240 Journal of Comparative Neurology. 



When the first and second branchial trunks of the vagus 

 are found fused for some distance from the ganghon, there ap- 

 pears to be a fusion, also, of the pharyngeal rami of the two 

 nerves. The relations of the r. pre-trematicus, also, of the 

 second trunk become obscured. However, there are cases, in 

 which the trunks are sufficiently separated to show that there is 

 a pharyngeal ramus of the second trunk corresponding to that 

 of the first, and a very small r. pre-trematicus which enters the 

 second branchial arch and, in some instances, fuses with a third 

 ramus of the first trunk at the dorsal end of the second branch- 

 ial cleft. 



As the main nerve turns ventrad to enter the gill arch, its 

 third ramus {X,2br.j) passes into the second external gill and 

 fuses with the sixth ramus of the first trunk. This nerve is dis- 

 tributed as is the corresponding nerve of the first external gill. 

 From the same point of branching of the main nerve, two rami 

 pass caudad into the third external gill; one (not figured) fol- 

 lows the blood vessels, while the other {X,2br.4) passes into the 

 dorsal surface of the external gill. The latter innervates the 

 third m. levator branchii, and sends fibers to the skin over this 

 muscle. This nerve in some specimens, and probably in all at 

 a particular stage of development, anastomoses with the branch- 

 ial ramus of the second spinal nerve. As the external gill de- 

 generates, the general cutaneous component of this nerve, as 

 well as the branch from the second spinal, seems to disappear. 



As the second branchial X trunk turns cephalad into the 

 gill arch, the remainder of its motor component {X,2br.6) goes 

 out in the ramus to the third m. depressor branchii. Beyond 

 this point, the r. post-trematicus, in contrast with the other 

 post-trematic rami described above, contains only communis 

 fibers. Otherwise, it is like those rami in manner of branching 

 and distribution {X,2br.'/=X,ibr.8; X,2br.S=X,ibr.g). 



/}-. The Ramus Supi'ateinporalis Vagi. 



The r. supratemporalis X {spt.') is the smallest nerve aris- 

 ing from the ganglion IX+X It goes out of the dorsal and 

 most anterior region of the ganglion, and inclines cephalad 



