in
the Stonesfield slate; though wood and herb-eating beetles,
grasshoppers, dragon-flies, and May-flies may be found beneath the lias,
and scorpions and cockroaches beneath the coal, though, also beneath the
coal, salamanders and Sauroid batrachians, of which the archegosaurus is
an example, may occur; though reptiles, as the telerpeton, may be found
deeper than the old red sandstone; yet the connexion between aerial
constitution and form of life will never be shaken. Still will remain
the facts that the geographical distribution of types was anterior to
the appearance of existing species, that organisms first appeared in a
liquid medium, primitively marine, then fluviatile, and at last
terrestrial; that Radiates, Molluscs, Articulates, Vertebrates, were all
at first aquatic, and that the Radiates have ever remained so; that the
plane of greatest vital activity has ever been the sea-level, where the
earth and air touch each other; that the order of individual development
is the order of mundane development. Still will remain the important
conclusions that the mammalian Fauna has diverged more rapidly than the
testaceous; that hot-blooded animals have not had that longevity of
species which has been displayed by the cold, just as we observe in the
individual the possibility of muscular contraction by a given galvanic
force lasts much longer in the latter than in the former; that if the
hot-blooded tribes have thus a briefer duration, they enjoy a
compensation in the greater energy of their life--perhaps this being the
cause and that the effect; that, notwithstanding the countless forms
exhibited by species, their duration is so great that they outlive vast
changes in the topographical configuration of countries--the Fauna of
some countries having been in existence before those countries
themselves; that the plan of individual development has ever been as it
is now, and that sameness of external influence produces similarity of
organization.

[Sidenote: The doctrine of catastrophes and uniformity.] In its early
history theoretical geology presented two schools--one insisting on a
doctrine of catastrophes, one on a doctrine of uniformity. The former
regarded those changes which have manifestly taken place in the history
of our planet as having occurred at epochs abruptly. To this doctrine
the prevailing impression that there had been providential interventions
lent much force. The other school, reposing on the great princ