246 R. R. HUMPHREY 



arises from poorly preserved mitochondria, which, according to 

 his description and figures, are very nmnerous in the interstitial 

 cells of the opossum. In Necturus, however, the fuchsinophile 

 granules must be responsible for the artifact, as it never occurs 

 prior to their being present in considerable numbers. In the pri- 

 mary spermatogonia of Necturus, moreover, in which mitochon- 

 dria are particularly numerous, I have not been able to find such 

 an artifact, even in sections showing it best in the interstitial 



cells. 



The granules and lipoid droplets, from their early appearance, 

 are not distributed uniformly throughout the cytoplasm. In 

 cells cut in the proper plane, as in figures 28 and 30, a small area 

 at one side of the nucleus appears free from granules, 'which, 

 however, are often far more numerous at the immediate per- 

 iphery of the area than in other parts of the cell. The nucleus, as 

 soon as cell boundaries are distinguishable, is seen to lie at one 

 side or end of the cell; the area mentioned, clearly an idiozome, 

 lies on that side of the nucleus toward the center of the cell. In 

 early stages this idiozome is relatively very small, and centrioles 

 are difficult to distinguish except when seen during mitosis, at 

 which time they stain sharply. As the cells increase in size, how- 

 ever, the centrosphere becomes greatly enlarged. In the cells 

 of the caudal third of the testis, on October 30th, are centro- 

 spheres from half to three-fourths- the diameter of the nucleus. 

 The material composing them is gathered about a distinct 

 centriole as a center; two centrioles may be seen occasionally. 

 It often appears to differ from the other cytoplasm of the cell 

 in its tendency to st'ain faintly with the basic stain. Immedi- 

 ately around the centriole there appears a small area of rather 

 dense homogeneous material, outside which are faint cytoplasmic 

 radiations extending to the periphery of the centrosphere. In 

 earlier stages there is no sharply defined boundary between the 

 centrosphere and the surrounding granules, but in the spring 

 months centrospheres frequently appear to have a peripheral zone 

 of more dense material inside which the granules are .not seen 

 (fig. 31). The centrosphere is then more clearly delimited. 

 In a few of the most extreme cases this peripheral zone has the 

 appearance even of a' distinct membrane. 



