e showed how complete was the gradation between
many forms ranked as species, and how difficult it was to say what forms
should be classed as 'varieties' and what as 'species.'

But when he came to indicate a possible method by which one species
might be derived from another, he was less happy in his suggestions. He
recognised the value of the evidence derived from the study of the races
which have arisen among domestic animals, and from the crossing of
different forms. But his main argument was derived from the acknowledged
fact that use or disuse may cause the development or the partial atrophy
of organs--the case of the 'blacksmith's arm.' Unfortunately some of the
suggestions made by Lamarck, in this connexion--like that of the
elongation of the giraffe's neck to enable it to browse on high
trees--were of a kind that made them very susceptible to ridicule. His
theory was of course dependent on the admission that acquired characters
were transmitted from parents to children, and in the absence of any
suggestion of 'selection,' it did not appeal strongly to thinkers on
this question.

Lyell first became acquainted with the writings of Lamarck in 1827. As
he was returning from the Oxford circuit for the last time--having now
resolved to give up law and devote himself to geological work
exclusively--he wrote to his friend Mantell as follows:--

'I devoured Lamarck _en voyage_.... His theories delighted me
more than any novel I ever read, and much in the same way, for
they address themselves to the imagination, at least of
geologists who know the mighty inferences which would be
deducible were they established by observations. But though I
admire even his flights, and feel none of the _odium
theologicum_ which some modern writers in this country have
visited him with, I confess I read him rather as I hear an
advocate on the wrong side, to know what can be made of the case
in good hands. I am glad he has been courageous enough and
logical enough to admit that his argument, if pushed as far as
it must go, if worth anything, would prove that men may have
come from the Ourang-Outang. But after all, what changes species
may really undergo! How impossible will it be to distinguish and
lay down a line, beyond which some of the so-called extinct
species have never passed into recent ones. That the earth is
quite as old as he supposes, has long been my creed,