132 ON BREEDINa EXPERIMENTS WITH LEPIDOPTERA. [Feb. 20^ 



This hypothesis, with slight modification, leads to the results 

 observed in the cross grossulariata X lacticolor. If we suppose 

 that among the eggs the male-bearing all carry grossulariata, the . 

 female -bearing all lacticolor, w^hile in the sjjermatozoa there is no 

 coupling, so that we have male- and female-bearing of both kinds,, 

 we shall get the following results : — 



DR 2 gives eggs D J , R 2 . 



DR c? gives spermatozoa Dc?,Rj,D2,R$. 



Since in fertilization a male-bearing gamete must always meet 

 a female-bearing, the possible combinations of egg and spermatozoa 

 ai-e as follows : — 



(«) Egg D (5 X sperm. D § = zygote DD c? $ . 



„ Dj X „ R? = „ DRc? ?. 



„ R2 X „ Dc? = „ DR? 6. 



„ R .? X „ R d = „ RR $ c? . 



In the combination lacticolor ? x heterozygous J we shall 

 similarly have eggs Re?, R 5 , spermatozoa Dc5',Rc?,D$,R$ 

 giving combinations — 



(6) Egg R J X sperm. D $ = zygote DR c? ? . 

 „ R c? X „ R $ = ^, RR c? 2 . 

 „ R? X „ Dj = „ DR? d. 

 „ R? X „ Rd = „ RR? d. 



In the mating heterozygous $ x lacticolor d the eggs are 

 D (J , R ? , the spermatozoa R d , R $ , the combinations — 



(c) Egg D d X sperm. R ? = zygote DR d 2 • 

 „ R2 X „ Rd = „ RR2 cJ. 



It is now obvious that if the sex borne by the egg is uniformly 

 dominant over that carried by the spermatozoon, the results are 

 exactly in accordance with the observed phenomena. The sex 

 carried by the egg is that written first in the zygote columns, and 

 we get — 



In group («) DD d , DR d , DR 2 , RR 2 • 

 (5) DRd, RRd,DR2, RR2. 

 (c) DRd RR2. 



It is possible to get the same result in other ways, e, g. by 

 assuming coupling between the tw-o characters and the respective 

 sex-determinants in both eggs and spermatozoa and random 

 conjugation between them ; but in any case, if Castle's assumption 

 of coupling be taken for granted, it is necessary to assume that 

 it is always the egg which determines the sex. 



Note.— The sex-hypothesis here outlined seems at first sight to 

 be at variance with that propounded by Wilson (Journ. Exp. 



