55S Microscopic Life in the Ocean at the South Pole. 



tor to the arctic regions of the earth, the latter becoming first 

 destitute of trees, then of grass, lastly of lichens and algse until 

 at the poles ice and death hold solemn reign. 



The greatest depths in the ocean at which Mollusca had been 

 found to exist were, according to the observations of Mr. Cuming 

 in the year 1834, the genera Venus Cytherea and Venericardia at 

 50, Byssoarca at 75, and Terebratula in 90 fathom water. Ac- 

 cording to Milne-Edwards and Elie de Beaumont, 244 metres, or 

 732 foot, formed the extreme range for the growth of corals and 

 the development of organic matter in the sea off the coast of 

 Barbary. From a 100-fathom depth, Peron drew up in the year 

 1800, off New Holland, Sertularice and a variety of corallines, 

 which were all luminous, and on an average three degrees higher 

 in temperature than the surface of the sea. In 1824 and 1825 Quoy 

 and Gaimard, in their valuable researches upon the structure of 

 corals, asserted that branched corallines could occur only in a depth 

 of from 40 to 50 fathom, and that in a 100 fathom of water Rete- 

 pora alone existed. According to Ellis and Mylius, who wrote in 

 1753, the greatest known depth from which a living animal had 

 been taken was the Umbellaria Encrinus, which was fished up by 

 Captain Adrian in Greenland from 236 fathom of water, equal to a 

 depth of 1416 foot. Specimens, however, of the sea-bottom have 

 been drawn up from still greater depths ; for at Gibraltar, Captain 

 Smith found in 950 fathom, or 5700 foot of water, sand containing 

 fragments of shells ; and Captain Vidal, according to Mr. Lyell, 

 detected in the mud of Galway Firth, from a depth of 240 fathom, 

 only some Dentalia, the remainder of the sea-bottom from the same 

 depth consisting of pulverized shells and other organic remains 

 devoid of life. 



According to the calculations of Parrot, a column of sea-water 

 at a depth of 1500 foot exercises a pressure of 750 pound, or 1\ 

 hundred- weight, upon the square inch ; and since the atmospheric 

 air enclosed in these animals of a delicate cellular structure descend- 

 ing from the surface of the ocean would produce alternately such 

 extremes of expansion and contraction as to appear destructive to 

 such organisms, just doubts have been raised whether organic life 

 could actually subsist at great depths. 



