114 A PRIMER OF BIOLOGY 



have given rise to 100 millions of millions of carrion 

 flies! 



These figures are sufficiently startling when they 

 are put down in black and white, but another 

 and equally startling fact meets us at once when 

 we study the subject more closely, namely, that 

 this prodigious rate of increase is never main- 

 tained. It is perfectly obvious to every one that 

 one plant in an incredibly short space of time would 

 soon cover the globe to the exclusion of everything 

 else. If every pair of birds produced in a few years 

 10,000,000 of birds, the sky would be dark with 

 their wings. There must therefore be an enormous 

 destruction of individuals, especially in the early 

 stages of life, by various injurious agencies. Extreme 

 cold or heat, damp, drought, disease, enemies, all 

 play a part, and the net result is that, despite these 

 enormous powers of increase, the number of individuals 

 of each type, living from year to year, remains fairly 

 constant. 



Nothing, perhaps, brings this destruction of life 

 more vividly home to us than to consider how many 

 organisms, in the adult or in the embryonic condi- 

 tion, are destroyed in order that an average dinner 

 may be provided for one human being (Arthur : " The 

 Right to Live," 1897). Suppose that the dinner 

 consists of tomato soup, fish, roast beef with potatoes 

 and cauliflower, chicken, a rice pudding, together 

 with the usual accompaniments of bread, cheese, 

 and, say, a glass of wine. To produce the plate of 

 tomato soup at least two tomatoes will be required, 

 representing at least 200 possible seedlings. Then 

 there will be one fish, one ox, one chicken, say 

 three potatoes, representing the possibility of at 

 least twelve plants, and one cauliflower. The bread 



