t the
length in belief to which you go, and not at all surprised at the
prudent reservations which you make. I remember well how many years it
cost me to go round from old beliefs. It is encouraging to me to observe
that everyone who has gone an inch with me, after a period goes a few
more inches or even feet. But the great point, as it seems to me, is to
give up the immutability of specific forms; as long as they are thought
immutable, there can be no real progress in "Epiontology." (160/3. See
De Candolle, loc. cit., page 67: he defines "Epiontologie" as the study
of the distribution and succession of organised beings from their origin
up to the present time. At present Epiontology is divided into geography
and palaeontology, "mais cette division trop inegale et a limites bien
vagues disparaitra probablement.") It matters very little to any one
except myself, whether I am a little more or less wrong on this or that
point; in fact, I am sure to be proved wrong in many points. But the
subject will have, I am convinced, a grand future. Considering that
birds are the most isolated group in the animal kingdom, what a splendid
case is this Solenhofen bird-creature with its long tail and fingers to
its wings! I have lately been daily and hourly using and quoting your
"Geographical Botany" in my book on "Variation under Domestication."

LETTER 161. TO HORACE DOBELL. Down, February 16th [1863].

Absence from home and consequent idleness are the causes that I have not
sooner thanked you for your very kind present of your Lectures. (161/1.
"On the Germs and Vestiges of Disease," (London) 1861.) Your reasoning
seems quite satisfactory (though the subject is rather beyond my limit
of thought and knowledge) on the V.M.F. not being "a given quantity."
(161/2. "It has been too common to consider the force exhibited in
the operations of life (the V.M.F.) as a given quantity, to which no
accessions can be made, but which is apportioned to each living being in
quantity sufficient for its necessities, according to some hidden law"
(op. cit., page 41.) And I can see that the conditions of life must play
a most important part in allowing this quantity to increase, as in the
budding of a tree, etc. How far these conditions act on "the forms of
organic life" (page 46) I do not see clearly. In fact, no part of my
subject has so completely puzzled me as to determine what effect to
attribute to (what I vaguely call) the direct action of the c