92 



whereby to account for modifications innumerable^ each 

 of whichj when viewed simply as a difference, indepen- 

 dently of the circumstances producing it, might have 

 been regarded as sufficient to erect a 'species' upon, 

 had the desire for multiplying them overbalanced the 

 love of truth*." 



Such are a few of the circumstances, influences, and 

 conditions, by which the outward aspect of the insect 

 tribes is liable, within definite limits, to be more or less 

 regulated : and it is impossible to view them with an 

 unbiassed mind and not arrive at the conclusion, that 

 physical agents generally have a very decided control 

 over the external contour of these lower creatures. In 

 selecting the examples which we have lately discussed, I 

 have avoided as much as possible those startling in- 

 stances of variation which distant quarters of the globe 

 wiU readUy supply, because there are vast numbers of our 

 naturalists who will not acknowledge the validity of any 

 evidence which would tend to amalgamate, in a broad 

 sense, the species of the Old and New Worlds. I have 

 therefore contented myself with such data as must fall 

 within our common experience, feeling satisfied that if 

 the principle be allowed in the one case, it cannot long 

 be objected to in the other. There are few entomolo- 

 gists who would not recognize, in the abstract, a legiti- 

 mate capacity for adaptation in every insect with which 

 * Insecta Maderensia, p. 11. 



