in its place. Protoplasm consumes the oxygen and sets free the carbonic
acid. Both kinds of protoplasm do this, until exposed to the light; and
then a difference is observed; for under the influence of light, animal
protoplasm alone continues to act in this way, and vegetable protoplasm
begins at once to develop little green bodies or corpuscles in its
cells, and afterwards acts in a totally opposite way, taking the carbon
into its substance and giving off the oxygen.[1]


[Footnote 1: Certain _fungi_ seem to afford an exception to this. The
above is, I believe, true as a theoretical action of plants and animals
in protoplasmic form. But practically, in all higher developments of
either kind, other distinctions come into play; e.g., that plants can
make use of inorganic matter, gases, and water, and elaborate them into
organic matter. Animals cannot do this, they require more or less solid
food--always requiring "complex organic bodies which they ultimately
reduce to much simpler inorganic bodies. They are thus mediately or
immediately dependent on plants for their subsistence" (Nicholson,
"Zoology," 6th ed. p. 17). It is perhaps with reference to this that in
the Book of Genesis the Creator is represented as giving _plant_ life to
the service of man and animals--while nothing is said of the preying of
_Carnivora_ and _Insectivora_ on animal life.]

Not only then has each kind of protoplasm its own mysterious character
impressed on it, and is compelled to act in a certain way; but still
further, each particle of animal and vegetable protoplasm, when directed
into its _general_ course of development as _plant or animal_, will
again only obey a certain course of development in its own line.

But we must proceed a step further; for those who would believe in the