534 STUDIES ON RESPIRATION. XVI 



merits using a different species {Strongylocentrotus purpuratus) and 

 found no increase when sufficient NaCl was added to increase the 

 specific gravity of the sea water by about 50 per cent. They found 

 an increase in the case of unfertilized eggs (as did Warburg) but they 

 attributed this to the fact that the hypertonic solution causes the for- 

 mation of a membrane. Unfertilized eggs which had already formed 

 membranes (as the result of treatment with butyric acid) showed no 

 increase in hypertonic solutions. Measurements by the writer of the 

 specific gravity of the solution described by Loeb and Wasteneys 

 showed it to be about 1.036, while that of the most concentrated solu- 

 tion used by the writer was much above this. 



Using the method of measuring respiration described by Osterhout,^ 

 the writer undertook to measure the production of carbon dioxide 

 while the osmotic pressure of the medium was changed sufficiently to 

 be highly hypertonic on the one hand and quite hypotonic on the 

 other. The marine alga Laminaria agardhii was used as the basis of 

 most of the work. The results with Ulva lactuca were quite similar to 

 those with Laminaria. 



It was found that the carbonates of sea water interfered with the 

 measurement of the carbon dioxide produced, arid to overcome this 

 difficulty the chamber containing the Laminaria was lined with filter 

 paper dipped in artificial sea water (van't Hoff's solution, containing 

 no carbonates). No other liquid was added but the chamber was so 

 small that a very slight amount of evaporation sufficed to saturate 

 the air. The change thereby produced in the concentration of the 

 solution in the thallus was negligible and the cells may be regarded 

 as bathed in a solution of constant concentration during the experi- 

 ment. Uniform normal respiration was also obtained when the Lami- 

 naria was immersed in artificial sea water or placed in the respiration 

 chamber without the addition of liquid or moistened filter paper. 



The pieces of Laminaria were selected from fresh material as 

 nearly uniform in size as possible and placed in the container. The 

 normal rate of respiration was then obtained for each piece of tissue 

 before it was treated. The pieces were then removed and exposed 

 to the hypertonic or hypotonic solution for 5 minutes, at the end of 



^ Osterhout, W. J. V., /. Gen. Physiol., 1918-19, i, 17. 



