STUDIES ON REGULATION 



XI FUNCTIONAL REGULATION IN THE INTESTINE OF 



CESTOPLANA 



BY 



C. M. CHILD 

 With Twenty Text Figures 



This Neapolitan form which has served for other experiments 

 (Child '05a, '05b, '05c) is very favorable for the study of the intes- 

 tinal changes which occur during form-regulation. The intestine 

 in normal animals is almost black in color and since other portions 

 of the body are unpigmented is very distinctly visible in the living 

 animal. Moreover, the regulatory changes are extreme and in 

 some cases relatively rapid; and finally animals and pieces live 

 for months in clear water without food so that it is possible to 

 follow the intestinal changes during a long period. 



I THE TURBELLARIAN INTESTINE, ITS FUNCTIONS, AND FUNC- 

 TIONAL FACTORS INVOLVED IN ITS DEVELOPMENT AND REG- 

 ULATION 



This part of the paper aims to establish a general basis for 

 interpretation of the experiments and observations to be described 

 later. It precedes rather than follows the descriptive part because 

 it is important, as well as economical of time and space, to be able 

 to point out the bearing of the various experimental data, under 

 each head instead of postponing interpretation to a general sec- 

 tion where the chief points of the description must be reviewed. 



The basis of interpretation suggested here is, however, in part 

 the result of these and other similar experiments, not a precon- 

 ceived hypothesis with which the facts are to be brought into 

 accord. As will appear also, it is in line with previous suggestions 

 which I have made concerning the dynamic or functional char- 

 acter of form-regulation (Child '05a, '06a, '06b). 



The Journal of Experimemtal Zoology, vol. iv, no. 3. 



