364 Darwin, and after Darwin. 



will subsequently endeavour to prove, there is abun- 

 dant evidence to show that incipient characters are 

 often developed to a large extent by causes other 

 than natural selection (or apart from any reference to 

 utility), with the result that some of them thus happen 

 to become of use, when, of course, the supposed diffi- 

 culty is at an end. 



But although it is thus easy to dispose of both the 

 propositions in question, on account of their univer- 

 sality, stated more carefully they would require, as 

 I have said, more careful consideration. Thus, if it 

 had been said that some incipient organs are presum- 

 ably useless at the time of their inception, and that in 

 some of these cases it is difficult, or impossible, to con- 

 ceive how the principle of correlation, or any other 

 principle hitherto suggested, can apply then the 

 question would have been raised from the sphere of 

 logical discussion to that of biological fact. And 

 the new question thus raised would have to be de- 

 bated, no longer on the ground of general or abstract 

 principles, but on that of special or concrete cases. 

 Now until within the last year or two it has not been 

 easy to find such a special or concrete case that is to 

 say, a case which can be pointed to as apparently 

 excluding the possibility of natural selection having 

 had anything to do with the genesis of an unquestion- 

 ably adaptive structure. But eventually such a case 

 has arisen, and the Duke of Argyll has not been slow 

 in perceiving its importance. This case is the electric 

 organ in the tail of the skate. No sooner had Pro- 

 fessor Cossar Ewart publibhed an abstract of his first 

 paper on this subject, than the Duke seized upon it as 

 a case for which, as he said, he had long been waiting 



