l68 NERVE COMPONENTS OF BONY FISHES. 



mals, for it does not conform to the third criterion men- 

 tioned above. That is, it does not fuse with the r. 

 mandibularis V and hence it does not distribute to the 

 hyoid and mandibular arches in the way characteristic of 

 the mammals. 



Cole, in his discussion of the chorda already referred to 

 ('96a, p. 657 ff.), gives a vigorous and I think conclusive 

 argument for the pre-spiracular nature of the chorda, but 

 his homologies in the several groups of fishes and 

 amphibians are open to criticism in several respects. 



In the first place, he is misled by a false conception of 

 a typical branchial nerve. The pre-trematic ramus he 

 regards as sensory and the post-trematic as "practically 

 motor." The latter point is incorrect; the post-trematic 

 ramus is typically mixed, and the presence of com- 

 munis fibres (r. mandibularis internus VII) in the post- 

 trematic VII is strictly typical, (This is true also even 

 in the Mammalia, if Van Gehuchten's most recent work, 

 cited above, is sound.) He homologizes his chorda with 

 Strong's internal mandibular, but considers that the latter 

 is a pre-trematic nerve which has fused secondarily with 

 the post-trematic. He adds: " My reasons for this asser- 

 tion are two — (i) his man. int. arises from the base of the 

 palatine, which is almost invariably the origin of the pre- 

 spiracular nerve ; (2) it consists entirely (?) of splanchnic 

 sensory fibres (and thus agrees with the palatine), whereas 

 the post-spiracular division of the Vllth is practically 

 motor." 



Now, the first of these reasons loses its force entirely 

 when we remember that nearly all of the communis fibres 

 of the VII nerve diverge into their respective rami im- 

 mediately upon leaving the ventral edge of the geniculate 

 ganglion, so that both the pre-trematic and the post- 



