78 ORGANIC EVOLUTION CONSIDERED 



as Darwin claims, are as nothing compared to the 

 number of unknown extinct species, would make it 

 necessary to repeat cross-sterility by birth between 

 parent A and offspring B an infinite number of times. 



When we remember that the universal rule seems 

 to be that parent and offspring are cross-fertile, and 

 not cross-sterile, as the theory of evolution absolutely 

 demands, there is no sufficient reason for making the 

 extreme assumption of cross-sterility by birth. All 

 known facts are against this extreme assumption. 

 When we consider that no case of cross-sterility is 

 known between A and B, when the sexual organs 

 of both are perfect, and that the theory of evolution 

 demands an infinite number of such cases, so that they 

 could hardly be regarded as exceptions to the fact of 

 cross-fertility, and when we remember that the infi- 

 nite number of species of animals which have sur- 

 vived to propagate their kind represent only a small 

 fraction of those that were born cross-sterile with the 

 parent form, because only those survived that were 

 born not only cross-sterile, but also with some favor- 

 able variation that would the better enable them to 

 compete for existence — remembering these things, it 

 would seem that the theory of evolution is pushed to 

 the verge of despair in adopting the theory of cross- 

 sterility by birth between parent and offspring. And 

 yet this assumption, which has of late been urged by 

 Dr. Romanes especially, and adopted by others, is 

 regarded as the most plausible way out of the diffi- 

 culty. 



The formation of permanent varieties in a state of 

 nature is infinitely more difficult than under domesti- 

 cation, because in the latter case man separates the 

 forms that he wants to .propagate, and keeps them 

 apart from the parent stock, whereas, in the former 



