WCP1910

[1]¹

9, St Mark's Crescent N.W.

Sept[embe]^r 27^th

Dear Darwin

Your view seems to be, that variations occurring in one sex are transmitted either to that sex exclusively or to both sexes equally ^{or more rarely partially transferred.}. But we have every gradation of sexual colours from total dissimilarity to perfect identity. If this is explained solely by the laws of inheritance, then the colours of one or other sex will be always (in relation to their environment) a matter of chance. I cannot think this. I think selection more powerful than laws of inheritance ^{of which it makes use,} as shown by cases of two three or four forms of female butterflies, all of which have, I have little doubt, been specialized for protection.

To answer your ^1st question is most [2] difficult, if not impossible, because we have no sufficient evidence in individual cases of slight sexual difference, to determine whether the the male alone has acquired his superior brightness by sexual selection, or the female been made duller by need of protection ^{or whether the two causes have acted}. Many of the sexual differences of existing species may be inherited differences from parent forms who existed under different conditions & had greater or less need of protection. I think the case of Pieris pyrrha proves, that one sex females alone can be greatly modified for protection.²

I think I admitted before, the general tendency (probably) of males to acquire brighter colours tints. Yet this can not be universal for many female birds & quadrupeds [3] have equally bright tints.

To your second question I can reply more decidedly. I do think the females of the Gallinaceae³ you mention have been modified or been prevented from acquiring the brighter plumage of the male, by need of protection. I know that the Gallus bankiva⁴ frequents drier & more open situations than the peahen of Java, which is found among grassy and leafy vegetation, — corresponding with the colours of the two. So the Argus pheasants ♂ & ♀ are I feel sure protected by their tints corresponding to the dead leaves of the lofty forest in which they dwell, and the female of the gorgeous fire back pheasant, Lophura viellottii [vieillottii]⁵ is of a very similar rich brown colour.

I do not however at all think the [4] question can be settled by individual cases, but ^by only large masses of facts.

The colours of the mass of female birds seem to me strictly analogous to the colours of both sexes of Snipes, woodcocks, Plovers &c. which are undoubtedly protective.

Now, supposing on your view, that the colours of a male bird become more and more brilliant by sexual selection, and a good deal of that colour becomes ^is transmitted to the female till it becomes positively injurious to her during incubation & the race is in danger of extinction; — do you not think that all the females who had acquired less of the male's bright colours ^{or who themselves varied in a protective direction} would be preserved, & that thus a good protective colouring would soon be acquired?

If you admit that this could occur, & can show no good reason why it should not often occur, then we no longer differ for this is the main point of my view.

Have you ever thought of the red wax-tips of the Bombycilla⁶ beautifully imitating, the red fructification of lichens used in the nest, & therefore the females have it too? Yet this is a very sexual-looking character.⁷

We begin printing this week.⁸

Yours very faithfully| Alfred R. Wallace [signature]

P.S. Pray don’t distress yourself on this subject. It will all come right in the end, and after all it is only an episode in your great works. ARW [signature]⁹

[1]¹

If sexes have been differentiated entirely by sex[ua]^l. selection, the female can have no relation to environment.

But in groups when both sexes require protection during feeding or repose, as snipe, woodcock, ptarmingan, desert birds & animals —, ^{green forest birds &c} arctic birds of prey & animals then both sexes are modified for protection. Why sh[oul]^d that power cease to act entirely when sexual differentiation exists & when the female requires protection; & why should the colour of so many female birds ^{seem to} be protective; if it has not been made protective by selection.

Contrary to principles of "origins[?] of species[?]"that colour sh[oul]^d have been produced in both sexes by sexual selection or even have been modified to bring the female into harmony[?] with the environment — "Sexual selection is less rigorous than natural selection"² & will therefore be subordinate to it.

To C.Darwin.) 9, St. Mark's Crescent N.W..Oct'r 4th. 1868

Dear Darwin I should have answered your letter before, but I have been very busy reading over my MSS. the last time before going to press, drawing maps, &c.&c.

Your first question can not be answered, because we have not in individual cases of slight sexual difference, sufficient evidence to determine how much of that difference is due to sexual selection acting on the male,— how much to natural selection (protective) acting on the female,— or how much of the difference may be due to inherited differences from ancestors who lived under different conditions. On your second question I can give an opinion. I do think the females of the Gallinaceae you mention have been either modified, or prevented from acquiring much of the brighter plumage of the males, by the need of protection. I know that Gallus bankiva (?) frequents drier & more open situations than, Pavo muticus (?) which in Java is found among grassy & leafy vegitation,— corresponding with the colours of the two females. So the Argus pheasants male & female are I feel sure protected by their tints corresponding to dead leaves of the dry lofty forests in which they dwell; and the female of the gorgeous fire-back pheasant, Lophula viellottii, is of a very similar rich brown colour.

