THE MULTIPLE TESTIS OF URODELES. 65 



fication in the two organs of those growth, degeneration, and re- 

 generation processes which make a multiple testis possible. 



In the writer's opinion, no particular phylogenetic significance 

 attaches to this peculiar type of testis. It occurs in several mem- 

 bers of the family Salamandridse ; Champy mentions it in numer- 

 ous European tritons and salamanders, and I myself have observed 

 it in our two American members of the family. If axolotl, on tht 

 other hand, possesses a multiple testis, as Champy states, it differs 

 from its near relative, Amblystoma punctatum. 1 Among the Ple- 

 thodontidse, too, Desmognathus stands alone, no other member of 

 the family, to my knowledge, possessing a multiple testis. Since 

 the plan of spermatogenesis in Necturus or Cryptobranchus in 

 fact, in any of the urodeles I have examined differs from that in 

 Desmognathus or the Tritons in no fundamental way, a multiple 

 testis might arise in any of these urodeles if the spermatogenetic 

 processes became sufficiently reduced in rate. In this way, prob- 

 ably, 'have the species now possessing multiple testes arisen from 

 ancestors with organs of the simple type. Such slowing of the 

 reproductive processes in phylogeny might possibly be interpreted 

 as due to deterioration in the vigor of the stock; the writer sees 

 neither in it nor in the resulting structure of the testis any par- 

 ticular adaptative value. 



SUMMARY AND CONCLUSIONS. 



1. Multiple testes of two or more enlargements or lobes sep- 

 arated by intervening non-functional regions are of common occur- 

 rence in Desmognathus and other urodeles. 



2. Such multiple testes are observed only in larger males. The 

 smallest sexually mature males have testes of but a single lobe. 



3. A study of the manner in which new lobes appear indicates 

 the following mode of origin : 



1 Spengel says : " Beim Axolotl erscheint er (the testis) als eine breite, 

 dicke, von zahlreichen Unebenheiten besetzte Platte." This description is 

 somewhat more applicable to the testis of Amblystoma punctatum. Irregu- 

 larities, however, are to be observed in the testis of Amblystoma only in the 

 spring when the lobules are emptying, and are in no case so extreme as to 

 be at all similar to the lobes of a true multiple testis. It may be questioned 

 whether the " lobes " described by Champy in axolotl are similar in origin 

 to those in Desmognathus and the tritons, or whether they are merely such 

 " Unebenheiten " as Spengel mentions. No other investigator has described 

 the testis in axolotl as being of the multiple type. 



