This class embraces those beings which are the lowest in the animal
kingdom--those which have the fewest and most imperfect senses. Indeed,
some of them so far resemble plants as to make the point of separation
between the animal and vegetable kingdoms almost a matter of
uncertainty. They are called _radiata_, because in most of them an
arrangement may be traced, in their formation, like that of rays
branching out from a centre. Among the creatures of this class are the
star-fish, polypus, sea-anemone, and infusoria.