Continental and Island Life [pp. 1-29]

CONTINEN7'AL AND ISLAND LIFE.
of connecting links would not have occurred. Further, a new
difficulty would have sprung up in the geographical and geological relations of species and genera, which would then have
assumed too much of the aspect of a preconceived plan. It is
only fair to a well-known and somewhat extreme European evolutionist, Karl Vogt, to state that he launches boldly into the
ocean of multiple evolution, not fearing to hold that identical
species of mollusks have been separately evolved in separate
Swiss lakes, and that the horse has been separately evolved in
America and in Europe, in the former along a line beginning
with Eohippus, and in the latter along an entirely separate line
commencing with Paleotherium. The serious complications
resulting from such admissions are evident, but Vogt deserves
credit for faith and consistency beyond those of his teachers.
With reference to the actual distribution of species, the question of time becomes most important when applied to the glacial
period, since it is obvious that much of the present distribution
must have been caused or greatly modified by that event. The
astronomical theory would place the close of the glacial age
as far back as 70,00ooo or 80,0ooo years ago. But if we reject this
theory, we are not under this limitation as to time, and the geological evidence would lead to the conclusion that the glacial
period was much nearer to our own epoch. Croll himself has
shown that in Scotland the removal of material from the surface
since that period might be taken to indicate a much shorter
time. In Canada, the character of the river-courses cut through
the glacial beds, and their very unformed and imperfect excavations, would lead to the belief that only a few thousands of years
have elapsed since the glacial beds were laid down. The same
conclusion can be drawn from the good preservation of the glaciated surfaces and of the shells and bones found on the terraces.
Similar evidence is afforded by the rate of recession of coasts
and waterfalls, and by the condition of eskers and lake ridges.
If we adopt the shorter estimates afforded by these facts, it will
follow that the submergences and emergences of land in the
glacial age were more rapid than has hitherto been supposed,
and that this would react on our estimate of time by giving
facilities for more rapid denudation and deposition. Such re sults, would greatly shorten the duration assignable to the human
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