k might conceivably be effected. He thinks that
the slowness of the action of Natural Selection really depends on the
slowness of the changes naturally occurring in the physical conditions,
etc.) (in which I hope I may be wrong), I have chiefly had in my mind
the effects of intercrossing. I subscribe to almost everything you say
excepting the last short sentence. (296/4. The passage in question is
as follows: "I have also attempted to show that the causes which have
produced the separate species of one genus, of one family, or perhaps of
one order, from a common ancestor, are not necessarily the same as those
which have produced the separate orders, classes, and sub-kingdoms
from more remote common ancestors. 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 thei