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CARNEGIE INSTITUTION OF WASHINGTON. 



limestone dissolves in sea-water which remains alkaline during the process of 

 solution, but that this solution is slow. This supports the conclusion of Dr. 

 Shiro Tashu'O, that normal alkaline sea-water contains some substance, prob- 

 ably free CO2, which dissolves limestone. The amount of this free acid is, 

 however, so slight that its effect as a solvent is practically negligible, and 

 Vaughan is correct in his contention that the sea-water as such has not been a 

 significant factor in deepening the lagoons of atolls through solution. 



For example, the thickness of calcium carbonate removed from the sm'faces 

 of these shells ranged from 0.00067 to 0.00069 mm. after a year's immersion in 

 alkaline sea-water, and the shell which was buried beneath the mud and sub- 

 jected to H2S as well as to CO2 lost a superficial thickness of 0.0019 mm. in 

 a year. Taking this latter figure as a maximum rate of solution of limestone 

 due to sea-water as such, it appears that the time required to dissolve out a 

 depth of 20 fathoms would be 19,250,000 years, or about 1,000,000 years to 

 a fathom, and as many lagoons 15 to 20 fathoms deep appear to have been 

 formed since the beginning of the Recent period, it is evident they have not 

 been caused by solution due to sea- water as such, for even if reef limestone 

 dissolves 100 times as fast as did this Cassis shell it would require 144,000 to 

 192,500 years to form the present lagoons. 



The chief factors causing solution of submarine limestone in coral-reef 

 regions are undoubtedly fresh water draining off the forested shore, holo- 

 thurians, echini, fishes, boring algse, and sponges, and numerous other animals 

 and plants, which swallow or dissolve limestone, but even all these taken 

 together are not sufficient to prevent the silting up of most atoll lagoons, as 

 has been well shown by Guppy, F. Wood-Jones, Vaughan, and others. 



The Lower Temperature at which Reef Corals Lose their Ability to Capture 

 Food, by Alfred G. Mayer. 



Upon gradually cooling the sea-water within which hungry reef corals are 

 living, it was found that they gradually lost their activity, and with it their 

 ability to capture food (crab or snail meat). Food already captured, however, 

 could be held upon the surface of the tentacles or other parts to within 1° 

 of death temperature, whereas the corals lost the power to seize fresh pieces 

 of crab meat at about 3° to 5° C. above death temperature. Thus: 



Thus at about 61° F., or 16° C, most of the reef corals would be unable to 

 capture food, and doubtless a sustained exposure to such a temperature would 

 be fatal. 



Report upon the Behavior of the Dimorphic Spermatozoa of Strombus, 

 by Edwin E. Reinke. 



As was reported in the Year Book for 1914, it was proposed to continue, 

 during the season of 1915, at the Tortugas Laboratory, the experiments on the 

 behavior of the spermatozoa of Strombus, using an artificial sea-water instead 

 of natural sea-water. It had been found that there was a considerable amount 

 of variation in the behavior of the spermatozoa in cultures made with pure 



