Nerve-Conduction in Cassiopea Xamachana. 7 



fessor McClendon, who was engaged upon a study of the sea-water as a 

 physiological fluid. He found that the P H of the surface sea-water at 

 Tortugas in summer, at about 29 C., ranges from 8.1 to 8.2, the range 

 being due to variations in its carbonates. As is well known from the 

 studies of L. J. Henderson (1913), these carbonates act as a buffer 

 substance, and by ionizing they tend to neutralize the effects of any 

 slight accession of acid to the water. Thus McClendon found that 

 sea- water of P H 8.1 diluted with an equal volume of distilled water of 

 P H 6.04 gave a solution of P H 8.09. Also 50 per cent sea-water plus 

 50 per cent distilled water of P H 8 gives a solution which is fully as 

 alkaline as, if not slightly more so than, pure sea-water. 



A number of tests of the change in hydrogen-ion concentration after 

 pulsating rings had been in 500 c.c. of various dilutions of sea-water 

 showed that in daylight there was no considerable change in 1 hour; 

 while in four others it declined similarly in pure sea-water after 12 

 hours, and in 3 other rings placed for 12 hours each in 500 c.c. of 60 per 

 cent sea-water plus 40 per cent of 8 P H distilled water the P H had 

 declined to 7.95. The average change at the end of an hour was 

 certainly not greater than from 8.1 to 8.0 P H . 



The thermometer used in this research was compared with one which 

 had been recently standardized by the U. S. Bureau of Standards; both 

 thermometers read to 0.1 C. 



Ordinary distilled water often retains an acid reaction even after air 

 freed from C0 2 by passing through tubes containing granulated soda- 

 lime has been bubbled through it for 72 hours. Accordingly, Professor 

 George A. Hulett, of Princeton University, very kindly offered to have 

 prepared, under his direction and by his well-known method,* 144 

 liters of distilled water, which were sealed in 144 clean, steamed flasks of 

 pyrex glass. f The hydrogen-ion concentration of the contents of each 

 flask was tested separately and found to range from 0.80 to l.OX 10~ 6 , 

 the average being 0.9 X 10~ 6 , or about 6.045 P H . 



This water was taken to Tortugas and used in all experiments herein 

 mentioned. It retained a constant hydrogen-ion concentration and 

 apparently no injurious elements were derived from the pyrex glass. 

 In the series of experiments wherein the sea-water was diluted with 

 distilled water of about 6 P H , each pyrex glass flask was opened by 

 breaking the narrow neck of the flask and the water was used as soon as 

 possible, the opening in the neck of the flask being sealed in the 

 intervals by a plug of soft paraffine. The distilled water of 6 P H used 

 in diluting the sea-water was not aerated and was thus deficient in 

 oxygen. This, however, makes but little difference, for the commensal 

 plant cells in the tissues of Cassiopea are so active in diffuse daylight 

 that the medusa pulsates at a nearly normal rate even if placed in sea- 



*1896; Zeitschift phys. Chemie, Bd. 21, p. 287. 



fThis water was prepared and tested by Mr. J. H. Yoe in Professor Hulett's laboratory. 



