The aqueous methanolic extract of the marine worm (P. vancaurica tetradentata) was con centrated and poured into acetone. The precipitate showing feeding stimulant activity was dis solved in a small amount of water and poured into methanol. The methanol-soluble part was fractionated by ion exchange column chromatography. The neutral fraction thus obtained was active and rich in ninhydrin-positive components. The neutral fraction was further separated into 8 fractions by ion exchenge

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... hy. The most active fraction (Fr. J-5) contained three ninhydrin-positive substances which were identified as Gly, L-Ala and L-Val. Authentic specimens of the three amino acids and their mixture were assayed their activity at various con centrations, but they showed less stimulant activity than Fr. J-5, suggesting that other active substances should be contained in this fraction. From the ninhydrin-negative part of Fr. J-5 a fluorescent substance was identified by TLC on silica gel and this component may participate in the activity of Fr. J-5. It may reasonably be concluded from these results that the stimulant activity of P. vancaurica tetradentata is attributable for the Most part to Gly, L-Ala, L-Val and an amphoteric fluorescent substance.