Botany and Zoology. 129 



The tympano-mandibular and the hyoidean arches had both been 

 recognized as resembling ribs. A like homology of the scapula had 

 early been detected by Oken ; but its relation to the skull or occiput 

 had been masked, and had escaped previous notice, by its displace- 

 ment from its natural or typical connexions in all the air-breathing 

 vertebrata. 



The enunciation of these correspondences has sometimes been re- 

 ceived by anatomists conversant with one particular modification of the 

 general type, with as little favor as those of the " cannon-bone" to the 

 metacarpus, of the " great and small pastern" and the " coffin-bones" 

 to the digital phalanges of the human hand, may be supposed to have 

 been by the earlier veterinarians. 



Prof. Owen adduced instances of the displacement of different ver- 

 tebral elements to subserve special exigencies, as that of the neura- 

 pophyses in the bird's sacrum, and that of the ribs of the human tho- 

 rax, in which there could be, and had been, no question as to the re- 

 ference of such displaced parts severally to their proper vertebral seg- 

 ments. The displacement of the scapular arch from the occiput was a 

 modification of precisely the same kind, and differed only in degree. 

 In the crocodile every cervical as well as every dorsal vertebra had its 



ribs; and in the immature animal the same elements existed, as distinct 



parts, in the lumbar, sacral, and in several caudal vertebra. The 

 occipital vertebra would be represented only by its " centrum" and 

 "neural arch," unless the loose and obviously displaced seapulo-cora- 

 eoid arch were recognized as its pleurapophysial and hsemapophysial 

 elements. This arch made its first appearance in every vertebrate 

 embryo close to the occiput ; and in fishes — the representatives of the 

 embryo-state of higher vertebrata, where the principle of vegetative 

 repetition most prevailed, and the primitive type was least obscured by 

 teleological or adaptive modifications — the scapular arch retained its 

 true and typical connexions with the occiput. 



The general homology of the locomotive members as developments 

 °f the diverging appendages of the inferior vertebral arches, was illus- 

 trated, and the parallelism in the course of the modifications of all such 

 appendages pointed out. As the scapular arch belongs to the skull, so 

 ll * appendages, the pectoral or anterior members, were essentially parts 

 of the same division of the skeleton segments. 



. Asa corollary to the generalization that the vertebrate skeleton con- 

 Sls ted of a series of essentially similar segments, was the power of 

 tracing the corresponding parts from segment to segment in the same 

 skeleton. The study of such -serial homologies" had been com- 

 menced by the unfortunate Vicq. d'Azyr, in his memoir " on the paral- 

 lelism of the fore and hind extremities;" and similar relations could 

 b * traced through the more important elements of the series oi vertebra. 

 Pr *f. Owen believed it to be an appreciation of some of these hornol- 

 JP? that lay at the bottom of the epithets, -scapula of the head, 



1,M »n of the head," -femur of the head," &c, applied to certain 

 **■! bones by Oken and Spix. To Cuvier this language had seemed 



"nmtelligi b | e jargon ; yet the error consisted merely in *"£"** 

 y*»l instead of a general name to express the serial homology rightly 

 d,s <*rned, in some of the instances, by the acute German anatomist*. 



--»v,u, m some oi tne insuuicus, uy aw •*-" 



SfccoKD Series, Vol. IV, No. 10.— July, 1847. I 7 



