14 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



This struggle for life requires to be well thought over 

 to show its reality. It is an essential of life that food 

 should be provided. Thus the birds that delight us with 

 their song are dependent on a good supply of seeds or 

 insects. Darwin tells us he once dug and cleared a small 

 piece of land, marking all seedlings of weeds as they 

 came up. He found that, out of 357, no less than 295 

 were destroyed, chiefly by insects and slugs. To eat and 

 be eaten seems the ruling function of animal and vegetable 

 life, if not the end of their being, and their construction is 

 in conformity with this law. Plants consume decaying 

 animal and vegetable matter, which would else nourish 

 seeds of disease ; herbivorous animals eat the plants, 

 carnivorous animals prey upon the herbivorous. An 

 individual possessing the best biting machinery is the 

 one most likely to survive, and produce similar offspring ; 

 vermin, parasites, temperature and climate, epidemics, 

 preying animals, and man all play their part in this 

 struggle, frequently causing a whole species to become 

 extinct. On the other hand, if the check upon insect life 

 were too rapid or disproportioned, whole species of plants 

 must become extinct, as they are absolutely dependent 

 for their very existence upon the visits of insects to ensure 

 fertilization. 



Darwin takes an imaginary case of a wolf, an animal 

 depending upon capturing its prey by craft, strength, or 

 fleetness. Suppose, from any cause, that the fleetest 

 prey — deer, for instance — had increased in numbers 

 through any change in the country, or that other prey 

 had decreased in numbers during the season when the 

 wolf was hardest pressed for food. The result would 

 surely be that the fleetest and slimmest wolves would 

 have the best chance of surviving, and so be preserved, or 

 naturally selected, just as are fleetest greyhounds under 



