190 CARNEGIE INSTITUTION OF WASHINGTON. 



and the velocity of nerve conduction is proportional to the degree 

 of concentration of these adsorbed cations, but this rate is accelerated 

 by any free OH or H ions which may be present in the sea-water. 



In another study, Mayer found that reef corals can still capture food 

 until cooled within about 3° to 5° C. of their death temperature. Thus, 

 if the ocean were cooled to 61° F., all the reef species would probably 

 die from starvation if from no other cause, and it may be of interest to 

 observe that the surface-waters of Florida are at times cooled to 63° F. 

 by the northers of the winter months, and a heavy death-rate among the 

 fishes occurs. 



Dr. T. Wayland Vaughan, accompanied by Dr. E. W. Shaw, of the 

 United States Geological Survey, spent two weeks upon the Tortugas, 

 and, aided by Mr. Mills, they secured specimens of Texas Rock and 

 other submerged ledges in the Northwest Channel. They also made 

 shore-Une maps of the Tortugas Keys and studied the submarine 

 physiography of the lagoon, with a view to establishing the geologic 

 history of the region. It may be said that Dr. Shaw confirmed the 

 conclusions previously drawn by Vaughan respecting physiography and 

 sedimentation and pubhshed in the Year Book for 1914. After com- 

 pleting this study, these gentlemen visited several of the Florida Keys 

 between Key West and Miami, making use of the Anton Dohrn and 

 her launches, the Velella and the Henderson. 



Dr. Vaughan has now completed his study of the Tortugas region and, 

 when pubhshed, the results of his investigation of the geologic proc- 

 esses, and of the coral reefs, their growth-rate, ecology, and geological 

 status will be of great interest, demonstrating, as it does, the minor 

 role corals have had as builders of Umestones, and the importance of 

 bacterial, chemical, and constructional agencies. It is to be hoped, 

 therefore, that this most careful and intensive study of a coral-reef 

 region which has as yet been made by any man of science may result 

 in a volume accessible to all and creditable alike to Dr. Vaughan and 

 to the Carnegie Institution of Washington, whose high privilege it was 

 to afford him opportunities for these studies. He presents herewith a 

 condensed report upon the rate of growth of corals which is the most 

 complete and rehable account of the subject yet pubhshed. 



George Matthai, B. A., Esq., of Emmanuel College, Cambridge Uni- 

 versity, made a collection of corals at the Tortugas and preserved the 

 planulse in various stages for histological and anatomical study. 



John C. Waller, B. A., Esq., recently of King's College, Cambridge 

 University, studied the electrical conductivity and potential in the leaf- 

 stalks of plants, and presents a report herewith. 



An interesting botanical investigation has been commenced by H. H. 

 M. Bowman, of the University of Pennsylvania, upon the physiology, 

 ecology, and growth-rate of the mangroves of southern Florida. 



