THE CIRRIPEDIA . 
473 
sued. The perfect or fully-developed barnacle or sessile Cirripede 
has a mouth almost in the shape of a proboscis, and it is sur- 
rounded by the usual structures noticed in the Crustacea , but they 
have been more or less modified in their growth. There is a 
swollen lip, and palpi are soldered to it ; and there are man- 
dibles, maxillae, and outer maxillae, which serve as a lower lip. 
The opening into the gullet is situated between the mandibles, 
and the oesophagus — or tube leading down to the stomach — is 
capable of violent swallowing movements, and the small creatures 
brought within the range of the mouth by the whip-like motion 
of the fine, hairy, and branched cirri are prevented from escaping 
by the palpi just mentioned. The mandibles have strong teeth, 
and their duty appears to be to crush and force anything down 
the oesophagus after it has been guided towards them by the 
spiny maxillae. The numerous cirri are jointed, spined, and hairy, 
and act as arms, although they are legs, so to determine currents 
in the water, which wash multitudes of small creatures within 
range of the mouth, and which supply the respiratory appendages 
with abundance of well aerated fluid. The stomach is curved 
and bent up, and is provided with glands and branching liver 
tubes, and is lined with an epithelium ; and small Cmstacea , mi- 
nute Mollusca, and larvae of all kinds are digested by it. When 
the food has been digested, the internal epithelial coat of the 
stomach covers it like a bag, and is forced out with it. The eyes 
in the, pedunculated Cirripedia are apparently united; but two 
lenses exist, and this double eye is situated deep within the body. 
It is attached to a muscle at the lowest part of the oesophagus, 
and lies actually on the upper part of the stomach, so that a ray 
of light has to pass through many tissues, and to dip down into 
the body before it can be felt by the optic nerve. Yet these crea- 
tures are probably sensitive to light. 
The Lepas and barnacle are bi-sexual, and the eggs, when 
excluded from the body, and to all intents and purposes laid, 
are collected in leaf-like masses within the sac which lines the 
shell, and they remain there to be hatched. The leaves of eggs 
are fertilised when they first enter the sac, and are kept from 
being washed out by a number of bead-like bodies mounted on 
stalks, which retain them within a reduplication or fold of the 
