The Malpighian Tubules of the Larva of Heptagenia Interpunctata, Say.

The Malpighian tubules of the Ephemerida, both of the larva and the imago, have been described by a number of workers; as far as I have been able to ascertain there has not been any paper published in which one can find a detailed description of their structure either in the immature or the mature stage of these insects. These tubules in the May-flies assume, according to different observers, many forms; several have been described as filiform, others as similar in a general way fa the ones described in the present paper. From both descriptions and figures it has been shown that in several species of May-flies the tubules are short and bent or coiled, or, in some species they assume a spiral form. The more detailed descriptions have shown that in many species each tubule consists of a distal, thicker and secretory, portion from which a thinner tube passes and enters indirectly or directly into the intestine. Tubules opening separately have been figured by Dufour (3) and Drenkelfort (2) but in most species it has been shown that they open into several common receptacula and that these open directly into the digestive tract; Leue (8) and Vayssiere (13). The short account of most of the quoted authors gives but a meager description; many, however, show the two above mentioned parts of each tubule and the spiral or twisted shape is commonly mentioned or figured. From these various accounts the one which most closely resembles the tubules of Heptagenia interpunctata is the figure given by Vayssiere (13) of Heptagenia longicauda.