The collection of Hydroidea obtained by this Expedition, was forwarded to me for examination in the summer of 1882, by Dr. MAX WEBER, of Amsterdam. I have found no new species in it, — a natural result of the number of Scandinavian and Arctic Hydroids that have been made known to us in late years, by MM. M. and G. O. SARS, ALLMAN, HINCKS, METSCHNIKOFF and others. But the present collection contains several species hitherto rare, it extends greatly the range of many that have formerly been reported from only one or two localities, and it contains also several well marked and peculiar varieties. It includes altogether 24 species from 12 stations, from various depths down to 170 fathoms. The annexed table gives the names of the species with the stations and depths at which they were found. The most prominent and luxuriant species are Sertularia gigantea, and Lafoëa fruticosa; — of which the former is common everywhere in shallow, the latter in deep water; most of the species are large and strong in comparison with specimens from farther south.