Always to be found in Drake's Island Tank.* Very abundant during the summer, but diminishing innumber during the winter months. It has been described by O. MÜller (22), Ehrenberg (6), Stein (31), Dujardin (5), Claparede and Lachmann (3), under various names, but their descriptions may be regarded as only of historic interest. The later observations of Gruber (13), Cohn (4), and Entz (8) aremore detailed, and Lebedew (17) has given the fullest account of the animal. Kent (16), Biitschli (1), and SchewiakofE (27) have only short notices.