From the time of Aristotle many naturalists have desired, and a large number have attempted, to discover something about the breeding and development of the common eel, but until the present time it has remained a baffling mystery. At last the mystery is to a great extent penetrated; the larva of the eel has been discovered, and turns out to be a creature which was known before. Until the present year absolutely nothing was known of the history of the eel between the disappearance of the parents in the sea in autumn, and the disappearance of the young transparents elvers in early spring. Professor Grassi and Dr. Calandruccio have now discovered that one of the larval forms called Leptocephali is the larva of the common eel. This form was described and distingushed as Leptocephalus brevirostris, but it was not suspected that it belonged to the eel.