NATURAL SELECTION 77 



tic animals were permitted to freely mingle, in a state 

 of nature, they would, in a few generations, produce 

 a common form. There is nothing like the agency of 

 man, in nature, to prevent varieties from mingling. 



The only method by which A and B could remain 

 separated while located side by side, would be for 

 them to be rendered cross-sterile in some way. If B 

 were born cross-fertile with A, there is no conceivable 

 method probable, by which, if the reproductive organs 

 of both are perfect, which is necessarily implied in 

 this case, they could ever become cross-sterile. This 

 leads to the most important question, whether B may, 

 by birth, be cross-sterile with its parent A, while the 

 individuals composing B are fertile with each other 

 and also those of A with each other. 



It is admitted by evolutionists that cross-sterility 

 between A and B cannot be accounted for by the the- 

 ory of natural selection, for it could be of no conceiv- 

 able advantage. 



Dr. Romanes cuts the Gordian knot by assuming 

 that B is, by birth, cross-sterile with A, and at the 

 same time he assumes, and must assume, that the 

 sexual organs of both A and B are perfect, so that 

 each can propagate its kind. 



According to this assumption there must be pro- 

 duced in the same locality, and at the same time, 

 enough individuals of B, cross-sterile with A but fer- 

 tile with each other, to propagate B, and, besides, 

 there must be some favorable variation of these indi- 

 viduals that will enable them to survive. 



Besides this, cross-sterility of A with B must be 

 repeated every time a new species B originates, in 

 order to isolate it from the parent form, which, con 

 sidering the hundreds of thousands of known species 

 of living organisms, together with the common as- 

 sumption that all known forms, both living and fossil, 



