422 LAWS OP MULTIPLICATION. 



having but small self-preservative powers, are rapidly de- 

 stroyed, to be at the same time without reproductive powers 

 proportionately great. The defect of fertility, if extreme, 

 will result in the death of one generation before another has 

 grown up. If less extreme, it will entail a scarcity such 

 that in the next generation sexual congress will be too infre- 

 quent to maintain even the small number which remains ; and 

 the race will dwindle with increasing rapidity. If still less 

 extreme, the consequent degree of sparseness, while not so 

 great as to prevent an adequate number of procreative unions, 

 will be so great as to render special food abundant and 

 special enemies few will thus diminish the destructive 

 forces so much that the self-preservative forces will become 

 relatively great: so great, relatively, that when combined 

 with the small ability to propagate the species, they will 

 suffice to balance the small destructive forces. Suppose, 

 next, a species whose individuals have high powers of self- 

 preservation, while they have powers of multiplication much 

 beyond what is needful. The excess of fertility, if extreme, 

 will cause sudden extinction of the species by starvation. 

 If less extreme, it must produce a permanent increase in 

 the number of the species; and this, followed by intenser 

 competition for food and augmented number of enemies, will 

 involve such an increase of the dangers to individual life, 

 that the great self-preserving powers of the individuals will 

 not be more than sufficient to cope with them. That is to 

 say, if the fertility is relatively too great, then the ability to 

 maintain individual life inevitably becomes smaller, relatively 

 to the requirements; and the inverse proportion is thus 

 established. 



So that when, from comparing the different states of the 

 same species, we go on to compare the states of different 

 species, we see that there is an analogous adjustment ana- 

 logous in the sense that great mortality is associated with 

 great multiplication, and small mortality with small multi- 

 plication. And we see that the unlikeness of the cases con- 



