d and enigmatic, and explains many
things which are thus far utterly inexplicable upon any other scientific
assumption.

We have said (p. 116) that Darwin's hypothesis is the natural complement
to Lyell's uniformitarian theory in physical geology. It is for the
organic world what that popular view is for the inorganic; and the
accepters of the latter stand in a position from which to regard the
former in the most favorable light. Wherefore the rumor that the
cautious Lyell himself has adopted the Darwinian hypothesis need not
surprise us. The two views are made for each other, and, like the two
counterpart pictures for the stereoscope, when brought together, combine
into one apparently solid whole.

If we allow, with Pictet, that Darwin's theory will very well serve for
all that concerns the present epoch of the world's history,--an epoch
which this renowned palaeontologist regards as including the diluvial or
quaternary period,--then Darwin's first and foremost need in his onward
course is a practicable road from this into and through the tertiary
period, the intervening region between the comparatively near and the
far remote past. Here Lyell's doctrine paves the way, by showing that in
the physical geology there is no general or absolute break between the
two, probably no greater between the latest tertiary and the quaternary
period than between the latter and the present time. So far, the
Lyellian view is, we suppose, generally concurred in. Now as to the
organic world, it is largely admitted that numerous tertiary species
have continued down into the quaternary, and many of them to the present
time. A goodly percentage of the earlier and nearly half of the later
tertiary mollusca, according to Des Hayes, Lyell, and, if we mistake
not, Bronn, still live. This identification, however, is now questioned
by a naturalist of the very highest authority. But, in its bearings on
the new theory, the point here turns not upon absolute identity so
much as upon close resemblance. For those who, with Agassiz, doubt the
specific identity in any of these cases, and those who say, with Pictet,
that "the later tertiary deposits contain in general the _debris_ of
species _very nearly related_ to those which still exist, belonging to
the same genera, but specifically different," may also agree with Pictet
that the nearly related species of successive faunas must or may have
had "a material connection." Now the only material connectio