beautifully coloured, and I can as yet hardly think that the colouring in
such cases is protective.


LETTER 461. TO AUG. WEISMANN.
Down, February 29th, 1872.

I am rejoiced to hear that your eyesight is somewhat better; but I fear
that work with the microscope is still out of your power. I have often
thought with sincere sympathy how much you must have suffered from your
grand line of embryological research having been stopped. It was very good
of you to use your eyes in writing to me. I have just received your essay
(461/1. "Ueber der Einfluss der Isolirung auf die Artbildung": Leipzig,
1872.); but as I am now staying in London for the sake of rest, and as
German is at all times very difficult to me, I shall not be able to read
your essay for some little time. I am, however, very curious to learn what
you have to say on isolation and on periods of variation. I thought much
about isolation when I wrote in Chapter IV. on the circumstances favourable
to Natural Selection. No doubt there remains an immense deal of work to do
on "Artbildung." I have only opened a path for others to enter, and in the
course of time to make a broad and clear high-road. I am especially glad
that you are turning your attention to sexual selection. I have in this
country hardly found any naturalists who agree with me on this subject,
even to a moderate extent. They think it absurd that a female bird should
be able to appreciate the splendid plumage of the male; but it would take
much to persuade me that the peacock does not spread his gorgeous tail in
the presence of the female in order to fascinate or excite her. The case,
no doubt, is much more difficult with insects. I fear that you will find
it difficult to experiment on diurnal lepidoptera in confinement, for I
have never heard of any of these breeding in this state. (461/2. We are