THE PHENOMENA OF REVERSION 299 



CHAPTER X 



THE PHENOMENA OF REVERSION IN THEIR RELATION 



TO AMPHIMIXIS 



1. Reversion to Racial Characters in Plant-Hybrids 



By the term reversion, is meant the appearance of characteris- 

 tics which existed in the more remote ancestors, but were absent 

 in the immediate ancestors — i.e., the parents. 



The facts relating to these phenomena are familiar enough, 

 and I shall therefore only refer to as many of them as are nec- 

 essary for the further development of my theory. 



The simplest case of reversion occurs in hybrids. It occa- 

 sionally happens that hybrids which have been fertilised by 

 their own pollen, produce offspring some of which more or less 

 resemble only one of the two ancestral species. In such cases, 

 therefore, a simple reversion to a grandparent takes place. In- 

 stances of this kind certainly occur, though not in all hybrid- 

 plants ; nor are they often met with even in those species in 

 which they do occur. On this point Darwin quotes two contra- 

 dictory statements made by Wichura and Naudin respectively, 

 the former of whom never observed instances of reversion in his 

 specimens of willow-hybrids, while the latter insisted strongly 

 on the frequent occurrence of reversion in the Cuciirbitacece. 

 Darwin thought that this contradiction is explained by Gartner's 

 statement that reversions seldom occur in hybrid-plants raised 

 from wild species, but are of frequent occurrence in those pro- 

 duced from cultivated species. Opinions on this point have 

 since undergone some modification, for Focke states that ' with- 

 out the influence of the pollen of the parent-species, complete 

 reversions to the ancestral form occur practically only in hybrids 

 of closely allied races.' Instances of reversion of this kind do 

 therefore at any rate occur. 



Such cases can easily be explained on the basis of our theory. 

 The germ-mother-cells of the hybrid contain a group of idants 

 derived from the paternal, and another from the maternal an- 



