R. R. HUMPHREY. 



Though present, they have remained quiescent during the months 

 preceding the extrusion of the spermatozoa ; with the emptying oi 

 the lobule, however, or even somewhat previously in many urodeles, 



FIG. 2. Longitudinal section of a Desmognathus testis, showing a region 

 somewhat posterior to that pictured in Fig. i. Developing lobules are here 

 well defined and their relation to the collecting duct clearly indicated. 



they begin to multiply. By increase in their numbers the emptied 

 lobule is in time completely regenerated ; its germ cells again come 

 to maturity and the cycle of degeneration and regeneration is re- 

 peated. That a delay in the regeneration of a group of emptied 

 lobules would appreciably modify the form of the testis is self- 

 evident. Such delayed lobule regeneration, as a factor in the for- 

 mation of multiple testes, will be referred to subsequently. 



All the lobules of the urodele testis do not, as a rule, mature and 

 discharge spermatozoa at the same time. Examination of the testis 

 shows the older developmental stages of the germ cells to be local- 

 ized in its caudal region, while the earlier or younger stages are 

 found more cephalically. In the course of spermatogenesis a wave 

 of developmental change passes from the caudal to the cephalic 

 end of the organ. The lobules of any region, therefore, will con- 

 tain reproductive elements similarly advanced in development ; 

 caudal to any such region older stages are encountered while ante- 

 rior to it are successively younger stages. Finally, at the anterior 

 end of the testis will be found a slender cord or filament (see 

 Fig. i) containing only primary spermatogonia. 



