abitants of the archipelago now range
thousands of miles beyond its confines; and analogy leads me to believe
that it would be chiefly these far-ranging species which would oftenest
produce new varieties; and the varieties would at first generally
be local or confined to one place, but if possessed of any decided
advantage, or when further modified and improved, they would slowly
spread and supplant their parent-forms. When such varieties returned to
their ancient homes, as they would differ from their former state, in
a nearly uniform, though perhaps extremely slight degree, they would,
according to the principles followed by many palaeontologists, be ranked
as new and distinct species.

If then, there be some degree of truth in these remarks, we have no
right to expect to find in our geological formations, an infinite number
of those fine transitional forms, which on my theory assuredly have
connected all the past and present species of the same group into one
long and branching chain of life. We ought only to look for a few links,
some more closely, some more distantly related to each other; and these
links, let them be ever so close, if found in different stages of the
same formation, would, by most palaeontologists, be ranked as distinct
species. But I do not pretend that I should ever have suspected how poor
a record of the mutations of life, the best preserved geological section
presented, had not the difficulty of our not discovering innumerable
transitional links between the species which appeared at the
commencement and close of each formation, pressed so hardly on my
theory.

ON THE SUDDEN APPEARANCE OF WHOLE GROUPS OF ALLIED SPECIES.

The abrupt manner in which whole groups of species suddenly appear in
certain formations, has been urged by several palaeontologists,
for instance, by Agassiz, Pictet, and by none more forcibly than
by Professor Sedgwick, as a fatal objection to the belief in the
transmutation of species. If numerous species, belonging to the same
genera or families, have really started into life all at once, the fact
would be fatal to the theory of descent with slow modification through
natural selection. For the development of a group of forms, all of which
have descended from some one progenitor, must have been an extremely
slow process; and the progenitors must have lived long ages before their
modified descendants. But we continually over-rate the perfection of the
geological record, an