48 FLORIDA REEFS. 



io-neoiis mass of materials which formed its earhest condition, their inves- 

 tigation mingles with that of the astronomer, and we cannot trace the 

 limestone in a little coral without going back to the creation of our solar 

 system, when the worlds that compose it were thrown off from a central 

 mass in a gaseous condition. 



When the coral has become in this way permeated with lime, all parts 

 of the body are rigid, with the exception of the upper margin, the 

 stomach, and the tentacles. The tentacles are soft and waving, projected 

 or drawn in at will ; they retain their flexible character through life, and 

 decompose when the animal dies. For this reason the dried specimens 

 of corals preserved in museums do not give us the least idea of the living 

 corals, in which every one of the millions of beings composing such a 

 community is crowned by a waving wreath of white or green or rose- 

 colored tentacles. 



As soon as the little coral is fairly established and solidly attached to 

 the ground, it begins to bud. This may take place in a variety of ways, 

 dividing at the top or budding from the base or from the sides, till the 

 primitive animal is surrounded by a number of individuals like itself, of 

 which it forms the nucleus, and which now begin to bud in their turn, 

 each one surrounding itself with a numerous progeny, all remaining, how- 

 ever, attached to the parent. Such a community increases till its individuals 

 are numbered by millions ; and I have myself counted no less than fourteen 

 millions of individuals in a coral mass of Porites (Plate XVI.) measuring 

 not more than twelve feet in diameter. The so-called coral heads, which 

 make the foundation of a coral wall, and seem by their massive character 

 and regular form especially adapted to give a strong, solid base to the 

 whole structure, are known in our classifications as the Astrasans, so named 

 on account of the star-shaped form of the little pits crowded upon their 

 surface, each one of which marks the place of a single more or less 

 isolated individual in such a community. 



Thus firmly and strongly is the foundation of the reef laid by the 

 Astraeans (Plate IV.); but we have seen that for their prosperous growth 

 they require a certain depth and pressure of water, and, when they have 

 brought the wall so high that they have not more than six fathoms of 

 water above them, this kind of coral ceases to grow. They have, however, 

 prepared a fitting surface for different kinds of corals that could not live 

 in the depths from which the Astraeans have come, but find their genial 



