INTERSTITIAL CELLS OF URODELE TESTIS 223 



viridescent animal. Through the courtesy of Dr. Bertram G. 

 Smith, a somewhat less complete series of testes of Cryptobran- 

 chus alleghaniensis was at my disposal — a series including imma- 

 ture males as well as sexually mature animals taken in the months 

 of ]May to September, inclusive. Some material from Plethodon 

 erythronotus, Plethodon glutinosus, Spelerpes bilineatus, Am- 

 blystoma punctatum, Gyrinophilus porphyriticus and an Euro- 

 pean form, Salamandra atra, was also examined, but of none 

 of these last-named animals have sufficient specimens as yet been 

 secured to constitute even a partially complete series. For 

 comparison, however, with conditions in the other animals at 

 similar stages of the spermatogenetic cycle, this material has 

 proved of no little value. 



Structure of the urodele testis 



The testes of urodeles, as of all amphibia, are abdominal in 

 position. They are more or less elongated structures attached 

 to the dorsal body wall by a mesorchium in which are the vasa 

 efferentia, leading from the testis to the vas deferens, as well as 

 the afferent and efferent blood vessels of the organ. The testes 

 of Desmognathus, Plethodon, and Spelerpes are highly pig- 

 mented externally; Salamandra, Amblystoma, and Diemyctylus 

 have testes free, as a rule, from pigmentation; Necturus has an 

 irregular mottling of pigment splotches, varying with the indi- 

 vidual animal, from almost complete pigmentation (rare) to 

 complete absence of pigment (rare). There is apparently, in 

 Necturus, no definite relation of pigmentation to period in the 

 spermatogenetic cycle as there is in the deeply pigmented testes 

 of Desmognathus, in which pigmentation diminishes with the 

 expansion of the organ, to increase as the organ shrinks during 

 the regressive changes following the completion of the cycle. 



The structure of the urodele testis requires detailed considera- 

 tion, since as has been stated it is an organ exhibiting, in compari- 

 son with the testes of higher animals, a much more complete 

 isolation of the different stages of the spermatogenetic process. 



