_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.
CLASS I. GREGARINIDAE.**
CLASS II. RHIZOPODA.
_Order_ 1. _Monera_.**
" 2. _Amoebea_.**
" 3. _Foraminifera_.
" 4. _Radiolaria_ (Polycystines, &c.
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