More Letters of Charles Darwin Volume II

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LETTER 436. TO J. JENNER WEIR.
4, Chester Place, Regent's Park, N.W., March 13th [1868].

You make a very great mistake when you speak of "the risk of your notes
boring me." They are of the utmost value to me, and I am sure I shall
never be tired of receiving them; but I must not be unreasonable. I shall
give almost all the facts which you have mentioned in your two last notes,
as well as in the previous ones; and my only difficulty will be not to give
too much and weary my readers. Your last note is especially valuable about
birds displaying the beautiful parts of their plumage. Audubon (436/1. In
his "Ornithological Biography," 5 volumes, Edinburgh, 1831-49.) gives a
good many facts about the antics of birds during courtship, but nothing
nearly so much to the purpose as yours. I shall never be able to resist
giving the whole substance of your last note. It is quite a new light to
me, except with the peacock and Bird of Paradise. I must now look to
turkey's wings; but I do not think that their wings are beautiful when
opened during courtship. Its tail is finely banded. How about the drake
and Gallus bankiva? I forget how their wings look when expanded. Your
facts are all the more valuable as I now clearly see that for butterflies I
must trust to analogy altogether in regard to sexual selection. But I
think I shall make out a strong case (as far as the rather deceitful guide
of analogy will serve) in the sexes of butterflies being alike or differing
greatly--in moths which do not display the lower surface of their wings not
having them gaudily coloured, etc., etc.--nocturnal moths, etc.--and in
some male insects fighting for the females, and attracting them by music.

My discussion on sexual selection will be a curious one--a mere dovetailing
of information derived from you, Bates, Wallace, etc., etc., etc.

We remain at above address all this month, and then return home. In the
summer, could I persuade you to pay us a visit of a day or two, and I would
try and get Bates and some others to come down? But my health is so
precarious, I can ask no one who will not allow me the privilege of a poor
old invalid; for talking, I find by long and dear-bought experience, tries
my head more than anything, and I am utterly incapable of talking more than
half an hour, except on rare occasions.

I fear this note is very badly written; but I was very ill all yesterday,
and my hand shakes to-day.

LETTER 437. TO J. JENNER WEIR.
4, Chester Place, Regent's Park, N.W., March 22nd [1868].

I hope that you will not think me ungrateful that I have not sooner
answered your note of the 16th; but in fact I have been overwhelmed both
with calls and letters; and, alas! one visit to the British Museum of an
hour or hour and a half does for me for the whole day.

I was particularly glad to hear your and your brother's statement about the
"gay" deceiver-pigeons. (437/1. Some cock pigeons "called by our English
fanciers gay birds are so successful in their gallantries that, as Mr. H.
Weir informs me, they must be shut up, on account of the mischief which
they cause.") I did not at all know that certain birds could win the
affections of the females more than other males, except, indeed, in the
case of the peacock. Conversely, Mr. Hewitt, I remember, states that in
making hybrids the cock pheasant would prefer certain hen fowls and
strongly dislike others. 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. "Descent of Man" (1901), page 623.) Are
there everywhere many unpaired birds? What can the explanation be?

Mr. Gould assures me that all the nightingales which first come over are
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.
In regard to one of these papers Mr. Darwin wrote (May 13th, 1869): "Your
verification of Wallace's suggestion seems to me to amount to quite a
discovery."); it seems to me much the best plan; therefore, I will not
forward your letter to Mr. Wallace. I was much in the Zoological Gardens
during my month in London, and picked up what scraps of knowledge I could.
Without my having mentioned your most interesting observations on the
display of the Fringillidae (439/2. "Descent of Man" (1901), page 738.),
Mr. Bartlett told me how the Gold Pheasant erects his collar and turns from
side to side, displaying it to the hen. He has offered to give me notes on
the display of all Gallinaceae with which he is acquainted; but he is so
busy a man that I rather doubt whether he will ever do so.

I received about a week ago a remarkably kind letter from your brother, and
I am sorry to hear that he suffers much in health. He gave me some fine
facts about a Dun Hen Carrier which would never pair with a bird of any
other colour. He told me, also, of some one at Lewes who paints his dog!
and will inquire about it. By the way, Mr. Trimen tells me that as a boy
he used to paint butterflies, and that they long haunted the same place,
but he made no further observations on them. As far as colour is
concerned, I see I shall have to trust to mere inference from the males
displaying their plumage, and other analogous facts. I shall get no direct
evidence of the preference of the hens. Mr. Hewitt, of Birmingham, tells
me that the common hen prefers a salacious cock, but is quite indifferent
to colour.

