THE CRANIAL NERVES AND LATERAL SENSE ORGANS OF FISHES. 171 



off remarkably far forward the large nerve which proceeds to the pectoral fin, and which 

 in this case has unmistakably no connection with the first spinal ganglion." Finally, in 

 Chcetostonms we find (p. 539): — "The great recurrent branch of the facial leaves the 

 complex of gauglia belonging to the trigeminus and facial dorsally, and proceeds 

 upwards to the parietal bone, in tchich it lies for part of its course, receiving the stipra- 

 temp)orat tjranch of the first vagus branch, and giving off more posteriorly the branch 

 which passes by the 1st spinal ganglion on its way probably to the pectoral fin." 

 (Italics mine.) 



If the above description by Pollard be compared with the descrij)tion of the accessory 

 lateral nerve of Gadus given below, it will be seen tliat the two systems of nerves 

 correspond with each other, detail for detail, in a most remarkable way. As, however, I 

 can conclusively prove that the accessory lateral is not -a lateral line nerve, it follows, 

 either that the comj^arison docs not liold good, or that Pollard's conclusions as to the 

 nature of the recurrent facial are altogether erroneous. The former alternative is put 

 out of the question by the extraordinary resemblance of the one system to the other. It 

 is hence necessary to enquire into tlie jiossibility of the latter. 



rirst, according to Pollard's o\^-n statement, his work was based entirely upon 

 sections ; and although this is a very valuable method of investigation, I fully a"Tee with 

 Allis that unless the results so obtained are as far as possible checked by dissection, 

 the most disastrous errors are often committed. For example, I should most certainly 

 have described the accessory lateral of Gadus as belonging to the lateral line system 

 had I not previously ascertained by careful dissections that it did not. The way in 

 which the roots of the nerve are applied to the lateral line ganglia {i. e. the external 

 mandibular and latei-alis ganglia) would deceive the most careful investigator not 

 working with Weigert sections and not knowing beforehand the macroscopic anatomy of 

 the nerve. It thus seems to me inevitable that Pollard has mistaken, or rather failed 

 to determine, the precise origin of the fibres of his recurrent facial *. The only factor 

 in the peripheral distribution of the recurrent facial which points to its being a lateral 

 line nerve is the statement that it " supplies the mucous canal at the base of the dorsal 

 fin." What this canal is must remain a mystery until Pollard's work is revised, since ho 

 gives absolutely no description of it, nor any figure. In the meantime I agree with the 

 remark made by Allis (6, p. 627) that " the canal may, however, be of the kind described 

 Dy Emery as the accessory lateral line of Fierasfer, and hence not comparable at ali 

 with the canals of the lateral line system as found in Amia and Teleosts." Allis, 

 unfortunately, is not consistent on the point. He disbelieves in the canal as a lateral line 

 structure in Polypterus, but accepts as such exactly the same canal in Clarias and 

 Auchenaspis, without considering the possibility of the innervation of it in the latter 

 forms having been erroneously described. On the above grounds, therefore, I consider 

 the " recurrent facial " of Siluroids to be a somatic sensory bat not a lateral line nerve, 

 comparable in every respect to the so-called cutaneous branches of the trigeminus or the 

 accessory lateral nerves in Gadus and other Teleosts. 



* I am leaving out of consideratiou the origin of the facial portion of the nerve, since Pollard does not mention 

 from which portion of the complex it arises — whether from the lateral line ganglion or the facial ganglion senun 

 siricto. 



SECOND SERIES. — ZOOLOGY, VOL. VII. 24 



