282 
DARWINISM 
CHAT. 
of colour in the male, but rarely a decided difference. The 
female of the great red kangaroo, however, is a delicate gray; 
while in the Lemur macaco of Madagascar the male is jet- 
black and the female brown. In many monkeys also there arc 
some differences of colour, especially on the face. The sexual 
weapons and ornaments of male mammalia, as horns, crests, 
manes, and dewlaps, are Avell known, and are very numerous 
and remarkable. Having thus briefly reviewed the facts, Ave 
Avill uoav consider the theories to which they have given rise. 
Sexual Selection by the Struggles of Males. 
Among the higher animals it is a very general fact that 
the males fight together for the possession of the females. 
'This leads, in polygamous animals especially, to the stronger 
or better armed males becoming the parents of the next 
generation, which inherits the peculiarities of the parents ; 
and thus vigour and offensive Aveapons are continually 
increased in the males, resulting in the strength and horns 
of the bull, the tusks of the boar, the antlers of the stag, 
and the spurs and fighting instinct of the gamecock. But 
almost all male animals fight together, though not specially 
armed; even hares, moles, squirrels, and beavers fight to the 
death, and are often found to be scarred and Avounded. The 
same rule applies to almost all male birds; and these battles 
have been observed in such different groups as humming¬ 
birds, finches, goatsuckers, woodpeckers, ducks, and waders. 
Among reptiles, battles of the males are known to occur in 
the cases of crocodiles, lizards, and tortoises; among fishes, 
in those of salmon and sticklebats. Even among insects the 
same Uiav prevails; and male spiders, beetles of many groups, 
crickets, and butterflies often fight together. 
From this very general phenomenon there necessarily 
results a form of natural selection Avhich increases the vigour 
and fighting power of the male animal, since, in every case, 
the weaker are either killed, wounded, or driven aAvay. This 
selection would be more powerful if males Avere always in 
excess of females, but after much research Mr. Darwin could 
not obtain any satisfactory evidence that this Avas the case. 
The same effect, howe\'er, is produced in some cases by con¬ 
stitution or habits; thus male insects usually emerge first from 
