PuRNELL. — On the Animal Mind in Organic Evolution. 245 



herds of cattle. The physical structure of each breed has 

 become modified to suit its place in life, and to better 

 adapt it to fulfil what its mental capacity enables it to 

 perform. 



The chief occupations of an aminal are to provide itself 

 with the means of subsistence, sometimes with shelter, to 

 defend itself against the attacks of enemies, and to multiply 

 its kind. Those animals which are gifted with the most in- 

 telligence, whose appetencies and desires are the keenest, are 

 the most likely to succeed in the struggle for existence. Not, 

 indeed, always so. A fatal and wide-spreading disease like 

 the rinderpest may doom millions to death ; it may spare 

 less intelligent animals, possessing bodily peculiarities fitting 

 them to resist the disease, and carry off individuals more in- 

 telligent, but with constitutions prone to the disease ; a great 

 catastrophe of nature, like a flood or volcanic eruption, an 

 extraordinary period of frost or of hot weather, may destroy 

 vast numbers, and neither superior intelligence nor superior 

 strength of body may avail to save the animal's life. Leaving 

 out of account, however, such special causes of mortality, it is 

 plain that the individual animal of any species which is gifted 

 with an active intelligence will be more likely to hold its own 

 than the individual whose mind is sluggish. The cat which dis- 

 composes the household by its thievish propensities would, in 

 the wild state, manage to provide itself with an excellent 

 living where the well-behaved tabby would starve. The bird 

 of any species which best conceals its nest from the enemies 

 which prey on its eggs and young, and most carefully nurtures 

 its young, will be more likely to leave progeny surviving it 

 than another bird of the same species whose less active intelli- 

 gence make it less successful in the performance of these 

 parental offices. 



It is to the varying mental characteristics of animals that 

 the dispersal of animal races and the multiplication of species 

 is largely due. Professor Karl Semper has shown how cer- 

 tain species of crustaceans can be transmuted into one another 

 according to the saltness of the water in which they live. He 

 proved by experiment that a small crustacean named Artemia 

 milhausenii, which lives in salt - water, can be transformed 

 into an apparently entirely different crustacean called Branchi- 

 pus stagnalis, which inhabits fresh water, the two animals 

 being so different in outward aspect that naturalists had 

 classed them as belonging to different genera. Now, in nature 

 either Artemia milhausenii must have migrated from fresh 

 water to salt, or Branchipus stagnalis from salt water to fresh, 

 and in either case it must have been impelled by its own 

 mental desires to seek the change of habitat which has pro- 

 duced so marked an effect upon its bodily structure. There 



