read July 1, 1858, by Mr. Wallace and myself, in which, as stated in the
introductory remarks to this volume, the theory of Natural Selection is
promulgated by Mr. Wallace with admirable force and clearness.

Von Baer, toward whom all zoologists feel so profound a respect, expressed
about the year 1859 (see Prof. Rudolph Wagner, "Zoologisch-Anthropologische
Untersuchungen", 1861, s. 51) his conviction, chiefly grounded on the laws
of geographical distribution, that forms now perfectly distinct have
descended from a single parent-form.

In June, 1859, Professor Huxley gave a lecture before the Royal Institution
on the "Persistent Types of Animal Life". Referring to such cases, he
remarks, "It is difficult to comprehend the meaning of such facts as these,
if we suppose that each species of animal and plant, or each great type of
organisation, was formed and placed upon the surface of the globe at long
intervals by a distinct act of creative power; and it is well to recollect
that such an assumption is as unsupported by tradition or revelation as it
is opposed to the general analogy of nature. If, on the other hand, we
view "Persistent Types" in relation to that hypothesis which supposes the
species living at any time to be the result of the gradual modification of
pre-existing species, a hypothesis which, though unproven, and sadly
damaged by some of its supporters, is yet the only one to which physiology
lends any countenance; their existence would seem to show that the amount
of modification which living beings have undergone during geological time
is but very small in relation to the whole series of changes which they
have suffered."

In December, 1859, Dr. Hooker published his "Introduction to the Australian
Flora". In the first part of this great work he admits the truth of the
descent and modification of species, and supports this doctrine by many