od of
growth. The cell grows by material taken into its substance, as food.
When sufficient food has been partaken, and enough new material
accumulated to cause the cell to attain a certain size, then it
divides, or separates into two cells, the division being equal, and the
point of cleavage being at the kernel or nucleus. As the two parts
separate, the protoplasm _of_ each groups itself around its nucleus,
and two living forms exist where there was but one a moment before. And
then each of the two cells proceed to grow rapidly, and then separate,
and so on to the end, each cell multiplying into millions, as time
passes.

Ascending in the scale, we next find the living forms composed of
cell-groups. These cell-groups are formed by single cells dividing, and
then subdividing, but instead of passing on their way they group
themselves in clusters, or masses. There are millions of forms of these
cell-group creatures, among which we find the sponges, polyps, etc.

In the early forms of life it is difficult to distinguish between the
animal and the plant forms, in fact the early forms partake of the
qualities of both. But as we advance in the scale a little there is
seen a decided "branching out," and one large branch is formed of the
evolving plant forms, and the other of the evolving animal forms. The
plant-branch begins with the sea-weeds, and passes on to the fungi,
lichens, mosses, ferns, pines and palm-ferns, grasses, etc., then to
the trees, shrubs and herbs. The animal-branch begins with the
_monera_, or single-cell forms, which are little more than a drop of
sticky, glue-like protoplasm. Then it passes on to the _amoebae_, which
begins to show a slight difference in its parts. Then on the
_foraminifera_, which secretes a shell of lime from the water. Then on
a step higher to the _polycystina_, which secretes a shell, or skeleton
of flint-like material from the water. Then come the sponges. Then the
coral-animals, anemones and jelly-fish. Then come the sea-lilies,
star-fish, etc. Then the various families of worms. Then the crabs,
spiders, centipedes, insects. Then come the mollusca, which include the
oysters, clams and other shell-fish; snails, cuttle-fish, sea-squirts,
etc. All of the above families of animal-forms are what are known as
"invertebrates," that is, without a backbone.

Then we come to the "vertebrates," or animals having a backbone. First
we see the fish family with its thousands of forms. Then com