no 



HYDRO1DA II 



The "Ingolf" brought back from several of its stations colonies of the same type described by 

 Ssemundsson as Dipliasia Wandeli. They are stiffly built, with a distinctly marked, often some- 

 what darker and plainly segmented main stem. Each internodium has a pair of hydrothecae and a 

 branch, directed alternately to either side, so that in these colonies, we have constantly two hydrothecae 

 between two successive branches on the same side of the stem; of these two hydrothecae, 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 "Ingolf 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 



60 



40 



20 



looom. 



20om. bucm. .._ looom. 



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" (6552' N., 2^^8' 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 brown colour helps 

 to bring it out; its segmentation is less prominent, and the branches proceed more openly and some- 

 what irregularly, with three, or more often four hydrothecae between two branches on the same side 



