8 Papers from the Department of Marine Biology. 



water which had been boiled for an hour to expel its air, then restored 

 to its former volume by air-free distilled water and cooled to normal 

 temperature. Thus in daylight the medusa appears to be able, due to 

 its plant cells, to supply nearly if not quite enough oxygen for its 

 normal metabolism. The presence of free CO 2 in the surrounding 

 sea- water is, however, very toxic and soon stops pulsation, and in dark- 

 ness unreduced C0 2 accumulates, and thus the rate of movement is 

 considerably slower than in daylight. 



In another series of experiments, it was desired to dilute sea-water 

 with distilled water of the same hydrogen- ion concentration as that of 

 the sea-water itself. Accordingly, 50 flasks of Professor Hulett's 

 distilled water were broken and the contents poured into a green-glass 

 carboy which had previously contained Merck's distilled water. Air 

 which had been freed from C0 2 by drawing it through glass tubes 

 containing granulated soda-lime was then bubbled vigorously through 

 this distilled water for 78 hours, after which the water had a P H 

 of 8. It was protected from the carbon dioxide of the atmosphere by 

 permitting only air which had passed through soda-lime tubes to enter 

 the carboy, and thus it retained an unchanged alkalinity remaining 8 

 P H from July 4 to 11 inclusive, during which time 139 dilution 

 experiments were conducted with it; after this its alkalinity began to 

 decline while 26 additional experiments were made. The average for 

 the entire series was 7.93 P H or a hydrogen-ion concentration of 

 1.17XKT 8 . 



The fixity of the alkalinity at P H 8 for so many days was probably 

 due to OH ions derived from the alkaline green glass of the carboy, 

 which may have been counterbalanced by a slight leakage of CO 2 

 through the rubber stopper of the carboy. Then, when the volume 

 of the water became reduced, the surface over which solution of glass 

 took place was relatively reduced in comparison with the surface 

 capable of absorbing atmospheric CO 2 , and thus the water finally 

 tended toward acidity. Previous to its being used to hold the distilled 

 water the carboy was cleaned by washing it with solutions of HC1, 

 distilled water, KOH, absolute alcohol, and finally distilled water, tak- 

 ing precautions to prevent dust from entering. 



The rings cut from the subumbrella of Cassiopea were attached to 

 the kymograph lever by threads of catgut (fig. 15) ; while the rings 

 themselves were each placed in 500 c.c. of solution contained in clean 

 glass jars, covered between tunes of record-taking to prevent evapora- 

 tion and to exclude dust. 



Each ring was first placed in 500 c.c. of sea-water and its rate and 

 temperature ascertained. It was then transferred to another glass jar 

 containing 500 c.c. of a freshly made solution composed of 475 c.c. of 

 sea-water and 25 c.c. of distilled water. At the end of an hour its 

 rate was again ascertained on the kymograph and it was transferred 



