70 PECKHAM. Vol. 1. 



endurance, the strength, the swiftness, and (b) partly by their 

 fertility, it is constantly being maintained. These conflicting 

 sets of actions may be generalized as the forces destructive of 

 race and the forces preservative of race." 



There exists an equilibrium between the destructive and 

 preservative forces of every species. Any excess of either of 

 these sets of forces itself generates, by the deviation it pro- 

 duces, certain counter-forces that eventually out-balance it and 

 initiate an opposite deviation. 



"Is this the sole equilibration that must exist ? Clearly 

 not. The temporary compensating adjustments of multipli- 

 cation to mortality in each species are but introductory to the 

 permanent compensating adjustments of multiplication to 

 mortality among species in general. The above reasoning 

 would hold just as it now does, were all species equally prolific 

 and all equally short-lived. It yields no answer to the 

 inquiries — why do their fertilities differ so enormously, or why 

 do their mortalities differ so enormouslj'? And how is the 

 general fertility adapted to the general mortality in each? 

 The balancing process we have contemplated, can go on only 

 within moderate limits — must fail entirely in the absence of a 

 due proportion between the ordinary birth-rate and the 

 ordinary death-rate ; * * * the minor adjustment of vary- 

 ing multiplication to varying mortality in each species, implies 

 some major adjustment of average multiplication to average 

 mortality. What must this adjustment be? 



"We have already seen that the forces preservative of race 

 are two — ability in each member of the race to preserve itself, 

 and ability to produce other members — power to maintain 

 individual life, and power to generate the species. These must 

 vary inversely. When, from lowness of organization, the 

 ability to contend with external dangers is small, there must be 

 great fertility to compensate for the consequent mortality; 

 otherwise the race must die out. When, on the contrary, high 

 endowments give much capacity of self-preservation, a 

 correspondingly low degree of fertility is requisite. Given the 



