Sponges without Collared Cells

Abstract

MY friend Mr. Maurice Burton has given his reasons for believing that there are many siliceous sponges which have no oscula, pores, or flagellate chambers, and nourish themselves through the general surface¹. His evidence does not seem to prove the existence of such structure other than, as previously recognised, where degeneration of tissue has followed the onset of unfavourable conditions; and there we have no knowledge that subsequent nourishment takes place. It is difficult to understand how a solid finger, 1 cm. wide, of amæboid animal cells in jelly, can be nourished and grow by soakage of solubles from sea water if it can be done, it is not clear why sponges or metazoa came into existence. Loisel (1898², p. 220) considered his experiments proved that a Spongilla was nourished by adding to its water the filtered juice of another Spongilla but this does not show that Mr. Burton's hypothesis is tenable, for there is little organic matter dissolved in ordinary sea water. Further, the spongilla which was nourished possessed collar-cells and currents, and exposed to the water an internal surface of ingesting protoplasm twenty or a hundred times the area of its horny external skin.