Royal Institution. 208 



phical researches of Cuvier, and other comparative anatomists, in 

 tracing the same or homologous parts through the animal series, as 

 they were exemplified in the osseous system, and principally in the 

 bones of the head. When any bone in the human skull, for exam- 

 ple, had been thus traced and determined in the skulls of the lower 

 vertebrate animals, the same name was applied to it there as it bore 

 in human anatomy, but understood in an arbitrary sense ; and when 

 the part had no name in human anatomy, but was indicated, as often 

 happened, by a descriptive phrase, it received a name having a close 

 relation to such phrase ; and thus a uniform nomenclature had arisen 

 out of the investigation of the homologies of the bones of the skele- 

 ton, applicable alike to the human subject, the quadruped, the bird, 

 and the fish. The corresponding parts have been sometimes called 

 analogues, and sometimes homologues ; the latter being the appropriate 

 term, since the parts are in fact namesakes. The essential difference 

 between the relations of analogy and homology was illustrated by re- 

 ference to a diagram of the skeletons of the ancient and modern fly- 

 ing dragons. The wings of the extinct pterodactyle were sustained 

 by a modification of the bones 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 finger, was enormously elongated. 

 The wmgs 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 homo- 

 logous with it, inasmuch as it was composed of distinct parts. The 

 true homologue of the wing of the pterodactyle was the fore-leg of 

 the little Draco volans. 



The recognition of the same part in diflPerent species. Prof. Owen 

 called the " determination of its 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 spe- 

 cial homologies had been earned, dwelling upon those which ex- 

 plained the nature and signification of the separate points of ossifi- 

 cation 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 namesakes or homologues recog- 

 nized by common consent in the skeletons of all vertebrate animals j 

 and Prof. Owen believed the differences of opinion on the small re- 

 siduum capable, with one or two exceptions, of satisfactory adjust- 

 ment. The question then naturally arose in the philosophic 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 ana- 



