CRANIAL NERVES OF CHIMERA MONSTROSA. 673 



Literature. — The cranial spinal nerves were first described by Stannius in Ganoids, 

 where there seem to be two. Van Wijhe confirmed the existence of these nerves in 

 Ganoids, and followed the interpretation of them first adopted by Gegenbaur. The 

 latter (14) thought they represented the ventral roots of the vagus, and considered the 

 true roots of the vagus to be the dorsal roots. He further compared the two sets of 

 roots to the dorsal and ventral roots of the spinal nerves, and, further, his inferior roots 

 to the hypoglossus of Amniota. Jackson and Clarke (16) describe four cranial spinals 

 in Echinorhinus, the last three of which unite with the brachial plexus, which itself 

 communicates by an anastomosis with the vagus. They follow the interpretation of 

 these nerves given by Gegenbaur. Ewart (51) pointed out that the so-called inferior 

 roots of the vagus or cranial spinal nerves were simply the most anterior spinal nerves 

 minus their dorsal roots ; and the fact that in the Skate these nerves pass, not 

 through the skull, but through the vertebral column, practically establishes Ew art's 

 contention (see Ewart and Cole, 66). It is difficult to see what doubt there could 

 ever have been about the matter, seeing that the distribution of a cranial spinal is 

 distinctively that of the ventral root of a spinal nerve. That these nerves correspond 

 to the hypoglossus of higher vertebrates seems to be pretty well established, since the 

 latter apparently consists of the ventral roots of one or more spinal nerves. It is 

 therefore interesting to note that, according to Dohrn and other embryologists, the 

 hypoglossus must not be confounded with the vagus. 



P.S. — I regret that Dr Dixon's memoir on the Vth nerve of man* only came into 

 my hands after the above was written. I have therefore only been able to make very 

 slight use of it, and must refer readers interested in the subject to the original paper 

 itself. The same applies to Miss Platt's work, on Necturus.f Miss Platt describes four 

 sense organs of the infra-orbital line as being innervated by twigs composed of buccal 

 and profundus fibres in equal proportions. She further quotes Dohrn as believing it 

 possible that profundus fibres may accompany the superficial ophthalmic of the facial. 

 This seems to me to be a confirmation of my statement that the profundus fibres of 

 Chimcera to the supra-orbital canal are simply accompanying fibres of the superficial 

 ophthalmic of the facial. I think it must now be admitted, and provided for, that the 

 fibres of one cranial nerve may accompany another and perfectly distinct cranial nerve. 

 Jacobson's anastomosis is an excellent example of this (cp. Strong and Dixon). Miss 

 Platt's statements on p. 520 et seq., concerning the anastomosis between the trigeminus 

 and buccal (which she calls the buccalis profundus) are of a very interesting character, 

 but I may express surprise to find her "hesitating " to confirm Strong's statement that 

 the "trigeminus proper does not participate in the innervation of the lateral line 

 system " (p. 530). I note, further, that Miss Platt points out Strong's error re the 



* " On the Development of the Branches of the Fifth Cranial Nerve in Man," Trans. Royal Dublin Soc, vol. vi. 

 p. 19, 1896. 



t "Ontogenetic Differentiations of the Ectoderm in Nedurus," Q.J.M.S., vol. 38, No. 152, p. 485, 1896. 



