304 L- J- BACHHUBER. 



entirely surrounded by nuclear material (Figs. 41, 42, 43). The 

 entire nucleus then migrates to one side of the cell and gradually 

 leaves behind all, or very nearly all, of the cytoplasm, together 

 with the chromatoid body (Figs. 43, 44, 45). At the same time 

 the entire nucleus begins to condense and finally forms a flat 

 plate, which has at times, however, the appearance of a convex 

 plate (Fig. 46). In the meantime the sperm tail has been 

 formed from the cytoplasm with the centrosome in the neck. 

 The nucleus, now the sperm head, gradually enlarges with a 

 resultant diminution of staining capacity. In properly stained 

 sections and smears there can occasionally be distinguished a 

 number of darker staining bodies one of which is usually larger 

 than the others. The number of these approaches very nearly 

 the number of chromosomes which went into the sperm head. 

 It is thus possible that the chromosomes retain their individuality 

 even in the fully developed spermatozoa (Figs. 47, 48). As the 

 sperm head enlarges, these dark-staining bodies gradually diffuse 

 through the entire head (Figs. 49, 50). Further enlargement 

 brings about the complete development of the spermatozoon. 

 The head manifests an even staining capacity, the neck shows 

 the presence of the centrosome, while the tail takes such a light 

 stain that it is barely visible (Fig. 51). 



7. CONCLUSIONS. 



1. The number of chromosomes in the spermatogonium is 

 probably twenty-two. 



2. The number in the primary spermatocytes is placed at 

 twelve. 



3. The number in the secondary spermatocytes is placed at 

 eleven. 



4. Two accessory elements, an X and a Y, are present. One- 

 half of the spermatozoa contain the X, and the other half, the 

 Y element. 



5. A chromatoid body is present. Its function was undeter- 

 mined. It underwent no division, and was finally cast off with 

 the excess cytoplasm in the metamorphosing spermatid. 



