Sexual reproduction in euglenoid flagellates is poorly known. The most recent report appears to be by Mignot from 1962 in a species of the rather unusual heterotrophic genus Scytomonas. We recently came across a paper by Biecheler from 1937, in which she describes sexual reproduction in a species of Euglena. Biecheler observed both fusion of isogamous cells and formation of cysts, but she was unable to study meiosis. The paper has, however, had little impact and is rarely mentioned in modern textbooks (we, too, were unaware of its existence). However, because Biecheler’s publications are generally characterised by very high quality, we feel that this paper should gain much more recognition. In addition, the method Biecheler used, and which unexpectedly induced sexual fusion in Euglena, may be usable in other flagellate groups to investigate the generally rarely reported phenomenon of sexuality. We have therefore translated Biecheler’s paper from the French to (1) make the general phycologist aware that sexual reproduction does indeed occur in this group of flagellates and (2) stimulate further research on sexual reproduction in flagellates in general by using Biecheler’s method and, if successful, investigate which factors induce sexuality.