"The facts to which reference is here made were, without doubt, eminently fitted to attract the attention of a philosophical thinker; but until the relations of the existing with the extinct species and of the species of the different geographical areas, with one another were determined with some exactness, they afforded but an unsafe foundation for speculation.

It was not possible that this determination should have been effected before the return of the "Beagle" to England; and thus the date which Darwin (writing in 1837) assigns to the dawn of the new light which was rising in his mind becomes intelligible."-- From "Darwiniana," Essays by Thomas H.Huxley, London, 1893; pages 274-5.), so that in July, 1837, I opened a notebook to record any facts which might bear on the question; but I did not become convinced that species were mutable until, I think, two or three years had elapsed.

(278/2.

On this last point see page 38.) LETTER 279.

TO G.J.