My dear Dr. Gunther, Sincere thanks. Your answers are wonderfully clear and complete. I have some analogous questions on reptiles, etc., which I will send in a few days, and then I think I shall cause no more trouble. I will get the books you refer me to. The case of the Solenostoma (In most of the Lophobranchii the male has a marsupial sack in which the eggs are hatched, and in these species the male is slightly brighter coloured than the female. But in Solenostoma the female is the hatcher, and is also the more brightly coloured.--'Descent of Man,' ii. 21.) is magnificent, so exactly analogous to that of those birds in which the female is the more gay, but ten times better for me, as she is the incubator. As I crawl on with the successive classes I am astonished to find how similar the rules are about the nuptial or "wedding dress" of all animals. The subject has begun to interest me in an extraordinary degree; but I must try not to fall into my common error of being too speculative. But a drunkard might as well say he would drink a little and not too much! My essay, as far as fishes, batrachians and reptiles are concerned, will be in fact yours, only written by me. With hearty thanks.
Yours very sincerely, CH. DARWIN.
[The following letter is of interest, as showing the excessive care and pains which my father took in forming his opinion on a difficult point:]
CHARLES DARWIN TO A.R. WALLACE.
Down, September 23 [undated].
My dear Wallace, I am very much obliged for all your trouble in writing me your long letter, which I will keep by me and ponder over. To answer it would require at least 200 folio pages! If you could see how often I have re-written some pages you would know how anxious I am to arrive as near as I can to the truth. I lay great stress on what I know takes place under domestication;I think we start with different fundamental notions on inheritance. I find it is most difficult, but not I think impossible, to see how, for instance, a few red feathers appearing on the head of a male bird, and which ARE ATFIRST TRANSMITTED TO BOTH SEXES, could come to be transmitted to males alone. It is not enough that females should be produced from the males with red feathers, which should be destitute of red feathers; but these females must have a LATENT TENDENCY to produce such feathers, otherwise they would cause deterioration in the red head-feathers of their male offspring. Such latent tendency would be shown by their producing the red feathers when old, or diseased in their ovaria. But I have no difficulty in ****** the whole head red if the few red feathers in the male from the first tended to be sexually transmitted. I am quite willing to admit that the female may have been modified, either at the same time or subsequently, for protection by the accumulation of variations limited in their transmission to the female ***. I owe to your writings the consideration of this latter point. But I cannot yet persuade myself that females ALONEhave often been modified for protection. Should you grudge the trouble briefly to tell me whether you believe that the plainer head and less bright colours of a female chaffinch, the less red on the head and less clean colours of the female goldfinch, the much less red on the breast of the female bull-finch, the paler crest of golden-crested wren, etc., have been acquired by them for protection. I cannot think so any more than Ican that the considerable differences between female and male house sparrow, or much greater brightness of the male Parus coeruleus (both of which build under cover) than of the female Parus, are related to protection. I even mis-doubt much whether the less blackness of the female blackbird is for protection.
Again, can you give me reasons for believing that the moderate differences between the female pheasant, the female Gallus bankiva, the female black grouse, the pea-hen, the female partridge, [and their respective males,] have all special references to protection under slightly different conditions? I, of course, admit that they are all protected by dull colours, derived, as I think, from some dull-ground progenitor; and Iaccount partly for their difference by partial transference of colour from the male and by other means too long to specify; but I earnestly wish to see reason to believe that each is specially adapted for concealment to its environment.
I grieve to differ from you, and it actually terrifies me and makes me constantly distrust myself. I fear we shall never quite understand each other. I value the cases of bright-coloured, incubating male fishes, and brilliant female butterflies, solely as showing that one *** may be made brilliant without any necessary transference of beauty to the other ***;for in these cases I cannot suppose that beauty in the other *** was checked by selection.
I fear this letter will trouble you to read it. A very short answer about your belief in regard to the female finches and gallinaceae would suffice.
Believe me, my dear Wallace, Yours very sincerely, CH. DARWIN.
CHARLES DARWIN TO J.D. HOOKER.
Down, May 25 [1870].
...Last Friday we all went to the Bull Hotel at Cambridge to see the boys, and for a little rest and enjoyment. The backs of the Colleges are simply paradisaical. On Monday I saw Sedgwick, who was most cordial and kind; in the morning I thought his brain was enfeebled; in the evening he was brilliant and quite himself. His affection and kindness charmed us all.