488 DK. ALFRED E. WALLACE OK 



arises under tte influence of natural selection must, from tlie 

 very nature of its origin, be useful to the new form, no other 

 agency has been shown to exist capable of producing non-utili- 

 tarian characters in every individual constituting a species, neither 

 more nor less. Now the general cause which is adduced as being 

 able to do this is stated by Darwin in the following passages, which 

 are quoted by Mr. E-omanes as expressing his own views : — 



" There must be some efficient cause for each slight individual 

 difference, as well as for more strongly marked variations which 

 occasionally arise ; and if the unknown cause were to act per- 

 sistently, it is almost certain that all the individuals of the species 

 would be similarly modified " (' Origin of Species,' p. 171). 



Again, after referring to cleistogamic flowers and degraded 

 parasitic animals, he says : — 



" We are ignorant of the exciting cause of the above specified 

 modifications ; but if the unknown cause were to act almost 

 uniformly for a length of time, we may infer that the result 

 would be almost uniform ; and in this case all the individuals of the 

 species would be modified in the same manner " (' Origin,' p. 175)*. 



Now these passages, merely as stating a possibility or a prob- 

 ability, appear to me to be wanting both as regards logic and 

 in the absence of any appeal to the actual facts of variation. 

 Por the argument is, briefly, that the same causes will always 

 produce the same or closely similar results. But this is only true 

 when the same causes act upon identical materials and under 

 identical conditions. But the very foundation of the Darwinian 

 theory is, that the materials — the individuals of a species — are 

 not identical, but that they vary indefinitely and in many directions 

 even under closely similar conditions. How then can any external 

 or internal causes produce an identical result — a definite new 

 variation — in all the individuals of a species, born as they are of 

 varying parents, of different ages, and subject to ever fluctuating 

 conditions ? It seems to me, therefore, that the a priori prob- 

 abilities are all against Darwin's supposition. 



Now let us see how far the facts of variation give any support 

 to the theory of useless specific characters. If there is one 

 thing better established than another it is that the individual 

 variations which are constantly occurring in all common species 



* In my 'Darwinism,' p. 141, 1 have stated my opinion that Darwin did not 

 believe in the production of useless characters in all the individuals of a species. 

 I had overlooked the passages quoted by Mr. Eomanes and given above, which 

 certainly show that he did believe it. 



