172 NERVE COMPONENTS OF BONY FISHES. 



necessary some qualification of Cole's remark ('98a, p. 200): "There 

 are several cases on record where on the disappearance of the spiracle 

 the pre-spiracular accompanies for a time the post-spiracular nerve 

 and thus becomes a topographical, but not a morphological, post- 

 spiracular nerve. It seems to me that when the early development 

 of the nerves of Amia has been investigated it will be found that the 

 'internal mandibular' nerve is morphologically pre-spiracular, though 

 occupying a post-spiracular position in the adult. This is what we 

 know has happened in Ratia (cp. Strong's 'internal mandibular'), 

 and what has doubtless also happened in Ckimcera and Gadus." 

 This, it seems to me, simply begs the question. There are no facts, 

 so far as my knowledge goes, which would pennit us to say that we 

 "know" of any such secondary changes in the relations of this nerve, 

 though such changes are theoretically possible. 



In the case of Amia, AUis has replied {Anat. Anzeiger, XV, p. 

 374), stating specifically that the r. mandibularis internus VII is 

 post-spiracular in the larval Amia. In the case of Chimera, we con- 

 cluded above that the post-trematic communis element has fused 

 with the pre-trematic, rather than the post-trematic ramus. And in 

 Gadus the fusion of the pre-trematic communis element with the 

 post-trematic is manifestly impossible, for the simple reason that the 

 post-trematic trunk totally lacks communis fibres. 



The r. pre-trematicus VII of my description is unquestionably the 

 same nerve as the posterior palatine nerve of Gadus (Cole, '98a, p. 

 135). It is not so certain that it is the same as AUis' posterior pala- 

 tine of Amia ('97, p. 619) . It has the same origin and it runs out in 

 front of the pseudobranch, but its distribution seems to be far 

 cephalad and laterally along the border of the maxilla. If it supplies 

 the pseudobranch, then this part would be homologous with the 

 nerve in question. The remainder of the nerve cannot be compared 

 with anything in Menidia. 



In Protopterus the r. mandibularis internus VII is evidently from 

 the description of Pinkus ('94) in part, at least, the post-trematic com- 

 munis element, as in other Ichthyopsida, and not a pure motor nerve, 

 as Cole supposes ('98a, p. 201). Pinkus regards his r. palatinus in- 

 ferior as the chorda tympani and homologizes it (as Miss Piatt does 

 the "external palatine" of Necturus, '96, p. 534) with Strong's r. 

 mandibularis internus VII. The latter of these conclusions is doubt- 

 less incorrect, for Strong's nerve is, as we have just seen, also 

 present. AUis may be right in identifying Pinkus' nerve with cer- 

 tain communis branches of the r. mandibularis V of Amia. But 

 these relations must remain hypothetical until we have more exact 

 knowledge of the components in Protopterus. 



