I will write to Mr. H. in a few days,
and ask him whether he has observed anything of this kind with pure
unions of fowls, ducks, etc. I had utterly forgotten the case of the
ruff (437/2. The ruff, Machetes pugnax, was believed by Montague to be
polygamous. "Descent of Man," Edition I., Volume I., page 270.), but now
I remember having heard that it was polygamous; but polygamy with birds,
at least, does not seem common enough to have played an important part.
So little is known of habits of foreign birds: Wallace does not even
know whether Birds of Paradise are polygamous. Have you been a large
collector of caterpillars? I believe so. I inferred from a letter from
Dr. Wallace, of Colchester, that he would account for Mr. Stainton
and others rearing more female than male by their having collected the
larger and finer caterpillars. But I misunderstood him, and he maintains
that collectors take all caterpillars, large and small, for that they
collect the caterpillars alone of the rarer moths or butterflies. What
think you? I hear from Professor Canestrini (437/3. See "Descent of Man"
(1901), page 385.) in Italy that females are born in considerable excess
with Bombyx mori, and in greater excess of late years than formerly!
Quatrefages writes to me that he believes they are equal in France.
So that the farther I go the deeper I sink into the mire. With cordial
thanks for your most valuable letters.

We remain here till April 1st, and then hurrah for home and quiet work.

LETTER 438. TO J. JENNER WEIR. 4, Chester Place, N.W., March 27th
[1868].

I hardly know which of your three last letters has interested me most.
What splendid work I shall have hereafter in selecting and arranging
all your facts. Your last letter is most curious--all about the
bird-catchers--and interested us all. I suppose the male chaffinch
in "pegging" approaches the captive singing-bird, from rivalry or
jealousy--if I am wrong please tell me; otherwise I will assume so. Can
you form any theory about all the many cases which you have given me,
and others which have been published, of when one [of a] pair is killed,
another soon appearing? Your fact about the bullfinches in your garden
is most curious on this head. (438/1. Mr. Weir stated that at Blackheath
he never saw or heard a wild bullfinch, yet when one of his caged males
died, a wild one in the course of a few days generally came and perched
near the widowed female, whose call-note is not loud