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 to our little 
nger, was enormously elongated. The wings of the little Draco 
volans, 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. 
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. 
e recognition of the same part in different species, Prof. Owen 
called the ‘determination of a special homology; the recognition 
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 
continent. To account for the law of special homologies on the hy 
pothesis of the subserviency of the parts so determined to similar ends 
in different animals—to say that t 
they have to perform similar functions—involve man difficulties, and 
are opposed by numerous phenomena. Admitting that the multiplied 
