266 MARY T. HARMAN. 



spindle fibers are fine but distinct. The astral rays are similar 

 to those of the spermatogonial divisions. In the late anaphases 

 the centrosome is no longer visible and the spindle fibers are 

 indistinct. There seems to be no resting stage between the 

 first maturation division and the second maturation division. 



The chromosomes of the second spermatocyte are ovoid. 

 Metaphase plates show six and seven chromosomes (Figs. 23 

 and 24. The accessory cannot always be distinguished from 

 the other chromosomes. It is either the second or the third 

 largest. It divides in this division and passes to the poles 

 in advance of the others (Fig. 25). In the late anaphases all 

 the chromosomes have coalesced, although the number may yet 

 be distinguished (Fig. 26). By the time the chromosomes have 

 reached the poles they form a diffuse mass of chromatin at 

 each pole, and the cell has begun to constrict in the middle. 



The centrosome which is similar to the centrosome of the 

 primary spermatocyte has disappeared. The spindle fibers have 

 become indistinct. As the constriction of the cell is completed 

 the chromatin has migrated to the center of each daughter cell. 



In the changing of the spermatid into the spermatozoon two 

 things are conspicuous from the beginning, the changes in the 

 character of the chromatin and the elongation of the cell body. 

 From the diffuse irregular mass there is formed an ovate body 

 with the chromatin in a coarsely reticular condition largely 

 around the periphery of it. The cell becomes elongate and larger 

 at one end than at the other. The cytoplasm has changed from 

 the tangled network to fibrillar strands of granules extending 

 longitudinally across the cell. The cell wall is quite distinct. 

 This condition is illustrated in Fig. 29. The spermatid continues 

 to elongate. The nucleus becomes spherical and remains at 

 one end of the spermatid. The more granular cytoplasm lies 

 toward the periphery of the tail-like elongation. There is a 

 portion of the cytoplasm extending from the nucleus through 

 the center of the tail wilich is more finely granular than the 

 remainder and takes the stain less readily. Part of the chromatin 

 has become massed together, forming a sphere situated to the 

 side of the nucleus near the end of the lightly staining area of 

 the tail. The greater part of the remaining chromatin is dis- 



