Caprella.) a peculiar structure makes its appearance very early on the
anterior part of the back, by which the embryo is attached to the "inner
egg-membrane," and which has been called the "micropylar apparatus," but
improperly as it seems to me.* (* Little as a name may actually affect
the facts, we ought certainly to confine the name "micropyle" to canals
of the egg-membrane, which serve for the entrance of the semen. But the
outer egg-membrane passes over the "micropylar apparatus" of the
Amphipoda without any perforation, according to Meissner's and La
Valette's own statements; it appears never to be present before
fecundation, attains its greatest development at a subsequent period of
the ovular life, and the delicate canals which penetrate it do not even
seem to be always present, indeed it seems to belong to the embryo
rather than to the egg-membrane. I have never been able to convince
myself that the so-called "inner egg-membrane" is really of this nature,
and not perhaps the earliest larva skin, not formed until after
impregnation, as might be supposed with reference to Ligia, Cassidina
and Philoscia.) It will remind us of the union of the young Isopoda with
the larval membrane and of the unpaired "adherent organ" on the nape of
the Cladocera, which is remarkably developed in Evadne and persists
throughout life; but in Daphnia pulex, according to Leydig, although
present in the young animals, disappears without leaving a trace in the
adults.

The young animal, whilst still in the egg, acquires the full number of
its segments and limbs. In cases where segments are amalgamated
together, such as the last two segments of the thorax in Dulichia, the
last abdominal segments and the tail in Gammarus ambulans and Corophium
dentatum, n. sp., and the last abdominal segments and the tail in
Brachyscelus,* or where one or more segments are deficient, as in
Dulichia and the Caprellae, we find the same fusion and the same