the breathing organs of animals which obtain their oxygen from water. In fishes, the gills consist of cartilaginous or bony arches, attached to the bones of the head and furnished on the outer, convex sides with a multitude of fleshy leaves, of fringed, vascular fibers, resembling plumes, which are, when healthy, of a red color. The water is admitted by gill-openings, and as it circulates through the plume-like parts of the gills, the oxygen is extracted from it. The crustaceans, the mollusks and the amphibians in certain portions of their lives are furnished with gills.