mpossible to conceive how the first rudiments of these could
have been of any use, and, if not of use they could not have been
preserved and further developed by natural selection.

Now, the first remark to be made on objections of this nature is, that
they are really outside the question of the origin of all existing
species from allied species not very far removed from them, which is all
that Darwin undertook to _prove_ by means of his theory. Organs and
structures such as those above mentioned all date back to a very remote
past, when the world and its inhabitants were both very different from
what they are now. To ask of a new theory that it shall reveal to us
exactly what took place in remote geological epochs, and how it took
place, is unreasonable. The most that should be asked is, that some
probable or possible mode of origination should be pointed out in some
at least of these difficult cases, and this Mr. Darwin has done. One or
two of these may be briefly given here, but the whole series should be
carefully read by any one who wishes to see how many curious facts and
observations have been required in order to elucidate them; whence we
may conclude that further knowledge will probably throw light on any
difficulties that still remain.[41]

In the case of the mammary glands Mr. Darwin remarks that it is admitted
that the ancestral mammals were allied to the marsupials. Now in the
very earliest mammals, almost before they really deserved that name, the
young may have been nourished by a fluid secreted by the interior
surface of the marsupial sack, as is believed to be the case with the
fish (Hippocampus) whose eggs are hatched within a somewhat similar
sack. This being the case, those individuals which secreted a more
nutritious fluid, and those whose young were able to obtain and swallow
a more constant supply by suction, would be more likely to live and come
to a healthy maturity, and would therefore be preserved by natural
selection.

In another case which has been adduced as one of special difficulty, a
more complete explanation is given. Soles, turbots, and other flatfish
are, as is well known, unsymmetrical. They live and move on their sides,
the under side being usually differently coloured from that which is
kept uppermost. Now the eyes of these fish are curiously distorted in
order that both eyes may be on the upper side, where alone they would be
of any use. It was objected by Mr. Mivart that a sudd