t, to which the popular doubter is certain to appeal,
is an equally baseless ground of separation. For all the animals I
have above named are rooted and fixed, while many true plants of lower
grade are never rooted at all. The yeast plant, the _Algae_ that swarm
in our ponds, and the diatoms that crowd the waters, exemplify plants
that are as free as animals; and many of them, besides, in their young
state especially (e.g., the seaweeds), swim about freely in the water
as if they were roving animalcules. On the second count, also, science
gains the day; power of motion is no legitimate ground at all for
distinguishing one living being as an animal, while absence of
movement is similarly no reason for assuming that the fixed organism
must of necessity be a plant. Then comes the microscopic evidence.
What can this wonder glass do in the way of drawing boundary lines
betwixt the living worlds? The reply again is disappointing to the
doubter; for the microscope teaches us that the tissues of animals and
plants are built upon kindred lines. We meet with cells and fibers in
both. The cell is in each case the primitive expression of the whole
organism. Beyond cells and fibers we see the wonderful living
substance, _protoplasm_, which is alike to our senses in the two
kingdoms, although, indeed, differing much here and there in the
results of its work. On purely microscopic grounds, we cannot separate
animals from plants. There is no justification for rigidly assuming
that this is a plant or that an animal on account of anything the
microscope can disclose. A still more important point in connection
with this protoplasm question consists in the fact that as we go
backward to the beginnings of life, both in animals and plants, we
seem to approach nearer and nearer to an identity of substance which
baffles the microscope with all its powers of discernment. Every
animal and every plant begins existence as a mere speck of this living
jelly. The germ of each is a protoplasm particle, which, whatever
traces of structure it may exhibit, is practically unrecognizable as
being definitely animal or plant in respect of its nature. Later on,
as we know, the egg or germ shows traces of structure in the case of
the higher animals and plants; while even lowly forms of life exhibit
more or less characteristic phases when they reach their adult stage.
But, of life's beginnings, the microscope is as futile as a kind
scientific touchstone for dist