THE ANIMAL KINGDOM. 73 



It is principally in the Soutli Sea and the Eed Sea that 

 the polypoids abound. At the approaches to the Maldive 

 Islands they form extraordinary masses, of not less extent 

 than the Alps according to the accounts of travellers. 



After having described the methods by which the 

 Polypi raise their dangerous reefs so fatal to mariners, 

 Owen thus sums up as to the immensity of their labours. 

 "The prodigious surface over which the combined and 

 ceaseless toil of these little architects extends, ought to 

 be taken into consideration in order to understand the 

 important part they play in nature. They have built a 

 barrier of reefs 400 miles long round New Caledonia, and 

 another which extends along the north-east coast of 

 Australia 1000 miles in length. This rei^resents," adds 

 the illustrious zoologist, "a mass in comparison with which 

 the walls of Babylon and the Pyramids of Egypt are 

 child's toys. And these edifices of the Polypi have been 

 reared in the midst of the ocean waves, and in defiance of 

 tempests which so rapidly annihilate the strongest works 

 constructed by man."^ 



Notwithstanding their extreme minuteness, the Polypi 

 have nevertheless, by their calcareous buildings, reacted 

 powerfully on the crust of the terrestrial globe. They 

 have modified it in two ways, by raising the bed of the 



1 Messrs. Quoy, Gayinard, and Ehrenberg, however, without denying tluit 

 these Polypi have executed immense works in the sea, still think that their per- 

 formances have been much exaggerated. A modern observer fixes the growth of 

 the madrepore reefs at not more than a millimetre and a half, or about the twen- 

 tieth of an inch, yearly. M. Ehrenberg, who shares this opinion, thinks that the 

 masses of madrepore seen in the Bed Sea were very likely contemporary with 

 the Pharaohs. 



This illustrious observer maintains that it is not probable that harbours are 

 so rapidly obstructed by these living reefs as has been stated. He calls atten- 

 tion to the fact that the harbour of Tor, known to have been constructed about 

 1300 years ago, has not been iu any way blocked up by the polypoids which 



abound in the vicinity. 



10 



