(Halichondria panicea), member of the class Demospongiae (phylum Porifera), so called because of the way in which it crumbles when handled. H. panicea is a common sponge that encrusts hard substrata and seaweed on the shore and in shallow subtidal regions. Varying in colour from dark green to light yellow, it is frequently found in shaded crevices or under overhangs. Its surface is characterized by numerous conical protuberances, each with a hole at the top. Rhythmic beating of whiplike hairs (flagella) situated on the inner body wall draws water in through minute pores in the body surface. Oxygen and food particles are extracted from the water, which is then driven out through the holes at the top of the conical protuberances.