n this work, yet I record in
my diary that about two years out of this time was lost by illness. On
this account I went in 1848 for some months to Malvern for hydropathic
treatment, which did me much good, so that on my return home I was able
to resume work. So much was I out of health that when my dear father
died on November 13th, 1848, I was unable to attend his funeral or to
act as one of his executors.

My work on the Cirripedia possesses, I think, considerable value, as
besides describing several new and remarkable forms, I made out the
homologies of the various parts--I discovered the cementing apparatus,
though I blundered dreadfully about the cement glands--and lastly I
proved the existence in certain genera of minute males complemental to
and parasitic on the hermaphrodites. This latter discovery has at last
been fully confirmed; though at one time a German writer was pleased to
attribute the whole account to my fertile imagination. The Cirripedes
form a highly varying and difficult group of species to class; and my
work was of considerable use to me, when I had to discuss in the 'Origin
of Species' the principles of a natural classification. Nevertheless, I
doubt whether the work was worth the consumption of so much time.

From September 1854 I devoted my whole time to arranging my huge
pile of notes, to observing, and to experimenting in relation to the
transmutation of species. During the voyage of the "Beagle" I had been
deeply impressed by discovering in the Pampean formation great fossil
animals covered with armour like that on the existing armadillos;
secondly, by the manner in which closely allied animals replace one
another in proceeding southwards over the Continent; and thirdly, by
the South American character of most of the productions of the Galapagos
archipelago, and more especially by the manner in which they differ
slightly on each island of the group; none of the islands appearing to
be very ancient in a geological sense.

It was evident that such facts as these, as well as many others, could
only be explained on the supposition that species gradually become
modified; and the subject haunted me. But it was equally evident that
neither the action of the surrounding conditions, nor the will of the
organisms (especially in the case of plants) could account for the
innumerable cases in which organisms of every kind are beautifully
adapted to their habits of life--for instance, a woodpecker or a