NoRRlS, Nerves of Atnphiuma. 543 



addition it is reinforced by fibers from the jugularis branch that 

 supplies the sphincter coUi muscle. If the nerve contains any 

 general cutaneous fibers they must come from the latter source. 

 The exact mode of origin of this nerve is subject to a great deal 

 of individual variation, and as it leaves the posterior border of 

 the depressor mandibulae muscle it may consist of two or more 

 parallel twigs that run for some distance before uniting (as in 

 fig. i). In passing the thymus gland the nerve is always in two 

 or more divisions. Sometimes a small branch runs back into the 

 trunk along with the main nerve (fig. l). In some individuals a 

 small branch is seen to leave the main nerve in the neighborhood 

 of the thymus gland, and to pass antero-dorsally anastomosing 

 with the r. supratemporalis X. In one instance the anastomosis 

 was also with one of the twigs of the r. lateralis mediusX. The 

 r. lateralis VII seems to be pecuhar to Amphiuma among the 

 amphibians. Its origin and distribution suggest a possible 

 homology with the r. laterahs recurrens VII of fishes, but in these 

 latter, as shown by Herrick (1899, 1900, 1901) and Clapp 

 (1898) the ramus recurrens, or lateralis accessorius, is primarily 

 a communis nerve, with which a few lateralis or general cutaneous 

 fibers may be associated. As shown above, there may occur an 

 anastomosis between the lateralis VII and the r. supratemporalis 

 X, suggesting a similar relation in fishes. In the trunk region 

 there occur some peculiar relations between ths laterahs VII and 

 the spinal nerves, but further study of this region will be necessary 

 before it will be safe to attempt exact comparisons. Kingsley 

 (1902b) in comparing the Caecilians and Amphiuma gives as one 

 of the supposed points of resemblance : "The occurrence in both 

 of a ramus lateralis recurrens branch of the facial nerve," but he 

 gives no further explanation. 



All of the branches of the r. jugularis, except those supplying the 

 anterior portion of the depressor mandibulae muscl<^, may contain 

 lateralis fibers. From the branches of the jugularis that pass 

 back into the posterior division of the depressor mandibulae 

 muscle there are given ofi^ two or three small lateralis twigs which 

 after emerging superficially from the muscle run posteriorly just 

 beneath the skin to supply a few of the more posterior of the 

 jugular series of neurom-asts. These commonly anastomose more 

 or less with the twigs of the lateralis branches that supply most of 

 the neuromasts of this series. The fore-going small lateralis 



