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- 
lowing 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 vertebree ; 
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 vertebre 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 differences 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 trabecul, 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 
