tendency toward ordinary 
 downy type, similar to that of penguins, and to neossoptiles of 
 many water-birds. 
 
 I have had no opportunity to study neossoptiles of rheas, but 
 they are stated by Gadow (1891) to be "buschelformig" as in 
 ostriches, but with a weakly developed shaft. 
 
 b) Relationships 
 
 Like the Struthioniformes, the rheas show characters which 
 might be construed as evidence of their being primitive in their 
 flightless condition and of not being descendants of flying birds. 
 
290 University of California Publications in Zoology [Vol. 13 
 
 As shown above, they resemble the ostriches in many details, and 
 are unquestionably more nearly related to them than to any other 
 Ratitae. In the general arrangement of feathers and in the form 
 of the barbules, while probably, like ostriches, at the end of a 
 short separate path of evolution, they appear to be nearer the line 
 of descent of carinate birds. Special attention is drawn to the fact 
 that the barbules which approach most nearly a pennaeeous type, 
 are in the positions where pennaeeous barbules are most likely to 
 be found at the height of their development in carinate birds, i. e., 
 on the basal portion of barbs beyond the middle of the feather. 
 
 c) Summa/ry 
 
 In addition to common ratite characters, Rheiformes are char- 
 acterized by the following in common with ostriches : 
 
 (1) Absence of aftershafts. 
 
 (2) No under wing coverts (one row in ostriches). 
 
 (3) Unusually large number of primaries. 
 
 (4) A type of barbule which is intermediate between a downy 
 and a pennaeeous type, differing, however, from ostriches. 
 
 They are further characterized by: 
 
 (1) Differentiation of the barbules of different portions of 
 feathers. 
 
 (2) Highest developed barbules with flattened base provided with 
 barbicels on ventral edge only, and filamentous pennulum with prongs 
 similar to those of typical down feathers of penguins. 
 
 (3) Less highly developed barbules with basal portion reduced, 
 thus becoming still more like the down barbules of penguins. 
 
 3. Order CASUARIFORMES 
 PI. 14, Figs. 3, i 
 
 The birds of this group differ very considerably from the ratite 
 birds previously studied, but agree with them in the several important 
 characters common to all ratites. Although Nitzsch (1867) described 
 filoplumes from a cassowary, he was undoubtedly mistaken in his 
 identification of them (see Part I, p. 260), for filoplumes are as com- 
 pletely absent in this group as in any of the other Ratitae. Unlike 
 those of the ostriches and rheas, the primaries are greatly reduced, 
 hardly differentiated at all in Dromaeidae, and reduced to five or six 
 stiff black spines in Casuariidae, representing, according to Beebe 
 
■'■^^^^ Chandler: Structure of Feathers 291 
 
 (1904), only the hypertrophied calami, the scanty-vaned shaft being 
 first formed and then broken off at the superior umbilicus. No special- 
 ized reetrices are to be found. The aftershaft is enormously developed, 
 nearly or quite equalling the main feather plate, a condition found 
 elsewhere only in plumules and in the ear coverts of some birds. 
 
 The plumage of these birds differs widely from that of the 
 ostriches and rheas in being very hairlike and harsh to the touch, 
 a condition brought about by the looseness of the vanes, and the 
 stiffening of the rami, coincident with a reduction and loss of the 
 barbules. 
 
 a) Dromaeus novae-hollandiae 
 (1) Body Feathers 
 
 Body feathers characterized by great slenderness of form. Feather 
 plate extremely long relative to width ; total length in a typical back 
 feather of both shaft and aftershaft, about 20 to 25 cm.; width 
 approximately uniform for entire length, less than 1.5 cm. wide; 
 feather slightly rounded at tip. Aftershaft not appreciably different. 
 Shaft slender, slightly more so in aftershaft, with a broad, shallow, 
 ventral concavity. Rami typically of rather peculiar form, espe- 
 cially towards tip of feathers, where in many feathers the barbules 
 are more and more restricted to basal portion of barbs and 
 finally lost entirely. These naked terminal barbs set as close 
 together as are the middle, barbuliferous ones (about 8 or 9 per 
 centimeter), with rami very deep dorso-ventrally, and sword- 
 shaped, dorsal edge wide and smooth like the upper edge of a 
 sword blade, lower edge thin and sharp, tapering up to meet the 
 upper edge at tip (pi. 14, fig. 4a). Eami of more proximal barbs, 
 bearing barbules, similar but not so wide or so evidently sword- 
 shaped. 
 
 Barbules alike on inner and outer vanes, usually present to tips 
 of barbs on at least two-thirds of feather, and sometimes to tip 
 of feather; about 1 to 1.8 mm. long, very slender, and very numer- 
 ous, set about 30 to 35 per millimeter on both sides. Unlike those 
 of ostriches and rheas, barbules of typical downy type, with narrow, 
 flattened base, and long, filamentous pennulum (pi. 14, fig. 46). 
 Base short, of moderate width, pennulum almost absolutely thread- 
 like, the nodes very inconspicuously marked by minute prongs. All 
 barbules from either aftershaft or main feather plate, and from all 
 feathers examined, similar in form, differing only in size. 
 
 h) Other types. Casuariidae 
 
 Though very much like the emus in all the important characters 
 of their epiphyology, cassowaries differ in a few minor details. A 
 much larger proportion of each feather is composed of naked shaft 
 and rami, and the latter are widely separated from each other, not 
 
292 University of California Publications in Zoology [Vol. 13 
 
 forming compact, well-developed vanes, the result being that the 
 plumage of these birds is much coarser and more bristly than that 
 of emus. 
 
 The feathers have a somewhat different general shape. While 
 in emus they are elongate and narrow with approximately a uniform 
 width throughout, in cassowaries their widest point is a few centi- 
 meters above the umbilicus, thence more or less gradually tapering 
 to the tip. The aftershaft is as highly developed as in emus, and 
 as with the latter resembles the main feather plate in structure as 
 well as size. The calamus is exceedingly short, shorter in Casuarius 
 uniappendiculatus than in C. papuanus; in fact, it is so short in the 
 former that the division into shaft and aftershaft occurs under 
 the surface of the skin, the feather thus appearing completely 
 double. The barbs are moderately developed, not sword-shaped, 
 and spaced about 7 or 8 per centimeter, increasing to 16 per centi- 
 meter at the base; the barbules (pi. 14, figs. 3a, 36) are of about 
 the same length as in Dromaeus (1 to 1.8 mm.) but entirely lack 
 the prongs at the nodes, the latter being indistinguishable, and the 
 pennula simple threads. The naked terminal portion of the 
 feather, which sometimes constitutes three-fourths of the entire 
 feather, and reaches a length of over 20 cm., sometimes has the stiff, 
 bristle-like naked barbs present in decreasing numbers all the way to 
 the tip, where there are only two or three per centimeter on each side, 
 while in other cases, especially in shorter feathers, the naked shaft 
 is produced as a very coarse, stiff bristle. 
 
 c) Relationships 
 
 While agreeing with the ostriches and rheas in characters 
 common to all the Eatitae, the cassowaries and emus differ from 
 either of the former types far more than they differ from each other. 
 The present group, with the Apterygiformes, on the one hand forms 
 a subdivision of the Ratitae comparable with the Struthioniformes 
 and Rheiformes on the other, though the latter are more nearly 
 related to each other than are the former. The enormous after- 
 shaft, the few reduced remiges, the coarse texture of the plumage, 
 and the form of the barbules, are all striking points of difference 
 from the ostriches and rheas, while in all except the aftershaft 
 they agree more closely with the Apterygiformes in these characters. 
 Although in their feather structure there is no positive evidence 
 of their being primitively rather than secondarily flightless, there 
 
1916] Chandler: Structure of Feathers 293 
 
 is positive evidence favoring this theory in the ostriches and rheas, 
 as already shown, and the evident close relationship of the latter 
 birds to those of the present group is a strong argument in favor 
 of the Casuariiformes not having had flying ancestors. 
 
 d) Summary 
 
 The Casuariiformes have the following characters in addition 
 to those common to the ratites : 
 
 (1) Remiges greatly reduced, functionless in Dromaeidae, their 
 calami developed into a few stout spines in Casuariidae ; 
 
 (2) Texture of plumage coarse and hairlike, due to long, narrow 
 feathers which have more or less of terminal portion composed ot 
 a coarse shaft and rami with no barbules; 
 
 (3) Aftershaft similar to main feather plate in both size and 
 structure ; 
 
 (4) Barbules of downy type, practically invariable on different 
 parts of the body, the bases narrow and flattened, the pennula 
 long and filamentous, with prongs sometimes developed at the nodes 
 in Dromaeus, none whatever in Gasuarius. 
 
 4. Order APTERYGIPORMES 
 PI. 14, Fig. 5 
 
 This group, comprising several species of a single genus, is 
 probably the nearest to the carinate stem of all the ratite birds. 
 Their general epiphyological characters are as follows: (1) the 
 presence of small lateral apteria, as well as a ventral one (Parker 
 1891); (2) absence of differentiated plumules and filoplumes; (3) 
 remiges and rectrices rudimentary and functionless; (4) aftershaft 
 entirely absent; and (5) no pennaceous structure present. 
 
 The minute structure of the feathers comes nearer to the down 
 of the carinate birds than it does in any other ratite birds. No 
 specialized remiges are present and all the feathers are very similar. 
 
 a) Apteryx haasti 
 (1) Body Feathers 
 
 Shaft and calamus both slender, the former with no discernible 
 ventral groove, and tapering evenly for greater part of its length, 
 widening out a little terminally to produce a stiff, coarse tip. 
 
294 University of California Publications in Zoology [Vol. 13 
 
 Vanes tapering in both directions from about one-third of distance 
 from calamus to tip of feather. At widest point feather plate 
 about 3 cm. wide, total length seldom over 10 cm., thus giving 
 feather a much wider form than in case of Casuariiformes. Barbs 
 14 per centimeter on each side basally, only 9 or 10 towards tip of 
 feather, set at right angles to shaft on lower part of feather, the 
 angle gradually becoming more acute toward tip, so that even 
 though barbs are actually considerably longer, the vanes taper 
 evenly. Barbs on basal part of feather furnished with barbules 
 for whole length, but towards tip barbuliferous portion more and 
 more restricted to basal portion of barbs, the terminal parts of 
 which are elongated into moderately slender, black hairs lying 
 close to each other, and with totally different appearance from the 
 bare, coarse barbs of cassowaries and emus. Barbules very slender 
 and filamentous, of typical downy type. Base short, but well- 
 formed, about 0.017 mm. wide. Pennulum 0.008 mm. in diameter, 
 varying from perfectly smooth filament in basal barbs to filament 
 with distinct nodes and minute prongs in more terminal barbs 
 (pi. 14, figs. 5a, 5b). In well-developed downy region of vanes, 
 barbules from 2 to 3 mm. in length, set 25 to 35 per millimeter, 
 but in more terminal portion, where reduced, diminishing greatly 
 in length, but concomitantly stouter, with more distinct prongs. 
 
 Little variation in structure in different feathers. Around base 
 of bill a few long, hairlike rictal bristles developed, formed by 
 greatly elongated shafts of minute facial bristles. 
 
 b) Relationships 
 
 Apteryx apparently has a peculiar mingling of primitive, special- 
 ized, and degenerate characters, but, as hinted under Casuariiformes, 
 its feather structure suggests a rather closer affiliation to the Casuarii- 
 formes than to any other birds, and it seems best to regard the genus 
 as an early offshoot from the stem leading to the latter group. 
 
 The presence of vestigial (rudimentary?) apteria in these birds 
 has been considered by many authors as indicative of their descent 
 from a type possessing well-formed apteria, but it seems to me that 
 there is fully as much ground for looking upon this feature as a 
 beginning rather than a vestige. As in the case of other ratite 
 birds, the absence of differentiated plumules and filoplumes is much 
 more easily thought of as a primitive than as a degenerate char- 
 acter. The remiges and rectrices may have been better developed 
 in their ancestors, but there seems to be no positive ground for 
 believing that they ever possessed lifting power. The absence, of 
 the aftershaft may be a primitive or a secondarily acquired char- 
 acter. Its absence is the chief epiphyological divergence from the 
 Casuariiformes. 
 
^^^^^ Chandler: Structure of Feathers 295 
 
 c) Sxcmmary 
 
 In addition to the common ratite characters, Apterygiformes are 
 characterized by: 
 
 (1) The presence of small apteria; 
 
 (2) No specialized remiges or rectrices; 
 
 (3) No aftershaft; 
 
 (4) Feathers broad and tapering, outer part of barbs naked 
 towards tip of feather; 
 
 (5) Barbules of typical downy type, smooth and filamentous, 
 or with distinct nodes and prongs on pennulum, the base small but 
 well-formed. 
 
 5. SUMMARY OF RATITAE 
 
 Based on epiphyology the Ratitae are divisible into two main 
 groups, the Struthioniformes and Rheiformes on the one hand, the 
 Casuariiformes and Apterygiformes on the other. All of them 
 agree in the absence or rudimentary condition of the apteria, the 
 uselessness of the remiges for flight, the absence of differentiated 
 plumules and filoplumes, and the lack of any typical pennaceous 
 structure. 
 
 The first group seems to represent two branches of an early 
 offshoot from the stem leading to earinate birds, the type of feather 
 structure being at the end of a short path of evolution, the barbules in 
 both eases differing from either a pennaceous or downy type, but 
 apparently not leading to either. The aftershaft is absent in this 
 group. 
 
 The second group seems to represent two branches of another but 
 possibly later offshoot from the earinate stem, the barbules being of 
 typical downy type, and resembling, especially in Casuariiformes, 
 the down barbules of penguins and of the neossoptiles of many 
 •other forms of water birds. In the Casuariiformes the aftershaft 
 is equivalent t6 the main feather plate; in Apterygiformes it is 
 absent. In the latter group small lateral apteria are present, but 
 there is as much reason to believe them to be just developing as to 
 look upon them as vestigial. 
 
296 University of California Publications in Zoology [Voi,. 13 
 
 II. CARINATAE 
 
 All of the birds included in this group differ from those already 
 considered in the following important details: (1) the presence of 
 apteria in all but the Spenisciformes and Palamedeidae ; (2) the 
 presence, or undoubtedly secondary loss, of plumules and filo- 
 plumes; and (3) presence in the adult of both downy and pen- 
 naceous structures, while the nestling feathers are always downy. 
 
 1. Order SPHENISCIFORMES 
 
 Plate 15 
 
 The epiphyology of this group differs widely in a number of points 
 from that of all other living birds. With the sole exception of the 
 Palamedeidae, they are the only carinate birds with an absolutely 
 uniform distribution of feathers, the contour feathers and plumules 
 both being evenly distributed over the entire body. No specialized 
 remiges are developed and it seems probable that the first row of 
 feathers on the posterior margin of the wing is not homologous to the 
 remiges of other birds, but represents the under wing coverts, the 
 third row of feathers representing the true remiges ; this interpreta- 
 tion is based on the fact that in these birds there are no under wing 
 coverts with a reversed position (i. e., umbilicus exposed), as there 
 are in all other birds (Wray, 1887a). The rectrices are represented 
 by a row of feathers which have the shaft very stiff and spine-like, 
 with relatively short, stout, appressed barbs, and weak, reduced 
 barbules. 
 
 a) Aptenodytes pennanti 
 (1) Body Feathers 
 
 Details of feather structure very distinct from that of birds of 
 any other group. Calamus cylindrical and transparent, constricted 
 at superior umbilicus, where it gives off the shaft and an aftershaft. 
 The shaft of latter sub-triangular, about 0.1 mm. wide at junction 
 with calamus, widening out to about 0.4 mm. in the 2 mm. of its length, 
 then giving off a large number (50 or more) of very delicate, downy 
 barbs about 1.5 cm. long in feather about 4 cm. long. Down of after- 
 shaft like that of main feather plate, except barbules shorter. 
 
 Shaft remarkably broad and flat, in feather under consideration 
 about 2.5 mm. wide a short distance distal to superior umbilicus, con- 
 siderably under 1 mm. in depth, tapering gradually to tip ; very flat, 
 only slightly convex above and below, a slight median ridge on each 
 surface. Rami attached to narrow edge of shaft, thus not nearer 
 
1916] Chandler: Structure of Feathers 297 
 
 dorsal surface as in other birds. Barbs very numerous, about 30 or 
 40 per centimeter on each side, thus in some measure making up for 
 weakness of structure by strengthening vanes. More or less of inner 
 portion of barbs, usually about one-half, furnished with primitive 
 pennaeeous barbules; outer portion downy, compactness of vanes 
 being maintained only by stiffness of rami. Terminal portion of 
 feather devoid of barbules, rami becoming cylindrical and bristly. 
 Inner and outer vanes similar. Distal barbules of pennaeeous 
 portion (pi. 15, figs. 6a, 66) with poorly developed base. Pennulum 
 with a series of ventral barbicels extending to tip, not differentiated 
 into ventral teeth, booklets, and cilia. Usually all of them much 
 curved and hooklike, but not hooked merely at tip as in other 
 birds. Proximal barbules (pi. 15, figs. 6c, 6d) with no bend or 
 sharp differentiation between base and pennulum, the latter dis- 
 tinguishable only by presence of outward-curving, dorsal and ventral 
 barbicels, which hardly differ in form from prongs of down barbules, 
 though usually longer. Distal barbules reaching length of about 
 0.35 mm., the proximals about 0.6 mm., the base in each case 
 occupying about half total length. 
 
 2. Down 
 
 Transition from pennaeeous to down barbules simple and easy, 
 the hooked form of barbicels of distal barbules being lost and size 
 of those of proximal barbules reduced. Typical down barbules (pi. 15, 
 fig. 6e, and pi. 34, fig. 96) characterized by unusual shortness, hot 
 exceeding 0.8 mm. in length, and usually considerably less. Base 
 very narrow and poorly differentiated from pennulum. The latter 
 naked and filamentous basally, but furnished with comparatively 
 long and conspicuous prongs towards tip. As usual in typical 
 down, barbules inserted in four instead of two rows, those of either 
 side alternately projecting in different directions (pi. 15, fig. 6e). 
 Counting all four rows, there are about 60 barbules per millimeter. 
 
 b) Other Types 
 
 The dark feathers of Eudyptes chrysocome are very familiar, differ- 
 ing chiefly in having longer pennaeeous barbules (pi. 15, figs. 7a, 7b), 
 which have a dark pigment segregated into transverse bands, as in the 
 feathers of gulls and some pigeons. This probably accounts for the 
 bluish tinge which the feathers of this species have. In Spheniscus 
 mendiculatus the distal barbules are relatively short, while the proxi- 
 mals are long, with a well-developed series of ventral baricels; they 
 are about 0.25 mm. and 0.68 mm. long respectively. 
 
 The stiff, spinelike rectrices of the latter species have a broad, 
 shallow concavity on the ventral side of the shaft, although in the 
 body feathers the shaft is very thin and almost perfectly flat both 
 above and below. 
 
298 University of California Publications in Zoology [Vol. 13 
 
 c) Relationships 
 
 The Sphenisciformes must undoubtedly be considered the lowest 
 of living aquatic birds, although some of their apparently primitive 
 characters may be due to degeneration. The uniform distribution 
 of feathers, the absence of specialized remiges and of under wing 
 coverts with a reversed position, and the simple structure of both 
 their pennaceous and their downy barbules, all point to their 
 low systematic position. The broad, flattened form of the shaft, 
 and general scale-like appearance of the feathers on the other hand 
 are specialized characters. The most logical interpretation is to 
 look upon them as derivatives of the extinct, aquatic, toothed birds, 
 highly modified by specialization and degeneration for aquatic life. 
 
 d) Summary 
 
 The penguins have the following characters: (1) uniform dis- 
 tribution of both plumules and contour feathers; 
 
 (2) So far no filoplumes discovered; 
 
 (3) No specialized remiges, and no reversed under wing coverts; 
 
 (4) Aftershaft present, its shaft reduced, and the barbs spread- 
 ing out tuftlike; 
 
 (5) Main ^haft very broad and flat, usually with no ventral 
 groove ; 
 
 (6) Distal barbules very small with a weak base and a series 
 of hooked barbicels on pennulum, these barbicels not differentiated 
 into ventral teeth, booklets, and cilia; 
 
 (7) Proximal barbules small but longer than distals, no dis- 
 tinct bend or distinction between base and pennulum except the 
 presence of simple forward-curving ventral and sometimes also 
 dorsal barbicels; 
 
 (8) Down barbules relatively very short, with a poorly dif- 
 ferentiated base, and a filamentous pennulum furnished with well- 
 developed prongs, especially toward the tip, where they are always 
 larger. 
 
 2. Order COLYMBIFORMES 
 
 Plate 16 
 
 The loons and grebes, which comprise the present order, though 
 
 differing from each other in some details of structure, are very 
 
 similar as regards their epiphyology. Unlike any of the preceding 
 
 birds, they have well-developed apteria, and possess typical func- 
 
1916] Chandler: Structure of Feathers 299 
 
 tional remiges, although the birds are adapted for aquatic life. 
 They also possess typically developed pennaceous barbules. The 
 aftershaft is present with a short weak shaft, and numerous 
 spreading barbs. 
 
 a) Gavia immer 
 (1) Remex 
 
 Development very high, totally different from primitive condi- 
 tion in penguins. Shaft slightly broader than deep, distinctly 
 quadrangular, with narrow median groove on ventral side and 
 barbs attached nearer dorsal surface, as in all other flight birds. Rami 
 of both vanes, though narrow at junction with shaft, immediately 
 become very wide, with a broad, membranous ventral ridge, the 
 total width of ramus then equivalent to that of shaft, i. e., about 1.6 
 mm., the translucent ventral ridge constituting approximately one- 
 fourth the width of the ramus. Eami taper rapidly and become narrow. 
 Lower edge of ventral ridge almost if not quite smooth, no villi pro- 
 jecting ventrally. About 20 barbules per centimeter, usually a few 
 less on outer vane, a few more on inner. 
 
 Inner vane. — Distal barbules (pi. 16, fig. 8a) characterized by a 
 broad, well-formed base about 0.27 mm. long, narrowing proximal 
 to ventral teeth; latter 1 or 2, narrow and fingerlike; pennulum 
 moderately long; booklets 4 or 5, moderately long and slender, well- 
 formed; ventral cilia moderate, straight, more or less appressed to 
 shaft; basal two or three dorsal cilia stout and triangular, the 
 transition to rudimentary distal ones gradual. Total length of 
 barbule about 0.6 mm. Proximal barbules (pi. 16, fig. 8b) rather 
 stout, about 0.43 mm. long by 0.05 mm. wide, with about 4 long, 
 slender, conspicuous ventral teeth; pennulum filamentous, with 
 rudimentary barbicels. 
 
 Outer vane. — Distal barbules (pi. 16, fig. 8c) with elongated 
 base (0.33 mm. by 0.033 mm.) with 2 rather small ventral teeth. 
 Booklet region of pennulum very broad (pi. 16, fig. 8c, this barbulei 
 being twisted to show this characteristic). Hooklets considerably 
 increased in number, 6 or 7 present; ventral cilia very much as in 
 inner vane, and dorsal cilia absent entirely. Towards inner part of 
 barbs, bases of barbules much shorter and hooklets gradually chang- 
 ing over to curved ventral cilia, strongly hooked, reminiscent of 
 those in penguins. Proximal barbules of distal part of outer vane 
 (pi. 16, fig. 8d) with considerably narrower bases than those of inner 
 vane, and pennulum with a complete series of ventral cilia, the more 
 proximal ones strongly curved and hooked. The more basal proxi- 
 mal barbules very similar to those of inner vane, the ventral teeth 
 elongating on more distal barbules, ultimately forming the 4 or 5 
 proximal hooklike ventral barbicels, the more proximal cells of pen- 
 nulum adding more barbicels to these until a complete series is 
 
 formed. 
 
 (2) other Feathers 
 
 Back feathers with well-developed interlocking vanules basally. 
 Distal barbules with both base and pennulum elongated, the former 
 
300 University of California Puilications in Zoology [Vol. 13 
 
 with single, slender ventral tooth, the latter with 3 or 4 short hook- 
 lets, and a series of curved ventral barbicels. Type same as that 
 in Aechmophonis occidentalis (pi. 16, fig. 9e). Proximals with 
 slender, elongate base, and slender pennulnm, the latter with a 
 series of moderate ventral barbicels. See plate 16, figure 9/ (Aech- 
 mophorus occidentalis). On distal portion of feather, both distal 
 and proximal barbules reduced to single elongate type, resembling 
 somewhat proximal barbules of penguins; no sharp demarcation be- 
 tween base and pennulum, but latter with a series of curved ventral 
 barbicels; base, on some of terminal barbules, with one or two flex- 
 ules developed (pi. 16, fig. 9g, of Aechmophorus occidentalis), a 
 highly significant fact considering their universal occurrence in 
 Procellariiformes. 
 
 Breast feathers well-developed, with fairly strong vanes. Bar- 
 bules remarkably similar to those of penguins; distals (pi. 16, 
 fig. 8e) with narrow base and weak ventral teeth, pennulum with 
 long series of short booklets, gradually changing to curved ventral 
 cilia, exactly as in penguins ; proximal barbules towards tip of 
 barbs (pi. 16, fig. 8/) with slender tapering base and barbicelled 
 pennulum, the ventral cilia longer than dorsal, but both series 
 present. 
 
 i) Other Types 
 
 Gaviidae. — Gavia paciflca has practically identically the same 
 structure as the species above described. 
 
 Colymbidae. — In Aechmophorus occidentalis the structure of 
 the remiges is strikingly similar to that of Gavia, differing only in 
 a few details. The rami are not so deep and have not so wide a 
 ventral ridge as in the Gaviidae, and they are set closer on the 
 shaft, there being about 25 and 28 per millimeter on the inner and 
 outer vanes respectively. The barbules are essentially the same in 
 structure as in Gavia, but, as would be expected on smaller feath- 
 ers, they also are smaller; the distals (pi. 16, figs. 9a, 9c), for ex- 
 ample, are only about 0.47 mm. long, the base constituting about 
 half of this. On the proximaL barbules of the inner vane (pi. 16, 
 fig. 9b) the base is relatively longer and narrower, with less con- 
 spicuous ventral teeth, while in the proximals of the outer vane 
 (pi. 16, fig. 9d) the barbicels are much smaller and weaker. Colymbus 
 holioelli and Podilymhus podiceps are similar, but the barbicels of 
 the proximal barbules of the outer vane are still less conspicuously 
 developed, and confined to barbules on a less extensive portion of 
 the barb. 
 
 The back feathers of Aechmophorus occidentalis closely resemble 
 those of the loons. In most other grebes, however, e. g. the various 
 species of Colymbus and Podilymbus, a hairlike effect is produced in 
 
1916] Chandler: Structure of Feathers 301 
 
 the plumage by the wearing away of the barbules on the exposed 
 portions of the barb. 
 
 The breast feathers of the Colymbidae differ very considerably 
 from those of the Gaviidae. In Aechmophorus occidentalis the 
 breast feathers are exceedingly dense, inserted perpendicular to 
 the contour of the body, with the terminal portion sharply turned to 
 lie flat on the contour, this arrangement resulting in an unusually 
 dense plumage. The feathers are peculiar in having the barbs 
 set conspicuously wide apart on the shaft, about 13 per centimeter, 
 and set at rather a wide angle. The barbules are set about 20 per 
 millimeter on each side, and are about 0.75 millimeter in length. 
 They are of a very unusual type, flattened for about half their length 
 and then filamentous, the flattened portion being spirally twisted. 
 There is a further complication in that only every second, sometimes 
 every third, barbule reaches across to the neighboring barb, the 
 intervening ones being twisted so as to lie nearly parallel to the 
 barb and ventral to it (pi. 16, fig. 9h). On the outer portion 
 of the more distal barbs this peculiar structure is lost and the 
 barbules become elongate (over 1 mm.), slightly flattened, and 
 less twisted, and develop on their distal ends a double series of 
 barbicels, the ventral ones curved and hooklike, exactly similar to 
 the barbicels of the distal barbules in penguins. At the same time 
 the barbs and barbules become ribbed in such a way as to become 
 strongly reflective, and they give a shiny, silky appearance. The 
 result of this peculiar structure is a very much curved, loose, 
 open-vaned feather, which in the aggregate gives the thick silky 
 breast so characteristic of grebes. Various species of Colymius and 
 Podilymbus show precisely the same structure. 
 
 c) Down 
 
 The down of loons (Gaviidae) very closely resembles that of pen- 
 guins, being very short, usually under 0.5 mm., and with well-devel- 
 oped prongs, exactly as in penguins. In grebes the down is consid- 
 erably longer, often considerably over 1 mm. long, and frequently 
 with the prongs very slightly developed. 
 
 d) Relationships 
 
 As will be seen from the above descriptions, the feathers of 
 grebes and loons are very highly specialized and differentiated, and 
 
302 University of California Publications in Zoology [Vol. 13 
 
 show an almost perfectly intermediate position between penguins 
 on the one hand and Procellariiformes on the other. In the struc- 
 ture of the breast feathers and down, loons come much nearer the 
 Sphenisciformes than do grebes, and they are also more similar to 
 the Procellariiformes. The grebes appear to represent a separate 
 offshoot of the group, and have a condition of the breast feathers 
 which is different from that of any other birds except some of the 
 Alcidae. 
 
 e) Summary 
 
 Colymbiformes are characterized as follows: 
 
 (1) Aftershaft present, its shaft short, and barbs spreading; 
 
 (2) Distal barbules of inner vane of remiges with small, slender, 
 ventral teeth, moderate booklets and ventral cilia, and stout, tri- 
 angular, proximal dorsal eilia; 
 
 (3) Distals of outer vane with elongated base, the booklet region 
 of pennulum broad, and a considerable increase in number of booklets ; 
 
 (4) Proximal barbules with rather well-developed, slender ven- 
 tral teeth on inner vane and a series of hooked barbicels on outer; 
 
 (5) Breast feathers characterized by peculiar twisted barbules 
 in Colymbidae, but very reminiscent of Sphenisciformes in Gaviidae ; 
 
 (6) One or two flexules appearing on terminal barbules in 
 breast feathers; 
 
 (7) Down barbules short, strikingly similar to those of the 
 Sphenisciformes. 
 
 3. Order PROCELLARIIFORMES 
 
 Plate 17 
 
 The albatrosses, petrels, puffins, and other birds that comprise 
 this order form a very well-marked and easily recognizable group, 
 and it is not surprising to And that they possess a number of con- 
 stant epiphyologic characters. The plumules are evenly distributed 
 over the whole body, between the contour feathers and in the 
 apteria. The wing is very long in some species, due to the large 
 number of secondaries, these varying from 10 to 37 in different 
 species. The aftershaft is present, though sometimes very weak 
 and vestigial. "When well-developed, e. g., in Oceamodroma, its 
 shaft is short and the barbs spread out in a tuft as in the Colym- 
 biformes. In Diomedea it is very minute, while in Pelecanoides it 
 
1916] Chandler: Structure of Feathers 303 
 
 is over half the length of the main feather plate, with 30 or more 
 barbs in the breast feathers. 
 
 a) Diomedea exsulans 
 
 (1) Remex 
 
 Highly specialized as functional flight feather, the barbules in 
 fact possessing more "frills" than in any other feather known. 
 Shaft deeper than wide, especially on more proximal portion of 
 feather, with sharp, inconspicuous groove; calamus large and in- 
 flated. Vanes firm and elastic; barbs fairly close together, about 
 18 per centimeter on inner vane, somewhat less on outer, their rami 
 considerably deepened near junction with shaft, and barbules firmly 
 interlocking. Pith of barbs consisting of only a single layer of 
 hollow cells transversely, the ventral ridge not as broad and thin 
 as in loons, but constituting about a fourth of depth of barb. 
 
 Inner vane. — Distal barbules (pi. 17, fig. 10a) with a number 
 of rather striking characteristics. Twist between base and pennu- 
 lum unusually pronounced, making a very sharp curve in dorsal 
 contour of barbules as they lie undisturbed in vanule. Base large 
 and rather long, 0.45 mm. by 0.16 mm., differing from barbs of 
 birds of any other group, as far as known, by the presence of one 
 or two minute forward-projecting prongs on dorsal edge, on cells 
 bearing ventral teeth. Latter very peculiar in form, not simple 
 finger-like or lobate projections, but bifid at tip, and often trifid 
 (pi. 17, fig. 10a). Pennulum longer than base; booklets moderate 
 and well-formed; ventral cilia long, slender and flexible; the dorsal 
 cilia with much the same character as in Colymbiformes, i. e., short 
 and triangular basally, then becoming more slender, and finally de- 
 creasing, those beyond the sixth usually rudimentary or absent en- 
 tirely. Proximal barbules (pi. 17, fig. 10b) large and well formed; 
 base very long and relatively slender; about 0.76 mm. by 0.06 
 mm. with a well-developed flange, and rather small dorsal spines; 
 ventral teeth differing from those of all other birds in being slender, 
 flexible, and greatly elongated, sometimes 0.15 mm. long, and 
 usually with wavy appearance, as shown in figure. Pennulum ap- 
 proximately equal to base in length, broad at proximal end (about 
 0.01 mm.), tapering gradually to tip. Distal barbules set very 
 close together, about 30 per millimeter, proximals, being set at a 
 much more acute angle, much less numerous, about 17 per milli- 
 meter. 
 
 Outer vane. — Distal barbules (pi. 17, fig. 10c) differing from 
 those of inner vane in same manner as in loons, i. e., base slightly 
 more elongate, booklet region of pennulum broader, booklets more 
 numerous, ventral cilia longer and more filamentous, and dorsal 
 cilia undeveloped except terminally, but specific characteristics, 
 such as dorsal prongs and jagged ventral teeth, unchanged. Prox- 
 imal barbules (pi. 17, fig. lOd) with shorter and more tapering 
 base, and extremely long, heavy pennulum with a complete series 
 of ventral barbicels, the more proximal of which long and wavy. 
 
304 University of California Publications in Zoology [Vol. 13 
 
 the more distal ones shorter and not so delicate, often more or less 
 appressed to the shaft; towards tip dorsal cilia also developed. 
 Pennulum 1 mm. or more in length, 0.01 mm. wide. 
 
 (2) other Feathers 
 
 Secondaries differ from primaries in having pennula, especially 
 of distals, greatly increased in length, like the pennula of prox- 
 imals of outer vane of primaries. Back feathers, near base of barbs, 
 with distal barbules almost identically like those of inner vane of 
 remiges, but with pennula longer, and dorsal barbicels weaker. 
 Proximals, like those of outer vane of remiges, having very long, 
 heavy, barbicelled pennula towards tip of barb, but only 4 or 5 
 slender, wavy teeth on more basal part of barb. On distal portion 
 of barb, i. e., approximately distal third, flexules developed on 
 distal barbules, but transformation of barbules slight as compared 
 with breast feathers. 
 
 In ireast feathers proximal portion of barbs not materially dif- 
 fering in structure from that of back feathers, except that barbules 
 are weakened and the characteristic features less distinct. Terminal 
 portion of barb, however, entirely transformed. Distal barbules 
 (pi. 17, fig. lOe) with a series of flexules continuous with dorsal 
 pennular series of barbicels except in booklet region; base narrow, 
 and no marked bend between base and pennulum. As shown in 
 figure, all barbicels, even booklets, have tendency to bifurcate. 
 Proximal barbules also develop flexules, becoming similar in form 
 to that in Oceanodroma melania (pi. 17, fig. 126). 
 
 i) Other Types 
 
 In Pufftnus griseus the structure of the remiges is very similar 
 to that of Diomedea. All barbules, as shown in plate 17, figures 
 lla-c, though smaller, and with the characteristic features less 
 conspicuous, nevertheless differ in no essential points. The back 
 feathers of this species have the characteristic details of structure 
 still less distinct, the dorsal prongs and dorsal cilia of the distal 
 barbules, and the wavy form of the ventral teeth of the proximals, 
 being undeveloped. The breast feathers have the same structure 
 as in Diomedea. 
 
 Oceandroma melania has the minute structure of the remiges 
 very much like that of Puffinus, though the barbules, of course, 
 are smaller, the base being about 0.3 mm. long, (relatively very 
 large, except in this order) and with the same conspicuousness of 
 the twist at the junction of the base and pennulum, but the dorsal 
 prongs of the base are exceedingly minute or missing entirely. In 
 all other details, the structure is essentially the same as in Dio- 
 medea and Puffinus. 
 
