THE PHENOMENA OF ORGANIC NATURE. 141 



a particular stock by selective breeding, two forms, 

 which should either be unable to cross one with 

 another, or whose cross-bred offspring should be infer- 

 tile with one another. 



For, you see, if you have not done that you have not 

 strictly fulfilled all the conditions of the problem ; you 

 have not shown that you can produce, by the cause 

 assumed, all the phenomena which you have in nature. 

 Here are the phenomena of Hybridism staring you in 

 the face, and you cannot say, " I can, by selective 

 modification, produce these same results." ISTow, it is 

 admitted on all hands that, at present, so far as experi- 

 ments have gone, it has not been found possible to pro- 

 duce this complete physiological divergence by selective 

 breeding. I stated this very clearly before, and I now 

 refer to the point, because, if it could be proved, not 

 only that this has not been done, but that it cannot be 

 done ; if it could be demonstrated that it is impossible 

 to breed selectively, from any stock, a form which shall 

 not breed with another, produced from the same stock ; 

 and if we were shown that this must be the necessary 

 and inevitable result of all experiments, I hold that 

 Mr. Darwin's hypothesis would be utterly shattered. 



But has this been done ? or what is really the state 

 of the case ? It is simply that, so far as we have gone 

 yet with our breeding, we have not produced from a 

 common stock two breeds which are not more or less 

 fertile with one another. 



I do not know that there is a single fact which 

 would justify any one in saying that any degree of ster- 

 ility has been observed between breeds absolutely 

 known to have been produced by selective breeding 

 from a common stock. On the other hand, I do not 



