Treatment of the embryos of sea urchins with glyoxylic acid results in the appearance of luminescence which is indicative of the presence of biogenic monoamines. At the early stages of development (cleavage divisions, blastula, gastrula) the histochemical method reveals a tryptamine-like substance which is first found in all embryonic cells and later is concentrated mainly in the cells of the primary gut and ciliary bands. At the stages of prism and pluteus there appear neuron-like cells containing dopamine. The inhibitors of monoamine oxidase and neurotoxins reliably increase the histochemical reaction to monoamines only in late embryos which suggests a change in the properties of monoaminergic systems in the course of embryogenesis.

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Indolylalkylamine determination was performed on the eggs and embryos of six species of sea urchins, using several fluorometric techniques, including the fluorescence of a substance itself and the fluorescence of its condensation products after treatment with orthophthaldialdehyde and ninhydrin. The serotonin-like substance of sea urchin embryos as well as of adults was shown to consist of at least two components, of which the major one is tryptamine or its derivative with a substituting group at aminonitrogen. Further, serotonin was found to be present at all developmental stages investigated, although at much lower concentrations. The results of this study suggest a regulatory role of ''prenervous'' tryptamine in the early embryogenesis of the sea urchin.

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