Johnston, Nerves of Petromyzonts. 607 



vertebrate. It is rather a peculiarly large dorsal ramus, with 

 motor components only in cyclostomes. It never acquires the 

 visceral sensory components distributed to the lining of the ali- 

 mentary canal which characterize rami of the branchial nerves, 

 while the true pretrematic rami never acquire the cutaneous com- 

 ponents which characterize the maxillaris. Moreover, no pre- 

 trematic rami are developed in the other nerves in petromyzonts. 

 The trigeminus in the lamprey is a branchial nerve like the glosso- 

 pharyngeus, but supplying the specialized muscles of its arch, 

 wanting in the branches to the next posterior gill sac which has 

 disappeared, and possessed of an extremely large dorsal ramus 

 which supplies muscles as well as skin of the buccal region. It is 

 of course held that the ophthalmicus is a separate nerve. 



6. The sensory innervation of the velum comes entirely from 

 the maxillaris. This would imply that the velum is covered by 

 ectoderm, which may be true, or that the velar nerve is a com- 

 munis component in the maxillaris. The facts that the fibers of 

 the velar nerve are fine and its ganglion cells small and that its 

 ganglion forms the cephalic portion of the gasserian ganglion 

 not mingled with the cells of undoubted cutaneous fibers, lend 

 color to the supposition that this nerve may be communis. The 

 central connections of the fibers were not impregnated. 



7. The facial nerve innervates one special muscle related to 

 the tongue, the hyo-hyoideus anterior of FiJRB ringer. I would 

 suggest that one function of this muscle is to raise the tongue 

 against the floor of the water tube (velar orifice) and so with the 

 m. velo-hyomandibularis internus, which enwraps the oesophagus 

 dorsally, to close both the water tube and the oesophagus during 

 the sucking movements of the buccal funnel. 



8. The presence of fibers ending in the intermuscular septa 

 which may serve the muscle sense. 



PAPERS CITED. 



FURBRINGER, P. 



1875. Untersuchungen zur vergleichenden Anatomic der Muskulatur des Kopfskelets der 

 Cyclostomen. Jenaische Zeitschr., Bd. 9. 



FUSARI. 



1901. Presentation de preparations microscopiques demontrant les terminaisons nerveuses dans 

 les muscles striees, dans I'epiderme et dans I'epithelium de la cavite buccale de 

 I'Ammocoetes branchialis. C. R. Assoc. Anat. Jme. sess., Lyon. 



1905. Contributo alio studio delle terminazioni nervose nei muscoli striati di Ammocoetes 

 branchialis. Atti Acad. Sc. Torino, vol. 40. 

 Herrick, C. Judson. 



1900. A contribution upon the cranial nerves of the codfish. Journ. Comb. Neur., vol. 10. 