 The back feathers of Oceanodroma melamia have a weak struc- 
 
^^1^] Chandler: Structure of Feathers 305 
 
 ture as compared to those of the species already described. The 
 distal barbules for the greater length of the barbs have well-formed 
 bases with no flexules, only two or three weak booklets, and no 
 dorsal cilia. The proximals, at the base of the feather, have only 
 two small, inconspicuous ventral teeth, but acquire four long and 
 slightly wavy ones farther distad on the barb. Near the tip of 
 the barbs the flexules are developed, beginning nearest the pen- 
 nulum instead of at the proximal end of the base, the latter be- 
 coming narrow and reduced, concomitant with the development of 
 the flexules. This is well shown in plate 17, figures 12a and 6. 
 
 In Pelecanoides urinatrix, belonging to the genus which may be 
 regarded as the least specialized member of the group, the breast 
 feathers have the barbules for the greater part of the barb weak, 
 but of ordinary type, i. e., without flexules. The bases of the 
 distals are narrow and elongate, the ventral tooth, usually single, 
 very small and simple, and the pennula hardly longer than the 
 base, slender, with usually only two weak booklets ; a series of 
 short ventral cilia similar to those of the body feathers of loons 
 (pi. 16, fig. 8e). The proximals do not possess the elongate, wavy 
 ventral teeth so characteristic of the more specialized members of 
 this order, but have these structures so small and inconspicuous 
 as hardly to be discernible at all. Near the tip of the barbs the 
 same sort of a change takes place that occurs in Oceanodroma, i. e., 
 a development of flexules with an accompanying reduction of the 
 base, the ventral cilia being still well developed. The similarity 
 of this type of barbule to those developed at the tip of the barbs 
 of the breast feathers of loons seems highly significant. This re- 
 semblance is strongly brought out by a comparison of plate 17, 
 figure 126, with plate 16, figure 8/, representing the barbules of 
 the tip of barbs of breast feathers of Oceanodroma and of Gavia 
 respectively. 
 
 c) Down 
 
 The down barbules in Diomedea and Puffinus (pi. 34, fig. 97) 
 are characterized by rather long, forward-curving prongs which are 
 slender and cilia-like in form, sometimes nearly 0.04 mm. long and 
 not infrequently forked. They are longest near the base of the 
 barbule, decreasing to rudimentary prongs toward the tip. The total 
 length of the barbules sometimes reaches 1 mm., but is usually some- 
 what less. 
 
306 University of California Publications in Zoology [Vol. 13 
 
 In Oceanodroma and Pelecanoides the barbules are slightly 
 shorter, usually 0.8 to 0.9 mm. long, and have very small prongs, 
 not noticeably larger near the base of the barbules than at the tip. 
 The black pigment in the case of Oceanodroma melania is evenly 
 distributed in the barbules, or almost so. 
 
 d) Relationships 
 
 The Procellariiformes, in the structure of their feathers, show 
 unmistakable resemblances to the Colymbiformes, especially the 
 loons, so much so that their close relationship can hardly be doubted. 
 They show, however, a considerably higher degree of development 
 than do the Colymbiformes, the barbules of both remiges and body 
 feathers possessing all the ordinary types of barbicels in highly 
 developed form, as well as some special structures of their own. 
 The bifurcated ventral teeth, dorsal prongs on the base in the 
 distal barbules of the remiges, and the elongated, delicate, wavy 
 ventral tee1?h of the proximals, are characters belonging solely to 
 Procellariiformes, or at least reach their highest development there. 
 The flexules of the body feathers also reach their highest develop- 
 ment in these birds. In view of these facts, we must look upon the 
 Procellariiformes, at least the more specialized ones, such as Dio- 
 medea, as representing the end of a path of evolution of their own, 
 while a more primitive procellariiform bird probably gave rise to 
 the Ciconiiformes through the Steganopodes (see page 315). 
 
 e) Summary 
 
 Procellariiformes may be characterized as follows: 
 
 (1) Plumules evenly distributed; 
 
 (2) Aftershaft present; 
 
 (3) Distal barbules of inner vane of remiges with minute dorsal 
 prongs on cells bearing ventral teeth (undeveloped in Pelecanoides), 
 the ventral teeth bifurcated or jagged, ventral cilia well developed, 
 slender and flexible, and the basal dorsal cilia triangular, gradually 
 becoming slender; 
 
 (4) Distals of outer vane of remiges differing in having more 
 slender base, booklet region of pennulum wider, booklets more nu- 
 merous, and basal dorsal cilia absent; 
 
 (5) Proximals of inner vane of remiges with very long slender 
 base, with elongated, delicate, wavy ventral teeth, and with pen- 
 nulum stout basally; 
 
1916] Chandler: Structure of Feathers 307 
 
 (6) Proximals of outer vane with tapering base, and very long, 
 heavy pennulum, with slender, wavy, or curved barbicels basally, 
 and usually both dorsal and ventral barbicels on greater part of 
 its tip ; 
 
 (7) Body feathers, especially on breast, with highly developed 
 flexules on both distal and proximal barbules; 
 
 (8) Down barbules of moderate length, either with rather long 
 prongs, longer near base of barbule (Diomedea and Puffinus), or 
 with an even series of moderately developed prongs {Oceanodroma 
 and Pelecanoides) . 
 
 4. Order CICONIIFORMES 
 
 Under this large group are included four suborders, and as all 
 the members of the group have little in common as regards their 
 feather structure, it will be more convenient to deal with each sub- 
 order separately. The suborders are as follows: (1) Steganopodes, 
 including all the water birds with fully webbed feet; (2) Ardeae, 
 including herons and bitterns; (3) Ciconiae, the storks and ibises; 
 and (4) Phoenicopteri, or flamingoes. 
 
 I. Suborder Steganopodes 
 Plates 18, 19 
 This suborder contains a rather heterogeneous assemblage of 
 water birds, which, although probably all with the possible excep- 
 tion of the Phaethontidae more closely related to each other than 
 to any other birds and therefore forming a natural group, are very 
 diverse, different members of it being probably near the line of 
 descent of various more specialized groups. In all of them the 
 plumules are evenly distributed over the entire body, and the after- 
 shaft is absent in most genera, but a minute one is present in 
 Fregata. 
 
 a) Phalacocorax penicillatus 
 (1) Remex 
 
 Remiges highly developed but not as much so as in Diomedea. 
 Shaft considerably broader than deep except at superior umbilicus, 
 with narrow ventral groove often nearly obsolete; no fine striations 
 on side of shaft as continuations of attachments of barbs, as 
 there are in most birds. Barbs set about 20 per centimeter, almost 
 equal on both vanes, very narrow, with only slight, translucent 
 ventral ridge. 
 
 Inner vane. — ^About 40 barbules per millimeter on distal vanule. 
 
308 University of California Publications in Zoology \Nol. 13 
 
 20 on proximal, the proximal barbules being set at a much more 
 acute angle with rami than are distals. Distal harhvles (pi. 18, 
 fig. 14a) moderate in size, the base being about 0.23 mm. long, 
 pennulum about 0.45 mm. Base narrowed only slightly proximal 
 to ventral teeth, and twist between base and pennulum not pro- 
 ducing sharp curve in dorsal contour. Ventral teeth lobate in form, 
 rather angular, and not smoothly rounded. Booklets usually 5 in 
 number, relatively short, but progressively becoming longer, their 
 broadened middle portion drawn out and flattened, often with a 
 tendency to give off a short prong. Ventral cilia long, curved, and 
 not very flexible. Proximal 2 or 3 dorsal cilia broad and lobate, 
 rather angular in shape, these followed by a few slenderer, spiny 
 ones, the more distal ones more and more rudimentary. Proximal 
 iarbules (pi. 18, fig. 14fe) with long, slender base about 0.6 mm. 
 by 0.04 mm. Ventral teeth 4 or 5 in number, long and pointed, 
 but not drawn out into wavy filaments as in Procellariif ormes ; 
 pennulum slender and filamentous, slightly shorter than base. 
 
 Outer vane. — Distal barbules (pi. 18, fig. 14c) differ from those 
 of inner vane in ordinary ways; shorter base, more numerous 
 booklets, and more proximal dorsal cilia undeveloped. Proximal 
 barbules (pi. 18, fig. lid) on basal portion of barbs resemble those 
 of inner vane, but on distal half, more or less, ventral teeth sep- 
 arate from one another, increasing in number, and develop into 
 hooked barbicels, which are shorter and have stouter hooks than 
 those of the Procellariif ormes (compare plate 18, figure 14d with 
 plate 17, figure lOd). 
 
 (2) other Feathers 
 
 In upper back feathers of females and young, distal barbules 
 nearer type of outer vane of remiges, with narrow elongate base, 
 two small, lobate ventral teeth, a long, broad pennulum with a 
 double series of cilia, dorsal ones best developed towards tip, but 
 never as well developed as the long, filamentous ventral ones. Pen- 
 nula of barbules near middle of barbs longest, giving brown velvety 
 effect to plumage (pi. 18, fig. 14e). Black edgings of feathers due 
 both to imperfections of development and to subsequent wearing 
 away of long pennula of distal barbules. Proximals with slender 
 tapering base, about 0.4 mm. long, and much elongated slender 
 pennula, about 0.8 mm. in length, with weak hooked cilia at bend, 
 followed by some scattered, simple, filamentous ones (pi. 18, fig. 14/). 
 Near base of barbs both proximal and distal barbules closely resemble 
 those of remiges. 
 
 Dark glossy green feathers of adult male have elongated, weak 
 barbules near base of barbs, the distals with an even series of short, 
 hooked ventral cilia, reminiscent of penguins and loons. Glossy 
 green portion produced by simple, rodlike barbules, slightly flat- 
 tened, and with refractory surface. 
 
 Breast feathers have outer part of barbs furnished with weak, 
 reduced barbules, entirely non-coherent, basal portion being well 
 developed; distal barbules with long, narrow base, reduced ventral 
 teeth, trapezoidal in shape, and elongate pennula, the latter with 
 3 or 4 short booklets, and a complete series of short, curved, ventral 
 
1916] Chandler: Structure of Feathers 309 
 
 cilia, subequal in size. On more distal portion of barbs, sharp 
 distinction between base and pennulum is lost, the barbules becom- 
 ing very narrow and simple, with a few weak, curved ventral cilia 
 near tip. Proximal barbules very much like those of back, but 
 more simple, and ori terminal portion of barbs assuming a form very 
 similar to distals opposite them, except that the ventral barbicels are 
 longer and more numerous. 
 
 b) Other Types 
 (1) Plotinae 
 
 Plotus, although grouped with the Phalacocoracidae, constituting 
 the subfamily Plotinae, differs from Phalacocorax so widely in its 
 feather structure that on this basis alone it should be entitled to 
 full family rank. The Steganopodes as a group are characterized 
 by the unusual difference in the different families as regards their 
 minute feather structure, but no two families of the order are more 
 distinct from each other than is Plotus from Phalacocorax. 
 
 Taking Plotus anhinga as a type, we find that the distal bar- 
 bules of the inner vanes of the remiges (pi. 18, fig. 13a) are remark- 
 ably reminiscent of those of the Cathartidae. The bases are elongate 
 and narrow, about 0.35 by 0.03 mm., while the pennula are about 
 0.45 mm. long. The twist between the base and pennulum is of 
 such a nature as to give the dorsal contour a peculiar, characteristic 
 wavy curve. When spread back between thumb and forefinger 
 both the base and the tip of the pennulum lie in a vertical plane, 
 only the moderately broad booklet area lying on its side, giving it 
 a hump-backed appearance. The ventral teeth are lobate, and pro- 
 ject straight forward in a direct line with the ventral edge of the 
 base. The booklets, usually five in number, are relatively short 
 and stout, but progressively increasing in length; the ventral cilia 
 are coarse, straight, and blunt, all but the proximal one or two 
 being closely appressed to the barbules. All of the dorsal barbules 
 are absent entirely, except the specialized one or two basal ones, 
 which have the form of stout, blunt, forward and laterally project- 
 ing spines. Immediately distal to them the dorsal contour of the 
 barbule curves evenly downward. The proximal barbules (pi. 18, 
 fig. 13&) are hardly less peculiar. In these the base is short and 
 stout, hardly longer than the base of the distals, and about 0.55 
 wide, with very short, triangular ventral teeth. The pennulum is 
 remarkably short and stout, being considerably shorter than the 
 abbreviated base, and 0.02 mm. wide, the cells of the ventral tooth 
 region and beyond having conspicuous, recurved dorsal spines, and 
 
310 University of California Publications in Zoology [Vol. 13 
 
 all of the cells clearly marked off by ridges. The barbules are set 
 fairly close together, the distals being about 30 and the proximals 
 18 per millimeter. 
 
 In the outer vane of the secondaries are to be found the most 
 unusual types of barbules in the whole avian class. The portion 
 of the vane which possesses a beautiful silvery grey color owes this 
 entirely to the pennula of the distal barbules (pi. 18, fig. 13c). The 
 bases are similar to those of the inner vane, but the pennula are 
 profoundly transformed into thick, clumsy, inflated, sacklike ex- 
 pansions, filled with opaque air bubbles which, when the barbules 
 are immersed in balsam, become infiltrated and rendered transparent, 
 leaving the round nuclei appearing like eyelike spots. There are 
 no dorsal cilia whatever, the booklets are only three or four in num- 
 ber, short and heavy, and the ventral cilia are produced into extremely 
 long, filamentous processes, lying closely appressed to each other, and 
 extending far beyond the tip of the expanded portion of the pennulum. 
 There are nine or ten short cells in the pennulum beyond the 
 booklet region, each with a long ventral barbicel, so that there is 
 a dense brush of these. The deep black pigment of these barbules 
 has a peculiar distribution, being dense in the base and in the 
 booklet cells and first two cilia cells of the pennulum, but absent 
 in the terminal part of the pennulum. Distal to the silvery area, 
 the pennula lose their inflated form and long cilia, then resembling 
 those of the inner vane, but with no dorsal spinelike cilia. The 
 proximals of the outer vane (pi. 18, fig. 13ci) are hardly distin- 
 guishable from those of the inner vane, except that the pennulum 
 is slightly shorter, and the recurved dorsal spines more prominent. 
 
 The back feathers of Plotus are modifications of the same type. 
 The proximals (pi. 18, fig. 13g) have a similar short, relatively 
 broad base, and the pennulum with recurved spines, but it is pro- 
 duced into a long, slender filament, and ultimately the whole bar- 
 bule is transformed into down on the more basal barbs. On the 
 more distal barbs the pennula become elongated and lose their 
 broad character, at the same time developing a few very weak and 
 minute ventral cilia, but the typical form of the whole barbule is 
 then soon lost and it becomes merely rodlike in form with a few 
 ventral barbicels. The distal barbules also ultimately assume this 
 form at the tip of the barbs. On the black portion of the feather 
 the distal barbules (pi. 18, fig. 13/) have long, slender bases with 
 small but typical ventral teeth, no hump on dorsal contour between 
 
1916] Chandler: Structure of Feathers 311 
 
 base and pennuluin, four very short, stout booklets, and a tapering 
 pennulum with a typical series of ventral cilia, but no dorsal ones. 
 On the silvery grey portion the barbules resemble those of the 
 similar portion of the secondaries, but are still more transformed. 
 The base is shortened and greatly reduced, and the pennulum is 
 enormously expanded and inflated (pi. 18, fig. 13e), with short re- 
 duced booklets, and greatly elongated filamentous ventral cilia ijdng 
 in a close, dense brush. The barbules of the back feathers are ex- 
 ceedingly dense, the distals being set 45 per millimeter, and the 
 proximals only about 18 per millimeter. 
 
 The breast feathers of Plotus anhinga are entirely downy, the 
 barbules being short on the terminal portion of the feather, but 
 long on the basal portion, where they are also very dense, there 
 being over 50 per millimeter on each side. 
 
 (2) Fregatidae 
 
 The Fregatidae, containing only the genus Fregata, have the 
 barbules of the remiges strikingly similar to those of Phalacocorax, 
 but differ in being of enormous size relative to the size of the 
 feathers (pi. 18, figs. 15a., 15&). Comparing these figures with figures 
 14a and 146 of the same plate, which represent barbules of a 
 feather of similar size in Phalacocorax, the difference is plainly 
 evident. The proximal barbules of the inner vane have a base 
 which is 0.9 mm. in length. In spite of their large size they are 
 set very close together, there being about 32 distals and 17 prox- 
 imals per millimeter. 
 
 The iridescent feathers of the back have the barbules completely 
 transformed for the production of color. The distal barbules of 
 the iridescent purplish and greenish-black feathers have short, in- 
 conspicuous bases, three or four small moderate booklets, and flat, 
 expanded pennula with constrictions between the cells. This method 
 of iridescent color production is exactly similar to that of ducks, 
 and the pennula are of precisely the same tjrpe as that in Anas 
 platyrhynchos (pi. 21, fig. 28i). In Fregata the proximal bar- 
 bules also share in the iridescent effect by means of the prominent 
 dorsal ridges between the cells bearing the ventral teeth, a condi- 
 tion frequently found in birds with dark iridescent feathers, e. g., 
 Geococcyx (pi. 30, fig. 73a). These proximal barbules of Fregata 
 have rather slender, tapering bases, and the ventral teeth tend to 
 become separated, to increase in number, and to develop as short. 
 
312 University of California Publications in Zoology C"^*"^- ^3 
 
 stout, ventral barbicels. The pennula of the proximals are flla- 
 mentous and take no part in the color production. 
 
 In the breast of Fregata the barbules are slender and elongated, 
 with all the barbicels small and weak, but with no specialized 
 characters. 
 
 (3) SuUdae 
 
 The Sulidae, containing the genus Sula, or gannets, are almost 
 identical with the cormorants and frigate birds in the minute struc- 
 ture of the remiges, except in the smaller size of the barbules, and 
 the slightly longer ventral teeth of the proximals of the inner vane 
 (pi. 19, figs. 16a, 166), and the better developed series of ventral 
 barbicels of those of the outer vane, those representing the ventral 
 teeth being short, broad, and blunt, followed by a series of per- 
 fectly formed, hooked cilia, broad at their origin, and tapering 
 with the curve, as in the proximals of the outer vane of Aechmo- 
 phorus (pi. 16, fig. 9d). 
 
 The back and breast feathers have barbules very similar to the 
 less specialized ones of Phalacocorax and Fregata. The distals 
 (pi. 19, fig. 16c) are elongate, with short, stout booklets and a full 
 series of curved ventral cilia, the dorsal ones being less conspicuous. 
 The proximals (pi. 19, fig. 16d) are also long and slender with a 
 series of weak ventral cilia. Towards the tips of the barbs flexules 
 are developed very much as in Phaethon. (See below, and plate 19, 
 figures 19e and 19/). 
 
 (4) Pelecanidae 
 
 The pelicans, Pelecanidae, with the single genus Pelecanus, while 
 possessing the same essential characters of the barbules as do the 
 cormorants, frigate birds, and gannets, differ in a number of details. 
 In the remiges of Peleca/nus erythrorhynchus the distal barbules 
 of the inner vane (pi. 19, fig. 17a) are conspicuously short and 
 stout. The base is over 0.06 mm. wide, and only about 0.25 mm. 
 long, whereas if it had the same relative length as in Phalacocorax 
 it would be about 0.37 mm. long. The ventral teeth are very 
 broad and lobate, the booklets, about six in number, are relatively 
 slender and progressively longer, followed by a series of long, 
 slender ventral cilia, which lie close together on account of the 
 shortness of the cells. The dorsal barbicels resemble those found 
 ill the more typical genera. In contrast to the distal barbicels, the 
 proximals (pi. 19, fig. 176) have exceedingly long and slender bases, 
 being almost 0.9 mm. long and only about 0.06 mm. wide in the 
 
1916] Chandler: Structure of Feathers 313 
 
 middle portion of the barbs. The pennula are short, not over half 
 the length of the bases. In no birds which I have examined is 
 there a greater difference between the length of the bases of distal 
 and proximal barbules on the same barb. To counterbalance this 
 great difference in size, in order to produce fairly equivalent 
 vanules, the angle of insertion of the distals is unusually wide, 
 while that of the proximals is unusually acute, this in turn result- 
 ing in an astonishing difference in number of barbules per unit of 
 measure. While there are 40 or more distals per millimeter, there 
 are only 16 or 17 proximals for the same distance. 
 
 On the outer vane the distal barbules differ from those of the 
 inner vane only in the absence of the dorsal cilia, and sometimes in 
 the presence of one more booklet. The proximals (pi. 19, fig. 17c), 
 except on a small portion of the tip of the barb, are similar 
 to those of the inner vane except that they are short, and rela- 
 tively broader. On the distal part of the barb the ventral teeth 
 increase to about six in number, become separated, and are trans- 
 formed into very long, stout, curved barbicels, resembling the teeth 
 of a large-toothed comb. The pennulum is shortened so that it 
 does not extend more than one cell beyond the barbicels; the base 
 is likewise shortened and reduced. 
 
 The primaries of Peleca/nus californicus are similair to those 
 described above. The secondaries and coverts, however, have the 
 distals transformed to produce the characteristic hoary effect. 
 These barbules (pi. 19, fig. 18a) have their bases reduced in size, 
 the booklets shortened, and the pennula elongated, with a double 
 series of long, slender cilia. They resemble very closely the distal 
 barbules of the hoary feathers of Phalacocorax (pi. 18, fig. He), 
 but the pennula are not so- broad, while the cilia are longer and 
 more prominent. 
 
 In the breast feathers of Pelecanus, at the base of the barbs 
 the barbules have a structure similar to that found in Sula and other 
 Steganopodes, a proximal barbule from this portion being shown 
 in plate 19, figure 17e. The outer portion of the barb, however, 
 develops typical flexules on both distal and proximal barbules, ex- 
 actly as in the Proeellariiformes. Plate 19, figure Yld, shows a 
 distal barbule from a breast feather of P- erythrorhynchus and 
 comparison with plate 17, figure lOe {Diomedea exsulans) will 
 show the striking similarity. At the extreme tip both barbules 
 assume the form shown in plate 19, figure 19e (Phaethon}, which 
 
314 University of California Publications in Zoology [Vol. 13 
 
 should be compared with plate 17, figures 12a and 126. Pelecwrvws 
 calif amicus has the same type of structure. 
 
 (5) PJiaetUontidae 
 
 The Phaethontidae or tropic birds, as far as feather structure 
 is concerned, seem to show a perfect transition from the Procel- 
 lariiformes on the one hand to the Laro-limicolae on the other, 
 though apparently more closely related to the latter. As shown by 
 plate 19, figure 19a (Phaethon rubricauda), the base of the distal 
 barbules of the inner vane is relatively large and broad, and the 
 ventral teeth long and slender, with a very slight tendency to 
 bifurcate, not always displayed, however. The booklets are only 
 four in number, and relatively short and small, the ventral cilia 
 are much reduced, and the dorsal ones likewise, except the basal 
 two, which are strongly reminiscent of Laro-limicolae. The prox- 
 imal barbules (pi. 19, fig. 196) differ from those of other Stegano- 
 podes, but agree with the Laro-limicolae in their relatively small 
 size, and in having small inconspicuous ventral teeth. There is 
 another significant difference in the relative number of distal and 
 proximal barbules. In all other Steganopodes there are nearly 
 twice as many distals as proximals, while in Phaethon there are 
 22 or 23 proximals to 30 distals, this genus thus resembling both 
 the Procellariiformes and the Laro-limicolae. The barbules of the 
 outer vane, the forms of which are shown in plate 19, figures 19c 
 and 19d, are characterized primarily by their slender form, the 
 wide separation of the booklets of the distal barbules, which are 
 all of nearly equal length, and the weak ventral cilia of the prox- 
 imal barbules. The rami of the outer vane have the ventral edge 
 serrate and broken into villi, a condition which reaches the height 
 of its development in the Anseres. 
 
 The barbules in back feathers of Phaethon rubricauda closely 
 resemble those of the inner vane of the remiges, except in their 
 smaller size. 
 
 The breast feathers, as in Pelecanus among Steganopodes, and 
 like the Procellariiformes and Laro-limicolae, develop flexules, but 
 not as numerous or as well-formed ones as in Pelecanus. Plate 
 19, figure 19e, shows a proximal barbule from the terminal por- 
 tion of a barb from a breast feather, while figure 19/ of the same 
 plate shows a distal barbule from a portion not quite so near the 
 tip. Its base is much reduced, and it has weak barbicels; a little 
 more distally it assumes a form similar to that represented in plate 
 
1916] Chandler: Structure of Feathers 315 
 
 19, fi^re 19e. Unfortunately these two figures were reversed in 
 position from the system usually followed in the preparation of 
 the plates. 
 
 c) Down 
 
 The down of Steganopodes, like the pennaeeous structure, is 
 extremely variable. In Phalacocorax, Fregata, Pelecanus and Pha'e- 
 thon the downy barbules are of moderate length, i. e., from 1.0 to 
 1.3 mm., and smoothly filamentous except in Pelecanus, which has 
 minute prongs at the nodes on the distal portion of the barbules. 
 In Plotus the downy barbules (pi. 34, fig. 99) are also filamentous, 
 but are very long, frequently reaching a length of over 2 mm. Sula 
 ■ differs not only from other Steganopodes but also from all other 
 birds in the enormous development of the prongs at the nodes. These 
 reach a length of over 0.1 mm. in barbules which are only 0.6 to 0.8 
 mm. long, being slender, filamentous, and frequently bifurcated 
 (pi. 34, fig. 98). The only other birds which begin to approach Sula 
 in the length of the prongs are albatrosses and puffins, and this might 
 be looked upon as additional evidence of fairly close relationship 
 between the Sulidae and the Procellariiformes. 
 
 d) Relationships 
 
 The Steganopodes are a group of birds in which primitive char- 
 acters are curiously combined with specialized characters, the result 
 being a rather heterogeneous aggregation of more or less related 
 forms which are specialized along different lines. They seem to 
 fall into three fairly well-defined groups as follows: (1) Phalaco- 
 corax, Fregata, Sula and Pelecanus; (2) Plotus; and (3) Pha'e- 
 thon. 
 
 The first group may be regarded as containing the most typical 
 Steganopodes, since they form the bulk of the group, and are 
 least specialized. They seem undoubtedly to be derived from a 
 primitive procellariiform type, and as certainly to stand at the 
 base of the ciconiiform group, the next above them being the 
 Ciconiae. 
 
 The second group, including only the neotropical genus Plotus, 
 though often grouped only as a sub-family of the Phalacocoraeidae, 
 differs very widely from the other Steganopodes in the structure 
 of its feathers, in which it is very specialized. In some details of 
 the feather morphology this genus shows such striking similarity 
 
316 University of California Publications in Zoology [Vol. 13 
 
 to the Cathartae that their kinship can hardly be doubted. This 
 will be forcibly shown by a comparison of plate 18, figures 13a and 
 136, with plate 22, figures 34 a and c. This close similarity of the 
 Cathartae with Plotus, accompanied as it is by other common char- 
 acters as shown by Gadow (1891), suggests the possibility of re- 
 garding the Cathartae as direct descendants of the Steganopodes, 
 from a form not far removed from Plotus. 
 
 The third group, Phaethontidae, is so strikingly like the Laridae 
 that their affiliation with the Steganopodes seems very doubtful, 
 and if feather morphology be considered, they should be looked 
 upon rather as aberrant larid forms. Comparison of plate 19, 
 figures 19 a-f, with plate 28, figures 61 a-e, will make clear the 
 marked similarity in feather morphology. 
 
 e) Summary 
 
 The Steganopodes are divisible into three groups on the basis 
 of feather morphology, the typical Steganopodes, Plotus, and 
 Phaethon. The first group is characterized as follows : 
 
 (1) Plumules uniformly distributed; 
 
 (2) After shaft absent or rudimentary; 
 
 (3) Distal barbules of remiges relatively small as compared 
 with proximals, and much more numerous, the difference in num- 
 bers much greater than usual; 
 
 (4) Distal barbules of remiges with short, broad base, with 
 broad lobate ventral teeth, except in Sula, where they are relatively 
 small and narrow; pennulum moderate in length, booklets slender 
 and progressively longer, ventral cilia long and slender, basal dorsal 
 cilia, on inner vane, stout and triangular, gradually changing to a 
 spiny, and ultimately a filamentous form; 
 
 (5) Proximal barbules of remiges with base long and large rela- 
 tive to distals; ventral teeth long and conspicuous on inner vane, 
 transformed into a weak series of Ventral cilia on outer vane; 
 pennulum rather broad, usually shorter than base, but sometimes 
 as long. 
 
 (6) Back feathers with bases of both distal and proximal barbules 
 elongate, the distals with long pennula, with double series of well- 
 developed slender cilia, except where specially modified for produc- 
 tion of iridescent color; booklets short; proximal barbules with 
 tendency to develop weak ventral cilia; 
 
1916] Chandler: Structure of Feathers 317 
 
 (7) Breast feathers similar but weaker, without flexules except on 
 outer part of barbs in Pelecanus and SuJ,a; 
 
 (8) Down barbules of moderate length, smoothly filamentous, 
 or with minute prongs at nodes on their distal portion except in Sula, 
 where prongs at nodes are enormously developed, to an extent 
 approached among other birds only in some Procellariiformes. 
 
 Plotus, constituting the second group, is characterized as fol- 
 lows: 
 
 (1) Proximal barbules very small relative to distals, the length 
 of their bases actually less. 
 
 (2) Distal barbules of inner vane of remiges with ventral teeth 
 lobate, their ventral edge in a continuous line with ventral edge of 
 base; booklets relatively small and very stout, progressively longer; 
 ventral cilia coarse, blunt, and rodlike, more or less appressed to 
 pennulum; no dorsal cilia except one, or sometimes two, stout, 
 blunt, spinelike basal ones, followed by a dip in the dorsal contour 
 of the barbule, thus giving it a characteristic shape. 
 
 (3) Proximals of both vanes of remiges with very short, small 
 base, inconspicuous ventral teeth, and short, conspicuously wide 
 pennulum, with recurved spines. 
 
 (4) Silvery gray color of parts of outer vane due to a greatly 
 expanded and inflated unpigmented pennulum bearing small, stout 
 booklets and extrem^ely long, slender, closely associated ventral cilia. 
 
 (5) Body feathers with distals and proximals both similar to 
 remex type, of which they are mere simplifications; no fiexules 
 developed. 
 
 (6) Down barbules smooth and filamentous, and longer than 
 in any other Steganopodes, frequently over 2 mm. 
 
 The third group, including only the monogeneric Phaethontidae, 
 is characterized as follows: 
 
 (1) Distal barbules of remiges large as compared with proxi- 
 mals, and the latter over two-thirds as numerous. 
 
 (2) Twist between base and pennulum of distals producing 
 sharp curve in the dorsal contour as barbule lies in normal posi- 
 tion; ventral teeth small and slender; booklets slender, rather weak, 
 and well separated from each other ; ventral cilia reduced ; and basal 
 dorsal cilia of inner vane lobate, almost exactly as in gulls. 
 
 (3) Proximal barbules of remiges with narrow base, short pen- 
 nulum and short inconspicuous ventral teeth on inner vane, a series 
 of weak ventral cilia on outer vane. 
 
318 University of California Publications in Zoology [Vol. 13 
 
 (4) Breast feathers with flexules developed on terminal por- 
 tion of barbs of breast feathers. 
 
 (5) Down smooth and filamentous, little if any over 1 mm. long. 
 
 II. Suborder Ciconiae 
 PL 20, Figs. 23-27. 
 Constituting the second suborder of the Ciconiiformes are the 
 storks and ibises, which, together with the Ardeae, form a compact 
 and well-defined group. Although the. typical Ardeae are readily 
 distinguishable from typical Ciconiae, there are a number of more 
 or less intermediate forms which make their characterization by 
 other characters as well as by epiphyology very difficult. Ex- 
 cluding Balaeniceps and Scopus, which combine characters of both 
 groups, the Ciconiae are distinguished from the Ardeae by the fol- 
 lowing characteristics: (1) absence of powder down, (2) even 
 distribution of plumules in both pterylae and apteria, and (3) 
 feathered lores. The aftershaft is very variable, being present, 
 rudimentary, or absent in different genera. 
 
 a) Mycteria americana 
 
 (1) Remex 
 
 Shaft stout and square, about as deep as wide, with broad, V- 
 shaped ventral groove, and fine striations on sides where barbules 
 are attached. Band not greatly deepened at junction with shaft 
 but deeper than usual in Steganopodes. Pith cells more than a 
 single layer thick, and ventral edge of rami of both outer and inner 
 vanes without villi. Distal vanule with barbules greatly outnum- 
 bering those of proximal vanule, the barbules about 40 per milli- 
 meter on former, only 18 per millimeter on latter, this difference ac- 
 companied by great difference of angle of insertion of barbules on 
 ramus. 
 
 Inner vane. — Distal hariules (pi. 20, fig. 23ft) small relative to 
 proximals; base of moderate size, about 0.35 by 0.05 mm., with 
 fairly large, lobate ventral teeth, frequently blunt and slightly 
 incised at tip; pennulum characterized by stout heavy form; 
 booklets numerous, 6 or 7 in number, moderately stout, and pro- 
 gressively increasing a great deal in length; ventral cilia rather 
 poorly developed, present all the way to tip of pennulum, straight, 
 and appressed to barbule; basal dorsal cilia stout, blunt, and spine- 
 like, well separated from each other, the first one always the largest; 
 usually three such stout barbicels developed, the following ones 
 becoming more and more like the ventral ones. Proximal barbules 
 (pi. 20, fig. 23b) with very large bases, about 0.7 mm', long by 0.07 
 mm. wide with a series of broad, triangular ventral teeth projecting 
 very little beyond the ventral contour of barbule ; pennulum re- 
 
1^^6] Chandler: Structure of Feathers 319 
 
 markably short, about half length of base, very broad proximally, 
 and tapering rapidly to tip; pigment deeper ventral to nuclei than 
 dorsal to them, reverse being more frequently true in other birds. 
 
 Outer vane. — Distal barbules differ only in absence of dorsal 
 cilia, except a few terminal rudimentary ones (pi. 20, fig. 23c). 
 Proximals, unlike those of any birds so far studied except peli- 
 cans, differ only slightly from those of inner vane, being somewhat 
 smaller, their form exactly similar except that ventral teeth are 
 slightly longer, with tendency to become hooklike, but even at tip 
 of barbs not increasing in numbers and forming a series of ventral 
 barbicels. 
 
 (2) other Feathers 
 
 Back feathers have same structure as outer vane of remiges 
 except that small dorsal cilia are sometimes developed on distal 
 barbules near the base of more proximal barbs. In breast feathers 
 structure not essentially different. Distals (pi. 20, fig. 23dt) more 
 elongate, and dorsal cilia, except at proximal end of pennulum, 
 better developed. Proximal barbules of exactly same type as in 
 remiges, in neither distal nor proximal barbules any tendency what- 
 ever for development of fiexules. 
 
 b) Other Types 
 
 Ciconia ciconia has a very similar structure of its feathers. 
 The chief difference is in the relative narrowness of the proximal 
 barbules. 
 
 Leptoptilus dubius has a slight modification of the structure of 
 distal barbules as compared with those of Mycteria. The first two 
 dorsal barbicels of distal barbules of the inner vane (pi. 20, fig. 24a) 
 are stout and spinelike as usual, but are very much closer together 
 and are not followed by a series of less specialized cilia, thus approach- 
 ing more closely to the heron type. On the outer vane the pennulum 
 of distal barbules is relatively short and furnished with an even series 
 of short blunt dorsal cilia (pi. 20, fig. 24&). The under tail cov- 
 erts of Leptoptilus deserve special mention as they are the source 
 of the famous "marabou" feathers of commerce. These feathers 
 are furnished with stiff, heavy shafts, but have the entire feather 
 downy in structure, a condition seldom found in contour feathers, 
 except occasionally on a very weakly developed breast or belly 
 feather. 
 
 In Plegadis guarauna, or scarlet ibis, there is a very striking 
 modification in the distal barbules to deepen the scarlet color-effect 
 (pi. 20, fig. 26a). As will be seen from this figure, both base and 
 pennulum are profoundly transformed, and all the barbicels except 
 the booklets are lost or greatly changed. Both base and pennulum 
 
320 University of California Publications in Zoology [Vol. 13 
 
 are characterized by a series of transverse rings which evidently 
 have a tendency to break up the light and deepen the red color 
 produced by the diffused pigment. The proximal barbules remain 
 practically unchanged. 
 
