HYDRA 



2884 



HYDRANGEA 



the British residency are other points of inter- 

 est. Hyderabad has extensive and costly 

 waterworks. Population, 1911, 500,620. 



HYDRA, hi'dra, in Greek legend, a monster 

 which dwelt in Lake Lerna, in Argo'lis. It was 

 credited with possessing many heads, of which 

 the central one was immortal. The number of 

 heads varied from nine to 100, any one of 

 which being cut off was immediately replaced 

 by two others, unless the wound was seared 

 by fire. The destruction of this monster was 

 the second labor of Hercules, and was accom- 

 plished with the assistance of lolaus who, as 

 each head was cut off, cauterized the wound. 

 The immortal head was buried beneath a huge 

 stone. See HERCULES, subhead The Twelve 

 Labors. 



HYDRA, FRESH-WATER, or FRESH- WATER 

 POLYP, pol'ip, one of the simplest of the 

 many-celled animals, an inhabitant of fresh- 

 water ponds. It belongs to the same branch 

 of the animal kingdom as the sea anemones, 

 corals and jelly- 

 fishes (see COE- 

 LENTERATA). 

 The hydra has a 

 cylindrical body, 

 which is about as 

 thick as fine sew- 

 ing-cotton and 

 from one-fourth 

 of an inch to half 

 an inch long. At 

 one end of the 

 body there is a 

 disklike expan- 

 sion, or foot, with HYDRA 



wViir>h it plintT trv One form of this strange 



wnicn it clings to water anirnal The illust r a . 



bits of sticks, tion a shows a cross section 



. . of the body, outlining the two 



stones and leaves layers of minute cells which 



in the water; at com P se the bod y walls - 

 the opposite end is a mouth from which pro- 

 jects a circle of delicate threads, called tenta- 

 cles, varying in number from five to twelve 

 or more. 



Specimens brought into the schoolroom and 

 kept in a dish of water in the light afford an 

 extremely interesting study. If watched under 

 a microscope the hydra will seem to be con- 

 tinually changing in form. Sometimes it 

 stretches out its tentacles until they look like 

 long, delicate threads; at other times it con- 

 tracts its tentacles and its whole body until 

 it has the appearance of a tiny egg with a 

 group of wartlike knobs at one end. It is also 

 able to move slowly from place to place. If 



some small water fleas are placed in the dish, 

 its method of obtaining its food can be ob- 

 served. The tentacles are provided with many 

 fine little stinging threads, which the hydra 

 shoots into the body of its prey, like a minia- 

 ture lasso. These barbs have a paralyzing 

 effect, and the captured insect is soon mastered 

 and drawn by the contraction of the tentacles 

 into the mouth cavity. 



Hydras propagate for the most part by bud- 

 ding. That is, tiny knoblike growths appear on 

 the body of the parent animal, which, as they 

 become larger, gradually acquire tentacles. 

 When fully developed they break off and begin 

 existence anew as independent hydras. One 

 of the most interesting facts in connection 

 with the hydra is its power of multiplying by 

 division. As a rule, if a hydra be cut into 

 two or more pieces, each portion will in time 

 develop into a new animal. Several species 

 of this animal have been identified, two of 

 which are common in America. One is bright 

 green in color, due to the presence of chloro- 

 phyll, the coloring matter found in plants. The 

 other is grayish-brown. B.M.W. 



HYDRANGEA, hidran'jea, the name given 

 to about twenty-five species of ornamental 

 shrubs of the saxifrage family, which are found 



THE HYDRANGEA 



in North and South America, China and Japan. 

 The flowers vary from white to pink and 

 bluish and are small individually, but they 

 grow in large, showy clusters. When grown 

 on some soils, the pink varieties will in time 



