? 



288 



VARIATION OF PLANTS AND ANIMALS. [Ch. XXXVI', 



/' 



■When 



ifl 



greatlj perfected^ he is able to bring about very important 

 changes in a short time. He has no power either of causing 

 or preventing the nmnerons varieties which nature presents 

 to him among individuals born of the same parents. But 

 he can choose those which best suit his purpose^ and breed 

 from them^ while he destroys those varieties which are less 

 valuable. In the next generation he again picks out those 



more marl 



qualit 



degree ; and so goes on 



Mr 



accumulating these 

 differences till he produces a breed which answers to some 

 preconceived idea formed by him. He can discriminate 

 trifling variations both in animals and plants which an unedu- 

 cated eye cannot appreciate. The variations which are thus 

 intensified become fixed by inheritance, and permanent races 

 are formed — a process technically called selection. But there 

 is another kind of selection, termed ' unconscious ^ by 

 Darwin, which perhaps acts more powerfully in the long run, 

 both in a rude and civilised state of society. The savage, 

 when pressed by hunger, is often driven to feed on his dogs ; 

 in which case, if he is able to retain any of them, he preserves 

 such as are most useful to him in the chase. So in a very 

 early state of agriculture, the seeds and fruits of those varie- 

 ties which offer some advantage over others, by the abundance 

 of their produce or the quality or flavour of the nutriment 

 they afford, will be sown by preference, whereas the seeds of 

 less prized varieties will be consumed. For man is always 

 called upon to decide which individuals shall be spared as a 

 stock from which to breed, so many more being always born 

 into the world than there is room or food for. Mr. Darwin 

 supposes that, even in the most advanced state of society, 

 the influence of unconscious selection acts more powerfully 

 than methodical selection. 



Our present bull-dogs, he observes, are different from those 

 formerly used for baiting bulls, being of smaller size and 

 altered in shape, now that the old sport has been given up. 

 Our fox-hounds differ from the old English hound, and our 

 greyhounds have become lighter. Our enormous dray-horses 



I 



