1 10 Evolution and Adaptation 



seminated by birds, its existence depends on them, and it may 

 metaphorically be said to struggle with other fruit-bearing 

 plants, in tempting the birds to devour and thus disseminate 

 its seeds. In these several senses, which pass into each other, 

 I use for convenience' sake the general term ' Struggle for 

 Existence.' " 



A number of writers have objected to the general and 

 often vague way in which Darwin makes use of this phrase ; 

 but it does not seem to me that this is a serious objection, 

 provided we are on our guard as to what the outcome will 

 be in each case. In each instance we must consider the 

 question on its own merits, and if it is found convenient to 

 have a sufficiently general and non-committal term, such as the 

 " struggle for existence," to include all cases, I see no serious 

 objection to the use of such an expression, although it is 

 true the outcome has been that it has become a catchword, 

 that is used too often by those who have no knowledge of its 

 contents. 



Were it not that each animal and plant gives birth, on an 

 average, to more than two offspring, the species would soon 

 become exterminated by accidents, etc. We find in some of 

 the lower animals, and in some of the higher plants, that 

 thousands and even millions of eggs are produced by a 

 single individual in the course of its life. A single nematode 

 may lay sixty million eggs, and a tapeworm one thousand 

 million. A starfish may produce about thirty-nine million 

 eggs, a salmon may contain fifteen thousand, and a large shad 

 as many as one hundred thousand. The queen of a termite 

 nest is said to lay eighty thousand eggs a day. 



In the higher vertebrates the number of young is con- 

 siderably less, but since the young stages are passed within 

 the body of the parent, proportionately more of them reach 

 maturity, so that even in man the population may be doubled 

 in twenty-five years, and in the elephant, slowest breeder of 

 all animals, Darwin has calculated that, if it begins breeding 



