-s 



liWl 



SCIENCE 



lEntered at ihe Pos -Ofl o i of New York, N.V., as Second-Class Matter.] 



A WEEKLY NEWSPAPER OF ALL THE ARTS AND SCIENCES. 



Eighth Year. 

 Vol. XVI. No. 407 



NEW YORK, NovK.MBER 21, 1890. 



Single Copies, Ten Cents. 

 $3.50 Peb Year, in Advance. 



THE PROBLEMS OF COMPARATIVE OSTEOLOGY.' 



Osteology is the study of the bones or the skeleton of verte- 

 brates. Cnmparaiive osteology ij the study of the origin and 

 evolution of the different modifications of the skeleton. It could 

 also be called '■ moriihology of the skeleton " It not only regards 

 the living forms alone, but considers the fossil forms exactly in 

 the same way. As we know nothing but the skeleton of the ex- 

 tinct vertebrates, comparative osteology becomes the real basis of 

 vertebrate pbylogeny. All our systems of vertebrates have to be 

 founded on characters derived from the skeleton. It is quite evi- 

 dent, therefore, that comparative osteology is one of the most 

 important branches of vertebrate morphology. It alone enables 

 ns to give an exact and scientific explanation of the origin and 

 €volution of vertebrates, and so it is the real foundation of the 

 morphology of these animals. 



Comparative osteology may be divided into three branches : 1. 

 Osteology of the living forms; 3. Osteology of the extinct forms; 

 Z. Evolution of the skeleton. 



It is the task of the first-named branch — osteology of the living 

 forms — to study the skeleton of the living forms in as com- 

 plete a manner as possible., A characteristic genus of each 

 faraily ought to be examined, and the characters of the families 

 given on this basis. It especially regards such groups of animals 

 as are very isolated tn-day, and of the origin of which we know 

 very little or nothing through paleontology. Such animals are, 

 for instance, the Monotremata. the ostriches, chameleon, Necturus, 

 Hippocampus. At the same time it aims to study with great 

 oare such forms as in former periods must have been abundant, 

 and which are represented to day, perhaps, by a single genus only. 

 Such forms are Hyrax, Apteryx, Sphenodon, Polyptenis, Cerato- 

 dus, and many others. 



There are different ways to work in this branch. One man 

 may give a most complete osteology of a single form, for instance, 

 the chicken; but this purely descriptive work will be of little sci- 

 entific value in itself, though it vs-ill become valuable for him who 

 gets the philosophy out of it, and who traces the relations and 

 origin of the form described. Notwithstanding, such work is very 

 often important, if forms which are very rare or difificult to get 

 are treated in this way. A pure description, for instance, of the 

 osteology of the peculiar tortoise Carettochelys from New Guinea, 

 would be very important, because it would enable us to give the 

 correct systematic position to this form. Of the greatest impor- 

 tance is the study of osteological variations in a genus or a species. 

 Darivin's publications in this direction are known to everybody, 

 and Nehring in Germany has devoted much time to it. Such re- 

 searches ought to be undertaken oftener, as they are of the greatest 

 value for the explanation of the origin of species. Another man 

 may study all the sknlls of the members of a family, or an order, 

 or a class, or even of all living vertebrates, and thus gi>e a com- 

 plete history of the osteology of the skull ; or he may treat the 

 veitebrse, the sboulder-girdle, the pelvis, the limbs, in the same 

 way. Such researches are extremely important; but, by consider- 

 ing one part of the skeleton alone, it may happen that parallel 

 forms may be considered as nearly related which in fact have 

 nothing whatever to do with each other 



* Abstract of a lecture givea by Dr. G, Baur at Clark Univerdlty, Worcester, 

 Mass., Oct, 17, 1890, 



It is by this method of study that the great homologies of the 

 skeleton have been worked out Of course, the time of the 

 archetype idea of the skeleton belong;; now to the past, or nearly 

 so; but it has been followed by a time which has gone a step too 

 far with its tendency to homologize every thing. In this, great 

 care is necessary. There are elements and formations which have 

 nohomologues. 1 recall the interparietal of mammals. This bone 

 appeared in the mammalian line, doubtless produced by the in- 

 crease of the brain. It is a new formation in the special branch 

 of mammals which has no homologue among lower vertebrates. 

 When the predentary bone was found in iguanodon, a homologue 

 was eagerly searched for; but this bone is a new formation in the 

 peculiar grnup of Orthopoda to which iguanodon belongs, and has 

 no homologue among lower forms, I could multiply these exara- 

 ple.;' (the tympanic of mammals belongs here, for instance), but I 

 will mention only one other case. There is much said at present 

 about hexa or hepta-dactylism of the mammalian hand, homo- 

 logues for the additional digits are looker! for among fishes, and 

 we hear about the polydactyl ancestors of mammals; but it is for- 

 gotten that mammals came fjom pentadactyl reptiles, and reptiles 

 from pentadactjl batrachians, and that these rudimentary addi- 

 tional digits in mammals are simply of recent independent origin, 

 and have no homologues. The same is true of the polydactyl 

 forms of ichthyosaurs, of the liexadactyl hind-limb of frogs, and 

 of all higher vertebrates with poly phalangeal digits, as the 

 Plesiosauria , MosttaaurictoE, Sirenia, Cefacea. It is by studying 

 only one part of the skeleton, without consideration of the others, 

 that such mistakes in homology are made. So it is that the fins 

 cf ichthyosaurs were considered for a long time, and by some 

 still to-day, as forming the missing link between fishes and rep- 

 tiles 



A third man may study the osteology of a group of vertebrates as 

 a whole; for instance, the ungulates, or t'le parrots, or the croco- 

 diles, or salmons. He will compare all Ihe skulls, the limbs, the 

 vertebrae and so on, of such a group, trying to trace the origin 

 and relation of its members. He will have a big task, but he will 

 get nearest to the truth. But even if he should study the skulls 

 of all living species of vertebrates, or the copitlete osteology of 

 all living forms, his general results on origin and affinity of the 

 different groups would be very incomplete. 



Here paleontology comes in with a helping hand. I mean true 

 morphological vertebrate paleontology, not that old " geological'' 

 paleontology. Paleontology of vertebrates, when studied without 

 anatomical knowledge, is of no use : in this case it is generally 

 nothing more than a lumber room of names of so-called new 

 species or genera, mostly based on insignificant fragments or 

 specimens insufficiently described. That old paleontology should 

 be abolished entirely. A geologist ought to remain in his own 

 domain, geology, and leave paleontology alone, if he is not, what 

 is seldom the case, a thorough anatomist. This is true also of 

 invertebrate paleontology. The splendid publications of Hyatt, 

 Jackson, Beecher, and Clarke, for instance, are writtrn from 

 this standpoint. Vertebrate paleontology is nothing but a 

 branch of comparative osteology, which in itself belongs to 

 vertebrate morphology. It is very remarkable that the museums 

 of natural history are not arranged according to this natural sys- 

 tem. Here we find with one exception (the Museum of the Royal 

 College of Surgeons of LondonJ the bones of extinct animals 



