Fig. 30. DirrERENTiATiosr of Germ Cells and Somatic 

 Cells Ix the Egg of Ascaris. A and B, second cleavage 

 division showing that the chromosomes remain entire in the 

 lower cell, which is in the line of descent of the sex cells 

 ("germ track"), but that they throw off their ends and break 

 up into small granules in the upper cells, which become 

 somatic cells. O, 4-cell stage, the nuclei in the upper (somatic) 

 cells being small and the ends of the chromosomes remaining 

 as chromatic masses in the cell body outside of the nuclei, 

 while the nuclei in the lower cells are much larger and con- 

 tain all the chromatin. D, third nuclear division, showing the 

 somatic differentiation of the chromosomes in all the cells 

 except the lower right one, which alone is in the germ track 

 and will ultimately give rise to sex cells. (After Boveri.) 



