[Control of the Morphogenetic Steady State in the Polyps of Hydractinia echinata : II. Chemical analysis].

1. In homogenates of all tissues, including the hydrorhiza, thermostable factors are present capable of evoking heteropolar regeneration. Isolated heat-stable nematocyst toxins lead, in proper concentrations, to the same symptoms. A heat-labile substance with analogous effects is traceable in extracts of the nematocyst-free proboscis. 2. Extracts of gastrozooids and of blastostyles supply a substance which brings about the development of supernumerary tentacles. This substance, which was detectable only after separation of the extract by column chromatography, is digested by trypsin and seems to have a molecular weight in the range of peptide hormones. Heteropolar head-formations, which beyond that have been evoked after the first Chromatographie step on DEAE-Sephadex A-50, remained within the normal range of frequency after further purifying the substance with Sephadex G-25. 3. Basic proteins, extracted with 0.57 M NaCl at pH 6.8, and purified by Reineckeprecipitation and by chromatography, block any regeneration and evoke spasmic contractions. By means of discelektrophoresis eight (at pH 8.2) resp. twelve (at pH 4.3) electropositive proteins have been detectable. 4. Material of the hydrorhiza retains, when freeze-dried, its inductive capacity. 5. In the discussion of the results concerning the apical inducers, the gradient hypothesis is confronted with the concept of an induction sequence. Furthermore, it is explained, that the testing system chosen here and in similar works does not prove the existence of hypostomeinducing ("polarizing") factors, since not only specific inducers but also inhibitors interfering with the dominance system will give rise to heteropolar regeneration.