ner. Immediately before one of the periods of
exuviation, the ova burst forth from the the ovarian tubes in the
peduncle and round the sack, and, carried along the open circulatory
channels, are collected (by means unknown to me) beneath the
chitine-tunic of the sack, in the corium, which is at this period
remarkably spongy and full of cavities. The corium then forms or rather
(as I believe) resolves itself into the very delicate membrane
separately enveloping each ovum, and uniting them together into two
lamellae; the corium having thus far retreated, then forms under the
lamellae the chitine-tunic of the sack, which will of course be of larger
size than the last-formed one, now immediately to be moulted with the
other integuments of the body. As soon as this exuviation is effected,
the tender ova, united into two lamellae, and adhering, as yet, to the
bottom of the sack, are exposed: as the membranes harden, the lamellae
become detached from the bottom of the sack, and are attached to the
ovigerous fraena. To demonstrate this view, an individual should have
been found, with both the old and new chitine tunic of the sack, and
with the lamellae lying between them; this, I believe, I have seen, but
it was before I understood the full importance of the fact: a great
number of specimens would have to be examined in order to succeed again,
for the changes connected with exuviation supervene very quickly. I
have, however, several times found the ova so loose under the sack, as
to be detached with a touch from the ovarian tubes; and I have twice
carefully examined specimens, which had just moulted, as shown by even
the mandibles being flexible, in which the lamellae had not become united
to the fraena, but still adhered to the newly-formed chitine tunic of
the sack; in these, the ova were so tender, that they broke into pieces
rather than be separated from the membrane of the lamella, itself hardly
perfectly developed, for pulpy cellular matter adhered outside some of
the ova. These and other facts are quite inexplicable on any other view
than that advanced.

As the lamellae are formed without organic union with the parent, they
would be liable to be washed out of the widely open sack of the
Lepadidae, if they had not been specially attached to the _fraena_. These
fraena consist of a pair of more or less semicircular folds of skin,
depending inside the sack, on each side of the point of attachment of
the body. The fraena are