, assumes no special tendency of
organisms to give rise to useful varieties, and knows nothing of
needs of development, or necessity of perfection. What he says is, in
substance: All organisms vary. It is in the highest degree improbable
that any given variety should have exactly the same relations to
surrounding conditions as the parent stock. In that case it is either
better fitted (when the variation may be called useful), or worse
fitted, to cope with them. If better, it will tend to supplant the
parent stock; if worse, it will tend to be extinguished by the parent
stock.

If (as is hardly conceivable) the new variety is so perfectly adapted
to the conditions that no improvement upon it is possible,--it will
persist, because, though it does not cease to vary, the varieties will
be inferior to itself.

If, as is more probable, the new variety is by no means perfectly
adapted to its conditions, but only fairly well adapted to them, it will
persist, so long as none of the varieties which it throws off are better
adapted than itself.

On the other hand, as soon as it varies in a useful way, i.e. when the
variation is such as to adapt it more perfectly to its conditions, the
fresh variety will tend to supplant the former.

So far from a gradual progress towards perfection forming any necessary
part of the Darwinian creed, it appears to us that it is perfectly
consistent with indefinite persistence in one estate, or with a gradual
retrogression. Suppose, for example, a return of the glacial epoch and a
spread of polar climatal conditions over the whole globe. The operation
of natural selection under these circumstances would tend, on the whole,
to the weeding out of the higher organisms and the cherishing of the
lower forms of life. Cryptogamic vegetation would have the advantage
over Phanerogamic; Hydrozoa over Corals; Crustacea over Insecta, and
Amphipoda and Isopoda over the higher Crustacea; Cetaceans and Seals
over the Primates; the civilization of the Esquimaux over that of the
European.

"5. Pelzeln has also objected that if the later organisms have proceeded
from the earlier, the whole developmental series, from the simplest to
the highest, could not now exist; in such a case the simpler organisms
must have disappeared."

To this Professor Kolliker replies, with perfect justice, that the
conclusion drawn by Pelzeln does not really follow from Darwin's
premisses, and that, if we take the facts of Palaeontol