Il6 HARRIET L. ROBBINS AND C. M. CHILD. 



except for the fact that both lots were fed with beef liver three 

 times before weighing and pH determination, the first two feed- 

 ings being on successive days, the third after an interval of one 

 day. In the first five experiments of Table III. worms from 

 the first five experiments of Table II. were used, but in smaller 

 numbers because of the increased weights after feeding, partic- 

 ularly in the regenerated animals. In Table III., as in Table II. 

 the "large" animals are those which have not undergone regener- 

 ation and represent as nearly as possible the animals from which 

 the pieces were taken, and the "regenerated" animals are those 

 which have developed from the pieces. Table III. agrees with 

 earlier work (Child, '190) in showing that the rate of change in 

 pH is increased in all animals by feeding after a period of star- 

 vation, but it also shows that the difference in rate between the 

 regenerated and the large animals persists after feeding. Here 

 again the data on CC>2 production agree with the results of the 

 susceptibility method (Child, '15, Chap. IV.). Data on oxygen 

 consumption recently published by Allen ('19) and by Hyman 

 ('196) also agree with these results. 



ADDITIONAL DATA. 



Table IV. includes a number of miscellaneous experiments 

 of some interest. 



In the course of regulatory development an outgrowth of 

 new tissue occurs at anterior and posterior ends of each piece. 

 All the facts indicate that this tissue, which forms the new 

 head and posterior end, is more or less embryonic in character 

 when it arises and possesses, at least at first, a higher rate of 

 metabolism than the remainder of the piece. In order to deter- 

 mine whether the higher rate of CO 2 production in regenerated 

 animals is due solely to the more intense activity of this new 

 tissue or whether the rate is also increased in other parts, the new 

 heads and posterior ends were removed from regenerated animals 

 leaving only the so-called old or less extremely altered tissue of 

 the middle regions. Lots of such pieces were then compared 

 with lots of equal weight of freshly cut ^4-pieces (Fig. i) and of 

 animals 16-18 mm. like those from which the pieces were taken, 

 the heads being removed from these large animals in order to 



