540 Reviews. | July, 
but more systematically in some highly philosophical Memoirs read 
before the British Association in Cheltenham, August, 1856,* the 
uuapossibility of reconciling many of the morphological conceptions 
of Owen with what is known of the mode of development of the 
cranium, and of its relations to the vascular and nervous systems. 
The necessity of combining embryological investigation with compa- 
rative anatomy in all our morphological inquiries was at once put on 
a firm and scientific basis by these Memoirs of Mr. Goodsiz’s. 
In pursuing his investigations into the morphology of the skull, 
Mr. Huxley has employed both these methods of research, and has 
arrived at the conclusion “ that the skull is no more a modified vertebral 
column, than the vertebral column is a modified skull: but the two 
are essentially separate and distinct modifications of one and the same 
structure, the primitive groove.” 
To make this proposition clear to our readers, it is necessary we 
should explain that one of the first indications of the development of 
the body of the vertebrate embryo is the appearance of an elongated 
linear groove in the blastodermic membrane, the anterior end of which, 
somewhat dilated, corresponds in position to the future head. At the 
bottom of this groove a cellular cylindrical rod, the notochord, is 
formed, which extends throughout the whole length of the future 
vertebral column. ‘lhe anterior end of the notochord passes into the 
dilated cephalic end of the primitive groove, and corresponds in 
position to a part at least of the future basis cranii. Hmbryologists 
do not agree as to the distance to which this notochord passes forward 
in the base of the embryo skull. Mr. Huxley, grounding his state- 
ments mainly on the observations of Rathke, pronounces very positively 
that in all the vertebrata, Amphioxus only forming an apparent 
exception, it stops short immediately behind that part of the basis 
eranii which lodges the pituitary body. 
Now, highly as everything should be valued which Rathke has 
written on developmental matters, yet it ought not to be forgotten 
that this position of his has not been allowed to pass unchallenged by 
embryologists of equal, and of almost equal repute. Thus Reichert, 
the eminent professor of anatomy in the University of Berlin, states 
that it passes at an early stage of development into the frontal region, 
and Kolliker also has observed it to reach farther forward than Rathke 
allows. In that very remarkable fish, the Amphioxus, in which the 
cranium remains membranous throughout lite, the notochord extends 
almost to the anterior end of the head, far in front of the origins of 
the olfactory and optic nerves, and therefore beyond the region which 
would correspond to the pituitary fossa. The very striking exception 
which this fish affords to the universality of Rathke’s proposition, may 
well make us pause and ask if our investigations into the mode of 
development of the vertebrate cranium were more extended than they 
have as yet been, might not other animals be found in which simi- 
larly well-marked exceptional arrangements exist ? 
From the sides of the “ primitive groove” thin membranous 
* Subsequently published in detailed abstract in the ‘Edinburgh New Philo- 
sophical Journal,’ January, 1857. 
