NATURE 



169 



THURSDAY, DECEMBER 22, it 



GEGENRAUR'S COMPARATIVE ANATOMY 



OF THE VERTEBRATA. 

 Vergleichende Anatomie der Wirbelthiere : mii Beriiclc- 

 sic/itigun^ der Wirbellosen. Von Carl Gegenbaur. 

 Erster Band. Einleitung, Integument, Skeletsystem, 

 Muskelsystem, Nervensystem und Sinnesorgane. Mit 

 619 Zum. Theil faibigen Figuren im Text. Pp. .xiv 

 + 97S. (Leipzig : Wilhelm Engelmann, 1898.) 



THE first volume of the long-expected work by the 

 master has appeared. By placing the study of 

 anatomy upon the basis of evolution he had become the 

 founder of modern comparative anatomy, and he has 

 raised the building to a great extent by his own hands, 

 supported by a school of disciples, ever increasing through 

 his stimulating and correcting influence. 



No wonder that for years expectation has been keen 

 about this book, which must necessarily be the crowning 

 of his life's work. The present volume, besides an intro- 

 duction, deals with the tegumentary, skeletal, muscular 

 and nervous systems, and the sense organs. 



It would be a hopeless attempt here to give anything 

 ike an adequate resume of the nearly 1000 pages of this 

 first volume. Only some of the salient features can be 

 touched upon. The plan is grand ; the execution can be 

 fully appreciated only by those who have made com- 

 parative anatomy their special study, because the treat- 

 ment frequently soars to such heights that the enormous 

 amount of detail which is marshalled in the book, almost 

 seems to disappear before the generalising ideas into 

 which the facts have been welded and condensed. This 

 is especially the case with the introductory chapters 

 prefacing, or the summarising retrospects following upon, 

 the principal chapters. But this does not make easy 

 reading, and some of the sentences, although containing 

 beautifully conceived ideas, are so idiomatic and so terse 

 as to appear almost oracular. For instance, he discusses 

 the de\elopment of the bird's wing, how the quills grow- 

 ing upon the patagium, and gaining preponderance over 

 it, have become the functional wing surface, wliile the 

 patagium itself loses its importance and becomes corre- 

 spondingly reduced. The result of this contemplation is 

 summed up thus : " Das Product tritt functionell an die 

 Stelle des Bodens, auf dem es entstand." 



The general introduction alone, taking up the first 

 seventy pages, is an ideal treatise of morphology, dealing 

 with such fundamental questions as adaptation, correla- 

 tion, differentiation, inheritance, ontogeny with reference 

 to phylogeny, value and meaning of the germinal 

 layers, &c. 



A characteristic feature, going like a red thread through 

 the whole book, is the animosity against ontogenetic 

 research so far as that is in the hands of those whom our 

 author speaks of as embryographers. According to him 

 the ontogenetic record is of no use unless it is in full 

 concord with the results arrived at by the comparative 

 anatomical method, and not many opportunities are 

 missed which afford a stab at ontogeny where this has 

 failed to elucidate a certain problem. The embryo- 

 grapher will, therefore, feel inclined to smile when he 

 NO. 1521, VOL. 59] 



comes across the not unfrequent passages where, 

 palaeontology remaining mute and comparative anatomy 

 revealing nothing, the problem in question is summarily 

 dismissed as one fit for the ontogenetic method. 



Another leading feature is the striving to derive any 

 given organ from something else, from another one pre- 

 viously existing, instead of being satisfied with its origin 

 /// situ. Of course this is the true scientific, evolutionary 

 method, and it is the very one by which Gegenbaur's 

 works have become epoch-making ; but occasionally the 

 idea seems to be a little overdone, and it is then not 

 always easy to reconcile the various arguments with each 

 other. For instance, in the discussion of great im- 

 portance, pp. 590-592, which runs approximately as 

 follows ; 



It is more reasonable to derive cartilaginous parts from 

 other existing cartilage, although their ontogeny may show 

 them to make their appearance where they are wanted 

 in the organism. Thus it is, for instance, preferable to 

 assume the derivation of the Cyclostomes' gill-basket 

 from the cranial cartilage, instead of believing that this 

 basket-work has originated in situ. " It is (p. 590) very 

 probable that the whole of the cartilaginous skeleton took 

 its origin from the perichordal cartilage." 



All this is certainly very satisfactory and uniform, but as 

 the author himself has pointed out on p. 200, it is becoming 

 more and more plausible that theoriginal home of cartilage 

 was in the integument, in the ectoderm. Its appearance 

 in the perichordal neighbourhood would in this case be a 

 secondary feature, owing to chondroid infiltration into 

 the connective tissue. But if this is so, then there would 

 be nothing unreasonable in the assumption that the gill- 

 basket of the Lamprey had received its cartilage in situ. 

 We do not want to press this derivation, but it seems 

 unfair categorically to ask (p. 591) : 



" What business has a cell, or even a group of cells, to 

 transform itself here or there into cartilage .'' One or a 

 few cells, even when they become cartilaginous, do not 

 yet possess a supporting function ; at any rate the causal 

 momentum of this transformation would remain obscure, 

 as the result of the transformation cannot at the same 

 time be its cause." 



This certainly sounds very uncompromising, but the 

 mystery of the origin of the cartilage is not solved by 

 deriving it from other cartilage. The same consideration 

 applies to the derivation of bone, and our author makes 

 the following statement, p. 594 : 



" Indem wir das knocherne .Skelet nicht mehr ausschliess 

 lich vom Bindegewebe ableiten, durch an sich unver- 

 staendliche, weil in ihren Causalmomenten nicht darzule- 

 genden VeraenderungenjenesGewebe andenbetreffenden 

 Orten entstanden unsvorstellen, sondern den wesentlich- 

 sten Antheil bei seiner Entstehung in den Osteoblasten 

 finden, werden die ersten Anfaenge der Hautskeletbildung 

 (Selachier) mit den hoechst verwickelten Zustaenden des 

 Skeletes der Wirbelthiere aufs innigste verkniipft." 



The sentence just quoted, rather typical of the style, 

 defies direct translation, but its sense may perhaps be 

 rendered as follows : By referring the most essential 

 share in the formation of the bony skeleton to the 

 osteoblasts, we are enabled to connect intimately the 

 first beginnings of the dermal skeletal formation (of 

 Selachians) with the highly differentiated condition of the 

 skeleton of the higher Vertebrata. We no longer derive 



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