CO 2 IN RELATION TO REGENERATION IN PLANARIA. 113 



As regards the two records for the same lot, the A -pieces show 

 in general a slightly lower CO 2 production in the second period 

 than in the first, or in some cases about the same. Experiment 

 9, however, shows a slightly higher rate in A during the second 

 period, this being due probably to the slightly higher water 

 temperature during the second period. In the C-pieces the rate 

 is distinctly lower, in many cases much lower in the second period 

 than in the first. Differences in time of five minutes between 

 the records of two lots made at the same time mean only that 

 the two were barely distinguishable as different. Differences 

 of this mangitude between the two records of the same lot can 

 mean no more than that the rate is essentially the same in the 

 two periods. Differences of ten minutes or more are however, 

 unquestionably significant and differences of much greater 

 magnitude appear in the table. 



The table show's then that immediately after section there 

 is in some cases a slight temporary increase in CO 2 produc- 

 tion in the ^.-pieces and a very marked increase in the C-pieces, 

 that is to say the differences and changes in CO 2 production 

 following section are in general parallel to the differences and 

 changes in susceptibility. The objection may be raised that 

 the differences in CO 2 production are less than would be expected 

 from the stimulation by section, but when it is remembered that 

 there is no reason to believe that the alimentary tract shares in 

 this stimulation except locally at the cut surface and that the 

 pieces do not undergo motor activity during the determination 

 this objection has little weight. As a matter of fact the close 

 parallelism between the data on CO 2 production and those on 

 susceptibility indicates that even as regards the temporary 

 changes following section of pieces, susceptibility is in some degree 



1 During the first determination in No. 7 three C-pieces died. When the 

 determination was repeated the following day, two C-pieces, which had been cut 

 with the others but not used before, were added to lot C and one piece was removed 

 from lot A to make weights as nearly as possible equal. Only two extra worms 

 had been sectioned, therefore three pieces could not be added to take the place of 

 those dead. 



2 Slight motor activity occurred in the A-pieces during the first determination. 



3 Here the temperature was half a degree higher in the second determination 

 than in the first, and the A -pieces show a slightly increased rate in the second 

 determination. Footnotes for Table I. 



