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conjoined twins

(Encyclopedia)conjoined twins, congenitally united organisms that are complete or nearly complete individuals, historically known as Siamese twins. They develop from a single fertilized ovum that has divided imperf...

Plzeň

(Encyclopedia)Plzeň pŭlˈzĕnyə [key], Ger. Pilsen, city (1991 pop. 173,008), W Czech Republic, in Bohemia, at the confluence of several rivers. One of the Czech Republic's largest cities, it lies near a belt of...

chemical warfare

(Encyclopedia)chemical warfare, employment in war of incendiaries, poison gases, and other chemical substances. Ancient armies attacking or defending fortified cities threw burning oil and fireballs. A primitive ty...

seasons

(Encyclopedia)CE5 The seasons are caused by the tilt of the earth's axis to the plane of its orbit about the sun. The Northern Hemisphere is tilted toward the sun in the summer and receives more direct rays than...

De Long, George Washington

(Encyclopedia)De Long, George Washington də lôngˈ [key], 1844–81, American arctic explorer, b. New York City, grad. Annapolis, 1865. In 1873 he was assigned to the Juniata, which was sent to the arctic to sear...

vacuum

(Encyclopedia)vacuum, theoretically, space without matter in it. A perfect vacuum has never been obtained; the best human-generated vacuums contain less than 100,000 gas molecules per cc, compared to about 30 billi...

raccoon

(Encyclopedia)raccoon, nocturnal New World mammal of the genus Procyon. The common raccoon of North America, Procyon lotor, also called coon, is found from S Canada to South America, except in parts of the Rocky Mt...

amphibian, in zoology

(Encyclopedia)amphibian, in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (or...

apple

(Encyclopedia)apple, any tree (and its fruit) of the genus Malus of the family Rosaceae (rose family). Apples were formerly considered species of the pear genus Pyrus, with which they share the characteristic pome ...

bass, in zoology

(Encyclopedia)bass băs [key], common name applied to various fishes of Centrarchidae (black basses and sunfishes), Serranidae (sea basses and groupers), Moronidae (temperate basses), and other families. All basses...