exteriorly almost smooth. One was found which filled up not only
the whole gland, as is often the case, but its neck; so that it
resembled an olive-oil flask in shape. These concretions when
broken are seen to be more or less crystalline in structure. How
they escape from the gland is a marvel; but that they do escape is
certain, for they are often found in the gizzard, intestines, and
in the castings of worms, both with those kept in confinement and
those in a state of nature.

Claparede says very little about the structure of the two anterior
glands, and he supposes that the calcareous matter of which the
concretions are formed is derived from the four posterior glands.
But if an anterior gland which contains only small concretions is
placed in acetic acid and afterwards dissected, or if sections are
made of such a gland without being treated with acid, lamellae like
those in the posterior glands and coated with cellular matter could
be plainly seen, together with a multitude of free calciferous
cells readily soluble in acetic acid. When a gland is completely
filled with a single large concretion, there are no free cells, as
these have been all consumed in forming the concretion. But if
such a concretion, or one of only moderately large size, is
dissolved in acid, much membranous matter is left, which appears to
consist of the remains of the formerly active lamellae. After the
formation and expulsion of a large concretion, new lamellae must be
developed in some manner. In one section made by my son, the
process had apparently commenced, although the gland contained two
rather large concretions, for near the walls several cylindrical
and oval pipes were intersected, which were lined with cellular
matter and were quite filled with free calciferous cells. A great
enlargement in one direction of several oval pipes would give rise