CO 2 IN RELATION TO REGENERATION IN PLANARIA. Ill 



of 18 C. As soon as #7-3 is reached in the first determination, 

 the tubes are opened, the pieces are returned to water and left un- 

 disturbed for the desired number of hours, i.e., at least long enough 

 as determined by the susceptibility method for disappearance in 

 large measure of the temporary changes following section. At 

 the end of this time the rate of pH change is again determined 

 for each lot under as nearly as possible the same experimental 

 conditions as the first determination. 



Fifteen such experiments were performed before the technique 

 used in the experiments recorded in Table I. was fully worked 

 out. In eight of these fifteen experiments the A -pieces showed 

 marked motor activity and a more rapid change in pH than the 

 C-pieces immediately after section, in three there was either death 

 of some of the pieces from drying or an error in weighing, and 

 in four none of these sources of error was involved and the result 

 were similar to those in Table I. 



Table I. gives the data for thirteen experiments, in all of which 

 the technique was as nearly as possible the same. The only 

 feature of the table which requires explanation is the column 

 'Time after section." The times given in this column are the 

 times of sealing of the tubes containing the animals in indicator 

 solution. The first time for each lot, "Immed.," i.e., imme- 

 diately, means simply that the pH determination was begun as 

 soon as possible after the pieces were sectioned. Since it requires 

 a half hour or more to cut lots consisting of forty to fifty A and 

 C-pieces, the time between section and sealing may be as much 

 as an hour for the pieces cut first and only a few minutes for 

 those cut latest. 



In eleven of the thirteen experiments recorded, 84 per cent., 

 the CO2 production of the C-pieces immediately after section 

 is about equal to, or greater than that of the A -pieces. As 

 regards the other two experiments, Nos. 7 and 8, in No. 7 three 

 C-pieces died during the first determination, and in No. 8, 

 motor activity occurred in the ^.-pieces, perhaps because of a 

 slight rise in temperature of the water in which the tubes were 

 kept. The second pH determination, begun at various lengths 

 of time ranging from nine to forty-two hours after section, shows 

 in every case a lower rate of CC>2 production in C than in A . 



