. Outlines of zoology. the base of this lies theanus. Around the body there is a fold of skin, and from this ariie fivecalcareous plates, an unpaired dorsal carina, two scuta right and left 304 PHYLUM ARTHROPODA. anteriorly, two terga at the free posterior end. The nervous systemconsists of a brain, an cesophageal ring, and a ventral chain of five orrnore ganglia. There is a fused pair of rudimentary eyes. No specialcirculatory or respiratory organs are known. Two excretory (?) tubeslead from (ccelomic) cavities to the base of the second maxillae, and areprobably comparable with shell glands a

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. Outlines of zoology. the base of this lies theanus. Around the body there is a fold of skin, and from this ariie fivecalcareous plates, an unpaired dorsal carina, two scuta right and left 304 PHYLUM ARTHROPODA. anteriorly, two terga at the free posterior end. The nervous systemconsists of a brain, an cesophageal ring, and a ventral chain of five orrnore ganglia. There is a fused pair of rudimentary eyes. No specialcirculatory or respiratory organs are known. Two excretory (?) tubeslead from (ccelomic) cavities to the base of the second maxillae, and areprobably comparable with shell glands a Stock Photo
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. Outlines of zoology. the base of this lies theanus. Around the body there is a fold of skin, and from this ariie fivecalcareous plates, an unpaired dorsal carina, two scuta right and left 304 PHYLUM ARTHROPODA. anteriorly, two terga at the free posterior end. The nervous systemconsists of a brain, an cesophageal ring, and a ventral chain of five orrnore ganglia. There is a fused pair of rudimentary eyes. No specialcirculatory or respiratory organs are known. Two excretory (?) tubeslead from (ccelomic) cavities to the base of the second maxillae, and areprobably comparable with shell glands a
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Image ID: 2AGERY2
. Outlines of zoology. the base of this lies theanus. Around the body there is a fold of skin, and from this ariie fivecalcareous plates, an unpaired dorsal carina, two scuta right and left 304 PHYLUM ARTHROPODA. anteriorly, two terga at the free posterior end. The nervous systemconsists of a brain, an cesophageal ring, and a ventral chain of five orrnore ganglia. There is a fused pair of rudimentary eyes. No specialcirculatory or respiratory organs are known. Two excretory (?) tubeslead from (ccelomic) cavities to the base of the second maxillae, and areprobably comparable with shell glands and with nephridia. There is acomplete food canal and a large digestive gland. Beside the latter liethe branched testes, whose vasa deferentia unite in an ejaculatory ductin the penis. From the much-branched ovaries in the stalk, the ovi-ducts pass to the first thoracic legs, where they open into a cement-making sac, opening to the exterior. The eggs are found in flat cakesbetween the external fold of skin and the body.. ov Mn Fig. 158.—Acorn-shell [Bdlanus tintiimabulum).—After Darwin. T., tergum; CR., thoracic legs ; R., outer shell in section ; D., aper-ture pf oviduct; F.t mantle cavity; X, depressor muscle oftergum; ^ A?., antennae; Of., ovary; G., depressor of scutum ;H., oviduct; AM.^ adductor muscle of scuta; S., scutum. The life history. Nauplius larvae escape from the egg-cases, and,after moulting several times, become like little Cyprids. The firstpair of appendages become suctorial, and, after a period of free-swimming, the young barnacle settles down on some floating object,mooring itself by means of the antennary suckers, and becoming firmlyglued by the secretion of the cement glands. During the settling andthe associated metamorphosis, the young barnacle fasts, living on astore of fat previously accumulated. Many important changes occur,the valved shell is developed, and the adult form is gradually assumed. The food consists of small animals, which are swept t