258 



EVOLUTION AND ANIMAL LIFE 



of its small number of chromosomes (two in variety univalens, four in 

 bivalens), their large size, and the diagrammatic clearness of the 



FIG. 146. Reduction of the chromatin in the cleavage of the egg of A scaris mcgalo- 



cephala var. univalens. (After Boveri.) 



changes which take place in division. In the division of the fertilized 

 egg cell we have two (in univalens) long chromosomes handed over to 

 each daughter cell. As these two cells in turn divide, a striking 