 Ajaja ajaja, representing the Plataleidae or spoonbills, resembles 
 Plegadis very closely. Both Plegadis and Ajaja have the ventral edge 
 of the rami serrate. The similarity of the barbules of the back 
 feathers to similar ones of Mycteria is shown by plate 20, figure 27a, 
 as compared with plate 20, figure 23c. 
 
 c) Down 
 
 The down barbules of Mycteria americana and of other 
 Ciconiidae are long, frequently over 2.5 mm., and are very slender 
 and filamentous, with minute inconspicuous prongs, or none what- 
 over, at the nodes. In the Ibididae and Plataleidae, on the other 
 hand, the down barbules are rather short, usually under 1 mm. in 
 length, and very stout and coarse, the internodes with longitudinal 
 ridges and grooves, and the nodes with well-developed prongs. A 
 down barbule of Guara rubra is shown on plate 23, figure 101. 
 
 d) Relationships 
 
 The Ciconiae form the middle section of the Ciconiiformes, the 
 Steganopodes being below them and the Ardeae and Phoenicopteri 
 above. Undoubtedly their closest relatives are the herons, with 
 which they are joined by such intermediate forms as Balaeniceps 
 and Scopus, the feathers of which I have been unable to obtain for 
 study. The Phoenicopteri appear to connect the Ciconiae with the 
 Anseres. No relation whatever is shown by the structure of the 
 feathers to the Limicolae or to typical Gruiformes. 
 
 e) Summary 
 
 The Ciconiae are characterized as follows: 
 
 (1) Barbules much more numerous on distal than on proximal 
 vanule. 
 
 2. Distal barbules with base of moderate size relative to prox- 
 imals, with moderate, lobate ventral teeth ; pennulum stout and heavy, 
 with 6 or 7 moderate-sized, progressively longer booklets; ventral 
 cilia more or less appressed, straight, usually blunt ; on the inner vane 
 about three well-separated, stout, basal dorsal cilia, followed by less 
 
1916] Chandler: Structure of Feathers 321 
 
 specialized ones, except in Leptoptilus, where there are only 2, and 
 these close together. 
 
 (3) Proximal barbules with large bases, inconspicuous ventral 
 teeth, a short but broad and tapering pennulum, and no ventral 
 cilia developed on outer vane. 
 
 (4) Ventral edge of outer rami of primaries serrate in Ibididae 
 and Plataleidae, but smooth in Ciconiidae. 
 
 (5) Body feathers with barbules as in remiges, but more elongate 
 and slender; never any flexules. 
 
 (6) Down barbules in Ciconiidae long, slender, and filamentous, 
 with small inconspicuous prongs or none at all; in Ibididae short, 
 stout and heavy, longitudinally ribbed, and with well-developed 
 prongs at the nodes. 
 
 III. Suborder Ardeae 
 PI. 20, Figs. 20-22 
 
 As stated above, the typical Ardeae are readily distinguishable 
 from the Ciconiae, but Balaeniceps and Scopus combine the char- 
 acters ' of both groups in such a way that the characterization of 
 either is very difficult without allowing for these exceptions. 
 Unfortunately I have not been able to obtain feathers of either of 
 these genera for study, in order to find out whether their feather 
 structure adheres to the typical ardean type or approaches that of 
 the Ciconiae. Having no data concerning either of these two out- 
 lying forms, nor of Cochlearius, the present section deals only with 
 the Ardeidae, including the herons, egrets and bitterns. Their 
 general epiphyological characteristics are as follows: (1) plumules 
 confined to the apteria, (2) powder down present, (3) aftershaft 
 present, and (4) lores naked. 
 
 a) Ardea herodias 
 
 (1) Bemex 
 
 Shaft and rami very similar to those of Ciconiae, the shaft, if 
 anything, slightly deeper than wide, with V-shaped ventral groove, 
 and fine striations on side. Rami not considerably deepened, even on 
 outer vane, the pith not more than a single layer in thickness and 
 the ventral edge not serrate or furnished with villi. Distal vanule 
 with about 30 barbules per millimeter, proximal vanule with about 
 18 per millimeter. 
 
 Inner vane. — Distal barbules (pi. 20, fig. 20a) with small base, 
 about 0.26 by 0.04 mm. with relatively very large, leaf-like ventral 
 teeth so shaped and arranged as to form a single, large, blunt, 
 
322 University of California Publications in Zoology ["V^o^- ^3 
 
 subtriangular lobe; pennulum with very characteristic form, differ- 
 ing considerably from those of Ciconiae, though approached in 
 Leptoptilus; hooklets similar to those of Ciconiae, but normally 
 only 5 in number, followed by 3 or 4 steadily diminishing ventral 
 cilia, beyond which the pennulum is greatly elongated, rather 
 slender, and totally unbarbicelled ; 2 basal dorsal cilia developed 
 as characteristic stout spines very closely approximated to each 
 other, third dorsal cilium a short spine, and all the rest unde- 
 veloped. Proximal iarhules (pi. 20, fig. 20&) with base of moderate 
 size, about 0.5 by 0.05 mm., with short, inconspicuous ventral 
 teeth; pennulum only a little shorter than base, slightly flattened 
 proximally, but soon tapering to a very fine slender filamentous tip. 
 
 Outer vane. — Distal iarhules (pi. 20, fig. 20c) with pennulum 
 somewhat shorter and stouter than in inner vane, usually 6 hooklets, 
 no dorsal cilia, and a large number of short, blunt ventral cilia. 
 Proxirnal barbules (pi. 20, fig. 20d) differ from those of inner 
 vane only in having a somewhat shorter pennulum; no ventral cilia 
 ever developed. 
 
 (2) other Feathers 
 
 Inner scapular feathers with distal barbules (pi. 20, fig. 20e) 
 somewhat like those of distals of outer vane of remiges, but both 
 base and pennulum more elongated, pennulum also stouter, more 
 like ciconiid type, with short, broad, and very blunt ventral cilia 
 somewhat resembling ventral teeth; pigment irregularly distributed, 
 being dense in base, but very light or absent in pennulum. 
 Proximal barbules of scapulars (pi. 20, fig. 20/) differ from those of 
 outer vane of remiges only in more elongate and relatively slender 
 form. Blunt ventral cilia of distals of outer vane slightly more 
 numerous and better developed, otherwise vanes alike. Elongated 
 tips of these feathers produced by an elongation of the slender shaft 
 accompanied by a number of greatly elongated barbs lying so closely 
 appressed, and attached to shaft at such long intervals, as to lie paral- 
 lel with shaft. These elongated barbs are furnished with distal and 
 proximal barbules only slightly reduced, so that they interlock fairlj' 
 well. On account of change in angle of insertion of more distal barbs, 
 there is too much strain for perfect vane to be maintained, result being 
 a breaking up into elongated groups of barbs, which is very charac- 
 teristic of these feathers. 
 
 On breast feathers also with elongated, ornamental tips, basal 
 portion of feathers has much simplified barbules, and barbs very- 
 loose if at all held together. Barbs of ornamental tip better 
 developed with less simplified barbules, the latter resembling those 
 of scapular and back feathers, being short, with well-developed 
 functional hooklets. As in back feathers, barbs inserted at wide 
 intervals, and .closely appressed to one another so as to form a 
 very narrow, compact tip. 
 
 b) Other Types 
 
 Nycticorax nycticorax differs from Ardea herodias in the struc- 
 ture of its remiges only in the slightly better developed third dorsal 
 
1918] Chandler: Structure of Feathers 323 
 
 eilium, and presence of a rudimentary fourth one. The dark green 
 feathers of the back are somewhat modified. The bases of both 
 distal and proximal barbules of these feathers are long and nar- 
 row, and deeply pigmented, while the ventral teeth in both are 
 poorly formed and lightly pigmented. The booklets of the distals 
 are weak and reduced, the ventral cilia are short and blunt, and 
 there are no dorsal cilia. The proximals have three or four 
 progressively diminishing blunt ventral cilia on the pennulum, thus 
 greatly resembling in general form the distal barbules. 
 
 Botaurus and Butorides very closely resemble Ardea in all the 
 details of their feather structure. The distal and proximal barbules 
 of the outer vane of Butorides virescens are shown in plate 20, 
 figures 21a and 21&, and comparison with figures 20a and 20& of the 
 same plate will show the similarity. The slight separation and for- 
 ward curve of the ventral teeth of the proximals of the distal part 
 of the outer vane, as shown in plate 20, figure 21& and slightly 
 less prominently in plate 20, figure 20d, are very characteristic of 
 the entire family. 
 
 The most interesting birds of the entire group from a popular 
 point of view are the egrets, Egretta candidissima and Herodias 
 egretta, from which are derived the famous "aigrettes" of com- 
 merce. In the structure of its remiges Herodias egretta differs 
 from the typical forms of the genus Ardea in the reduction of the 
 dorsal cilia. The first one is fairly well developed, the second smaller, 
 and the third very minute. They thus differ from Ardea herodias in 
 the opposite direction from Nycticorax, which has the dorsal cilia a 
 little better developed. 
 
 The aigrettes of both species of egrets are too well-known to 
 need a general description, the barbs being very widely separated 
 on the shaft, reaching a length of 15 cm. or more, and appearing as 
 filamentous strands entirely separate from each other. Although to 
 the naked eye the barbs appear destitute of barbules, closer examina- 
 tion shows that there is a complete series of closely appressed, 
 non-interlocking barbules, the distal and proximal ones very similar, 
 except that the latter are a little longer. They are flat and taper- 
 ing, with no well-developed barbicels, as shown in plate 20, figure 22. 
 The distal and proximal barbules are spaced 21 and 18 per milli- 
 meter respectively. The barbules of the aigrettes of Herodias egretta 
 differ from those of Egretta candidissima in the length, the former 
 being under 0.65 mm. long while the latter are normally at least 0.7 
 
324 University of California Publications in Zoology [Vol. 13 
 
 mm. and usually a little over 0.8 mm. In the ai^ette-like feathers of 
 Bubuleus His of Europe there are only 11 proximal barbules and 
 14 distals per millimeter, and they never exceed about 0.57 mm. 
 in length. These barbieels are even more rudimentary than in the 
 true American egrets. 
 
 Eurypyga (see p. 352, and pi. 27, figs. 55a-d) and possibly 
 Cariama (p. 352, and pi. 27, figs. 56a and b) are probably nearly 
 related to the Ardeae. Cursorius, family Glareolidae (p. 356, and 
 pi. 28, figs. 60a-c), also appears to be most nearly related to the 
 Ardeae. 
 
 c) Down 
 
 The down barbules in Ardea are long, reaching a length of 2 mm. 
 or more, being filamentous and very slender, with slightly enlarged 
 nodes, and pigment uniformly, or almost uniformly, distributed. 
 Minute prongs present at nodes on more distal portion of barbules. 
 In Botaurus, in which the down is dark gray, the pigment is 
 absent only at the nodes (pi. 34, fig. 100). 
 
 d) Relationships 
 
 The Ardeae, or at least the Ardeidae, seem to form an end 
 branch from a ciconiid stem, being considerably more specialized 
 than the Ciconiae, and apparently not giving rise to any other 
 orders or suborders. Eurypyga, and to a less extent, Cariama, both 
 ordinarily classed in the Gruiformes, have a feather structure which 
 is so heron-like that the possibility of their inclusion in the Ardeae 
 is strongly suggested. Cursorius likewise has a structure which 
 strongly argues for its inclusion in this group. 
 
 e) Summary 
 
 The typical Ardeae have the following epiphyological characters: 
 
 (1) Plumules confined to apteria. 
 
 (2) Aftershaft present. 
 
 (3) Powder down present. 
 
 (4) Lores naked. 
 
 (5) Distal barbules nearly twice as numerous as proximals. 
 
 (6) Distal barbules of remiges with small base, with large, 
 leaflike ventral teeth, so shaped and arranged as to form a large 
 blunt triangle; booklets usually 5, only 3 or 4 progressively dimin- 
 
1916] Chcmdler: Structure of Feathers 325 
 
 ishing ventral cilia developed, and on inner vane two closely 
 approximated, blunt, stout, dorsal cilia followed by one or two 
 spinelike ones, the rest of the pennulum elongated, slender, and 
 without barbicels. 
 
 (7) Proximal barbules of inner vane with moderately large 
 base, short inconspicuous ventral teeth, and pennulum very slender 
 and threadlike, shorter than base. 
 
 (8) Proximals of outer vane similar to those of inner vane, 
 never developing ventral cilia. 
 
 (9) Body feathers with pennulum of distals usually rather 
 stout, dorsal cilia not developed, the ventral ones conspicuously 
 short and blunt. 
 
 (10) Ornamental plumes with divided vanes frequently de- 
 veloped. 
 
 (11) Down very long, often over 2 mm., the nodes slightly 
 enlarged, sometimes with minute prongs, pigment when present not 
 collected into conspicuous spots. 
 
 IV. SUBOKDER PhOENICOPTEKI 
 
 PI. 21, Fig. 32 
 
 The flamingoes, in Knowlton's classification, are grouped as a 
 suborder of the Ciconiiformes, but in their characters they are so 
 perfectly transitional between the Ciconiae, especially the ibises, on 
 the one hand, and the Anseriformes on the other, that, while 
 evidently forming a suborder of their own, the question as to 
 the group with which they are more closely associated has been 
 one of the most debated questions in the classification of birds. 
 Their feather structure, therefore, is of unusual interest, on account 
 of the light which it throws on this relationship. 
 
 As in both the Ciconiae and the Anseriformes, the down is 
 here also uniformly distributed. The aftershaft is present, which is 
 an interesting fact considering that in the Ciconiae it is very 
 variable, while in the Anseriformes it is rudimentary or absent. 
 There are twelve primaries as in some Ciconiae, whereas in 
 Anseriformes there are only eleven. 
 
 a) Phoenicopterus ruber 
 
 (1) Remex 
 
 Shaft of remiges slightly wider than deep, with shallow median 
 groove. Pith of rami more than one cell in thickness ; whole ventral 
 
326 University of California Publications in Zoology [Vol. 13 
 
 ridge narrow, and without villi on the ventral edge on outer vane. 
 Distal barbules small relative to the proximals, and outnumbering 
 them about two to one; on inner vane of secondary about 40 distals 
 to 20 proximal barbules per millimeter. 
 
 Inner vane. — Distal barbules (pi. 21, fig. 32a) with very short 
 base, about 0.2 mm. long by about 0.04 mm. wide; ventral teeth 
 slender and elongate, much more so than in Ciconiae, but less so 
 than in Anseres; the pennulum relatively short, seldom over 0.3 
 mm., making, with the base, a short barbule; booklets 5, slender, 
 of moderate length, but progressively longer; ventral cilia long and 
 slender, and not conspicuously curved; dorsal cilia, as a series, 
 well developed, the basal 2 or 3, stout and spiny, the more distal 
 ones more slender. Proximal barbules with base about 0.5 mm. 
 long by 0.055 mm. wide, with a series of about 4 ventral teeth, 
 the proximal two larger and more lobate, the outer ones more 
 slender and pointed. 
 
 Outer vane. — Distal barbules differ mainly in the larger number 
 of booklets, and more conspicuous ventral cilia, and absence of 
 dorsal ones, while in proximals (pi. 21, fig. 32b) the ventral teeth, 
 especially distal ones, become separated from each other, increase 
 in number, and form a series of straight, sharp, ventral barbicels, 
 exactly comparable to those in the outer vane of ducks, as will be 
 seen by comparing plate 21, figure 32b, with plate 21, figure 28/. 
 
 (2) other Feathers. 
 In body feathers barbules merely a simplification of remex type, 
 proximals retaining a series of slender, ventral barbicels, as shown in 
 plate 21, figure 32c, which represents a proximal barbule from loose- 
 vaned scapular feather; no flexules ever developed. 
 
 (3) Down 
 Down barbules (pi. 35, fig. 102) long and filamentous, with 
 inconspicuous nodes except near tip of pennula, where they are 
 slightly enlarged, and possess small prongs. 
 
 b) Relationships and Summary 
 
 In all of the above details of the minute structure of the feathers 
 the Phoenicopteri agree with the Anseres more closely than with the 
 Ciconiae. 
 
 In all of the following points they agree with the Anseres . as 
 opposed to the Ciconiae: (1) general shape and relative size of 
 barbules; (2) form of ventral teeth of both distals and proximals; 
 (3) form of both ventral and dorsal cilia of distals; (4) presence 
 and form of ventral barbicels of outer proximals. 
 
 The chief points of difference are: (1) the smaller number of 
 booklets; (2) the smooth ventral edge of rami of outer vane; (3) 
 form of down. In the first two of these characters they also differ 
 from the Ibididae, with which they are more closely related than 
 
1916] Chandler: Structure of Feathers 327 
 
 with any other Ciconiae, and in the third they are intermediate 
 between the Ciconiae and the Anseres. 
 
 5. Order ANSERIPORMBS 
 
 PI. 21, Figs. 28-31 
 
 Comprising the two suborders Anseres and Palamedeae, this order 
 
 is characterized by the uniform distribution of plumules, and 
 
 the absence or rudimentary condition of the aftershaft. The Pala- 
 
 'medeae are further characterized by the total absence of apteria, 
 
 a condition found elsewhere only in the Sphenisciformes among 
 
 carinate birds. Since in the finer structure of their feathers the 
 
 two suborders have little in common, it will be more advantageous 
 
 to take them up separately. 
 
 I. Suborder Ansekbs 
 PI. 21, Fig. 28-30 
 
 a) Anas platyrhynchos 
 (1) Remex 
 
 Calamus unusually long, being considerably over one-third length 
 of quill in primaries. This elongation is a very constant and char- 
 acteristic feature. Shaft about as broad as deep, with broad, shal- 
 low ventral groove. Rami with rather broad attachment to shaft, 
 especially on outer vane, and differing from all other birds except 
 a few gallinaceous species, in the enormous development of ventral 
 ridge into a broad, thin, filmlike expansion on the basal one-third 
 to two-thirds of the barb, reaching over and adhering to the 
 adjacent ramus in front of it, producing a very conspicuous 
 macroscopic effect on lower side of feather, where the portion of 
 feather plate involved has a shiny, glazed appearance. Plate 21, 
 figure 28a, represents proximal portion of barb from inner vane 
 of a primary, showing expanded ventral edge with filmy expanded 
 ventral ridge ending abruptly. On outer vane, rami further char- 
 acterized by dense villi (pi. 21, fig. 28&). Distal and proximal 
 vanules with barbules not as different in size as in Ciconiae but 
 distals outnumbering proximals nearly as much as in latter group ; 
 about 42 distals and 23 proximals per millimeter on a barb from 
 inner vane of primary. 
 
 Inner vane. — Distal barbules (pi. 21, fig. 28c) relatively large 
 for size of feather, base about 0.27 by 0.042 mm., extremely thin 
 and filmy, pigment usually absent below line of nuclei, although this 
 area is wider than usual; ventral teeth lobate but not blunt or 
 truncate at end, being drawn out more or less into slender points. 
 Hooklets exceedingly slender and delicate, with their hooked tips 
 somewhat enlarged, usually 6 or 7 of them, progressively and 
 regularly becoming longer; ventral cilia long, slender, and not 
 
328 University of California Publications in Zoology [^oi- 13 
 
 appressed. Dorsal cilia forming a well-developed series, basal ones 
 stouter and spinelike, but not as strongly contrasted with others 
 as in Cieoniae. Proximal hariules (pi. 21, fig. 28d) also thin and 
 filmlike, with little pigment; base unusually slender, about 0.65 
 by 0.04 mm. Proximal two ventral teeth broad, lobate, and blunt, 
 followed by two or three narrow and pointed ones; pennulum little 
 shorter than base, with rudimentary barbicels always showing. 
 
 Outer vane. — Distal bariules (pi. 21, fig. 28e) with drawn-out 
 points of ventral teeth more prominent; booklets even more slender, 
 and increased in number; dorsal barbicels absent. Proximal bar- 
 iules on outer portion of barb with ventral teeth proliferated and_ 
 transformed into straight ventral barbicels, resembling teeth of a 
 comb (pi. 21, fig. 28/). 
 
 (2) Other Feathers 
 
 As in nearly all ducks, greater wing coverts form a speculum 
 of different color from rest of wing, in this case deep bluish violet. 
 For production of this color, as of other metallic colors, e. g., blues 
 and greens of various species, the pennula are transformed into 
 fiattened refrangent surfaces (pi. 21, fig. 28i) with constrictions 
 between cells, and fine, longitudinal striations on cells, which are 
 deeply pigmented with black. Base and booklet region considerably 
 reduced in these metamorphosed barbules. Barbules of inner vane 
 of speculum feathers, and proximals of outer vane also, unmodified. 
 As described at close of Part I (p. 279), modifications of distal 
 barbules are absent in albinos. 
 
 Body feathers rather loose in texture, due largely to fact that 
 bases of barbules lie in vertical plane, leaving wide spaces between 
 them. Ventral teeth of distal barbules greatly reduced, but slender, 
 subequal cilia still numerous and well formed. Just distal to hook- 
 let region, pennulum twists so that ventral cilia come to project 
 dorsally. Proximals have slender, tapering bases, inconspicuous 
 ventral teeth and rudimentary prong-like cilia. The poorly de- 
 veloped tail feathers intermediate in form between remiges and body 
 feathers. Their form is shown by plate 21, figures 28gr and h. 
 
 b) Other Types 
 
 The minute structure of the feathers is remarkably constant in 
 all the members of the Anseres. Nettion carolinense is perhaps 
 slightly more typical of the group in that the ventral teeth of the 
 distal barbules are greatly elongated and slender, as shown in plate 
 21, figure 29a. Marila, Mergus, Querquedula and other genera are 
 almost identical with Nettion. 
 
 Branta, like Anas, has the ventral teeth of the distals somewhat 
 shorter, while some of the feathers have the pennula of the distals 
 of the outer vane elongated with long brushlike cilia to produce the 
 characteristic plush-like effect. Chen very closely resembles Branta, 
 
1916] Chandler: Structure of Feathers 329 
 
 but the barbieels of the proximals of the outer vane are stouter and 
 more irregular. 
 
 Olor columbianus has the elongation of the ventral teeth of the 
 distals less extreme, as in Anas, and has the booklets even more 
 slender than in typical ducks and geese. 
 
 Speculum feathers occur in a very large number of genera, espe- 
 cially of ducks, sometimes being white, but frequently some iridescent 
 color, as blue, green, or violet, the structure in these cases being of 
 the type described above for Anas platyrhynchos. A distal barbule 
 from the brilliant green portion of a speculum feather of Nettion 
 carolinense is shown in plate 21, figure 296. The deep velvety black 
 scapular feathers of Mareca, which are tinged with metallic green, 
 have distal barbules in which the base as well as the pennulum takes 
 part in the color effect (pi. 21, fig. 30a) . 
 
 c) Down 
 
 The down barbules of all typical ducks are short, seldom over 1 
 mm. long, and usually considerably less. They are simple and thread- 
 like for the greater part of their length, but on the basal half of the 
 barbs there are developed at the tip of the barbules 3 or 4, sometimes 
 5, very conspicuous expanded nodes followed by a slender tip (pi. 35, 
 fig. 104). On the outer portion of the barbs these enlarged nodes are 
 reduced and there are a few terminal pairs of prongs taking their 
 place. The number of terminal nodes differs to some extent in dif- 
 ferent species, e. g., An^is has 2 or 3, Mareca 3 to 5, and Mergus 2 
 to 4. In Branta there are 4 to 6, which are not so large and are 
 farther separated. In Olor they are still more separated, less con- 
 spicuous, and the transitional nodes on either side are better devel- 
 oped (pi. 35, fig. 103). 
 
 d) Relationships 
 
 The feathers of the Anseres show high specialization in a num- 
 ber of points of their microscopic morphology, and are unques- 
 tionably to be regarded as the end of one line of evolution. The 
 typical ducks show the specialized characters in their highest develop- 
 ment, the geese, as represented by Branta and Chen, being lower in 
 the scale, and the swans, as represented by Olor, still lower and form- 
 ing a more or less natural bridge over the gap between the more 
 typical Anseres on the one hand, and the Phoenicopteri on the other. 
 
330 University of California Publications in Zoology ["^"l. 13 
 
 e) Summary 
 
 The Anseres are characterized as follows: 
 
 (1) Plumules evenly distributed. 
 
 (2) Aftershaft rudimentary or absent. 
 
 (3) Rami of remiges with extremely broad filmlike ventral 
 ridges, furnished with dense villi on the ventral edge on the outer 
 vane. 
 
 (4) Barbules of remiges and body feathers essentially the same, 
 the latter merely simplified. 
 
 (5) Distal barbules with elongated ventral teeth and very slender 
 booklets. 
 
 (6) Proximal barbules of inner vane with slender base, 2 prox- 
 imal ventral teeth blunt and lobate, the others narrow and pointed, 
 and a moderately long filamentous pennulum with pronglike rudi- 
 mentary barbicels. 
 
 (7) Proximals of outer vane with a series of straight, pointed 
 cilia on the pennulum. 
 
 (8) Down barbules short, with nodes undeveloped, except 3 to 6 
 or 8 near tip which are very highly developed. 
 
 Suborder Palamedeae 
 PI. 21, Fig. 31 
 
 The two genera constituting this group, Palamedea and Chauna, 
 differ in a number of important details of feather structure from the 
 Anseres. In Chauna cristata the barbs are heavily built, the pith 
 more than one cell in thickness, and with only a narrow translucent 
 ventral ridge. The distal barbules (pi. 21, fig. 31a) of the outer vane, 
 the only ones which I have obtained for study, are characterized by a 
 large, stout base with broad, lobate ventral teeth, reminiscent of the 
 Meleagridae, and by a fairly short pennulum with a very large 
 series of long slender booklets, usually eight in number, followed by 
 only a few slender ventral barbicels. The proximals (pi. 21, fig. 
 31&) have large, stout bases with the ventral teeth as in the 
 Anseres (i. e., the first two more lobate than the others), and a 
 short, rather broad pennulum as in the Ciconiae and also some Galli. 
 
 The back feathers are of a rather peculiar nature, the pennula 
 being greatly elongated to give the characteristic hoary appearance. 
 The base is long and tapering, the booklets usually five, subequal in 
 size, followed by a complete series of ventral cilia, also of approx- 
 
1916] Chandler: Structure of Feathers 331 
 
 imately equal size. The long barbicelled pennulum is without 
 pigment, resulting in the hoary appearance above mentioned. The 
 breast feathers have a much simplified type of barbules, with a 
 series of booklets and curved ventral cilia which grade into each 
 other and are all subequal in size. The pigment is distributed in 
 well-defined transverse bars. The down barbules, unlike those of 
 the Anseres, are long, 2 mm. or more, being almost simple threads, 
 a few inconspicuous prongs being developed at the nodes. 
 
 As will be seen from the above, the Palamedeae are peculiar in 
 that they combine the characters of a number of other groups of 
 birds in a confusing manner and could not readily be associated 
 with any group on the basis of their feather structure. The distal 
 barbules of the remiges resemble those of the Anseres in number 
 and form of the pennular barbicels, but the ventral teeth are most 
 closely paralleled by the Meleagridae ; proximals of the remiges 
 combine anserine, ciconiid, and galline characters; the barbules of 
 the breast feathers constitute a type of their own, probably de- 
 generated ; and finally the down barbules are long and threadlike, 
 unlike either Anseres or Galli, but near the Ciconiidae. 
 
 6. Order FALCONIFORMES 
 Plates 22, 23 
 The Falconiformes include a rather well-defined group divisible 
 into three distinct suborders, which, as in the case of Anseriforraes 
 and Ciconiiformes, can more readily be treated separately. As an 
 entire group they show unmistakable evidence of being derived 
 from a parent stock somewhere intermediate between the Stegano- 
 podes and Ciconiae. In the entire order the plumules are uniformly 
 distributed, powder down is present in a few, and the aftershaft is 
 present in all but the Cathartae, which, however, seem otherwise to 
 be the lowest in the evolutionary scale. 
 
 I. Suborder Cathartae 
 PI. 22, Fig. 34 
 
 a) Oymnogyps calif ornianus 
 (1) Remiges 
 
 Barbs moderately broad, but very heavily built, pith of rami 
 more than one cell in thickness. Barbules large, the distals larger 
 than usual relative to proximals. Fewer barbules per unit of 
 
332 University of California Publications in Zoology [Vol. 13 
 
 measure than in any group previously studied, about 28 distals and 
 12 or 13 proximals per millimeter. 
 
 Inner vane. — Distal barhules (pi. 22, figs. 34a, 34&) with large 
 bases, about 0.4 mm. long by 0.05 mm. wide. Stout base of the distals 
 furnished with moderate, lobate ventral teeth; the pennulum stout, 
 with about 5 stout, progressively longer booklets, followed by a few 
 long, slender ventral cilia, the distal portion devoid of them. Two 
 basal dorsal cilia developed as in Plotus, forming stout, blunt, 
 laterally projecting, spinelike processes; all the other dorsal barbi- 
 cels rudimentary. Distal to these characteristic dorsal cilia there is a 
 bend in dorsal contour of barbule as shown in the figures. When 
 detached, barbules usually lie in the position shown in plate 22, 
 figure 34&. Proximal barbules (pi. 22, fig. 34c) with relatively 
 small bases, a series of moderate ventral teeth, and pennulum 
 which is broad proximally, but rapidly tapering to fine thread. 
 Pennulum somewhat shorter than base. 
 
 Outer vane. — Distals (pi. 22, fig. Md) differ from those of inner 
 vane mainly in possessing larger number of booklets, in greater 
 development of ventral cilia, and in absence of dorsal ones. Prox- 
 imals, as shown by plate 22, figure 34e, very similar to those of 
 inner vane, but slightly larger, and ventral teeth a little more 
 prominent, at extreme tip becoming slightly more separated from 
 one another and assuming more of a toothlike form. Typical 
 ventral cilia not developed. 
 
 b) Other Types 
 
 Cathartes aura has practically the same types of barbules, though 
 smaller and the barbicels not so stout. On the broad basal portion 
 of the primaries, the proximal barbules at the tip of the barbs have 
 the ventral teeth transformed into toothlike cilia, but they are not 
 proliferated and do not become slender or hooked. 
 
 The back feathers of Cathartes aura have barbules resembling 
 those of the outer vane of the remiges, the distals differing in hav- 
 ing a very stout heavy pennulum, with fewer and more slender teeth, 
 and with stout appressed ventral cilia. The breast feathers have 
 the barbules very much simplified and reduced. No flexules are 
 ever developed. 
 
 c) Down 
 
 The down barbules of Cathartae are very long and slender, 
 with the nodes only marked by slight enlargements, showing best 
 on the proximal vanule, the internodes being very long. The bases 
 of the down barbules are hardly differentiated from the pennula, 
 being very narrow. 
 
1916] Chandler: Structure of Feathers 333 
 
 d) Relationships 
 
 The Cathartae show many characters in the minute feather struc- 
 ture which appear to show rather close alliance with the Steganopodes, 
 and in one particular, namely in the nature of the distal barbulesof 
 the inner vane, show an astonishing likeness to Plotus. This is a char- 
 acter which could easily have arisen separately in the two groups, as 
 it undoubtedly has done in other eases, e. g., the Bucerotidae, but the 
 other likenesses between the Cathartae and the Steganopodes as a 
 group make it more probable that Plotus and the Cathartae had a 
 common ancestor. As will be shown below, the present group differs 
 considerably from the Accipitres but the gap is bridged to some 
 extent by the Gypogerani and Vulturidae. 
 
 e) Summary 
 
 The main characters of the Cathartae are as follows: 
 
 (1) Barbules relatively widely spaced on the barb, and of large 
 size. 
 
 (2) Distals of remiges characterized by large stout base, mod- 
 erate ventral teeth, heavy pennulum, and a series of progressively 
 longer stout booklets, followed by a few large, more or less appressed 
 ventral cilia, the dorsal cilia being reduced to 2 stout, blunt, spine- 
 like, basal ones immediately beyond which there is a conspicuous 
 bend in the barbule. 
 
 (3) Proximals with moderate base and ventral teeth, pennulum 
 shorter than base, and with no cilia on either inner or outer vane. 
 
 (4) Down barbules long and slender, with long intemodes and 
 very inconspicuous nodes. 
 
 II. Suborder Gypogerani 
 PI. 22, Fig. 35 
 Though in general appearance the secretary birds are farther 
 removed from typical Accipitres than are the American vultures, 
 in feather structure they have a much closer resemblance. 
 
 a) Gypogeranus serpentarius 
 (1) Remex 
 
 Inner vane. — Distal iariules (pi. 22, fig. 35c) more or less inter- 
 mediate in form between those of the other suborders of this group. 
 Base and ventral teeth moderate, booklets 5 in number, and slender 
 as in Palconidae, ventral cilia slender and rather inconspicuous, 
 
334 University of California Publications in Zoology V^oy.. 13 
 
 and dorsal cilia, except basal two, rudimentary. The latter not 
 so stout or so close together as in the Cathartae but more so than 
 in the Falconidae. Proximal iariules (pi. 22, fig. 35d) relatively 
 small and of typical falconid type. 
 
 Outer vane. — Distal barbules differ from those of inner vane in 
 the greater length of the booklets and in the shorter cells of the 
 pennulum, the latter resulting in the close approximation of the 
 ventral cilia, so that they appear brushlike. Proximal barbules 
 have well-developed, hooked ventral cilia, as in Accipitres. 
 
 Distal to the incision of the feather, where vanes are narrowed, 
 distal barbules of inner vane do not possess dorsal barbicels, and 
 proximal barbules of outer vane do not have hooklike ventral cilia. 
 The latter are developed but lie closely appressed to the barbule. 
 
 (2) Back Feathers 
 
 Gray hack feathers of Gypogeranus with distal barbules with 
 relatively large pennula, furnished with small, rather weak hook- 
 lets and long, slender, closely set ventral cilia. Pigment concen- 
 trated in spots, resulting, as in gulls, in bluish tinge in gray color 
 (pi. 22, figs. 35a, 35b). 
 
 (3) Down 
 
 The down barbules do not materially differ from those of other 
 Falconiformes, being moderately elongate, reaching a length of 
 2 mm. or more, the base poorly developed, and pennula very slender 
 with slightly enlarged nodes, which, especially at tip, are furnished 
 with short, inconspicuous prongs. 
 
 b) Summary and Relationships 
 
 The Gypogerani are much nearer to the Accipitres than to the 
 Cathartae as far as feather structure is concerned. They agree 
 more closely with the Cathartae in the character of the dorsal cilia 
 of the distal barbules of the inner vane, but in all other details of 
 structure they are almost identical with the Accipitres. 
 
 III. Suborder Accipitres 
 
 The birds of this suborder form a compact, well-defined group, 
 including the hawks, eagles, ospreys, and Old "World vultures. The 
 owls used to be associated with this group until further investigation 
 showed that they were in reality widely separated, with many points 
 in common as the result of parallel evolution and similar adapta- 
 tion. The morphology of the feathers agrees with the osteology, 
 myology, and other characters in showing that the Striges really 
 have nothing in common with the Accipitres as regards near rela- 
 tionship. As in other Falconiformes, the plumules of the Accipitres 
 are uniformly distributed, and in a few forms powder-down is 
 present. The aftershaft is present, and usually well developed. 
 
^^^^] Chandler: Structure of Feathers 335 
 
 a) Buteo iorealis 
 
 (1) Remiges 
 
 Shaft about as wide as deep, quadrangular, with well-developed 
 ventral groove. Vanes notched or incised on outer vanes, the rami 
 of outer vane beyond point of incision as wide as shaft is deep, 
 the pith more than one cell in thickness, with moderate ventral 
 ridge, with villi on ventral edge. Proximal vanule with over two- 
 thirds as many barbules as distal vanule, there being 28 to 30 distal 
 barbules and 22 to 23 proximals per millimeter, the latter small 
 relative to distals. 
 
 Inner vane. — Distal iariules (pi. 23, fig. 38a) with long, slender 
 base, about 0.38 by 0.06 mm., with relatively small, but broad and 
 lobate ventral teeth; pennulum much longer than base, with 5 
 slender, moderately long booklets, which progressively increase in 
 length, a well-developed series of slender, filamentous ventral cilia, 
 and a series of slender dorsal cilia, the basal ones stouter and 
 more spinelike, but not lobate as in the Cathartae. Proximal bar- 
 bules (pi. 23, fig. 38&) with base relai^ively small as compared 
 with distals, about 0.75 by 0.07 mm., \^ith 4 or 5 short, pointed 
 ventral teeth and moderately slender pennulum, a little over half 
 as long as base. 
 
