8 yoiirnal of Comparative Neurology and Psychology. 



Although the work on nerve components has shown several 

 of the names commonly used to designate these rami to be inap- 

 propriate in a number of types, in order to get some basis on which 

 a comparison of the number of rami carrying communis fibers 

 could be made, the current nomenclature has been used. The 

 table is open to criticism, of course, in this regard, but it does 

 bring out the fact that of the rami usually attributed to the V 

 and VII nerves a great variation exists in the number carrying 

 communis fibers. In the case of Petromyzon, one branch of the 

 hyomandibular trunk carries communis fibers and Johnston does 

 not state, so far as I am aware, its homology with corresponding 

 rami of the teleosts. In the case of Rana, I have catalogued only 

 two rami as bearing communis fibers, namely, the ramus pala- 

 tinus and the ramus mand. int. VII, but the ramus palatinus near 

 its peripheral distribution forms anastomoses with the ramus 

 oph. V and with the ramus mand. int. VII, so that there are 

 really four rami in the frog carrying communis fibers, although 

 they do not enter these rami near their ganglia. The teleosts, 

 owing to their close relationship and the constancy of these rami, 

 furnish the best basis for comparison. 



Of the fourteen rami usually found in teleosts, two, the ramus 

 mand. int. VII, and ramus oper. sup. VII, are absent in Ameiurus, 

 and of the twelve remaining, ten contain communis fibers and 

 these fibers are absent from the ramus oph. sup. VII and ramus 

 buccalis VII only. An examination of Menidia shows only five 

 rami carrying communis nerves; the same is true of Gadus, but 

 while these two types have the same number of rami carrying 

 communis fibers the rami are not identical. Menidia has com- 

 munis fibers in the ramus mand. int. VII, which is absent in Gadus 

 while Gadus has communis fibers in the ramus mand. int. V 

 which is present in Menidia but contains no communis fibers. 

 The distribution of the taste buds on the ectoderm is correlated 

 more or less closely with this variation in the rami carrying com- 

 munis fibers, although peripheral anastomoses sometimes ma- 

 terially modify the distribution of taste buds from what we should 

 expect to find, judging fromthe number of rami carrying communis 

 fibers at a point near the ganglia. 



The same variation is found in Amphibia. Amblystoma and 

 Triton each have three rami which carry communis fibers that 

 run out with these rami from near the ganglia, while the frog 

 has only two. 



