84 CONTROLLED NATURAL SELECTION 
The occurrence of only a single variation is 
necessary for this conception. Because females 
who happen to choose the most conspicuous 
males, will be more liable to escape destruc- 
tion than females who happen to be mated 
with less conspicuous males: and the former 
females will therefore be more likely to hand 
on this male character than the latter females. 
This applies to all the purposely conspicuous 
characters of males. 
Stolzmann in 1885 put forward a theory to 
account for the secondary sexual characters 
of birds, which in some respects resembles 
this theory. 
Having observed that males are often more 
numerous than females, he justly concluded 
that the species’ food supply was being wasted 
on them and that this excess of males was 
harmful to the species; more especially be- 
cause he believed that the paired females 
during the breeding season were harried by 
celibate males, with injurious results. He 
therefore conceived that the brilliant colours 
of the males arose in order that they might 
easily be seen by enemies and their ranks 
thus thinned. 
This theory was very short-lived, because 
it was speedily pointed out, that if males 
