More Letters of Charles Darwin Volume I

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LETTER 202. TO T.H. HUXLEY.
Down, June 12th [1867?].

We come up on Saturday, the 15th, for a week. I want much to see you for a
short time to talk about my youngest boy and the School of Mines. I know
it is rather unreasonable, but you must let me come a little after 10
o'clock on Sunday morning, the 16th. If in any way inconvenient, send me a
line to "6, Queen Anne Street W.,"; but if I do not hear, I will (stomacho
volente) call, but I will not stay very long and spoil your whole morning
as a holiday. Will you turn two or three times in your mind this question:
what I called "pangenesis" means that each cell throws off an atom of its
contents or a gemmule, and that these aggregated form the true ovule or
bud, etc.? Now I want to know whether I could not invent a better word.
"Cyttarogenesis" (202/1. From kuttaros, a bee's-cell: cytogenesis would
be a natural form of the word from kutos.)--i.e. cell-genesis--is more true
and expressive, but long. "Atomogenesis" sounds rather better, I think,
but an "atom" is an object which cannot be divided; and the term might
refer to the origin of atoms of inorganic matter. I believe I like
"pangenesis" best, though so indefinite; and though my wife says it sounds
wicked, like pantheism; but I am so familiar now with this word, that I
cannot judge. I supplicate you to help me.

LETTER 203. TO A.R. WALLACE.
Down, October, 12th and 13th [1867].

I ordered the journal (203/1. "Quarterly Journal of Science," October,
1867, page 472. A review of the Duke of Argyll's "Reign of Law.") a long
time ago, but by some oversight received it only yesterday, and read it.
You will think my praise not worth having, from being so indiscriminate;
but if I am to speak the truth, I must say I admire every word. You have
just touched on the points which I particularly wished to see noticed. I
am glad you had the courage to take up Angraecum (203/2. Angraecum
sesquipedale, a Madagascan orchid, with a whiplike nectary, 11 to 12 inches
in length, which, according to Darwin ("Fertilisation of Orchids," Edition
II., page 163), is adapted to the visits of a moth with a proboscis of
corresponding length. He points out that there is no difficulty in
believing in the existence of such a moth as F. Muller has described
("Nature," 1873, page 223)--a Brazilian sphinx-moth with a trunk of 10 to
11 inches in length. Moreover, Forbes has given evidence to show that such
an insect does exist in Madagascar ("Nature," VIII., 1873, page 121). The
case of Angraecum was put forward by the Duke of Argyll as being
necessarily due to the personal contrivance of the Deity. Mr. Wallace
(page 476) shows that both proboscis and nectary might be increased in
length by means of Natural Selection. It may be added that Hermann Muller
has shown good grounds for believing that mutual specialisation of this
kind is beneficial both to insect and plant.) after the Duke's attack; for
I believe the principle in this case may be widely applied. I like the
figure, but I wish the artist had drawn a better sphinx. With respect to
beauty, your remarks on hideous objects and on flowers not being made
beautiful except when of practical use to them, strike me as very good. On
this one point of beauty I can hardly think that the Duke was quite candid.
I have used in the concluding paragraph of my present book precisely the
same argument as you have, even bringing in the bull-dog (203/3.
"Variation of Animals and Plants," Edition I., Volume II., page 431: "Did
He cause the frame and mental qualities of the dog to vary in order that a
breed might be formed of indomitable ferocity, with jaws fitted to pin down
the bull for man's brutal sport?"), with respect to variations not having
been specially ordained. Your metaphor of the river (203/4. See Wallace,
op. cit., pages 477-8. He imagines an observer examining a great river-
system, and finding everywhere adaptations which reveal the design of the
Creator. "He would see special adaptation to the wants of man in broad,
quiet, navigable rivers, through fertile alluvial plains that would support
a large population, while the rocky streams and mountain torrents were
confined to those sterile regions suitable only for a small population of
shepherds and herdsmen.') is new to me, and admirable; but your other
metaphor, in which you compare classification and complex machines, does
not seem to me quite appropriate, though I cannot point out what seems
deficient. The point which seems to me strong is that all naturalists
admit that there is a natural classification, and it is this which descent
explains. I wish you had insisted a little more against the "North
British" (203/5. At page 485 Mr. Wallace deals with Fleeming Jenkin's
review in the "North British Review," 1867. The review strives to show
that there are strict limits to variation, since the most rigorous and
long-continued selection does not indefinitely increase such a quality as
the fleetness of a racehorse. On this Mr. Wallace remarks that "this
argument fails to meet the real question," which is, not whether indefinite
change is possible, "but whether such differences as do occur in nature
could have been produced by the accumulation of variations by selection.")
on the reviewer assuming that each variation which appears is a strongly
marked one; though by implication you have made this very plain. Nothing
in your whole article has struck me more than your view with respect to the
limit of fleetness in the racehorse and other such cases: I shall try and
quote you on this head in the proof of my concluding chapter. I quite
missed this explanation, though in the case of wheat I hit upon something
analogous. I am glad you praise the Duke's book, for I was much struck
with it. The part about flight seemed to me at first very good; but as the
wing is articulated by a ball-and-socket joint, I suspect the Duke would
find it very difficult to give any reason against the belief that the wing
strikes the air more or less obliquely. I have been very glad to see your
article and the drawing of the butterfly in "Science Gossip." By the way,
I cannot but think that you push protection too far in some cases, as with
the stripes on the tiger. I have also this morning read an excellent
abstract in the "Gardeners' Chronicle" of your paper on nests. (203/6. An
abstract of a paper on "Birds' Nests and Plumage," read before the British
Association: see "Gard. Chron." 1867, page 1047.) I was not by any means
fully converted by your letter, but I think now I am so; and I hope it will
be published somewhere in extenso. It strikes me as a capital
generalisation, and appears to me even more original than it did at
first...

