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whicli they are adjusted to the peculiarities of the region 

 in which they obtain^ that they are strictly an esoteric 

 assemblage, inhabiting the actual sites (or nearly so) of 

 their original debut upon this earth. Here, then, we 

 have a sufficient length of time for developments to have 

 taken place; they are all exposed to the self-same 

 agencies from without (for they live principally in com- 

 munion) ; yet, though I have examined careftdly more 

 than a thousand specimens (a large proportion of them 

 beneath the microscope), I have never discovered a 

 single intermediate link which could be regarded as in a 

 transition state between any of the remainder. But 

 how is this ? — Is it possible to account for differences so 

 decided, yet each of such amazing constancy, amongst 

 the several creatures of a central type which have been 

 exposed to identical conditions through, at any rate, 

 generations innumerable? They clearly cannot be ex- 

 plained on the doctrine of transmutation : yet they are 

 no exceptions to the ordinary rule, — occupying an ana- 

 logous position to the members of every other endemic 

 group. 



But I will not occupy more space on the transmuta- 

 tion theory : suffice it to have shown that, in thus con- 

 ceding a legitimate power of self-adaptation, in accord- 

 ance with external circumstances, to the members of the 

 insect world; and in suggesting the inquiry, whether 

 the action of physical influences has been adequately 

 allowed for by entomologists generally (or, in other 

 words, whether the small shades of difference which 



