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 i 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 c 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 110 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 



