An Experimental Effect of Light on the Sponge, Oscarella

Abstract

THE spicule-less sponge, Oscarella lobularis, is an interesting form found on our shores and elsewhere, and presents a wide range of colour variation. Topsent (Arch. de Zool. Exp. et Gén. 3, iii., 1895) has recorded that Oscarella when found exposed fully to light is deep red, as when growing on the stem of the weed Cystoseira or on the sides of rocks, and brownish or even greenish-yellow when growing in dark situations, as on the under side of stones. At Plymouth, a similar range of colour variation is found, while colonies which are overgrowing the under sides of stones and extending over the edges show a development of red colour where the sponge is exposed to direct light.