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Show 276 PIIYSIOGNOMY OF PLANTS. below the surface of the sea. The diminution of temperature in descending takes place but slowly; that of light almost equally so; and the existence of numerous Infusoria at great depths shows that the polypifers would not want for food. In opposition to the hitherto generally received opinion of the entire absence of organic life in the Dead Sea, it is deserving of notice that my friend and fellow-laborer, M. Valenciennes, has received through the Marquis Charles de l'Escalopier, and also the French consul Botta, fine specimens of Porites elongata from the Dead Sea. This fact is the more interesting because this species is not found in the Mediterranean, but belongs to the Red Sea, which, according to Valenciennes, has but a few organic forms in common with the Mediterranean. I have before remarked that in France a sea fish, a species of Pleuronectes, advances far up the rivers into the interior of the country, thus becoming accustomed to gill-respiration in fresh waters; so we find that the coral-animal above spoken of, the Porites elongata of Lamarck, has a not less remarkable flexibility of organization, since it lives in the Dead Sea, which is over-saturated with salt, and in the open ocean near the Seychelle Islands. (See my Asie Centrale, t. ii. p. 517.) According to the most recent chemical analyses made by the younger Silliman, the genus Porites, as well as many other cellular polypifers (Madrepores, Andrreas, and Meandrinas of Ceylon and the Bermudas), contain, besides 92.95 per cent. of carbonate of lime and magnesia, some fluoric and phosphoric acids. (See pp.' 124-131 of "Structure and Classification of Zoophytes," by James D. Dana, Geologist of the United States Exploring Expedition, under the command of Captain Wilkes.) The presence of fluorine in the solid parts of polypifers reminds us of the fluorate of lime in the bones of fishes, according to the experiments of Morechini and Gay Lussac at Rome. Silex is only found mixed in very small quantity with flu01·ate and phosphate of lime in coral stocks; but a coralanimal allied to the Horn-coral, Gray's Hyalonema, has an axis of pure fibres of silex resembling a queue or braided tress of hair. Professor Forchhammer, who has been lately engaged in a thorough analysis of the sea-water from the most different parts of the globe, finds the quantity of lime in the Caribbean Sea remarkably small, |
