THE TESTIS 377 



plasm. Their cell outlines are often indistinct. These cells by 

 mitotic division produce two daughter cells, one of which retains 

 the structure and position of the mother cell, the other increases 

 greatly in size and, assuming a more central position, becomes a 

 spermatocyte. The subdivision of the spermatogonium marks the 

 initial phase of spermatogenesis. 



The spermatocytes, which arise by the division of the sperma- 

 togonia, are large cells. Their cytoplasm is finely granular, their 

 nucleus large, and its rich supply of chromatin is arranged in a 

 more or less skein-like manner. Because of the active mitosis oc- 



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FIG. 306. SEMINAL TUBULE OF A MAN IN TRANSACTION. 



a and 6, interstitial cells, the latter containing coarse granules ; c, connective tissue 

 cells ; d, a mast-cell of the connective tissue. Within the tubule, several phases of sper- 

 matogenesis are well shown. Highly magnified. (After Spangaro.) 



curring in these cells their nuclear membrane is usually absent or 

 indistinct. ' Mitotic figures are frequently observed in the sperma- 

 tocytes. As a rule two divisions, resulting in two generations, 

 occur in these cells ; hence the frequency of the double row of 

 large spermatocytes.. 



