46 THE ORIGIN OF SPECIES 



brid oflspriug of species, and the so-called mongrel ofl- 

 spring 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 gen- 

 eration mongrels are more variable than hybrids; but 

 Gartner admits that hybrids from species which have 

 long been cultivated are often variable in the first gen- 

 eration; and I have myself seen striking instances of this 

 fact. Gartner further admits that hybrids between very 

 closely allied species are more variable than those from 

 very distinct species; and this shows that the difference 

 in the 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 variability, how- 

 ever, in the successive generations of mongrels is, per- 

 haps, 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 variabil- 

 ity; namely, that the reproductive system, from being 



