ntry, for all will have been
continually blended through free intercrossing.

By considering the embryological structure of man--the homologies
[parallels] which he presents with the lower animals--the rudiments
which he retains--and the reversions to which he is liable, we can
partly recall in imagination the former condition of our early
progenitors; and can approximately place them in their proper place in
the zoological series. We thus learn that man is descended from a hairy,
tailed quadruped, probably arboreal in its habits [living on or among
trees] and an inhabitant of the Old World. This creature, if its whole
structure had been examined by a naturalist, would have been classed
among the Quadrumana, as surely as the still more ancient progenitor of
the Old and New World monkeys. The Quadrumana and all the higher mammals
are probably derived from an ancient marsupial animal [usually provided
with a pouch for the reception and nourishment of the young, as in the
case of the kangaroo] and this through a long line of diversified forms,
from some reptile-like or some amphibian-like creature, and this again
from some fish-like animal. In the dim obscurity of the past we can see
that the early progenitor of all the Vertebrata must have been an
aquatic animal, provided with branchiae [gills], with the two sexes
united in the same individual, and with the most important organs of the
body (such as the brain and heart) imperfectly or not at all developed.
This animal seems to have been more like the larvae of the existing
marine Ascidians than any other known form.

The greatest difficulty which presents itself when we are driven to the
above conclusion on the origin of man is the high standard of
intellectual power and of moral disposition which he has attained. But
every one who admits the principle of evolution must see that the mental
powers of the higher animals, which are the same in kind with those of
man, though so different in degree, are capable of advancement. Thus the
interval between the mental powers of one of the higher apes and of a
fish, or between those of an ant and scale-insect, is immense; yet their
development does not offer any special difficulty; for with our
domesticated animals the mental faculties are certainly variable, and
the variations are inherited. No one doubts that they are of the utmost
importance to animals in a state of nature. Therefore, the conditions
are favourable for their deve