and the more general exposition of the subject by the author of the
_Vestiges of Creation_, the first step had not been taken towards a
satisfactory explanation of the derivation of any one species from any
other. Such eminent naturalists as Geoffroy Saint Hilaire, Dean Herbert,
Professor Grant, Von Buch, and some others, had expressed their belief
that species arose as simple varieties, and that the species of each
genus were all descended from a common ancestor; but none of them gave a
clue as to the law or the method by which the change had been effected.
This was still "the great mystery." As to the further question--how far
this common descent could be carried; whether distinct families, such as
crows and thrushes, could possibly have descended from each other; or,
whether all birds, including such widely distinct types as wrens,
eagles, ostriches, and ducks, could all be the modified descendants of a
common ancestor; or, still further, whether mammalia, birds, reptiles,
and fishes, could all have had a common origin;--these questions had
hardly come up for discussion at all, for it was felt that, while the
very first step along the road of "transmutation of species" (as it was
then called) had not been made, it was quite useless to speculate as to
how far it might be possible to travel in the same direction, or where
the road would ultimately lead to.


_The Problem before Darwin_.

It is clear, then, that what was understood by the "origin" or the
"transmutation" of species before Darwin's work appeared, was the
comparatively simple question whether the allied species of each genus
had or had not been derived from one another and, remotely, from some
common ancestor, by the ordinary method of reproduction and by means of
laws and conditions still in action and capable of being thoroughly