These and many other colours of female birds seem to me exactly analogous to the colours of both sexes in such groups as the snipes, woodcocks, plovers, ptarmigan, desert birds, arctic animals, green birds

(the second page of the letter has been torn off.) (The last page of this or of another letter was placed with it in the portfolio of letters, copy of which see.) [2]

To C.Darwin.) (Last page of a letter placed next to that of Oct 4th, 1868)

… …even for the pleasure of females. And if the need of protection has been powerful enough to change the females of white Pieris (?) into a variety of colours & a definite pattern, to imitate a Heliconia,— much more easy would it be, merely to tone down brighter colours into obscure tints.

I am sorry to find that our difference of opinion on this point is a source of anxiety to you.

Pray do no let it be so. The truth will come out at last, and our difference may be the means of setting others to work who may set us both right.

After all, this question is only an episode (though an important one) in the great question of the "Origin of Species", and whether you or I are right will not at all affect the main doctrine,— that is one comfort.

I hope you will publish your treatise on "Sexual selection" as a separate book as soon as possible, & then while you are going on with your other work, there will no doubt be found some one to battle with me over your facts, on this hard problem.

With best wishes and kind regards to Mrs Darwin & all your family

Believe me Dear Darwin Yours very faithfully | Alfred R. Wallace.

To C.Darwin.) 9, St. Mark's Crescent N.W..Oct'r 4th.1868

Dear Darwin I should have answered your letter before, but I have been very busy reading over my MSS. the last time before going to press, drawing maps, &c.&c.

Your first question can not be answered, because we have not in individual cases of slight sexual difference, sufficient evidence to determine how much of that difference is due to sexual selection acting on the male,— how much to natural selection (protective) acting on the female;— or how much of the difference may be due to inherited differences from ancestors who lived under different conditions. On your second question I can give an opinion. I do not think the females of the Gallinaceae you mention have been either modified, or prevented from acquiring much of the brighter plumage of the males, by the need of protection. I know that Gallus bankiva (?) frequents drier & more open situations than, Pavo muticus (?) which in Java is found among grassy & leafy vegetation,— corresponding with the colours of the two females. So the Argus pheasants male & female are I feel sure protected by their tints corresponding to dead leaves of the dry lofty forests in which they dwell, and the female of the gorgeous fire-back pheasant, Lophula viellottii, is of a very similar rich brown colour.

These and many other colours of females birds seem to me exactly analogous to the colours of both sexes in such groups as the snipes, woodcocks, plovers, ptarmigan, desert birds, arctic animals, green birds

(the second page of the letter has been torn off.) (The last page of this or of another letter was placed with it in the portfolio of letters, copy of which see.) [2]

To C.Darwin.) (Last page of a letter placed next to that of Oct 4th,1868)

… …even for the pleasure of females. And if the need of protection has been powerful enough to change the females of white Pieris (?) into a variety of colours & a definite pattern, to imitate a Heliconia,— much more easy would it be, merely to tone down brighter colours into obscure tints.

I am sorry to find that our difference of opinion on this point is a source of anxiety to you.

Pray do no let it be so. The truth will come out at last, and our difference may be the means of setting others to work who may set us both right.

After all, this question is only an episode (though an important one) in the great question of the "Origin of Species", and whether you or I are right will not at all affect the main doctrine,— that is one comfort.

I hope you will publish your treatise on "Sexual selection" as a separate book as soon as possible, & then while you are going on with your other work, there will no doubt be found some one to battle with me over your facts, on this hard problem.

With best wishes and kind regards to Mrs Darwin & all your family

Believe me Dear Darwin Yours very faithfully | Alfred R. Wallace.

To C. Darwin.) 9, St. Mark’s Crescent N.W. Sept. 27th. (1868¹)

Dear Darwin

Your view seems to be that variations occurring in one sex are transmitted either to that sex exclusively or to both sexes equally or more rarely partially transferred. But we have every gradation of sexual colours from total dissimilarity to perfect identity. If this is explained solely by the laws of inheritance, then the colours of one or other sex will be always (in relation to their environment) a matter of chance. I cannot think this. I think this. I think selection more powerful than laws of inheritance of which it makes use, as shown by cases of two three or four forms of female butterflies, all of which have, I have little doubt, been specialized for protection.

