CORALS, SEA-ANEMONES, AND JELLY-FISHES.
With the Sea-anemones and Jelly-fishes almost the lowest organised group of living animals is reached. As typified by an ordinary sea-anemone, the body may be described as a simple sac, the orifice of which is inverted for some little distance, and held in position with relation to the outer wall by a series of radiating partitions. One or more rows of tentacles, varying in number and character according to the species, surround the mouth of this partially inverted sac. There is no distinct intestinal track, the whole space enclosed within the outer wall and ramifying among the radiating partitions containing the digestive juices. The radiating membranous partitions develop upon their surfaces the reproductive elements, and in the case of Corals, which are merely skeleton-producing sea-anemones, partly secrete within them the symmetrical radiating calcareous plates so characteristic of the group.
Photo by W. Saville-Kent, F.Z.S.] [Milford-on-Sea.
A MUSHROOM-CORAL FULLY EXPANDED.
In this condition the coral, or skeleton of the animal, is entirely concealed.
Photo by W. Saville-Kent, F.Z.S.] [Milford-on-Sea.
|MUSHROOM-CORALS, WITH THE ANEMONE-LIKE POLYP EXPANDED.
Taken through the water on a coral-reef.