me organs, in another group or section of a
group, are found to differ much, we at once value them less in our
classification. We shall presently see why embryological characters are
of such high classificatory importance. Geographical distribution
may sometimes be brought usefully into play in classing large genera,
because all the species of the same genus, inhabiting any distinct and
isolated region, are in all probability descended from the same parents.

ANALOGICAL RESEMBLANCES.

We can understand, on the above views, the very important distinction
between real affinities and analogical or adaptive resemblances. Lamarck
first called attention to this subject, and he has been ably followed by
Macleay and others. The resemblance in the shape of the body and in the
fin-like anterior limbs between dugongs and whales, and between these
two orders of mammals and fishes, are analogical. So is the resemblance
between a mouse and a shrew-mouse (Sorex), which belong to different
orders; and the still closer resemblance, insisted on by Mr. Mivart,
between the mouse and a small marsupial animal (Antechinus) of
Australia. These latter resemblances may be accounted for, as it seems
to me, by adaptation for similarly active movements through thickets and
herbage, together with concealment from enemies.

Among insects there are innumerable instances; thus Linnaeus, misled by
external appearances, actually classed an homopterous insect as a moth.
We see something of the same kind even with our domestic varieties, as
in the strikingly similar shape of the body in the improved breeds of
the Chinese and common pig, which are descended from distinct species;
and in the similarly thickened stems of the common and specifically
distinct Swedish turnip. The resemblance between the greyhound and
race-horse is hardly more fanciful than the analogies which have been
drawn by some authors between widely different animals.

On the view of characters being of real importance for classification,
only in so far as they reveal descent, we can clearly understand why
analogical or adaptive characters, although of the utmost importance to
the welfare of the being, are almost valueless to the systematist.
For animals, belonging to two most distinct lines of descent, may have
become adapted to similar conditions, and thus have assumed a close
external resemblance; but such resemblances will not reveal--will rather
tend to conceal their blood-relation