146 R. R. HUMPHREY. 



too, that an unusual degeneration of germ cells, limited to any 

 one region, would reduce the size of the testis at that point, 

 producing either a slender extension of the organ (Fig. 4) or a 

 constriction between two regions of greater diameter (Fig. 5). 

 In Desmognathiis and other Urodeles (Diemyctyhis, Salamandra) 

 the peculiar pattern of spermatogenesis ultimately converts the 

 simple type of testis above described into a "multiple testis," 

 that is to say, a structure consisting of from two to five 

 simple testes joined in series by slender intermediate regions 

 containing only the central duct and a few surrounding primary 

 spermatogonia. Figure 6 indicates in outline the form of a 

 "multiple testis" of two lobes. The origin of this peculiar type of 

 testis has been discussed at length in a separate paper (Humphrey, 

 '22). In other species (the Plethodons, Gyrinophihis, Eurycea) a 

 "multiple testis" has never been encountered by the writer in an 

 examination of hundreds of specimens. The testis remains a 

 simple or unit structure, tapering anteriorly, more or less uniform 

 in diameter throughout its greater extent, and ending caudally 

 either in a bluntly rounded fashion (Fig. i) or as a slender 

 prolongation, variable in length, which I shall designate as the 

 caudal appendage (Figs. 4 and 8). This structure constitutes 

 the subject of the present study. 



Such an appendage will be encountered in practically every 

 adult Plethodon giutinosus male killed during the summer months. 

 It will be found in a majority of Gyrinopliilus males, but in only a 

 small percentage of Eurycea and Plethodon cinerius. Its length 

 varies, even in males of the same species, equal in size, killed at 

 the same time of the year. It may be so short as to be scarcely 

 distinguishable by gross examination, or it may approximate a 

 fourth of the total length of the testis. Its diameter, usually 

 rather uniform throughout, is but a fifth to a third that of the 

 testis immediately anterior to it. The two regions, as a rule, are 

 sharply differentiated as to size, the caudal portion or appendage 

 not increasing perceptibly in diameter towards its junction with 

 the larger "body" of the testis. (The two regions, indeed, may 

 even be separated by a slight constriction.) The caudal ap- 

 pendage would usually differ in appearance, then, from the 

 gradually tapering anterior end of the testis of figs. I to 7. It 

 would differ, too, from the similarly tapering posterior end of the 



