Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/857

ZOOLOGY 807 distinguish Cuvier. Another special distinction of Cuvier is his remarkable work in comparing extinct with recent organisms, his descriptions of the fossil Mammalia of the Paris basin, and his general application of the knowledge of recent animals to the reconstruction of extinct ones, as indicated by fragments only of their skeletons. It was in 1812 that Cuvier communicated to the Academy of Sciences of Paris his views on the classification of animals. He says Si Ton considers le regne animal d apres les principes quo nous venous de poser, en se debarassant des prejuges etablis sur les divisions ancieimement admises, en n ayant egard qu a 1 organisa- tion et a la nature des animaux, et non pas a leur grandeur, a leur utilite, au plus on moins de connaissance que nous en avons, ni a toutes les autres circonstances accessoires, on trouvera qu il existe quatre formes principales, quatre plans generaux, si Ton peut s ex- primer ainsi, d apres lesquels tons les animaux semblent avoir ete modeles et dont les divisions ulterieures, de quelque titre que les naturalistcs les aient decorees, ne sont que des modifications assez legeres, fondees sur le developpement, ou 1 addition de quelques parties qui ne changent rien a 1 essence du plan." His classification as finally elaborated in Le Regne Animal (Paris, 1829) is as follows : First Branch. Animalia Vertebrata. Class I. MAMMALIA. Orders : Bimana, Quadrumana, Carnivora, Marsupialia, Rodcntia, Edentata, Pachydermata , Rumin-antia, Cctacea. Class II. BIRDS. Orders : Accipitres, Passcrcs, Scansorcs, Gallinse, Grallie, Palmipedes. Class III. REPTILIA. Orders : Oftelonia, Sauria, Ophidia, Batradiia. Class IV. FISHES. Orders : (a) Acanthoptcrygii, AMominales, Subbrachii, Apodcs, Lopliobraiicliii, Plcctoynathi ; (b) Sluriones, Scl- achii, Cydostomi. Second Branch. Animalia Mollusca. Class I. CEPHALOPODA. Class II. PTEROPODA. Class III. GASTROPODA. Orders : Pulmonata, Nudibranchia, Infcrobranchia, Tccti- branchia, Hdcropoda, Pcctinibranchia, Tubulibranchia, Scut ibranchia, Cydobranchia. Class IV. ACEPHALA. Orders : Tcstacca, Tunicata. Class V. BRACHIOPODA. Class VI. CIRRHOPOUA. Third Branch. Animalia Articulata. Class I. ANNELIDES. Orders : Tubicolae,, Dorsibmndiiee, Abranckise. Class II. CRUSTACEA. Orders : (a) Malacostraca : Dccapoda, Stomapoda, Am- pkipoda, Ltemodipoda, Isopoda ; (b) Entomostraca : Uranckiopoda, Pcceilopoda, Trilobitee. Class III. ARACHNIDES. Orders : Pulmonarias, Trochcarisz. Class IV. INSECTS. Orders : Myriapoda, Thysanura, Parasita, SiKtoria, Colco- ptcra, Orthoptcra, Hcmiptera, Ncitropterti , Hynunoptcra, Lepidoptf.ra, likipi ptcra, Diptcra. Fourth Branch. Animalia Radiata. Class I. ECHIXODEKMS. Orders : Pcdicdlata, Apoda. Class II. INTESTINAL WORMS. Orders : Ncinatoidea, Parcnchymatosa. Class III. ACALEPH^E. Orders : Simpliccs, Hydrostaticie. Class IV. POLYPI (including the Cidentcra of later authori ties and the Polyzoa). Orders : Carnosi, Gclatinosi, Polypiaril. Class V. INFUSORIA. Orders : llotifcra, Ifomogenca (this includes the Protozoa of recent writers and some Protophyta}. The leading idea of Cuvier, his four embranchemem, was confirmed by the Russo- German naturalist Von /on Baer. Baer (1792-1876), who adopted Cuvier s divisions, speak ing of them as the peripheric, the longitudinal, the mass ive, and the vertebrate types of structure. Von Baer, however, has another place in the history of zoology, being the first and most striking figure in the introduc tion of embryology into the consideration of the relations of animals to one another. Cuvier may be regarded as the zoologist by whom The mor- anatomy was made the one important guide to the under- 1 holo- standing of the relations of animals. But it should be gists noted that the belief, dating from Malpighi (1670), that there is a relationship to be discovered, and not merely a haphazard congregation of varieties of structure to be classified, had previously gained ground. Cuvier was familiar with the speculations of the "Natur-philosophen," and with the doctrine of transmutation and filiation by which they endeavoured to account for existing animal forms. The noble aim of F. W. J. Schelling, " das ganze System der Naturlehre von dem Gesetze der Schwere bis zu den Bildungstrieben der Organismus als ein organisches Ganze darzustellen," which has ultimately been realized through Darwin, was a general one among the scientific men of the year 1800. Lamarck accepted the develop ment theory fully, and pushed his speculations far beyond the realm of fact. The more cautious Cuvier adopted a view of the relationships of animals which, whilst denying genetic connexion as the explanation, recognized an essen tial identity of structure throughout whole groups of ani mals. This identity was held to be due to an ultimate law of nature or the Creator s plan. The tracing out of this identity in diversity, whether regarded as evidence of blood-relationship or as a remarkable display of skill on the part of the Creator in varying the details whilst re taining the essential, became at this period a special pur suit, to which Goethe, the poet, who himself contributed importantly to it, gave the name "morphology." C. F. Wolff, Goethe, and Oken share the credit of having initi ated these views, in regard especially to the structure of flowering plants and the Vertebrate skull. Cuvier s doctrine of four plans of structure was essentially a morphological one, and so was the single-scale doctrine of Buffon and Lamarck, to which it was opposed. Cuvier s morphologi cal doctrine received its fullest development in the prin ciple of the " correlation of parts," which he applied to palaeontological investigation, namely, that every animal is a definite whole, and that no part can be varied without entailing correlated and law-abiding variations in other parts, so that from a fragment it should be possible, had we a full knowledge of the laws of animal structure or morphology, to reconstruct the whole. Here Cuvier was imperfectly formulating, without recognizing the real phy sical basis of the phenomena, the results of the laws of heredity, which were subsequently investigated and brought to bear on the problems of animal structure by Darwin. Richard Owen l may be regarded as the foremost of R. Owen Cuvier s disciples. Owen not only occupied himself with the dissection of rare animals, such as the Pearly Nautilus, Lingula, Limulus, Protopterus, Apteryx, ttc., and with the description and reconstruction of extinct Reptiles, Birds, and Mammals, following the Cuvierian tradition, but gave precision and currency to the morphological doctrines which had taken their rise in the beginning of the cen tury by the introduction of two terms, "homology" and Homo- " analogy," which were defined so as to express two lo gy anfl different kinds of agreement in animal structures, which, ;u owing to the want of such "counters of thought," had been hitherto continually confused. Analogous structures in any two animals compared were by Owen defined as structures performing similar functions, but not necessarily derived from the modification of one and the same part in the "plan" or " archetype " according to which the two animals compared were supposed to be constructed. Homologous structures were such as, though greatly dif fering in appearance and detail from one another, and though performing widely different functions, yet were 1 Born in 1804 hi Lancaster ; conservator of the Hunteriau Museum,

London, 1830-56; superintendent Nat. Hist. Brit. Mus., 1856-84.