Botany and Zoology. , 125 



of the fore-arm or pectoral limb, which bones were long and slender, 

 like those of the bat; and one of the fingers, answering lo our little 

 finger, was enormously elongated. The wings of the little Draco 

 volant, the species which now flits about the trees of the Indian tropics, 

 were supported by its ribs, which were liberated from an attachment to 

 a sternum, and were much elongated and attenuated for that purpose. 



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91 



The wing of the pterodactyle was analogous to the wing of the Draco 

 inasmuch as it had a similar relation of subserviency to flight; but it 

 was not homologous with it, inasmuch as it was composed of distinct 

 parts. The true homologue of the wing of the pterodactyle was the 

 foreleg of the little Draco volans. 



The recognition of the same part in different species, Prof. Owen 

 called the "determination of a special homology;" the recognition 

 of its relation to a primary segment of the typical skeleton of the 

 vertebrata, he called the "determination of its general homology. 

 Before entering upon the higher generalization involved in the con- 

 sideration of the common or fundamental type, Prof. Owen gave many 

 illustrations of the extent to which the determination of special homol- 

 ogies had been carried, dwelling upon those which explained the nature 

 and signification of the separate points of ossification at which some of 

 the single cranial bones in anthropotomy began to be formed ; as in the 

 so-called "occipital," " sphenoid," and " temporal" bones. More than 

 ninety per cent, of the bones in the human skeleton had had their name- 

 sakes or homologues recognized by common consent in the skeletons 

 of all vertebrate animals ; and Prof. Owen believed the differences of 

 opinion on the small residuum, capable with one or two exceptions, of 

 satisfactory adjustment. The question then naturally arose in the phi- 

 losophical mind, upon what cause or condition does the existence of these 

 relations of special homology depend ? Upon this point the anatomical 

 world was divided. The majority of existing authors on comparative 

 anatomy appeared either to have tacitly abandoned, or, with Cuvier and 

 Agassiz had directly opposed, the idea of the law of special homo* 

 lo gies being included in a higher and more general law of uniformity 

 )f type, such as has been "illustrated by the theory of the cranium 

 consisting of a series of false or anchylosed veriebrac. Profs, de 

 Blainville and Grant, however, teach the vertebral theory of the skull; 

 the one adopting the four vertebras of Bojanus and the fctfied pro- 

 pounder of the theory, Oken ; the other regarding the hypothesis of 

 <Jeoffroy St. Hilaire of the cranial vertebra; as more conformable to 

 ■Win* Prof. Carus of Dresden has beautifully illustrated the poet 

 Goethe's idea of the skull being composed of six veriebnv. But these 

 abhors had left the objections of Cuvier and Agassiz unrebutted ; and 

 J^ging from the recent works of Profs. Wagner, Miiller, Sianmus, 

 Kallmann, and others of the modern German school, and those oi 

 Wine Edwards, the doctrine of unity of organization, as illustrated by 

 lhe vertebral theory of the skull, seemed to be on the decline on he 

 eminent. To account for the law of special homologies on the by. 

 P°«hesi of the subserviency of the parts to determined to s.m. lor ends 

 * different animals-to say* that the same bones ■ ir J^^ au * 

 th *y have to perform similar functions-involve many difheu 1*™*™* 

 ** opposed by numerous phenomena. Admitting that the multiplied 



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