1. The eggs of Echinus esculentus contain about 1.5% glycogen and 20% lipid (dry weight).

2. Whole eggs produce lactic acid under anaerobic conditions, the maximum rate of production being 0.15 pi. lactate/hr./mg. eggs (dry weight) at 20° C.

3. Lactic acid production is inhibited by fluoride, iodoacetate and phenylmercuric nitrate.

4. The supernatant from centrifuged egg homogenates prepared in M/50-phosphate buffer, pH 7.5, (‘extract’), was found to be a satisfactory glycolytic enzyme preparation.

5. The production of lactic and pyruvic acid by such extracts is greatly stimulated by the addition of glycogen, cozymase and adenosine triphosphate, (‘complemented extracts’).

6. Complemented extracts glycolyse glucose and fructose with greater facility than glycogen or starch. With glucose or fructose as substrate, the rate of formation of lactate and pyruvate may reach 1.7 µl./hr./mg. eggs (dry weight) at 20° C.

7. Complemented extract glycolysis is inhibited by fluoride, iodoacetate, phenylmercuric nitrate and phloridzin.

8. Active extract glycolysis occurs with the following glycolytic intermediates as substrates: glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, hexose diphosphate and phosphoglyceric acid.

9. It is concluded that the sea-urchin egg (E. esculentus) possesses a typical glycolytic system, whose activity is comparable with that found in other invertebrate tissues.

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