ME. G. J. EOMAISTES ON PHYSIOLOGICAL SELECTION. 403 



been able to survive under all circumstances where tbey would 

 have otherwise inevitably perished by free intercrossing ? 



Looking to the very general association on which I am dwelling, 

 1 cannot wonder that in the pre-Darwinian days naturalists were 

 led to suppose that the primary distinction of sterility was di- 

 vinely accorded to species, for the purpose of preventing their 

 secondary distinctions from becoming lost by intercrossing. And 

 I cannot help feeling that these naturalists were less blind 

 than their successors ; for at lea^t they had an intelligible theory 

 whereby to explain the general association which we are con- 

 sidering, wh.ereas their successors have absolutely no theory 

 at all. They are, therefore, much in the same position as a 

 man might be who wonders at the constant association between 

 a flowing river and a continuously descending excavation ; for in 

 both cases the association is much too frequent and general to be 

 accounted for by chance, so that, if it is not to be accounted for 

 by design, there only remains the alternative of accounting for 

 it by a connection of casuality. Yet, naturalists are now in the 

 same state of mind as the man above supposed ; they merely 

 wonder at the association without perceiving its obvious import. 

 Por, assuredly, it is quite as obvious that species could not exist 

 as species without the physiological condition of sterility, as it is 

 that a river could not exist as a river without the physical con- 

 dition of declivity. And just as in the latter case, wherever the 

 requisite physical conditions occur, streams and rivers come into 

 existence by way of natural consequence, so in the former case, 

 wherever the requisite physiological conditions occur, species and 

 genera arise as a no less inevitable result. 



It only remains to be said that the theory of physiological 

 selection has this immense advantage over every other theory 

 that has ever been propounded on the origin of species : it admits 

 of being either demonstrated or destroyed by verification. Eut 

 the process of verification will be a most laborious one, and can- 

 not be satisfactorily completed (even if many naturalists should 

 engage upon it) without the expenditure of years of methodical 

 research. In view of this consideration, I have deemed it best 

 to publish my theory before undertaking the labour of verifica- 

 tion ; for, by so doing, I hope to induce other naturalists to co- 

 operate with me in carrying on the research in different parts 

 of the world. With this object, I will conclude by briefly 



