rrassment of those who attempt to classify
and distinguish the new acquisitions, poured in such multitudes into our
museums, should increase with the augmentation of their number, is quite
natural; since to obviate this, it is not enough that our powers of
discrimination should keep pace with the increase of the objects, but we
ought to possess greater opportunities of studying each animal and plant
in all stages of its growth, and to know profoundly their history, their
habits, and physiological characters, throughout several generations;
for, in proportion as the series of known animals grows more complete
none can doubt there is a nearer approximation to a graduated scale of
being; and thus the most closely allied species will be found to possess
a greater number of characters in common.

_Causes of the difficulty of discriminating species._--But, in point of
fact, our new acquisitions consist, more and more as we advance, of
specimens brought from foreign and often very distant and barbarous
countries. A large proportion have never even been seen alive by
scientific inquirers. Instead of having specimens of the young, the
adult, and the aged individuals of each sex, and possessing means of
investigating the anatomical structure, the peculiar habits, and
instincts of each, what is usually the state of our information? A
single specimen, perhaps, of a dried plant, or a stuffed bird or
quadruped; a shell, without the soft parts of the animal; an insect in
one stage of its numerous transformations;--these are the scanty and
imperfect data which the naturalist possesses. Such information may
enable us to separate species which stand at a considerable distance
from each other; but we have no right to expect any thing but difficulty
and ambiguity, if we attempt, from such imperfect opportunities, to
obtain distinctive marks for defining the characters of species which
are closely related.

If Lamarck could introduce so much certainty and precision into the
classification of several thousand species of recent and fossil shells,
notwithstanding the extreme remoteness of the organization of these
animals from the type of those vertebrated species which are best known,
and in the absence of so many of the living inhabitants of shells, we
are led to form an exalted conception of the degree of exactness to
which specific distinctions are capable of being carried, rather than to
call in question their reality.

When our data a