I have finished Volume I. of my book ["Variation of Animals and Plants"],
and I hope the whole will be out by the end of November. If you have the
patience to read it through, which is very doubtful, you will find, I
think, a large accumulation of facts which will be of service to you in
future papers; and they could not be put to better use, for you certainly
are a master in the noble art of reasoning.

LETTER 204. TO T.H. HUXLEY.
Down, October 3rd [no date].

I know you have no time for speculative correspondence; and I did not in
the least expect an answer to my last. But I am very glad to have had it,
for in my eclectic work the opinions of the few good men are of great value
to me.

I knew, of course, of the Cuvierian view of classification (204/1. Cuvier
proved that "animals cannot be arranged in a single series, but that there
are several distinct plans of organisation to be observed among them, no
one of which, in its highest and most complicated modification, leads to
any of the others" (Huxley's "Darwiniana," page 215).); but I think that
most naturalists look for something further, and search for "the natural
system,"--"for the plan on which the Creator has worked," etc., etc. It is
this further element which I believe to be simply genealogical.

But I should be very glad to have your answer (either when we meet or by
note) to the following case, taken by itself, and not allowing yourself to
look any further than to the point in question. Grant all races of man
descended from one race--grant that all the structure of each race of man
were perfectly known--grant that a perfect table of the descent of each
race was perfectly known--grant all this, and then do you not think that
most would prefer as the best classification, a genealogical one, even if
it did occasionally put one race not quite so near to another, as it would
have stood, if collocated by structure alone? Generally, we may safely
presume, that the resemblance of races and their pedigrees would go
together.

I should like to hear what you would say on this purely theoretical case.

It might be asked why is development so all-potent in classification, as I
fully admit it is? I believe it is because it depends on, and best
betrays, genealogical descent; but this is too large a point to enter on.

LETTER 205. TO C. LYELL.
Down, December 7th [1867].

I send by this post the article in the Victorian Institute with respect to
frogs' spawn. If you remember in your boyhood having ever tried to take a
small portion out of the water, you will remember that it is most
difficult. I believe all the birds in the world might alight every day on
the spawn of batrachians, and never transport a single ovum. With respect
to the young of molluscs, undoubtedly if the bird to which they were
attached alighted on the sea, they would be instantly killed; but a land-
bird would, I should think, never alight except under dire necessity from
fatigue. This, however, has been observed near Heligoland (205/1.
Instances are recorded by Gatke in his "Heligoland as an Ornithological
Observatory" (translated by Rudolph Rosenstock, Edinburgh, 1895) of land-
birds, such as thrushes, buntings, finches, etc., resting for a short time
on the surface of the water. The author describes observations made by
himself about two miles west of Heligoland (page 129).); and land-birds,
after resting for a time on the tranquil sea, have been seen to rise and
continue their flight. I cannot give you the reference about Heligoland
without much searching. This alighting on the sea may aid you in your
unexpected difficulty of the too-easy diffusion of land-molluscs by the
agency of birds. I much enjoyed my morning's talk with you.