 Outer vane. — Distal barbules much like those of inner vane, but 
 base shorter and relatively stouter, pennulum shorter, the booklets 
 usually 6 in number, and relatively longer, and no dorsal cilia. 
 Proximal barbules (pi. 23, fig. 38c) on terminal portion of barbs 
 with a series of highly developed hooked ventral cilia, basal ones, 
 representing ventral teeth, short and triangular, middle ones almost 
 like booklets of distal barbules, outer ones smaller, weak, and fila- 
 mentous. 
 
 (2) other Feathers 
 
 Back feathers have structure differing from remiges chiefly in 
 simplification. Barbules more slender, especially base, all the barbi- 
 eels considerably reduced and vanules open, i. e., with spaces 
 between barbules, which stand in vertical plane relative to surface 
 of barb (see plate 23, figures 41a and 416, representing barbules 
 from back feather of Falco rusticola). Breast feathers similar, but 
 still more simplified, the bases of barbules very elongate and slender 
 and all barbicels greatly reduced. 
 
 b) Other Types 
 
 Examination of a large number of species of different sections 
 of the suborder shows that there is little variation in the form of 
 the barbules. Feathers of species of Buteo, Circus, Haliastur, 
 Archibuteo, Spizaetus, Haliaeetus, Aquila, Elanus, Falco, Pandion, 
 Polyborus, and Gyps have been examined, and no striking devia- 
 tions from the type described have been found. In the distal bar- 
 bules of Falco peregrinus (pi. 23, fig. 36a) the pennulum is rela- 
 
336 University of California Publications in Zoology [Vol. 13 
 
 tively short, but the proximals, (pi. 23, figs. 36&, 36c) almost exactly 
 as in Buteo. FaXco sparverius, again, has a long pennulum on 
 the distal barbules. In Haliaeetus leucocephalus the pennulum of 
 the distals is short, and the basal dorsal cilia unusually stout 
 (pi. 23, fig. 39a). The proximals (pi. 23, fig. 38&) have longer 
 and more prominent ventral teeth than in Buteo. Polyhorus cheri- 
 way agrees with Haliaeetus in the small pennulum and spinelike 
 dorsal cilia of the distal barbules (pi. 23, fig. 40a.). 
 
 The structure of the feathers of Circus hudsonius was worked 
 out in detail by me (1914) ; they agree with Buteo in all important 
 details. 
 
 In Gyps fulvus, representing the Vulturidae, the barbules of 
 the outer vane of the remiges differ considerably from the type, as 
 shown by plate 22, figures 33c and 33c?. The distal barbules have 
 enormously developed booklets and ventral cilia, giving the barbule 
 a very unique appearance. The proximal barbules on the terminal 
 portion of the barbs do not acquire hooked cilia as in other Accip- 
 itres, but differ from those of the inner vane merely in the slight 
 proliferation of the ventral teeth, which are only partially trans- 
 formed into cilia, as shown in plate 22, figure SSd. The back 
 feathers of this species differ from those of more typical accipitrines 
 only in the great width of the pennulum of the distal barbules 
 (pi. 22, figs. 33a, 336). 
 
 c) Down 
 
 The down barbules are very variable, even within a single genus. 
 In the majority of the group, e. g., Accipiter cooperi, Pandion 
 carolinensis, Circus hudsonius, Buteo iorealis, and Gyps fulvus, 
 the barbules are elongate and very slender, with very slight swell- 
 ings at the nodes, and short prongs toward the tip. In Falco, how- 
 ever, the nodes are more enlarged, not conspicuously so in F. rusti- 
 cola or F. peregrinus but strikingly so in F. sparverius where the 
 pigmentation is in deep nodular spots. As shown in plate 35, figure 
 105, the internodes are very slender and frequently wavy, the latter 
 condition being very unusual in down barbules. 
 
 d) Relationships 
 
 The microscopic morphology of the feathers of the Accipitres 
 presents many points which are difficult of interpretation. Admit- 
 ting their relationship with the Cathartae, which seems to be 
 
1916] Chandler: Structure of Feathers 337 
 
 plainly indicated by other features in their anatomy, and is made 
 rather easy, even taking into consideration the structure of their 
 feathers, on account of the intermediate condition of Gypogeranus, 
 the Accipitres must be regarded as derivatives of a Steganopode- 
 like bird. Yet in the form of the ventral cilia of the proximal bar- 
 bules, and of ventral teeth, booklets, and dorsal cilia of the distals, 
 they come .very close to the Galli. The down of some resembles 
 that of the Steganopodes while that of others, e. g., Falco sparverius, 
 resembles that of some Coraeiiformes. However, all of these points 
 of resemblances are features which could easily be conceived of as 
 having been developed more than once, and it seems best to regard 
 the Accipitres as derivatives of the Steganopodes through the 
 Cathartae and Gypogerani. 
 
 e) Summary 
 
 The Accipitres are characterized as follows: 
 
 (1) Distal barbules of inner vane of remiges with relatively large 
 base, lobate ventral teeth, 5 booklets, slender filamentous ventral cilia, 
 and slender dorsal cilia, the basal ones spinelike ; pennulum frequently 
 much longer than base. 
 
 (2) Distals of outer vane with shorter base, and relatively shorter 
 pennulum with shorter cells, making a brushlike series of ventral cilia. 
 
 (3) Proximals of inner vane with relatively small base, short 
 pointed ventral teeth and moderately long pennulum. 
 
 (4) Proximals of outer vane, on distal half of barb, with well- 
 developed series of hooklike ventral cilia. 
 
 (5) Body feathers differing from remiges only in simplification, 
 and slender form of barbules. 
 
 (6) Down barbules very fine and slender, the nodes more or less 
 enlarged, sometimes pigmented. 
 
 7. Order GALLIFORMES 
 Plate 24 
 Comprising a very large assemblage of the so-called "game- 
 birds," the present order is subdivided into four suborders as fol- 
 lows: (1) Mesaenatides, represented only by the kagu or mesite 
 of Madagascar; (2) Galli, including the megapodes, curassows, 
 pheasants, partridges, turkeys, etc.; (3) Turnices, including the, 
 Hemipodes of the Old "World; and (4) Opisthocomi, to which 
 belongs only the peculiar Hoactzin of South America. 
 
338 University of California Publications in Zoology [Vol. 13 
 
 Unfortunately, I have been unable to secure feathers of the first 
 and fourth suborders for examination, and the relationships sug- 
 gested by their feather structure cannot, therefore, be discussed. 
 The other two groups, Galli and Turnices, though in superficial 
 appearance very similar, differ ip so many details of feather struc 
 ture that they may more advantageously be considered separately. 
 
 I. Suborder Galli 
 PI. 26, Figs. 42-47 
 Though containing a very large number of species and genera, 
 this suborder forms a fairly compact and well-defined group. In 
 general they are characterized by the restriction of the plumules to 
 the apteria, and by the variability of the aftershaft. In some 
 members of the group, e. g., Bonasa, the latter is better developed 
 than in any other group except Casuariiformes, while in others, e. g. 
 Pavo, it is very small and almost rudimentary. 
 
 a) Gallus domesticus 
 
 (1) Remex 
 
 Shaft slightly wider than deep, with a broad, conspicuous ventral 
 groove; calamus, in contrast to the condition found in Anseres, 
 short, not greatly inflated, its caliber less than that of the shaft. 
 
 Vanes firm, barbs of the inner vane set about 18 per centimeter, 
 those of outer vane considerably less, especially in the primaries. 
 Vanules with barbules very close set, about 40 distals and 32 prox- 
 imals per millimeter in a typical portion of the feather, this number 
 of proximals being larger relative to the number of distals than 
 in most water-birds. 
 
 Inner vane. — Distal barbules (pi. 24, fig. 42a) with base about 
 0.26 mm. in length by 0.04 mm. in width, the pennulum about the 
 same length. Base rather broad and quadrangular, with usually 3 
 v.entral teeth, these in the form of broad lobes, very thin and film- 
 like. Nuclei in a conspicuously diagonal line, on account of the 
 short, broad form of the base, with its broad ventral teeth. Pen- 
 nulum with 6 to 8 hooklets of moderate' size, progressively increas- 
 ing in length, not slender with enlarged hooks, as in Anseres, but 
 stouter basally. Ventral cilia of moderate size, not flexible or 
 appressed, but in the form of stout, strongly curved, hooklike 
 processes, decreasing in size toward the tip, but relatively well- 
 developed on the whole length of the pennulum; 3 or 4 sharp, 
 spinelike, dorsal cilia, not, however, highly modified as broad lobate 
 or hoodlike projections. More distal cells of the pennulum with 
 short, pronglike, rudimentiary dorsal cilia. 
 
 Proximal barbules (pi. 24, fig. 42b) with slender base, about 
 0.6 mm. long by 0.05 mm. wide, with a series of short, pointed, 
 lobate ventral' teeth. Pennulum remarkably short, especially on 
 
1916] Chandler: Structure of Feathers 339 
 
 more basal portion of barb, for the most part not exceeding one- 
 third the length of the base, broad basally, tapering rapidly to a 
 slender but short filament. 
 
 Outer vane. — Distal barhules (pi. 24, fig. 42c) even shorter than 
 on inner vane, total length under 0.5 mm., the base constituting 
 about one-half of this. Base slightly curved longitudinally, with 
 lobate ventral teeth not as broad as in inner vane. Pennulum with 
 booklets about as in the inner vane. Ventral cilia more nearly sub- 
 equal to each other for the whole length of the pennulum, strongly 
 curved, and well separated from each other. Dorsal cilia in the 
 form of short prongs. 
 
 Proximal harbules on proximal portions of the. barbs closely 
 resembling those of the inner vane, but pennulum even shorter. 
 On the outer portion of the barbs, the proximals (pi. 24, fig. 42d, 
 42e) with ventral teeth proliferated and transformed into a series 
 of stout, strongly hooked ventral cilia, in some cases almost exactly 
 like booklets in form, more numerous on more distal barbules, but 
 only 3 to 5 basal ones strongly hooked. 
 
 (2) other Feathers 
 Body feathers, where there are no special color modifications, 
 merely simplifications of remex type, distal barbules resembling 
 outer vane type, proximals the inner vane type. Vanes not firmly 
 interlocking and usually a large portion of feather downy. After- 
 shaft with well-formed shaft, its vanes distinct and separate, barbs 
 attached in linear series as in contour feathers, and not tuftlike 
 as is more usual. Vanules of the interlocking or pennaceous por- 
 tion always open, i. e., barbules in a vertical plane and therefore 
 with spaces between them. Distal barbules with long, slender bases, 
 with more or less reduced ventral teeth. Pennulum with 3 to 5 
 short, weakened booklets followed by a series of the same type of 
 short, curved, infiexible and subequal ventral cilia as in the 
 remiges, these becoming short and more or less rudimentary in 
 looser. feathers. Proximal barbules (pi. 24, fig. 42/) with elongated, 
 tapering bases, with moderate, rather slender, ventral teeth. Pen- 
 nulum short, as in remiges, almost invariably considerably less 
 than half length of base; no cilia. 
 
 b) Other Types 
 
 The minute structure of the remiges is remarkably constant 
 throughout the group, and it is possible to distinguish a gallinaceous 
 bird from all others very easily by the structure of its remiges. The 
 description of the feathers of Gallus domesticus will hold, with very 
 slight modification, for all the Phasianidae. 
 
 In the Tetraonidae the pennulum of the more terminal proximal 
 barbules of the outer vane has a lonjer series of ventral cilia, which 
 are relatively somewhat shorter, and of more uniform size. In some 
 members of the family the ventral ridge of the barbs is extremely 
 broad, as in Anserine birds. See plate 24, figures 43a, b, and c. 
 
340 University of California Publications in Zoology [Vol. 13 
 
 In the Meleagridae the distal barbules of the remiges have the 
 ventral teeth enormously developed as broad, thin filmlike sheets, 
 while the booklets are very long and slender, almost as much so as 
 in Olor. See plate 24, figures 44a, 446. 
 
 In the Megapodidae and Cracidae, as exemplified by the genera 
 Megapodius and Penelope, the structure of the feathers is very 
 similar to each other, both varying a little from the usual type. In 
 the remiges of Megapodius and Penelope the distal barbules (pi. 24, 
 fig. 45a, 46a) are characterized by a rather elongate base, somewhat 
 sinuate in ventral profile, with relatively small ventral teeth. The 
 booklets and ventral cilia are of typical gallinaceous form, but the 
 dorsal cilia differ in the slightly stouter, more thomlike form of the 
 basal two. The proximal barbules which possess ventral hooklike 
 barbicels (pi. 24, fig. 456) are restricted to a smaller portion of the 
 tip of the barbs. 
 
 The body feathers, where there are no special color modifications, 
 undergo a similar simplification and assume a very similar form, 
 in nearly all gallinaceous birds. The aftershaft, when developed, is 
 of the form described for Gallus domesticus, with well-developed 
 shaft and distinct separate vanes ; the vanes of the main feather 
 plate are always of the open type; the barbules are nearly always 
 at least recognizably similar; the distals with curved, hooklike 
 ventral cilia, the proximals with relatively extremely short pennula. 
 
 c) Down 
 
 The down barbules of gallinaceous birds differ considerably on 
 different portions of the barbs, and to some extent on different 
 barbs (see Part I, p. 270), but reach their highest and most typical 
 development on the basal portion of the distal vanule of the well- 
 developed down barbs of the main feather plate. 
 
 These typical barbules (pi. 36, fig. 108) are readily distin- 
 guishable from those of any other group of birds. They are densely 
 set, sometimes as many as 50 per millimeter on each side near the 
 base of the barbs, though always considerably less at the middle 
 and tip. They are usually extremely long, reaching a length of 
 over 5 mm. in various species of pheasants and turkeys, though as 
 a rule they are more nearly 3 mm. in length. The base of these 
 barbules is only slightly differentiated. The pennulum on its more 
 proximal portion has poorly developed swollen nodes (pi. 36, fig. 
 1086), which, however, soon indrease in size and develop a typical 
 
^^^^^ Chandler: Structure of Feathers 341 
 
 ringlike form (pi. 36, fig. 108c). Some of these rings frequently, 
 in fact almost always to a greater or less extent, break loose from 
 the nodes, and slide along on the slender, filamentous barbule like 
 rings on a wire, sometimes breaking up into groups of 5 or 6. It is 
 possible to move them along on the barbules by placing them on a 
 slide and moving the cover glass. Toward the tip of the barbules 
 the ringlike structure is again lost, and the nodes become simply 
 swollen. On the proximal vanule these rings are usually not so 
 perfectly developed, and on the more distal portion- of both vanules 
 the nodes become simply swollen, and shaped more or less like a 
 eucalyptus seed, with short prongs, or the barbule becomes almost 
 smoothly filamentous, with indistinct nodes. The outside diameter 
 of the rings in Meleagris virginiana, for instance, is about 0.012 
 mm., while that of the internodes of the barbules is only 0.004 to 
 0.005 mm. The down at the base of remiges and rectrices, and that 
 of the aftershafts, never possess the ringlike structure. The downy 
 structure varies very little in any of the families of the suborder. 
 
 d) Color Modifications 
 
 There are many interesting color modifications in this group, 
 especially in the Phasianidae, but they can only briefly be discussed 
 here. White is usually produced by diffusion of light merely from 
 translucent barbules, but in Lagopus the barbules (pi. 24, fig. 47a) 
 are filled with minute bubbles which tend further to diffuse the 
 light. Deep glistening red, yellow, and orange colors are usually 
 produced by pigmented, highly polished barbs which are naked, or 
 possess much reduced barbules. Changeable metallic lilacs, fiery 
 reds, blues, greens, and purples are produced by highly refrangent, 
 simple, rodlike barbules, the silvery blue feathers of Phasianus 
 torquatus, for example, being a result of the combination of white 
 barbs with rodlike blue barbules. In the coherent green vanes of 
 the tail feathers of roosters, and other similar feathers, the pennula 
 of the distal barbules (pi. 24, fig. 42gf) are responsible for the color 
 as in the Anseres, the individual cells, however, not being demarcated 
 by constrictions, but the whole pennulum in the form of a curved, 
 spoonlike structure (pi. 24, fig. 42/). 
 
 There is a very unusual condition found in the blood-red breast 
 feathers of the golden pheasant, where the barbs are closely appressed 
 and brought to lie almost parallel with the shaft. In these feathers 
 two barbs frequently fuse to form a single one at a short distance 
 
342 University of California Publications in Zoology [Vol. 13 
 
 from the shaft, which remains single for all the rest of its length. 
 In one case the barb was seen to be split for only a portion of its 
 length, being fused into one at both base and tip. 
 
 In peacocks the highly iridescent blue, green, and bronze colors 
 are the result of barbules which are totally metamorphosed in both 
 base and pennulum to produce color. 
 
 e) Relationships 
 
 According to the feather structure, the Galli are highly special- 
 ized birds, the broad, ventral teeth of the distal barbules, the hooked 
 ventral cilia of the proximals, and the nature of the down, being 
 specializations and decidedly not primitive characters. The form 
 of both distal and proximal barbules, as well as the form of the 
 down, shows unmistakable affinity 'to that of the Columbae on the 
 one hand, and the Cuculiformes on the other, the so-called "Peris- 
 teropode" group (Megapodidae and Cracidae) more strongly sug- 
 gesting the cuculoid birds, while the "Alectoropodes" (pheasants, 
 grouse, etc.) are reminiscent of the Columbae. (Compare plates 24, 
 29, and 30.) ■ 
 
 Unmistakable relationship is also shown to the Tinami, which, 
 according to feather structure, should be considered as a specialized 
 offshoot from a primitive gallinaceous stem. This will be more 
 fully discussed under Crypturiformes. 
 
 In sOme respects, namely in the form of the barbicels of the 
 distal barbules of the remiges, some affinity to the Rallidae and 
 other gruid forms is shown, but the nature of the body feathers is 
 totally different, and it is more probable that the few striking 
 similarities are rather to be interpreted as the result of parallel 
 evolution. (Compare plate 24 with plate 25.) 
 
 The relationship of the Galli with the Turnices will be discussed 
 under the latter. 
 
 f) Summary 
 
 The Galli are characterized as follows: 
 
 (1) Plumules only in apteria. 
 
 (2) Aftershaft variable, but when developed, with distinct and 
 separate vanes. 
 
 (3) In remiges, proximal barbules small as compared to distals, 
 and both series very close set. 
 
1916] Chandler: Structure of Feathers 343 
 
 (4) Distal barbules of remiges short, the bases short with large, 
 thin, lobate ventral teeth, the pennula with a long series of pro- 
 gressively longer booklets, a complete series of curved, inflexible, 
 ventral cilia, and in the inner vane a series of little-specialized, 
 spiny, dorsal cilia. 
 
 (5) Proximal barbiiles of inner vane with moderate bases with 
 short, pointed, ventral teeth, and with very short pennula. 
 
 (6) Proximals of outer vane, on distal portion of barbs, with a 
 highly developed series of stout, hooked, ventral cilia, sometimes 
 very closely resembling booklets. 
 
 (7) Barbules of body feathers differing from remiges only in 
 simplification of structure, no flexules ever developed. 
 
 (8) Down, where typically developed, with extremely long, 
 slender barbules, with detachable, ringlike structures at the nodes. 
 
 II. Suborder Tuenices 
 PI. 24, Fig. 48 
 The Hemipodes, or bustard quails, belonging to the two rather 
 divergent genera Turnix and Pedionomus, are small, quail-like ground 
 birds of the southern parts of the Old World. They constitute a 
 rather isolated group whose place in the system of classification 
 has been in considerable doubt. 
 
 a) Turnix lepurana 
 
 (1) Remex 
 
 Feather small, the wing being somewhat reduced in size; shaft 
 with slight ventral groove ; iarbs not deep, the ventral ridge narrow. 
 
 Inner Vane. — Distal barbules (pi. 24, fig. 48a) small; base about 
 0.2 mm. long by 0.03 mm. wide, tapering conspicuously to ventral 
 teeth, which are relatively smaller than in Gallus, otherwise very 
 similar; nuclei in conspicuously diagonal line. Pennulum distinctly 
 galline in form, slightly longer than base. Hooklets rather short, 
 usually 5 in number. Ventral cilia not well developed except im- 
 mediately distal to hooklets, as in Ardeae, of distinctly galline 
 and not ardeid form, however. Dorsal cilia, except basal two, in 
 form of short prongs as in Galli, but basal two larger and thorn- 
 like in form (pi. 24, fig. 48a). Proximal barbules (pi. 12, fig. 48&) 
 moderately slender, base and ventral teeth as in Galli, pennulum 
 very slender and filamentous, almost equal to base in length. 
 
 Outer vane. — Distal barbules very similar to those of inner vane, 
 but with 6 hooklets, and no dorsal barbicels, and never more than 
 3 well-developed ventral cilia. Proximal barbules of basal and 
 middle parts of barb like those of inner vane, but pennulum much 
 shorter, much as in Galli. Towards tip of barb, ventral cilia devel- 
 oped almost exactly as in Tetraonidae. 
 
344 University of California Publications in Zoology Vfoi.. 13 
 
 (2) other Feathers 
 
 Bach feathers rather loose-vaned. Aftershaft with long shaft 
 and distinct vanes, but barbs much farther apart than in Galli, 
 therefore not such a compact structure. Barbules much simplified. 
 Distals with elongated, slender base, with reduced ventral teeth; 
 pennulum greatly elongated and threadlike, three times length of 
 base on basal portion of barb, 4 short, rather weak teeth, and 2 or 
 3 short, blunt ventral cilia immediately beyond booklets. Prox- 
 imals, near base of barb, with slender but well-formed base, 4 or 5 
 short but slender and sharp ventral teeth, and greatly elongated 
 pennulum. Towards tip of barbs, pennula shortened, and barbules 
 greatly reduced and simplified. 
 
 Breast feathers very similar, but pennula on basal barbules not 
 so elongate. Aftershaft weaker. 
 
 h) Down 
 
 The down is distinctly different from that of the Galli. Ringlike 
 structures are never developed at the nodes, the latter being in- 
 conspicuous and only slightly enlarged, and never pigmented, al- 
 though the internodes have black pigment. The length of the bar- 
 bules is moderate, seldom reaching over 2 mm. 
 
 c) Relationships 
 
 The structure of the distal and proximal barbules of the remiges, 
 while strikingly galline in some respects, is likewise very similar, 
 in fact more so, to Eurypyga. The structure of the down, which 
 has such a strikingly characteristic development in the Galli, in 
 these birds is totally different, but is almost exactly the same as 
 that of Eurypyga. It might be suggested that the Gruiformes and 
 Galliformes are divergent branches of a common primitive stem, 
 and that the Turnices and Eurypyga are to be considered as more 
 or less nearly related early offshoots either from the gruiform or 
 galliform branch, thus exhibiting somewhat intermediate characters. 
 
 d) Summary 
 
 The Turnices are characterized as follows, in common with the 
 Galli: 
 
 (1) Plumules sparse, restricted to apteria. 
 
 (2) Aftershaft present, with long shaft and distinct vanes. 
 
 (3) Distal barbules of remiges with broad bases, with broad, thin 
 ventral teeth and strikingly diagonal line of nuclei; pennulum with 
 
^^^^] Chandler: Structure of Feathers 345 
 
 short, stout booklets and short, curved, inflexible ventral cilia, but 
 only the proximal ones developed. 
 
 (4) Proximal barbule with base moderate and ventral teeth 
 well developed but not conspicuous, those of distal part of barbs of 
 outer vane with well-developed series of ventral cilia, the proximal 
 one hooked. 
 
 (5) Barbules of back and breast feathers mere simplifications of 
 remex type. 
 
 In the following characters they differ from typical Galli: (1) 
 poor development of barbicels on terminal part of pennulum and 
 stout, thornlike form of first two dorsal cilia of distal barbules; 
 
 (2) rather long, filamentous pennulum of proximal barbules; and 
 
 (3) moderately long down barbules with slightly enlarged un- 
 pigmented nodes, the internodes with black pigment. 
 
 8. Order CRYPTURIFORMES 
 Plate 25 
 This order, which includes the aberrant South American tin- 
 amous, has in some ways the most specialized feather structure of 
 any existing birds. They form a compact group of some forty 
 species, all in the family Tinamidae. They differ from all other 
 birds in having plumules present between the contour feathers, 
 while absent in the apteria. The aftershaft is rudimentary or' 
 absent in some genera but large and well developed, with distinct 
 vanes, in other genera (e. g., Bhynchotes) . Although strictly ground 
 birds which can fly very poorly and have a remarkable lack of con- 
 trol of the flight powers they do possess, the small wings have remiges 
 which are very well developed. 
 
 a) Tinamus solitarius 
 
 (1) Remex 
 
 Calamus short and of smaller caliber than shaft. Shaft slightly 
 wider than deep, with small median groove. Vanes extremely flrm 
 and elastic, the barbs adhering to each other with remarkable ten- 
 acity. Rami not deep, the ventral ridge rather narrow; about 25 
 per centimeter on each side basally, 16 to 18 for greater part of 
 feather. 
 
 Inner Vane. — Distal barbules (pi. 25, flg. 49a) relatively very 
 small, base very short and broad, about 0.35 mm. long by 0.04 
 wide, the ventral teeth broad, lobate, and filmlike. Pennulum, in 
 side view, of peculiar shape, narrow in booklet region, then becom- 
 ing very broad (about 0.15 mm.) and thence tapering evenly to tip. 
 
346 University of California Piihlications in Zoology f,VoL. 13 
 
 Hooklets short, subequal in length, and extremely numerous, 
 usually 8. Proximal 3 or 4 ventral cilia moderate, not curved, more 
 or less appressed, more distal ones rudimentary. Dorsal cilia 
 strikingly similar to neural spines of dorsal vertebrae of a dog, in 
 relative size, shape, and general direction, the first two or three 
 rapidly increasing in size, and progressively pointing more distally, 
 the remaining ones slowly decreasing again but continuing to pro- 
 ject at a smaller and smaller angle. Proximal harhules unique 
 (pi. 25, fig. 49b). Bases about 0.5 mm. long by 0.05 mm. wide, 
 very much curved transversely, so that dorsal part lies almost 
 parallel with ventral part, a device taking the place of a dorsal 
 flange. Pennula completely fused into a solid bar lying parallel 
 with ramus, the ventral teeth, one or two in number, projecting 
 ventrally just proximal to the bar; dorsal teeth absent. Hooklets 
 of distals hook under recurved dorsal edge of proximals, and fused 
 pennula of latter prevent their slipping out under strain. 
 
 Outer Vane. — Structure of distal iariules exactly same as in 
 inner vane, except the less development of more basal dorsal cilia 
 (pi. 25, fig. 49c). Outer bar formed by fusion of pennula of prox- 
 imals same as on inner vane for over nine-tenths of vanule, the 
 proximal barbules of the distal 2 or 3 millimeters with well- 
 developed, strongly hooked barbicels on free pennulum, as in Galli. 
 
 (2) other Feathers 
 
 The back feathers with distal barbules with rather elongate, 
 rectangular base, ventral tooth single, much reduced, pennulum with 
 broad face in nearly same plane as base, hooklets reduced to 3 or 4, 
 other barbicels short, blunt, and more or less rudimentary (pi. 25, 
 fig. 49d). Proximal barbules differing only in having a narrower 
 base, which stands vertically, the bar of fused pennula carried to 
 very tip on both vanes in well-developed feathers (pi. 25, fig. 49e). 
 In looser ones, and in breast feathers, pennula of proximal barbules 
 imperfectly fused on distal half of barb, and on distal third no 
 fusion whatever. Distal barbules of breast feathers like those of 
 back feathers, except that pennulum has long filamentous tip. 
 
 b) Other Types 
 
 All species of tinamous are strikingly similar in the structure of 
 their feathers. The remiges of Nothocercu^ frantzii, for instance, 
 differ only in the slightly longer pennulum of the distal barbules, 
 and the more restricted area of free barbicelled proximals on the 
 outer vane. The back and breast feathers have been examined in 
 different species of five different genera (Nothocercus, Tinamus, 
 Bhynchotus, Nothura, and Calopezus), and in all the structure of 
 the barbules is remarkably similar, differing only in the relative 
 length of the pennula of the distal barbules, development of ventral 
 cilia, etc. 
 
1916] Chandler: Structure of Feathers 347 
 
 c) Down 
 
 The downy structure in Calopezus and Nothura is exactly the 
 same as in typical gallinaceous birds, not only in the structure of 
 the typical basal barbules of the distal vanule, which have detach- 
 able rings of the same form, but also in the method and degree of 
 simplification in other parts of the barbs. In Tinamus and Notho- 
 cercus, on the other hand, the detachable rings are only slightly 
 developed, but the more basal nodes are very much enlarged, while 
 the more distal ones are in the form of tiny droplets, the type of 
 barbule thus resembling that of the Columbae very closely (pi. 25, 
 fig. 49/). In all species the down barbules are very long, as in 
 typical gallinaceous birds. 
 
 d) Relationships 
 
 The structure of the down alone is sufficient proof that the 
 tinamous are unquestionably far more closely allied to the Galli 
 than to any other birds, since it is difficult to believe that the 
 peculiar detachable rings at the nodes would be developed twice, by 
 separate paths of evolution. The remarkable similarity of the down 
 of some species to that of the Columbae can more readily be thought 
 of as parallel evolution, since it is a type which recurs again in the 
 Rhamphastidae, for instance, and is very easily derived from the 
 gallinaceous type of structure. The occurrence of these two types 
 of down in this single order, however, is suggestive of the fairly 
 close relationship of the Colurnbae and Galli. 
 
 The Crypturiformes show a remarkable number of specializations 
 of feather structure which are absolutely peculiar to them; in 
 fact, it may safely be said that the barbs of tinamous have the 
 most perfect and highly specialized interlocking mechanism found 
 anywhere in birds. This fact alone is enough to show the error 
 of grouping them with the Eatitae, or even anywhere near them. 
 They must undoubtedly be looked upon as a highly modified oifshoot 
 from the Galliformes, if the feather structure be taken into account 
 at all. 
 
 e) Summary 
 
 Crypturiformes are characterized as follows : 
 
 (1) Plumules sparse, and found only between contour feathers. 
 
 (2) Aftershaft present, often rudimentary, when well developed 
 with long shaft and distinct vanes. 
 
348 University of California Publications in Zoology C^ol. 13 
 
 (3) Distal barbules of inner vane of remiges with very short, 
 relatively broad base, with broad, lobate ventral teeth; pennulum 
 widest immediately beyond Eooklets, thence tapering in either direc- 
 tion; booklets excessively numerous, subequal, about 8 in, number, 
 only proximal ventral cilia developed, these moderate and more or 
 less appressed, dorsal cilia in shape, relative size, and angle of pro- 
 jection resembling the series of neural spines of dorsal vertebrae 
 of a dog. 
 
 (4) Proximal barbules of inner vane of remiges with base con- 
 cave toward distal side, the recurved dorsal portion replacing the 
 flange in other birds; pennula fused into a solid outer bar, lying 
 parallel with ramus. 
 
 (5) Distal barbules of outer vane differing from those of inner 
 only in reduction of dorsal cilia; proximal barbules on over nine- 
 tenths of barb like those of inner vane, with pennula fused into a 
 bar, but on short distal portion free, with well-developed hooked 
 barbicels as in Galli. 
 
 (6) Structure of body feathers a mere simplification of that of 
 remiges, pennula of proximals still fused. 
 
 (7) Down of two types, exactly like that of typical Oalli in 
 Calopezus and Nothocercus; closely resembling that of Columbae in 
 Tinamus and Nothura. 
 
 9. Order GRUIFORMES 
 Plates 26 and 27 
 Constituting a very heterogeneous group of birds whose relation- 
 ship has always been considered more or less doubtful, but affording 
 a convenient resting-place for many birds incertae sedis, the present 
 group shows so many variations among themselves in feather struc- 
 ture, and the different types included approximate so many other 
 groups, that practically no general epiphyologic characters which 
 are common to all can be described. The plumules in some are 
 generally distributed, in others sparse all over, in Otis confined to 
 the apteria. The aftershaft is present, rudimentary, or absent in 
 different species, but never, so far as I have been able to find, with 
 well-developed shaft and distinct vanes. 
 
 a) Grus canadensis 
 
 (1) Remex 
 Shaft about as wide as deep, very rectangular in cross-section 
 except for short distance distal to superior umbilicus; at superior 
 
191^] Chandler: Structure of Feathers 349 
 
 umbilicus very high, much higher than wide, and egg-shaped in 
 cross-section. Rami moderately broad at junction with shaft, pith 
 more than one cell thick, the ventral ridge rather narrow, less than 
 one-seventh total width of ramus, its ventral edge smooth. 
 
 Inner vane. — Distal barbules (pi. 26, fig. 50a) set about 28 per 
 millimeter. Base short and broad, about 0.24 mm. by 0.06 mm., 
 ventral teeth of moderate size, broad and lobate, their tips often 
 inconspicuously jagged, or very slightly bifurcated. Pennulum 
 considerably longer than base, rather broad, booklets 5 or 6, mod- 
 erately slender and progressively longer, but booklet cells so short, 
 and each successive booklet curved so much farther distal, that distal 
 ones reach no farther ventral than proximal ones; ventral cilia 
 slender, but slightly curved, all but first two or three appressed to 
 pennulum; more proximal dorsal barbules spinelike, especially first 
 two, more distal ones well developed, but slender, curving forward. 
 Proximal iarhules (pi. 26, fig. 50c) relatively large, set about 17 
 per millimeter, base about 0.73 mm. long by 0.07 wide, with 5 or 6 
 rather narrow, pointed, conspicuous ventral teeth; pennulum some- 
 what shorter than base but over half as long, flattened and mod- 
 erately broad proximally, its tip slender, with rudimentary barbicels. 
 
 Outer vane. — Distal barbules (pi. 26, fig. 50&) differing from 
 those of inner vane only in loss of proximal dorsal cilia, other 
 details of both base and pennulum similar ■ to those of inner vane. 
 Proximal barbules (pi. 26, fig. 50c), except at tip of barb, exactly 
 similar to those of inner vane. Towards tip of barb ventral teeth 
 become separated, and assume shape similar to those in Butorides 
 (pi. 20, fig. 21&), i. e., short curved barbicels, intermediate in form 
 between typical ventral teeth, as exemplified in more basal proximal 
 barbules (pi. 26, fig. 50c), and typical hooked ventral cilia, as in the 
 terminal proximal barbules of the outer vane in Ballus (pi. 26, 
 fig. 52c). 
 
 (2) Other Feathers 
 
 Bach feathers have distal barbules with rather elongate, slender 
 base, the ventral teeth with bifurcation or jaggedness of tips more 
 pronounced. Pennulum very long, 0.05 mm. or over, giving velvety 
 effect to feathers. Both dorsal and ventral cilia similar to those of 
 distal barbules of inner vane of remex. Proximals (pi. 26, fig. 50(f) 
 with slender base, about 0.65 mm. long by 0.05 wide, ventral teeth 
 reduced in size and number, and pennulum relatively shorter than 
 in remiges. 
 
 Scapular feathers especially modified as ornamental plumes, a 
 large part of outer vane, and some of inner vane, with discrete, 
 i. e., non-adhering, barbs, which curve outward. This condition is 
 accomplished merely by the breaking off of distal barbules imme- 
 diately beyond base, thus destroying interlocking apparatus. Tips 
 of proximal barbules also usually imperfect. 
 
 Breast feathers have structure of barbules on basal two-thirds 
 of middle barbs very similar to back feathers, except reduction of 
 all barbicels of distal barbules (pi. 26, fig. 50e) and shortening 
 of pennulum of proximals. On distal third a rather sudden transi- 
 tion occurs in both kinds of barbules to type shown in plate 26, 
 figure 50/. No differentiation between base and pennulum, the 
 
350 University of California Publications in Zoology [Vol. 13 
 
 barbule evenly tapering for whole length, dorsal edge with complete 
 and continuous series of flexules and dorsal cilia, ventral edge with 
 rather short, slender, more or less appressed ventral cilia. More 
 distal barbs have this structure for three-fourths of their length. 
 
 })) Other Types 
 
 The structure of the feathers in all species of Grus is probably 
 very similar, and there is a similar freeing of the barbs of the 
 terminal part of the scapular feathers in nearly all, if not all, of 
 the species. 
 
