184 NUCLEOCYTOPLASMIC RELATIONS 



Boveri (1915) studied them and concluded that the male parts 

 were inherited from the mother and the female parts from both 

 parents. He suggested that the sperm had not united with the egg 

 pronucleus but with one of the cleavage nuclei ( Fig. 7 ) . The dis- 

 covery by P. W. Whiting (1924) of a haploid mosaic male, mo- 

 saic in traits inherited from a heterozygous mother, prompted the 

 hypothesis that two products of meiosis had survived and the 

 eggs were binucleate. In 1932, P. W. Whiting discovered a 

 Habrobracon gynandromorph in which the female part came 

 from the sperm and one set of the heterozygous mother's markers 



FERTILIZATION OFA CLEAVAGE NUCLEUS 

 (BOVERI) 



FERTILIZATION OF ONE OF TWO PRONUCLEI 

 (WHITING) 



ZYGOTE FORMATION AND ACCESSORY SPERM NUCLEUS 

 (WHITING AND ROTHENBUHLER) 



Fig. 7. Diagrammatic representation of three possible mechanisms for 

 gynandromorph fonnation in Hymenoptera. 



whereas the male portion came from the other set of the mother's 

 markers. This gave strong support to the hypothesis that gynan- 

 dromorphs resulted from fertilization of one of the meiotic 

 products of a binucleate egg (Fig. 7). This is an acceptable al- 

 ternative to Boveri's hypothesis of fertilization of the cleavage 

 nuclei, and, in explaining the origin of this Habrobracon gynan- 

 dromorph, Boveri's hypothesis fails. 



Meiotic Block. The meiotic block in Habrobracon must be 

 under genetic control, since lack of control is inherited in the 

 lemon lethal stock. Other than this, little is known. Is the block 

 intrinsic? Is there some agent in the egg cytoplasm which inhibits 