LETTER 206. TO F. HILDEBRAND.
Down, January 5th [1868].

I thank you for your letter, which has quite delighted me. I sincerely
congratulate you on your success in making a graft-hybrid (206/1. Prof.
Hildebrand's paper is in the "Bot. Zeitung," 1868: the substance is given
in "Variation of Animals and Plants," Edition II., Volume I., page 420.),
for I believe it to be a most important observation. I trust that you will
publish full details on this subject and on the direct action of pollen
(206/2. See Prof. Hildebrand, "Bot. Zeitung," 1868, and "Variation of
Animals and Plants," Edition II., Volume I., page 430. A yellow-grained
maize was fertilised with pollen from a brown-grained one; the result was
that ears were produced bearing both yellow and dark-coloured grains.): I
hope that you will be so kind as to send me a copy of your paper. If I had
succeeded in making a graft-hybrid of the potato, I had intended to raise
seedlings from the graft-hybrid and from the two parent-forms (excluding
insects) and carefully compare the offspring. This, however, would be
difficult on account of the sterility and variability of the potato. When
in the course of a few months you receive my second volume (206/3. This
sentence may be paraphrased--"When you receive my book and read the second
volume."), you will see why I think these two subjects so important. They
have led me to form a hypothesis on the various forms of reproduction,
development, inheritance, etc., which hypothesis, I believe, will
ultimately be accepted, though how it will be now received I am very
doubtful.

Once again I congratulate you on your success.

LETTER 207. TO J.D. HOOKER.
Down, January 6th [1868].

Many thanks about names of plants, synonyms, and male flowers--all that I
wanted.

I have been glad to see Watson's letter, and am sorry he is a renegade
about Natural Selection. It is, as you say, characteristic, with the final
fling at you.

His difficulty about the difference between the two genera of St. Helena
Umbellifers is exactly the same as what Nageli has urged in an able
pamphlet (207/1. "Ueber Entstehung und Begriff der naturhist. Art."
"Sitz. der K. Bayer. Akad. Der Wiss. zu Munchen," 1865. Some of Nageli's
points are discussed in the "Origin," Edition V., page 151.), and who in
consequence maintains that there is some unknown innate tendency to
progression in all organisms. I said in a letter to him that of course I
could not in the least explain such cases; but that they did not seem to me
of overwhelming force, as long as we are quite ignorant of the meaning of
such structures, whether they are of any service to the plants, or
inevitable consequences of modifications in other parts.

I cannot understand what Watson means by the "counter-balance in nature" to
divergent variation. There is the counterbalance of crossing, of which my
present work daily leads me to see more and more the efficiency; but I
suppose he means something very different. Further, I believe variation to
be divergent solely because diversified forms can best subsist. But you
will think me a bore.

I enclose half a letter from F. Muller (which please return) for the chance
of your liking to see it; though I have doubted much about sending it, as
you are so overworked. I imagine the Solanum-like flower is curious.

I heard yesterday to my joy that Dr. Hildebrand has been experimenting on
the direct action of pollen on the mother-plant with success. He has also
succeeded in making a true graft-hybrid between two varieties of potatoes,
in which I failed. I look at this as splendid for pangenesis, as being
strong evidence that bud-reproduction and seminal reproduction do not
essentially differ.

My book is horribly delayed, owing to the accursed index-maker. (207/2.
Darwin thoroughly appreciated the good work put into the index of "The
Variation of Animals and Plants.") I have almost forgotten it!

LETTER 208. TO T.H. HUXLEY.
Down, January 30th [1868].

Most sincere thanks for your kind congratulations. I never received a note
from you in my life without pleasure; but whether this will be so after you
have read pangenesis (208/1. In Volume II. of "Animals and Plants, 1868.),
I am very doubtful. Oh Lord, what a blowing up I may receive! I write now
partly to say that you must not think of looking at my book till the
summer, when I hope you will read pangenesis, for I care for your opinion
on such a subject more than for that of any other man in Europe. You are
so terribly sharp-sighted and so confoundedly honest! But to the day of my
death I will always maintain that you have been too sharp-sighted on
hybridism; and the chapter on the subject in my book I should like you to
read: not that, as I fear, it will produce any good effect, and be hanged
to you.

