882 Miscellaneous. 
inference is really true. Certainly it is not yet generally accepted ; 
but a strong current is setting towards its acceptance. 
So long as universal cataclysms were in vogue, and all life upon 
the earth was thought to have been suddenly destroyed and renewed 
many times in succession, such a view could not bethought of. So 
the equivalent view maintained by Agassiz, and formerly, we believe, 
by D’Orbigny, that, irrespective of general and sudden catastrophes, 
or any known adequate physical cause, there has been a total depo- 
pulation at the close of each geological period or formation, say forty 
or fifty times, or more, followed by as many independent great acts 
of creation, at which alone have species been originated, and at each 
of which a vegetable and an animal kingdom were produced entire 
and complete, full-fledged, as flourishing, as wide-spread and popu- 
lous, as varied and mutually adapted from the beginning as ever 
afterwards,—such a view of course supersedes all material connexion 
between successive species, and removes even the association and 
geographical range of species entirely out of the domain of physical 
causes and of natural science. This is the extreme opposite of Wal- 
lace’s and Darwin’s view, and is quite as hypothetical. The nearly 
universal opinion, if we rightly gather it, manifestly is, that the re- 
placemeut of the species of successive formations was not complete 
and simultaneous, but partial and successive, and that along the 
course of each epoch some species probably were introduced, and 
some, doubtless became extinct. If all since the Tertiary belongs to 
our present epoch, this is certainly true of it; if to two or more 
epochs, then the hypothesis of a total change is not true of them. 
Geology makes huge demands upon time; and we regret to find 
that it has exhausted ours,—that what we meant for the briefest and 
most general sketch of some geological considerations in favour of 
Darwin’s hypothesis has so extended as to leave no room for con- 
sidering ‘the great facts of comparative anatomy and zoology”’ with 
which Darwin’s theory “ very well accords,” nor for indicatng how 
‘it admirably serves for explaining the unity of composition of all 
organisms, the existence of representative and rudimentary organs, 
and the natural series which genera and species compose.” Suffice 
it to say that these are the real strongholds of the new system on its 
theoretical side; that it goes far towards explaining both the physio- 
logical and the structural gradations and relations between the two 
kingdoms, and the arrangement of all their forms in groups subordinate 
to groups, all within a few great types ; that it reads the riddle of abor- 
tive organs and of morphological conformity, of which no other theory 
has ever offered a scientific explanation, and supplies a ground for 
harmonizing the two fundamental ideas which naturalists and philo- 
sophers conceive to have ruled the organic world, though they could 
not reconcile them,—namely, Adaptation to Purpose and the Con- 
ditions of Existence, and Unity of Type. To reconcile these two 
undeniable principles is a capital problem in the philosophy of natural 
history; and the hypothesis which consistently does so thereby 
secures a great advantage. 
We all know that the arm and hand of a monkey, the fore leg and 
