The Making of Species 
other characters which arise from the develop- 
ment of these, or are correlated with them” 
(Darwinism, p. 283). But the view that the 
female selects the most beautiful of her suitors 
has always seemed to Wallace ‘to be un- 
supported by evidence, while it is also quite 
inadequate to account for the facts.” For 
example, the accessory plumes of birds “usually 
appear in a few definite parts of the body. We 
require some cause to initiate the development in 
one part rather than in another.” 
Wallace considers that natural selection is 
able to explain all the phenomena of sexual 
dimorphism. He points out that, when the sexes 
are dissimilar among birds, it is almost invariably 
the female which is duller coloured. The reason 
for this is, he believes, that the hen birds, while 
sitting, ‘‘are exposed to observation and attack 
by the numerous devourers of eggs and birds, 
and it is of vital importance that they should be 
protectively coloured in all those parts of the 
body which are exposed during incubation. To 
secure this, all the bright colours and showy’ 
ornaments which decorate the male have not 
been acquired by the female, who often remains 
clothed in the sober hues which were probably 
once common to the whole order to which she 
belongs. The different amounts of colour ac- 
quired by the females have no doubt depended 
on peculiarities of habits and environment, and on 
322 
~ Spite 
