94 



THE DETERMINATION OF SEX 



way there arise two kinds of spermatozoa. When an egg is 

 fertilized by a spermatozoon that contains an accessory ele- 

 ment, a female is produced. 



Miss Stevens 46 has published a series of papers on the devel- 

 opment of the sexual elements. Fig. 41 represents the alter- 



'- X 



FIG. 41. Diabrotica. a-d, D. vittata; e-f, D. soror; a, dissolution of the con- 

 tracted chromosome (first stage after synizesis); b-d, transformation of the nucleus 

 of the first spermatocyte; x, the accessory chromosome; e-f, division of the nucleus 

 of the first spermatocyte. After N. M. Stevens. 



ations as found by her in a beetle, Diabrotica. b, c, d show 

 the accessory chromosome clearly, e and / show us the 

 first division. Half of the daughter cells of the first division 

 have an accessory chromosome, which, however, divides at 

 the second division. The process differs from that in Anasa, 



