DEPARTMENT OF MARINE BIOLOGY. 171 



Further Studies on the Drew Hypothesis of CaCOz Precipitation in Sea-Water, 



by Charles B. Lipman. 



The results of my Samoan investigations of 1920, reported briefly in the 

 Year Book of the Carnegie Institution, cast grave doubt on the validity of 

 Drew's hypothesis, which aims to account for deposits of precipitated CaC03 

 in the sea by ascribing them to the specific precipitating action of a bacterial 

 organism now named Pseudo7nonas calcis. Briefly recapitulated, my data of 

 1920 indicated, among other things, that there is no evidence, in the first place, 

 that the precipitation of CaC03 occurs in ordinary sea-water, but only in 

 artificial media containing large quantities of calcium salts of organic acids. 

 In the second place, even under the conditions of such artificial media as those 

 just mentioned, P. calcis is only one of many different organisms which 

 possess the power of precipitating CaC03| hence that power is not to be con- 

 sidered specific, as, for example, is that of the nitrifying bacteria in forming 

 nitrates, and hence the name P. calcis is misleading and possibly a misnomer. 



With these conclusions before him, the late Dr. A. G. Mayor decided that it 

 would be wise for me to continue my studies on this subject, and preferably at 

 Tortugas, in which region Drew did much of his work and formulated his 

 hypothesis. Dr. Mayor, therefore, invited me to continue my studies in 1921 

 by joining the Laboratory staff at Tortugas. I was unable to do so then, but 

 found it possible to accept a renewed invitation for the summer of 1922. My 

 experiments at Tortugas were more elaborate than those which I carried out 

 in Samoa, and while in some respects the results were different in detail from 

 the earlier ones, there is no difference in principle. From these results I have 

 become more firmly convinced than ever that no evidence is at hand in sup- 

 port of the Drew hypothesis as an explanation of the mechanism of CaC03 

 precipitation in natural sea-waters; that the conclusions which I reached in 

 1920 are essentially sound; that in addition an understanding of the elements 

 of ionic equilibrium in salt solutions renders clear the method by which CaC03 

 may be precipitated in sea-water. All these assertions are supported by experi- 

 mental data in my possession. 



The Fishes of Tortugas and Their Habits, by W. H. Longley. 



In the seven weeks from June 6 to July 25 distinct progress was made in 

 my research, now carried on at Tortugas for eight seasons. 



In photographing fishes in their natural surroundings, thoroughly satis- 

 factory results were obtained and many negatives secured suitable for illus- 

 trating the final report of the investigation. With increasing experience it 

 has been found possible to reduce the time of exposure of plates materially. 

 For general work one thirty-fifth of a second is sufficient, and under excep- 

 tional circumstances the time required to secure a picture with stop 8 may 

 be 0.01 second or less. 



In addition to one species, apparently new to science, the following (not 

 hitherto known from this locality) were observed: Mycteroperca tigris, M. 

 dimidiata, Hcemulon bonariense, H. carbonarium, Alutera scripta, Chromis 

 multilineatus, Iridio garnoti, and Sparisoma chrysopterum. Of these, the 

 last three at least appear to be new to the United States fauna. 



Of other species, the following, which are not very abundant, were observed 

 or discriminated for the first time: A ulostomus maculatus, Decapterus punctatus, 



