METAMORPHOSIS 



3752 



METAPHOR 



(1) Hardening of the rock, as in the case of 

 sandstone ; 



( 2 ) Change in composition and structure, as in 

 slate. Slate was at first mud, then it became 

 shale, and, finally, under the influence of heat and 

 pressure, it was changed into its present form ; 



(3) Crystallization. The formation of marble 

 from limestone is a good illustration of this 

 change. Under intense heat the limestone was 

 partially melted, and on cooling the particles ar- 

 ranged themselves in crystals, which are readily 

 seen by examining a p.iece of marble with a mag- 

 nifying glass. 



Rocks have been subjected to heat in two 

 ways; first, by lava, which has been forced up 

 through crevices or thrown out by volcanoes, 

 and, second, by movement of the earth's crust, 

 which is always accompanied by both heat and 

 pressure. See GEOLOGY. 



Metamorphic Rocks. Rocks changed by heat 

 and pressure, as described above, are known as 

 metamorphic rocks. They differ from igneous 

 rocks in that the latter were formed in the 

 state in which they now exist, while meta- 

 morphic rocks have had their characteristics 

 changed by heat and pressure. See IGNEOUS 

 ROCKS. 



METAMORPHOSIS, metamawr'josis. In 

 studying the life history of certain animals, 

 such as frogs, a great variety of insects, sea 

 urchins and crabs, we find that the little creat- 

 ure which emerges from the egg is wholly un- 

 like the full-grown animal, and that during the 

 process of development striking changes in 

 structure and appearance occur before maturity 

 is reached. This unfolding process is known 

 as metamorphosis, a name derived from a 

 Greek word meaning to transform. It is no- 

 where more strikingly illustrated than in the 

 life cycle of the butterfly, whose development 

 is also an example of complete metamorphosis. 

 That is, including its existence in the egg, it 

 passes through four stages of growth. The 

 newly-hatched creature is known as a larva, 

 and the first stage of development after its 

 emergence from the egg is the larval period. 



The Larval Butterfly. The larva of the but- 

 terfly is a crawling, fuzzy caterpillar, brown, 

 yellow or white in color, or a huge green worm 

 with broad rings of black, bearing no resem- 

 blance to the beautiful, winged adult. It has 

 several pairs of legs, biting jaws instead of 

 a long, slender, sucking tube, and no wings. It 

 eats greedily, grows rapidly and molts its skin 

 several times, after which it enters upon the 

 third, or pupal, period. 



The Pupa. The third stage in the life his- 

 tory of the butlterfly is a very quiet one, for the 



larva shuts itself up in a smooth, hard case 

 known as a chrysalis, which is suspended from 

 a twig or the underside of a leaf. During this 

 period of inactivity the wings, legs and body of 

 the mature insect are being formed, and other 

 mysterious changes are taking place which 

 science does not fully understand. 



The Imago. When the end of the third 

 period arrives the case splits open, and the 

 imago, or fully-developed insect, is released 

 from its prison. 



Other Examples. Another interesting ex- 

 ample of metamorphosis is that of the toad, 

 which comes out of the egg a small, wriggling 

 tadpole. This tiny creature lives under water 

 and breathes by means of gills, but as it grows 

 larger it develops lungs and pairs of fore- and 

 hind legs, and gradually loses its tail. Finally 

 it is ready to leave its home in the water and 

 live for the most part on the land, a full- 

 grown toad. The grasshopper is an insect 

 which passes through but three stages of de- 

 velopment, omitting the chrysalid period en- 

 tirely. Its metamorphosis is therefore incom- 

 plete. 



For special details, see FROG ; TOAD ; INSECT ; 

 BUTTERFLY ; MOTH, and other articles describing 

 animals subject to metamorphosis. Consult Lub- 

 bock's The Metamorphosis of Insects. 



METAPHOR, met' a for, one of the common- 

 est of the figures of speech, which indicates a 

 resemblance between two objects by applying 

 to one a name or an action which belongs to 

 the other. In the simile the resemblance is 

 pointed out by means of some such word as 

 like, or as; in the metaphor it is merely im- 

 plied; but the two figures resemble each other 

 closely, and to change one into the other is 

 easy. Literature abounds in metaphor, and the 

 least poetic man uses it almost daily in his 

 speech. Such expressions as "angry waves," 

 "soft speech," "singing brook," are all meta- 

 phorical in their origin, though they have be- 

 come so common that their figurative force is 

 no longer felt. In such quotations as the fol- 

 lowing, however, the mind feels the force of 

 the unaccustomed turns of thought, and is im- 

 pressed by them : 



Lowliness is young Ambition's ladder, 

 Whereto the climber-upward turns his face. 

 SHAKESPEARE : Julius Caesar. 

 He were no lion, were not Romans hinds. 



SHAKESPEARE : Julius Caesar. 

 I am the vine, ye are the branches. 



Bible. 



The Lord is my rock and my fortress. 



Bible, 



