inguishing animals from plants as is
power of movement, or shape, or form.

A fourth point of appeal in the matter is found within the domain of
the chemist. Chemistry, with its subtile powers of analysis, with its
many-sided possibilities of discovering the composition of things, and
with its ability to analyze for us even the light of the far distant
stars, only complicates the difficulties of the biologist. For, while
of old it was assumed that a particular element, nitrogen, was
peculiar to animals, and that carbon was an element peculiar to
plants, we now know that both elements are found in animals, just as
both occur in plants. The chemistry of living things, moreover, when
it did grow to become a staple part of science, revealed other and
greater anomalies than these. It showed that certain substances which
were supposed to be peculiar to plants, and to be made and
manufactured by them alone, were also found in animals. Chlorophyl is
the green coloring matter of plants, and is, of course, a typical
product of the vegetable world; yet it is made by such animals as the
hydra of the brooks and ponds, and by many animalcules and some worms.
Starch is surely a typical plant product, yet it is undoubtedly
manufactured, or at least stored up, by animals--a work illustrated by
the liver of man himself, which occasionally produces sugar out of its
starch.

Again, there is a substance called _cellulose_, found well nigh
universally in plants. Of this substance, which is akin to starch, the
walls or envelopes of the cells of plant tissues are composed. Yet we
find those curious animals, the sea squirts, found on rocks and stones
at low-water mark, manufacturing cellulose to form part and parcel of
the outer covering of their sac-like bodies. Here it is as if the
animal, like a dishonest manufacturer, had infringed the patent rights
of the plant. On the fourth count, then--that of chemical
composition--the verdict is that nothing that chemistry can teach us
may serve definitely, clearly, and exactly to set a boundary line or
to erect a partition wall between the two worlds of life. There yet
remains for us to consider a fifth head--that of the food.

In the matter of the feeding of the two great living worlds we might
perchance light upon some adequate grounds for making up the one
kingdom from the other. What the consideration of form, movement,
chemical composition, and microscopic structure could not effect for
us in