122 



GENERAL EMBRYOLOGY 



number, through continued mitosis, they begin to increase in 

 size, though not nearly to the same extent that the oogonia do. 

 There is not always the same distinctness between the phases 

 of multiplication and growth here, and the two final divisions 

 of the full grown spermatogonial cell, then known as the 



FIG. 68. Diagram of a section through part of the testis of the rat, showing 

 some stages in spermatogenesis. From Korschelt and Heider, after Lenhossek. 

 bz, basal cells; spc, spermatocytes; spg, spermatogonia; spt, spermatids; spz, 

 spermatozoa. 



primary spermatocyte, are the reducing or maturation divisions. 

 These lead, as we have seen, to the formation, from each primary 

 spermatocyte, first of two secondary spermatocytes, both alike, 

 and then to four spermatids, all alike. The cells of the column 

 then become arranged so that groups of spermatids become 

 related with each of the basal cells, which often leave their 



