Vol. VI. January, /poy. No. 2 



BIOLOGICAL BULLETIN. 



FORM-REGULATION IN CERIANTHUS, III. 

 THE INITIATION OF REGENERATION. 



C. M. CIIfLD. 



In the first paper of this series ('03^) the typical course of re- 

 generation in a cylindrical piece was described ; in the second 

 paper ('03$) some of the factors influencing the process of regener- 

 ation as a whole were discussed ; these papers have served to clear 

 the ground for a detailed analytical study of the process of re- 

 generation in Cerianthus in its various manifestations. In this 

 and following papers of the series various phases of this subject 

 will be considered. 



CHANGES IN FORM CONSEQUENT UPON SECTION. 



The reduction in size of the opening at the end of a cut piece 

 by the bending inward of the cut margins was described in its 

 simplest form in the first paper of this series. A somewhat more 

 general consideration of this peculiar process is necessary before 

 proceeding to the discussion of other points. 



Early in the course of my experiments upon Ccriantlnis it was 

 noted that in nearly every case, however the pieces might be cut, 

 the body-wall became rolled or folded in such a manner that the 

 opening into the enteric cavity resulting from the cut \vas much 

 reduced in size or was closed by approximation or contact between 

 different parts of the body-wall. The usual result of the infold- 

 ing is the complete removal of the entodermal surfaces from con- 

 tact with the external water, /. c\, the piece rolls up or closes in 

 such mariner that the entoderm is on the inside. For conve- 

 nience we may designate inrolling about a transverse axis as 

 transverse inrolling, and inrolling about a longitudinal axis as 

 longitudinal inrolling. 



At first glance this process appears much like an adaptive re- 

 action. In some cases it is almost as if the animal or part were 



55 



