78 Animal Life and Intelligence. 



diversities of structure might be of use to each being under 

 changing conditions of life. Can it, then, be thought 

 improbable, seeing that variations useful to man have 

 undoubtedly occurred, that other variations, useful in some 

 way to each being in the great and complex battle of life, 

 should occur in the course of many successive generations ? 

 If such do occur, can we doubt (remembering that many 

 more individuals are born than can possibly survive) that 

 individuals having any advantage, however slight, over 

 others, would have the best chance of surviving and of 

 procreating their kind ? On the other hand, we may feel 

 sure that any variation in the least degree injurious would 

 be rigidly destroyed. This preservation of favourable indi- 

 vidual differences and variations, and the destruction of 

 those which are injurious, I have called Natural Selection, 

 or the Survival of the Fittest. Variations neither useful 

 nor injurious would not be affected by natural selection, 

 and would be left either a fluctuating element, or would 

 ultimately become fixed, owing to the nature of the 

 organism and the nature of the conditions." * 



" The principle of selection," says Darwin, elsewhere, 

 " may conveniently be divided into three kinds. Methodical 

 selection is that which guides a man who systematically 

 endeavours to modify a breed according to some pre- 

 determined standard. Unconscious selection is that which 

 follows from men naturally preserving the most valued 

 and destroying the less valued individuals, without any 

 thought of altering the breed. Lastly, we have Natural 

 selection, which implies that the individuals which are best 

 fitted for the complex and in the course of ages changing 

 conditions to which they are exposed, generally survive 

 and procreate their kind." f 



I venture to think that there is a more logical division 

 than this. A man who is dealing with animals or plants 

 under domestication may proceed by one of two well-con- 

 trasted methods. He may either select the most satisfac- 



* " Origin of Species," pp. 62, 63. 



t " Animals and Plants under Domestication," vol. ii. p. 177. 



