CORAL REEFS. 23 



fathoms below the surface. On page 22 we nave its pic- 

 ture (No. 1 8) . Now fancy that some of those little coral 

 animals I have described as swimming about freely in 

 the water when they are first born, should attach them- 

 selves upon the side of this island, and should begin to 

 bud and spread in large coral heads all around it. We 

 must remember that it is not only by budding that they 

 increase, but also by eggs ; these eggs, when hatched, are 

 the little pear-shaped, free Corals which float about for a 

 while, and then fasten themselves upon the community, 

 so that they not only multiply by dividing and branching, 

 but also by the addition of all the little animals that are 

 born from their eggs. As this coral bank grows, the 

 lower ones gradually die, their solid frames still remain- 

 ing to form a firm foundation for all that grow above 

 them. All the cracks and crevices are filled with sand, 

 Dits of shell, &c., so that it makes a wall as strong as 

 any masonry. When they have, by their growth, formed 

 a ridge all around the island, they begin to grow up- 

 ward from the foundation which they have laid, thus 

 raising a circular wall about it. When they have 

 reached a certain height in the water, those Corals 

 which like to live in deep water will no longer grow 

 there, and they die out ; but, on the surface that they 

 have prepared, new kinds, such as like the shallow 

 water, begin to establish themselves, and they continue 

 the wall the others had begun. As it goes on increasing 

 .in height, these also find the water too shallow for them \ 

 and now, to complete the work, come in the branching 

 ones, which I have described to you as resembling 

 sea- weeds and plants, and so the wall is crowned by a 

 waving shrubbery. This brings it at last to the sur- 



