L. DONCASTER 



17 



it has been shown that eggs with 27, fertilized by sperm with 28, 

 give rise to females with 55, while eggs with 28 give rise to males 

 having 56. Since the rjrossidariata factor is normally transmitted only 

 by the male-producing eggs, it must be supjaosed to be associated with 

 the extra chromosome in the male-determining egg. If, however, the 

 male factor M and the gross, factor G are not borne in one indivisible 

 chromosome, but in a compound chromosome (such as has been de- 

 scribed by Seller in eggs of the moth Phvarjniatobiu), and if in these 

 exceptional cases the compound chromosome separated into its com- 

 ponents, so that the G portion remained in the egg and the M portion 

 went into the polar nucleus, an egg would then be produced which was 

 female-determining, bore G, and had 28 chromosomes. Such an egg 

 when fertilized by a lacticolor male would give rise to a r/rossulariuta 

 female with 56 chromosomes, instead of the normal result, namely, a 

 lacticolor female with 55. Diagrams will make this clearer. 



Gross. ? with .55 



Eggs 



Offspring 



A. Normal Case. 



.'54 + il/G 5ih1Mu lact. male with ,56 



27 + JI/17 27 + il/(/ spermatozoa 



5i + Mg 



lact. female 



55 chromosomes 



54 + MG + Mg 

 gross, male 

 56 chromosomes 



Gross, s with 55 



Eggs 



B. Exceptional Case. 

 5i + 31G 54 + 2J/3 lact. male with 56 



54 + ,% -tG 



gross, female 



56 chromosomes 



Journ. of Gen. iv 



27 + G 27 + jI/ 27 + il/y •n + 3Icj spermatozoa 



bi + M+Mg 



lact. male 



56 chromosomes 



