SEA-FISHERIES LABORATORY. 277 



sense organs (10 and 11) of the hyomandibular canal, and 

 is then continued at first backwards and then sharply 

 downwards towards the edge of the operculum, to supply 

 the opercular line of pit organs. 



Below and before it bends forwards the Truncus 

 hyomandibularis splits into two large nerves — (1) an upper 

 one turning forwards, the R. mandibulars vii. [man. vii.), 

 consisting of two components accompanying each other, a 

 coarse fibred H. mandibularis externus vii. (man. ext. vii.) 

 and a fine fibred R. mandibularis interims vii. {man. int. 

 vii.), and (2) a R. hyoideus vii. (r. hy.) passing straight 

 downwards. 



9. R. hyoideus (r. hy.). — Consists of two components, 

 a coarse motor and a fine-fibred general cutaneous — just as 

 in Meniclia, but differing from Gadus. As in Menidia 

 the hyoideus below divides into anterior and posterior 

 branches. Sense organ 9 of the hyomandibular canal is 

 supplied from the hyoideus, but this bundle of lateral line 

 fibres has previously been handed over to it from the 

 external mandibular. 



As the R. mandibularis passes forwards it gives- off 

 branches to pit organs, especially one long branch above 

 corresponding to Herrick's nerve m. vii. 8. It may be 

 mentioned that the two components forming the E-. man- 

 dibularis are each easily followed by the microscope. 

 Below a large lateral line branch is given off which sup- 

 plies sense organs 6, 7 and 8 of the hyomandibular canal. 

 In front, the two components separate out, and thereafter 

 pursue independent courses. 



10. R. mandibularis internus (man. int. vii.). — A 

 communis nerve, situated much below the externus. 

 Passes sharply inwards to the visceral surface, and does not 

 rejoin the externus again as in Menidia, and as is usual in 

 TeleosLs, with the exception of Coitus according to Stannius. 