I rejoice that your children are all pretty well. Give Mrs. Huxley the
enclosed (208/2. Queries on Expression.), and ask her to look out when one
of her children is struggling and just going to burst out crying. A dear
young lady near here plagued a very young child for my sake, till it cried,
and saw the eyebrows for a second or two beautifully oblique, just before
the torrent of tears began.

The sympathy of all our friends about George's success (it is the young
Herald) (208/3. His son George was Second Wrangler in 1868; as a boy he
was an enthusiast in heraldry.) has been a wonderful pleasure to us.
George has not slaved himself, which makes his success the more
satisfactory. Farewell, my dear Huxley, and do not kill yourself with
work.

(209/1. The following group of letters deals with the problem of the
causes of the sterility of hybrids. Mr. Darwin's final view is given in
the "Origin," sixth edition (page 384, edition 1900). He acknowledges that
it would be advantageous to two incipient species, if by physiological
isolation due to mutual sterility, they could be kept from blending: but
he continues, "After mature reflection it seems to me that this could not
have been effected through Natural Selection." And finally he concludes
(page 386):--

"But it would be superfluous to discuss this question in detail; for with
plants we have conclusive evidence that the sterility of crossed species
must be due to some principle quite independent of Natural Selection. Both
Gartner and Kolreuter have proved that in genera including numerous
species, a series can be formed from species which when crossed yield fewer
and fewer seeds, to species which never produce a single seed, but yet are
affected by the pollen of certain other species, for the germen swells. It
is here manifestly impossible to select the more sterile individuals, which
have already ceased to yield seeds; so that this acme of sterility, when
the germen alone is affected, cannot have been gained through selection;
and from the laws governing the various grades of sterility being so
uniform throughout the animal and vegetable kingdoms, we may infer that the
cause, whatever it may be, is the same or nearly the same in all cases."

Mr. Wallace, on the other hand, still adheres to his view: see his
"Darwinism," 1889, page 174, and for a more recent statement see page 292,
note 1, Letter 211, and page 299.

The discussion of 1868 began with a letter from Mr. Wallace, written
towards the end of February, giving his opinion on the "Variation of
Animals and Plants;" the discussion on the sterility of hybrids is at page
185, Volume II., of the first edition.)

LETTER 209. A.R. WALLACE TO CHARLES DARWIN.
February 1868.

The only parts I have yet met with where I somewhat differ from your views,
are in the chapter on the causes of variability, in which I think several
of your arguments are unsound: but this is too long a subject to go into
now. Also, I do not see your objection to sterility between allied species
having been aided by Natural Selection. It appears to me that, given a
differentiation of a species into two forms, each of which was adapted to a
special sphere of existence, every slight degree of sterility would be a
positive advantage, not to the individuals who were sterile, but to each
form. If you work it out, and suppose the two incipient species a...b to
be divided into two groups, one of which contains those which are fertile
when the two are crossed, the other being slightly sterile, you will find
that the latter will certainly supplant the former in the struggle for
existence; remembering that you have shown that in such a cross the
offspring would be more vigorous than the pure breed, and therefore would
certainly soon supplant them, and as these would not be so well adapted to
any special sphere of existence as the pure species a and b, they would
certainly in their turn give way to a and b.

LETTER 210. TO A.R. WALLACE.
February 27th [1868].

I shall be very glad to hear, at some future day, your criticisms on the
"causes of variability." Indeed, I feel sure that I am right about
sterility and Natural Selection. Two of my grown-up children who are acute
reasoners have two or three times at intervals tried to prove me wrong; and
when your letter came they had another try, but ended by coming back to my
side. I do not quite understand your case, and we think that a word or two
is misplaced. I wish some time you would consider the case under the
following point of view. If sterility is caused or accumulated through
Natural Selection, then, as every degree exists up to absolute barrenness,
Natural Selection must have the power of increasing it. Now take two
species A and B, and assume that they are (by any means) half-sterile,
i.e., produce half the full number of offspring. Now try and make (by
Natural Selection) A and B absolutely sterile when crossed, and you will
find how difficult it is. I grant, indeed it is certain, that the degree
of the sterility of the individuals of A and B will vary; but any such
extra-sterile individuals of, we will say A, if they should hereafter breed
with other individuals of A, will bequeath no advantage to their progeny,
by which these families will tend to increase in number over other families
of A, which are not more sterile when crossed with B. But I do not know
that I have made this any clearer than in the chapter in my book. It is a
most difficult bit of reasoning, which I have gone over and over again on
paper with diagrams. (210/1. This letter appeared in "Life and Letters,"
III., page 80.)

