Opinions on Isolation. 137 



words have no meaning "; that " if this is 'the whole 

 essence of physiological selection,' then physiological 

 selection is but a re-statement and amplification of 

 Darwin's views "; that such a " change of front " is 

 incompatible, not only with my term " physiological 

 selection," but also with my having " acknowledged 

 that Mr. Catchpool had ' very clearly put forward the 

 theory of physiological selection'"; and much more 

 to the same effect. 



Now, to begin with, it is due to Mr. Catchpool to 

 state that his only publication upon this subject is 

 much too brief to justify Mr. Wallace's inference, that 

 he supposes variations in the way of cross-infertility 

 always to arise " alone in an otherwise undifferentiated 

 species." What Mr. Catchpool's opinion on this 

 point may be, I have no knowledge ; but, whatever it 

 is, he was unquestionably the first writer who "clearly 

 stated the leading principles" of physiological selec- 

 tion, and this fact I am very glad to have " acknow- 

 ledged." In my correspondence with Mr. Wallace, 

 however, I not only named Mr. Catchpool: I also 

 named and much more prominently Mr. Gulick. 

 For even if I were to grant (which I am far indeed 

 from doing) that there was any want of clearness in 

 my own paper touching the point in question, I have 

 now repeatedly shown that it is simply impossible 

 for any reader of Mr. Gulick's papers to misunder- 

 stand his views with regard to it. Accordingly, 

 I replied to Mr. Wallace in Nature by saying: 



Not only have I thus from the first fully recognized the 

 sundry other causes of specific change with which the physio- 

 logical variations may be associated ; but Mr. Gulick has gone 

 into this side of our common theory much more fully, and 



