590 'Journal of Comparative Neurology and Psychology. 



After the above fibers are given off the nerve passes down 

 behind the branchial cartilage and supplies the muscular sheath 

 and the lining of the anterior half of the second gill sac. In 

 studying the cranial nerves of P. dorsatus I did not appreciate the 

 importance of the caudal branch of this nerve "which disappears 

 in the muscles" (1905, p. 171). I have reviewed those sections 

 and find this to be a large branch which enters the muscular 

 sheath of the second gill sac in w^hich it dwindles away. The 

 two species agree, then, in that the IX nerve innervates the muscular 

 wall of the halves of the first and second gill sacs adjacent to the 

 first branchial arch in which the nerve runs. Whether this same 

 branch sends fibers into the lining of the second gill sac in P. 

 dorsatus I can not determine. If such fibers are present and are 

 disposed in small bundles or singly as inLampetra, they could not 

 be traced in transverse sections. It is altogether probable that 

 the arrangement is the same in both species, especially as no other 

 provision is seen for the innervation of the anterior half of the 

 second gill sac. 



In P. dorsatus the terminal portion of the IX nerve which goes 

 to the skin is larger than the posterior branch just referred to. 

 In Lamptera a few fibers to the skin, probably general cutaneous, 

 are impregnated in these preparations but the lateral line fibers 

 which presumably run throughout this portion of the nerve (see 

 1902, p. 47 and 1905, p. 172) are not impregnated. 



The VII nerve has its communis or visceral sensory ganglion 

 within the auditory capsule. The trunk, including visceral, cuta- 

 neous and motor components, emerges from the capsule and 

 descends on the caudal surface of the lateral line ganglion, bends 

 caudad beneath the capsule and divides into two chief rami. 

 One of these running straight caudad will be described below as 

 the sympathetic trunk. The other is the main trunk of the VII 

 nerve. It descends in front of the first gill sac and at about the 

 level of the dorsal border of the velum (fig. 7) divides into anterior 

 and posterior branches. The anterior branch has been described 

 above as the cutaneous branch. The posterior branch bends 

 inward and backward and gains the inner border of the muscle 

 sheath of the first gill sac (figs. 7 and 8). At the same time it gives 

 off branches which, together w^th others given off lower down, 

 supply the lining of the whole anterior half of the gill sac, inter- 

 lacing with the terminal fibers of the IX nerve about both the 



