42 NERVE COMPONENTS OF BONY FISHES. 



instead of five as in the adult, and the mandibular canal has 

 not been closed so as to cover the first organ of that line. 



Is the simplicity of the lateral line system in Menidia as 

 compared with many other fishes, especially the lower 

 fishes, to be regarded as primitive simplicity or as the 

 result of degeneration? Cole would say the former, for 

 he argues ('98, p. 245) that the naked condition of the 

 sense organs is always the primitive and that in the de- 

 cline of the system these organs are lost before the canals. 

 But how about the Amphibia in which the system is fluc- 

 tuating on the verge of extinction and yet no canals are 

 present, only naked organs? On the whole I incline to 

 regard the condition in Menidia as reduced rather than 

 primitive. 



The various recent attempts to show that a part of the 

 lateral line system is innervated by branches of the tri- 

 geminus, such as that of Collinge ('95), doubtless rest 

 either upon faulty observation or loose definition. Per- 

 haps the clearest of these cases is that of Chimaera (Cole, 

 '96a) in which two organs of the supra-orbital line are 

 innervated from the profundus; but Cole himself feels 

 confident that a microscopical examination would show 

 that the nerve in question is really a twig of the lateralis 

 system which is detached from the r. ophthalmicus super- 

 ficialis and secondarily joined to the profundus — a ques- 

 tion easily answered by a determination of the central 

 connection of these fibres, whether in the lateralis or the 

 Gasserian ganglion. 



Another case difficult of interpretation is given by Miss 

 Piatt ('96, p. 530), for Necturus. "I have traced the 

 nerve twigs to each one of the terminal clusters of organs 

 on the infra-orbital line, and find that four of the organs, 

 which I have marked in the reconstruction, are supplied 



