Rev. GeorQ^e Henslow on Natural Selection. 



IN Natural Science of July Mr. Henslow makes some statements 

 with regard to variation and Natural Selection which call fo'' 

 critical remark. He says that, though cultivated plants vary indefinitely, 

 and therefore require selection to produce definite modifications, this is 

 not the case in Nature — " Variation in Nature is always in strict adap- 

 tation to the direct action of the environment ; in other words, natural 

 variation is always definite.'" This statement seems to me so extraordinary, 

 and so opposed to well-known facts, that I can only impute it to the use 

 of the terms "vary" and "variation" in two very distinct senses; first, 

 as meaning those individual variations which occur abundantly both 

 in nature and under cultivation ; and, secondly, as meaning those 

 particular variations which alone survive under nature and produce a 

 " variety " or a " species." In this latter sense, of course, " natural 

 variation " is definite; but so, in the same sense, are the variations 

 of cultivated plants. From unstable and indefinite " variations " man 

 and nature alike produce definite " varieties." As one out of the 

 innumerable examples of indefinite variation which might be named 

 are the fifteen different modes of variation observed by Alph. de 

 CandoUe on a single oak tree, while in a great number of common 

 species an equal amount of variability may be observed both in wild 

 and cultivated individuals ; and all these variations are indefinite, in 

 the sense that they do not usually occur in one direction only, from the 

 typical form. A few examples of such variations have been given in 

 my " Darwinism," pp. 76-80. I cannot, therefore, understand either 

 the meaning or the value of the statement — " natural variation is always 

 definite.'''' 



It is not quite clear whether Mr. Henslow admits the agency of 

 Natural Selection at all. He says : " I would ask what facts are 

 producible to prove that Natural Selection acts at all on the main- 

 tenance, if not the origin, of any floral and, indeed, other structures ? " 

 It is, of course, admitted that direct proof of the action of Natural Selec- 

 tion is at present wanting ; but the indirect proofs have been so 

 cogent as to overcome the most violent prejudice and opposition, and 

 to convert a large majority of naturahsts to a belief in its agency. It 

 is, therefore, rather late in the day to deny its existence without 



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