276 GENETICS 



Even before chromosomes were known, Dzierzon 

 postulated that males of this group (drones) are 

 formed from unfertilized eggs, and females (worker 

 and queens) from fertilized eggs, a view which has 

 been substantiated by both cytological and genetical 

 observations. Newell has shown that in the cross be- 

 tween Italian (gray) queens and German (dark) 

 drones, as well as in reciprocal crosses, the male off- 

 spring are purely maternal, while the females are 

 hybrid in character. Cytological observations by 

 Petrunkevitch and by Nachtsheim have also estab- 

 lished the validity of the Dzierzon theory. 



Coupled with this, studies on the spermatogenesis 

 of hymenoptera have revealed the fact that the sper- 

 matogonia possess solely the haploid number of chro- 

 mosomes, and in order, therefore, that this number be 

 not further reduced in the process of maturation, only 

 one division of chromatin takes place. In the first 

 spermatocyte division of the honey bee all the chro- 

 matin passes to a single chromosome, only a minute 

 degenerate non-chromatic globule being formed at the 

 other pole of the spindle. In the second spermatocyte 

 division the chromatin divides but one of the sper- 

 matids is very small and degenerates. Thus, instead 

 of four spermatids, only one is formed and this one 

 contains the haploid number of chromosomes. 



Variations of this process are found in other 

 hymenoptera which frequently result, in the formation 

 from the larger second spermatocyte, of two separate 

 spermatids each possessing the haploid number of 

 chromosomes. 



