Colloidal Properties of the Mesogloea in Species of Leucosolenia

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Abstract
Oscular tubes rapidly collapse and disperse in isotonic potassium nitrate solution, the cells dissociating and rounding off, and the mesogloea softening and swelling. Reasons are given for regarding the action as a direct one on the mesogloea and intercellular ‘cement’. Transference of the collapsing tubes to sea-water, or isotonic calcium chloride, results in an immediate stiffening of the mesogloea, and the swollen cells form characteristic processes which are best seen after the cells have been in the nitrate solution for an optimum period depending on the temperature. They are not formed after treatment with M/100 potassium cyanide. The action of other isotonic salt solutions is briefly described. When a comparison is made of the times taken for the tubes to become plastic, the ions respectively used fall into three series which are the same as those found in regard to the dispersiveness of certain hydrophilic organic colloids. The experiments provide evidence that the mesogloea is secreted by the choanocytes or by the amoebocytes close beneath them, and that the secretion stiffens into a firmer gel as it passes into the spicule zone. The degree of firmness also varies apparently according to the health of the tube. The action of distilled water and acidified sea-water are described. After the spicules have dissolved the tube still retains its shape and much of its support can thus derive from the mesogloea. The relative functions of the mesogloea and the spicules are briefly discussed.