CORALS 167 



time by which we can approximate a calculation, and 

 we are constrained to believe that our lifetime, so far 

 as this world is concerned, is extremely brief. 



The coral polyps cannot thrive unless the tempera- 

 ture of the water all the year round be over 68 Fahr. 

 In England we frequently see evidences of coral 

 growths belonging to the remote past, as at Newton 

 Abbot and other parts of Devon, but the mean annual 

 temperature of our surrounding waters is much less 

 than 68, so that our climate must be quite different 

 from that when these corals were tenanted with 

 beautiful polyps. 



We can hardly fancy that parts of England were 

 reared by or owe their stability to coral growths. An 

 inquiry into the origin of many islands and even 

 portions of continents would convince us that the 

 coral polyps of the past have left behind them 

 veritable monuments that are hundreds of miles in 

 extent. Not a few geologists believe that the Dolomite 

 Mountains are the direct result of coral agency ! 

 Their chemical composition magnesia and carbonate 

 of lime supports this belief. 



In speaking of the coral creatures we must discard 

 the term ' insect ' in favour of c polyp.' An insect is a 

 creature that in one stage of its life must have six 

 jointed legs, a body almost cut into two parts, hence 

 its name, a complicated nervous system, besides 

 circulatory and visceral systems. The coral polyp can 

 lay claim to none of these possessions. It resembles 

 the sea-anemones of our own Channel off the coast 



