250 R. R. HUMPHREY 



cells between the ends of the lobules at or near the periphery of 

 the testis. These cells are hypertophied, rounded or oval, with 

 eccentric and often irregular nuclei. They are packed with 

 lipoid of a comparatively insoluble nature; fuchsinophile granules 

 and mitochondria are reduced in numbers. The enlarged cen- 

 trospheres previously described cannot be seen. These cells 

 resemble the degenerate type already described; they seem, how- 

 ever, to have nuclei of greater vitality, and to disappear more 

 slowly. Although an occasional specimen killed in autumn may 

 possess hypertrophied, fat-laden cells which have doubtless per- 

 sisted through the summer months, in most animals such cells 

 are entirely lacking in August. In July, however, cells derived 

 from this type are fairly numerous; such cells range from the 

 size and content of the hypertrophied cell down to cells with 

 shrunken nuclei and but a single lipoid droplet or one or two red- 

 stained granules in their scant cytoplasm. Frequently, one finds 

 fragments representing the last stages of the nuclei of such cells. 

 Figures 35 to 39 show such a series of degenerate forms as is 

 mentioned above. With the passing of these cells the testis may 

 be said to contain no interstitial cells; the cells seen only as 

 flattened nuclei between lobules are, of course, capable of again 

 becoming modified at the now approaching close of the sperma- 

 togenetic cycle. 



/. The testis in immature males. Testes of three sexually im- 

 mature males have been examined. These were all fairly well- 

 grown animals, about 21 cm. in length, in which the wolffian 

 ducts were still small, straight, and empty, though two were 

 examined at a time (May) when the ducts of mature animals are 

 yet full of spermatozoa. The testes show no indication that 

 spermatozoa were formed in the preceding autumn; i.e., there 

 are present no traces of degenerated lobules. 



The testes are filled with lobules of secondary spermatogonia. 

 As would be expected after a study of the interstitial cells in the 

 adult, there are between these lobules only cells of the flattened 

 type. Some of these, in one animal, show small blackened drop- 

 lets, though these are by no means so numerous here as within the 

 Sertoli cells. This same animal possesses a few enlarged, fat- 



