162 Puget Sound Marine Sta. Pub. Vol. 1, No. 14 



those of Shelford and Powers. These collections were made every 4 hours 

 out of the 24. They showed a marked increase in CO2 and a decrease in 

 Oo at midnight and at 4:30 A. M. Since the collections were not re- 

 peated the exact results are included here. Knudsen and Ostenfelt, ac- 

 cording to Murray and Hjort (15), found that diatoms absorbed much O, 

 in the dark; and with these operating in the same manner as the animals, 

 such differences are to be expected. 



5. Methods of Experimentation 



The fresh water in 1915 came from Trout Lake, 8 miles from the 

 station, the deep wells which supplied the town earlier having been aban- 

 doned. The lake is well supplied with fresh water animals and algae. 

 In 1915 the end of the lake nearest the town had recently been dammed 

 and some land covered with vegetation thus submerged. This led to con- 

 siderable decomposition in the lake and in the pipes, the water reaching 

 the station with a bad odor and no oxygen. An analysis showed the 

 following: — Oxygen .00 cc. per liter; carbon dioxide, free, 15.7 cc. per 

 liter, in carbonates 13.4 cc. per liter, in bicarbonates 13.4 cc. per liter; 

 alkalinity 120 parts per million; chlorine 286.7 parts per million; hydro- 

 gen sulfide (iodine method) 0.51 cc. per liter. The water used was aerated 

 and thereby the free carbon dioxide was reduced to 1-3 cc. per liter, the 

 cdor and hydrogen sulfide were removed, while the oxygen content rose to 

 about 5 cc. per liter. The water thus became essentially as it was before 

 leaving the lake. The fresh water experiments were conducted in this 

 water held at the same temperature as the sea water by being immersed 

 in a tank through which sea water flowed. 



The temperature of the water from which the animals of the Lamina- 

 rian and deeper belt were collected was about 11° C. The animals of 

 the shore which sometimes are left in small standing pools may be sub- 

 jected to as much as 24°-27° C. Animals from shallow water, especially 

 those from eel grass, are subjected to temperatures somewhat higher than 

 that of the other animals. All experiments were performed at 11.5°-13.0° 

 C, which was the temperature of the running salt water. 



Acidity was produced by adding enough hydrochloric acid ("jy) 

 to transform all carbonates to chlorides and give a small amount of free 



HCl. At the end of the experiment the water was titrated with {jj^J 

 sodium carbonate, methyl orange being used as an indicator. Alkalinity 

 was produced by adding (-^) sodium carbonate, phenolphthalein being 

 used as an indicator. 



