The ability of the slipper limpet Crepidula fornicata L. to feed on suspended particles carried into the mantle cavity by cilia on the gill has attracted attention for many years since the feeding mechanism was described by Orton (1912). Subsequent studies were made on the possible origins of this mode of feeding (Yonge, 1928, 1938), and later Werner (1951, 1952, 1953, 1955, 1959) made more detailed observations on the mechanisms by which particles are retained by the animal. He showed that coarse particles are strained by means of a mucus filter covering the inhalant aperture to the mantle cavity, whilst the majority of the medium and fine particles are entangled by a second mucus filter secreted by an endostyle and which lies against the frontal surface of the gill (for review, see Jørgensen, 1966; Newell, 1970).