THE STANDPOINT OF BIOLOGISTS. 25 



kitten-producing life lasts, say, for eight years, and it 

 may, on a low estimate, be supposed to produce a 

 litter of four kittens once in each year. In all a cat 

 will have, on a fair estimate, thirty-two kittens, and 

 may be a great-great-great-great-great-great-grand- 

 mother in her lifetime, yet we do not observe in 

 town or village such an alarming increase in the cats 

 from year to year. Their number is pretty station- 

 ary, kept so by the enormous destruction of their 

 progeny. The enormous capacity for reproduction 

 of# race of animals, where for a time their surround- 

 ings are favourable, will be appreciated by the 

 lowland farmers whose fields were laid waste a few 

 years ago by armies* of short-tailed field-mice, whose 

 natural enemies, the hawks, the cats, and the weasels, 

 had been extensively shot or trapped. 



The struggle to survive among the savage tribes 

 of man must be excessive. Whole races come and 

 go, and their survivors again fall victims to privations, 

 disease, or natural enemies, before the white man 

 with his better brain and capacity for adaptation. 



Selection is a Fact, not a Theory. 



The third idea in the law of natural selection 

 namely, that inborn variations are transmitted is 

 also a fact that is universally admitted not only 

 among biologists at the present day, but by those 



