HYDRO1DA II 



zoo trt. doom. ......_...,., i ooo m. rooom. 



Fig. XXII. Finds of Halecium minutum in the Northern Atlantic. 



small sympodial parts, normal in appearance, arise from enormous rhizocaulome formations instead of 

 from creeping stolons. This, as Kramp also points out, places the question of growth conditions as 

 generic character in a remarkable light; and what is worse, it shows us that the shape of the colony 

 can even in specific limitation only be applied with great discretion, a point which has also been 

 noted here under the heading of Lafoeid(F. Kramp thus supports my supposition (1909 p. 153) that 

 the colonies which Jaderholm (1907) mentions from the Bering Sea under the name of Halecium 

 tclcscopicum should more probably be ascribed to Halecium minutum. 



Halecium minutum is an arctic species which has doubtless a considerable distribution in the 

 Polar Sea, but which is often confused with others, and especially with Halecium tenellum, as is also 

 clearly evident from the list of investigation material given above. Apart from the Bering Sea, the 

 species has been recorded at Spitzbergen, the Murman coast, east and north coasts of Iceland, northern 

 east coast of Greenland, and several places along the west coast; finally also Fraser (1913 p. 168) 

 has met with it at Nova Scotia, on the Canso Bank. The species penetrates but very slightly into 

 the boreal region, as far as can be seen from the finds made up to now. 



Family Plumulariidae. 



The hydrothecse are small, sessile, approximately radially symmetrical, one side partly or en- 

 tirely fused with the branches (tubes); the diaphragm is somewhat asymmetrical. The large polyps can 

 practically speaking never be drawn entirely into the hydrothecse. The sarcothecse are two-chambered, 



7* 



