1890 PHYSIOLOGICAL SELECTION 219 



that physiological selection was in my opinion the 

 only theory of the origin of species. Everywhere 

 throughout the paper, from the title-page to the con- 

 clusion, I represented it as an 'additional suggestion,' 

 a ' supplementary hypothesis,' &c, &c. Sexual selec- 

 tion is in my view (as it is also in Darwin's, Wallace's, 

 and doubtless that of all evolutionists) one of the 

 '' other theories that have been propounded on the 

 origin of species.' So is Lamarck's theory, which 

 was considered by Darwin as more or less 'supplemen- 

 tary ' to natural selection ; and this is all that I meant 

 — or, I should say, could possibly be understood to 

 mean in view of the title-page, &c. — by speaking of 

 physiological selection as another theory of the origin 

 of species. It certainly is not the same thing as natural 

 selection or either of the ' other theories ' just men- 

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

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

 I myself said, an independent 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 another 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 entire paper ; but, 

 of course, could I have foreseen the interpretations 



