( Ivi ) 
the aid of entomological observations, is to be met by this 
prevalent cry of non j^ossiimus. 
If we turn to results as a measure of the value of methods, 
it will, I imagine, be conceded that we can show good cause 
in favour of theorising. I may be permitted to draw some illus- 
trations from the Lepidoptera, the only order to which I can 
lay claim to some slight special knowledge, and in which our 
former President is a recognized authority. In the following 
remarks I desire most emphatically to dissociate myself from 
controversial matters, because my sole aim in this addi'ess is 
to clear the atmosphere for the more healthy use of the specu- 
lative faculty by our younger and rising workers. I wish it 
to be understood that in speaking of any particular hypothesis, 
I am not now raising the question of its soundness or un- 
soundness — that is, logically, a distinct issue — but I am 
simply adducing the hypothesis in order to illustrate the 
results of its introduction into modern scientific thought. I 
begin with the phenomena of mimicry and protecti\e resem- 
blance among butterflies and moths as first explained by our 
late distinguished Fellow and past President, Henry Walter 
Bates, in his memorable paper of 1861, which was followed 
by the well-known memoirs of Wallace and Trimen on the 
same subject. It will be remembered by all who are 
familiar with the history of the subject, that this was the 
first application of the theory of natural selection of 
Darwin and Wallace to explain a new set of phenomena. 
It was a speculation evolved by Bates, not when collec- 
ting in the Amazon Valley, as is generally supposed, but 
while looking over his specimens when he had reached 
London, and was pondering, at his own fireside, over the 
meaning of the remarkable superficial resemblances among 
the butterflies of different groups which he had brought 
home.* 
The Batesian theory was fruitful ; it carried with it the 
explanation of the resemblance between insects of distinct 
orders and of the assimilation of insects and other animals 
* I owe this statement to Mr. Bates himself, "who has often made it 
to me. 