Will you consider and kindly give me your opinion on the two following
points. Do very vigorous and well-nourished hens receive the male earlier
in the spring than weaker or poorer hens? I suppose that they do.
Secondly, do you suppose that the birds which pair first in the season have
any advantage in rearing numerous and healthy offspring over those which
pair later in the season? With respect to the mysterious cases of which
you have given me so many, in addition to those previously collected, of
when one bird of a pair is shot another immediately supplying its place, I
was drawing to the conclusion that there must be in each district several
unpaired birds; yet this seems very improbable. You allude, also, to the
unknown causes which keep down the numbers of birds; and often and often
have I marvelled over this subject with respect to many animals.

LETTER 440. TO A.R. WALLACE.

(440/1. The following refers to Mr. Wallace's article "A Theory of Birds'
Nests," in Andrew Murray's "Journal of Travel," Volume I., page 73. He
here treats in fuller detail the view already published in the "Westminster
Review," July 1867, page 38. The rule which Mr. Wallace believes, with
very few exceptions, to hold good is, "that when both sexes are of
strikingly gay and conspicuous colours, the nest is...such as to conceal
the sitting bird; while, whenever there is a striking contrast of colours,
the male being gay and conspicuous, the female dull and obscure, the nest
is open, and the sitting bird exposed to view." At this time Mr. Wallace
allowed considerably more influence to sexual selection (in combination
with the need of protection) than in his later writings. The following
extract from a letter from Mr. Wallace to Darwin (July 23rd, 1877) fixes
the period at which the change in his views occurred: "I am almost afraid
to tell you that in going over the subject of the colours of animals, etc.,
etc., for a small volume of essays, etc., I am preparing, I have come to
conclusions directly opposed to voluntary sexual selection, and believe
that I can explain (in a general way) all the phenomena of sexual ornaments
and colours by laws of development aided by simple 'Natural Selection.'"
He finally rejected Mr. Darwin's theory that colours "have been developed
by the preference of the females, the more ornamented males becoming the
parents of each successive generation." "Darwinism," 1889, page 285. See
also Letters 442, 443, 449, 450, etc.)

Down, April 15th, [1868].

I have been deeply interested by your admirable article on birds' nests. I
am delighted to see that we really differ very little,--not more than two
men almost always will. You do not lay much or any stress on new
characters spontaneously appearing in one sex (generally the male), and
being transmitted exclusively, or more commonly only in excess, to that
sex. I, on the other hand, formerly paid far too little attention to
protection. I had only a glimpse of the truth; but even now I do not go
quite as far as you. I cannot avoid thinking rather more than you do about
the exceptions in nesting to the rule, especially the partial exceptions,
i.e., when there is some little difference between the sexes in species
which build concealed nests. I am not quite satisfied about the incubating
males; there is so little difference in conspicuousness between the sexes.
I wish with all my heart I could go the whole length with you. You seem to
think that male birds probably select the most beautiful females; I must
feel some doubt on this head, for I can find no evidence of it. Though I
am writing so carping a note, I admire the article thoroughly.

And now I want to ask a question. When female butterflies are more
brilliant than their males you believe that they have in most cases, or in
all cases, been rendered brilliant so as to mimic some other species, and
thus escape danger. But can you account for the males not having been
rendered equally brilliant and equally protected? (440/2. See Wallace in
the "Westminster Review," July, 1867, page 37, on the protection to the
female insect afforded by its resemblance either to an inanimate object or
to another insect protected by its unpalatableness. The cases are
discussed in relation to the much greater importance (to the species as a
whole) of the preservation of the female insect with her load of eggs than
the male who may safely be sacrificed after pairing. See Letter 189,
note.) Although it may be most for the welfare of the species that the
female should be protected, yet it would be some advantage, certainly no
disadvantage, for the unfortunate male to enjoy an equal immunity from
danger. For my part, I should say that the female alone had happened to
vary in the right manner, and that the beneficial variations had been
transmitted to the same sex alone. Believing in this, I can see no
improbability (but from analogy of domestic animals a strong probability)
that variations leading to beauty must often have occurred in the males
alone, and been transmitted to that sex alone. Thus I should account in
many cases for the greater beauty of the male over the female, without the
need of the protective principle. I should be grateful for an answer on
the point.

LETTER 441. TO J. JENNER WEIR.
Down, April 18th [1868].