 In the Ballidae the structure of the feathers differs in some 
 important details, approaching more closely to that of the Limieolae. 
 In the remiges of Ballus oisoletiis, the proximal and distal barbules 
 are more numerous, being about 26 and 37 per millimeter respect- 
 ively. The distal barbules (pi. 26, fig. 52a.) have a relatively long 
 base, about 0.25 mm. long by 0.035 mm. wide, becoming very nar- 
 row proximal to the small, fingerlike ventral teeth, a condition 
 exactly similar to that in the Limieolae. The pennulum is rather 
 narrow except in the booklet region, the booklets 5 in number, and 
 slender, and the cilia, both ventral and dorsal, very similar to those 
 in the Limieolae (compare plate 26, figure 52a, with plate 28, figure 
 57a.) The proximal barbules (pi. 26, fig. 52&) have relatively 
 small bases, about 0.5 mm. long by 0.04 mm. wide, with ventral 
 teeth moderately developed, while the pennula are shorter than the 
 bases, and flattened. On the outer vane the distal barbules show 
 no especially interesting characters, but the proximal barbules 
 (pi. 26, fig. 52c) on the distal half of the barb have pennula longer 
 than the bases furnished with a highly developed series of ventral 
 cilia, of which the more proximal ones are hooked. In this char- 
 acter the rails differ from both the Limieolae and Gruidae. In 
 Cresicus the ventral cilia of the proximal barbules of the outer vane 
 are less hooked, while in Gallinula, although the pennulum is very 
 long and is sharply bent with respect to the base, as in Railus, the 
 ventral cilia, except two or three basal ones, are not developed. 
 
 In the body feathers of Baling obsoletus (also of Cresicus, Gal- 
 linula, and other species of Ballus) the structure of the feathers 
 is strikingly peculiar, even at the very base of the barbs. As shown 
 by plate 26, figures 52d, e, and /, the distal barbules, from base 
 to tip of the barb, change from a form with three weak booklets 
 and rudimentary flexules and cilia, to a form with no differen- 
 
^^^^^ Chandler: Structure of Feathers 351 
 
 tiation between base and pennulum, no ventral barbicels whatever, 
 and a series of very highly developed flexules and dorsal cilia, in 
 a continuous series after the booklets are lost. Plate 26, figures 
 52e and / shows the tardiness of the booklet cells to develop any 
 dorsal cilia. Plate 26, figures 52g and h show the method of trans- 
 formation of the proximal barbules, the distals and proximals being 
 exactly the same on the distal half of the barbs. 
 
 In the Aramidae, as typified by Aramus giganteus, the barbules 
 of the tack feathers closely resemble those of the back feathers of 
 the Coraciidae and Megapodidae in that in the distal barbules of 
 the undisturbed vanules the bases are twisted in such a way that 
 although at the junction with the ramus they stand in a vertical 
 plane, they lie in a horizontal plane for most of their length. The 
 distals also resemble somewhat the "peristeropode" Galli in the 
 curved form of the ventral cilia (compare plate 26, figure 51a, with 
 plate 24, figures 45a and 46a). The proximals (pi. 26, fig. 516) 
 also approach the condition in these birds in their elongate taper- 
 ing bases, and very short pennula. The breast feathers have bar- 
 bules which resemble those of rails in the great development of the 
 dorsal series of barbicels, consisting of both flexules and dorsal 
 ciUa, but are a little closer to those of the cranes in that they are 
 elongate, and possess a highly developed series of ventral as well 
 as dorsal cilia (pi. 26, fig. 51e). Plate 26, figures 51c and d show 
 the distal and proximal barbules respectively at the base of a barb 
 of a breast feather, showing the method of development of the 
 peculiar type shown in figure 51e of the same plate. 
 
 In Otis tarda, representing the Otididae, the remiges are char- 
 acterized by the remarkable width of the pithy part of the ramus. 
 On the inner vane, on barbs not over about 6 cm. long, the ramus, 
 near its base, is about 1.5 mm. wide, of which the ventral ridge 
 forms a very narrow edge, being less than 0.05 mm. wide. The 
 distal barbules of the remiges are peculiar in their being relatively 
 short, with stout bases and very large, lobate ventral teeth, and 
 exceedingly long booklets, usually seven in number. They are 
 devoid of conspicuous basal dorsal cilia even on the inner vane. 
 The proximal barbules (pi. 27, fig. 536) have a relatively large 
 base, with a rather stout, moderately long pennulum. The back 
 feathers are distinctly like those of galline birds in the structure 
 of their barbules, the distals having both base and pennulum shaped 
 as in the back feathers of Gallus, and the nuclei distinct in the 
 
352 University of California PuMications in Zoology [Vol. 13 
 
 pennular as well as basilar cells (compare plate 27, fi^re 53c with 
 plate 24, figure 47a). The proximal barbules, though resembling 
 the Galli in the diagonal line of conspicuous nuclei, differ in the 
 long, slender penhulum (pi. 27, fig. 53d). 
 
 Psophia viridis, representing the Psophiidae, has barbules which 
 come very close to the peristeropode Galli, as will be seen by com- 
 paring plate 27, figures 54a, i, c and d with the figures of barbules 
 of Megapodius and Penelope (plate 24, figures 45a and & and 46a). 
 The iridescent golden green of a part of the outer vane of the 
 coverts is produced by refrangent barbules which are completely 
 metamorphosed to serve in color production. In form, on both 
 distal and proximal vanule, they are somewhat shortened, with no 
 barbicels whatever, as shown in plate 27, figure 54e. A short dis- 
 tance from their junction with the ramus they are bent suddenly 
 outward, and from this point, which is the widest, they taper 
 evenly to the tip. Both upper and lower surfaces refract light. 
 
 Eurypyga helias, representing the Eurypygidae, also has bar- 
 bules which show an approximation to the type found in perister- 
 opode Galli, but show a more striking similarity to the Ardeae. 
 As shown in plate 27, -figures 55a and c, the general form of the 
 distal barbules is remarkably like that of Ardea (compare plate 20, 
 figs. 20a and c), but the size and form of the ventral teeth and 
 ventral cilia are nearer to the megapodes. The proximal barbules 
 (pi. 27, fig. 55d) show a still closer similarity to the Ardeae in 
 the form of the base and in the slender filamentous pennulum, and 
 in the fact that no ventral cilia are developed on the proximal 
 barbules of the distal part of the barbs of the outer vane (com- 
 pare plate 27, figures 556 and d, with plate 20, figures 20& and d). 
 
 Cariama cristata, of the family Cariamidae, very much re- 
 sembles Eurypyga in the details of its feather structure, as shown 
 by plate 27, figures 56a and c, representing a distal and proximal 
 barbule respectively from a back feather. 
 
 c) Down 
 
 In Grus canadensis the down barbules are from 1.5 to 3.5 mm. 
 long, in the form of almost unmodified threads, which, however, 
 under high magnification show small prongs at the nodes, usually 
 two of unequal size, and appressed and inconspicuous. The barbules 
 show a tendency to scuff off, or become chafed, so that small frag- 
 ments may frequently be seen hanging from them. 
 
1916] Chandler: Structure of Feathers 353 
 
 In the Rallidae the down barbules are short, stout, and deeply 
 pigmented, with short internodes. The pigment is present chiefly 
 in the distal part of the internodes, the minute prongs and the 
 proximal part of the internodes being more or less unpigmented. 
 In Rallus obsoletus (pi. 36, fig. 107) the internodes reach a length 
 of about 0.035 mm. In Gallinula the nodes are farther apart, 
 while in Cresicus they are nearer together. In Psophia the down 
 is black, as in Ballus, but the nodes are indistinct, and the pig- 
 ment almost uniformly distributed. Eurypya (pi. 36, fig. 106) has 
 barbules which are more elongate and slender, very similar to that 
 of the ardeid forms which have dark down, e. g., Botaurus (pi. 34, 
 fig. 100). Aramus agrees, with the cranes in the structure of its 
 down, except that the barbules are not so slender. Cariama has 
 down which is very long and filamentous, with enlarged nodes in 
 all except the more basal barbules. In general the structure seems 
 to be more like that of the Ardeae than like that of ^ny other group. 
 The down of Otis in the general form of the barb and vanules and 
 length of barbules, is of galline type, but the minute structure is 
 very different, the nodes being entirely undeveloped, and the bar- 
 bules being merely long, slender, unmodified threads. 
 
 d) Relationships 
 
 As previously stated, the Gruiformes include a rather heterog- 
 eneous assemblage of birds which show affinities to a number of 
 other groups, but are so generalized in some respects and special- 
 ized in others as to be very difficult to classify. The rails show a 
 striking affinity, as far as their feather structure is concerned, to 
 the Laro-limicolae. The cranes, on the other hand, differ from the 
 Laro-limicolae, but agree with the Ciconiae, in the form of the 
 proximal barbules of the outer vane of the remiges, which have 
 no ventral cilia, while they agree with the Laro-limicolae, but differ 
 from the Ciconiae, in possessing flexules on the breast feathers. 
 Aramus, in the structure of its breast feathers is more or less inter- 
 mediate between the rails and the cranes, while in its back feathers 
 it approaches the peristeropode Galli. Psophia also shows char- 
 acters which are reminiscent of the megapodes and curassows, while 
 Otis comes closer to the aleetoropode type in the form of the bar- 
 bules and barbieels. Eurypyga shows so many ardeid characters in 
 the structure of its feathers that it strongly suggests its affiliation 
 
354 University cf California Publications in Zoology [Vol. 13 
 
 with the herons instead of with the cranes. Cariama is undoubtedly 
 nearer to Eurypyga than to any other forms. 
 
 In general it seems best to consider the Gruidae, Aramidae, and 
 Rallidae as offshots from a primitive stem leading to the Laro- 
 limicolae, while the Otididae, Psophiidae, and possibly the Ara- 
 midae, are more probably early offshots from the stem leading to 
 the Columbae and Galli. The Burypygidae, and possibly the Caria- 
 midae, are almost certainly of ardeid derivation. 
 
 e) Summary 
 
 (1) Distribution of plumules variable, uniformly distributed, 
 or sparse all over, confined to apteria in Otis. 
 
 (2) Aftershaft present, rudimentary, or absent. 
 
 (3) Distal barbules in dififerent forms showing affinities to the 
 Laro-limicolae, Galli and Ardeae; proximal barbules with incon- 
 spicuous teeth, pennulum very different in different forms, some- 
 times with cilia in outer vane, sometimes without. 
 
 (4) Breast feathers in Gruidae, Aramidae, and Rallidae with 
 flexules on barbules, but of galline type in Psophiidae and Otididae, 
 and ardeid in Eurypygidae and Cariamidae. 
 
 (5) Down barbules medium or long, smoothly filamentous, or 
 with ineonspieuoiis prongs at the nodes, or pigmented, with the 
 nodes slightly enlarged. 
 
 10. Order CHARADRIIFORMES 
 Plates 28-29 
 Including a very large assemblage of birds which in general 
 appearance seem to have little or nothing in common, the Chara- 
 driiformes are nevertheless joined together into a more or less 
 natural group by numerous more or less intermediate species which 
 bridge over the gaps separating the more widely divergent forms. 
 It is divisible into two main suborders, the Laro-limieolae and 
 Pteroclo-columbae, which will be separately treated. 
 
 Suborder Lako-limicolae 
 
 Plate 28 
 This suborder includes three groups of birds, the Limicolae, the 
 Lari, and the Alcae, including the plovers and their allies, the gull- 
 like birds, and the auks and murres respectively. They are all 
 characterized by the uniform, though often sparse (especially in the 
 
1^^^] Chandler: Structure of Feathers 355 
 
 Limicolae) distribution of down, and the presence of an aftershaft, 
 usually well-developed, but in a few eases very small. As was done 
 by Gradow (1891), the Limicolae are regarded as the center of the 
 entire charadriiform group, since in the structure of their feathers 
 as well as in other regards, they are neither the least nor the most 
 specialized. It is for this reason that a limicoline bird was selected 
 for special description. 
 
 a) Numenius americanus 
 
 (1) Remex 
 
 Calamus and basal portion of shaft rather slender, much deeper 
 than wide, the calamus relatively long, the shaft if anything deeper 
 than wide for most of length, with narrow ventral groove and dis- 
 tinct striations on side at junction of barbs. Rami relatively deep, 
 the ventral ridge moderately developed, with a smooth ventral edge 
 in both inner and outer vanes. Distal and proximal vanules with 
 30 and 20 barbules per millimeter respectively. 
 
 Inner vane. — Distal' harhules with relatively broad base (0.28 
 by 0.056 mm.), subnuclear area especially broad and filmlike, its 
 ventral contour line conspiculously curving in proximal to ventral 
 teeth (pi. 28, fig. 57a). Ventral teeth remarkably small and in- 
 conspicuous, both short and narrow. Pennulum slightly longer 
 than base; booklets 5 or 6 in number, short, moderately slender, 
 the distal ones not conspicuously longer than proximal ones, the 
 booklet cells not being short and crowded; ventral cilia developed 
 on whole length of pennulum, proximal 2 or 3 short, the more 
 distal ones longer, but appressed to barbule for part of their length 
 (see figure) ; two proximal dorsal barbules stout, spiny, best de- 
 scribed as earlike; more distal ones decreasing in size, and rather 
 rudimentary. Proximal barbules (pi. 28, fig. 576) with very slender 
 base, about 0.5 by 0.04 mm., ventral teeth short, blunt and in- 
 conspicuous; pennulum much shorter than base, moderately stout 
 proximally, tapering to fine point. 
 
 Outer vane. — Distal barbules with bases considerably longer and 
 more slender, about 0.32 by 0.04 mm., the subnuclear area being 
 the part especially reduced (pi. 28, fig. 57c). Ventral teeth some- 
 what longer but even more slender than on inner vane. Hooklets 
 5 or 6, longer than on inner vane, almost all of equal length. 
 Series of ventral cilia complete, these barbicels of moderate length, 
 slightly curved, and subequal. Dorsal cilia absent except near tip 
 where a few short rudimentary ones are developed. Proximal bar- 
 bules for over three-fourths of length of barb similar to those of 
 inner vane, but on terminal part of barb ventral teeth proliferat- 
 ing and developing into straight, unhooked ventral cilia (pi. 28, 
 fig. 57d). ^ 
 
 (2) Other Feathers 
 
 Back feathers. — Structure of distal barbules (pi. 28, fig. 57e) 
 much like that of those of outer vane of remiges, but base of some- 
 
356 University of California Publications in Zoology [Vol. 13 
 
 what different shape, as shown in figure, booklets reduced in num- 
 ber and strength, pennulum considerably longer, ventral cilia more 
 curved and more nearly subequal, and dorsal cilia better developed, 
 short and spinelike. Proximal barbules with tapering base and 
 relatively short, stout pennulum, less than half length of base. 
 
 Breast feathers similar to those of back in greater part of barbs, 
 but less developed, bases of barbules narrower, booklets weaker, and 
 weaker ventral cilia. On distal third of barb, barbules (pi. 28, fig. 
 57/) have a series of highly developed flexules, less curved ventral 
 cilia also being present. These barbules are then not unlike the outer 
 barbules on barbs of breast feathers of Gavia (pi. 16, figs. 8e, 8/). 
 The distal and proximal harbules on the distal third of the barb 
 are alike except that the proximals are slightly longer. 
 
 h) Other Types 
 
 Many species of Charadriidae, including nearly all the genera 
 represented in "Western North America, were examined, and all of 
 them were found to be extremely similar in their general feather 
 structure to that of Numenius. A barbule from the distal third 
 of a breast feather of Phalaropus fulicarius is represented in plate 
 28, figure 59ft, and a comparison with figure 57e of the same plate 
 shows how similar they are, though the stouter form of the fiexules 
 and less conspicuous ventral cilia of Phalaropus is reminiscent of 
 the rails. 
 
 In Parra spinosa, or jaeana, representing the Parridae, there 
 is a little modification of the charadriid type in the back feathers, 
 those on the basal half of the barb (pi. 28, fig. 58ft) being slightly 
 more elongate and slender, while on the distal half fiexules are 
 developed very much as in the breast feathers, but the barbule is 
 not so shortened (pi. 27, fig. 58&). 
 
 In Oedicnemus the remiges are very much like those of Chara- 
 driids in structure, but the breast feathers differ in that flexules 
 are very poorly if at all developed. 
 
 Cursorius gallicus, representing the Glareolidae, seems to show 
 in its feather structure a closer likeness to the Ardeae than to the 
 Limicolae. As shown by plate 28, figures 60ft and i, both distal 
 and proximal barbules are decidedly like those of the herons. The 
 terminal distal barbules of the breast feathers differ widely from 
 those of all other members of this suborder as shown by plate 28, 
 figure 60c, more closely approximating the herons or storks in the 
 short blunt barbieels. 
 
 The Laridae, representing the second group, composed of strong- 
 
1916] Chandler: Structure of Feathers 357 
 
 flying fish-eaters, differ so little from typical limicoline birds that 
 a special description of their feathers would be superfluous here. 
 Comparison on plate 28 of figures 61a, b, c, d and e, with figures 
 57a, 6, c, d and e respectively, will make the similarity strikingly 
 clear. It is interesting to note that the bluish-gray colors of gulls 
 are produced by an uneven distribution of pigment in the barbules, 
 as shown by the figures of Larus occidentalis (pi. 28, figs. 61a, d). 
 In lighter-colored gulls, such as Larus argentatus, the light spaces 
 between the dark bars in the bases of the barbules are more ex- 
 tensive. Terns and jaegers have an even distribution of pigment 
 in the barbules. In the former, as exemplified by Sterna maxima, 
 the outer vane of the remiges has a hoary appearance due to the 
 great length of the pennula of the distal barbules, which have ex- 
 ceedingly numerous and slender ventral cilia (pi. 28, fig. 62a). 
 
 The auks, guillemots, murres, etc., representing the Alcidae, 
 seem, according to their feather structure, to form a sort of con- 
 necting link between the Colymbiformes and Laridae. The resem- 
 blance of the structure of the remiges to that of both the gulls 
 and grebes is well brought out by a comparison of plate 28, figures 
 63a, 6 and c, representing barbules of the remiges of Vria troille, 
 with figures 61a, h and c of the same plate on the one hand, and 
 plate 16, figures 9a, 6 and c on the other. 
 
 The structure of the breast feathers is remarkably similar to 
 that of grebes and Sphenisciformes. The more basal distal barbules 
 (pi. 28, fig. 63d) could very readily be mistaken for those of Aech- 
 mophorus (pi. 16, fig. 9e). The middle part of the barb is fur- 
 nished with twisted barbules and is exactly similar to that shown 
 in plate 16, figure 9h, while on the more distal third the barbules 
 (pi. 28, figs. 63e, 63/) are strikingly similar to those developed in 
 the outer portion of the barbs of breast feathers of loons (pi. 16, 
 figs. 8e, 8/). 
 
 c) Down 
 
 In the Charadriidae the down barbules are quite different in 
 different forms, usually of rather moderate length, i. e., from 1 to 
 2 mm. long, sometimes pigmented. The nodes are always swollen 
 and . more or less distinct, in pigmented types often very distinct 
 with the pigment present in it as a dark spot, almost as in pas- 
 serine birds (pi. 37, fig. 114). In Cursorius the barbules are of 
 this type, and unusually dense, there being as many as 70 barbules 
 per millimeter on each side. 
 
358 University of California Publications in Zoology [Vol. 13 
 
 In the Laridae and Alcidae the down barbules are shorter, with 
 indistinct nodes on the proximal portion, and well-developed prongs 
 distally, thus very closely resembling the Colymbiformes. 
 
 d) Relationships 
 
 The unquestionable likeness of the structure of feathers in the 
 Alcidae to that in the Colymbiformes very strongly suggests the 
 close relationship between them. The relation of the Laridae to 
 the Alcidae, and of the Limieolae to the Laridae, is just as plainly 
 indicated, and we have a very clear and distinct path of evolution 
 suggested by these groups. Relationship to the Gruidae is also 
 suggested and it is probable that the latter represent an early off- 
 shoot from the limicoline stem. The Limieolae, in all respects, show 
 higher specialization than the other forms included in the suborder. 
 
 e) Summary 
 
 The Laro-limicolae are characterized as follows: 
 
 (1) Plumules evenly distributed, though sometimes sparse in the 
 Limieolae. 
 
 (2) Aftershaft present, sometimes small. 
 
 (3) Distal barbules of remiges with broad subnuclear area on 
 base, very small ventral teeth, rather short, subequal booklets, a series 
 of subequal, somewhat curved ventral cilia, and on inner vane two 
 proximal dorsal cilia more or less earlike. 
 
 (4) Proximal barbules with very slender base, inconspicuous 
 ventral teeth, and pennulum little if any over half length of base; 
 proximals of outer vane with imperfectly developed ventral cilia. 
 
 (5) Distal barbules of back feathers with a long series of well 
 developed, curved, ventral cilia. 
 
 (6) Breast feathers with barbules on outer portion of barbs with 
 flexules. 
 
 (7) Down resembling that of Colymbiformes in Laridae and 
 Alcidae, the barbules with enlarged nodes and more or less pig- 
 mented in Limieolae. 
 
 Suborder Pteroclo-columbab 
 Plate 29 
 This suborder includes two rather distinct and well-defined 
 groups, the Columbae with the pigeons and doves on the one hand. 
 
1916] Chandler: Structure of Feathers 359 
 
 and the Pterocles, with the sand-grouse, on the other. The group 
 is characterized by the great reduction of the plumules and the 
 aftershaft. In the Columbae, which are the most specialized, in 
 this regard, the plumules are entirely absent, and the aftershaft 
 is absent or rudimentary. In the Pterocles, the plumules are evenly 
 distributed, and the aftershaft is present, though small. 
 
 a) Colwniba livia 
 (1) Remex 
 
 Shaft much deeper than broad at superior umbilicus, for most 
 of length about as broad as wide, with a narrow, median ventral 
 groove, and striations on side, as in Laro-limicolae. Rami narrow, 
 the ventral ridge inconspicuous. Tanules with very closely set bar- 
 bules, the distals 45 per millimeter, the proximals about 35. 
 
 Inner vane. — Distal iarhules (pi. 29, fig. 64a) with short wide 
 base, about 0.18 mm. long by 0.037 mm. wide, the ventral teeth 
 very broad and triangular; nuclei in a strikingly diagonal line, 
 even more so than in Galli. Pennulum little if any longer than 
 base; more or less arched dorsad; booklets small and slender, 
 usually 6 in number, proximal 3 short, distal 3 progressively in- 
 creasing in length; ventral cilia short, curved, subequal, well sep- 
 arated from each other; dorsal cilia straight, spinelike, shorter 
 than ventral ones, the proximal two not especially modified. Prox- 
 imal barbules (pi. 29, fig. 646) relatively very short and broad, 
 the base about 0.4 mm. long by 0.056 wide, with nuclei in conspicu- 
 ously diagonal line as in distals. Ventral teeth usually 5, rather 
 narrow and pointed, not elongated, but always evident. Pennulum 
 very slender and filamentous, about half length of base. 
 
 Outer vane. — Distal harbules (pi. 29, fig. 64c) much like those 
 of inner vane, but, as shown by figure, whole barbule arched dorsad, 
 instead of only the pennulum. Pennulum about as long as base, 
 rather broad in lateral view. Hooklets 6 or 7 in number, small 
 and slender. Ventral cilia as in distal barbules of inner vane, but 
 a little shorter, dorsal cilia developed towards tip, but short and 
 spinelike. Proximal barbules on basal portion of barbs similar to 
 those of inner vane, towards tip ventral teeth become separated 
 from one another, increase in number, sometimes to 7 or 8, and 
 assume a stout curved form, intermediate between typical ventral 
 teeth and typical cilia. 
 
 (2) other Feathers 
 
 In Zenaidura macroura, used as type for description of hack 
 feathers, latter have distal barbules much like outer vane of remex, 
 and proximals more like inner vane of remex. Distal barbules 
 with short, broad base, broad ventral teeth, and relatively long 
 pennulum, with short, blunt, ventral cilia (pi. 29, fig. 65a). Hook- 
 lets characterized by presence of one or two prongs or horns on 
 their distal side, as shown in the greatly magnified booklet region 
 of a distal barbule from a covert feather of Columba fasciata (pi. 
 
360 University of California Publications in Zoology [Vol. 13 
 
 29, fig. 67a). Proximal barbules differ from those of remiges in 
 base being relatively slender, with inconspicuous ventral teeth, the 
 pennulum being extremely slender and filamentous, nearly as long 
 as base. 
 
 Breast feathers, as exemplified by Melopelia asiatica, with both 
 kinds of barbules characterized by elongation of bases, which are 
 relatively more slender than in back feathers, and very great 
 elongation of the slender threadlike pennula. Distal barbules (pi. 
 29, fig. 66&) have slender base, all barbieels reduced, and pennu- 
 lum two or three times length of base on more proximal part of 
 vanule, shorter than base on distal part of vanule. Proximal bar- 
 bules (pi. 29, fig. 66c) with similarly elongated base and extremely 
 long pennulum, several times length of base on proximal part of 
 vanule, about equal to it on distal part. 
 
 h) Other Types 
 
 In the majority of the Columbidae the remiges have a structure 
 very closely similar to that described above for Columba livia. A 
 very unusual and probably recent departure from the ordinary 
 type is to be found in the forked primaries of Drepanoptila, in 
 which the entire feather plate is double on the terminal portion. 
 
 Goura coronata differs widely from the other Columbidae in 
 the character of the proximal dorsal cilia of the distal barbules of 
 the inner vane (pi. 29, fig. 70a), which are large and specialized 
 as stout, lobelike projections as in herons and vultures. In other 
 respects the distal barbules, and in all respects the proximal bar- 
 bules, resemble those of typical Columbidae. The coverts, scapulars, 
 and back feathers undergo very little modification in the different 
 genera except for production of color. (See plate 29, figure 66a, 
 covert from Melopelia; figure 68a, covert from Macropygia; figure 
 69a, covert from Osmotreron). The breast feathers also differ but 
 slightly in different groups. Even in Goura coronata, which has 
 feathers differing most widely from the type of any species in the 
 family, the breast feathers are remarkably similar to those of other 
 columbids (pi. 29, figs. 70c, IQd). The barbules on the loose-vaned 
 crown feathers of Goura (pi. 29, fig. 70e) have lost their pennula 
 and the bases are cigar-shaped. 
 
 In the Pteroclidae, exemplified by Pteroclis arenariu^, the distal 
 and proximal barbules of the inner vane (pi. 29, fig. 71a, 71c) are 
 distinctly of typical columbid type, but those of the outer vane 
 differ in having very short pennular cells with long, slender ventral 
 cilia and very short, knoblike dorsal cilia. The scapular feathers 
 have the peculiarities of the pennulum of the distal barbules still 
 
^^^^] Chandler: Structure of Feathers 361 
 
 more emphasized, the cells being exceedingly short, the crowded 
 ventral cilia being long and slender, the dorsal ones in close juxta- 
 position to each other, and of a peculiar blunt, heavy form (pi. 29, 
 fig. 716). The proximal barbules (pi. 29, fig. 71c) are similar to 
 those of the inner vane of the remiges. The barbules of the breast 
 feathers resemble those of the scapulars but are weaker and less 
 perfectly developed. 
 
 c) Down 
 
 The down barbules of typical Columbae are long, as in galli- 
 naceous birds, frequently 3 or 4 mm. in length. On the basal part 
 of the pennula there are a number of very large, expanded, and 
 conspicuous nodes, usually from 3 to 8 of them of full size, then a 
 similar number of smaller and less conspicuous ones, decreasing 
 in size until they almost entirely disappear, the whole distal por- 
 tion of the pennulum being smoothly filamentous or with very minute 
 swollen nodes (pi. 36, fig. 109). Very similar down barbules are 
 found in Tinamus and Nothocercus among the Crypturiformes. 
 
 This structure of down has been found in all species of Colum- 
 bidae which have been examined except Goura coronata. It has 
 been found in Columba, Melopelia, Zenaidura, Golumbigallina, Did- 
 unculus, Macropygia and Osmotreron. In Goura the down bar- 
 bules are shorter than in other Columbidae, not over 2 mm. long, 
 and are smoothly filamentous with the nodes not swollen at all, 
 although the junction of the cells is indicated by the uneven distri- 
 bution of pigment, the latter being located in the distal portion of 
 the internodes. Nitzsch (1867, pi. 1, fig. 25) figures the basal 
 portion of a down barbule from a turtle dove. 
 
 In Pteroclis the down barbules are between 1 and 2 mm. long, 
 very slender and delicate, with no indications whatever of nodes, 
 except towards the tip where rather large prongs are developed. 
 
 d) Color Modifications 
 
 There are a number of special color modifications in the Colum- 
 bidae which are worthy of special mention. The blue-grays, rang- 
 ing from light pearl gray in the breast of Melopelia asiastica to a 
 slate blue in Goura, are very common in birds of this group, as 
 in the Laridae, and are produced in the same way, namely, by a 
 segregation of the black pigment into transverse bars (pi. 29, figs. 
 64c, 66a-c, and 70c-e) the lighter colors produced by barbules with 
 
362 University of California Publications in Zoology [Vol. 13 
 
 wider light interspaces, as for instance, in the breast of Ooura (pi. 
 29, fig. 666-c). It is very unusual, in parti-colored barbules, for 
 any pigment to be present ventral to the row of nuclei. A beau- 
 tiful, delicate olive color is produced in the coverts of Osmotreron 
 by distal barbules in which the base is bluish gray, due to cross- 
 bars of black pigment, while the entire pennulum contains a deep 
 lemon-yellow pigment (pi. 29, fig. 69a). The iridescent neck feathers 
 of Columba, ZenaAdura, and other genera are produced by 
 barbules from which the pennula are broken off, the reflecting sur- 
 face being the large recurved flange. The barbule drawn on plate 
 29, figure 576, from a neck feather of Columba fasciata is seen in 
 side view, and nothing of this portion except the tips of the ventral 
 teeth shows as the barbules lie in the vanule, the result being that 
 these feathers are not iridescent on the ventral side (see also Strong 
 1903&). 
 
 e) Relationships 
 
 The Pteroclo-columbae, according to their feather structure, 
 show more similarities to the gallinaceous birds than to any other 
 group. The shape of both distal and proximal barbules, and the 
 specialized nature of the down, are all points of striking likeness. 
 The occurrence in the tinamous, which are undoubtedly a special- 
 ized group of gallinaceous birds, of both the columbid and galline 
 type of down, might be considered a further bond of union between 
 the two latter groups. They show the same afiiliation to some of 
 the gruiform birds as do the gallinaceous birds, and like the latter 
 show some affinity to the Cuculiformes, especially in the presence 
 of prongs on the booklets of the distal barbules of back and breast 
 feathers. The relation of the Pteroclo-columbae to the Laro-limi- 
 colae, if there is any close relationship, is not shown at all in the 
 structure of the feathers. The Pterocles show a number of differ- 
 ences from the Columbae in feather structure, which are probably 
 specializations of their own, and do not show closer approximation 
 to any other group. 
 
 f) Summary 
 
 (1) Plumules sparse or absent. 
 
 (2) Aftershaft rudimentary or absent. 
 
 (3) Distal barbules of remiges with short, broad base, nuclei in 
 strikingly diagonal line, ventral teeth broad and triangular; pen- 
 
1916] Chandler: Structure of Feathers 363 
 
 nulum with 5 or 6 rather small hooklets, a series of short, curved 
 ventral cilia, more slender in Pteroclis, and in the inner vane a 
 series of small, spinelike dorsal cilia, the proximal ones of which 
 are especially modified only in Goura. 
 
 (4) Proximal barbules of inner vane of remiges with short, stout 
 base, moderate, pointed ventral teeth, and very slender pennulum, 
 shorter than base. 
 
 (5) Proximals of outer vane, towards tip of shaft, with ventral 
 teeth becoming somewhat cilia-like in form, but a well-formed series 
 of ventral cilia never developed. 
 
 (6) Structure of coverts, scapulars, and back feathers much 
 like that of outer vane of remex, except that hooklets of distal 
 barbules frequently have prongs or spines . on the edge nearer the 
 tip of the barbule ; Pteroclis differs in having distal barbules of scapu- 
 lars with more specialized barbicels than in remex. 
 
 (7) Breast feathers with similar structure, but pennula very 
 elongated, no flexules ever developed. 
 
 (8) Down barbules in Pteroclis and Goura moderately long, 
 without enlarged nodes; in all other species examined, the nodes 
 on proximal part of pennula very much swollen and expanded, 
 and very conspicuous, terminal portion of barb smoothly fila- 
 mentous, or with very minute prongs. 
 
 11. Order CUCULIFORMES 
 
 This order, composed of two suborders, the Cuculi, including 
 the cuckoos and plaintain-eaters, and the Psittaci, including the 
 parrots, forms a sort of connecting link between the ground birds 
 on the one hand, and the coraciiform and passerine birds on the 
 other. Though the cuckoos and parrots are undoubtedly related, 
 their being grouped together in a separate order has been open to 
 considerable question. In the Cuculi the plumules are very sparse, 
 and restricted to the apteria, and the aftershaft is absent or Rudi- 
 mentary in the Cuculidae, present in the Musophagidae ; in the 
 Psittaci the plumules are well developed over the whole body, and 
 the aftershaft is large, but with a short shaft and no distinct vanes. 
 
 a) Coccyzus americanus 
 (1) Bemex 
 
 Calamus very small, and of smaller caliber than shaft. Shaft 
 at least as wide as deep at superior umbilicus, the widest part of 
 
364 University of California Publications in Zoology [Vol. 13 
 
 quill being a short distance distad of this point; ventral groove 
 practically absent; striations on sides at junction of barbs distinct. 
 Pith of ramus only one cell in thickness, the ventral ridge rela- 
 tively wide, its ventral edge smooth in barbs of both vanes. Vanules 
 rather open, the barbules set about 28 per millimeter on both distal 
 and proximal ones, although both are composed of rather narrow 
 barbules. 
 
 Inner vane. — Distal bariules (pi. 30, fig. 72a) with relatively 
 very long and narrow base, about 0.28 by 0.035 mm., the ventral 
 contour sinuate, i. e., broad on proximal half, then becoming nar- 
 rower in an even curve just proximal to the ventral teeth, which 
 curve slightly outward again; flange very well developed; ventral 
 teeth very small and slender. Pennulum a little shorter than base, 
 all its cells, including those bearing booklets, not short or crowded 
 together; the booklets, about 5 in number, small, very frequently 
 with prongs as in Columbae, and hanging straight ventrally, i. e., 
 not curved forward ais when booklet cells are crowded; ventral 
 cilia short and appressed to pennulum, the dorsal cilia more promi- 
 nent, proximal two large and lobate, more distal ones short and 
 spinelike. Proximal barbules (pi. 30, fig. 726) short and slender 
 relative to distals; base about 0.4 by 0.035 mm., ventral teeth short, 
 blunt, inconspicuous, pennulum somewhat shorter than base and 
 rather stout, sometimes with minute, rudimentary barbicels. 
 
 Outer Vame. — Distal barbules (pi. 30, fig. 72c) with shorter 
 and relatively broader and less sinuate base than those of inner 
 vane; booklets 5 or 6 in number, cilia as in distal barbules of inner 
 vane except absence of proximal dorsal ones. Proximal barbules 
 on basal half or more of barbs like those of inner vane, on more 
 distal part with a well-developed series of rather short cilia, middle 
 ones of which are hooked (pi. 30, fig. 72d). 
 
 (2) other Feathers 
 
 Back feathers with distal barbules much like those of outer 
 vane of remex except that their bases are much more slender, 
 about 0.28 by 0.025 mm., the booklets usually 4 in number, small, 
 but progressively increasing in length more than in remex, and 
 frequently with prongs; cilia small. Proximal barbules even more 
 slender than in , remex, the base about 0.4 by 0.28 mm. Ventral 
 teeth 2 or 3 in number, very inconspicuous, pennulum shorter than 
 base. 
 
 Breast feathers almost exactly same as back feathers in struc- 
 ture, but barbules weaker and still more slender (pi. 30, figs. 
 72e, /). 
 
 b) Other Types 
 
 The structure of the feathers of all the Cuculidae are very sim- 
 ilar to the type described as far as examined {Coccyzus, Cuculus, 
 Geococcyz, and Eudynamis), except where there are modifications 
 for color production. 
 
 The Musophagidae do not differ in any important ways from the 
 
1816] Chandler: Structure of Feathers 365 
 
 Cueulidae in the structure of their feathers, although, as will be 
 shown later, they have a peculiar pigmentation. 
 
 The Psittaci differ from the Cuculi to a very slight degree. The 
 barbules of the remiges, as exemplified by Cacatua galerita (pi. 30, 
 figs. 74:a^d), differ in no important details except the character 
 of the proximal barbules of the distal part of the outer vane, 
 where, instead of the pennulum being long with well-developed 
 hooked cilia as in Coccyzus (pi. 30, fig. 72d), the base is shortened, 
 the pennulum also short, and the ventral teeth somewhat increased 
 in number, separated, and in the form of short, more or less tri- 
 angular barbicels (pi. 30, fig. 74d). 
 
