266 THE EVOLUTION OF SEX. 



Hence every type that is best adapted to its conditions — every higher 

 type — has a rate of multiplication that insures a tendency to predominate. For 

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

 fertile relatively. 



The whole generalization admits of the simplest graphic illustra- 

 tion. For if the line AB represents the aggregate matter or energies. 



C 



A ! B 



the structures or the functions, of the organism, of which AC denotes 

 the amount devoted to individuation and CB to reproduction, the 

 inverse variation of AC to CB is obvious, as also if AC and CB 

 represent the psychological obverse of these two classes of function. 

 Nor does an increase in total energy modify this, as when the stronger 

 members of a species frequently also exhibit greater reproductive 

 power; for if in one case AB = 20, of which CB = 4, and in another 

 AB = 25, CB may become 5 without any rise of reproductive ratio, 

 since / ¥ = 4$. But if the species be evolving, the advance in individ- 

 uation implies a certain economy, of which a share may go to 

 diminish the decrement to genesis, as above explained. 



IV. Spencer's Application of his Results to Man. — In 

 extending this hard-won generalization to the case of man, the con- 

 comitance of all but highest total individuation with all but lowest 

 rate of multiplication (the enormous bulk of the elephant involving a 

 yet greater deduction from genesis) is at once apparent. Comparing 

 different races of nations, or even different social castes or occupa- 

 tions, the same holds good; while the prevalence of high multiplica- 

 tion in races of which the nutrition is in obvious excess over the 

 expenditure is also evident, witness the Boers or French Canadians. 

 Such an apparent difficulty as that of the Irish, in whom rapid multi- 

 plication occurs despise poor food, is accounted for by the relatively 

 low expenditure in obtaining it (since the ' ' law of diminishing return 

 implies its converse for diminishing labor), though, no doubt, also in 

 part by the habit of early marriage, if not by some measure of 

 lowered individuation as well. The main position being established, 

 Spencer proceeds to discuss the question of human population in the 

 future, and insists strongly on the importance of pressure of popula- 

 tion, which he regards as the main incentive to progress alike in past, 

 present, and future. Reviewing the possibilities of progress in bulk, 

 complexity of structure, multiplication and variation of function, he 

 concludes that the more complete moving equilibrium, and more 

 perfect correspondence between organism and environment, which 

 such evolution involves, must take place mainly in the direction of 

 psychical development. Yet this development, while stimulated by 



