Herrick, Cranial Naves of Bony Fishes. 169 



veloped in response to an obvious functional need. The advan- 

 tage to be derived from such a centraHzation of the sensory ap- 

 paratus of the entire digestive tract is obvious. 



The acustico-lateral system is apparently phylogenetically 

 the youngest of the cranial systems. Its relations to the other 

 sensory systems are still problematical. 



Addendum. Since this paper was read there has appeared 

 the very suggestive paper on the cranial nerves of the sturgeon 

 (Anat. Anzeiger, XIV, 22-23) by J. B. Johnston. His conclu- 

 sions, which differ somewhat from my own, I shall examine 

 critically at another time, merely mentioning a few of the sali- 

 ent points here. Johnston identifies the general cutaneous and 

 acustico-lateral systems, regarding them both as representing 

 the dorsal horns of the spinal cord. The acustico-lateral is the 

 more highly specialized part and it possesses a spinal portion 

 running parallel with the spinal V, which he calls the spinal 

 VIII. The close internal connections between these two sys- 

 tems and their close parallelism in many other respects certain- 

 ly favor the belief that the acustico-lateral has been differen- 

 tiated from the general cutaneous, in spite of the complete dis- 

 creteness of the two systems peripherally. And it should be 

 noted that this does not imply that the lateralis rami from the 

 head can ever be directly homologized with any rami of spinal 

 nerves ; for the former are none the less neomorphs in the head, 

 even though their precursors were in the spinal nerves, as Cole 

 has so ably argued. It is interesting to note that the latter au- 

 thor also regards the acustico-lateralis system as the derivative 

 of the general cutaneous, the evidence in this case being embry- 

 ological. 



Now, Johnston regards the communis system as peculiar 

 to the head, having no spinal representatives. He even goes 

 so far as to state that ' ' no sensory fibers of the spinal nerves 

 supply visceral structures." This, I think, is erroneous, even 

 in the higher forms, though the great reduction and profound 

 modification of the viscero-sensory system of the trunk under 

 the influence of the r. visceralis vagi are freely granted. Further- 



