a true mollusc (VERMETUS) so far departs from the fashion prevalent in
the molluscan world of building a spiral shell, that after beginning one
in proper spiral mode it elongates itself in vermiform manner and forms
an irregular serpuloid tube on the surface of larger shells or stones
just as the SERPULA does; so that without examination of the animal one
may easily be mistaken for the other.

What a contrast is here--on the one hand a lowly worm learning to build a
solid if rude shelly covering for its tender body, on the other a
relative of the elegant, many-whorled TURRITELLA forgetting its high
station and degenerating to the likeness of a worm. No doubt it is really
a case of degeneration from the acquirement of fixed habits, just as when
a lively young crustacean larva gives up its free independent life and
glues its head to a stone--what happens? Why, he becomes a mere barnacle
instead of a spritely shrimp as he might have been! Let mankind take
note and beware.

Another group of worm-like or snaky creatures common on a coral-reef are
the sea-cucumbers or beche-de-mer. In my experience the most singular
branch of the family is at once the longest and thinnest, for it
resembles a snake so closely that at first sight the observer
subconsciously assumes an attitude of hostility. There seem to be two
varieties of the species. One is much more ruddy in appearance than the
other, and its body is the smoother; but they are much alike in physique
and helplessness. The figure of a sausage-skin four or five and even six
feet long, and capable of elongation to almost double, containing muddy
water in circulation and one end exhibiting a set of ever-waving
tentacles, conveys a not unflattering notion of the animal as it lies
coiled among the coral, half hidden with algae. Far too feeble to be
offensive, it suffers collapse on alarm--that is to say, if such a violent