. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. no HYDROIDA II The "IngolP brought back from several of its stations colonies of the same type described by Ssemundsson as Diphasia Waiideli. They are stiffly built, with a distinctly marked, often some- what darker and plainly segmented main stem. Eacli internodium has a pair of hydrothecse and a branch, directed alternately to either side, so that in these colonies, we have constantly two hydrothecse between two successive branches on the same side of the stem; of these two hydrothecse, the one (the lower) is situate
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. no HYDROIDA II The "IngolP brought back from several of its stations colonies of the same type described by Ssemundsson as Diphasia Waiideli. They are stiffly built, with a distinctly marked, often some- what darker and plainly segmented main stem. Eacli internodium has a pair of hydrothecse and a branch, directed alternately to either side, so that in these colonies, we have constantly two hydrothecse between two successive branches on the same side of the stem; of these two hydrothecse, the one (the lower) is situate in the corner by the branch. In the most extreme specimens of this variant group, we find single undivided branches. This variety is represented by a particularly pure type in specim- ens from the "IngolP St. 3 and St. 93. In these colonies, there is no pronounced fore or rear side as generally seen in Diphasia fallax. This must doubtless be taken in connection with the fact that the. 200 m. boom. iooo m. 2 ooo m. Fig. LIX. The distribution of Diphasia fallax in the Northern Atlantic. In the hatched regions a common occurrence in reported (-)- the variety spoken of in the text). most marked representatives of the variety are attached to a firm underlayer, stones or mollusc shells, and not, as is mostly the case with this species, to stems of other hydroids; they thus stand more perpendicularly, and consequently develope more symmetrically, whereas the ordinary colonies, being- fixed in a more horizontal position, find it better to develope more onesidedly, with an upturned "front". Among the numerous transition forms, it will here suffice to mention some specimens from "Thor" (65°52' N., 23°58' W.). They are very closely allied to the group of variants described as a distinct variety, but exhibit at the same time several of the characteristic features of the main species. The stem is not quite so marked as compared with the branches, albeit its darker
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