202 MR. F. J. COLE ON THE STRUCTURE AND MORPHOLOGY OF 



motor. I may mention here that there is a nerve in Gad us exactly corresponding to the 

 " internal mandibular " of Allis in Amia. I have for the above reasons described it as 

 the pre-spiracular or chorda tympani division of the facial. The following scheme of the 

 constitution of the facial nerve in a typical fish takes no account of the lateral line 

 constituent, which only accompanies the facial and is not a branch of it : — 



Eacial nerve sensu stricto (minus external mandibular lateral line nerve). Forks over 

 spiracular cleft into — 



(1) Palathnis or viscer alls facialis. Is joined by Jacobson's anastomosis (^palatinus 



or visceralis glossopharyngei), and is a visceral sensory nerve distributed to 

 the mucous membrane of the roof of the mouth in front of the spiracle. 



(2) A visceral sensory nerve arising from the base of (1) and forming part of the 



same bundle of fibres. FrcB-spiracular, frce-hranchial, prcB-trcniatic, cr 

 chorda tjjnipani division of facial. May be continued ventrally on to pharynx, 

 in which case it should become related to the posterior face of the mandibular 

 arch, and be distributed to the mucous membrane of this arch. 



(3) A visceral motor nerve = main trunk of facial. Forms external to spiracle a 



portion of the nerve known as the truncus hyomandibularis facialis, of which 

 the remainder and larger part here=the external mandibular lateral line 

 nerve. JPost-spiracular, post-brancliial, post-tremafic, internal mandibular^ or 

 hyoidean branch of the facial. Continued ventrally on to pharynx, where it 

 becomes related to the anterior face of the hyoid arch, the muscles of which 

 absorb most of its fibres (Allis, 6, p. 745). Gives off posteriorly the nerve 

 known as the Ramus operctUaris facialis to the muscles of the hyoid arch 

 (Allis, loc. cit.). 



Allis (4, p. 472), in seeking to prove the independence of the supra-orbital canal (which 

 is of course independent as far as innervation proves anything), goes somewhat too far 

 in advancing the developmental independence of the supra-orbital canal from the infra- 

 orbital as proving this point. As the lateral canals, according to his own description, 

 develop in indejiendent segments, each containing a sense organ, his argument proves 

 nothing, especially as there is a dermal tubule at the point of anastomosis between the 

 two canals which involves their independence as a developmental necessity. It will 

 have been noticed that I have not described an ophthalmicus profundus nerve in Gadus. 

 The question of the existence of this nerve in Teleosts is fully discussed by Allis (1897, 

 6, pp. 538 et seq.), and lie concludes : " In no Teleost, w^ith the single recorded exception, 

 so far as I can find, of Trigla, is there a sej)arate profundus ganglion and root. Both 

 ganglion and root are apparently always completely fused with the ganglion and root of 

 the trigeminus." He further points out that the nerve identified by Pollard as the 

 profundus in certain Siluroids is really the ophthalmicus superficialis VII, and, I think,, 

 rightly doubts any fusion between the profundus and superficialis as explaining the 

 apparent absence of the former, believing it to be " more probable that the ophthalmicus 

 profundus of Elasmobranchs is entirely wanting in Teleosts." Goronowitsch's and other 

 authors' nerves, therefore, named the ophthalmicus profundus, represent the ophthalmicus 

 superficialis V, and his ophthalmicus superficialis is the lateral line nerve of that name 



