but little movement. In the Bopyridae (Bopyrus, Phryxus, Kepone, etc.,
which might have been conveniently left in a single genus), which are
parasitic on Crabs, Lobsters, etc., taking up their abode chiefly in the
branchial cavity, the adult females are usually quite destitute of eyes;
the antennae are rudimentary; the broad body is frequently
unsymmetrically developed in consequence of the confined space; its
segments are more or less amalgamated with each other; the feet are
stunted, and the appendages of the abdomen transformed from natatory
feet with long setae into foliaceous or tongue-shaped and sometimes
ramified branchiae. In the dwarfish males the eyes, antennae, and feet,
are usually better preserved than in the females; but on the other hand
all the appendages of the abdomen have not unfrequently disappeared, and
sometimes every trace of segmentation. In the females of Entoniscus,
which are found in the body-cavity of Crabs and Porcellanae, the eyes,
antennae, and buccal organs, the segmentation of the vermiform body, and
in one species (Figure 41) the whole of the limbs, disappear almost
without leaving a trace; and Cryptoniscus planarioides would almost be
regarded as a Flatworm rather than an Isopod, if its eggs and young did
not betray its Crustacean nature. Among the males of these various
Bopyridae, that of Entoniscus Porcellanae occupies the lowest place; it
is confined all its life to six pairs of feet, which are reduced to
shapeless rounded lumps.

The Amphipoda are distinguishable from the Isopoda at an early period in
the egg by the different position of the embryo, the hinder extremity of
which is bent downwards. In all the animals of this order which have
been examined for it,* (* In the genera Orchestoidea, Orchestia,
Allorchestes, Montagua, Batea n.g., Amphilochus, Atylus, Microdeutopus,
Leucothoe, Melita, Gammarus (according to Meissner and La Valette),
Amphithoe, Cerapus, Cyrtophium, Corophium, Dulichia, Protella and