Ch. I] 



FORMATION OF THE SEX-CELLS 



8 



chromatin-gramiles of the equatorial plate. Each of the twelve 

 chromatin-granules divides into two equal parts and the halves 

 migrate toward one or the other of the centrosomes (Fig. 1, D). 

 The cell-protoplasm next divides into two parts, so that two 

 new cells are formed. Each cell contains twelve chromosomes. 

 In this way the primitive sperm-cells continue to increase in 

 number by a series of cell-divisions, all like that just described. 



Fig. 2.— The formation of spermatozoa in Gryllotalpa. The two maturation-divi- 

 sions. (After vom Rath.) 



Second Period. A period of rest then follows, during which 

 the cells grow larger. During this time the chromatin is again 

 arranged in a fine network. 



Third Period. Two successive and most peculiar cell- 

 divisions now take place. The chromatin -network becomes 

 thicker, and forms a tangled skein of threads (Fig. 2, A, B). 



