absorbed in the construction of a tenement which has no time! Does the
inmate possess any sense of duration? Addison (quoting a French
authority) says that it is possible some creatures may think half an hour
as long as we do a thousand years! The magnificent mind of the modern
biologist regards a million of years as a mere fag-end of time. The
industrious worm which has built so choice a home may have enjoyed the
sense of comfort and security for a period representing an honourable
age, while, according to the standards of man, the home was not worth the
building for so short a tenancy.

Do we not see in this astonishing example a highly successful effort of a
marine worm to improve on the condition and habits of its barbarous
ancestors? Analyse a bulk sample of the building material, and you shall
find it not dissimilar from the shell of a mollusc, and the interior
film--no doubt a secretion of the animal--is to be safely accepted as
analogous to the silky smoothness which molluscs (often of rough and
rugged exterior) obtain by nacreous deposit and which finds its
culmination in the goldlip mother-of-pearl?

Still higher in the series, so far as the construction of a tenement is
concerned, is that known as the SERPULA, a worm which constructs a
calcareous tube more or less loosely convoluted and adherent to a shell
or stone or coral, or sometimes entwined into a self-supporting colony.

Another worm builds of sand or mud, with a rough casting of fine gravel
and shell-grit, a habitation similar in design to that of the serpula,
though on a less complete and authoritative model; indeed, it would
almost seem that the latter had designed its tenement after the fashion
of that of its poor relation--that the one made a study in mud which the
other reproduced in carbonate of lime. But the most curious fact is that