CASTLE : THE HEREDITY OF SEX. 



211 



furnished by the recessive parent. If gametes of opposite sex always 

 unite in fertilization, and the sex-character borne by the hybrid gamete 

 always dominates, the resulting zygotes will be D (R) ^ and E 9 • 

 See Table IV. But if dominance attaches to the gametes of one 

 joarent as often as to those of the other, the result will be D(R) ^ + 

 D (R) 9 + R (? + R 9. Manifestly neither of these results agrees 

 closely with the one observed, which lies between the two. It seems 

 probable, then, that if coupling does occur, it occurs not in all possible 

 cases, but only in a part of them. 



TABLE IV. 



Sex-distribution among offspring of Aglia tail (R) crossed with its aberration 



lugens (D). Compare Table III. 



NoTK. Numerals in italics indicating the observed disiribution are, for conve- 

 nience in comparison, inserted immediately belovv the calculated numbers. 



Suppose that it occurs in only one-third of them ; then the gametes 

 of the hybrid will be 2 D ^ + D 9 + R c? +' 2 R 9 . If such gametes 

 meet others all of which are R, as in a cross with a recessive individual, 

 and if sexual dominance is 2wssessed hi all cases hy the gamete of the hybrid 

 parent, we get the following distribution of zygotes, 2 D (R) J + D 

 (R) 9 + R (? + 2 R 9 , whicli, as we have seen, is close to that ob- 

 served. Compare Table IV., Generation IV. [1] and [3]. On the other 

 hand, the assumption that sexual dominance is possessed as often by 

 the gamete of one parent as the other would lead to the result normal 



