2 74 Likenesses ; or. Philosophical Anatomy 



of tlie future skull has become cartilaginous, an indication of 

 transverse segmentation is to be traced in the soft tissue of 

 that region — a proof of what oversights may be committed 

 by relying too hastily on development as our guide. The 

 continuous chondritication of the base of the skull before 

 observed, had led to a denial of all fundamental transverse 

 segmentation of that region by the opponents of the vertebral 

 theory of the skull, while the assertors of that theory 

 regarded such continuity as an induced and adaptive 

 masking of a segmentation visible to the eye of the intellect, 

 though not to that of the sense. The latter view now turns 

 out to have been the right one, and a latent tendency, specu- 

 latively divined, has noAv been to a certain extent made 

 palpably evident. Hoav many other latent tendencies may 

 not exist which never render themselves visible to sense ? 

 Might it not be contended that the ultimate segmentation of 

 the bony cranium of mammals is one mode of expression, 

 disguised and highly modified, of such latent earliest tend- 

 ency to serial segmentation ? 



But most striking of all recent phenomena concerning 

 the vertebral archetype, is the explicit return just made by 

 Professor Huxley ^ to the conception so long ago advocated 



^ See Proceedings of the Royal Society, No. 157, p. 127. The author's 

 determination of the homologies he seeks to establish rests entirely upon the 

 constancy of position of the velum palati, which he has selected as his fixed 

 point. A certain hesitation in assenting to the new view may be justified by 

 the absence (as far as yet known) of the auditory organ in the amphioxus. 

 If there is one thing which is constant in the vertebrata it is the auditory 

 capsule, and the figures on the paper referred to, show it relatively largest 

 in the youngest condition of the ammocsetes chosen for comparison. The 

 distribution of the cranial nerves can hardly be said to afibrd decisive char- 

 acters, since as there are myotomes, if nerves are supplied to them laterally 

 from a central nervous trunk, each nerve must divide into a dorsal and a 

 ventral branch to supply each muscular segment. Similarly, nervous supply 

 must be sent to the front end of the body, and if the so-called eye-spot 

 of amphioxus be an eye-spot, the circumstance that this nerve passes over it, 

 though a striking fact, is scarcely sufficient to identify it with the ophthalmic 

 division of the fifth nerve of fishes and higher vertebrates. 



