REGENERATION IN ISOLATED AND FUSED PIECES OF CLAVA LEPTOSTYLA

¹ Department of Zoology, University of Michigan, Ann Arbor, Michigan, and Mt. Desert Island Biological Laboratory, Salisbury Cove, Maine

1. Observations have been made on regeneration of isolated pieces of hydranths of Clava leptostyla, including the hypostome and tentacle-bearing region, the gonosome and the stalk.

2. Stalks isolated in 50% and 80% sea water underwent accelerated dedifferentiation as compared with controls in normal sea water.

3. The distinction is drawn between (1) "primary" regeneration, meaning the differentiation of missing oral or basal ends under the influence of the existing apico-basal gradient and (2) "secondary" regeneration, the delayed development of new hydnanths from attached hydrorhiza or dedifferentiated tissue.

4. Primary regeneration at the apical end of isolated stalks usually occurred after anchoring the stem against 2% agar with a fine glass rod thrust through the middle or the basal end. Regeneration was inhibited, however, if the apical end was pinned.

5. Primary regeneration of apical ends was repressed by fusion of pieces of 2 hydranths in apical-to-apical juxtaposition or by fusion of an apical piece between the basal ends of two other hydranths.

6. Apical regeneration likewise failed to occur in fusions of two stalks in apical-to-basal or basal-to-basal orientation.