INTERPRETATION AND QUALIFICATION. 505 



cost no more, or have an increased cost less than the in- 

 creased gain. In any case the result is a greater surplus of 

 vital capital, part of which goes to the aggrandizement of 

 the individual, and part to the formation of new individuals. 

 While the higher tide of nutritive matters, everywhere filling 

 the parent-organism, adds to its power of self-maintenance, it 

 also causes a reproductive overflow larger than before. 



Hence every type which is best adapted to its conditions, 

 (and this on the average means every higher type), has a rate 

 of multiplication that insures a tendency to predominate. 

 Survival of the fittest, acting alone, is ever replacing in- 

 ferior species by superior species. But beyond the longer 

 survival, and therefore greater chance of leaving offspring, 

 which superiority gives, we see here another way in which 

 the spread of the superior is insured. Though the more- 

 evolved organism is the less fertile absolutely, it is the more 

 fertile relatively. 



