1898] THE STUDY OF VARIATIONS : A REJOINDER 395 



Romanes regarded indiscriminate variations as essential to the theory 

 of Natural Selection. Had Romanes and other biologists thoiight 

 otherwise, it would have been unnecessary to raise this point, and it 

 was only because I had not seen my position taken up elsewhere 

 that I put it forward. 



Professor Henslow may be told by many that his books do 

 prove that variations are definite, but, unfortunately, for the present 

 state of the question there are at least an equal number who think 

 otherwise. But were all biologists unanimous on this point my 

 position would be unaffected, since it maintains tliat definite varia- 

 tions can be easily accounted for by Natural Selection alone. The 

 fact that Darwin and Wallace were both unaware of this, does not 

 invalidate the theory in the slightest degree, since they could not 

 possibly be expected to have foreseen every development of their 

 views. Mr Henslow finds my theory on this subject to be ' offered 

 without a particle of fact ' to support it ; but no fact is here needed, 

 the position being that a theory is offered in support of Natural 

 Selection, leading naturally from indefinite to definite variations in 

 the course of evolution. It is not a question of facts, as at present 

 collected ; it is simply a question of two competing theories, which 

 would both explain the definite variations in nature, if tliey exist. 

 It will therefore be only from a careful restudy of variations that 

 we can hope for a more settled ^iew of this question. 



The difficulty that Professor Henslow finds in this to me obvious 

 deduction astonishes me ; I can see nothing complicated in the 

 assumption that Natural Selection, as it necessarily must eliminate 

 the unfit, will as necessarily leave behind to grow and reproduce 

 with each other the more or less fit ; and that with each succeeding 

 generation the variations must tend to become increasingly fit, and, 

 consequently, more or less definitely adaptive. Indeed it seems to 

 me to be a much greater assumption to say that variations are 

 adaptive on the present data, since a biologist's knowledge would 

 be great indeed if, even on any given single variety, he were able to 

 prove all its variations useful, and much more so were he able to 

 establish the same result with reference to species. 



Lastly, I am asked to give half-a-dozen examples of plants and 

 animals living in a wild state, which I can place within the first 

 three groups of my classification of variations. As the whole object 

 of my paper is to point out that no instance can be adduced by any 

 biologist which will be accepted by others holding opposite views, it 

 seems a little extraordinary that I should be expected to give six 

 instances, or even three or one, when I believe none are to be found 

 in the present state of our knowledge on this question. 



Weismann, in The Contemporary Review for September 1895, 

 states this difficulty very clearly : " An essay by Herbert Spencer is 



