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presumptive truth, on a narrower one it does not always 

 apply ; for species are differently constituted ab ovo, and 

 wiR 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 ret arded in their 

 development, — often indeed to such an extent as to 

 become actually evanescent : and I behave 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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