[Determination of sexual polyps in hydractinia echinata. A biological and chemical analysis]

1. In contact with tissue of blastostyles buds of gasterozooids and regenerating gasterozooids will transform into blastostyles. The inductive capacity within blastostyles decreases from apex to base. Hypostomes with gasterozooid-like properties, which may frequently occur at the basal cut of isolated blastostyles, will transform into the homologous blastostyle structures in a sequence following that inductive gradient. 2. The spontaneous transformation of regenerating gasterozooids into reproductive polyps, which could be observed during wintertime, can be increased by α-ketoglutarate (5×10^-4 M/L), isocitrate (5×10^-3 M/L), colcemide (3×10^-6 M/L) and, with only weak effect, by CO₂ increased top=2-4% Atm. With increasing dosages optimum lines could be determined. The transformable state of regeneration starts when tentacle formation takes place. By applying α-ketoglutarate in stepwise decreased concentrations 75 ppc transformations have been obtainable. 3. If similarly applied in graduated dosages chromatographically separated blastostyle ectraxts also increase the rate of transformation. The causative factor is to be found in the range of fractions that also contains the tentacle-inducing substance.