26 THE STUDY OF ANIMAL LIFE CHAP. 



mist in the sea, countless millions of microscopic crea- 

 tures often enclosed in beautiful shells of flint and lime ; 

 myriads of them are always being killed at the surface 

 by vicissitudes of temperature and the like ; they sink 

 gently through the miles of water to find a grave in the 

 abysmal ooze. The submarine volcano top, which did 

 not reach the surface, is slowly raised by the rainfall of 

 these countless minutiae. Inch by inch for myriads of 

 years, the snow-drift of dead shells forms a patient pre- 

 paration for the coral island. The tiniest, hardly bigger 

 than the wind-blown dust, form when added together 

 the strongest foundation in the world. The vast whale 

 skeleton falls, but melts away till only the ear-bones are 

 left. Of the ruthless gristly shark nothing stays but 

 teeth. The sea-butterflies (Pteropods), with their frail 

 shells, are mightier than these, and perhaps the micro- 

 scopic atomies are strongest of all. The pile slowly 

 rises, and the exquisite fragments are cemented into a 

 stable foundation for the future city of corals. 



At length, when the height at which they can live is 

 reached, coral germs moor themselves to the sides of 

 the raised mound, and begin a new life on the shoulders 

 of death. They spread in brightly coloured festoons, 

 and have often been likened to flowers. They surround 

 their soft bodies with strong shells of carbonate of lime, 

 obtained by some transformation from the calcium 

 chloride or calcium sulphate of the sea-water. Sluggish 

 creatures they are, living in calcareous castles of in- 

 dolence ! In silence they spread, and crowd and smother 

 one another in a struggle for standing-room. The dead 

 forms, partly dissolved and cemented, become a broad 

 and solid base for higher and higher growth. At a cer- 

 tain height the action of the breakers begins, great 

 severed masses are piled up or roll down the sloping sides. 

 Clear daylight at last is reached, the mound rises above 

 the water. The foundations are ever broadened, as 

 vigorously out -growing masses succumb to the brunt of 

 the waves and tumble downwards. Within the surface- 

 circle weathering makes a soil, and birds resting there 

 with weary wings, or perhaps dying, leave many seeds 



