[67]

1877 Oct. 4' Oxalis acetosella— youngish leaf oblique to light— somewhat hidden amongst other leaves— day high clouds

[data not transcribed]

(Used)

[67v]

36 34

Chap. 8

to inherit their superiority. In regard to structures acquired through ordinary or natural selection, and adapted for special ends, there is in most cases, as long as the conditions of life remain the same, a limit to the amount of advantageous modification in relation to some special end; but in regard to structures stat/adapted to make one male victorious over another either in fighting or in charming the female, there is hardly any limit to the amount of advantageous modification; so that as long as fitting variations arise the work of sexual selection will go on. This circumstance may partly account for the frequent and extraordinary amount of variability of presented by secondary sexual characters. Nevertheless, natural selection will determine that no secondary characters shall be acquired by the victorious males, which is injurious to them in any high degree, by expending too much of their vital powers, or exposing them to any great danger.

The development, however, of certain structures—of the horns, for instance, in certain stags,—has been carried to a wonderful extreme; and in some instances, as we shall afterwards hereafter see, to a degree which must be slightly injurious to the male, as far as the his general conditions of life are concerned. From this fact we learn that the advantages which the favoured males have derived from conquering

[68]

Oct 5th Oxalis acetosella Same leaf in same position

[data not transcribed]

(Used)

[68v]

34 32

Chap. 8

attractive females. But this view is not probable from what we know of the eagerness of habit of most animals, for generally the male in general, this view does not seem probable most cases is, eager to pair with any female. It is a more probable view when both sexes are equally possess the same ornaments= al that these ornaments were have been acquired through sexual selection by one sex alone, generally the male sex, but were but, and have then been not only equally transmitted to both sexes. through both sexes, as is always the case, but equally developed in both. If, indeed, during a lengthened period the males of any species had were greatly to exceeded the female in number and then during another lengthened period the reserve had were to occurred, a double but not simultaneous process of sexual selection might easily have been carried on, but not during the same period by which both sexes could ultimately be modified.)

We shall hereafter see that there are many animals with the sexes resembling each other alike which probably have been modified through sexual selection, although they are not brilliantly cl coloured, not provided with any special ornaments. Their absence of bright tints or other ornaments may have be the resulted from of variations of the right kind not never having arisen, or from of the animals themselves having preferred, improbable as it this will at first appear, simple colours, such as plain