You see that I have taken you at your word, and have not (owing to heaps of
stupid letters) earlier noticed your three last letters, which as usual are
rich in facts. Your letters make almost a little volume on my table. I
daresay you hardly knew yourself how much curious information was lying in
your mind till I began the severe pumping process. The case of the
starling married thrice in one day is capital, and beats the case of the
magpies of which one was shot seven times consecutively. A gamekeeper here
tells me that he has repeatedly shot one of a pair of jays, and it has
always been immediately replaced. I begin to think that the pairing of
birds must be as delicate and tedious an operation as the pairing of young
gentlemen and ladies. If I can convince myself that there are habitually
many unpaired birds, it will be a great aid to me in sexual selection,
about which I have lately had many troubles, and am therefore rejoiced to
hear in your last note that your faith keeps staunch. That is a curious
fact about the bullfinches all appearing to listen to the German singer
(441/1. See Letter 445, note.); and this leads me to ask how much faith
may I put in the statement that male birds will sing in rivalry until they
injure themselves. Yarrell formerly told me that they would sometimes even
sing themselves to death. I am sorry to hear that the painted bullfinch
turns out to be a female; though she has done us a good turn in exhibiting
her jealousy, of which I had no idea.

Thank you for telling me about the wildness of the hybrid canaries:
nothing has hardly ever surprised me more than the many cases of reversion
from crossing. Do you not think it a very curious subject? I have not
heard from Mr. Bartlett about the Gallinaceae, and I daresay I never shall.
He told me about the Tragopan, and he is positive that the blue wattle
becomes gorged with blood, and not air.

Returning to the first of the last three letters. It is most curious the
number of persons of the name of Jenner who have had a strong taste for
Natural History. It is a pity you cannot trace your connection with the
great Jenner, for a duke might be proud of his blood.

I heard lately from Professor Rolleston of the inherited effects of an
injury in the same eye. Is the scar on your son's leg on the same side and
on exactly the same spot where you were wounded? And did the wound
suppurate, or heal by the first intention? I cannot persuade myself of the
truth of the common belief of the influence of the mother's imagination on
the child. A point just occurs to me (though it does not at present
concern me) about birds' nests. Have you read Wallace's recent articles?
(441/2. A full discussion of Mr. Wallace's views is given in "Descent of
Man," Edition I., Volume II., Chapter XV. Briefly, Mr. Wallace's point is
that the dull colour of the female bird is protective by rendering her
inconspicuous during incubation. Thus the relatively bright colour of the
male would not simply depend on sexual selection, but also on the hen being
"saved, through Natural Selection, from acquiring the conspicuous colours
of the male" (loc. cit., page 155).) I always distrust myself when I
differ from him; but I cannot admit that birds learn to make their nests
from having seen them whilst young. I must think it as true an instinct as
that which leads a caterpillar to suspend its cocoon in a particular
manner. Have you had any experience of birds hatched under a foster-mother
making their nests in the proper manner? I cannot thank you enough for all
your kindness.

LETTER 442. TO A.R. WALLACE.

(442/1. Dr. Clifford Allbutt's view probably had reference to the fact
that the sperm-cell goes, or is carried, to the germ-cell, never vice
versa. In this letter Darwin gives the reason for the "law" referred to.
Mr. A.R. Wallace has been good enough to give us the following note:--"It
was at this time that my paper on 'Protective Resemblance' first appeared
in the 'Westminster Review,' in which I adduced the greater, or rather, the
more continuous, importance of the female (in the lower animals) for the
race, and my 'Theory of Birds' Nests' ('Journal of Travel and Natural
History,' No. 2) in which I applied this to the usually dull colours of
female butterflies and birds. It is to these articles as well as to my
letters that Darwin chiefly refers."--Note by Mr. Wallace, May 27th, 1902.)

Down, April 30th [1868].

Your letter, like so many previous ones, has interested me much. Dr.
Allbutt's view occurred to me some time ago, and I have written a short
discussion on it. It is, I think, a remarkable law, to which I have found
no exception. The foundation lies in the fact that in many cases the eggs
or seeds require nourishment and protection by the mother-form for some
time after impregnation. Hence the spermatozoa and antherozoids travel in
the lower aquatic animals and plants to the female, and pollen is borne to
the female organ. As organisms rise in the scale it seems natural that the
male should carry the spermatozoa to the female in his own body. As the
male is the searcher, he has required and gained more eager passions than
the female; and, very differently from you, I look at this as one great
difficulty in believing that the males select the more attractive females;
as far as I can discover, they are always ready to seize on any female, and
sometimes on many females. Nothing would please me more than to find
evidence of males selecting the more attractive females. I have for months
been trying to persuade myself of this. There is the case of man in favour
of this belief, and I know in hybrid unions of males preferring particular
females, but, alas, not guided by colour. Perhaps I may get more evidence
as I wade through my twenty years' mass of notes.

