Beginners' zoology . e when the tide is in,and draws into its shell the water containing animalculesand oxygen. Oysters to the value of many millions of dollars are gath-ered and sold every year. The most valuable oyster fish-eries of North America are in Chesapeake Bay. Theyoung oysters, or spat, after they attach themselves tothe bottom in shallow water, are transplanted. New oysterbeds are formed in this way. The beds are sometimesstrewn with pieces of rock, broken pottery, etc., to encouragethe oysters to attach themselves. The dark spot in thefleshy body of the oyster is the digestive gla
Beginners' zoology . e when the tide is in,and draws into its shell the water containing animalculesand oxygen. Oysters to the value of many millions of dollars are gath-ered and sold every year. The most valuable oyster fish-eries of North America are in Chesapeake Bay. Theyoung oysters, or spat, after they attach themselves tothe bottom in shallow water, are transplanted. New oysterbeds are formed in this way. The beds are sometimesstrewn with pieces of rock, broken pottery, etc., to encouragethe oysters to attach themselves. The dark spot in thefleshy body of the oyster is the digestive gland,, or cut ends of the tough adductor muscles are noticeablein raw oysters. The starfish is very destructive in oysterbeds. Pearls are deposited by bivalves around some irritatingparticle that gets between the shell and the mantle. Thepearl oyster furnishes most of the pearls; sometimespearls of great value are obtained from fresh-watermussels. Namearticles that are made partly orwholly of A Snail. Study of a LiveSnail or Slug. — Is ?> -I 2, mouth; vf, hf, feelers; e, opening of egg duct; /, foot; moist ? Do land >««, mantle; /?<, opening to lung; a, vent. snails and slugs have lungs or gills? Why? How many pairsof tentacles have they? What is their relative length and position?The eyes are dark spots at bases of tentacles of snail and at thetips of the rear tentacles of slug. Touch the tentacles. Whathappens? Do the tentacles simply stretch, or do they turn inside io6 BEGINNERS ZOOLOGY
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1921
