316 MY LIFE [CHAr. 



by means of muscle-reading, although in his letter to Darwin 

 he had declared that his mental questions had been 

 answered. 



But a cause of difference on a scientific question had since 

 arisen between Romanes and myself which led to complica- 

 cation. In 1886 he read a paper to the Linnean Society, 

 which was printed in their Journal, entitled "Physiological 

 Selection : an additional suggestion on the Origin of Species." 

 This paper put forth what was really a new theory of the 

 origin of infertile races, which was supposed to account 

 for the infertility that so generally occurs between allied 

 species. It was very complex, and led to much discussion, 

 and before leaving for America I had criticized it in the 

 September issue of the Fortnightly Review. Later, I gave 

 what I considered a proof of its entire fallacy in my " Dar- 

 winism" (published in 1889), and many other writers had 

 also given reasons for rejecting it. This rejection of a theory 

 which he evidently thought very highly of seems to have 

 been very unexpected and to have somewhat ruffled his 

 temper, as was very natural, or he would not, I think, have 

 written of me as he did, especially if we consider the letters 

 he had sent me four years previously. In an article in the 

 Nineteenth Century, of May, 1890, he repeats a statement 

 which he had made before in other periodicals in the follow- 

 ing words : — " He presents an alternative theory to explain 

 the same class of facts. Yet this theory is purely and simply, 

 without any modification whatsoever, a restatement of the 

 first principles of physiological selection, as these were origi- 

 nally stated by myself." To this and to a repetition of it in 

 the American magazine, The Monist, of October, I replied in 

 Nature, and I need only say here that the essential parts of 

 my theory were founded partly on facts established by 

 Darwin, and partly on a mathematical demonstration that 

 sterility could be increased by natural selection. This last 

 argument was stated by me in nearly the same form in 

 letters to Darwin in 1868, eighteen years before Romanes 

 set forth his theory of physiological selection (see " More 

 Letters of Charles Darwin," vol. i. pp. 288-297). Further, 



