CBANIAL NERVES OF CHIMSERA MONSTROSA. 649 



ascertained fact, and not a surmise. The superior maxillary divides into two. One of 

 these branches unites with the superficial ophthalmic of the Vth, whilst the ventral 

 division has the course and relations of a maxillary nerve. Further, Ba seems to send 

 some fibres to the Vllth such as I have described in Chimsera. The inferior maxillary 

 is, of course, the mandibular. 



In Amphibia, Strong (68) describes the Vth nerve as follows : — 



(1) Ophthalmic ) 



v ' r f , \ .-,! \ = cutaneous. 



( (2a) maxillary j 



(2) Maxillo-mandibular < 



( (26) mandibular = cutaneous + motor. 



The geography of the maxillary and mandibular is that of prse-and post-branchial nerves. 

 Strong also describes three " accessory cutaneous " branches, two of which spring from 

 the root of 1, whilst the other arises from 2. All of them, however, more or less enter 

 into relations with the lateral line divisions of the Vllth, and therefore exactly corre- 

 spond to the bundles I found in Chimsera leaving the Vth and accompanying the buccal 

 division of the Vllth. It is hence important to note that Strong's " accessory " branches 

 do not supply lateral sense organs, but are cutaneous sensory nerves. The Gasserian 

 ganglion was found to be double, and consisted of an ophthalmic portion and a maxillo- 

 mandibular portion. 



According to Ewart (51), the profundus of Lsemargus arises by several rootlets 

 immediately in front of the main root of the Vth, and these rootlets he regards as 

 equivalent to the small anterior non-ganglionated root of Marshall and Spencer (28). 

 This, as Strong points out, is no doubt the case ; but, as before stated, I have been 

 unable in Cliimsera to connect the profundus with this anterior root. According to all 

 reliable authority, the profundus is a cutaneous sensory nerve ; and Allis (49) states, 

 further, that in Amia it fuses with the superficial ophthalmic of the Vth. The latter 

 statement is interesting, when we remember that in Chimsera, as well as in other 

 cartilaginous fishes, the fusion is with the ophthalmic of the Vllth. Kegarding the 

 twigs from the profundus to the supra-orbital canal, and my explanation thereof given on 

 p. 638, Stannius (pp. 18, 19, and 20) points to several cases of one nerve or a branch 

 of a nerve accompanying another, and considers that it must be looked upon as mere juxta- 

 position, and not that the accompanying nerve is a branch of the nerve which it 

 accompanies. He cites as an example the fourth nerve of several fishes, which is 

 known to accompany the ophthalmicus profundus. Pollard confirms this statement, 

 and adds Clarias to Stannius' list. Pollard elsewhere remarks ; # — " Thus we see that 

 the fundamental grounds for determining the homology of nerves are (1) origin from 

 homologous nerve cells ; (2) terminal distribution to definite structures. The course 

 of the fibres is of less importance." In the same memoir (p. 398), Pollard refers 

 to the motor division of the profundus found in the Cyclostomata. He says : — " The 

 motor fibres supply muscles attached to and working the nasal tube, and belonging 



* Oral Cirri, p. 397. 



