2Q2 FRANZ SCHRADER. 



well as in embryonic stages and I am induced to regard Buchner's 

 figure of a multipolar spindle as an exceptional case. That such 

 may occur I have no reason for denying, and it is indeed strange 

 that abnormalities are not the rule rather than the exception in 

 all of the mycetocytes. 



The size of the cells is not proportionate to the increased 

 amount of chromatinic material. It is augmented considerably 

 when compared with that of the giant cells in the time of first 

 association with the symbionts, but never reaches the dimensions 

 that one would expect from an examination of the contained 

 chromosomes. 



GENERAL CONSIDERATIONS. 



Breest's and Strindberg's conclusions that mycetocytes arise 

 from the yolk cells may safely be discarded as far as Pseudococcus 

 is concerned. By Strindberg's own definition, yolk cells are 

 cleavage cells which have been left behind after the general 

 migration to the periphery to establish the blastoderm. The 

 giant cells however, which are the direct progenitors of the myce- 

 toctes, arise even before the migration of cleavage cells is com- 

 plete, and therefore before the yolk cells have been established 

 as such. 



Pierantoni's conclusions have already been taken up in my 

 previous paper ('23). Undoubtedly he is correct in his explana- 

 tion that the cleavage cells wander in among the symbionts, but 

 in Pseudococcus I consider this association, if such it can be called, 

 as one of the most temporary nature. It is the natural conse- 

 quence of the general peripheral migration of cleavage cells. 



The whole series of developments, as here described, seems 

 extraordinary. And yet, most of the stages regarded individually 

 are not unprecedented; the processes involved have been de- 

 scribed before in other forms. 



A fusion of polar bodies and the persistence of the polar nucleus 

 thus formed has been described in several polyembryonic Hymen- 

 optera. The formation of a polar nucleus is therefore not the 

 only case among insects. It is indeed only rarely that such in- 

 stances are met, but the old assumption that polar bodies never 

 develop in a normal case of embryology certainly does not hold. 

 That the polar nucleus does not behave like the female pronu- 



