THE P^DOGENETIC FLY, MIASTOR 57 



The nuclei present at the four-cell stage occupy 

 rather definite positions and may be numbered for 

 convenience by the Roman numerals I, II, III, 

 and IV, as indicated in Fig. 15. The division from 

 the four- to the eight-cell stage is a very important 

 one, since it is at this time that the primordial 



^ fa 



ilf ffcf 



&-- : :&i3& 



FIG. 16. Miastor metrcdoas. Stages in the chromatin-diminution 

 process. (From Kahle, 1908.} 



germ cell is established. Each of the four nuclei 

 divides by mitosis, but nuclei I, II, and III undergo 

 a chromatin-diminution process during which a 

 large part of their chromatin remains in the cyto- 

 plasm when the daughter nuclei reform. The details 

 of such a process are indicated in Fig. 16. Nucleus 

 IV, on the other hand, divides as usual (Fig. 15) and 

 each daughter nucleus receives one-half of its chroma- 

 tin. One of these daughter nuclei becomes embedded 

 in that peculiar mass of cytoplasm at the posterior 



Mp 



