MATURATION OF THE GERM-CELLS 47 



there is a parallel reduction in the number of chromosomes to 

 one-half. 



Fig. io. — Spermatogenesis and polar bodies. (After Hertwig and Weis- 

 mann.) 



A', Primitive sperm-cell of Ascari% megalocephala, var. bivalens, with four chromosomes; 

 B", sperm mother-cell (eight chromosomes) ; C, two spermatocytes formed, each with four 

 chromosomes ; D', four spermatozoa formed, each with two chromosomes ; A, primitive 

 egg-cell with four chromosomes ; B, fully developed o\aim, with eight chromosomes ; C, for- 

 mation of first polar body (pb. i) which di\'ides into two, each with two chromosomes ; D, 

 formation of second polar body (pb. 2). The nucleus of the now mature ovum has two 

 chromosomes, like the ripe spermatozoon. 



" The one fact of maturation that stands out with perfect 

 clearness and certainty amid all the controversies surrounding it 

 is a reduction of the number of chromosomes in the ultimate germ- 

 cells to one-half the number characteristic of the somatic cells. It 

 is equally clear that this reduction is a preparation of the germ- 



