The Chromosomes of Euschistus variolarius, Eusdiistus servus etc. 503 
The only exceptions 'whicli we recall are the cases of exclusively 
female characters in certain species of butterflies, Colias philodice, Colias 
edusa and Papilio memnon. In Colias, for example, the females have 
either yellow or white wings, whereas the wings of the niales are always 
yellow. ’WTiite wings, therefore, in this species, are an exclusively female 
character, very niuch as the genital spot of E. variolarius is an exclu- 
sively male character, with the important clifference, that the spot of vario- 
larius is characteristic of all the males, whereas white wings are not 
characteristic of all the females of C. philodice, the females having either 
white wings or yellow wings. 
These two sex-limited characters have another feature in common. 
The spot of variolarius can be transmitted through the female when 
she is crossed with a species which has no spot, and the white 
wings of these butterflies can be transmitted through the yellow- 
winged male. 
These facts in the butterflies have been explained by Gerould 1911, 
on the assumption that white -wings are dominant in the females, and 
recessive in the niales ; but this does not explain the fact that white wings 
are completely absent from all the F 2 males, whereas theoretically they 
should be present in 25 per cent of these males. Gerould suggests a pos- 
sible explanation on the assumption that for some reason the males that 
have the white wings do not survive. This solution of the difficulty is 
criticised by Goldschmidt (’12), who attempts to explain the fact by 
theoretical assumptions of his own. 
He assumes : 
First: that each sex has the factors for both sexes. 
Second: that the female is heterozygous for the male sex, and ho- 
mozygous for her own sex^). 
Third: that the male is homozygous for both sexes. 
Using the letter G to designate the factor for the female secondary 
sexual characters, and the letter A for the factor for the male secon- 
dary sexual characters, his formulae for the two sexes are as follows: 
$ F F G G Jil m A a 
(JFF G G MM AA. 
1) His assumption that the female is heterozygous for the male sex has no morpho- 
logical Support from the chromosomes, which in these forms are very unfavorable for 
the determination of this important point. 
