270 
GERM-CELL CYCLE IN ANIMALS 
E 
Fic. 73.— Rhabditis nigrovenosa. Stages in maturation, fertilization, 
and cleavage. A. Odgonium with twelve chromosomes. B. Sec- 
ond maturation division. Pronucleus and second polar body each 
with six chromosomes. C. Primary spermatocyte. D. Division of 
primary spermatocyte. FE. Second spermatocyte division; one 
chromosome delayed. F. Two spermatozoa each with six chromo- 
somes. G. Cleavage spindle of egg showing two groups of chromo- 
somes; one with six contributed by the egg, the other with five 
contributed by the sperm. (After Schleip, 1911.) 
