抄録
The spawning season of Anadara subcrenata ranges from the end of June to August in Nakano-umi, but the singe indivedual seems to discharge its reproductive substance for long time.
The first occurrence of the swimming young shell was known on 22nd of June from the collection of 2 indeveduals in my net. Since that time till 29th a few indivduals were seen every day, but since the tyhoon of 31st of July the swimming young shells increased to maximun nunber on 6th of August.
The main factor of the sudden increase of swinning young shells in the sea seemed to ascribable to the sudden decrease of the temperature and the specific grvity of the lower zone of the sea by the typhoon.
The swimming young shells were by far the most abundant at the zone deeper than 3 meters from the surface.
