FACTORS AFFECTING TERMINAL GROWTH IN THE HYDROID CAMPANULARIA

¹ Department of Zoology, Indiana University, Bloomington, Indiana, and the Marine Biological Laboratory, Woods Hole, Mass.

1. When terminal growth rate was measured for stems of well-fed colonies of the hydroid Campanularia flexuosa for a period of 60 days, it was found that this rate is constant for about ten days, becomes progressively slower for the next 10 to 15 days, and then remains constant.

2. Isolated sections of stems of different ages differ one from another both in respect to the time required for the production of additional terminal hydranths, and in their ability to produce hydranths rather than free stolons. In general the same experimental groups which most readily produce hydranths following cutting produce them at fairly high rates.

3. Older levels of stems are in general less efficient in the rate of terminal hydranth production and in the ability to produce hydranths rather than free stolons. Not all of the results can be explained on the basis of an effect of aging. The possible role of inhibitors and of differences in efficiency of circulation must be considered.