no 



HYDROIDA II 



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

 Ssemnndsson as Diphasia Waiideli. They are stiffh' built, with a distinctl\- marked, often some- 

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

 branch, directed alternately to either side, so that in these colonies, we have constantl\- two hydrothecre 

 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, tliere is no pronounced fore or rear side as 

 generally seen in Dipliasia fallax. This must doubtless be taken in connection with the fact that the 



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 consequentl)- devclope 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 

 distmct variety, but exhibit at the .same time several of the characteristic features of the main species. 

 The stem is not cpiitc 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 hydrothecx- lietween two branches on the same side 



