The Evaporation of Water from Helix Aspersa

Abstract

1. Data is presented which suggest that inactive specimens of Helix aspersa are able to regulate evaporative water loss from the mantle. 2. Evaporation is reduced following the cessation of glandular extrusion, by the concentration of solutes in partially dehydrated superficial mucus. 3. Methods are described for determining vapour pressure gradients across living and freshly killed mantle tissue and for calculating permeabilities. 4. Osmotic permeability measurements using isolated and intact body wall were made. 5. The permeability of regulating mantle tissue was 0.039 mg./cm.²/hr. per mm. Hg vapour pressure difference. Living body wall and freshly killed mantle were at least forty times more permeable to water. 6. Low permeability seems to be a unique property of living mantle tissue.