196 CARNEGIE INSTITUTION OF WASHINGTON. 



such varied character that, between June and September at least, its fishes 

 may be studied most advantageously, in comparison with those of Hawaii, 

 for example. Satisfactory progress has been made during the past season in 

 establishing the relation which the various species bear to one another and 

 to their environment, and in securing a photographic record of their char- 

 acteristic activities. 



Studies on Sea-Water Bacteria and Other Svhjects in the South Seas, 

 by Charles B. Lipman. 



Precipitation of Calcium Carbonate. 



A new aspect of the subject of the origin of much of the mass of coral islands, 

 or of calcareous beds in their vicinity, was introduced by Drew in 1911. He 

 isolated an organism which he named Bacterium calcis, later renamed by Kel- 

 lerman and Smith Pseudomonas calcis, which he claimed was responsible for the 

 precipitation of the calcium carbonate in the calcareous muds underlying the 

 waters surrounding calcareous reefs and coral islands in the Florida-West 

 Indian region. This hypothesis for the explanation also of the oolitic depos- 

 its has been generally accepted by those concerned with the geology and 

 biology of the regions in question. 



In an attempt to determine whether or not similar causes for lime precipita- 

 tion are extant in the tropical Pacific, the writer made an investigation of the 

 bacterial flora of the sea-water surrounding certain reefs fringing the island of 

 Tutuila in American Samoa and also of that in the open ocean 2 or 3 miles 

 distant. This study resulted in the isolation of a number of sea-water bacteria 

 and the test of them as regards ability to precipitate calcium carbonate. In a 

 variety of tests it was not possible to obtain precipitation of calcium carbonate 

 in sea-water alone, except to a very slight degree with one or two bacteria. 

 Among the bacteria isolated, and which produced a slight precipitation of 

 CaCOa in sea-water, was one which resembles and is probably identical with 

 P. calcis. In a calcium-lactate sea-water medium the precipitation under 

 consideration was found to occur readily and markedly, but about equally 

 with all other organisms isolated. 



Since Drew did not try to obtain precipitation of calcium carbonate in 

 natural sea-water, the writer is led to the conclusion that his hypothesis is incor- 

 rect, or at least not proved, since calcium-malate sea-water which he used 

 is an artificial medium, an analogue of which would probably not occur under 

 natural conditions. The reason for the precipitation in the artificial medium 

 can easily be explained on the basis of the chemistry of such culture solutions. 

 The details of this study, presenting the several steps which led to the refuta- 

 tion of Drew's hypothesis, will be given in a forthcoming paper. An attempt 

 will be made, however, to study the situation in the tropical Atlantic under the 

 same conditions as those under which Drew worked, so that his results may 

 be checked, and so that we may ascertain if the difference between the two 

 environments can make possible the validity of the hypothesis tested for 

 one region and not for another. 



Number of Bacteria in the Sea-Water surrounding the Island of Tutuila. 



Studies were made on the number of bacteria in the waters covering the Aua 

 Reef and also of the waters 2 or 3 miles out to sea from the naval station of 

 Tutuila. The number of prganisms, as determined by plating out the waters 

 on nitrate-peptone sea-water agar, were approximately 1,000 to 2,000 bacteria 

 per cubic centimeter in the ocean-water from 2 to 3 miles out at sea, and from 

 70,000 to 100,000 bacteria per cubic centimeter in the water of the Aua region. 



