The present author obtained three living specimens of megalopa from Sagami Bay by surface collection, in October of 1970. These larvae have been reared in the aquarium until moulted to the young crabs, which are identified to Hemigrapsus penicillatus. The adult crab is very common in japan, found usually on the rocky and muddy beaches as well as on the beach of pebbles on river-mouth. The larval features of these specimens have been observed and illustrated in this short report, comparing with the larvae of some other related crabs already reported.