PROOFS OF EVOLUTION . 
17 
lost them by disuse. The wonderful development 
of the gymnast and athlete is achieved by intensi¬ 
fied use of the muscular system. If use or disuse 
is continued from generation to generation, hered¬ 
ity will transmit the result. 
Natural Selection, or Survival of the Fittest, 
grows out of the struggle for self-preservation. 
It is based on the law of hunger. It develops 
strength, cunning, or agility. It is an enemy to 
the weak and poorly conditioned. We see this 
principle exemplified every day in the struggle 
for supremacy among individuals, communities, 
nations, and races. The strongest and best- 
favored survive; the weakest perish. 
Sexual Selection is not concerned with hunger, 
but with beauty and the desire for offspring. As 
well stated by Prof. LeConte, “In Natural Selection 
there is a struggle of all for food, or means of 
living. In Sexual Selection there is a struggle 
among the males for the possession of the females 
and the means of procreation. The one is related 
to the nutritive appetite, the other, to the sexual 
appetite.” 
In animal life, Natural Selection most obtains 
among mammals; sexual selection is more pre- 
