264 THE ORIGIN OF SPECIES 



general sterility of crossed species may safely be looked at, not 

 as a special acquirement or endowment, but as incidental on 

 changes of an unknown nature in their sexual elements. 



HYBRIDS AND MONGRELS COMPARED, INDEPENDENTLY OF 

 THEIR FERTILITY 



Independently of the question of fertility, the offspring of 

 species and of varieties when crossed may be compared in 

 several other respects. Gartner, whose strong wish it was to draw 

 a distinct line between species and varieties, could find very few, 

 and, as it seems to me, quite unimportant differences between 

 the so-called hybrid offspring of species, and the so-called mon- 

 grel offspring of varieties. And, on the other hand, they agree 

 most closely in many important respects. 



I shall here discuss this subject with extreme brevity. The 

 most important distinction is, that in the- first generation mon- 

 grels are more variable than hybrids; but Gartner admits that 

 hybrids from species which have long been cultivated are often 

 variable in the first generation; and I have myself seen striking 

 instances of this fact. Gartner further admits that hybrids be- 

 tween very closely allied species are more variable than those 

 from very distinct species; and this shows that the difference in 

 degree of variability graduates away. When mongrels and the 

 more fertile hybrids are propagated for several generations, an 

 extreme amount of variability in the offspring in both cases is 

 notorious; but some few instances of both hybrids and mongrels 

 long retaining a uniform character could be given. The varia- 

 bility, however, in the successive generations of mongrels is, 

 perhaps, greater than in hybrids. 



This greater variability in mongrels than in hybrids does not 

 seem at all surprising. For the parents of mongrels are varieties, 

 and mostly domestic varieties (very few experiments having been 

 tried on natural varieties), and this implies that there has been 

 recent variability, which would often continue and would aug- 

 ment that arising from the act of crossing. The slight variability 

 of hybrids in the first generation, in contrast with that in the 

 succeeding generations, is a curious fact and deserves attention. 

 For it bears on the view which I have taken of one of the causes 

 of ordinary variability, namely, that the reproductive system, 

 from being eminently sensitive to changed conditions of life, 

 fails under these circumstances to perform its proper function of 

 producing offspring closely similar in all respects to the parent 

 form. Now, hybrids in the first generation are descended from 



