They also trap suspended food particles in their microvilli collars and transfer the food to amoeba-like cells in the matrix. Between the two layers of cells there is a semifluid matrix with needlelike structures for support. Sponges reproduce sexually and asexually. Sperm are released into the surrounding water to be picked up by a nearby sponge and directed to the egg within the matrix. The zygote develops into a free-swimming larva.
Cnidarians are radial, tentacled animals that live mostly in the seas.
Unique stinging devices called nematocysts discharge threads to capture prey and fend off predators. An outer epidermis covers the body, and an inner gastrodermis lines the digestive cavity. A nerve net running through both layers coordinates the animal's response to stimuli. Some jellyfishes also have sensory cells and contractile cells. A jelly-like mesoglea lies between the outer and inner body layers.