I am not shaken about the female protected butterflies. I will grant (only
for argument) that the life of the male is of very little value,--I will
grant that the males do not vary, yet why has not the protective beauty of
the female been transferred by inheritance to the male? The beauty would
be a gain to the male, as far as we can see, as a protection; and I cannot
believe that it would be repulsive to the female as she became beautiful.
But we shall never convince each other. I sometimes marvel how truth
progresses, so difficult is it for one man to convince another, unless his
mind is vacant. Nevertheless, I myself to a certain extent contradict my
own remark, for I believe far more in the importance of protection than I
did before reading your articles.

I do not think you lay nearly stress enough in your articles on what you
admit in your letters: viz., "there seems to be some production of
vividness...of colour in the male independent of protection." This I am
making a chief point; and have come to your conclusion so far that I
believe that intense colouring in the female sex is often checked by being
dangerous.

That is an excellent remark of yours about no known case of male alone
assuming protective colours; but in the cases in which protection has been
gained by dull colours, I presume that sexual selection would interfere
with the male losing his beauty. If the male alone had acquired beauty as
a protection, it would be most readily overlooked, as males are so often
more beautiful than their females. Moreover, I grant that the life of the
male is somewhat less precious, and thus there would be less rigorous
selection with the male, so he would be less likely to be made beautiful
through Natural Selection for protection. (442/2. This does not apply to
sexual selection, for the greater the excess of males, and the less
precious their lives, so much the better for sexual selection. [Note in
original.]) But it seems to me a good argument, and very good if it could
be thoroughly established. I do not know whether you will care to read
this scrawl.

LETTER 443. TO A.R. WALLACE.
Down, May 5th [1868?].

I am afraid I have caused you a great deal of trouble in writing to me at
such length. I am glad to say that I agree almost entirely with your
summary, except that I should put sexual selection as an equal, or perhaps
as even a more important agent in giving colour than Natural Selection for
protection. As I get on in my work I hope to get clearer and more decided
ideas. Working up from the bottom of the scale, I have as yet only got to
fishes. What I rather object to in your articles is that I do not think
any one would infer from them that you place sexual selection even as high
as No. 4 in your summary. It was very natural that you should give only a
line to sexual selection in the summary to the "Westminster Review," but
the result at first to my mind was that you attributed hardly anything to
its power. In your penultimate note you say "in the great mass of cases in
which there is great differentiation of colour between the sexes, I believe
it is due almost wholly to the need of protection to the female." Now,
looking to the whole animal kingdom, I can at present by no means admit
this view; but pray do not suppose that because I differ to a certain
extent, I do not thoroughly admire your several papers and your admirable
generalisation on birds' nests. With respect to this latter point,
however, although, following you, I suspect that I shall ultimately look at
the whole case from a rather different point of view.

You ask what I think about the gay-coloured females of Pieris. (443/1.
See "Westminster Review," July, 1867, page 37; also Letter 440.) I believe
I quite follow you in believing that the colours are wholly due to mimicry;
and I further believe that the male is not brilliant from not having
received through inheritance colour from the female, and from not himself
having varied; in short, that he has not been influenced by selection.

I can make no answer with respect to the elephants. With respect to the
female reindeer, I have hitherto looked at the horns simply as the
consequence of inheritance not having been limited by sex.

Your idea about colour being concentrated in the smaller males seems good,
and I presume that you will not object to my giving it as your suggestion.

LETTER 444. TO J. JENNER WEIR.
Down, May 7th [1868].

I have now to thank you for no less than four letters! You are so kind
that I will not apologise for the trouble I cause you; but it has lately
occurred to me that you ought to publish a paper or book on the habits of
the birds which you have so carefully observed. But should you do this, I
do not think that my giving some of the facts for a special object would
much injure the novelty of your work. There is such a multitude of points
in these last letters that I hardly know what to touch upon. Thanks about
the instinct of nidification, and for your answers on many points. I am
glad to hear reports about the ferocious female bullfinch. I hope you will
have another try in colouring males. I have now finished lepidoptera, and
have used your facts about caterpillars, and as a caution the case of the
yellow-underwings. I have now begun on fishes, and by comparing different
classes of facts my views are getting a little more decided. In about a
fortnight or three weeks I shall come to birds, and then I dare say that I
shall be extra troublesome. I will now enclose a few queries for the mere
chance of your being able to answer some of them, and I think it will save
you trouble if I write them on a separate slip, and then you can sometimes
answer by a mere "no" or "yes."