— 89 ^ 



The next brancti of the truncus facialis, in the 55 mm Scorpaena, is given off as the truncus 

 traverses its foramen, and contains communis fibers only. Turning downward and backward it issues 

 through the facialis opcning of the trigemino-facialis chamber and then almost immediately joins 

 and anastomoses completely with the ramus anterior of the nervus glossopharyngeus. The nerve 

 so formed is Jacobson's nerve. It runs antero-ventrally along the dorso-anterior aspect of that part 

 of the hyoid cleft that lodges the opercular hemibranch, and is distributed to that hemibranch and 

 to the adjacent tissues on the anterior surface of the cleft, delicate branches of the nerve accompanying 

 both the efferent and afferent arteries of the hemibranch. In both Cottus and Lepidotrigla this nerve 

 is found in almost identical conditions, and it doubtless also is in Dactylopterus, but in this latter 

 fish it was not traced beyond the point of its anastomosis with the glossopharyngeus. The fibers 

 of the glossopharyngeus all rim distally with the facialis fibers, none of them turning proximally 

 along the facialis nerve, as I was led to suppose might be the case in Scomber. 



Immediately before or after the facialis branch to Jacobson's nerve arises from the truncus 

 facialis, that truncus receives, in both Scorpaena and Lepidotrigla, a communicating branch or 

 branches from the facialis sympathetic ganglion, this connection doubtless existing also in the other 

 fishes of the group but not there being traced. 



After giving off the nerve to Jacobson's anastomosis, the facialis, in Scorpaena and Lepido- 

 trigla, sends a motor branch to the adductor arcus palatini, and then a branch to the adductor hyo- 

 mandibularis ; this latter branch also innervating the adductor and levator operculi. These two nerves 

 together form the ramus opercularis profundus of Herrick's nomenclature. The branch that goes 

 to the adductor hyomandibularis is joined posteriorly by and anastomoses with a branch of the supra- 

 temporal branch of the nervus vagus, certain of the fibers of the vagus running proximaUy along 

 the fibers of the opercidaris profundus and the two nerves thus appearing as a complete and uninter- 

 rupted circuit. In Cottus and Dactylopterus the opercularis profundus is also found, but its ana- 

 stomosis with a branch of the vagus was not traced. 



The truncus facialis, in Scorpaena and Lepidotrigla, is then joined by the communicating 

 branch from the trigeminus ganglion and becomes the truncus hyoideo-mandibidaris of Stannius' 

 nomenclature. This nerve continues laterally and slightly downward and enters the facialis canal in 

 the hyomandibular, lying, in its course, postero-dorsal to the adductor arcus palatini and anterior to the 

 adductor hyomandibularis and to all of the levator muscles of the branchial arches. As it enters its canal 

 in the hyomandibular, a branch is sent backward in the sniall branch canal in the hyomandibular, and, 

 separating into two parts, innervates the two dorsal latero-sensory organs in the preopercular canal. 

 This small branch is the ramus opercularis superficialis of Herrick's nomenclature, and it was traced 

 in the dissections and not in the sections of Scorpaena ; the sections here being quite imperf ect. In 

 the dissections no branch could be found distributed to the outer surface of the operculum, such as 

 Herrick describes in Menidia, but in Lepidotrigla this branch was found, though the character of its 

 fibers could not be determined. In Menidia these fibers of the nerve are said by Herrick to be partly 

 general cutaneous and partly lateralis. These latter fibers are said to supply certain naked cutaneous 

 sense organs lying on the outer surface of the operculum, these organs being of that intermediate 

 type between pit-organs and terminal buds which are always puzzling to every observer. Herrick 

 concludes that these organs must, because of their innervation, belong to the lateral line rather than 

 the communis system, a conclusion I am not prepared, from the facts so far presented, to accept. 

 In the Cod the corresponding fibers of this nerve are said by Herrick ('00) to probably be wholly 



Zoologica. Heft 57. 12 



