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president’s address. 
Another hypothesis to account for colour was that suggested 
by Darwin, viz., sexual selection. 
He thought the females selected the most brilliant coloured 
males, and that in this way gay colours and markings had 
become evolved. Considerable doubt has been thrown on 
this hypothesis, and I certainly do not think that the brilliant 
colours of male Butterflies can be altogether accounted for 
by sexual selection, but I was able myself to make an interest- 
ing observation bearing on this point in the New Forest 
last summer. I observed a female of the small heath Blue- 
Butterfly, Lycaena aegon , sitting on the top of a bush of 
heath, and all round her, at various distances, some sitting, 
and some on the wing, were a number of males. She was the 
only female among twenty or thirty specimens, and was 
evidently holding a court, and presumably selecting a mate. 
I think that the veteran naturalist, Alfred Russel Wallace, 
has suggested the most probable way in which the brilliant 
colours of Butterflies have been acquired. He attributes 
them to surplus vitality and growth power in dominant 
species, especially in the males. Of the existence of this 
surplus vitality and growth power there can be no doubt. 
It is seen throughout Nature. Plants produce far more 
seeds than are required for the continuance of the species, 
and if by any chance the usual checks to the increase of any 
plant or animal are removed, as in the case of the Rabbits 
which have been introduced in Australia and New Zealand, 
this surplus growth of vitality makes itself manifest in the 
enormous increase in the species. This surplus vitality 
applies not only to the species as a whole, but also to every 
part of the animal. 
Now in the case of Butterflies, their colours are due to 
modifications of the scales, with which their wings are covered, 
and if there be no reason why the vital force employed in 
the production of colour should be restrained, nature runs 
riot, and produces all the exquisite tints and patterns which 
