Euplectella suberea glass sponge, 19th-century illustration. These deep-sea animals have soft tissues in a tube made of silica. Here, the soft tissues are protruding from the holes in the silica tube. These sponges are filter feeders, drawing water through their tissues to filter out small particles of food. This drawing was made from several damaged specimens collected west of Gibraltar, between Pernambuco and Bahia, South America, during the Voyage of HMS Challenger (1872-1876). This scientific expedition, organised by the Royal Society, spent four years surveying the world's oceans.