vm] OF EVOLUTION 85 



in the direction of anticipating the lines in which 

 enquiries on the method of evolution must proceed, 

 having even a prevision of the doctrine of mimicry, 

 long afterwards established by Bates and others. 

 Lyell wrote : 



' In regard to the origination of new species, I am very glad 

 to find that you think it probable that it may be earned on 

 through the intervention of intermediate causes. I left this rather 

 to be inferred, not thinking it worth while to offend a certain class 

 of persons by embodying in words what would only be a specula- 

 tion One can in imagination summon before us a small part 



at least of the circumstances that must be contemplated and 

 foreknown, before it can be decided what powers and qualities a 

 new species must have in order to enable it to endure for a given 

 time, and to play its part in due relation to all other beings 



destined to coexist with it, before it dies out It may be seen 



that unless some slight additional precaution be taken, the species 

 about to be born would at a certain era be reduced to too low a 

 number. There may be a thousand modes of ensuring its 

 duration beyond that time ; one, for example, may be the 

 rendering it more prolific, but this would perhaps make it press 

 too hard upon other species at other times. Now if it be an 

 insect it may be made in one of its transformations to resemble a 

 dead stick, or a leaf, or a lichen, or a stone, so as to be somewhat 

 less easily found by its enemies ; or if this would make it too 

 strong, an occasional variety of the species may have this 

 advantage conferred on it ; or if this would be still too much, 

 one sex of a certain variety. Probably there is scarcely a dash 

 of colour on the wing or body of which the choice would be quite 

 arbitrary, or which might not affect its duration for thousands of 

 years. I have been told that the leaf-like expansions of the 

 abdomen and thighs of a certain Brazilian Mantis turn from 



