That all have been alike produced by 'descent with modification' from a few primitive types, the whole body of evidence clearly indicates; but while individual variation with Natural Selection is proved to be adequate for the production of the former, we have no proof and hardly any evidence that it is adequate to initiate those important divergences of type which characterise the latter." In this passage stress should be laid (as Mr. Wallace points out to us) on the word PROOF. He by no means asserts that the causes which have produced the species of a genus are inadequate to produce greater differences. His object is rather to urge the difference between proof and probability.)
LETTER 297. TO J.H. FABRE.
(297/1. A letter to M. Fabre is given in "Life and Letters," III., page 220, in which the suggestion is made of rotating the insect before a "homing" experiment occurs.)
Down, February 20th, 1880.
I thank you for your kind letter, and am delighted that you will try the experiment of rotation. It is very curious that such a belief should be held about cats in your country (297/2. M. Fabre had written from Serignan, Vaucluse: "Parmi la population des paysans de mon village, l'habitude est de faire tourner dans un sac le chat que l'on se propose de porter ailleurs, et dont on veut empecher le retour. J'ignore si cette pratique obtient du succes."), I never heard of anything of the kind in England. I was led, as I believe, to think of the experiment from having read in Wrangel's "Travels in Siberia" (297/3. Admiral Ferdinand Petrovich von Wrangell, "Le Nord de la Siberie, Voyage parmi les Peuplades de la Russie asiatique, etc." Paris, 1843.) of the wonderful power which the Samoyedes possess of keeping their direction in a fog whilst travelling in a tortuous line through broken ice. With respect to cats, I have seen an account that in Belgium there is a society which gives prizes to the cat which can soonest find its way home, and for this purpose they are carried to distant parts of the city.
Here would be a capital opportunity for trying rotation.
I am extremely glad to hear that your book will probably be translated into English.
P.S.--I shall be much pleased to hear the result of your experiments.
LETTER 298. TO J.H. FABRE. Down, January 21st, 1881.
I am much obliged for your very interesting letter. Your results appear to me highly important, as they eliminate one means by which animals might perhaps recognise direction; and this, from what has been said about savages, and from our own consciousness, seemed the most probable means. If you think it worth while, you can of course mention my name in relation to this subject.
Should you succeed in eliminating a sense of the magnetic currents of the earth, you would leave the field of investigation quite open. I suppose that even those who still believe that each species was separately created would admit that certain animals possess some sense by which they perceive direction, and which they use instinctively. On mentioning the subject to my son George, who is a mathematician and knows something about magnetism, he suggested making a very thin needle into a magnet; then breaking it into very short pieces, which would still be magnetic, and fastening one of these pieces with some cement on the thorax of the insect to be experimented on.
He believes that such a little magnet, from its close proximity to the nervous system of the insect, would affect it more than would the terrestrial currents.
I have received your essay on Halictus (298/1. "Sur les Moeurs et la Parthenogese des Halictes" ("Ann. Sc. Nat." IX., 1879-80).), which I am sure that I shall read with much interest.
LETTER 299. TO T.H. HUXLEY.
(299/1. On April 9th, 1880, Mr. Huxley lectured at the Royal Institution on "The Coming of Age of the Origin of Species." The lecture was published in "Nature" and in Huxley's "Collected Essays," Volume II., page 227. Darwin's letter to Huxley on the subject is given in "Life and Letters," III., page 240; in Huxley's reply of May 10th ("Life and Letters of T.H. Huxley," II., page 12) he writes: "I hope you do not imagine because I had nothing to say about 'Natural Selection' that I am at all weak of faith on that article...But the first thing seems to me to be to drive the fact of evolution into people's heads; when that is once safe, the rest will come easy.")
Down, May 11th, 1880.