Outlines of zoology . Fig. 10.—Fresh-water crayfish(Astacus), a Crustacean.—After Huxley. Fig. II.—a, Caterpillar;6, pupa; i, butterfly. lo GENERAL SURVEY OF THE ANIMAL Fig. 12.—Spider. appendages. The skin produces an external, not-livingcuticle, the organic part of which is a substance calledchitin, associated in Crustaceans with carbonate oflime. The nervous system con-sists of a dorsal brain, connected,by a nerve-ring around thegullet, with a ventral chain ofganglia. Echinoderms. — This is a well-defined series, including star-fishes,brittle-stars, sea-urchins, sea-cucum-bers, an
Outlines of zoology . Fig. 10.—Fresh-water crayfish(Astacus), a Crustacean.—After Huxley. Fig. II.—a, Caterpillar;6, pupa; i, butterfly. lo GENERAL SURVEY OF THE ANIMAL Fig. 12.—Spider. appendages. The skin produces an external, not-livingcuticle, the organic part of which is a substance calledchitin, associated in Crustaceans with carbonate oflime. The nervous system con-sists of a dorsal brain, connected,by a nerve-ring around thegullet, with a ventral chain ofganglia. Echinoderms. — This is a well-defined series, including star-fishes,brittle-stars, sea-urchins, sea-cucum-bers, and feather - stars. Thesymmetry of the adult is usuallyradial, though that of the larva isbilateral. A peculiar system, knownas the water - vascular system, ischaracteristic, and is turned to various uses, as inlocomotion and respiration. There is a marked tend-ency to deposition of lime in the tissues. The develop-ment is strangely circuitous or indirect. Segmented worms.—It is hopeless atpresent to arrange withany definiteness thoseheterogeneous forms towhich the title worm is given. For this titleis little more than aname for a shape,assumed by animals ofvaried na
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
