CARBON DIOXIDE PRODUCTION IN RELATION TO REGENERATION IN PLANARIA DOROTOCEPHALA

1. The colorimetric estimation of CO₂ production shows that the changes in CO₂ production following section in pieces of the body of Planaria dorotocephala run parallel with changes in susceptibility. Immediately following section CO₂ production is markedly increased in pieces cut from near the mouth region, while in pieces from regions near the head it is only slightly if at all increased. These changes are temporary excitations following section and disappear after a number of hours.

2. The development of a new individual from a piece is accompanied by a very considerable increase in CO₂ production which involves not only the new outgrowths at the two ends of the new animal but the "old" parts as well. This increase in CO₂ production is found both before and after feeding is resumed following the development of the piece. In these respects also the changes in CO₂ production parallel changes in susceptibility, both series of data indicating that the animal developing from an isolated piece becomes in the course of this development, physiologically younger than the animal from which the piece originated.