208 Evolution and Adaptation 
—for instance, the hump on the male zebu cattle of India, 
the tail of fat-tailed rams, the arched outline of the forehead 
in the males of several breeds of sheep, and, lastly, the mane, 
the long hairs on the hind-legs, and the dewlap of the male 
of the Berbura goat.” 
In these cases and in others that Darwin cites, which seem 
clearly to indicate that some of these secondary sexual charac- 
ters are not the result of sexual selection, he concludes, ‘that 
they must be due to simple variability, together with sexually 
limited inheritance. 
“Hence it appears reasonable to extend this same view to 
all analogous cases with animals in a state of nature. Never- 
theless I cannot persuade myself that it generally holds good, 
as in the case of the extraordinary development of hair on 
the throat and fore-legs of the male Ammotragus, or in 
that of the immense beard of the male Pithecia. Such study 
as I have been able to give to nature makes me believe that 
parts or organs which are highly developed, were acquired 
at some period for a special purpose. With those antelopes 
in which the adult male is more strongly colored than the 
female, and with those monkeys in which the hair on the 
face is elegantly arranged and colored in a diversified 
manner, it seems probable that the crests and tufts of hair 
were gained as ornaments ; and this I know is the opinion of 
some naturalists. If this be correct, there can be little doubt 
that they were gained, or at least modified through sexual 
selection; but how far the same view may be extended to 
other mammals is doubtful.” 
The astonishing colors in some of the monkeys cannot 
be passed over without comment. 
“In the beautiful Cercopithecus diana, the head of the 
adult male is of an intense black, whilst that of the female 
is dark gray; in the former the fur between the thighs is of 
an elegant fawn-color, in the latter it is paler. 
“In the Cercopithecus cynosurus and griseoviridis one part 