 Melopsittacus differs in having distal barbules of the outer vane 
 (pi. 30, fig. 75a) with rather stout bases and short pennula with 
 crowded cells, the booklets being long and closely approximated to 
 one another and the ventral cilia also rather crowded. The proximal 
 barbules undergo the same sort of modification on the outer part of 
 the barb as in Cacatua (pi. 30, fig. 756). 
 
 The body feathers of the Psittaci resemble those of the Cuculi, 
 but differ in that the barbicels are all less highly developed (pi. 30, 
 figs. 76a., 77a, 77&). In breast feathers, frequently, practically 
 all the barbicels are rudimentary or absent, except two or three 
 rather conspicuous booklets on the distal barbules (pi. 30, figs. 77a, 
 776). 
 
 c) Down 
 
 The down in Coccyzus, Cuculus, and Eudynamis resembles that 
 of the typical Columbidae rather closely, but can readily be dis- 
 tinguished. The barbules are long (2 mm. more or less) and very 
 slender, and the nodes are in the form of round droplets some- 
 what resembling the viscid droplets on a spider's thread. Those 
 near the base are large, while more distally they are very minute, 
 but still maintain their globular form. In pigmented barbules 
 the pigment is localized in a spot just back of the globular node. 
 The internodes are exceedingly long and slender, in Eiodynamis 
 honorata sometimes 0.1 mm. long and less than 0.002 mm. in dia- 
 meter. In Geococcyx the globular nodes are not in evidence, the 
 cells being merely gradually enlarged, and pigmented on their distal 
 half. 
 
 The down of the Psittaci very closely resembles that of the typical 
 cuckoos, having more or less globular nodes which are rather large 
 
366 University of California Publications in Zoology [Vol. 13 
 
 proximally, but very minute distally. In the aftershaft the nodes are 
 not quite so globular, and show rudiments of prongs. In the majority 
 of the Psittaci, the nodes are shaped more like the fruit of a 
 eucalyptus tree, and have the pigment in them instead of proximal 
 to them, thus closely approaching some of the coraciiform birds. 
 The nodes in the Psittaci are somewhat closer together than in the 
 Cuculi, there being usually 15 or more per millimeter, instead of 10 
 or 12 as in the Cuculi. 
 
 d) Color Modifications 
 
 There are a number of interesting color modifications in this 
 order. The steel-blue feathers of Eudynamis honorata have a warm 
 brown pigment, and are highly reflective, the blue color being prob- 
 ably due, at least in part, to the selective transmission and reflec- 
 tion of the pigment. There are raised ridges at the junction of 
 the cells of the bases of both distal and proximal barbules, and also 
 on the broad pennula of the latter. A similar modiflcation is to 
 be found in the glossy green feathers of Geococcyx califomianus. 
 In this case the green color seems to be primarily produced by the 
 reflective bases of the distal barbules, but the pennula of the prox- 
 imals are conspicuously broadened, with distinct raised ridges at 
 the junction of the cells (pi. 30, fig. 73a). 
 
 In the Musophagidae, represented by Turacus corythaix, the 
 barbules of the remiges owe their deep purplish crimson color to 
 an evenly distributed pigment known as turacin, which, according 
 to Church (1893), is somewhat soluble in water and contains a 
 considerable percent of copper. By transmitted light this pigment 
 in thin layers, e. g., in a single barbule, is of a distinct green 
 color, but in thicker layers, as where the flange overlaps the rest 
 of the base, or where two barbules lie on top of each other, it is 
 a deep red. It is, therefore, a fluorescent color, with color proper- 
 ties somewhat similar to those of eosin. The dull glossy green and 
 delicately lined feathers of the back are produced by barbs in 
 which the barbules are evenly pigmented with a brownish color and 
 are green by refraction, while the rami are whitish. 
 
 In the Psittaci a number of interesting color "modifications are 
 found. Yellows, reds, and oranges are produced by a pigment 
 evenly distributed in both rami and barbules. Green, blue, and 
 purple are produced by a refraction from the dorsal ridges of the 
 rami, modified by pigmentation in the barbules, e. g., the soft deep 
 
1916] Chandler: Structure of Feathers 367 
 
 green of many species is produced by a brilliant green structural 
 color in the ramus, accompanied by a brown pigmentation in the 
 barbules, the depth and tone of the green varying with the shade 
 and amount of brown pigment in the barbules. The bright emerald 
 green of Melopsittacus is produced by green or blue rami, with 
 lemon-yellow barbules, and the yellow olive-green of Tanygnathus 
 lucionensis by green rami and barred barbules which are yellowish 
 proximally (pi. 30, fig. 76a). The deep purple or blue of some 
 species is produced by a brilliant purple or blue structural color 
 in the rami, and a dark brown pigment color in the barbules. One 
 of the most interesting combinations is in the feathers on the side 
 of the head of Palaeornis cyanocephalus, which are described as 
 rosy, with a bloom like that of a ripe plum. This is produced by 
 a light purplish blue structural color in the rami, and a red pig- 
 ment color in the barbules. 
 
 e) Relationships 
 
 In all respects of feather structure, the Cuculiformes are very 
 closely related to the Coraciiformes, and should probably be con- 
 sidered as nearly allied to the immediate forerunners of this group. 
 The question of their descent is likewise easy, the only lower groups 
 to which they show affinity being the peristeropode Galli and the 
 Columbae; in general form of pennaceous barbules they are nearer 
 to the former, but in the structure of the down and in some details 
 of the structure of the pennaceous barbules, e. g., the prongs on 
 the booklets, they show afSliation with the latter. The Cuculi, 
 especially the Musophagidae, come nearer the gallinaceous and 
 columbid birds, while the parrots are nearer the Coraciiformes in 
 the structure of their feathers. 
 
 f) Summary 
 
 (1) Plumules evenly distributed in Psittaci, sparse and con- 
 fined to apteria in Cuculi. 
 
 (2) Aftershaft present in Psittaci, rudimentary or absent in 
 Cuculi. 
 
 (3) Distal barbules and proximal barbules about equal in 
 number. 
 
 (4) Distal barbules with verj"- elongate base with sinuous ven- 
 tral contour, ventral teeth very small; pennulum shorter than base, 
 
368 University of California Publications in Zoology [Vol. 13 
 
 booklets small, sometimes pronged, ventral cilia short and appressed 
 to barbule in inner vane, proximal dorsal cilia lobate, the others 
 short and spiny. 
 
 (5) Proximal barbules small and slender, ventral teeth inconspic- 
 uous, pennulum rather stout, and shorter than base; well-developed 
 hooked ventral cilia developed in outer vane in Cuculi, but these 
 rudimentary in Psittaei. 
 
 (6) Structure of body feathers mere simplification of that of 
 remiges, the barbicels much reduced. 
 
 (7) Down in most Cuculi with small globular nodes, larger 
 towards base of barbules, and pigment proximal to them; Psittaei 
 with nodes shaped like eucalyptus fruit, and pigmented. 
 
 12. Order CORACIIFORMES 
 Plates 31-33 
 
 This order includes a large number of diversified birds which 
 may be regarded as forming a more or less natural connecting link 
 between the Cuculiformes and lower birds on the one hand, and the 
 Passeriformes on the other. Although some of the included fam- 
 ilies are undoubtedly near the line of descent of the latter, others 
 are to be regarded as very specialized offshoots, e. g., the Striges, 
 and the Bucerotidae. The suborders Coraciae, Striges, Caprimulgi, 
 Colli, Trogones, Cypseli and Piei, as given by Knowlton and Ridge- 
 way (1909), are not of equal value. In discussing the structure 
 of the feathers in this order, that of a species of the typical sub- 
 order will be described in detail and the other families or groups 
 in which important modifications occur with be taken up in order, 
 regardless of the suborders into which they have been grouped. 
 
 Throughout the order the plumules are more or less suppressed; 
 in the Alcedinidae they are dense in the apteria, but sparse in the 
 pterylae; in Striges, Caprimulgi and Cypselidae they are present 
 in the apteria only, while in all other forms they are absent en- 
 tirely. The aftershaft is even more variable, being absent in some, 
 e. g., Buceros, rudimentary in others, e. g., Meropidae, and very well 
 developed in others, e. g. Trogones. 
 
 a) Coracias affinis 
 
 (1) Remex 
 
 Shaft about as wide as deep; median ventral groove small and 
 inconspicuous, striations on sides at junction of barbs slight. Rami 
 
1816] Chandler: Structure of Feathers 369 
 
 narrow, pith more than a single cell in thickness, the vanules placed 
 at a low level on sides, so that rami are as high above as below 
 the attachment of barbules. Ventral ridge narrow and inconspicu- 
 ous. Distal and proximal vanules with about 30 and 22 barbules 
 per millimeter respectively. 
 
 Inner vane. — Distal barbules (pi. 31, fig. 78a) short and broad, 
 about 0.25 by 0.05 mm., the ventral contour sinuate, and ventral 
 teeth small and fingerlike. Pennulum about as long as base, but 
 very frequently broken off just distal to booklets. Hooklets mod- 
 erately long and slender, progressively increasing in length. Ven- 
 tral cilia straight, infiexible, and subequal in size, the first two 
 slightly longer and closer together on account of crowding together 
 of cells. Dorsal cilia rudimentary, except proximal 2 or 3, which 
 are enlarged and lobate, especially on more distal portion of barb. 
 Proximal barbules (pi. 31, fig. 78b) relatively large, the base about 
 0.55 by 0.05 mm.; ventral teeth short, triangular and inconspicuous; 
 pennulum a little shorter than base, and considerably flattened for 
 most of its length. 
 
 Outer vane. — Distal barbules very similar to those of inner vane, 
 except that dorsal cilia are entirely absent, and hooklets are 
 usually 6 in number. Pennulum has some tendency to break off 
 distal to hooklets. Proximal barbules on outer part of barb (pi. 31, 
 fig. 78c), with relatively small, slender base, and long pennulum 
 with a well-developed series of ventral cilia which are strongly 
 hooked and reminiscent of the Galli in their high development. 
 
 (2) other Feathers 
 
 Back feathers characterized by long narrow base of distal bar- 
 bules (0.36 by 0.035 mm.) with small, fingerlike ventral teeth, and 
 reduced barbicels, very much as in the Cuculiformes, the hooklets 
 usually 3 in number, but not pronged. Proximal barbules exceed- 
 ingly slender, the base about 0.55 mm. by 0.03 mm., ventral teeth 
 short and pointed, 4 or 5 in number, pennulum somewhat shorter 
 than base and flattened, but not as much so as in remiges. Breast 
 feathers of same type, but barbicels of distal barbules more re- 
 duced, the cilia being small and the hooklets only two in number, 
 but frequently pronged. Proximals as in back feathers. 
 
 b) Other Types 
 
 Momotidae. — Eemiges in Momotus strikingly similar to Coracias 
 in all details of structure, the pennula of the proximal barbules 
 slightly broader and more jagged in outline on account of rudi- 
 mentary backward-projecting barbicels. Body feathers with more 
 reduced barbicels than in Coracias, often, especially on outer half 
 of barbs, reduced to mere undifferentiated filaments. 
 
 Meropidae. — U crops viridis like Coracias, but proximal barbules 
 on terminal half of barbs of outer vane more slender, with fewer 
 and less well-developed barbicels. 
 
370 University of California Publications in Zoology [Vol. 13 
 
 Alcedinidae. — Ceryle alcyon differs considerably from Coracias 
 in structure of barbules of remiges. Distals of inner vane have 
 long, slender, and conspicuous ventral cilia, and proximals of same 
 vane have shorter pennula, this being only about one-half length of 
 base. On distal half of barbs of outer vane, proximals (pi. 31, fig. 
 79a) have very short, stumpy bases, and short pennula, the ventral 
 barbicels exceedingly long and strong, in fact relatively larger and 
 stronger than they have been found in any other birds. Distal 
 barbules of back feathers also have long ventral cilia. Breast feath- 
 ers unusual in having a series of slender ventral cilia on proximal 
 barbules (pi. 31, fig. 79b). 
 
 Upupidae. — Irrisor viridis has no dorsal cilia whatever on distal 
 barbules even on inner vane of remiges. Hooklets only 4 in num- 
 ber, slender and well separated, ventral cilia well developed, the 
 distal ones more conspicuous on account of the way they lie (pi. 
 31, fig. 83a). Distals of outer vane have the latter character even 
 more conspicuous. Proximals of outer part of barbs of outer vane 
 have short reduced base, and relatively long pennulum with a 
 series of short weak unhooked ventral cilia (pi. 31, fig. 836). Vpupa 
 indica is very similar to Irrisor in structure of feathers. 
 
 Bucerotidae. — Barbules of remiges considerably modified from 
 type. In Hydrocorax mindanensis distal barbules of inner vane 
 (pi. 31, fig. 82a) with very large base with ventral contour strongly 
 sinuate, and ventral teeth relatively large. Pennulum very broad 
 in lateral view in region of hooklets and of first 2 or 3 cells with cilia. 
 Hooklets 4 or 5 in number, very large and heavy, but not elongate; 
 ventral cilia short, stout and blunt, the proximal ones the longer, 
 but not showing when lateral aspect of base is in view on account 
 of twist in pennulum; the more distal ones, however, are in lateral 
 view, so that pennulum appears club-shaped (see plate 31, figures 
 82a and c) ; dorsal cilia rudimentary except basal two, which are 
 large and lobate. Distal barbules of outer vane (pi. 31, figs. 82c, d) 
 very similar, but hooklets usually 6, dorsal cilia absent, and width 
 of booklet region very great, as shown by plate 19, figure 82d. 
 Proximal barbules very long with relatively slender base, 4 or 5 
 moderate, pointed ventral teeth, and broad pennulum, about half 
 as long as base with backward-projecting rudimentary barbicels. 
 Proximals of outer vane do not have barbicels even on outer part 
 of barb, as shown by plate 31, fig. 82e. 
 
 Anthracoceros and Lophoceros agree in important details with 
 
■I^IS] Chandler: Structure of Feathers 371 
 
 Hydrocorax, but in neither are the barbules as large and heavy. 
 The breast feathers and looser back feathers are of the same type 
 as other coraeiiformes, but the barbs are very loose distally, soon 
 giving way to a downy structure. 
 
 Striges. — The owls are characterized by remarkable softness of 
 their plumage, which, as already shown by Mascha (1904), is brought 
 about by an even more remarkable modification in structure of 
 barbules. 
 
 In Bubo maximum, on inner vane of remiges, distal barbules 
 (pi. 32, fig. 84a) have base of typical coraciid type, with sinuate 
 ventral contour and small, slender, ventral teeth, but pennulum 
 excessively elongated, frequently reaching a length of over 2 mm., 
 when the base is only about 0.3 mm., being, therefore, nearly seven 
 times as long. The booklets, 5 in number, very slender, increasing 
 in length to a remarka-ble degree from the proximal to the distal 
 ones. As shown by Mascha (1904), the pennulum is flattened 
 dorso-ventrally and furnished with a complete double series of both 
 dorsal and ventral cilia, which, however, are curved in such a way 
 that their tips project laterally (pi. 32, fig. 84a.). Both dorsal and 
 ventral cilia slender and flexible, the ventral ones, especially on the 
 proximal portion of the pennulum, longer than dorsal ones, the 
 proximal ones of which are not at all enlarged or modified. The 
 proximal barbules (pi. 32, fig. 846) have an elongate, narrow base, 
 long, slender ventral teeth which, however, lie in close juxtaposition 
 and so are inconspicuous, and an exceedingly long filamentous pen- 
 nulum, almost as long as that of the distal barbules. 
 
 On the outer vane distal barbules differ in that pennuhim is 
 much stouter and considerably shorter, with the dorsal cilia entirely 
 absent. Proximal barbules have very slender base and long fila- 
 mentous but moderately heavy pennulum with a series of very 
 slender, delicate and inconspicuous ventral cilia. Comblike outer 
 margin of outer vane due to curving back of the rami, with an 
 accompanying shortening and stiffening of the barbules and loss of 
 the interlocking apparatus. Plate 32, figure 84c represents a distal 
 barbule from this region of barb. 
 
 Body feathers of owls resemble remiges in great length of bar- 
 bules. The delicate, semi-transparent character, especially of breast 
 feathers, is due to wide spacing of barbs and barbules, the former 
 set about 15 per centimeter on each side, the latter 8 or 9 and 12 
 to 15 per millimeter on proximal and distal vanules respectively. 
 
372 University of California Publications in Zoology [Vol. 13 
 
 In breast feathers barbules almost downy, the base very poorly 
 developed and barbicels greatly reduced (pi. 32, fig. 85a). 
 
 The facial disc of owls is the result of a series of very densely 
 set and closely woven feathers. Barbs set 35 or 40 per centimeter 
 and at a very acute angle with shaft, so that they lie very close 
 together, and barbules set about 32 and 38 per millimeter on prox- 
 imal and distal vanules respectively. Distal barbules have short, 
 stout, tapering bases and short pennula, the cells of which are short 
 and crowded, so that the long, closely appressed ventral cilia are 
 very much crowded. 
 
 Caprimulgi. — In Chordeiles virginianus distal barbules of inner 
 vane of remiges resemble those of the Striges in form of their base, 
 ventral teeth, and booklets. Pennulum, as in the Striges, long, but 
 never over 1 mm.; more slender than in owls, and only first 6 or 8 
 cilia developed, the long series of conspicuous dorsal and ventral 
 ones absent. 
 
 In Podargus strigoides, 'filamentous types of distal barbules of 
 inner vane still longer on distal third of barb, being sometimes 
 almost 1.5 mm. long (pi. 32, fig. 87a). Interesting correlative 
 modification in sigmoid backward curve of barbs to give more room 
 for long overlapping pennula and to produce a softer feather. 
 Distal barbules of outer vane in Chordeiles with rather short 
 pennula with a well-developed series of ventral cilia (pi. 32, fig. 86a). 
 Proximal barbules on inner vane, unlike owls, have rather 
 short, stout pennula in Chordeiles, but in Podargus (pi. 32, fig. 876) 
 pennula are long. In the outer vane, proximals have a series of 
 ventral cilia the more proximal of which are stout and hooked, the 
 more distal ones slender and flexible (pi. 32, fig. 86b). 
 
 Body feathers have long, slender pennula, and weakened barbi- 
 cels, mere simplifications of the remex type. 
 
 Although in the great length of the pennula and resulting soft- 
 ness of the plumage the Caprimulgi resemble the Striges, the details 
 of structure, in so far as they differ in these suborders from that 
 of typical Coraciiformes, are not the same, and it is only reasonable 
 to suppose that the similarities are due to parallel evolution and 
 that there is no closer relationship shown between these two groups 
 than between either of them and other coraciiform groups. 
 
 Trogonidae. — Prionotelus temnurus has structure much like 
 Coracias, but especially characterized by form of ventral cilia. 
 Latter very straight and inflexible, and conspicuously larger near 
 
^^^^3 Chandler: Structure of Feathers 373 
 
 tip than near base of pennulum. No dorsal cilia, even on inner 
 vane, and booklets moderately long, only 3 in number (pi. 31, 
 figs. 80a, 80&). Proximal barbules of outer vane, on terminal por- 
 tion of barbs, have ventral teeth increased in number, but remaining 
 blunt, and appressed to barb (pi. 31, fig. 80c), well-developed 
 ventral barbicels never being formed. Body feathers, where not 
 modified for color, with barbules similar to those of remiges, but 
 simpler. 
 
 Cypselidae. — In Cypseloides niger, on inner vane of remiges, 
 distal barbules have base of typical coraeiiform shape, but the 
 ventral tooth, usually single and relatively large, with its tip bent 
 sharply down, giving it a blunt appearance distally. Pennulum 
 with more proximal dorsal cilia developed and stout in form on 
 barbules on outer portion of barbs, on the inner portion only the 
 ventral ones present; these moderate in size and curved as in 
 Coracias, pennulum usually breaking off a little distal to booklets. 
 Proximal barbules with short, broad, tapering bases, the ventral 
 edge more or less scalloped, and pennulum rather heavy, about as 
 long as bases. Body feathers have distal barbules with ventral tooth 
 larger at tip than at base as in some passerine birds. Chaetura 
 differs in having broader bases of the distal barbules and rather 
 reduced booklets. 
 
 Trochilidae. — In remex of Selasphorus rufus, distal barbules are 
 characterized by disproportionate size of base and relatively large 
 ventral teeth. Proportionate to the size of the base, the booklet 
 region of the pennulum and booklets are exceedingly small (pi. 32, 
 figs. 88a and &). In all feathers examined of this species and of 
 several other species the pennulum was broken off one or two cells 
 beyond the booklets as shown in the figures. The base measures 
 about 0.18 by 0.025 mm., while the pennuliim, up to the point 
 where usually broken off, is only one-fifth as long. The proximal 
 barbules have short, broad, tapering bases, with the ventral edge 
 scalloped, ventral teeth inconspicuous and pennulum stout, about 
 as long as base (pi. 32, fig. 88c). 
 
 Body feathers have barbs with approximately equal vanules, the 
 barbules very numerous, about 45 per mm. on each side, with their 
 broad surface exposed, but not in contact on feathers without color 
 modifications. Pennula of barbules of both vanules broad and thin, 
 lying in a vertical plane and turned at such an angle with the base 
 as to be parallel with the ramus (see Beebe, 1906, fig. 27). This 
 
374 University of California Publications in Zoology [Vol. 13 
 
 gives appearance resembling that of the fused outer bar of proximal 
 vanules of tinamous, but in present case pennula are merely in 
 close juxtaposition. 
 
 Coin. — Unfortunately no feathers of birds of this group have 
 been available for study. 
 
 Pici. — This suborder, including the Galbulidae, Capitonidae, 
 Rhamphastidae, and Picidae, seems to be intermediate between 
 Passeriformes and Coraciiformes, the Galbulidae being nearer the 
 Coraciiformes, the other families nearer the Passeriformes. In 
 Galbulidae, exemplified by Jacamerops grandis, the distal barbules 
 of inner vane of remiges (pi. 33, fig. 91a) very long and slender, 
 the pennulum relatively small, as in Trochilidae. Distals of outer 
 vane similar to those of Coracias (pi. 33, fig. 916). Proximals of 
 inner vane with very long, narrow base and stout, tapering pennu- 
 lum about half as long as base; on outer vane a well-developed 
 series of hooked ventral cilia (pi. 33, fig. 91c). In the Bucconinae, 
 represented by Malacoptera fusca, barbules are of typical passerine 
 type. 
 
 In the Picidae the barbules of the remiges are of typical passer- 
 ine form. Distal barbules of inner vane with relatively large and 
 long base, the subnuelear area suddenly narrowing before the small 
 ventral teeth; pennulum relatively small with all the barbicels 
 well developed, but small ' (pi. 33, fig. 89a). Proximals of inner 
 vane (pi. 33, fig. 896) with slender elongate base, inconspicuous 
 ventral teeth, and moderate pennulum somewhat shorter than base. 
 Outer vane differs in distal barbules having shorter base, relatively 
 larger pennulum, and longer booklets, and proximal barbules having 
 a rather heavy elongated pennulum with short, slightly hooked 
 ventral cilia (pi. 33, figs. 89c and d). The Capitonidae and 
 Rhamphastidae agree very closely with the Picidae, the back feathers 
 of Rhamphastidae, represented by Bhamphastus ariel, being remin- 
 iscent of the Trogonidae in the straight, inflexible cilia of the distal 
 barbules, these being largest near tip of pennulum (pi. 33, fig. 90c). 
 
 c) Down 
 
 The down barbules of the various groups of Coraciiformes differ 
 to a very considerable degree, but in nearly all cases they are pig- 
 mented and the nodes are more or less distinct. 
 
 In Coracias, Merops, Momotus, and Irrisor, the down barbules 
 are of moderate length, the cells rather long and gradually swell- 
 
131^] Chandler: Structure of Feathers 375 
 
 ing on the distal two-thirds of their length, this portion being fur- 
 nished with a dark pigment (pi. 37, fig. 110). The cells vary from 
 about 20 per millimeter in Coracias affinis to about 28 in Momotus. 
 
 In Halcyon gularis the cells are very short and relatively stout, 
 often over 30 per millimeter, and nearly twice as large in caliber 
 as in Momotus. Only the terminal third of these cells is enlarged 
 and pigmented, thus giving the barbules a very beady appearance. 
 In Ceryle alcyon the cells are longer and more slender, thus being 
 intermediate between Alcyon and the more typical Coraciae. 
 
 In Hydrocorax mindanensis (Bueerotidae), the down barbules 
 have a very peculiar and unusual appearance, the cells being very 
 short and thick, as many as 40 per millimeter, with the nodes not 
 enlarged but marked by two sharp, spiny prongs. The pigment is 
 almost uniformly distributed (pi. 37, fig. 111). In Anthracoceros 
 the cells are longer and the pigment is confined to the middle of 
 the internodes. The nodes are often very indistinct. 
 
 In the Striges the down is very similar to that of the Cuculi- 
 formes. In Bubo maximus the barbules have three large nodes on 
 the inner part of the pennulum, shaped more or less like the fruit 
 of a eucalyptus tree. Following these the cells are of the type 
 found in Coracias but very elongate, 9 or 10 per millimeter, with 
 the pigment confined to the distal one-fourth or one-fifth. In Aluco 
 pratincola the structure is similar, but there are usually five instead 
 of three enlarged basal nodes, and sometimes a few globular, droplet- 
 like nodes as in Coccyzus. 
 
 In the Caprimulgi the nodes are usually rather indistinct, espe- 
 cially in the Caprimulgidae, where they are almost imperceptible, 
 although the pigment is restricted to a spot near the distal end 
 of each cell. In Podargus the down is like that of Coracias. 
 
 In Cypseloides and Chaetura, representing the family Cypselidae, 
 the down barbules are similar to those of the Caprimulgidae, the 
 cells having dark pigment in their distal portions and light pigment 
 in their proximal portions, the nodes being indistinct. 
 
 In the Trochilidae the structure of the barbules on the more 
 basal portion of the well-developed downy barb is totally different. 
 The bases of these barbules, unlike those of any other birds except 
 the Passeriformes and Pici, are considerably enlarged and widened 
 on the barbules near the base of the barbs, and have irregular villi 
 on the ventral side, as shown in plate 37, figures 112a and h. The 
 pennula are furnished with large, conspicuous nodes of a peculiar 
 
376 University of California Publications in Zoology [Vol. 13 
 
 type for their entire length, and have short internodes (pi. 37, 
 fig. 112). The down barbules of a, large number of genera of 
 Trochilidae have been examined, and all of them have been found 
 to possess this type of structure. The barbules on the outer part 
 of the barbs have inconspicuous nodes, of a type similar to that 
 shown in plate 37, figure 110. 
 
 The Trogons have down very much like the Trochilidae in that 
 the nodes are large and conspicuous and present for the entire 
 length of the pennula, but they are not relatively as large, or the 
 internodes as short, and the bases are not furnished with villi. 
 The nodes are shaped more or less like the fruit of a eucalyptus 
 tree and are deeply pigmented. 
 
 The down barbules of the Pici, like the pennaceous barbules, 
 show a close similarity to the Passeriformes except in the family 
 Galbulidae. In the latter, as exemplified by Bucco, Malacoptera 
 and Jacamerops, the down is like that of Coracias and Momotus. 
 In the Rhamphastidae (Rhamphastiis, Pteroglossus and Andigena) 
 the barbules (pi. 37, fig. 113) have large nodes shaped like euca- 
 lyptus fruits on the proximal portion, these becoming small and 
 insignificant beyond the basal 6 or 7. The bases of the inner bar- 
 bules have weakly developed villi. The barbets, Capitonidae, have 
 down almost exactly like the Rhamphastidae. Iil the Picidae the 
 type is similar except that the basal nodes are relatively smaller, 
 and the decrease in size toward the tip of the barbules is more 
 gradual and less conspicuous. The villi on the bases are well- 
 developed on the barbules near the base of the barbs, as much so 
 as in many Passeriformes. 
 
 d) Color Modifications 
 
 The variety of colors found in the Coraciiformes is unexcelled 
 anywhere amongst birds, and the variety of structural modifica- 
 tions correlated with color production is correspondingly great. 
 
 Many of the Coraciiformes are characterized by the prevalence 
 of deep purple and light blue colors in the wings and tail. The 
 deep purple is a brilliant purple refraction color produced by the 
 large dorsal ridges of the rami, combined with a blackish brown 
 pigmentation in the non-refractive barbules. The beautiful light 
 blue of these birds is produced by a superstructure above the 
 refrangent surface of the dorsal ridges of the rami which otherwise 
 produce brilliant purple, the barbules in this case being unpig- 
 
1916J Chandler: Structure of Feathers 377 
 
 merited and almost transparent. Gentle scraping or light pressure 
 destroys the superstructure of the rami, leaving the purple hue, 
 while crushing destroys this color also and the barb appears 
 blackish. The beautiful light blues and purples of the Old World 
 kingfishers and rollers are produced in this way. 
 
 Dull or olive-green, as in the back and breast of species of 
 Merops and Momotus, is always the result of structural color in the 
 rami and black or brown pigment color in the barbules, while 
 bright, metallic, or iridescent greens, such as that of the back of 
 Jacamerops, the breast and plumes of many trogons, the breast of 
 Irrisor, and of many other species, are the result of refraction 
 from the barbules. In Jacamerops and Irrisor it is produced by 
 the slightly modified bases of the barbules; In the trogons the 
 brilliant green is produced by barbules which are entirely meta- 
 morphosed into color-producing structures which are non-coherent 
 and do not lie fiat, the result being the beautiful effect of tinsel 
 so characteristic of these birds (pi. 31, fig. 81a). 
 
 The blue-gray of Ceryle alcyon is produced, as is that of the 
 gulls, by irregular distribution of black pigment (pi. 31, fig 79a). 
 Blue, like green, is produced either by refraction from the rami 
 accompanied by light or dark pigment color in the barbules, or 
 by refraction from the latter. 
 
 The brilliant iridescent gorget feathers of hummingbirds are 
 among the most interesting color-producing structures to be found. 
 In this case the color is produced by barbules the fianges of which 
 are very broad and recurved, being in some cases wider than the 
 portion of the feather not turned over (pi. 32, fig. 88dt). These 
 barbules, like those of the back and breast feathers which are not 
 modified for the production of color, have broad pennula which lie 
 in a line on the outer edge of the vanule, parallel with the ramus, 
 and are unpigmented, and therefore inconspicuous. In the iri- 
 descent color-producing feathers, the bases of the barbules are so 
 broadened as to produce a solid vanule, i. e., without spaces between 
 the barbules. In the green and blue colors of Petasophora anais, 
 the refraction is from the portion of the barbules which is not 
 curved over, while in the brighter green of Eugenes fulgens, and in 
 all lilac, ruby, or fiery red colors, it is from the broad, recurved 
 flange (pi. 32, fig. 88d), the latter being also produced medially in 
 order to cover the ramus and meet its fellow from the opposite side. 
 
 In hummingbirds alone are there to be found red, lilac, or ruby 
 
378 University of California Publications in Zoology [Vol. 13 
 
 colors which are due entirely to refraction, the pigment being of a 
 totally different color. It is interesting to note that in blue 
 iridescent feathers the underlying pigment is a rich rufous brown, 
 in green a duller fuscous brown, and in all shades of red a very 
 dark olive-green, brighter in the fiery red of Selasphorus rufus 
 than in the lilac or ruby red of other species. This phenomenon 
 is explained by the theory of selective transmission and reflection, 
 colors which are readily reflected being poorly transmitted. 
 
 In various other types of coraciiform birds still other interesting 
 color modifications are to be found, only a few of which may be 
 mentioned here. The coppery green of Jacamerops grandis is pro- 
 duced by barbules very similar in form to those of hummingbirds, 
 the color being reflected from the portion of the barbule not curved 
 over, as in Petasophora. Green in the Capitonidae is produced in 
 an interesting manner, the portion of the ramus ventral to the 
 attachment of the barbules having a deep yellow pigment color, 
 while dorsal to the barbules the rami are curved over flangelike, 
 contain a rich brown pigment, and produce a blue structural color. 
 The combination of blue and yellow by reflected light gives the 
 effect of green, while by transmitted light it is orange brown. The 
 depth and tone of the color varies with the pigment in the non- 
 refrangent barbules. In the woodpeckers the red crests which are 
 so frequently found owe their color to prolonged, cylindrical rami 
 which are filled with a deep red pigment. The peculiar effect of 
 the white and red streaked breast of Asyndesmus torquatus is due 
 to a deep red pigmentation in the dorsal half of the rami, and a 
 white effect in the ventral half, appearing under the microscope 
 like a miniature snow bank, due to the countless minute air spaces 
 which cause diffusion of light. 
 
 e) Relationships 
 
 The Coraciiformes, as stated at the beginning of the discussion 
 of them, constitute a rather heterogeneous assemblage of birds which 
 lie between the Cuculiformes and the lower orders on the one hand, 
 and the Passeriformes on the other. The Coraciidae and near 
 allies, Striges, Caprimulgi, Bucerotidae and Cypselidae, have types 
 of feathers which are to be regarded as independent offshoots from 
 the main line of evolution. The trogons seem to be more nearly in 
 the line of descent of the passerine birds, the Rhamphastidae and 
 Capitonidae of the suborder Pici connecting them with the latter 
 
1916] Chandler: Structure of Feathers 379 
 
 group. The Troehilidae and the suborder Pici, with the exception 
 of the Galbulidae, show such striking likenesses to the Passeriformes 
 that it is difficult to deny their closer alliance to that group than 
 to the Coraeiiformes. 
 
 f) Summary 
 
 The Coraeiiformes are characterized as follows : 
 
 (1) Plumules more or less suppressed, or confined to apteria. 
 
 (2) Aftershaft variable, being absent, rudimentary or well 
 developed. 
 
 (3) Distal barbules of remiges with bases different in different 
 groups but always with small slender ventral teeth; pennulum 
 moderate, with usually not over 5 booklets, the ventral cilia mod- 
 erate, straight, usually longer and more conspicuous near tip of 
 pennulum than at its base; dorsal cilia as a rule poorly developed. 
 Exceptions in the relatively stout, blunt ventral teeth of Troehili- 
 dae, the extremely long pennula of Striges and Caprimulgi, and 
 the minute pennula of Troehilidae, the poorly developed ventral 
 cilia in the inner vane of Podargus, in the large number of stout 
 booklets in the outer vane of Bucerotidae, and in the relatively 
 high development of the proximal two dorsal cilia in the Bucer- 
 otidae. 
 
 (4) Proximal barbules of inner vane of remiges usually with 
 slender elongate base, moderate ventral teeth, and rather broad 
 pennulum somewhat shorter than base. Exceptions in short broad 
 bases in Troehilidae, and in greatly elongated pennula in Striges 
 and Caprumulgi. 
 
 (5) Proximal barbules on distal part of barbs of outer vane 
 of remiges with moderately developed series of hooked ventral cilia. 
 Exceptions in enormous talon-like ventral cilia of Ceryle, non- 
 barbicelled pennulum of Bucerotidae and Troehilidae, and weak 
 cilia of trogons, hoopoes and owls. 
 
 (6) Body feathers, where unmodified for color production, mere 
 simplifications of remex type. 
 
 (7) Down always more or less pigmented, with nodes slightly 
 enlarged and inconspicuous in typical coraciid forms, larger and 
 beadlike in Alcedinidae, and almost unnoticeable in Caprimulgi 
 and Cypselidae; barbules coarse, with prongs at nodes, in Bucero- 
 tidae; nodes large basally and inconspicuous distally in Striges and 
 
380 University of California Publications in Zoology [Vol. 13 
 
 Pici; bases of down barbules with villi on ventral edge in Trochili- 
 dae and Pici (except Galbulidae). 
 
 13. Order PASSBRIFORMES 
 
 Although containing nearly one-half of all known birds, this 
 order forms a very compact group, all the members of which are 
 so closely related that the entire order is hardly more diverse in 
 its forms than is a single suborder in other groups, and although 
 they are divided into numerous families, these have hardly more 
 than generic or supergeneric value as compared with families in 
 most other groups. As would be expected, the feather structure 
 varies but little in the different forms, in this regard the Passi- 
 formes being in sharp contrast to the Coraciiformes. 
 
