316 THE PRINCIPLES OF Part II. 



cases an inequality would be no advantage or disad- 

 vantage to certain individuals more than to others ; and 

 therefore it could hardly have resulted from natural 

 selection. We must attribute the inequality to the 

 direct action of those unknown conditions, which with 

 mankind lead to the males being born in a somewhat 

 larger excess in certain countries than in others, or 

 which cause the proportion between the sexes to differ 

 slightly in legitimate and illegitimate births. 



Let us now take the case of a species producing from 

 the unknown causes just alluded to, an excess of one 

 sex — we will say of males — these being superfluous and 

 useless, or nearly useless. Could the sexes be equalised 

 through natural selection ? We may feel sure, from all 

 characters being variable, that certain pairs would pro- 

 duce a somewhat less excess of males over females than 

 other pairs. The former, supposing the actual number 

 of the offspring to remain constant, would necessarily 

 produce more females, and would therefore be more pro- 

 ductive. On the doctrine of chances a greater number 

 of the offspring of the more productive pairs would sur- 

 vive ; and these would inherit a tendency to procreate 

 fewer males and more females. Thus a tendency to- 

 wards the equalisation of the sexes would be brought 

 about. But our supposed species would by this process 

 be rendered, as just remarked, more productive ; and 

 this would in many cases be far from an advantage ; 

 for whenever the limit to the numbers which exist, de- 

 pends, not on destruction by enemies, but on the amount 

 of food, increased fertility will lead to severer competi- 

 tion and to most of the survivors being badly fed. In 

 this case, if the sexes were equalised by an increase in 

 the number of the females, a simultaneous decrease in 

 the total number of the offspring would be beneficial ; 

 and this, I believe, could be effected through natural 



