1894 NATUEAL SELECTION v. SELF-ADAPTATION 333 



fectly clear up to a certain point, but then suddenly 

 becomes a petitio principii. In other words, so far as 

 your view is critical of natural selection considered 

 as a hypothetical cause of adaptive evolution, I can 

 well believe you have adduced a formidable array of 

 facts. But I fail to follow, when you pass on to the 

 constructive part of your case — or your suggested 

 substitute for natural selection in self-adaptation. 

 For self-adaptation, I understand, consists in results 

 of immediate response to stimuli supplied by environ- 

 m,ent. But, if so, surely the statement that all the 

 adaptive machinery of plant-organisation is due ta 

 self-adaptation is a mere begging of the question 

 against natural selection unless it can he shown how 

 self-adaptation worJcs in each case. Now I do not find 

 any suggestion as to this. And yet this is obviously 

 the essential point ; since, unless it can be shown how 

 self-adaptation works — i.e. that it is a vera causa, 

 and not a mere word serving to re-state the facts of 

 adaptive evolution. We have got no further in the 

 way of explanation than the physician, who said, 

 that the reason why morphia produces sleep is be- 

 cause it possesses a soporific quality. 



Observe, I purposely abstain from considering 

 your criticism of natural selection, which, although 

 perfectly lucid and possibly justifiable, yet certainly 

 does admit of the answer that incipient variations of 

 a fortuitous kind under nature may often be incon- 

 spicuous (while Wallace shows that in animals they 

 are, as a matter of fact, usually considerable). But 

 we need not go into this. The interesting point to 

 all of us must be the constructive part of your work ; 



