Chapter Iii.--World-Builders.

The world outside the terrestrial world, 79 The world of the infinitely little; the architects of ocean, 80 The immense works accomplished by the lower organisms, 81 They build up reefs, banks, islands, 82 The manufacture of chalk described, 83 How a coral-island is gradually developed, 83, 84 Examples of the labours of the coral animals, 85