Blood Volumes, Blood Distribution and Sea-Water Spaces in Relation to Expansion and Retraction of the Foot inBullia(Gastropoda)

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Abstract
1. The expansion and retraction of the foot has been studied in the prosobranchiate sandy-beach gastropod, Bullia. 2. In Bullia the foot is capable of an unusually great expansion, but this is not dependent upon an unusually large volume of blood. 3. Radiographical investigations have shown that on retraction blood flows direct from the pedal sinus to the visceral sinus system without passing through the heart, kidney or gill. 4. Investigation of the jets of water produced on retraction has shown that in the expanded animal the visceral region within the shell is surrounded by sea water. 5. The roles of blood movement and of contraction of the columella muscle, and also various other aspects of the circulation, are discussed.