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38 then are the most innocent, perhaps, of all others, they are more cruelly treated or used, than the most mischievous of wild beasts. "As the ephemerus abounds with useful lessons and moral precepts, so it affords sufficient matter for various speculations. It is engendered, grows to its bigness, and then generates, lays eggs, casts its sperm, grows old, and dies in the space of five hours. This short space comprehends the morning, noon, and evening of its life."

The species on which Swammerdam made his observations is the largest known, and is the Ephemera longicauda of Olivier (Encyclop. Method. Art. Ephemera.) In honour of the individual who made us so accurately acquainted with its history, Latreille subsequently named it E. Swammerdiana. It is not a native of this country, but occurs in the larger rivers of Holland, Germany, and France. About the same time, he investigated in a similar manner the history and anatomy of what he names the asilus or gad-fly, but which is a dipterous species of the modern genus Stratiomys, or chamæleon fly. His attention had been probably attracted to this insect, by the singular breathing apparatus of the larva, which consists of an anal orifice surrounded by a circle of diverging rays of beautifully feathered plumes. This singular structure, and the elegant appearance of the respiratory appendage, has caused it to be often described and delineated in modern