individual members of each of the two orders.

The pupae in both orders attach themselves by means of the adherent
feet; those of the Cirripedes to rocks, shells, turtles, drift-wood,
ships, etc.,--those of the Rhizocephala to the abdomen of Crabs,
Porcellanae, and Hermit Crabs. The carapace of the Cirripedes becomes
converted, as is well-known, into a peculiar test, on account of which
they were formerly placed among the Mollusca, and the natatory feet grow
into long cirri, which whirl nourishment towards the mouth, which is now
open. The Rhizocephala remain astomatous; they lose all their limbs
completely, and appear as sausage-like, sack-shaped or discoidal
excrescences of their host, filled with ova (Figures 59 and 60); from
the point of attachment closed tubes, ramified like roots, sink into the
interior of the host, twisting round its intestine, or becoming diffused
among the sac-like tubes of its liver. The only manifestations of life
which persist in these non plus ultras in the series of retrogressively
metamorphosed Crustacea, are powerful contractions of the roots, and an
alternate expansion and contraction of the body, in consequence of which
water flows into the brood-cavity and is again expelled, through a wide
orifice.* (* The roots of Sacculina purpurea (Figure 60) which is
parasitic upon a small Hermit Crab, are made use of by two parasitic
Isopods, namely a Bopyrus and the before mentioned Cryptoniscus
planarioides (Figure 42). These take up their abode beneath the
Sacculina and cause it to die away by intercepting the nourishment
conveyed by the roots; the roots, however, continue to grow, even
without the Sacculina, and frequently attain an extraordinary extension,
especially when a Bopyrus obtains its nourishment from them.)

(FIGURE 59. Young of Peltogaster socialis on the abdomen of a small
Hermit Crab; in one of them the fasciculately ramified roots in the