No. 611] GENESIS OF ORGANIZATION OF INSECT EGG 653 



duction of a definite part of the embryo, and hence of the 

 larva and adult, and that the cytoplasm is therefore 

 highly organized at the time the egg is fertilized. After 

 such experiments there is no regeneration of substances. 



As stated above, the cortical layer of cytoplasm is vis- 

 ibly alike throughout except at the posterior end, where it 

 has embedded in it the pole-disc granules. One of the 

 most interesting results of the operations performed with 

 the hot needle was obtained by killing the posterior por- 

 tion of the egg containing the pole-disc (Fig. 7). Eggs 



thus modified produced embryos without germ cells, prov- 

 ing that this cytoplasmic region is necessary for their 

 formation. The castration of the individual may also be 

 performed in a similar fashion after the germ cells have 

 been extruded from the egg (Fig. 3, d), and it is interest- 

 ing to note that sexless chicks have recently been pro- 



