DURING the forty years which have elapsed since the first two deep-sea nemertines were taken by the Challenger Expedition, a few examples have been collected by various other expeditions, but deep-sea nemertines have never been other than rare. Prof. Brinkmann, whose monbgraph on pelagic nemertines has recently been issued (Bergens Museums Skrifter. Bd. iii., No. 1, 1917, 194 pp., 16 plates), has, however, had a rich collection at his disposal, chiefly from the Michael Sars Expedition, so that he has been able to investigate the structure of most of the species described. He has also subjected the previously known species to careful revision, and concludes that five of them are so imperfectly described that they must be labelled as “uncertain.” The rule that the single type specimen of a species should be kept intact is, in the opinion of the author, unsound, for the external features often give little help to the systematist, and therefore investigation by means of serial sections is indispensable.