adapted. Each species had only one beginning in a single stock: probably
a single pair, as Linnaeus supposed, was first called into being in some
particular spot, and the progeny left to disperse themselves to as great a
distance from the original centre of their existence as the locomotive
powers bestowed on them, or their capability of bearing changes of climate
and other physical agencies, may have enabled them to wander." (14/9.
Prichard, third edition, 1836-7, Volume I., page 96.)

The second passage is annotated by Mr. Darwin with a shower of exclamation
marks:

"The meaning attached to the term SPECIES in natural history is very
definite and intelligible. It includes only the following conditions--
namely, separate origin and distinctness of race, evinced by the constant
transmission of some characteristic peculiarity of organisation. A race of
animals or of plants marked by any peculiar character which has always been
constant and undeviating constitutes a species; and two races are
considered as specifically different, if they are distinguished from each
other by some characteristic which one cannot be supposed to have acquired,
or the other to have lost through any known operation of physical causes;
for we are hence led to conclude that the tribes thus distinguished have
not descended from the same original stock." (14/10. Prichard, ed. 1836-
7, Volume I., page 106. This passage is almost identical with that quoted
from the second edition, Volume I., page 90. The latter part, from "and
two races...," occurs in the second edition, though not quoted above.)

As was his custom, Mr. Darwin pinned at the end of the first volume of the
1841-51 edition a piece of paper containing a list of the pages where
marked passages occur. This paper bears, written in pencil, "How like my
book all this will be!" The words appear to refer to Prichard's discussion