males, and he believes this is so with other migratory birds. But this
does not agree with what the bird-catchers say about the common linnet,
which I suppose migrates within the limits of England.

Many thanks for very curious case of Pavo nigripennis. (438/2. See
"Animals and Plants," Edition II., Volume I., page 306.) I am very glad to
get additional evidence. I have sent your fact to be inserted, if not too
late, in four foreign editions which are now printing. I am delighted to
hear that you approve of my book; I thought every mortal man would find the
details very tedious, and have often repented of giving so many. You will
find pangenesis stiff reading, and I fear will shake your head in
disapproval. Wallace sticks up for the great god Pan like a man.

The fertility of hybrid canaries would be a fine subject for careful
investigation.


LETTER 439. TO J. JENNER WEIR.
Down, April 4th [1868].

I read over your last ten (!) letters this morning, and made an index of
their contents for easy reference; and what a mine of wealth you have
bestowed on me. I am glad you will publish yourself on gay-coloured
caterpillars and birds (439/1. See "Descent of Man," Edition I., Volume
I., page 417, where Mr. Weir's experiments are given; they were made to
test Mr. Wallace's theory that caterpillars, which are protected against
birds by an unpleasant taste, have been rendered conspicuous, so that they
are easily recognised. They thus escape being pecked or tasted, which to
soft-skinned animals would be as fatal as being devoured. See Mr. Jenner
Weir's papers, "Transact. Entomolog. Soc." 1869, page 2; 1870, page 337.