ACTION OF ALKALIES ON PLANARIA. 329 



and then in water made alkaline to the desired degree by the ad- 

 dition of sodium or ammonium hydroxide. The general method 

 of procedure was that described by Hyman ('190). The species 

 used was Planaria dorotocephala. Each experimental lot con- 

 sisted of about 150 worms, 18-20 mm. long; these were selected 

 from the laboratory stock and placed in a 500 cc. Erlenmeyer 

 flask, in which they remained for a considerable time, being used 

 in a number of experiments. They were fed in these flasks at 

 intervals. At least three or four days were allowed to elapse after 

 each feeding before the worms were used for experiment in order 

 to avoid the increased respiratory rate consequent upon feeding 

 (Hyman, '19^). The worms were fed sufficiently often to avoid 

 any effects of starvation. From time to time new lots of worms 

 were selected. 



The water used was well water, an analysis of which is given 

 by Hyman ('25). The alkaline water was prepared by adding 

 enough sodium or ammonium hydroxide from stock solutions to 

 raise this water to the desired alkalinity. The pH was determined 

 with phenol red and thymol blue indicators by comparison with 

 standard sets. At alkalinities greater than pH 8.6 a precipitate 

 of calcium carbonate formed in the water. While there was no 

 indication that this precipitate in any way affected the results, it 

 was thought best to avoid it. This was done either by allowing 

 the precipitate to settle and then decanting or by using carbonate- 

 free water. This was prepared by adding 2 cc. concentrated HC1 

 to eight liters of well-water and bubbling air through the water 

 for 24 hours or more. That the rate of oxygen consumption of 

 Planaria dorotocephala is the same in carbonate-free as in un- 

 treated well-water had previously been determined by Hyman 

 ('25) and was verified in the present experiments. 



Throughout each respiratory test, the flasks containing the 

 worms and the blanks were kept in a large water bath at a tem- 

 perature of 20 C. 0.5. This was covered during the test. 

 This darkening of the flasks together with the fact that the worms 

 were kept continuously in the flasks was sufficient to eliminate 

 movement. The worms remained very quiet throughout the 

 oxygen consumption tests and the results cannot be ascribed to 

 any differences in motor activity. 



