TRACHEATES 227 



ought to preserve rather than injure the wings, since 

 dead structures are all the better for being spared, as 

 anyone can see in the matter of his clothes. Hence, 

 the wings ought to have been used up and atrophied 

 precisely in the case of the flying insects, and have been 

 preserved in the case of the non-flying, such as the orgyia. 

 There are many rudimentary organs in the coat of 

 insects. To these the Lamarckian principle is inappli- 

 cable, and so once more we must discard it as unsafe and 

 only explaining a part of the instances. 



To conclude ; no case has ever been known of the 

 inheritance of the effects of use and disuse, and so the 

 Lamarckian principle has not a single established fact 

 to support it. Its possible sphere of action is very 

 limited ; even amongst a given class of phenomena it 

 has always to leave inexplicable gaps. There is an 

 enormous number of instances to which it has no 

 application. Of the two postulates on which it is based, 

 the first is only certain in a few cases, and at the most 

 merely possible in the majority. The second postulate 

 is not an established fact, but a pure theory ; a theory, 

 moreover, that is difficult to imagine, and in its turn 

 postulates all sorts of phenomena and relations of most 

 of which nothing is known. Finally, the Lamarckian 

 principle is an obstacle in the way of a unified conception 

 of things, such as it is the chief aim of the theory of 

 evolution to build up, and can never be reconciled with 

 it. We shall see more of this in the eleventh chapter. 



But I think we have now said enough to deprive the 

 Lamarckian principle of all power to modify the forms of 

 the organic world. 



