NO. 2 PRE-CAMBRIAN ALGONKIAN ALGAL FLORA 93 



In the paper by Drew " On the Precipitation of Calcium Car- 

 bonate in the Sea by Marine Bacteria " there are two paragraphs 

 that sum up the results of his work/ 



The observations so far available are too few, and the area they cover 

 too small, to attempt to make any broad generalization at present. However, 

 it can be stated with a fair degree of certainty that the very extensive chalky 

 mud flats forming the Great Bahama Bank and those which are found in places 

 in the neighborhood of the Florida Keys are now being precipitated by the 

 action of the Bacterium calcis on the calcium salts present in solution in 

 sea-water. From this the suggestion is obvious that the Bacterium calcis, 

 or other bacteria having a similar action, may have been an important factor 

 in the formation of various chalk strata, in addition to the part played by 

 the shells of Foraminifera and other organisms in the formation of these 

 rocks. Dr. T. Wayland Vaughan has also suggested that the Miami oolite 

 and other oolitic rocks may owe their origin to the occurrence of some dia- 

 genic change in the precipitate of very finely divided particles of calcium car- 

 bonate produced in this way by bacterial action. If this view as to the forma- 

 tion of chalk and oolite rocks is correct, it would seem probable that these 

 strata must have been deposited in comparatively shallow seas whose tempera- 

 ture approximated to that of tropical seas at the present time 



As it now stands, the investigation can, at most, be considered to offer 

 a mere indication of the part played by bacterial growth in the metabolism 

 of the sea. To obtain a real insight into the question, it would be necessary 

 to make more extensive bacterial and chemical observations in tropical, tem- 

 perate, and arctic waters, to study the bacteriology of other areas where calcium 

 carbonate is being precipitated from the sea, and to make further investigations 

 in the laboratory into the chemistry of the reactions that can be brought about 

 by various species of marine bacteria. 



Dr. T. Wayland Vaughan in discussing the formation of the 

 Floridian and Bahaman oolites before the Geological Society of 

 Washington said : ' 



The studies of Dall, Sanford, and the author, in association with Geo. C. 

 Matson, led to the opinion that the finely divided calcium carbonate oozes so 

 abundant in. Florida waters are chemical precipitates. Drew showed in 191 1 

 that denitrifying bacteria are an important agent m effecting this precipitation 

 in Florida waters ; and in 1912 he extended his researches to the Bahamas, 

 where he found them enormously abundant and active, as many as 160,000,000 

 being found in i cc. of surface mud on the west side of Andros Island. Rainey, 

 in 1858, Harting, in 1871, and Linck, in 1903 (and perhaps others), showed 

 that calcium carbonate precipitated by an alkali forms spherulites ; and Drew 

 noted a similar tendency of the calcium carbonate precipitated on his cultures. 

 Murray and Irvine showed that at higher temperature chemically precipitated 

 calcium carbonate is of the aragonite form 



^ t'apers from the Tortugas Laboratory, Carnegie Institution of Washington, 

 Vol. S, 1914, p. 44- 



' Journ. Washington Acad. Sci., Vol. 3, 1913- P- 302-304. 



