THE MANNER IN WHICH THE SPONGE CLIONA BORES IN CALCAREOUS OBJECTS

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Abstract
Boring in shells and calcite crystals was investigated, using a new type of reconstitution culture. No free acid was detected, and no detectable quantity of calcium was put in solution by the sponge. However, acid action is indicated by restriction of boring to calcium carbonate. Conchiolin is penetrated with difficulty. Cells in contact with the substratum form a reticulum of fine pseudopodia and filaments; a corresponding pattern of lines is etched into the calcite. The areas so marked out are the same size and shape as the fragments discharged by the sponge. These fragments are identical whether from shells or calcite crystals; their faces are curved but their edges sharp. Apparently the cytoplasmic filaments insinuate themselves into calcite by secreting minute amounts of acid, and undercut fragments which are carried through the sponge parenchyma to excurrent canals.

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