of the Skull and the Skeleton. 359 



Thus, excluding the sense-bones and dermal bones, I would 

 interpret the neural part of the skull as having been originally 

 developed from a single vertebral centrum and neural arch, fol- 

 loYving in its development, only in a more perfect way, exactly 

 the same laws as govern the formation of ordinary vertebral 

 arches. That it is a vertebra is not affirmed, because it presents 

 modifications of structure which are nowhere seen in vertebrae ; 

 but these, which are the development of epiphyses by a neural 

 arch, are of a kind quite consistent with the vertebrate plan, and 

 certainly to have been expected under the influence of pressure. 

 Indeed it is not too much to say that, under the influence of 

 the requisite pressure, any other neural arch could have simi- 

 larly been developed into a cranial cavity; and therefore a 

 definition by Professor Huxley, "that the skull no more consists 

 of a chain of vertebrse than the vertebral column consists of a 

 chain of skulls," more faithfully expresses the kind of relation 

 between the neural regions of the two structures than any 

 statement that I have yet met with. And if the neural part of 

 the skull is considered to be a vertebra at all, it can only be an 

 ideal typical vertebra, where every possible part is present, and 

 to which, therefore, the ordinary uniformity of imperfect develop- 

 ment of most vertebral arches offers no near parallel. On the 

 whole, the difi^rences and affinities are perhaps so well marked 

 as nearly equally to justify those who would call it part of a 

 skull and those who prefer naming it a transformed and 

 thoughtful vertebra, both of which statements would be equally 

 true. 



If the cranium of a full-grown Gallus domesticus be boiled, 

 from the great intensity of ossification in the animal, it readily 

 separates into two portions — an anterior part, which is made up 

 of the bones of the face and jaws, and a posterior part, namely 

 the brain-case. And here it is seen that the interorbital septum, 

 which is formed from the trabeculse, is embraced by the pre- 

 sphenoids and frontals reaching the orbitosphenoids so as to close 

 up the brain as in Mammals ; so that the ethmoid presents the 

 relations of a cranial bone, and might be regarded as an ossifi- 

 cation produced by the olfactory ganglia — a sort of special 

 epiphysis. The bones which have been considered, it will be 

 remembered, only correspond to the neural arch of a vertebra. 

 Of the inferior arch, or that which corresponds to the ribs, it is 

 at first hard to see any indication. There are under the basi- 

 sphenoid of most animals two ossifications which Mr. Parker 

 has named basitemporals, which are clearly epiphyses of the 

 basisphenoid. In the subclass of birds called Pterodactyles, 

 these bones are anchylosed to the anterior margin of the basi- 

 occipital, and in Plesiosaurus they appear to form the inferior 



