Island and Reef Builders. 



of lime held in solution by the sea water, that the hard 

 parts of the coral are formed. 



This little Devonshire cup coral, so like a small 

 anemone in life, discloses, after its death and the decay 

 of its fleshy parts, a skeleton of singular beauty, com- 

 posed of carbonate of lime, and originally deposited 

 beneath the tissues of the living animal. This cup- 

 shaped coral is, to all intents and purposes, identical 

 with the reef-forming corals, but leads a solitary life, while 

 the reef-builders form colonies by budding, the buds 

 not becoming detached. As a result of long-continued 

 budding, extending layer over layer, the large solid 

 masses which go to form the coral reefs are gradually 

 built up. Of the rate of growth of these immense 

 masses of coral the marine biologist has yet much to 

 learn ; but some idea of the comparatively rapid growth 

 made under favourable conditions may be gathered from 

 the already ascertained facts, which show that one coral 

 animal, or polyp, one millimetre in diameter has been 

 known to bud out and form 693 grammes of coral in 

 thirty-six months. We know but little concerning the 

 duration of the life of these stony corals, beyond the fact 

 that the power of increase by budding, or asexual repro- 

 duction as it is called, is not unlimited, and that these 

 colonies, like individuals, have their allotted span of life, 

 attaining to a maximum rate of increase and then grow- 

 ing old, senile, and at last die a natural death. So far 

 as our present knowledge goes, the duration of life in 

 some of the solitary corals has been estimated at about 

 twenty-four years, while some of the reef-building 

 colonial forms are thought to live from twenty-two to 

 twenty-eight years. 



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