262 NERVE COMPONENTS OF BONY FISHES. 



nerves have thus far remained barren simply because the 

 later development of these so-called sense organs is un- 

 known. Again, the proper comprehension of the neural 

 crest and its significance to metamerism must remain 

 obscure until we learn to which of the components of the 

 adult the cells thus derived are related. The fact that 

 the neural crest is found in the trunk, as well as in the 

 head, and especially Neal's account ('98, p. 238) of its re- 

 lations to the vagus ganglion, suggest that it is related to 

 the general cutaneous component only, while the special 

 cutaneous nerves are derived from the ectodermal thicken- 

 ings. But the demand in this connection is not for specu- 

 lation, but for observations. 



Allis, in his later paper ('97) is dominated by the 

 conception that the sensory nerves are "split off" from 

 the skin. This rests largely upon assumption. It is only 

 in the case of the lateral line nerves that there is any 

 considerable evidence for this, and even here it is by no 

 means clear what may be the relation of the cellular 

 strand formed in connection with the skin and the defini- 

 tive fibrillar nerve. The illustrations given by Neal ('98) 

 indicate that, whether the lateralis nerves are really split 

 off from the skin (and this, I think, needs confirmation), 

 it is quite evident that the general cutaneous nerves are 

 not so derived in Acanthias. I have myself seen Neal's 

 preparations of the r. ophthalmicus superficialis V and VII 

 (the nerves most emphasized by Allis) and believe that 

 such a mode of origin for the ophthalmicus superficialis 

 V is quite out of the question. 



The relations of the components as conceived by Johns- 

 ton ('98) should also be criticised here. As already 

 indicated, this author finds the centres of the acustico- 

 lateral and general cutaneous systems in the oblongata 



