HYBRIDISM 245 



(very few experiments having been tried on natural 

 varieties), and this implies in most cases that there has 

 been recent variability ; and therefore we might expect 

 that such variability would often continue and be super- 

 added to that arising from the mere act of crossing. 

 The slight degree of variability in hybrids from the 

 first cross or in the first generation, in contrast with 

 their extreme variability in the succeeding generations, 

 is a curious fact and deserves attention. For it bears 

 on and corroborates the view which I have taken on 

 the cause of ordinary variability ; namely, that it is due 

 to the reproductive system being eminently sensitive 

 to any change in the conditions of life, being thus 

 often rendered either impotent or at least incapable 

 of its proper function of producing offspring identical 

 with the parent-form. Now hybrids in the first genera- 

 tion are descended from species (excluding those long 

 cultivated) which have not had their reproductive 

 systems in any way affected, and they are not variable ; 

 but hybrids themselves have their reproductive systems 

 seriously affected, and their descendants are highly 

 variable. 



But to return to our comparison of mongrels and 

 hybrids : Gartner states that mongrels are more liable 

 than hybrids to revert to either parent-form ; but this, 

 if it be true, is certainly only a difference in degree. 

 Gartner further insists that when any two species, 

 although most closely allied to each other, are crossed 

 with a third species, the hybrids are widely different 

 from each other ; whereas if two very distinct varieties 

 of one species are crossed with another species, the 

 hybrids do not differ much. But this conclusion, as 

 far as I can make out, is founded on a single experi- 

 ment ; and seems directly opposed to the results of 

 several experiments made by Kolreuter. 



These alone are the unimportant differences, which 

 Gartner is able to point out, between hybrid and 

 mongrel plants. On the other hand, the resemblance 

 in mongrels and in hybrids to their respective parents, 

 more especially in hybrids produced from nearly related 



