The original protoplasm, when dead, is undistinguishable by the eye, by
chemical test, or by the microscope, from the same protoplasm when
living; and living protoplasm, again, may be either animal or vegetable.
Both are in every respect (externally) absolutely identical. Yet the one
will only develop into a _plant_, the other only into an _animal._ Nor
does it diminish the significance of the fact to say that the
differentiation is _now_ fixed by heredity. If we suppose protoplasm to
be only a fortuitous combination of elements, what secondary or common
natural cause will account for its acquisition of the fixed difference?
It is true that some forms of plants exhibit some functions that closely
approach the functions of what we call animal life; but, as we shall see
presently, there is no evidence whatever that there is any bridge
between the two--we have no proof that a plant ever develops into an
animal. Here is one of the gaps which the theory of Evolution, true as
it is to a certain extent, cannot bridge over; and we must not overlook
the fact. We shall revert to it hereafter.

Can it be believed, then, that protoplasm, as the origin of life, is
self-caused, and self-developed? And this is not all. I must briefly
remind my readers that the way in which animal protoplasm deals with the
elements of nutrition is quite opposite to that which plant protoplasm
follows. I might, indeed, have mentioned this at an earlier stage, when
I mentioned Professor Huxley's comparison of the chemical action in the
formation of water with what he assumed to be the case in the formation
of protoplasm. When water is formed, the two gases disappear, and an
_exactly equal weight_ of water appears in their place; but if living
protoplasm is enabled to imbibe liquid or other nutriment containing
ammonia, water, and carbonic acid, there is no disappearance of the
three elements and an equivalent weight of living protoplasm appearing