Spongilla is a genus of freshwater sponge in the family Spongillidae. They are found in lakes and slow streams. Sponges of the genus Spongilla attach themselves to rocks and logs and filter the water for various small aquatic organisms such as protozoa, bacteria, and other free-floating pond life. Unlike marine sponges, fresh-water sponges are exposed to far more adverse and variable environmental conditions, and therefore they have developed gemmules as a means of dormancy. When exposed to excessively cold or otherwise harsh situations, the sponges form these gemmules, which are highly resistant "buds" that can live dormantly after the mother sponge has died. When conditions improve, the gemmules will "germinate" and a new sponge is born.