bands, rarely in compact well-defined bundles. The tissues have
generally not yet been moulded into compact masses of definite form.
There are as yet very few structures to which we can give the name
of organs. To form organs and group them in a body of compact
definite form was the work pre-eminently of worms. The material for
the building was ready, but the architecture of the bilateral animal
was not even sketched. And different worms were their own
architects, untrammelled by convention or heredity, hence they built
very different, sometimes almost fantastic, structures.

We must remember, too, the great age of this group. They are present
in highly modified forms in the very oldest palæozoic strata, and
probably therefore came into existence as the first traces of
continental areas were beginning to rise above the primeval ocean.
They are literally "older than the hills." They were exposed to a
host of rapidly changing conditions, very different in different
areas. This prepares us for the fact that the worms represent a
stage in animal life corresponding fairly well to the Tower of Babel
in biblical history. The animal kingdom seems almost to explode into
a host of fragments. Our genealogical tree fairly bristles with
branches, but the branches do not seem to form any regular whorls or
spirals. Few of them have developed into more than feeble growths.
They now contain generally but few species. Many of them are
largely or entirely parasitic, and in connection with this mode of
life have undergone modifications and degeneration which make it
exceedingly difficult to decipher their descent or relationships.

Four of these branches have reached great prominence in numbers and
importance. One or two others were formerly equally numerous and
have since become almost extinct; so the brachiopoda, which have