306 HYBRIDS AND MONGRELS COMPARED. 



of species, and the so-called mongrel 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 genera- 

 tion mongrels are more variable than hybrids; but Giirtner 

 admits that hybrids from species which have long been cul- 

 tivated are often variable in the first generation; 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 h3'brids 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, however, in the successive gener- 

 ations 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 varie- 

 ties), and this implies that there has been recent variabil- 

 ity, which would often continue and would augment 

 that arising from the act of crossing. The slight 

 variability of hybrids in the first generation, in coatrast 

 with that in the succeeding generations, is a carious 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 

 species (excluding those long cultivated) which have not 

 had their reproductive systems in any way affected, and 

 thev are not variable; but hvbrids themselves have the re- 

 productive 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 



