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presumptive truth, on a narrower one it does not always 

 apply ; for species are differently constituted ab ovo, and 

 will sometimes give a different result from the operation 

 of causes which are identical. Moreover, there is a 

 curious tendency which I have remarked in most islands, 

 that the wings (especially the metathoracic ones) of their 

 insect inhabitants are liable to be retarded in their 

 development, often indeed to such an extent as to 

 become actually evanescent : and I believe it to be a law 

 of Nature, that when any particular organ is either 

 stunted or taken away, the creature receives a compensa- 

 tion for its loss either by the undue enlargement of some 

 other one*, or else in a general increase of its bulk. If 

 such be the case, the presence of two apparently con- 

 flicting effects in a single island is rendered somewhat 

 more intelligible ; nevertheless, on the above hypothesis, 

 the specimens which increase in dimensions should un- 

 doubtedly have their organs of flight more or less en- 

 feebled, whilst those which diminish should be regularly 

 winged. And hence we arrive at the question, is this 

 so ? My own experience would certainly tend to prove 



* Although the result of a primary (or creative) adjustment to 

 special circumstances, rather than of a secondary adaptation, 

 brought about by a self-modifying capability ; we may just call 

 attention to the fact, that most of the blind insects, whether asso- 

 ciates within the nests of ants, or natives of subterranean caverns, 

 have either their palpi or antennae anomalously developed, as 

 though, partially (although how, and in what degree, we cannot 

 possibly ascertain), to make amends for the inconvenience which a 

 total want of sight must necessarily entail. 



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