172 Darwin, and after Darwin. 



late, Mr. Wallace and his followers will always throw 

 upon us the impossible burden of proving the negative, 

 that these apparently useless characters do not present 

 some hidden or former use, are not due to correlation, 

 and therefore have not been produced by natural selec- 

 tion. It is in vain to retort that the burden of proof 

 really lies the other way, or on the side of those who 

 affirm that there is utility where no man can see 

 it, or that there is correlation where no one can 

 detect it. Thus, so far as any appeal to particular 

 facts is concerned, it does not appear that there is any 

 modus Vivendi. Our opinions upon the question are 

 really determined by the views which we severally 

 take on matters of general principle. The issue, 

 though it has a biological bearing, is a logical issue, 

 not a biological one: it turns exclusively on those 

 questions of definition and deduction with which 

 we have just been dealing. 



But although it thus follows that we cannot 

 determine in fact what proportion of apparently 

 useless characters are or are not really useful, we 

 may very easily determine in fact what proportion 

 of specific characters fail to present any observable 

 evidences of utility. Yet, even upon this question of 

 observable fact, it is surprising to note the diver- 

 gent statements which have of late years been 

 made by competent writers ; statements in fact so 

 divergent that they can only be explained by some 

 want of sufficient thought on the part of those 

 naturalists who are antecedently persuaded that all 

 specific characters must be either directly or in- 

 directly due to natural selection. Hence they fail 

 to give to apparently useless specific characters the 