 In all of the Passeriformes the plumules are very sparse in the 
 apteria, or are absent entirely. The aftershaft, though sometimes 
 rudimentary or absent, is usually present, being composed of a few 
 long, straggly barbs, and a very short shaft. 
 
 a) Cyanocitta stelleri 
 
 (1) Remex 
 
 Shaft about as broad as deep, the median groove small and 
 inconspicuous, striations on sides at junction of barbs inconspicuous 
 or absent. Pith of rami only a single cell thick, the vanules set 
 low, ventral ridge well developed, with smooth ventral edge. 
 Vanules each with about same number of barbules, about 28 in each. 
 
 Inner vane. — Distal hariules (pi. 33, fig. 92a) of same type as in 
 Melanerpes formicivorus (compare plate 33, figure 89a with plate 
 33, figure 92a). Base very large and elongate, about 0.35 by 0.035 
 mm., the broad, filmlike, subnuclear area curving in just proximal to 
 ventral teeth, so that at this point the base is very narrow; ventral 
 teeth small and slender. Pennulum relatively very small, less than 
 half length of base; booklets 3 or 4 in number, small, subequal, 
 and never with prongs; ventral cilia small, more or less appressed 
 to pennulum, and inconspicuous; dorsal cilia short and spinelike, 
 the basal two somewhat enlarged, but not lobate. Proximal harhules 
 (pi. 33, fig. 926) with base relatively small compared with that of 
 distals, about 0.37 mm. by 0.035 mm., the ventral edge scalloped 
 more or less, ventral teeth short, pointed, and inconspicuous; pen- 
 nulum moderately flattened, about two-thirds as long as base. 
 
 Outer vane. — Distal barbules (pi. 33, fig. 92c) with much shorter 
 and broader base than in inner vane, about 0.22 mm. by 0.04 mm., 
 the broad subnuclear area as in the inner vane but curved more 
 conspicuously towards next succeeding barbule. Pennulum rela- 
 tively longer, booklets similar, ventral teeth better developed, larger 
 distally on barbule, as in trogons and Pici. Proximal barbules 
 
1916] Chandler: Structure of Feathers 381 
 
 (pi. 33, fig. 92d) similar to those of inner vane, the bases becoming 
 shorter on distal third of barbs. At extreme tip, base reduced and 
 almost lost, the pennulum weak, with small barbicels on both dorsal 
 and ventral sides. 
 
 (2) other Feathers 
 
 Plumage of back and breast rather hairlike, due to non-coherence 
 of barbs on their outer portions, on account of very loose inter- 
 locking of barbules. Vanules open, i. e., with wide spaces between 
 barbules, due to vertical position of latter and to their wide spacing, 
 there being only about 18 or 20 per millimeter on each side. Distal 
 barbules (pi. 33, fig. 92e) with narrow tapering bases which have 
 ventral part curved slightly toward next succeeding barbule, as in 
 remiges; barbicels all greatly reduced or missing, except 2 slender 
 but persistent booklets. Proximal barbules (pi. 33, fig. 92/) with 
 no sharp demarcation of base and pennulum, except a bend; form 
 narrow, and tapering from slightly expanded proximal portion of 
 base all the way to tip; total length about 0.8 mm. 
 
 b) Other Types 
 
 Throughout the group, except in case of color modifications, 
 there is very little divergence from this type. In Corvus corax 
 the ventral teeth of the distal barbules are more highly developed 
 than usual, being rather broad and triangular, and sometimes 
 bifurcated at the tip; in this species, also, the two basal dorsal cilia 
 reach an unusually high degree of development, as in the case of 
 Hydrocorax among the Coracii formes. Proximal barbules of outer 
 vane develop ventral cilia only at extreme tip, the ventral teeth in 
 these barbules becoming separated from one another, and assuming 
 a short spinelike form. 
 
 In the Frigillidae, Bombycillidae, Icteridae, and other families 
 more or less closely related to the finches, the distal barbules are 
 characterized by the peculiar form of the ventral teeth, which are 
 relatively very long and large, being broader at the middle of their 
 length than at their base. This character is shown in plate 33, 
 figure 94a, representing a distal barbule from the inner vane of a 
 remex of Pipilo maculatus. In some genera of the Turdidae, e. g., 
 Planesticus, there is a tendency for the distal barbules to adhere to 
 each other by means of the greatly elongated ventral teeth which 
 behave as if weakly fused with each other into a longitudinal bar, 
 not unlike the bar formed by the pennula of the proximal barbules 
 in Tinamous. 
 
 In the Tyrannidae, and to a greater or less extent in the 
 Mniotiltidae, Vireonidae, Turdidae, and many other allied families, 
 
382 University of California Publications in Zoology [Vol. 13 
 
 the proximal barbules on the outer half of the barbs of the outer 
 vane of the wing feathers undergo a rather sudden change. On 
 the inner portion of the barbs, the proximal barbules have mod- 
 erate bases and unusually broad pennula, but near the middle of 
 the barb the base suddenly becomes greatly reduced and the pen- 
 nulum elongated, the latter with a series of strong, hooked, ventral 
 cilia which are very conspicuous (pi. 33, fig. 93a.). Concomitant with 
 this specialization of the proximal barbules, the distals deteriorate, 
 the differentiation between base and pennulum being lost, the 
 former being short and triangular, only about 0.1 mm. long to the 
 point where it merges into the pennulum; no barbicels except a few 
 rudimentary dorsal and ventral ones near tip. 
 
 Although representatives of a very large number of passerine 
 families have been examined, no further modifications worthy of 
 special mention here have been found in the group, except in con- 
 nection with color production or some other macroscopic effect, as 
 in the ornamental plumes of birds of paradise and lyre birds. 
 Plate 33, figure 95a shows the tip of a "wax-tipped" feather of 
 Bombycilla garrula, showing the method of fusion of shaft with 
 outer vane only. This "wax-tip" has usually been looked upon 
 merely as the expanded terminal portion of the shaft. 
 
 c) Down 
 
 With the exception of its occurrence also in the Troehilidae 
 and all of the Pici except the Galbulidae, the down barbules of 
 passerine birds have a constant and peculiar character in the pres- 
 ence of lobate or fingerlike villi on the ventral edge or on the side 
 of the base, as shown in plate 37, figure 1156, and also in figures 
 114a and b, and 115a of the same plate. Down from over one 
 hundred species of passerine birds has been examined, these being 
 representatives of as diversified families as could be obtained, and 
 this character has never been found missing on the barbules near 
 the base of the well-developed downy barbs. It is never present, 
 as far as I have observed, on the barbules on the more distal pari* 
 of the barbs, nor in the aftershaft. 
 
 The pennula of the downy barbules are of moderate length, 
 ranging from about 1 mm. in most forms, e. g., Myiarchus and 
 Turdus, to 5 mm. in Menura. With a few exceptions, as in Haema- 
 toderus (Cotingidae), in the red shoulder patches of Agelaius phoeni- 
 ceus, and in a few other cases, usually where the feathers are red. 
 
1916] Chandler: Structure of Feathers 383 
 
 the down is pigmented, and grayish in color. The nodes, except in 
 such unpigmented down as that referred to above, are always con- 
 spicuous, but not strikingly larger near the base of the barbule 
 than at its tip. The shape of the nodes and length of internodes 
 varies considerably in different birds, the nodes being shaped like 
 a eucalyptus fruit in Corvus (pi. 37, fig. 115), and spaced about 
 22 per millimeter; of similar shape, but about 32 per millimeter in 
 Myiarchus; more rounded and about the same number in Menura; 
 of Coracias type (pi. 37, fig. 110) in Cinclus; exceedingly numerous 
 and prominent in the Mniotiltidae, 35 or more per millimeter, and 
 even more numerous in some of the Fringillidae (pi. 37, fig. 114). 
 
 d) Color Modifications 
 
 The colors of passerine birds are produced in much the same 
 way as in the Coraciiformes. Yellow is produced either by struc- 
 ture, pigment, or both. The yellowish straw color of the head and 
 neck feathers of Paradisea apoda is due almost if not entirely to 
 structure; the yellow of the belly feathers of Myiarchus cinerascens 
 and Tyrannus verticalis to a combination of a structural modification 
 and an underlying yellow pigment; the yellows and orange yellows 
 of Oriolus and various species of Mniotiltidae to pigment only, dis- 
 tributed in both rami and barbules. 
 
 Eed, as far as I have observed, is always the result of pigment, 
 frequently deepened in color by the high polish of the barbs in 
 which it occurs. Dull reds, such as that on the breast of Piranga 
 rubra are produced by pigment on both rami and barbules. The 
 fiery red crests of Tyrannus and Pyrocephalus are produced by red 
 pigment in naked rami which have diagonal lines running partly 
 across them, these representing rudimentary barbules arrested in 
 their development, and fused with the ramus. Other deep and 
 intense reds are produced by naked barbs which sometimes have no 
 structural modifications. 
 
 The deep blue of Progne subis is due to barbules which are 
 reduced to straight flattened bands partially overlapping each other, 
 and with refrangent surfaces, the tips always broken off, leaving 
 the ends truncate. The bright blue of the lazuli bunting, Passerina 
 amoena, is produced by refraction from naked rami. 
 
 The brilliant red and green feathers of Nectarinia famosa are 
 worthy of special mention. The tips of the rami in these feathers 
 are naked and have a deep red color, thus giving the shining red 
 
384 University of California Publications in Zoology [Vol. 13 
 
 edges to the feathers. The inner portion of the barbs has no red 
 in the rami, and has a series of closely-set flattened barbules, 
 resembling the pennula in green speculum feathers of ducks in 
 that there are constrictions between the cells, and each individual 
 cell is more or less warped and spoon-shaped (Gadow, 1882, pi. 28, 
 figs. 9a, 6). These barbules produce a brilliant green refraction 
 color, and thus give the green color to the inner portion of the 
 feather. The minute details of the method of refrangent color 
 production in pittas has been worked out by Gadow (1882), and 
 Strong (1902). 
 
 e) Belatitmships 
 
 The Passeriformes, according to feather structure, are to be 
 regarded as a compact group in which, in spite of the large number 
 of species, very little divergence has taken place. It constitutes 
 a terminal branch of the phylogenetic tree, its next lower relatives 
 being undoubtedly the Coraciiformes, especially the suborder Pici, 
 which, however, is probably to be regarded itself as a member of 
 this group rather than of the Coraciiformes. 
 
 f) Summary 
 
 The Passeriformes are characterized as follows: 
 
 (1) Plumules sparse in apteria or absent entirely. 
 
 (2) Aftershaft absent, rudimentary, or in the form of a few 
 long, straggly barbs. 
 
 (3) Distal and proximal vanules of remiges with about equal 
 number of barbules. 
 
 (4) Distal barbules of remiges very large relative to proximal 
 barbules, the bases of each type about equal. 
 
 (5) Distal barbules of inner vane of remiges with large elongate 
 base, with broad filmlike subnuclear area not extending all the way 
 to ventral teeth; ventral teeth small and slender, as in Coracii- 
 formes, or elongate and enlarged distally; pennulum relatively 
 small, the booklets moderate and well spaced, ventral cilia short, and 
 subequal, dorsal cilia small, the basal two more or less enlarged. 
 
 (6) Distal barbules of outer vane of remiges with much shorter 
 base, and relatively larger pennulum and booklets. 
 
 (7) Proximal barbules of inner vane of remiges with elongate, 
 relatively small base, inconspicuous ventral teeth, and pennulum 
 shorter than base. 
 
^^^6] Chandler: Structure of Feathers 385 
 
 (8) Proximal barbules of outer vane of remiges without ventral 
 cilia except at extreme tip of barbs, or with a sudden transition at 
 about middle of barb. 
 
 (9) Looser body feathers with barbules very much reduced and 
 simplified, with all barbicels rudimentary or absent except two or 
 three booklets on distals. 
 
 (10) Down barbules with lobate or fingerlike villi on base, the 
 pennulum with more or less distinct nodes, the latter not strikingly 
 larger near base of barbules. 
 
 IV General Conclusions 
 1. Taxonomic Value of the Structure of Feathers 
 
 The systematic study of the structure of feathers of different 
 groups of birds which has been made and presented in the preced- 
 ing pages cannot but impress one with the fact that the morphology 
 of feathers, in other words, the epiphyology of birds, is as valuable 
 from a taxonomic point of view as is osteology, myology, or the 
 systematic morphology of any other organ or system of organs of 
 the body. Not only is the difference between birds of different 
 groups of larger content as clearly marked in the structure of their 
 feathers as in the structure of any other system of organs, but the 
 fact that most of the modifications in these minute details of 
 structure which are found in different groups of birds can be of 
 little or no adaptive value, increases the taxonomic value beyond 
 that possessed by most other organs, since parallel or convergent 
 adaptive evolution is largely eliminated. As in all other organs, 
 parallel evolution which is not necessarily correlated with adapta- 
 tion may take place, and undoubtedly has done so, with the result 
 that the structure of feathers alone is not a safe criterion of rela- 
 tionship any more than is the structure of the bones or muscles. 
 Taken in conjunction with the evidence furnished by other organs 
 and systems of organs, however, and with these as a general guide, 
 the cases of parallelism in evolution can in most cases be discov- 
 ered, and the evidences of relationship and phylogenesis furnished 
 by the morphology of feathers is then of the very highest value. 
 
 As has been pointed out by Coekrell (1911a), the scales of 
 fishes are unquestionably of great taxonomic value. Work on the 
 
386 University of California Puilications in Zoology [Vol. 13 
 
 scales of reptiles and on the hair of mammals shows promise of 
 bringing out facts concerning them also, which will be of taxonomic 
 value. But in all of these the range of possible or probable modi- 
 fiability is very slight as compared with that of feathers, on account 
 of the much greater complexity and minute structural units of the 
 latter, and therefore the morphology of feathers is of greater value 
 than lepidology or any other branch of epiphyology from a taxo- 
 nomic point of view. 
 
 2. Principal Modifications of Structure Useful in Taxonomy 
 
 There are a great many different parts of feathers and plumage 
 which show phylogenetic modifications, among which some are of 
 great value and can almost certainly be depended upon to be of 
 importance in showing relationships, while others are as plainly of 
 very doubtful value. From the foregoing systematic study of the 
 different groups of birds, the relative value of the different structures 
 and arrangements of different parts of feathers has made itself 
 apparent, and the following general conclusions may be drawn. 
 
 The distribution of plumules is a character which, in itself, is of 
 little value, on account of its great variability, in a few eases, within 
 a single group, and on account of the adaptive value of the plumules, 
 as shown by their presence in all the lower orders of water-birds and 
 their recurrence in kingfishers amongst a group in which there is 
 elsewhere a tendency for plumules to be reduced or entirely lost. 
 However, in conjunction with the condition of other structures, the 
 distribution of plumules is of some phylogenetic importance. 
 
 The aftershaft is of more importance, and its presence or absence, 
 and form if present, may be depended upon to a considerable extent 
 as showing phylogenetic tendencies. 
 
 The quill, even of the remiges, is too variable within groups to be 
 of any great value except in a few cases, as, for instance, in the 
 Anseres, where the disproportionate length of the calamus is of diag- 
 nostic value. The condition of the ventral groove and of the stria- 
 tions on the sides are of little value except in a few eases. 
 
 The rami have a number of characters which are significant, 
 namely, the thickness of the pithy portion, whether of one or more 
 layers of cells (see Mascha, 1904), the width relative to the shaft, 
 the relative size and form of the ventral ridge, and the presence or 
 absence of villi on its ventral edge in the outer vane. 
 
 The distal hariules of the remiges have a number of characters 
 
1916] Chandler: Structure of Feathers 387 
 
 which are of high value from a taxonomic point of view, namely, the 
 number and size relative to the proximal barbules, the form and gen- 
 eral character of the base, the general size and form of the pennulum 
 relative to the base, the number, size, shape, and general characters of 
 the various kinds of barbicels, especially the ventral teeth, ventral 
 cilia, and basal dorsal cilia, and finally, the differences between the 
 distal barbules of inner and outer vane. 
 
 The proximal barhuies are far less variable than the distal barb- 
 ules, and as a rule are of much less taxonomic value. Their chief 
 phylogenetie modifications are in the following: size of base relative 
 to distal barbules, and relation of width to length ; number, form, and 
 conspicuousness of ventral teeth ; form of pennulum, and length rela- 
 tive to base; and condition of ventral cilia in barbules near the tip 
 of barbs in the outer vane. 
 
 The chief value of the body feathers lies in the degree and man- 
 ner of simplification of the barbules from the remex types, and the 
 presence or absence, and form, if present, of flexules. 
 
 The down barbules from the region of the superior umbilicus of 
 remiges and large coverts, and from the less developed portions of 
 barbs of other feathers, e. g., at the tip of the barb, are not always of 
 taxonomic value, but the typical down barbules from a portion of the 
 feather where they reach their highest development, as for instance 
 near the base of the distal vanule of a well-developed downy barb, 
 are of very great value from a phylogenetie point of view; in fact, 
 it is frequently possible by means of the down alone to identify the 
 group to which a bird belongs and unquestionably to determine its 
 relationship to other groups. The characters which are of value are 
 the length, the size and form of the base (of value only in the case of 
 some Coraciiformes and Passerif ormes) , the character and frequency, 
 of the nodes, and the presence or absence of prongs. 
 
 Methods of color production are of more or less taxonomic value 
 in certain cases. For instance, the iridescent colors of ducks and 
 other water-birds are produced differently than in gallinaceous birds, 
 and in both of these differently than in Coraciiform birds. 
 
 3. Relationships of Groups Suggested or Corroborated 
 
 The morphology of feathers, as presented in the preceding pages, 
 adds one more basis for comparison of different groups of birds, and 
 seems to throw new light on the relationship of certain groups to 
 others. A classification which even comes near to expressing true 
 
388 University of California Publications in Zoology [Vol. 13 
 
 relationships cannot be based on any single character; it must be 
 a composite picture of the evidence furnished by all the characters. 
 In the following paragraphs there is given a summary of the evi- 
 dence furnished by one single small character, the morphology of the 
 minute structure of feathers. In itself it is obviously inadequate. 
 Taken in conjunction with the evidence furnished by other characters, 
 however, it is hoped that the evidences of relationships suggested by 
 epiphyology may help to bridge the gaps left by other comparative 
 studies, and so help to complete and perfect the chains of relationship 
 in avian phylogeny. 
 
 Beginning with the Ratitae, the structure of the feathers of the 
 various orders included in the group gives very strong evidence in 
 favor of their being primitively rather than secondarily flightless 
 birds, the Struthioniformes and Rheiformes apparently being end 
 branches of one main evolutionary stem, and the Casuariiformes and 
 Apterygiformes similar end branches of another stem which is prob- 
 ably to be considered a little nearer to the line leading to the Cari- 
 natae (see summaries on pages 288, 290, 293, 295). 
 
 Among carinate birds the most primitive feathers are to be 
 found among the penguins, and next above them the Colymbiformes 
 (for details, see pages 298 and 302). Prom this group two im- 
 portant lines of evolution are suggested, one leading up through 
 the Alcidae to the Laridae and Limicolae, and through the Rallidae 
 and Gruidae to the Galli, Columbae, and finally the Passeriformes, 
 while the other leads through the Procellariiformes and Cieoniiformes 
 to the Anseres and Falconiformes. "While the writer does not be- 
 lieve that this is necessarily the true phylogenetic relationships of 
 the various groups, nor even contend that it is nearly the correct 
 interpretation, nevertheless with the facts now at hand, it satisfies 
 the conditions of the feather morphology better than any other 
 interpretation at present available. According to morpohology of 
 feathers there is strong evidence for the following hypotheses : 
 
 (1) The Procellariiformes, while constituting a specialized off- 
 shoot, lie near the line of descent of the Cieoniiformes, the nearest 
 of the latter order to the primitive type being the Steganopodes, while 
 the Ardeae are the most specialized. 
 
 (2) Plotus and Phalacocorax deserve to be separated into two 
 distinct families, the former showing remarkable likenesses to the 
 Cathartae. 
 
1916] Chandler: Structure of Feathers 389 
 
 (3) The Phoenicopteri have a type of feather structure which 
 is intermediate between that of the Ciconiae and the Anseres (see 
 summaries on pages 320, 326 and 330). 
 
 (4) The Phaethontidae seem to be more closely related to the 
 Laridae than to the Steganopodes. 
 
 (5) The Aleidae show very striking similarities to the Colymbi- 
 formes, and likewise appear to be closely related to the Laridae, 
 and may therefore be considered as more or less -intermediate. 
 
 (6) The Gruiformes, while having some features in common 
 with the Ciconiiformes, seem to be nearer the Limieolae, this being 
 especially true of the Rallidae and Aramidae. 
 
 (7) The strikingly heronlike epiphyology of Eurypyga and 
 Cariama, at least of Eurypyga, suggests the possibility of their 
 being grouped as aberrant Ardeae. 
 
 (8) Cursorius, representing the family Glareolidae, appears to be 
 out of place, and to find its nearest affinity with the Ardeae, rather 
 than with the Limieolae. 
 
 (9) The Pteroclo-columbae seem more closely related to the gallina- 
 ceous birds, especially the alectoropode Galli, than to the Laro- 
 limicolae, with which they seem to have no real relation (see sum- 
 mary, page 362). 
 
 (10) The Tinamidae show strong evidence of being a highly spe- 
 cialized offshoot from the Galliformes (see summary, page 347). 
 
 (11) The Cuculiformes are more or less intermediate between 
 the peristeropode Galliformes and Columbae on the one hand, and 
 the Coraciiformes on the other, but seem not to differ to a sufficient 
 extent from the latter to warrant their separation into a distinct 
 order. 
 
 (12) The Trochilidae and aU of the suborder Pici, with the 
 exception of the Galbulidae, appear to be more closely related to 
 the Passeriformes than to the Coraciiformes. 
 
 (13) The Galibulidae show evidence of not belonging with the 
 Pici. 
 
 With the exception of these relatively few cases of disagree- 
 ment with the phylogenesis and relationships accepted by Knowlton 
 and Ridgway (1909), the evidence of the morphology of feathers 
 strongly supports the grouping made by these authors, this in turn 
 being the grouping made by Gadow (1891), with a few minor 
 modifications. 
 
390 University of California Publications tn Zoology [Vol. 13 
 
 4. The Phylogenesis of Birds as Modified iy Morphology of Feathers 
 
 As intimated above, distinct lines of evolution in the modification 
 of the structure of feathers are clearly shown by this study. After 
 making a careful analysis of these various lines of divergence, which 
 seem to be more or less orthogenetic in nature, a phylogenetic tree 
 representing the evolution of birds has been worked out, and is pre- 
 sented in fig. G (p. 391). In so far as it is in accord with the facts of 
 morphology of the feathers, the classification presented by Knowlton 
 (1909) has been adhered to in the preparation of this evolutionary 
 tree, since it is believed that this classification is most nearly in 
 accord with the views of most of the leading ornithologists of the 
 present time, and most nearly embodies the evidence furnished by 
 recent work on comparative avian anatomy and morphology. In 
 all cases in which the evidence furnished by morphology of feathers 
 is distinctly not in accord with Knowlton 's interpretation of rela- 
 tionship, the classification has been altered so as to agree with the 
 facts of epiphyology presented in this paper. The phylogenesis 
 presented, therefore, is one which is based primarily on morphology 
 of feathers, but in which the system presented by Knowlton (1909) 
 has been adhered to in so far as there was no conflict. While it 
 is not supposed that such an interpretation of relationship is neces- 
 sarily the correct one, or that some other interpretation may not 
 be made which will better satisfy all the conditions of avian struc- 
 ture, it is hoped that the accompanying phylogenetic tree will be 
 of use to taxonomists in the embodiment of the facts presented in 
 this paper in the preparation of a system of classification which 
 will best satisfy the conditions of all branches of the comparative 
 morphology of birds. 
 
 Transmitted April 17, 1914- 
 
1916] 
 
 Chandler: Structure of Feathers 
 
 391 
 
 \Cypselidae\ \ pas,eriformts\ 
 
 \Caprimulgi 
 
 Pfcij ^ \Coraciae\ 
 
 \Striges\ 
 
 \Cdlumbae 
 
 \Tragones ^ 
 
 \CacuUformes 
 
 Accipiires] 
 
 \Ardeae\ IPhoeiiicopieri] 
 
 I Ettiypygidae\- 
 
 \Ciconiae\ 
 
 Fig. G. Phylogenetic tree showing liypothetical relationships of birds, based 
 on Knowlton and Rldgway's (1909) classification, with all changes 
 suggested by morphology of feathers incorporated. 
 
392 University of California Publications in Zoology [Vol. 13 
 
 BIBLIOGRAPHY 
 
 Ahlbobn, F. 
 
 1896. Zur Mechanik des Vogelfluges. Abh. Geb. d. Naturwiss., Hamburg, 
 14, 1-134, 54 figs, in text. 
 AiXElf, J. A. 
 
 1896. Alleged changes of color in the feathers of birds without moulting. 
 
 Bull. Am. Mus. Nat. Hist., 8, 13-44. 
 Altum, B. 
 
 1854a. Ueber die Farben der Vogelfedern im Allgemeinen, uber das 
 Schillem insbesondere. Naumania, Arch. f. d. Ornith., Jahrg. 
 1854, 293-304. 
 1854b. Ueber den Bau der Federn als Grund ihrer Farbung. Journ. f. 
 Ornith., Jahrg. 2, xix-xxxv. 
 Beddabd, F. F. 
 
 1885. On the aftershaft in the feathers of certain birds. Ibis, (5), 3, 
 
 19-23. 
 1898. The structure and classification of birds. (London, Longmans), 
 XX 4- 548, 252 figs, in text. 
 Bkebb, C. W. 
 
 1904. The ostriches and their allies. Ann. Rep. N. Y. Zool. Soc, 9, 
 
 203-229. 
 1806. The bird, its form and function. (New York, Holt), xi + 496, 
 1 pi., 371 figs, in text. 
 Bloch, a. 
 
 1897. Le pigment du syst6me pileu et son origins. Bull. Soc. d'Anthrop., 
 
 Paris (4), 8, 573-578. 
 
 BOGDANOW, A. 
 
 1856. Note sur le pigment des plumes des oiseaux. Bull. Soc. Nat, 
 
 Moscou, 29, 459-462. 
 1858. Ftudes sur les causes de la coloration des oiseaux. Rev. et Mag. 
 
 Zool., (2), 10, 180-181. 
 
 BONHOTE, J. L. 
 
 1912. On a peculiar type of feather in the water rail. British Birds 
 (London), 5, 42-44, 1 fig. in text. 
 Chandler, A. C. 
 
 1914. Modifications and adaptations to function in the feathers of Circus 
 hudsonius. Univ. Calif. Publ. Zool., 11, 329-376, pis. 16-20. 
 Chukch, a. H. • 
 
 1893. Turacin, a remarkable animal pigment containing copper. Nature, 
 48, 209-211. 
 Clement, C. 
 
 1876. Note sur la structure microscopique des plumes. Bull. Soc. Zool. 
 France, 1, 282-286. 
 
 COCKERBLL, T. D. A. 
 
 1910a. The scales of the African cyprinid fishes, with a discussion of 
 related Asiatic and European species. Proc. Biol. Soc. Wash., 
 23, 141-152. 
 
 1910b. The scales of the clupeid fishes. Ibid., 23, 61-63. 
 
 1910c. The scales of atherinid fishes. lUd., 23, 47-48. 
 
1916] Chandler: Structure of Feathers 393 
 
 1910d. The scales of the African characinid fishes. Smithson. Misc. Coll., 
 
 56, No. 1, 1-10, pis. 1-2. 
 1910e. The scales of the mormyrid fishes. Ibid., 56, No. 3, 1-4. 
 1910f. The scales of European cyprinoid fishes. Zool. Anz., 36, 475-480, 
 
 3 figs, in text. 
 1911a. The scales of freshwater fishes. Biol. Bull., 20, 367-375, pis. 1-5. 
 1911b. The scales of dipnoan fishes. Science, n. s., 33, 831-832. 
 1911c. Additional note on reticulated fish scales (with note on IcUfhyo- 
 
 phis). Ibid., 34, 127. 
 1912. The scales of Dermophis. Ibid., 36, 681. 
 
 1913a. A peculiar dermal element in chimaeroid fishes. Ibid., 38, 363. 
 1913b. The scales of the simenchelyid, ophidid, brotulid, and breg- 
 
 macerotid fishes. Proc. Biol. Soc. Wash., 26, 75-77. 
 CocKERELL, T. D. A., and Allison, E. M. 
 
 1909. The scales of some American Cyprinidae. Ibid., 22, 157-164. 
 CocKEEELL, T. D. A., and Callaway, 0. 
 
 1909. Notes on the scales of fishes. The herbivorous Cyprinidae. Ibid., 
 
 22, 121-123. 
 CocKBEELL, T. D. A., and Moore, E. V. 
 
 1910. On the modifications of the clrculi on the scales of Asiatic 
 
 cyprinid fishes. Zool. Anz., 36, 252-253. 
 
 COUES, E. 
 
 1884. Key to North American birds. (Boston, Estes and Lauriat), 
 XXX + 863, 561 figs, in text. 
 
 CUVIEE, Gr. 
 
 1809. Leeons d'anatomie comparSe. RecuillSes et pubises par C. Dumeril, 
 Paris. 
 Daviks, H. R. 
 
 1889. Die Entwicklung der Feder und ihre Beziehung zu anderen Integu- 
 
 mentbildungen. Morph. Jahrb., 15, 560-645, pis. 23-26. 
 DUEEDEN, J. E. 
 
 1911. The plumages of the ostrich. Agr. Jour. Union S. Afr., Pretoria, 
 
 1, 29-37, figs. 1-13. Reprinted in Rep. Smithsonian Inst., 
 1910, 561-572, 8 pis. 
 DWIGHT, J. Jr. 
 
 1900. The sequence of plumages and moults of the passerine birds of 
 
 New York. Ann. N. Y. Acad. Sci., 13, 73-360, pis. 1-7. 
 1902. Plumage cycles and the relations between plumages and moults. 
 
 Auk, 19, 248-255. 
 1907. Sequence in moults and plumages with an explanation of plumage 
 cycles. Ornis (London), 14, 513-518. 
 Evans, A. H. 
 
 1899. "Birds" in Cambridge Natural History. (London, Macmillan), 9, 
 xvi + 635, 144 figs, in text, 2 maps. 
 Fatio, v. 
 
 1886. Des diverses modifications dans les formes et la coloration des 
 plumes. Mem. Soc. Phys. et Hist. Nat. GenSve, 18, 249-308, 3 pis. 
 
 FlOALBI, E. 
 
 1890. Sulla architettura istologica di alcuni peli degli uccelli con con- 
 
 siderazioni sulla filogenia dei peli e delle penne. Atti (Mem.) 
 Soc. Toscana di sci. nat., 11, 227-266. 
 
394 University of California Publications in Zoology [Vol. 13 
 
 FtJRBRINGER, M. 
 
 1888. Untersuchungen zur Morphologie und Systematlk der Vogel, -zu- 
 gleich ein Beltrag zur Anatomie der Stiitz- und Bewegungsor- 
 gane. Bljdr. tot de Dierk., 15, i-xlix, 1-1751, pis. 1-30. 
 Gadow, Hans. 
 
 1882. On the color of feathers as affected by their structure. Proc. 
 
 Zool. Soc. London, 1882, 409-421, pis. 27-28. 
 1888. Remarks on numbers and phylogenetlc development of remlges 
 
 of birds. Proc. Zool. Soc. London, 1888, 655-667. 
 1891-1893. "Vogel. I. Anatomischer Theil. II. Systematischer Theil" 
 
 in Bronn, Klass. und Ordn. des Thierreichs, 6, Abth, 4, I, 
 
 pp. 1-1008, 59 pis., flgs. in text; II, pp. i-vii, 1-304.- 
 
 1911. Isotely and coral snakes. Zool. Jahrb., Abth. fur Syst., 31, 1-24, 
 
 pi. 1, 18 flgs. in text. 
 Habokee, V. 
 
 1890. Ueber die Farbe der Vogelfedern. Arch. f. mikr. Anat., 35, 68-87, 
 pi. 4. 
 Headlet, F. W. 
 
 1895. The structure and life of birds. (London, Macmillan), xx + 414, 
 78 flgs. in text. 
 
 1912. The flight of birds. (London, Witherby), x + 163, 16 pis., 27 flgs. 
 
 in text. 
 
 HOBNADAT, W. J. 
 
 1913. Our vanishing wild life, its extermination and preservation. (New 
 
 York, Scribner), xv + 411, many illus. 
 Jeffries, J. A. 
 
 1883. The epidermal system of birds. Proc. Bost. Soc. Nat. Hist., 22, 
 
 203-241, pis. 4-6. 
 Jones, L. 
 
 1907. The development of nestling feathers. Bull. Oberlin Coll., 13, 
 1-18, pis. 1-8. 
 Klee, R. 
 
 1886. Bau und Entwickelung der Feder. Zeitsch. f. Naturw., 19, 174-327. 
 Knowlton, F. H. 
 
 1909. Birds of the world, edited by Robert Ridgway. (New York, Holt), 
 xiii +. 873, 16 pis., 233 flgs. in text. 
 Kbukenbekg, C. F. W. 
 
 1881-82. Die Farbstoffe der Fedem. Vergl. Physiol. Studien (Heidel- 
 berg), Reihe I, Abth. 5, 72-92, pi. 3; Reihe II, Abth. 1, 151-171; 
 Reihe II, Abth. 3, 128-137, pi. 9. 
 Mallock, a. 
 
 1911. Note on the iridescent colors of birds and insects. Rep. Smithson. 
 Inst., 1911, 425-432, pis. 1-3. 
 Mascha, B. 
 
 1904. Ueber die Schwungfedern. Zeitsch. f. wiss. Zool., 77, 606-651, 
 
 pis. 29-31, 9 figs, in text. 
 
 1905. The structure of wing feathers. Smithson. Misc. coll., 48, 1-30, 
 
 pis. 1-16. 
 Newton, A. 
 
 1899. A dictionary of birds. (London, Black), xli + 1088, many flgs. 
 in text. 
 
1916J Chandler: Structure of Feathers 395 
 
 NiTZSCH, C. L. 
 
 1867. Pterylography. Edited and revised by H. Burmeister, trans, from 
 the German and edited by P. L. Sclater. Ray Soc. Publ., 10, 
 181, 10 pis. 
 Pabkeb, T. J. 
 
 1891. Observations on the anatomy and development of Apteryx. 
 Philos. Trans. R. Soc. London, 182B, 25-134, pis. 3-9. 
 Pbakl, R. 
 
 1907. Variation and differentiation in CeratopJiyllum. Carnegie Inst. 
 
 Wash. Publ. 58, 1-136, 26 figs, in text. 
 Pbrnitza. 
 
 1871. Bau und Entwickelung der Erstlingfieders. Sitzungsber. Kais. Ak. 
 Wlss. Wien., 43, Abth. 2, 439-449. 
 Ptckaft, W. p. 
 
 1893. The interlocking of the barbs of feathers. Nat. Sci., 3, 197-203. 
 
 1909. A history of birds. (London, Methuen), xxxi + 458, 36 pis., 50 figs. 
 
 in text. 
 Riddle, O. 
 
 1908. The cause of the production of "down" and other downlike struc- 
 
 tures in the plumages of birds. Biol. Bull., 14, 163-175. 
 Sttjbbs, p. J. 
 
 1910. An undescrlbed feather element. Nature, 84, 328. See also p. 436. 
 
 SCHLEIDT, J. 
 
 1913. Ueber Friihstadien der Entwicklung von Schuppe und Feder. 
 Arch. f. mikr. Anat., 83, 118-129, pi. 7. 
 
 SCHBOEDEB, R. 
 
 1880. Pterographische Untersuchungen. Diss. Inaug., Halle. 
 Stehli, G. 
 
 1910. Ueber die Beschuppung der Reptilien. Jen. Zeitsch., 46, 737-801, 
 pi. 28, 19 figs, in text. 
 Stbong, R. M. 
 
 1902. The development of color in the definitive feather. Bull. Harvard 
 
 Mus. Comp. Zool., 40, 147-186, 9 pis. 
 1903a. Iridescent feathers. Science, n. s., 17, 483-484. 
 1903b. Metallic colors of feathers from the side of the neck of the do- 
 mestic pigeon. Mark Anniv. Vol., 263-277, 1 pi. 
 1905. The evolution of color-producing structures in birds. Science, n. s., 
 21, 380-381. 
 Studeb, T. 
 
 1873. Die Entwicklung der Federn. Inaug. Diss., Bern., 29 pp., 2 pis. 
 1878. Beitrage zur Entwlcklungsgeschichte der Feder. Zeitsch. f. wiss. 
 Zool., 30, 421-436, pis. 25-26. 
 Sundevall, C. J. 
 
