1890 PHYSIOLOGICAL SELECTION 215 



tioned ; but no less certainly it is not exclusive of any 

 of the tkree. Unquestionably it is as you say, and as 

 I myself said, an indepeyident theory — i.e. not iden- 

 tical with, but additional to, that of natural selection. 

 But this is a widely different thing from saying that 

 it is in itself an exhaustive theory, which must there- 

 fore swallow up all or any ' others.' In short, I abide 

 by the closing statement of my introductory para- 

 graph — viz. that the theory is an ' attempt at sug- 

 gesting anotlier factor in the formation of species, 

 which, although quite independent of natural selection, 

 is in no way opposed to natural selection, and may 

 therefore be regarded as a factor supplementary to 

 natural selection.' Statements to the same effect 

 are indeed scattered through the entu-e paper ; but, 

 of course, could I have foreseen the interpretations 

 which afterwards arose, I should have reiterated such 

 statements ad nauseam. 



Sorry you cannot come to the B.A., or to dine, 

 but certainly do not wonder. 



Yours rery sincerely, 

 ' G. J. Romanes. 



Lastly, about species not being able to exist as 

 species without the physiological isolation of physio- 

 logical selection (p. 403), the statement of course only 

 apphes to nearly allied species occupying common 

 areas (see p. 404). If this statement is wrong, no 

 one has yet shown me wherein it is so. I fancy you 

 do not quite appreciate that by ' sterihty ' I always 

 mean (unless otherwise expressly stated) sterihty in 

 some degree, and this not only with regard to the 



