202 



J. S. NICHOLAS 



A-UVER 

 t -HEART 

 ® -CHORDA 

 A -THYROID 

 O-NEPHROS 

 X- INTESTINE 

 • -ERYTHROCYTES 

 T-MELANOPHORES 



+ -skeletalmuscl£ 



Figure 2. The His concept of localization in the chick blastoderm compared with 

 Rudnick's summary of present findings in this form. 



most of the remaining nuclei rather suddenly emerge from the central 

 deutoplasmic mass and are regularly arranged in a peripheral position, 

 where they remain, forming a single boundary layer completely enclos- 

 ing the remainder of egg materials. The pole cells remain separate from 

 the underlying blastoderm. 



The events described can be regarded as the first generalized move- 

 ment of material within the egg of Drosophila. The deutoplasm still con- 

 tains a few nuclei, the yolk nuclei, which for some reason did not move 

 towards the periphery. During this process the fused polar bodies have 

 undergone a series of transformations during which the nuclear cycle is 

 synchronized directly with that of the blastoderm nuclei. Eventually the 

 polar body disappears and its chromatin disintegrates and is resorbed 

 into the general deutoplasmic mass. 



After the nuclei have taken up their peripheral position and undergone 

 three mitoses, they incorporate some of the egg cytoplasm immediately 

 beneath them together with the cortical cytoplasm into a deep layer 

 which will become cellular material. Shortly afterward, cytoplasmic 