To answer your first question is most difficult, if not impossible, because we have no sufficient evidence in idividual[sic] cases of slight sexual difference, to determine whether the male alone has acquired his superior brightness by sexual selection, or the female been made duller by need of protection, or whether the two causes have acted. Many of the sexual differences of existing species may be inherited differences from parent forms who existed under different conditions & had greater or less need of protection.

I think I admitted before, the general tendency (probably) of males to acquire brighter tints. Yet this can not be universal for many female birds & quadrupeds have equally bright tints.

²I think the case of (female sign) Pieris Pyrrha³ proves, that females alone can be greatly modified for protection.

To your second question I can reply more decidedly. I do think the females of the Gallinaceae⁴ you mention have been modified or been prevented from acquiring the brighter plumage of the male, by need of protection. I know that Gallus bankiva⁵ frequents drier & more open situations that the peahen of Java, which is found among grassy and leafy vegitation[sic],— corresponding with the colours of the two. So the Argus pheasant male & female (signs) are I feel sure protected by their tints corresponding to the dead leaves of the leafy forest in which they dwell, and the female of the gorgeous fire [2]⁶ back pheasant Lophura viellottii is of a very similar rich brown colour. I do not however at all think the question can be settled by individual cases, but by only large masses of facts.

The colours of the mass of female birds seem to me strictly analagous to the colours of both sexes of Snipes, Woodcocks, Plovers &c. which are undoubtedly protective.

Now, supposing on your view, that the colours of a male bird become more and more brilliant by sexual selection, and a good deal of that colour is transmitted is transmitted to the female to the female[?] till it becomes positively injurious to her during incubation & the race is in danger of extinction,— do you not think that all the females who had acquired less of the male’s bright colours or who themselves varied in a protective direction would be preserved, & that thus a good protective colouring would be acquired? If you admit that this could occur, & can show no good reason why it should not often occur, then we no longer differ for this is the main point of my view.

Have you ever thought of the red wax-tips of the Bombyoilla⁷ beautifully imitating the red fructification of lichens used in the nest, & therefore the females have it too? Yet this is a very sexual looking character.

We begin printing this week.

Yours very faithfully | Alfred R. Wallace. [signature]

P.S. Pray don’t distress yourself on this subject. It will all come right in the end, and after all it is only an episode in your great work. A.R.W. [signature]

If⁷ sexes have been differentiated entirely by sexual selection the females can have no relation to environment. But in groups where the both sexes require protection during feeding or repose, as snipes, woodcock, ptarmigan, desert birds & animals, green forest birds &c, arctic birds of prey (?) & animals then both sexes are modified for protection. Why should that power cease to act entirely when sexual differentiation exists & when [3]⁷ the female requires protection; if it has not been made protective by selection, & why should the colour of so many female birds seem to be protective, if it has not been made protective by protection.

Contrary to principles of "Origin of Species" that colour should have been produced in both sexes by sexual selection & never have been modified to bring the female into harmony with the environment. "Sexual selection is less rigorous than natural selection" & will therefore be subordinate to it.

[1]¹

To C.Darwin.) 9, St.Mark's Crescent N.W. Sept 27th.²

Dear Darwin Your view seems to be that variations occurring in one sex are transmitted either to that sex exclusively or to both sexes equally or more rarely partially transferred. But we have every gradation of sexual colours from total dissimilarity to perfect identity. If this is explained solely by the laws of inheritance, then the colours of one or other sex will be always (in relation to their environment) a matter of chance. I cannot think this. I think this. I think selection more powerful than laws of inheritance of which it makes use, as shown by cases of two three or four forms of female butterflies, all of which have, I have little doubt, been specialized for protection.

To answer your first question is most difficult, if not impossible, because we have no sufficient evidence in i[n]dividual cases of slight sexual difference, to determine whether the male alone has acquired his superior brightness by sexual selection, or the female been made duller by need of protection, or whether the two causes have acted. Many of the sexual differences of existing species may be inherited differences from parent forms who existed under different conditions & had greater or less need of protection.

I think I admitted before, the general tendency (probably) of males to acquire brighter tints. Yet this can not be universal for many female birds & quadrupeds have equally bright tints.

(Note at side of page) — I think the case of (female sign) Pieris pyrrha proves, that females alone can be greatly modified for protection.

