Necturus Testis and Reproduction 59 



unknown manner, signals the hypertrophy of the interlobular cells sur- 

 rounding this region. With the subsequent degeneration of the distal 

 lobular portion, following the release of the spermatozoa, the interlobu- 

 lar cells continue to differentiate and eventually form what has been 

 termed the glandular tissue (see Fig. 2). This region was probably first 

 described in urodeles by Perez (1906), but the actual term glandular 

 tissue was first used by Champy (1913). Champy was so struck by the 

 change in color of the testes associated with the formation of the glan- 

 dular tissue, which is orange/ yellow due to the enormous lipid content 

 of the interlobular cells, that he likened its development to the corpus 

 luteum of the mammalian ovary, calling it a "veritable corps jaune 

 testiculaire." 



The development of the glandular tissue was described in Necturus 

 in a very extensive and comprehensive review by Humphrey (1921). This 

 study established that the glandular tissue was formed at the completion 

 of spermatogenesis and was composed, essentially, of hypertrophied 

 Leydig cells and remnants of degenerating lobules remaining at the close 

 of the breeding season. Since the Leydig cells only differentiate as the 

 lobules undergo spermiation, the evolution of the glandular tissue also 

 proceeds in a caudocephalic direction, following, as it were, in the wake 

 of spermatogenesis. 



Observations of N. lewisi testis towards the close of the breeding 

 season demonstrate the simultaneous occurrence of discrete regions dis- 

 playing different stages of germ cell development. Along the entire 

 length of the testes the lobules adjacent to the collecting duct consist of 

 short segments containing spermatogonial cysts (Fig. 3). It should be 

 mentioned that these immature segments are much longer in N. maculo- 

 sus at the same stage of testicular development. This possibly reflects a 

 more extensive period of spermatogenesis in N. lewisi, resulting in the 

 depletion of a greater number of spermatogonial cysts, which in turn 

 suggests a more extended breeding period for this species than N. macu- 

 losus. At the end of the breeding season the immature lobular segments 

 are mostly in a "resting" condition, although a number of mitotic fig- 

 ures were apparent in this region (Fig. 4). Thus, it seems that initial 

 germ cell replenishment can occur, albeit at a slow rate, long before the 

 main wave of spermatogenetic activity takes place. As has also been 

 demonstrated in N. maculosus (Pudney et al. 1983), in N. lewisi testis 

 the peripheral portions of the lobule undergo a marked longitudinal 

 variation in development. Progressing from the anterior to the posterior 

 end of the testis are seen: 1) highly distended lobules filled with bun- 

 dles of spermatozoa embedded in somatic cell cytoplasm (Fig. 5); 2) 

 recently emptied lobules containing residual spermatozoa embedded in 

 somatic cell remnants (Fig. 6); 3) lobules in a complete state of col- 

 lapse and regression (Fig. 7). These zones have no definite boundaries; 



