Chap. YIII. 
SEXUAL SELECTION. 
257 
of life, and the male has more highly developed sense 
or locomotive organs than the female, it may be that 
these in their perfected state are indispensable to the 
male for finding the female ; but in the vast majority 
of cases, they serve only to give one male an advan- 
tage over another, for the less well-endowed males, 
if time were allowed them, would succeed in pair- 
ing with the females ; and they would in all other 
respects, judging from the structure of the female, be 
equally well adapted for their ordinary habits of life. 
In such cases sexual selection must have come into 
action, for the males have acquired their present struc- 
ture, not from being better fitted to survive in the 
struggle for existence, but from having gained an ad- 
vantage over other males, and from having transmitted 
this advantage to their male offspring alone. It was the 
importance of this distinction which led me to designate 
this form of selection as sexual selection. So again, 
if the chief service rendered to the male by his pre- 
hensile organs is to prevent the escape of the female 
before the arrival of other males, or when assaulted by 
them, these organs will have been perfected through 
sexual selection, that is by the advantage acquired by 
certain males over their rivals. But in most cases it 
is scarcely possible to distinguish between the effects 
of natural and sexual selection. Whole chapters could 
easily be filled with details on the differences between 
the sexes in their sensory, locomotive, and prehensile 
organs. As, however, these structures are not more 
interesting than others adapted for the ordinary pur- 
poses of life, I shall almost pass them over, giving only 
a few instances under each class. 
There are many other structures and instincts which 
must have been developed through sexual selection — 
such as the weapons of offence and the means of defence 
VOL. I. s 
