260 HYBRIDS AND MONGRELS COMPARED. [Chap. IS. 



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

 recent variability, which would often continue and would augment 

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

 hybrids in the first generation, in contrast with that in the succeed- 

 ing 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 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: 

 GSrtner states that mongrels are more liable than hybrids to revert 

 to either parent-form ; but this, if it be true, is certainly only a dif- 

 ference in degree. Moreover, Gartner expressly states that hybrids 

 from long cultivated plants are more subject to reversion than 

 hybrids from species in their natural state ; and this probably 

 explains the singular difference in the results arrived at by different 

 observers : thus, Max Wichura doubts whether hybrids ever revert 

 to their parent-forms, and *ie experimented on uncultivated species 

 of willows; whilst Naudin, on the other hand, insists in the strongest 

 terms on the almost universal tendency to reversion in hybrids, 

 and he experimented chiefly on cultivated plants. Gartner further 

 states 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 experiment ; and seems directly opposed to the 

 results of several experiments made by Kolreutcr. 



Such alone are the unimportant differences which Gartner is able 

 to point out between hybrid and mongrel plants. On the other 

 hand, the degrees and kinds of resemblance in mongrels and in 

 hybrids to their respective parents, more especially in hybrids pro- 

 duced from nearly related species, follow according to Gartner the 

 same laws. When two species are crossed, one has sometimes a 

 prepotent power of impressing its likeness on the hybrid. So I 

 believe it to be with varieties of plants; and with animals one 

 variety certainly often has this jrepotent power over another 