 1886. On the wings of birds. Ibis, (5), 4, 389-457, pis. 10-11. 
 
 TOLDT, K. JUN. 
 
 1912. Beitrage zur Kenntnis der Behaarung der Saugetiere. Zool. Jahrb., 
 Abt. fur Syst, 33, 9-86, pis. 2-3. 
 
 WiEDEBSHEIM, R. 
 
 1909. Vergleichende Anatomie der Wirbelthiere (Ed. 7; Jena, Fischer), 
 XX + 935, 1 pi., 476 flgs. in text. 
 
396 University of California Publications in Zoology [Vol. 13 
 
 Weay, r. s. 
 
 1887a. On some points in the morphology of the wings of birds. Proc. 
 
 Zool. Soc. London, 1887, 343-357, pis. 29-32, 2 figs, in text. 
 1887b. On the structure of the barbs, barbules and barbicels of a typi- 
 cal pennaceous feather. Ibis, (5), 5, 420-423, pi. 12. 
 
EXPLANATION OF PLATES 
 
 Except as otherwise noted, all figures of barbules are from a 
 typical portion of a typical barb of the feathers it represents, and 
 drawn in lateral view, the distals with their bases to the left, the 
 proximals to the right, and in all cases dorsal side uppermost on the 
 plate. 
 
 PLATE 13 
 
 RmsiroBMES and Struthioniformes 
 
 All figures except 2d, X 85 
 
 Pig. 1. RJiea americana. 
 
 a. Barbule from basal portion of barb from terminal part of remex. 
 i. Barbule from basal third of barb from middle portion of rump 
 
 feather, 
 c. Barbule from middle portion of barb from middle part of remex. 
 
 Pig. 2. Struthio camelus. 
 
 a. Barbule from remex. 
 
 h. Barbule from back feather. 
 
 c. Barbule from black wing covert. 
 
 d. Elongated barb from back feather of chick (neossoptile). X 10. 
 
 e. Barbule from back feather of chick (neossoptile). 
 
 [398] 
 
UNIV, CALIF, PUBL, ZOOL. VOL, 13 
 
 ICHANDLERI PLATE 13 
 
PLATE 14 
 
 Casuarhformbs and Apteryqifoemes 
 
 All figures, except 4o and 56, X 14:0 
 
 Fig. 3. Casuarius papuanus. 
 
 a. Portion of barb from basal portion of contour feather. 
 6. Tips of barbules from same barb. 
 
 Pig. 4. Dromaeus novae-hollandiae. 
 
 a. Tip of naked barb from distal part of contour feather. X 35. 
 B. Proximal and distal portions of barbule from contour feather. 
 
 Fig. 5. Apteryx haasti. 
 
 a. Proximal and distal portions of barbule from back feather. 
 B. Similar barbule. X 85. 
 
 [400] 
 
UNIV. CALIF. PUBL. ZOOL, VOL, 13 
 
 [CHANDLER] PLATE 14 
 
PLATE 15 
 
 Sphbniscifoemes 
 
 Figs. 6a, c, e, X 100, Figs 66, d, and 7a, B, X 185 
 
 Fig. 6. Aptenodytes pennanti. 
 
 a. Distal barbule from near base of barb of back feather. 
 
 B. Same. X 185. 
 
 c. Proximal barbule from near base of barb of back feather. 
 
 a. Same. X 185. 
 
 e. Portion of barb from aftershaft. 
 
 Fig. 7. Eudyptes chrysocome. 
 
 a. Distal barbule from near base of barb of back feather. 
 B. Proximal barbule from same. 
 
 1402J 
 
UNIV. CALIF, PUBL. ZOOL, VOL. 13 
 
 [CHANDLER] PLATE 15 
 
PLATE 16 
 
 COLTMBIFOBMES 
 
 All figures, except 9ft, X 100 
 
 Fig. 8. Oavia immer. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex, pennulum in lateral view. 
 
 d. Proximal barbule from same distal third of barb. 
 
 e. Distal barbule from breast feather. 
 /. Proximal barbule from same. 
 
 Fig. 9. Aecfimophorus occidentalis. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 e. Distal barbule from back feather. 
 /. Proximal barbule from same. 
 
 fir. Distal barbule from back feather, near tip of barb, 
 ft. Portion of barb from breast feather. X 36. 
 
 [404] 
 
UNIV. CALIF. PU8L. 200L. VOL. 13 
 
 [CHANDLER] PLATE 16 
 
PLATE 17 
 
 Frocellakcifobmes 
 
 All figures X 100 
 
 Fig. 10. Diomedea exsulans. 
 
 a. Distal barbule from inner vane of remex. 
 
 &. Proximal barbule from same. 
 
 e. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 e. Distal barbule from outer third of barb of breast feather. 
 
 Fig. 11. Pufflnus griseus. 
 
 a. Distal barbule from inner vane of remex. 
 
 B. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex, distal third of barb. 
 
 Fig. 12. Oceanodroma melania. 
 
 a. Distal barbule from near tip of barb of breast feather. 
 J). Proximal barbule from same. 
 
 [406] 
 
UNIV. CALIF, PUBL, 200L. VOL, 13 
 
 [CHANDLER] PLATE 17 
 
PLATE 18 
 
 SxESAlSrOPODES 
 
 All figures X 100 
 
 Fig. 13. Plotus anMnga. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex, silvery gray portion. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 e. Distal barbule from back feather, silvery gray portion. 
 /. Distal barbule from back feather, black portion. 
 
 jr. Proximal barbule from back feather, about middle of barb. 
 
 Fig. 14. Phalaeocorax penicillatus. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 e. Distal barbule from back feather, velvety portion. 
 /. Proximal barbule from same. 
 
 Fig. 15. Fregata aquila. 
 
 a. Distal barbule from inner vane of remex. 
 
 2). Proximal barbule from same. 
 
 [408] 
 
UNIV. CALIF, PUBL. ZOOL. VOL. 13 
 
 [CHANDLER] PLATE If 
 
PLATE 19 
 
 Steganopodes, continued 
 
 All figures X 100 
 
 Fig. 16. Sula variegata. 
 
 a. Distal barbule from inner vane of remex. 
 
 &. Poximal barbule from same. 
 
 e. Distal barbule from back feather. 
 
 d. Proximal barbule from same. 
 
 Fig. 17. Pelecanus erythrorhynchus. 
 
 a. Distal barbule from inner vane of remex. 
 
 i. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex. 
 
 d. Distal barbule from breast feather, distal third of barb. 
 
 e. Proximal barbule from breast feather, proximal third of barb. 
 
 Fig. 18. Pelecanus californicus. 
 
 a. Distal barbule from back feather, velvety portion. 
 
 Fig. 19. Phaethon flaviventris. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Poximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 e. Distal barbule from breast feather, near tip of barb. 
 /. Proximal barbule from same. 
 
 [410] 
 
UNIV, CALIF, PUBL, ZOOL. VOL, 13 
 
 [CHANDLER | PLATE 19 
 
PLATE 20 
 
 Ardeab and Ciconiae 
 
 All figures X 100 
 
 Pig. 20. Ardea Jierodias. 
 
 a. Distal barbule from Inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 e. Distal barbule from back feather, basal third. 
 /. Proximal barbule from same. 
 
 Pig. 21. Butorides virescens. 
 
 a. Distal barbule from outer vane of remex. 
 
 6. Proximal barbule from same, distal third of barb. 
 
 Pig. 22. Egretta candidissima. 
 
 a. Barbule from "aigrette." 
 
 Fig. 23. Mycteria americana. 
 
 a. Distal barbule from inner vane of remex. 
 
 B. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Distal barbule from breast feather. 
 
 Pig. 24. Leptoptilus dubius. 
 
 a. Distal barbule from inner vane of remex. 
 
 B. Distal barbule from outer vane of remex. 
 
 Fig. 25. Plegadis guarauna. 
 
 a. Distal barbule from inner vane of remex. 
 
 Fig. 26. Guara (Eudocimus) ruber. 
 
 a. Distal barbule from scarlet back feather. 
 
 Fig. 27. Ajaja ajaja. 
 
 a. Distal barbule from back feather. - 
 
 [412] 
 
UNIV. CALIF. PUBL. ZOOL, VOL, 13 
 
 [CHANDLERJ PLATE 20 
 
PLATE 21 
 
 Anseriformbs and Phoenicopteki 
 
 All figures, except 28a and 6, X 100 
 
 Anas platyrfiyncJios. 
 
 Basal portion of barb from inner vane of primary. X 8. 
 
 Portion of ventral part of basal region of barb, from outer vane 
 
 of priniary. X 120. 
 Distal barbule from inner vane of remex. 
 Proximal barbule from same. 
 Pistal barbule from outer vane of remex. 
 Proximal barbule from same, distal third of barb. 
 Distal barbule from outer vane of tail feather. 
 Proximal barbule from same, distal third of barb. 
 Distal barbule from outer vane of violet speculum feather. 
 
 Nettion caroUnense. 
 
 Distal barbule from outer vane of primary. 
 
 Distal barbule from outer vane of green speculum feather. 
 
 Proximal barbule from same, distal third of barb. 
 
 Mareca americana. 
 
 Distal barbule from outer velvety black vane of scapular feather. 
 
 CJiauna cristata. 
 
 Distal barbule from outer vane of remex. 
 6. Proximal barbule from same. 
 
 Fig. 32. Phoenicopterus ruber. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from outer vane of remex, distal third of barb. 
 
 c. Proximal barbule from scapular feather, distal half of barb. 
 
 Fig. 
 
 28. 
 
 
 0. 
 
 
 B. 
 
 
 c. 
 
 
 d. 
 
 
 e. 
 
 
 /• 
 
 
 0- 
 
 
 h. 
 
 
 i. 
 
 Fig. 
 
 29. 
 
 
 0. 
 
 
 6. 
 
 
 c. 
 
 Fig. 
 
 30. 
 
 
 a. 
 
 Fig. 
 
 31. 
 
 
 a. 
 
 [414] 
 
UNIV, CALIF. PUBL. ZOOL, VOL, 13 
 
 [CHANDLER] PLATE 21 
 
PLATE 22 
 
 Faiconiformes 
 
 All figures X 100 
 
 Fig. 33. Qyps fulvus. 
 
 a. Distal barbule from back feather. 
 
 t. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of primary. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 Fig. 34. Gymnogyps californianus. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Same, with pennulum in lateral view. 
 
 c. Proximal barbule from inner vane of remex. 
 
 d. Distal barbule from outer vane of remex. 
 
 e. Proximal barbule from same, distal third of barb. 
 
 Fig. 35. Gypogeranus serpentarius. 
 
 a. Distal barbule from blue-gray scapular feather. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from inner vane of remex. 
 
 d. Proximal barbule from same. 
 
 [416] 
 
UNIV, CALIF, PUBL, ZOOL, VOL, 1C 
 
 [CHANDLER] PLATE 22 
 
■ PLATE 23 
 Falconifobmes (Acclpitres) 
 All figures X 100 
 
 Fig. 36. Falco peregrinus. 
 
 a. Distal barbule from Inner vane of remex. 
 
 b. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex. 
 
 Fig. 37. Falco sparverius. 
 
 a. Distal barbule from inner vane of remex. 
 
 Fig. 38. Buteo iorealis. 
 
 a. Distal barbule from inner vane of remex. 
 
 h. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex. 
 
 Fig. 39. Haliaeetus leucocephalus, 
 
 a. Distal barbule from inner vane of remex. 
 
 &. Proximal barbule from same. 
 
 Fig. 40. Polyborus cheriway. 
 
 a. Distal barbule from inner vane of remex. 
 
 Fig. 41. Falco rusticola. 
 
 a. Distal barbule from back feather. 
 
 6. Proximal barbule from same. 
 
 [418] 
 
UNIV, CALIF, PUBL. ZOOL, VOL, 1C 
 
 [CHANDLER] PLATE 23 
 
PLATE 24 
 
 Galliformes 
 
 All figures X 100 
 
 Pig. 42. Gallus domesticus. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, about middle of length of barb. 
 
 e. Proximal barbule from same, distal fourth of barb. 
 /. Proximal barbule from back feather. 
 
 g. Distal barbule from iridescent green tail plume. 
 
 Fig. 43. Bonasa wmbellus. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex. 
 
 Fig. 44. MeXeagris virginiana. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 Fig. 45. Megapodius cumingi. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from outer vane of remex, distal third of barb. 
 
 Fig. 46. Penelope cristata. 
 
 a. Distal barbule from inner vane of remex. 
 
 Fig. 47. Lagopus lagopus. 
 
 a. Distal barbule from white back feather. 
 
 Fig. 48. Twmix tepurana. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 [420] 
 
UNIV. CALIF. PUBL, ZOOL, VOL, 13 
 
 [CHANDLER] PLATE 24 
 
PLATE 25 
 
 Cetptueiformes 
 
 All figures X 135 
 
 Fig. 49. Tinamus solitarius. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Portion of proximal barbule, from inner vane of remex. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Distal barbule from back feather, black. 
 
 e. Portion of proximal vanule, from breast feather. 
 
 f. Basal portion of down barbule, from back feather. 
 
 [422] 
 
UNIV, CALIF. PUBL. ZOOL. VOL. 13 
 
 [CHANDLER] PLATE 25 
 
 49b 
 
 49c 
 
PLATE 26 
 
 Gkuifoemes 
 
 All figures X 100 
 
 Fig. 50. Orus canadensis. 
 
 a. Distal barbule from inner vane of remex. 
 
 &. Distal barbule from outer vane of remex. 
 
 c. Proximal barbule from same. 
 
 d. Proximal barbule from back featbers. 
 
 e. Distal barbule from breast feather, proximal half of barb. 
 
 /. Barbule, distal or proximal, from breast feather, distal third of 
 barb. 
 
 Fig. 51. Aramus giganteus. 
 
 a. Distal barbule from back feather, proximal half of barb. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from breast feather, about middle of barb. 
 
 d. Proximal barbule from same, about middle of barb. 
 
 e. Barbule, distal or proximal, from breast feather, distal third of 
 
 barb. 
 
 Fig. 52. Rallus oVsoletus. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex. 
 
 d. Distal barbule from breast feather, about end of proximal third 
 
 of barb. 
 
 e. Distal barbule from same, about middle of barb. 
 /. Distal barbule from same, distal third of barb. 
 
 g. Proximal barbule from same, about end of proximal third of barb. 
 h. Proximal barbule from same, distal third of barb. 
 
 [424], 
 
UNIV. CALIF. PUBL. ZOOL, VOL, 13 
 
 [CHANDLER] PLATE 26 
 
PLATE 27 
 
 Gbuifoembs, continued 
 
 All figures X 100 
 
 Pig. 53. Otis tarda. 
 
 a. Distal barbule from inner vane of remex. 
 
 2). Proximal barbule from same. 
 
 c. Distal barbule from back feather. 
 
 d. Proximal barbule from back feather. 
 
 Fig. 54. Psophia viridis. 
 
 a. Distal barbule from inner vane of greater covert. 
 
 B. Proximal barbule from outer vane of greater covert. 
 
 c. Distal barbule from back feather. 
 
 d. Proximal barbule from back feather. 
 
 e. Barbule from iridescent green portion of outer vane of covert. 
 
 Fig. 55. Eurypyga helias. 
 
 a. Distal barbule from inner vane of remex. 
 
 &. Proximal barbule from same. 
 
 c. Distal barbule from back feather. 
 
 d. Proximal barbule from back feather. 
 
 Fig. 56. Cariama cristata. 
 
 a. Distal barbule from back feather, near base of barb. 
 
 Z>. Proximal barbule from same. 
 
 [426] 
 
UNIV. CALIF. PUBL. ZOOL. VOL. K 
 
 [CHANDLER] PLATE 27 
 
PLATE 28 
 
 Laro-limicolab 
 
 All figures X 100 
 
 Fig. 57. Numenius americanus. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal fourth of barb. 
 
 e. Distal barbule from back feather. 
 
 /. Barbule, distal or proximal, from breast feather, distal half of 
 barb. 
 
 Fig. 58. Parra spinosa. 
 
 a. Distal barbule from back feather, near base of barb. 
 
 &. Same, distal third of barb. 
 
 Fig. 59. Phalaropus fuUcarius. 
 
 a. Barbule from breast feather, distal third of barb. 
 
 Fig. 60. Cursorius gallicus. 
 
 a. Distal barbule from inner vane of remex. 
 
 B. Proximal barbule from same. 
 
 c. Distal barbule from breast feather, near tip of barb. 
 
 Fig. 61. Larus occidentalis. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same, distal fourth of barb. 
 
 e. Barbule from breast feather, distal third of barb. 
 
 Fig. 62. Sterna maxima. 
 
 a. Distal barb from outer vane of remex. 
 
 Fig. 63. Uria troille. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Distal barbule from breast feather, near base of barb. 
 
 e. Same, near tip of barb. 
 
 /. Proximal barbule of same, near tip of barb. 
 
 [428] 
 
UNIV. CALIF, PUBL, ZOOL, VOL. 13 
 
 ICHANDLER] PLATE 28 
 
PLATE 29 
 
 Pteroclo-columbae 
 
 All figures, except 67a, X 100 
 
 Fig. 64. Columba livia. 
 
 a. Distal barbule from inner vane of remex, white. 
 
 6. Proximal barbule from same, white. 
 
 c. Distal barbule from outer vane of remex, slate gray. 
 
 Pig. 65. Zenaidura macroura. 
 
 a. Distal barbule from olive brown back feather. 
 
 Fig. 66. MelopeUa asiatica. 
 
 a. Distal barbule from blue-gray covert. 
 
 6. Distal barbule from breast feather, pearl gray. 
 
 c. Proximal barbule from same. 
 
 Fig. 67. Columba fasciata. 
 
 a. Hooklet region of distal barbule from covert. X 480. 
 
 6. Barbule from Iridescent green neck feather. 
 
 Fig. 68. Macropygia tenuirostris. 
 
 a. Distal barbule from rufous under tail covert. 
 
 Fig. 69. Osmotreron vernans. 
 
 a. Distal barbule from olive green covert. 
 
 Fig. 70. Goura coronata. 
 
 a. Distal barbule from inner vane of remex, slate blue. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from back feather, grayish blue. 
 
 d. Proximal barbule from same. 
 
 e. Barbule from loose barb of decomposed crest feather. 
 
 Fig. 71. PterocUs arenarius. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Distal barbule from outer vane of scapular feather. 
 
 c. Proximal barbule from same. 
 
 [430] 
 
UNIV, CALIF, PUBL, ZOOL, VOL, 13 
 
 [CHANDLER] PLATE 29 
 
PLATE 30 
 
 CUCUUFOEMES 
 
 All figures X 125 
 
 Fig. 72. Coccysus americanus. 
 
 a. Distal barbule from Inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Distal barbule from outer vane of remex. 
 
 d. Proximal barbule from same. 
 
 e. Distal barbule from breast feather. 
 /. Proximal barbule from same. 
 
 Fig. 73. Oeococcyx californiamis. 
 
 a. Proximal barbule from glossy green outer vane of remex. 
 
 Pig. 74. Cacatua galerita. 
 
 a. Distal barbule from inner vane of remex. 
 
 1). Proximal barbule from same. 
 
 c. Distal barbule from same. 
 
 d. Proximal barbule from same, distal third of barb. 
 
 Fig. 75. Melopsittacus sp. 
 
 a. Distal barbule from outer vane of remex. 
 
 &. Proximal barbule from same, distal third of barb. 
 
 Fig. 76. Tanygnathus lucionensis. 
 
 a. Distal barbule from yellowish-olive-green back feather. 
 
 Fig. 77. Aprosinictus cyanopygius. 
 
 a. Distal barbule from red belly feather. 
 
 6. Proximal barbule from same. 
 
 [432] 
 
UNIV. CALIF, PUBL, ZOOL, VOL. 1C 
 
 [CHANDLER] PLATE 30 
 
 St S W;;^ 
 
PLATE 31 
 
 CoBAcnFOKMKS (Coraclae and Trogones) 
 
 All figures X 100 
 
 Fig. 78. Coracias afflnis. 
 
 a. Distal barbule from inner vane of remex. 
 
 6. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane of remex. 
 
 Fig. 79. Oeryle alcyon. 
 
 a. Proximal barbule from outer vane of remex, dist-al half of barb. 
 &. Proximal barbule from breast feather. 
 
 Prionotelus temnurus. 
 Distal barbule from Inner vane of remex. 
 Distal barbule from outer vane of remex. 
 Proximal barbule from same, distal third of barb. 
 
 Phaeromacrus resplendens. 
 
 Barbule from brilliant green ornamental upper tail covert. 
 
 Hydrocorax mindanensis. 
 
 Distal barbule from inner vane of remex. 
 
 Proximal barbule from same. 
 
 Distal barbule from outer vane of remex. 
 
 Same, with pennulum In lateral view. 
 
 Proximal barbule from outer vane of remex, distal third of barb. 
 
 Irrisor viridts. 
 
 Distal barbule from Inner vane of remex. 
 
 Proximal barbule from outer vane of remex, distal third of barb. 
 
 Fig. 
 
 80. 
 
 
 a. 
 
 
 6. 
 
 
 c. 
 
 Fig. 
 
 81. 
 
 
 a. 
 
 Fig. 
 
 82. 
 
 
 a. 
 
 
 6. 
 
 
 c. 
 
 
 d. 
 
 
 e. 
 
 Fig. 
 
 83. 
 
 
 a. 
 
 [434] 
 
UNIV, CALIF, PUBL. ZOOL. VOL, 13 
 
 [CHANDLER] PLATE 31 
 
PLATE 32 
 
 CoEAcnFOBMBS. (Striges, Caprimulgi, Cypsell) 
 
 All figures, except 886, c, and d, X 100 
 
 Fig. 84. Buho virginianus. 
 
 a. Distal barbule from inner vane of primary. 
 6. Proximal barbule from same. 
 
 c. Proximal barbule from outer vane, on distal, recurved, tooth-like 
 portion of barb. 
 
 Fig. 85. Aluco pratincola. 
 
 a. Distal barbule from breast feather. 
 
 Fig. 86. Chordeiles virginianus. 
 
 a. Distal barbule from outer vane of remex. 
 
 6. Proximal barbule from same, distal third of barb. 
 
 Fig. 87. Podargus strigoides. 
 
 a. Distal barbule from inner vane of remex. 
 2). Proximal barbule from same. 
 
 Fig. 88. Selasphorus rufus. 
 
 a. Distal barbule from outer vane of primary. 
 
 6. Same, X 275. 
 
 c. Proximal barbule from outer vane of primary. X 275. 
 
 d. Proximal barbule from iridescent flery-red gorget feather. X 275. 
 
 [436] 
 
UNIV. CALIF. PUBL. ZOOL. VOL. 13 
 
 [CHANDLER] PLATE 32 
 
PLATE 33 
 
 PiCI AND PASSEMFOKMBS 
 
 All figures, except 95a, X 125 
 
 Melanerpes formicivorus. 
 
 Distal barbule from inner vane of remex. 
 
 Proximal barbule from same. 
 
 Distal barbule from outer vane of remex. 
 
 Proximal barbule from same, distal third of barb. 
 
 Rhamphastus ariel. 
 
 Distal barbule from back feather. 
 
 Jacamerops grandis. 
 
 Distal barbule from Inner vane of remex. 
 Distal barbule from outer vane of remex. 
 Proximal barbule from same, distal third of barb. 
 
 Cyanocitta stelleri. 
 
 Distal barbule from inner vane of remex. 
 
 Proximal barbule from same. 
 
 Distal barbule from outer vane of remex. 
 
 Proximal barbule from same. 
 
 Distal barbule from breast feather. 
 
 Proximal barbule from same. 
 
 Myiarchus cineraseens. 
 
 Proximal barbule from outer vane of remex, distal half of barb. 
 
 Pipilo maculatus. 
 
 Distal barbule from inner vane of remex. 
 
 Fig. 95. Bomiycilla garrula. 
 
 a. Tip of covert feather, with "wax tip". X 7. 
 
 Fig. 
 
 89. 
 
 
 a. 
 
 
 6. 
 
 
 c. 
 
 
 d. 
 
 Fig. 
 
 90. 
 
 
 a. 
 
 Fig. 
 
 91. 
 
 
 a. 
 
 
 6. 
 
 
 c. 
 
 Fig. 
 
 92. 
 
 
 a. 
 
 
 6. 
 
 
 c. 
 
 
 d. 
 
 
 e. 
 
 
 f. 
 
 Fig. 
 
 93. 
 
 
 a. 
 
 Fig. 
 
 94. 
 
 
 a. 
 
 [438] 
 
UNIV. CALIF. PUBL. ZOOL. VOL. 13 
 
 [CHANDLERI PLATE 33 
 
PLATE 34 
 
 Types of Down Barbules 
 
 Entire barbules drawn X 40; portions of barbules marked in parenthesis 
 drawn enlarged, X 285. 
 
 Fig. 96. 8pJieniscu8 mendiculatus. 
 
 a. Entire barbule. 6. same, enlarged. 
 
 Fig. 97. Pufflnus griseus. 
 
 a. Entire barbule. b. basal portion, c. terminal portion. 
 
 Fig. 98. 8ula variegata. 
 
 a. Entire barbule. 6. same, enlarged. 
 
 Fig. 99. Plotus anhinga. 
 
 a. Entire barbule. &. basal portion, c. terminal portion. 
 
 Fig. 100. Botaurus lentiginosus. 
 
 a. Entire barbule. D. basal portion, c. terminal portion. 
 
 [440] 
 
UNIV. CALIF, PUBL. ZOOL, VOL, K 
 
 [CHANDLER | PLATE 34 
 
PLATE 35 
 
 Types of Down BAKBtrLES, continued 
 
 Entire barbules drawn X 40; portions of barbules marked in parentbesis 
 drawn enlarged, X 285. 
 
 Fig. 101. Guara rubra. 
 
 a. Entire barbule. 6. basal portion, c. terminal portion. 
 
 Fig. 102. Phoenicopterus ruber. 
 
 a. Entire barbule. 6. basal portion, c. terminal portion. 
 
 Fig. 103. Olor columbianus. 
 
 a. Entire barbule. b. basal portion, c. terminal portion. 
 
 Fig. 104. Mergus americanus. 
 
 a. Entire barbule. 6. basal portion, c. distal portion. 
 
 Fig. 105. Falco sparverius. 
 
 a. Entire barbule. 6. basal portion, c. middle portion, d. terminal 
 portion. 
 
 [442] 
 
UNIV, CALIF. PUBL, ZOOL, VOL, i; 
 
 [CHANDLER] PLATE 35 
 
PLATE 36 
 
 Types op Down Barbxtles, continued 
 
 Entire barbules drawn X 40; portions of barbules marked by parenthesis 
 drawn enlarged, X 285. 
 
 Fig. 106. Eurypyga helias. 
 
 a. Entire barbule. 6. basal portion, c. terminal portion. 
 
 Fig. 107. Ballus ohsoletus. 
 
 a. Entire barbule. 6. basal portion, c. terminal portion. 
 
 Fig. 108. Meleagris virginiana. 
 
 a. Entire barbule from distal vanule near base of barb. 
 &. Basal portion, c. middle portion, d. terminal portion. 
 
 Fig. 109. Zenaidura macrowra. 
 
 a. Entire barbule from near base of barb. 
 
 Z). Basal portion, c. middle portion, d. terminal portion. 
 
 [444] 
 
UNIV, CALIF, PUBL, ZOOL. VOL, 13 
 
 [CHANDLER] PLATE 36 
 
PLATE 37 
 
 Types of Down Babbitles, continued 
 
 Entire barbules drawn X 40; portions of barbules marked by parenthesis 
 drawn enlarged, X 285. 
 
 Fig. HO. Momotus lessoni. 
 
 a. Entire barbule. &. basal portion, c. terminal portion. 
 
 Fig. 111. Hydrocorax mindanensis. 
 
 a. Entire barbule. &. basal portion, c. terminal portion. 
 
 Eugenes fulgens. 
 
 Entire barbule from near base of barb. 
 
 Basal portion, c. distal portion. 
 
 Rhamphastus ariel. 
 
 Entire barbule from near base of barb. 
 
 Basal portion, c. terminal portion. 
 
 Pipilo maculatus. 
 
 Entire barbule from near base of basal barb. 
 
 Basal portion, c. terminal portion. 
 
 Fig. 115. Corvus coram. 
 
 a. Entire barbule from near base of basal barb. 
 &. Basal portion. 
 
 Fig. 
 
 112. 
 
 
 a. 
 
 
 6. 
 
 Fig. 
 
 113. 
 
 
 a. 
 
 
 B. 
 
 Fig. 
 
 114. 
 
 
 a. 
 
 
 6. 
 
 [446] 
 
UNIV, CALIF, PUBL, ZOOL, VOL, 13 
 
 [CHANDLER] PLATE 37 
 
UNIVEBSITY OF CAMFOKNIA PUBLICATIONS— (Oofltiiiued) 
 
 EOOIidOT. Vol. 12 (Continued) 
 
 13. Bepoit 'aiKtn Mammals and Birds found in Portions of Tiinlty, , 
 
 Siskiyou !|,nd Sliasta Counties, Calif onda, by; Louise Kellogg. . Pp. 
 S86-398, iftates 15-18.; 
 
 14. An AnslyMs of tbe VerteT>iate Panna of tlie Trinity Begion of 
 
 Northern California, by Joseph OrinneU. Pp.. S99-110. : 
 
 Nos. 13 and 14 in one cover. January, 1916 ,._.. . .76 
 
 r Vol. 13. 1. The Sddzopeda Of thfr San Slego Region, by Calvin O. Esterly. 
 
 Pp. 1-20, plates 1-2. April, 1914.._...„... , : .15 
 
 2. A Study of the Occurrence and Manner of Distribution of ^ the 
 
 Otenophora of the San Diego Region, by Calvin O. Esterly. Pp. 
 21-38. April. 1914. ,„„..-. _ .16 
 
 3. A New Self-Regnlattng Paraffin Bath, by C. W. Woodworth. Pp. 
 
 39-42, 2 text figures, April, 1914. .,... .06 
 
 4. Diplodimwrn ecaudatum, with an Account of Its Neuromotor Ap- 
 
 paratus, by Robert 0. Sharp. Pp. 43-122, plates 3-7, 4 text figures. 
 
 Ma3^ 1914 ...: ; .: .::... _„ _. 80 
 
 6. The "Vtertical Distribution and Movements of the Schlzopoda of .the. 
 
 San Diego Region, by Calvin O. Esterly. Pp. 123-145.^ May, 1914 .20 
 
 6. The An&tomy of Beterodontus frdnoiset: I. The Exoskeleton, by 
 
 J. Frank Daniel. Pp. 147-166, plates 8-9, 4 text figures. May 23, 
 ' 1914 .., : : .20 
 
 7. The Movements and Reactions of the Isolated Melanophores of the 
 
 Frog, by 8. J. Holmes. Pp. 167-174, plate 10. August, 1914. ._ .10 
 
 8. PolyOha^tQUS Annelids of the Pacific Coast in the Collections of the 
 
 Zoological Museum of the tlntrerslty of California, by Aaron L. 
 Treadweli. Pp. 176-234, plates U-l2. 
 
 9. New Syllldae from San Francisco Bay (collected by the U. S. S. 
 
 ' 'Albatross' 'y, by Aaron L. Treadweli. Pp. 236-238, 7 text figiares. 
 
 Nos. 8 and 9 In one cover. October, 1914.. - - 66 
 
 10. Note on the Medusan Cl«nus Btomolophus, from San Diego, by 
 
 Henry B. Blgelow. Pp. 239-241. September, 1914..—...; 05 
 
 11. A Study of the Structure of Feathers, with Reference to Their 
 
 Taxonomic Significance, by Asa C. Chandler. Pp. 243-446, plates 
 13-37. April, 1916 .._ ., 2.00 
 
 12. Anatomical Adaptations in the Thoracic Limb of the CaUfomia '-^ 
 
 Pocket Oopher and Other Rodents, by Charles Daniel HoUlger. 
 
 Pp. 447-494, plates 38-39, 20 text figures. March, 1916.... 45 
 
 Vol. 14. 1. A Report upon the Physical Conditions In San Francisco Bay, Based 
 .a|ion the Operations of the United States Fisheries Steamer "Al- 
 batross" during the Tears 1912 and 1913, by F. B. Sumner, Q-. 
 
 D. Louderback, W. L. Schmltt, and E. C Johnston. Pp. 1-198, 
 plates 1-13, 20 text figures. July, 1914 „ _ 2.26 
 
 Vol. 16. 1. Hydrographlc, Plankton, and Dredging Records of the Scrlpps In- 
 sUtutioil for Biological Research of the University of California, 
 1901 to 1912, compiled and' arranged under the supen^on of W. 
 
 E. Ritter by Ellis L. Michael and Oeorge F. McEwen. Pp. 1-206, 
 
 4 text figures and map. July, 1915 ._ „_. 2.25 
 
 VoL 16. 1. An Outline of the Morphology and Life-History of CritMdia lepto- 
 . coridis, sp. nov., byJErene McCuHoch. Pp. 1-22, plates 1-4, 1 text . 
 figure. September, 1915 .._..^....:. ._ , :...._ .25 
 
 2. On. Oiardia microti sp. nOvr, from the .Meadow idfonse, by Charles 
 
 Atwood Kofoid^ and Elizabeth Bohn Christiansen. Pp. 23-29, 1 '^ 
 figure in text. 
 
 3. On Binary and Mulldple Fission lii Oiardia muris (Grass!) , by 
 
 Charles Atwood Kofold and EUzabeth Bohn Christiansen. Pp. 
 80-54, plates 5<8,1 figure in text. . 
 
 Nos. 2 and 3 in one OOver. November, 1915 ,80 
 
 4. Thd Cultivation of Tissues from Amphibians, by John O. Johnson. 
 
 Pp. 65-62, 2 figures in text November, 1915... :_. ..... .10 
 
 5. Notes on ;*Hntinnoina. 1. On the Probable Origin of Dictyocyita : 
 
 tiara Haeckel. 2.. On Petalotricha entzi sp. nov., by Charles 
 Atwood Kofold.. Pp. 63-69, 8 figures in text. December, i916..„- ^ .06 
 
TTNIVJERSITY or OAIiIPOEKriA PUBIIOATIONB— (Ooatinued) 
 ZPQIiOOT, Vol 16 (Continued) - % 
 
 6. Biliary and niultiple Fission in Hea»{mitu«,1>7 OUve Swn^y. FPi Ti- 
 
 gs, plates 9-11^ , " . 
 
 7. On a ir^v -Tricbomonad Flagellate, Trichamitus parmu, tTom Xb» 
 
 Intestine of Amphibians, bjr Olive gweay. Pp. 89-94) J^Ute 12. 
 
 Nos. 6 and 7 m one cover. December, 1915....: ...... „ M 
 
 8. On Blepharocorya equi sp. nov., a ITew Oiliate from tbe Oaecnm Of 
 
 the Horse, by Xnvln C.Schumacber. Fp. 96-106, plate 13. De- 
 cember, 1915 .. ...... .. .'. _. . .„.. 40 
 
 9. Three New Helices from Calif ornia, by S. StillmaA Berry. Pp. 107- 
 
 lil. Jimuary, 1916 ., ; ^_ .05 
 
 10. On Trypanosoma triatomae, A New FlaKelU|iV from a Hemiptenui 
 
 Bug itom the Nests of the Wood Bai Neotomd fuadpes, by 
 Charles Atwood Kof old and Irene McCuUoch. Pp. 113-186, plates 
 14^15. February, 1916 „..._ ..„.. ,16 
 
 11. The deneia, Monacercomonaa and Polymastia by Olive Swesy.- Pp. -^ 
 
 127-138, Plates 16-17. February, 1916........................ ,. ..„ .10 
 
 12. Notes on the Spiny Lobster (TamMru^ interruptus) of the Cali- 
 
 fornia Coast,, by Bennet M. Allen. Pp. 139-162^ March, 1916i .15 
 
 13^ Notes on Harine Fishes of Calif omla, by Carl I,. Hubbs. Pp. 163-^ 
 
 : , 160, plates 18-20. March, 1916 ;......... ., ...;.....:. ,16 
 
 14. Thto Feeding, Habits and Food of Pelagic Copepods and the Ques- 
 tion of Nutrition by Oxgaide Substances in Solution In ttte 
 Water, by Calvin 6. Bsterly.Pp: 171-184. March, 1916.;. .„. . .ijB 
 
M^.-..^ 
 
 
 
 -#ISi^^ 
 
 .kf^ 
 
 S¥^^ 
 
 -^ 
 
 
 .a^i