. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . At the base ofeach tube-foot there is aglobular reservoir, or ampulla. A valve connects the tube-foot andampulla. When the ampulla is contracted, water is forced into anddistends the tube-foot; when the ampulla is distended, it withdrawsthe water from the tube-foot, thus acting like a suction-bulb. Whenwater is sent into the tube-feet they are greatly extended and are thenplaced against an object. The water being then withdrawn throughthe ampullae, a vacuum is formed, and the
. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . At the base ofeach tube-foot there is aglobular reservoir, or ampulla. A valve connects the tube-foot andampulla. When the ampulla is contracted, water is forced into anddistends the tube-foot; when the ampulla is distended, it withdrawsthe water from the tube-foot, thus acting like a suction-bulb. Whenwater is sent into the tube-feet they are greatly extended and are thenplaced against an object. The water being then withdrawn throughthe ampullae, a vacuum is formed, and the suckers are tightly at-tached. By the alternating movements of the ambulacra theanimal is dragged slowly along and moves with a gliding does not deviate from a straight path, going over elevationsor through depressions without turning aside; its body con-forms to the irregularities of the road and never bridges overspaces. The stomach extends a little way into the arms, and ashort intestine leads to the excretory opening in the center of theback. Starfishes are carnivorous and voracious, and are partic-. Diagram of water-vascular system of a starfish: amadrepoiite; b, stone-canal; c, ring-canal; d, radial canalse, ampullae ; /, ambulacra. STARFISHES 207 nlarly destructive to oyster-beds. The animal fastens itself to abivalve, and protrudes a part of its stomach, with which it envel-ops its prey and slowly sucks it out of its shell. When feedingon small niollusks they take them into the stomach regain by natural growth parts of the body whichmay be lost. Sometimes the animal throws off an arm to escapecapture, and self-mutilation also occurs where unfavorable con-ditions exist. Oystermen formerly were ignorant of the star-fishs wonderful powers of regeneration, and were in the habitof cutting up those captured in their forks and throwing themoverboard, thus increasing the number instead of destroying theirenemies, as each arm with a piece of the bod
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmarinea, bookyear1901
