' 
MIMICRY IN CEYLON BUTTERILIES. 19 
We are now in a position to work out the results of the various 
possible matings between these different individuals. 
(1) 6 x ¢ @—Since both the male and ¢ g are in every 
case homozygous for the factor A such matings can only 
give gg and 99 of the male type. , 
(2) 6 xX °g @-—Since there are three possible kinds of male 
differing in constitution, though not necessarily in 
appearance, and since 9 @ may also be either homo- 
zygous or heterozygous for B, it follows that there are 
six possible types of mating between these two forms, 
viz. :— 
(i.) 66 AA BB Xx ¢¢ Aa BB j 
(.) 66 AA Bb x 96 Aa BB... 
(ui.) 6 AAbb xX 9g Aa BB , giving gg and 99 6 only. 
(iv.) gg AA BB x 9g Aa Bb | 
(v.) gg AA Bb xX 96 Aa BD, giving 66, 22 @ (75 per cent.). 
and 99 y (25 per cent.). 
(vi.) 6 AAbb x 96 Aa BD, giving 6g, 92 @ (59 per cent.) 
and ¢? y (50 per cent.). 
. 
(3) 6 x 2 y.—Since ¥ y is on our hypothesis always of the 
same constitution, it follows that the only three possible 
matings here are :— 
(i.) 66 AA BB x 96 Aa bb, giving éé and £% @ only. 
Gi. ) 6 AABL x 96 Aa db, giving 6, 99 6 (50 per cent.), and 
22 ¥ (50 per cent.). 
(iii.) gg AAbb x 96 Aa bb, giving éé and 2 y only. 
The experimental test of the correctness of such a scheme would 
lie in substantiating the following propositions :— 
(1) The form of female which is like the male in pattern breeds 
true, and does not throw either of the other two forms of 
female. 
(2) Neither of the other two forms of female can give the female 
of the male pattern.* 

* Should this be confirmed by experimental evidence, it would offer a simple 
explanation of the complete disappearance of the ‘‘ male form” of female 
which seems to have taken place in most polymorphic species. Thus the 
Malayan Papilio theseus and P. ambraz, near allies of P. polytes, have only 
the ‘‘ aristolochie form” of female, a condition which could rapidly come 
about on the above scheme if the ‘‘ aristolochis form” were already in 
existence and received some slight advantage over the normal form through 
the operation of natural selection. For if neither female could throw the other, 
even a small advantage possessed by the one would lead rapidly to the other’s 
elimination. On this view cases of sexual dimorphism in the colour patterns 
of Lepidoptera are cases of advanced polymorphism in which one form of female, 
viz., that like the male, has been eliminated, either in the history of the 
species itself or of its precursors. 
