During a stay at Naples in the past winter, I became acquainted with a great number of Nemertini which had escaped my notice on a former occasion (1874), and of which I could have numerous specimens in different varieties thanks to the greatly improved methods of dredging and searching which are now practised in Prof. Dohrn’s splendid establishment. This enabled me to gain a better insight, not only in the anatomy of the group, but in the range of varieties, species and genera as well. The preliminary results of these researches are contained in the following pages.