To your second question I can reply more decidedly. I do think the females of the Gallinaceae you mention have been modified or been prevented from acquiring³ the brighter plumage of the male⁴, by need of protection. I know that the Gallus bankiva⁵ frequents drier & more open situations than the peahen of Java⁶, which is found among grassy and leafy vegetation,— corresponding with the colours of the two. So the Argus pheasant⁷ male & female (signs) are I feel sure protected by their tints corresponding to the dead leaves of the lofty forest in which they dwell, and the female of the gorgeous fire [2]⁸

To C.Darwin. Sept.27th (1868 ?)

back pheasant Lophura viellottii is of a very similar rich brown colour.

I do not however at all think the question can be settled by individual cases, but by only large masses of facts.

The colours of the mass of female birds seen to me strictly analagous to the colours of both sexes of Snipes, Woodcocks, Plovers &c. which are undoubtedly protective.

Now, supposing on your view, that the colours of a male bird become more and more brilliant by sexual selection, and a good deal of that colour is transmitted is transmitted to the female to the female till it becomes positively injurious to her during incubation & the race is in danger of extinction;— do you not think that all the females who had acquired less of the male's bright colours or who themselves varied in a protective direction would be preserved, & that thus a good protective colouring would be acquired? If you admit that this could occur, & can show no good reason why it should not often occur, then we no longer differ for this is the main point of my view.

Have you ever though of the red wax-tips of the Bombyoilla beautifully imitating the red fructification of lichens used in the nest, & therefore the females have it too? Yet this is a very sexual-looking character.

We begin printing this week. Yours very faithfully | Alfred R. Wallace.

P.S. Pray dont distress yourself on this subject. It will all come right in the end, and after all it is only an opinion in your great work. A.R.W.

(On separate sheet) If sexes have been differentiated entirely by sexual selection the females can have no relation to environment. But in groups where the ^both sexes require protection during feeding or repose, as snipes, woodcock, ptarmigan, desert birds & animals, green forest birds &c, arctic birds of prey (?) & animals then both sexes are modified for protection. Why should that power cease to act entirely when sexual differentiation exists & when [3]⁹

(To C.Darwin. Sept. 27th 1868?)

the female requires protection, if it has not been made protective by selection, & why should the colour of so many female birds seem to be protective; if it has not been made protective by protection.

Contrary to principles of "Origin of Species" that colours should have been produced in both sexes by sexual selection & never have been modified to bring the female into harmony with the environment. "Sexual selection is less rigorous than natural selection" & will therefore be subordinate to it.

(This separate sheet seems to be a note used for writing the above letter.)

[1] [p. 229]

9 St. Mark's Crescent, N.W. October 4, 1868.

Dear Darwin, — I should have answered your letter before, but have been very busy reading over my MSS. the last time before going to press, drawing maps, etc. etc.

Your first question cannot he answered, because we have not, in individual cases of slight sexual difference, sufficient evidence to determine how much of that difference is due to sexual selection acting on the male, how much to natural selection (protective) acting on the female, or how much of the difference may be due to inherited differences from ancestors who lived under different conditions. On your second question I can give an opinion. I do think the [2] [p. 230] females of the Gallinaceae you mention have been either modified, or prevented from acquiring much of the brighter plumage of the males, by the need of protection. I know that Gallus bankiva frequents drier and more open situations than Pavo muticus, which in Java is found among grassy and leafy vegetation corresponding with the colours of tie two females. So the Argus pheasants, male and female, are, I feel sure, protected by their tints corresponding to dead leaves of the dry lofty forests in which they dwell; and the female of the gorgeous fire-back pheasant, Lophura viellottii, is of a very similar rich brown colour.

These and many other colours of female birds seem to me exactly analogous to the colours of both sexes in such groups as the snipes, woodcocks, plovers, ptarmigan, desert birds, Arctic animals, greenbirds.

[Editor's note in the original work:] (The second page of this letter has been torn off. This letter and that of September 27 appear both to answer the same letter from Darwin. The last page of this or of another letter was placed with it in the portfolio of letters; it is now given.)

I am sorry to find that our difference of opinion on this point is a source of anxiety to you.

Pray do not let it be so. The truth will come out at last, and our difference may be the means of setting others to work who may set us both right.

After all, this question is only an episode (though an important one) in the great question of the origin of species, and whether you or I are right will not at all affect the main doctrine — that is one comfort.

I hope you will publish your treatise on Sexual Selection as a separate book as soon an possible, and then while you are going on with your other work, there will no [3] doubt be found someone to battle with me over your facts, on this hard problem.

With best wishes and kind regards to Mrs. Darwin and all your family, believe me, dear Darwin, yours very faithfully, ALFRED R. WALLACE.