, instead of
enunciating it even as my opinion, that the place of lost
species is filled up (as it was of old) from time to time by new
species. I have only ventured to say that had new mammalia come
in, we could hardly have hoped to verify the fact[81].'

That Lyell was convinced of the truth of the doctrine of the evolution
of species is shown by his correspondence with friends and sympathisers
like Scrope and John Herschel. But he wrote:

'If I had stated ... the possibility of the introduction or
origination of fresh species being a natural, in
contradistinction to a miraculous process, I should have raised
a host of prejudices against me, which are unfortunately opposed
at every step to any philosopher who attempts to address the
public on these mysterious subjects[82].'

That Lyell was justified in not increasing the difficulties which would
retard the reception of his views, by introducing matter, which he still
regarded as of a more or less speculative character, I think everyone
will be prepared to admit. Darwin had to contend with the same
difficulty in writing the _Origin of Species_. To have included the
question of the origin of mankind _prominently_ in that work would have
raised an almost insurmountable barrier to its reception. He says in his
autobiography, 'I thought it best, in order that no honourable man
should accuse me of concealing my views, to add that by the work "light
would be thrown on the origin of man and his history." It would have
been useless and injurious to the success of the book to have paraded,
without giving evidence, my conviction with respect to his origin[83].'

Huxley and Haeckel have both borne testimony to the fact that Lyell, at
the time he wrote the _Principles_, was firmly convinced that new
species had originated by evolution from old ones. Indeed in a letter to
John Herschel in 1836 he goes very far in the direction of anticipating
the lines in which enquiries on the _method_ of evolution must proceed,
having even a prevision of the doctrine of _mimicry_, long afterwards
established by Bates and others. Lyell wrote:--

'In regard to the origination of new species, I am very glad to
find that you think it probable that it may be carried on
through the intervention of intermediate causes. I left this
rather to be inferred, not thinking it worth while to offend a
certain class of persons by embodying in words