108 MR. DARWIN'S WORK AND 



defining the obligations of an hypothesis, Mr. Darwin, in 

 order to place his views beyond the reach of all possible 

 assault, ought to be able to demonstrate the possibility 

 of developing from 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 

 infertile 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 

 ydu cannot say, ' I can, by selective modification, produce 

 these same results.' Now, it is admitted on all hands that, 

 at present, so far as experiments have gone, it has not 

 been found possible to produce 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 sterility 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 know that there is a single 

 fact which can justify any one in asserting that such 

 sterility cannot be produced by proper experimentation. 

 For my own part, I see every reason to believe that it may, 

 and will be so produced. For, as Mr. Darwin has very 

 properly urged, when we consider the phenomena of 

 sterility, we find they are most capricious; we do not 

 know what it is that the sterility depends on. There are 

 some animals which will not breed in captivity ; whether 



