a possible ancestor. The _Hippuritidoe_
of the Cretaceous burst into a varied life to all appearance
almost immediately after their first introduction into existence.
The wonderful Dicotyledonous flora of the Upper Cretaceous period
similarly surprises us without any prophetic annunciation from
the older Jurassic.

Many other instances could be given; but enough has been said
to show that there is a good deal to be said on both sides, and
that the problem is one environed with profound difficulties.
One point only seems now to be universally conceded, and that
is, that the record of life in past time is not interrupted by
gaps other than those due to the necessary imperfections of the
fossiliferous series, to the fact that many animals are incapable
of preservation in a fossil condition, or to other causes of a
like nature. All those who are entitled to speak on this head
are agreed that the introduction of new and the destruction of
old species have been slow and gradual processes, in no sense of
the term "catastrophistic." Most are also willing to admit that
"Evolution" has taken place in the past, to a greater or less
extent, and that a greater or less number of so-called species of
fossil animals are really the modified descendants of pre-existent
forms. _How_ this process of evolution has been effected, to what
extent it has taken place, under what conditions and laws it has
been carried out, and how far it may be regarded as merely auxiliary
and supplemental to some deeper law of change and progress, are
questions to which, in spite of the brilliant generalisations
of Darwin, no satisfactory answer can as yet be given. In the
successful solution of this problem--if soluble with the materials
available to our hands--will lie the greatest triumph that
Palaeontology can hope to attain; and there is reason to think
that, thanks to the guiding-clue afforded by the genius of the
author of the 'Origin of Species,' we are at least on the road
to a sure, though it may be a far-distant, victory.

APPENDIX.

TABULAR VIEW OF THE CHIEF DIVISIONS OF THE ANIMAL KINGDOM.

(Extinct groups are marked with an asterisk. Groups not represented
at all as fossils are marked with two asterisks.)

INVERTEBRATE ANIMALS.

SUB-KINGDOM I.--PROTOZOA.

Animal simple or compound; body composed of "sarcode," not definitely
segmented; no nervous system; and no digestive apparatus, beyond
occasionally a mouth and gullet.

CLAS