204 STRONG. [Vol. X. 



existence of this peculiarity in the relations between certain 

 minor branches of the Trigeminus and the lateral line nerves 

 to the head. The parallelism is carried further than this, how- 

 ever. The R. ophthalmicus superficialis VII parallels the R. 

 ophthalmicus V, the R. buccalis VII parallels the R. maxillaris 

 V, the R. communicans IX ad VII parallels the R. mandi- 

 bularis externus VII, and the postauditory R. supratemporalis 

 parallels the R. auricularis vagi. In fishes this is still more 

 striking where the two pairs first mentioned are in close 

 apposition and can only be separated with difficulty. We 

 have, besides, in fishes the element from the lobus trigemini, 

 whose fibres are not merely in close apposition but, probably, 

 mingle with the lateral-line fibres, forming thereby a still closer 

 union. On the trunk we have the two long branches : the R. 

 lateralis trigemini (facialis) and the N. lateralis. 



These parallelisms might be partly explained by the sub- 

 jection of the nerves in their growth to similar influences by 

 the other parts, but this could hardly explain such close 

 parallelisms. Nor are such parallelisms easily reconcilable 

 with the theory that the lateral-line system of nerves represents 

 a system phylogenetically different from the others. The ex- 

 planation most naturally suggested is that these three systems 

 jvere originally one. Of the three, the general cutaneous 

 system to which the Trigeminus proper belongs would represent 

 most nearly the primitive nerves from which the others were 

 differentiated. It is, naturally, only the differentiated cutaneous 

 nerves that we find extending over the trunk from the cranial 

 nerves ; or, to put it in another way, the spinal general cutane- 

 ous nerves bear the relation to the cranial special cutaneous 

 branches to the trunk that the general cutaneous branches from 

 the ascending Trigeminus bear to such branches in the head. 

 We might even advance a step further and say that the 

 more intimate fusion of the end bud and lateral line nerves 

 indicates the evolution of the latter from the former, a view 

 probable on other grounds and advocated in Wiedersheim's 

 Grimdriss {6y). 



Hatschek (30) has called attention to the morphological im- 

 portance of the dorsal rami as landmarks of former conditions. 



