uch expanded into the gland; thus quite removing a doubt which I had
sometimes felt, whether the ovarian tube was not simply attached to or
embedded in the gland, without any further connection. By dissection
the multiple external coats of the gland and ovarian tubes could be seen
to be continuous. The cellular contents of the tubes passed into the
more opaque cellular contents of the gland, by a layer of transparent,
pulpy, pale, yellowish substance. There appeared in several instances to
be a relation, between the state of fulness and condition of the
contents of the gland, and of the immediately adjoining portions of the
ovarian tubes. In one specimen of _Pollicipes mitella_ it was clear that
the altered, tough, yellow, transparent, non-cellular contents of the
two glands and ducts, had actually invaded for some little distance, the
two ovarian tubes which ran into them, thus showing the continuity of
the whole. From these facts I conclude, without hesitation, that the
gland itself is a part of an ovarian tube specially modified; and
further, that the cellular matter, which in the ovarian tubes serves for
the development of the ova, is, by the special action of the walls of
the gland, changed into the opaquer cellular matter in the ducts, and
this again subsequently into that tissue or substance, which cements the
Cirripede to its surface of attachment.

As the individuals grow and increase in size, so do the glands and
cement-ducts; but it seems often to happen, that when a specimen is
immovably attached, the cementing apparatus ceases to act, and the
cellular contents of the duct become converted into a thread of
transparent tough cement; the investing membrane, also, of the ducts, in
Conchoderma sometimes becomes hard and mamillated. I have already
alluded to the case of a Pollicipes, in which both glands and ducts, and
even a small portion of the two adjoining ovarian tubes, had become thus
filled up. As in sessile Cirripedes, at every fresh period of growth a
new cement gland is formed, it has occurred to me, that possibly in
Pollicipes something similar may take place. In sessile Cirripedes, the
old cement-glands are all preserved in a functionless condition,
adhering to the membranous or calcareous basis, each new larger one
attached to that last formed, and each giving out cement-ducts, which,
bifurcating in the most complicated manner, pass outside the shell and
thus attach it to some foreign body.

The cem