THE CHROMOSOMES 



79 



nal in origin. They divide as do the other cells of the 

 body for a lonff time. At each division each chromo- 

 some splits lengthwise and its halves migrate to op- 

 posite poles of the spindle. 



^«- 



cMp 



cR 



•cad 



Fig. 33. — o, Section of egg of Calligrapha bigsbyana, 

 showing "germ-cell determinants" (granules), g c d, 

 at posterior end of egg; b, posterior end of a later 

 stage of same, showing primordial germ-cells; c, Sec- 

 tion of egg of Miastor, showing single primordial 

 germ-cell at posterior end. (After Hegner.) 



But there comes a time when a new process ap- 

 pears in the germ-cells {jigs. 34 and 3.5). It is 

 essentially the same in the ^gg- and in the sperm- 

 cells. The discovery of this process w^e owe to the 

 laborious researches of many workers in many coun- 



