26o DARWINISM AND THE PROBLEMS OF LIFE 



the favourable variation, as the new character will then 

 predominate in the surviving two-thirds and be continu- 

 ously incorporated by amphimixis in the animals that 

 do not possess it, but survive, because the destruction 

 of the species is not great enough to involve them. 

 Thus amphimixis conveys a favourable variation to 

 animals that did not possess it. It quickly generalises 

 useful varieties, and the modification of the species 

 proceeds more rapidly than it could do without am- 

 phimixis. But it is clearly of great importance for a 

 useful variation to spread quickly to a large number of 

 animals, because of the great dangers that the animals 

 encounter from other sides against which the new 

 variation affords no protection. It is also due to 

 crossing that organs which have fallen into disuse 

 slowly disappear in all individuals of the species. 



When we are asked if it is not expecting too much 

 of chance to demand that a variation shall occur in the 

 majority of the survivors, we can answer " No." There 

 are many changes that must be in one of two opposite 

 directions, and in these cases plural variations are quite 

 natural. There are many other variations in which 

 totally different characters may appear plurally, such as 

 the three lengthened parts of the heron we spoke of 

 previously and various shades in the protective colouring 

 of butterflies' wings, if they increase the deception in 

 any way. In the case of many organs the only question 

 is whether they are better or worse, and all variations 

 that fall in the first category are preserved as plural 

 variations. 



In this way a gradual transformation of the species 



