276 PHYSIOGNOMY 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 1'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 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-respira- 

 tion in fresh water ; 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. 51 7.) 



According to the most recent chemical analyses made by the 

 younger Silliman, the genus Porites, as well as many other cellular 

 polypifers (Madrepores, Andrseas, 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. 

 124131 of " Structure and Classification of Zoophytes," by James 

 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 fluorate and phosphate of lime in coral stocks ; but a coral- 

 animal 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, 



