1895.] SENSORY CANAL SYSTEM OF FISHES. 297 



Trigeminal. 



lr:tSl-~"^"-^"''n^-^y -stant, ...^yi., .nain canal and 

 Eamus oticus J *^^^ ^"P""^" ^"*^ sub-orbital branches. 



Id Amiurus the ramus oticus supplies the upper part of the opercular 

 portion of the operculo-mandibular branch. 



In Amiurus the ramus ophthalmicus superficiahs supplies the cluster- 

 pores. In Conger the ramus maxillaris may supply posterior part of 

 the sub-orbital Ijranch. 

 Bamus mandibularis. May either supply mandibular portion of the operculo- 

 mandibular branch {Amiurus) or no portion of the canal system (other 

 types). 

 Facial. Supplies the operculo-mandibular branch. In Conger also supplies 



a sensory organ in lateral canal. 

 Glossopharyngeal. May either innervate a portion or the -whole of the main 

 canal or the occij)ital commissure only, or it may not supply any portion 

 of the canal system (Amiurus?). 

 Vagus. May or may not by anterior branches supply the initial portion of 

 the main canal of the head. 



It will be seen, from the above tabular view of the nerves, that 

 the innervation proceeds very largely from the trigeminal group of 

 nerves. I have pointed out in previous papers (3 and 4) that in 

 the Elasmobranchii the canal system was supplied solely by 

 the facial group ; in the Ganoidei the same feature still obtained, 

 with the addition of a larger innervation from the ramus oticus, 

 and also a portion of the system in Pohjodon was supplied by the 

 ramus mandibularis of the trigeminal. 



In most of the species examined the glossopharyngeal nerve 

 innervated some portion of the main canal or the occipital com- 

 missure (excepting Amiui~us ?), replacing the branch of the vagus 

 lateralis marked 1' in Polyodon (cf. 3. pi. 40. fig. 11). 



With the exception of Amia, in which Allis (1) states that the 

 glossopharyngeal nerve innervates a single sense-organ and a series 

 of what he terms "^pit-organs " — probably synonymous with what 

 I have called "primitive pores" — the Physostomi are the most 

 generalized class of fishes in which such a condition is found. 



The innervation of any portion of the canal system by the 

 glossopharyngeal nerve is certainly a characteristic feature in 

 Teleostean fishes. Amia is probably the only Ganoid in which 

 such a condition obtains. 



Vni. BiBLIOGEAPHY. 



Allis, E. P.—" The Anatomy and Development of the 



Lateral Line System in Amia calva." Journ. Morphology, 



1889, vol. ii. pp. 463-569, pis. xxx.-xlii. 



Bridge, T. W., and Habdon, A. C— " Contributions to the 



Anatomy of Fishes. — II. The Air-BJadder and Weberian 



Ossicles in the tSUuroid Fishes." Phil. Trans. 1893, pp. 65- 



333, pis. 11-19. 



CoLLiNGE, Walter E.— " The Sensory Canal System of 



Fishes. Pt. I. Ganoidei," Quart. Journ. Micros. Sci. 1894, 



yol. xxxvi. pp. 499-537, pis. 39, 40, 



