180 



NORTH AMERICAN FAUNA 74 



nuclei, resembling those of intermediate or type B spermatogonia, seemed to be 

 degenerating and advancing toward the center of the tubules. Similar conditions 

 were seen also in the testes of a 1 -year-old male collected in the first days of June. 

 The tubules in the latter were smaller (39-57 fim) than those of the newborn 

 males. 



The germ cells in the testes of 2-\ ear-old animals (two specimens) were similar 

 to those of the newborns, but the seminiferous tubules were somewhat larger 

 (49-81 fim), still \\ ithout a lumen. The same was true of one 3-year-old. which 

 had, howexer. both t\pe A and t\pe B spermatogonia centrally. The diameter of 

 the seminiferous tubules in this animal ranged from 70 to 81 /xm. Three animals 

 taken in No\ ember and December of their fourth year had testes in which type A 

 spermatogonia predominated, and there \\as much cellular debris centrally. 

 Tubule diameters in these ranged from 36 to 73 /mi. Two others in December of 

 their fifth and sixth years were the same, with tubule diameters of 48 to 69 ^m. 



Two 5-year-olds and two 6-year-olds taken in May and early June were 

 somewhat more ad\anced in testicular development, having mainly type B 

 spermatogonia and a few primary and secondar\- spermatocytes. However, three 

 of them still lacked any appreciable central lumen in the tubules. \\ hich were 90 

 to 107 ixm in diameter. Another 6-year-old taken in July was in the same 

 condition. The seminiferous tubules of five males taken between late November 

 and the end of Februar\- of their seventh \ ear. were small (54-97 jim) and. with 

 one exception, were comparable to the 5- and 6-year-olds in regard to cellular 

 components. The exceptional one (6.6 years on 6 December) had a few 

 spermatids as well, some of which seemed to be mature. Two other animals 

 taken in late March of their seventh year had much larger tubules (117-167 fim) 

 with a small lumen, but neither contained any spermatozoa. In one of the March 

 specimens, only Sertoli cells and spermatogonia were present; in the other were 

 signs of retrogression, with spermatid giant cells and much other debris in the 

 lumen. A 7-year-old specimen taken on 2 June also showed tubules in retrogres- 

 sive condition. 



The youngest animal in my series that had seminiferous tubules containing 

 clusters of apparently mature spermatids and free spermatozoa in the lumen was 

 an 8-year-old taken on 26 April. The tubules in this animal were about 150 in 

 diameter. Another 8-year-old, taken on 25 Ma\-. was retrogressive, with giant 

 cells and cellular debris in the lumina. None of four ninth year males taken in 

 November-December \\ as potent, but one 9-\ear-old taken on 25 May appeared 

 to be retrogressive, possibh" ha\ing achieved potency some time earlier. One of 

 three animals, taken in No\ ember to March of their 10th year was potent, as 

 w ere four 10-year-olds taken in April-Ma\-. One taken in August at 10.2 years 

 and four in November-December at 10.5 to 10.6 \ ears were not potent. One at 

 10.8 years taken on 19 Februar\- was potent and fertile; it had spermatozoa in 

 the body of the epididymis as well as in the testes. The apparent nonpotenc\- of 

 many of the young males that were taken from July to December is not 

 necessarily diagnostic of reproducti\e incapability, for most subadults seem not 

 to come into breeding condition until mid- winter to late winter. 



The implication from this small series is that some males may attain potenc\- as 

 early as their seventh winter or spring, but most probably attain that state no 

 earlier than the eighth or ninth winter. These findings are similar to those of 



