star-fish, etc.,
which possess a thick, hard skin, covered by spines or prickly
projections. These creatures abound in numerous species. The star-fish
has rays projecting from a common centre, which gives it its name,
while the sea-urchin resembles a ball. The sea-lilies, with their stems
and flowers (so-called) belong to this family, as do also the
sea-cucumbers, whose name is obtained from their shape and general
appearance, but which are animals possessing a comparatively complex
organism, one of the features of which is a stomach which may be
discarded at will and replaced by a new one. These creatures have a
well defined nervous system, and have eyes, and some of them even
rudimentary eyelids.

Ascending the scale of life-forms, we next observe the great family of
the _Annulosa_, or jointed creatures, which comprises the various
families of the worm, the crab, the spider, the ant, etc. In this great
family are grouped nearly four-fifths of the known life-forms. Their
bodies are well formed and they have nervous systems running along the
body and consisting of two thin threads, knotted at different points
into ganglia or masses of nerve cells similar to those possessed by the
higher animals. They possess eyes and other sense organs, in some cases
highly developed. They possess organs, corresponding to the heart, and
have a well-developed digestive apparatus. Note this advance in the
nutritive organism: the _moneron_ takes its food at any point of its
body; the _amoeba_ takes its food by means of its "false-feet," and
drives it through its body by a rhythmic movement of its substance; the
_polyp_ distributes its food to its various parts by means of the water
which it absorbs with the food; the _sea-urchin and star-fish_
distribute their food by canals in their bodies which open directly
into the water; in the higher forms of the _annulosa_, the food is
distributed by a fluid resembling blood, which carries the nourishment
to every part and organ, and which carries away the waste matter, the
blood being propelled through the body by a rudimentary heart. The
oxygen is distributed by each of these forms in a corresponding way,
the higher forms having rudimentary lungs and respiratory organs. Step
by step the life-forms are perfected, and the organs necessary to
perform certain definite functions are evolved from rudimentary to
perfected forms.

The families of worms are the humblest members of the great family of
th