The Contractility and Healing Behaviour of Pieces of Leucosolenia complicata

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Abstract
The behaviour of isolated pieces of Leucosolenia complicata confirms that this sponge is contractile. The pieces first curl up owing to a contraction of the internal epithelium, which can exert a tension in one direction (transverse) more than the other at right angles. The contraction is slow because it entails a redistribution of the supporting mesogloea. It is abolished by 5 minutes' treatment with distilled water. Healing next involves the formation of ‘healing membranes’. Each membrane consists of two epithelia with athin layer of mesogloea in between. The membranes arise either as an outfolding of the internal epithelium or from the cut edges of the wall, and they spread between the edges so that the tubular form of the olynthus is regained. Their spread is due to the maintenance of tension in the membrane, coupled with the shrinkage of the remainder of the piece. Pieces from which the internal epithelium has been brushed away shrink rapidly and become saddle-shaped, indicating that the dermal epithelium also is contractile. No important differences are noticeable when the healing behaviour takes place in equal parts of sea-water and isotonic magnesium chloride, which suggests that the behaviour is not under the control of a nervous system. A discussion is given on the elements responsible for the contractility of the internal epithelium. It is probable that the porocytes are connected beneath the bases of the collar-cells, and are the contractile cells concerned.

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