LETTER 211. A.R. WALLACE TO CHARLES DARWIN.
March 1st, 1868.

I beg to enclose what appears to me a demonstration on your own principles,
that Natural Selection could produce sterility of hybrids. If it does not
convince you, I shall be glad if you will point out where the fallacy lies.
I have taken the two cases of a slight sterility overcoming perfect
fertility, and of a perfect sterility overcoming a partial fertility,--the
beginning and end of the process. You admit that variations in fertility
and sterility occur, and I think you will also admit that if I demonstrate
that a considerable amount of sterility would be advantageous to a variety,
that is sufficient proof that the slightest variation in that direction
would be useful also, and would go on accumulating.

1. Let there be a species which has varied into two forms, each adapted to
existing conditions (211/1. "Existing conditions," means of course new
conditions which have now come into existence. And the "two" being both
better adapted than the parent form, means that they are better adapted
each to a special environment in the same area--as one to damp, another to
dry places; one to woods, another to open grounds, etc., etc., as Darwin
had already explained. A.R.W. (1899).) better than the parent form, which
they supplant.

2. If these two forms, which are supposed to co-exist in the same
district, do not intercross, Natural Selection will accumulate favourable
variations, till they become sufficiently well adapted to their conditions
of life and form two allied species.

3. But if these two forms freely intercross with each other and produce
hybrids which are also quite fertile inter se, then the formation of the
two distinct races or species will be retarded or perhaps entirely
prevented; for the offspring of the crossed unions will be more vigorous
owing to the cross, although less adapted to their conditions of life than
either of the pure breeds. (211/2. After "pure breeds," add "because less
specialised." A.R.W. (1899).)

4. Now let a partial sterility of some individuals of these two forms
arise when they intercross; and as this would probably be due to some
special conditions of life, we may fairly suppose it to arise in some
definite portion of the area occupied by the two forms.

5. The result is that in this area hybrids will not increase so rapidly as
before; and as by the terms of the problem the two pure forms are better
suited to the conditions of life than the hybrids, they will tend to
supplant the latter altogether whenever the struggle for existence becomes
severe.

6. We may fairly suppose, also, that as soon as any sterility appears
under natural conditions, it will be accompanied by some disinclination to
cross-unions; and this will further diminish the production of hybrids.

7. In the other part of the area, however, where hybridism occurs
unchecked, hybrids of various degrees will soon far outnumber the parent or
pure form.

8. The first result, then, of a partial sterility of crosses appearing in
one part of the area occupied by the two forms, will be, that the GREAT
MAJORITY of the individuals will there consist of the pure forms only,
while in the rest of the area these will be in a minority,--which is the
same as saying, that the new sterile or physiological variety of the two
forms will be better suited to the conditions of existence than the
remaining portion which has not varied physiologically.

9. But when the struggle for existence becomes severe, that variety which
is best adapted to the conditions of existence always supplants that which
is imperfectly adapted; therefore by Natural Selection the sterile
varieties of the two forms will become established as the only ones.

10. Now let a fresh series of variations in the amount of sterility and in
the disinclination to crossed unions occur,--also in certain parts of the
area: exactly the same result must recur, and the progeny of this new
physiological variety again in time occupy the whole area.

11. There is yet another consideration that supports this view. It seems
probable that the variations in amount of sterility would to some extent
concur with and perhaps depend upon the structural variations; so that just
in proportion as the two forms diverged and became better adapted to the
conditions of existence, their sterility would increase. If this were the
case, then Natural Selection would act with double strength, and those
varieties which were better adapted to survive both structurally and
physiologically, would certainly do so. (211/3. The preceding eleven
paragraphs are substantially but not verbally identical with the statement
of the argument in Mr. Wallace's "Darwinism," 1889. Pages 179, 180, note
1.)