SELECTION 157 



ever and wherever opportunity offers, at the 

 improvement of each organic being in relation 

 to its animate and inanimate conditions of 

 life. It may operate on characters which 

 we are apt to consider of very trifling im- 

 portance, and its accumulation of small 

 variations may set up unexpected correlative 

 changes. It may affect the egg, the seed, or 

 the young as easily as the adult; it may adapt 

 the structure of young to parent and of 

 parent to young; and in social animals it may 

 adapt the structure of each for the benefit 

 of all. In the later editions of the "Origin" 

 a brief account of sexual selection is given 

 at this point. 



The theory of natural selection is then 

 illustrated by particular instances. Thus 

 Darwin pictures the formation of swift 

 varieties of wolves, much in the same way 

 as greyhounds have been evolved by man. 

 Or, again, he refers to the secretion of 

 nectar by flowers, its use to insects, the 

 action of these in carrying the fertilizing 

 pollen, its advantage in intercrossing, and the 

 resultant finely adjusted adaptation of flower 

 and insect to each other through the pres- 

 ervation of their respective advantageous 

 variations. 



Circumstances favourable for the pro- 

 duction of new forms through natural selec- 



