Between the two layers of cells there is a semifluid matrix with needlelike spicules 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. Regarding the Nematocysts Unique stinging devices called nematocysts discharge threads to capture prey and fend off predators.
Some types release toxins that a painful to prey and swimmers alike.
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 jellylike mesoglea lies between the outer and inner body layers. Jellyfishes have abundant mesoglea helpful in providing buoyancy and in swimming.