No. 3.] ORIGIN OF THE SPERM-BLASTOPHORE, 



Usually, after the peripheral cells have divided, the central 

 cells become granular and appear homogeneous ; the nuclei and 

 cell membranes can no longer be distinguished (Fig. 5). In 

 other words, the central cells degenerate at this period and 

 become transformed into a cushion for the spermatozoa. This 

 cushion is called the " sperm-blastophore " by Bloomfield. 



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FIG. 5. 



FIG. 6. 



FIG. 7. 



(Occasionally this transformation of the central cells occurs 

 previous to the division of the peripheral cells, Fig. 6). The 

 daughter-cells produced by the several divisions of the sper- 

 matocyte become half the size of the mother-cells, and retain 

 this size throughout the stages of formation of the sper- 

 matozoan. These half-sized cells are the spermatids. 



IP 



FIG. 9. 



FIG. 10. 



FIG. 



3. SpcrmatiJs.--T\\Q spermatids encircle the blastophore 

 (Fig. 5), which changes to a spherical form and becomes more 

 conspicuous than in the former stage. The spermatids now 

 undergo repeated cell division, producing an enormous number 

 of new spermatids (Fig. 7), which gradually elongate (Figs. 8, 

 9), and finally become tailed spermatozoa (Figs. 10, 11). The 



