114 POPULAR ILLUSTRATIONS OP 



a peep at the life history of its builders. We shall then be better 

 prepared to inquire about reefs and lagoons, and the coral islands of 

 southern climes. 



I have already described the sea-anemone, and stated that the 

 Coral polyp is a diminutive variety of the same order, Actinia. 

 Dana, a well-known American author, compares the Coral polyp to 

 an aster, and the analogy is a very good one. The tentacles open 

 out in a circle, and are often richly coloured, and the central disc 

 of different tints gives a very good imitation of the China aster. 

 Instead, however, of the stalk of the flower, we have in the polyp a 

 broader pedicil containing the stomach, somatic cavity, and lamellar 

 tables, as seen in the sea-anemone. 



In natural history we always, or almost always, find a connecting 

 link between distinct groups, leading, as naturalists say, from one to 

 the other. Between the " hard basic " and " hard skin " groups of 

 Corals this transition is effected by a clove-shaped Coral, well known 

 as Caryophylla. This is a sclero-dermic Coral, and the transverse 

 divisions seen in the figure (No. 171, frontispiece) indicate dead 

 Coral, the only live portion being that at the end, where the polyps 

 are expanding. This is quite distinct from the tree-shaped red coral 

 stem, which forms the axis round which thousands of polyps and 

 their coenosarc are placed, increasing their stem both in thickness and 

 length. To illustrate the history of a reef Coral, we will, however, 

 take a more typical example. Well, then, let us suppose that the 

 polyp of a large family, called, from their star-like appearance, 

 Astrea, deposits an egg ; this egg is developed into a young polyp, 

 having cilia, by which it moves through the water, as we have seen 

 in the young Sponge. Having swum about and increased in stature, 

 the young polyp fixes itself in some spot which its instinct tells it 

 will be most convenient for its future success in life. Having once 

 become fixed it lays the foundation of a colony, and it may be of an 

 island or a continent, as we shall see by and by. Without any 

 power or exertion of its own, the vital force inherent in its nature 

 selects from the food taken into the stomach carbonate of lime, and 

 with this it forms on the sclero-dermic system not, mark, as many 

 suppose, a house for the polyp to live in, but a beautiful, strong, and 

 permanent calcareous skeleton, by which the delicate form of the 

 polyp may be supported and protected. This is termed a corallite, 

 and the creature now increases, as far as its own colony is concerned, 

 either by dividing its own body, termed fissiperation, which takes 

 place at the base, or more frequently by buds springing out from its 

 side ; each bud or each divided portion forms into distinct polyps, 

 which increase themselves with great rapidity in the same way, and 

 each having secreted its corallite, they form in their totality a corallum. 



