The Theory of Sexual Selection. 393 
one, unless, as Wallace supposes, there is some cor- 
relation between embellishment and general perfection, 
in which case, as he points out, the theory of sexual 
selection lapses altogether, and becomes but a special 
case of natural selection. 
Once more, Mr. Wallace argues that the evidence 
collected by Mr. Darwin himself proves that each bird 
finds a mate under any circumstances—a general fact 
which in itself must quite neutralize any effect of 
sexual selection of colour or ornament, since the less 
highly coloured birds would be at no disadvantage as 
regards the leaving of healthy progeny. 
Lastly, he urges the high improbability that through 
thousands of generations all the females of any par- 
ticular species—possibly spread over an enormous 
area—should uniformly and always have displayed 
exactly the same taste with respect to every detail of 
colour to be presented by the males. 
Now, without any question, we have here a most 
powerful array of objections against the theory of 
sexual selection. Each of them is ably developed by 
Mr. Wallace himself in his work on Zropical Nature ; 
and although I have here space only to state them in 
the most abbreviated of possible forms, I think it will 
be apparent how formidable these objections appear. 
Unfortunately the work in which they are mainly pre- 
sented was published several years after the second 
edition of the Descent of Man, so that Mr. Darwin 
never had a suitable opportunity of replying. But, if 
he had had such an opportun‘ty, as far as I can judge 
it seems that his reply would have been more or less 
as follows. 
In the first place, Mr. Wallace fails to distinguish 
