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
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