the sea. 



iliiipp 



68 THE UNIVERSE. 



bed of the sea. Volcanic action begins the work, and the 



Polypi finish it; they 

 bring the construction 

 up to the level of the 

 waves. These islands 

 always display a pe- 

 culiar configuration ; 

 they are nearly all 

 circular, and there is 

 a crater - like depres- 

 sion in the middle. 

 This peculiarity seems 

 to be owing to the fact 

 1. that the little work- 

 men can support their 

 vital energies better 

 where the water, be- 

 ing agitated, brings 

 them a more ample 

 supply of nourish- 

 ment. The animals 

 in the centre, being 

 placed under different 

 conditions, are less 

 vigorous and active, 

 and consequently can- 

 not raise their living 

 rampart so fast. 



In the Pacific Ocean, 



where a tolerably large number of those islands are seen, 



