FIG. 64. Behavior of chromosomes during maturation, fertilization, 

 and cleavage of Ancyr acanthus cystidicola. (From Mulsow, 1913.) 

 A. Spermatogonium with eleven chromosomes. B. First matura- 

 tion (spermatocyte) division. The single chromosome finally joins 

 one group. C. The four spermatids arising from one spermatocyte ; 

 two with six chromosomes, and two with five. D. Two sperma- 

 tozoa drawn while alive ; one with six chromosomes, and one with 

 five. E. Oogonium with twelve chromosomes. F. Second matura- 

 tion (oocyte) division. The black mass above is the first polar 

 body; the set of six black chromosomes are those of the second 

 polar body; the six dotted chromosomes are those of the egg. 

 G. Fertilized (male producing) egg ; sperm nucleus above with five 

 chromosomes; egg nucleus below with six chromosomes. H. Fertil- 

 ized (female producing) egg ; both egg and sperm nuclei with six 

 chromosomes. /. Cleavage stage of male producing egg ; the central 

 cell with nucleus containing eleven chromosomes. J. Cleavage 

 stage of female producing egg ; the lower cell with nucleus contain- 

 ing twelve chromosomes. (257) 



