596 



cimens. In one the nerve arose just within the orbit from the maii> 

 trunk of the trigeminus and passed upwards. It then crossed the 

 ophthalmic VII, without being connected with it in any way, and was 

 distributed to the skin. This represents the discrete condition and is 

 rare amongst fishes. In one of the other specimens however the nerve, 

 after arising in the same way, and pursuing a similar course proximally, 

 on approaching the ophthalmic VII bent forwards and completely fused 

 with it not far from the posterior boundary of the orbit. This re- 

 presents the more normal or fused condition and has been figured in 

 Chimaera both by Stannius^) and Collinge^). 



The Root of the Trigeminus. — One of the features of 

 main interest in the cranial nerves of Chimaera is the absence of any 

 confusion between the fifth and seventh nerves. There is no trigemino- 

 facial complex, and, as far as we are aware, this is the only fish in 

 which the separation of these two nerves is so complete and obvious. 

 Careful dissections of the present specimens entirely confirm the pre- 

 vious account (op. cit., p. 644). The root of the fifth lies underneath 

 and is entirely hidden by the root of the buccalis facialis, but there 

 is no connection whatever between the two nerves, and the trigeminus 

 has its own origin from the ventro-lateral wall of the medulla by two 

 short rootlets — a small anterior and a much larger posterior. The 

 smaller root will probably represent the motor and the larger the 

 cutaneous root of the trigeminus. 



The Roots of the Facial and Auditory Nerves. — We 

 have investigated these roots with great care, and have several ad- 

 ditions to make to the previous account, and one mistake to correct. 

 We have therefore found it necessary to re -draw the figure of the 

 roots of these nerves. Our remarks are based partly on dissections, 

 partly on a set of the roots dissected out, faintly stained with borax- 

 carmine and mounted as a transparent microscopic object, and partly 

 on another set cut into serial sections. The material was not preserved 

 for microscopic work, so that the sections were not available for satis- 

 factorily working out the nerve components. We therefore submit the 

 results of our examination of the sections with some reserve, except 

 as regards the lateral line component of the hyomandibular trunk (the 

 only point of real importance), about which the material favours a 

 definite decision. 



The mistake referred to above relates to the position of the audi- 

 tory root. In the previous account this was figured as dorsal to the 



1) Das peripherische Nervensystem der Fische, 1849. 

 2^ Proc. Zool. Sog. London, 1895. 



