by the female having been benefited by possessing a slightly shorter
crest than the male, and its consequent diminution or complete
suppression through natural selection. But I will take a more
favourable case, namely the length of the tail. The long train of the
peacock would have been not only inconvenient but dangerous to the
peahen during the period of incubation and whilst accompanying her
young. Hence there is not the least a priori improbability in the
development of her tail having been checked through natural selection.
But the females of various pheasants, which apparently are exposed on
their open nests to as much danger as the peahen, have tails of
considerable length. The females as well as the males of the Menura
superba have long tails, and they build a domed nest, which is a great
anomaly in so large a bird. Naturalists have wondered how the female
Menura could manage her tail during incubation; but it is now known (8.
Mr. Ramsay, in Proc. Zoolog. Soc. 1868, p. 50.) that she enters the
nest head first, and then turns round with her tail sometimes over her
back, but more often bent round by her side. Thus in time the tail
becomes quite askew, and is a tolerable guide to the length of time the
bird has been sitting. Both sexes of an Australian kingfisher
(Tanysiptera sylvia) have the middle tail-feathers greatly lengthened,
and the female makes her nest in a hole; and as I am informed by Mr.
R.B. Sharpe these feathers become much crumpled during incubation.
In these two latter cases the great length of the tail-feathers must be
in some degree inconvenient to the female; and as in both species the
tail-feathers of the female are somewhat shorter than those of the
male, it might be argued that their full development had been prevented
through natural selection. But if the development of the tail of the
peahen had been checked only when it became inconveniently or
dangerously great, she would have retained a much longer tail than she
actually possesses; for her tail is not nearly so long, relatively to
the size of her body, as that of many female pheasants, nor longer than
that of the female turkey. It must also be borne in mind that, in
accordance with this view, as soon as the tail of the peahen became
dangerously long, and its development was consequently checked, she
would have continually reacted on her male progeny, and thus have
prevented the peacock from acquiring his present magnificent train. We
may therefore infer that the length of the tail in the peacock and its
shortness in the peahen are the result of the requisite variations in
the male having been from the first transmitted to the male offspring
473