king a cow for the grass it eats? These queries are,
of course, answerable in one way only. Unfortunately (for the
querists), however, they do not include or comprehend the whole
difficulty. They merely assert, what is perfectly true, that we are
able, without trouble, to mark off the higher animals from the higher
plants. What science inquires is, whether we are able to separate
_all_ animals from _all_ plants, and to fix a definite boundary line,
so as to say that all the organisms on the one side of the line are
assuredly animals, while all the others on the opposite side of the
line may be declared to be truly plants. It is exactly this task which
science declares to be among the impossibilities of knowledge. Away
down in the depths of existence and among the groundlings of life the
identity of living things becomes of a nature which is worse than
confusing, and which renders it a futile task to attempt to separate
the two worlds of life. The hopelessness of the task, indeed, has
struck some observers so forcibly that they have proposed to
constitute a third kingdom--the _Regnum Protisticum_--between the
animal and the plant worlds, for the reception of the host of doubtful
organisms. This third kingdom would resemble the casual ward of a
workhouse, in that it would receive the waifs and strays of life which
could not find a refuge anywhere else.

A very slight incursion into biological fields may serve to show forth
the difficulties of naturalists when the task of separating animals
from plants is mooted for discussion. To begin with, if we suppose our
popular disbeliever to assert that animals and plants are always to be
distinguished by shape and form, it is easy enough to show him that
here, as elsewhere, appearances are deceptive. What are we to say of a
sponge, or a sea anemone, of corals, of zoophytes growing rooted from
oyster shells, of sea squirts, and of sea mats? These, each and all of
them, are true animals, but they are so plant-like that, as a matter
of fact, they are often mistaken by seaside visitors for plants. This
last remark holds especially true of the zoophytes and the sea mats.
Then, on the other hand, we can point to hundreds of lower plants,
from the yeast plant onward, which show none of the ordinary features
of plant life at all. They possess neither roots, stems, branches,
leaves, nor flowers, so that on this first count of the indictment the
naturalist gains the day.

Power of movemen