Necturus Testis and Reproduction 



57 



N. lewisi. The interlobular cells associated with the immature region of 

 seminiferous lobules, or those surrounding lobules containing develop- 

 ing germ cells appear, morphologically, to be undifferentiated (see Fig. 

 2). When, however, the lobules undergo spermiation this, in as yet an 



maturing lobules 

 • medial zone 



caudal zone 



ANNUAL 

 REGROWTH 



tunic 



• all zones 



Fig. 2. Diagrammatic representation of N. maculosus testis towards the close of 

 spermatogenetic activity. Seminiferous lobules (clear areas) containing the germ- 

 inal elements empty into the main, central, longitudinal collecting duct. Lobular 

 portions adjacent (proximal) to this duct contain immature germ cells that act 

 as a reservoir for successive bouts of spermatogenetic activity. Mature germ cell 

 cysts are in lobular portions distal to the collecting duct. Lobules are sur- 

 rounded by an interlobular tissue (grey areas), development of which depends 

 upon the state of differentiation of the lobules. The kinetics of spermatogenesis 

 are indicated by arrows showing the proximal to distal development of germ 

 cells (annual regrowth) and the caudocephalic differentiation of germ cells that 

 occurs in distal portions of the lobules and their associated interlobular tissue 

 during the annual breeding season (maturational wave). From Pudney et al. 

 (1983). 



