DEPARTMENT OF MARINE BIOLOGY. 175 



It is only within the past few years that the importance of hydrogen- 

 ion concentration has been recognized in physiological reactions. 

 Accordingly, Professor J. F. McClendon came to Tortugas to make a 

 physiological analysis of the sea-water and to attempt to make up an 

 artificial sea-water in a sj^nthetic manner, his previous notable work 

 upon the hydrogen-ion concentration and the buffer substances in 

 blood having fitted him in an exceptional manner for undertaking this 

 research. For this puipose, he was provided by the Laboratory with a 

 potentiometer which had been standardized by the United States 

 Bureau of Standards. He found that the hydrogen-ion concentration 

 of Tortugas sea-water ranged from 8.1 to 8.22 PH, and that it was but 

 Uttle if at all affected by suspended silt due to stirring up of the 

 bottom, as occurred during the heavy storm of July 4 to 6. As 

 shown by L. J. Henderson, the bicarbonates of the sea- water, being 

 only sUghtly dissociated, act as buffer substances to prevent any 

 slight addition of acid from producing a marked change in the hydro- 

 gen-ion concentration. 



Professor McClendon also made a physiological analysis of sea- 

 water, finding that its gaseous content was very important, and that 

 each liter of sea-water contained about 23.5 c. c. of 0.1 molecular NaOH, 

 which is balanced against the CO^, the pressure of which is 0.4 per cent 

 of an atmosphere. Thus he found that an artificial sea-water could be 

 made as follows: 1.0 molecular (NaCl 483.65 c. c.+NaBr 0.8 c. c. + 

 KCl 10.23 c. c. + NaHCOa 2.32 c. c.) + 0.5 molecular (MgS04 57.09 

 c. c. + MgClo 50.21 c. c. + CaCla 22.07 c. c.) + 373.63 c. c. of water. 

 As a solvent of the salts one should use either rain-water or distilled 

 water redistilled in a copper retort with a quartz condensing-tube, and 

 then throughly aerated by bubbling air through it. Sea-water made 

 according to this method sustained the vital activity of marine annuals 

 about as well as does natural sea-water. McClendon's method will 

 doubtless be of great value in physiological work wherein artificial sea- 

 water is required. 



Certain of the results of these studies of McClendon were at once 

 applied by Dr. Cary and Dr. Mayer in their work on the reactions of 

 Cassiopea, the hydrogen-ion concentration of the solutions in which 

 the animls were placed being detennined both before and after the 

 experiments. Using these data, Professor Cary redetermined the effects 

 of the presence or absence of the marginal sense-organs upon the rate 

 of the early stages of regeneration in Cassiopea, while Mayer redeter- 

 miaed the cur\'e for the rate of nerve-conduction of Cassiopea m natural 

 sea-water diluted with distilled water and also in various partial or 

 complete sea-water solutions. 



Professor Cary confirmed and made more precise his previous 

 determination that when even a single marginal sense-organ is present 

 the rate of the early stages of regeneration is more rapid than if a 



