CO 2 IN RELATION TO REGENERATION IN PLANARIA. 1 05 



A few experiments similar to those recorded below were per- 

 formed by Child from time to time during several years past, 

 and these experiments, although they brought to light certain 

 difficulties as regards technique and were too few in number to 

 constitute conclusive evidence, indicated very clearly that the 

 differences and changes in susceptibility following section and 

 after regeneration are paralleled by differences and changes in 

 rate of carbon dioxide production. A more extensive investi- 

 gation of the subject by another person was desirable, and this 

 was undertaken by Miss H. L. Robbins in candidacy for the 

 degree of M.S. The data tabulated in the present paper are 

 those obtained in this investigation. 



The special technique for the different experiments is described 

 in the following sections, but the general technique used in 

 connection with the colorimetric method is very similar to that 

 employed in the study of CO 2 production during starvation 

 (Child, '190). The weighing of the animals or pieces is the 

 most difficult feature of the preparation, since the presence of 

 superfluous water introduces an error in weight, and since 

 weighing must be done as rapidly as possible to avoid injury or 

 death from drying. After considerable practice, involving 

 repeated weighings of the same lots and determination of the 

 length of time which could be allowed without injury for drainage 

 on filter paper and exposure to the air while weighing, a satis- 

 factory method of procedure was developed, and this was fol- 

 lowed in all the tabulated experiments. The container was 

 first weighed and both container and weights were left on the 

 balance pans : next weights equal to the estimated weight of the 

 lot of worms or pieces were placed on the weight pan in order to 

 reduce the time necessary for weighing the animals: the worms 

 were then brought together at the tip of a funnel of well washed 

 filter paper, drained for a certain length of time, transferred on a 

 slightly vaselined scalpel blade to the container and weighed, 

 each of these operations being performed in as nearly as possible 

 the same length of time in each case. Equal or approximately 

 equal weights of the lots to be compared were used (see tables). 

 For the colorimetric estimations the Hynson Westcott and 

 Dunning H ion outfit with phenolsulphonephthalein as indicator 



