selection. For instance, the relative number of the two sexes, the earlier
emergence of the males, the laws of inheritance, etc. What an admirable
illustration you give of the transference of characters acquired by one
sex--namely, that of the male of Bombus possessing the pollen-collecting
apparatus. Many of your facts about the differences between male and
female bees are surprisingly parallel with those which occur with birds.
The reading your essay has given me great confidence in the efficacy of
sexual selection, and I wanted some encouragement, as extremely few
naturalists in England seem inclined to believe in it. I am, however, glad
to find that Prof. Weismann has some faith in this principle.

The males of Bombus follow one remarkable habit, which I think it would
interest you to investigate this coming summer, and no one could do it
better than you. (462/2. Mr. Darwin's observations on this curious
subject were sent to Hermann Muller, and after his death were translated
and published in Krause's "Gesammelte kleinere Schriften von Charles
Darwin," 1887, page 84. The male bees had certain regular lines of flight
at Down, as from the end of the kitchen garden to the corner of the "sand-
walk," and certain regular "buzzing places" where they stopped on the wing
for a moment or two. Mr. Darwin's children remember vividly the pleasure
of helping in the investigation of this habit.) I have therefore enclosed
a briefly and roughly drawn-up account of this habit. Should you succeed
in making any observations on this subject, and if you would like to use in
any way my MS. you are perfectly welcome. I could, should you hereafter
wish to make any use of the facts, give them in rather fuller detail; but I
think that I have given enough.

I hope that you may long have health, leisure, and inclination to do much
more work as excellent as your recent essay.