FACTORS IN ANIMAL LIFE 



Romanes found that rats would get certain semi- 

 liquid foods out of a bottle with their tails, as a cat 

 will get milk out of a jar with her paw, but neither 

 ever progresses so far as to use any sort of tool 

 for the purpose, or to tip the vessel over. Animals 

 practice concealment to secure their prey, but not 

 deception, as man does. They do not use lures or 

 disguises, or traps or poison. 



There is, of course, no limit to the variety and 

 adaptiveness of nature taken as a whole, but each 

 species is hedged about by impassable limitations. 

 The ouzel is akin to the thrushes, and yet it lives 

 along and in the water. Does it ever take to the 

 fields and woods, and live on fruit and land-insects, 

 and nest in trees like other thrushes ? So with all 

 birds and beasts. They vary constantly, but not in 

 one lifetime, and the sum of these variations, accu- 

 mulated through natural selection, as Darwin has 

 shown, gives rise, in the course of long periods of 

 time, to new species. 



As I have already said, domestic animals vary 

 more than wild ones. Every farmer and poultry- 

 grower knows that some hens are better with chick- 

 ens than others — more motherly, more careful — 

 and rear a greater number of their brood. The same 

 is true of sows with pigs. Some sows will eat their 

 pigs, and wild animals in cages often destroy their 

 young. Some ewes will not own their lambs, and 

 occasionally a cow will not own her calf. (Such cases 

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