FORM-REGULATION IN CERIANTHUS, VI. 



CERTAIN SPECIAL CASES OF REGULATION AND THEIR RELATION 



TO INTERNAL PRESSURE. 



C. M. CHILD. 



In this paper are described certain regulative phenomena of 

 interest both from a descriptive point of view and because they 

 appear to offer further evidence upon the problem of the role of 

 internal water-pressure in regulation. At present I can see no 

 other satisfactory interpretation of these cases than that based 

 upon internal pressure. In any case, however, they are interest- 

 ing modifications of the typical course of regulation and as such 

 deserve mention. 



THE ORAL REGENERATION OF OBLIQUE PIECES. 



Pieces with oblique ends are obtained by sectioning the body 

 at various angles to the principal axes as indicated in Fig. I. 

 Such pieces show a very marked difference in rapidity of regener- 

 ation on the different parts of the oblique cut surface, regenera- 

 tion being most rapid on that part which represents the region 

 nearest the oral end of the parent body and least rapid on the 

 opposite side. This difference is due in part to the fact discussed 

 in my second paper ('03^), viz., that the rapidity of regeneration 

 always decreases with the increasing distance of the regenerating 

 surface from the oral end of the original animal. But the differ- 

 ence in the rapidity of regeneration on the different parts of the 

 oblique surface is considerably greater than that between control 

 pieces with transverse cut surfaces at corresponding levels. It 

 follows from this that some other factor in addition to the differ- 

 ence of level is concerned in the result. 



Before proceeding to the description of experiments it should 

 be said that the possible significance of oblique pieces was not 

 fully recognized during the course of my experiments, therefore 

 my study of such pieces was less extended than it would other- 

 wise have been. The data are sufficient, however, to show 



