io6 Not Fortuitous in Origin. 



familiar the doctrine of &quot;spontaneous variations 

 of instinct ; that is, of variations produced by the 

 same unknown causes which produce slight devi 

 ations of bodily structure.&quot; But these causes, as 

 he has already told us, are innate to the organ 

 ism ; they are grounded in the very constitution of 

 the being that varies. Were they not, they could 

 not be inherited. An action purely accidental 

 ungrounded, that is, in the nature of the being 

 that performs it would not, on the doctrine of 

 chances, even be repeated by that individual, 

 much less transmitted to its descendants. What 

 is there to transmit in such a fortuitous perform 

 ance ? By the very definition of it, it stands un 

 related to everything else, and exhausts itself in 

 the doing. If the strange habit of the European 

 cuckoo was formed in the way indicated by Dar 

 win, it is only because a predisposition to that 

 mode of action lay dormant in the constitution. 

 &quot; When species vary,&quot; says the eminent botanist 

 !Naudin, whom Darwin frequently quotes, &quot; they 

 do so in virtue of an intrinsic and innate prop 

 erty.&quot; Mere chance variations could never get 

 repeated and perpetuated. And this, indeed, is 

 implied in a sentence with which Darwin con 

 firms the report of the occasional aberrant habit 

 of the American cuckoo. &quot; I could also,&quot; he says, 



