106 CONDITIONS AFFECTING THE 



and that is in the reproductive processes. For there 

 is a most singular circumstance in respect to natural 

 species — at least about some of them — and it would be 

 sufficient for the purposes of this argument, if it were 

 true of only one of them, but there is, in fact, a great 

 number of such cases — and that is, that similar as they 

 may appear to be to mere races or breeds, they present 

 a marked peculiarity in the reproductive process. If 

 you breed from the male and female of the same race, 

 you of course have offspring of the like kind, and if 

 you make the offspring breed together, you obtain the 

 same result, and if you breed from these again, you 

 will still have the same kind of offspring ; there is no 

 check. But if you take members of two distinct spe- 

 cies, however similar they may be to each other, and 

 make them breed together, you will find a check, with 

 some modifications and exceptions, however, which I 

 shall speak of presently. If you cross two such species 

 with each other, then, — although you may get offspring 

 in the case of the first cross, yet, if you attempt to breed 

 from the products of that crossing, which are what are 

 called Hybrids — that is, if you couple a male and a 

 female hybrid — then the result is that in ninety-nine 

 cases out of a hundred you will get no offspring at all : 

 there will be no result whatsoever. 



The reason of this is quite obvious in some cases ; 

 the male hybrids, although possessing all the external 

 appearances and characteristics of perfect animals, are 

 physiologically imperfect and deficient in the structural 

 parts of the reproductive elements necessary to gener- 

 ation. It is said to be invariably the case with the 

 male mule, the cross between the Ass and the Mare ; 

 and hence it is, that, although crossing the Horse with 



