KTJNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63- N:0 2. 



49 



presents an interesting variety of aggregata. Already its external aspect is noticeable, 

 the test being provided with strong, coarse wrinkles, preventing the apertnres from 

 being easily distinguished. (Pl. 2, fig. 42.) The branchial sac is of typical struc- 

 ture. The gon ad is three-branched, the branches being long and irregularly curved 

 (fig. 45). The structure of the alimentary canal is characteristic to that variety. As 

 is shown from fig. 46 the intestine forms a wide S-shaped loop, the rectum is long 

 and sinuous. The stomach is of considerable length, spindle-shaped, of liver-brown 

 colour. Its external surface is qnite smooth, numerous vessels are visible, ramifying 



Text-fig. 4. Dendrodoa aggregata var. groenlandica. 



A. Transverse section through the stomach- wall showing the crystals. X80. 



B. Group of ery9tals. X450. 



in its wall. (Cf. fig. 46.) Externally no longitudinal folds are visible, internally they 

 are well-developed. 



Text-fig. 4 represents a transverse section of the wall of the stomach, showing 

 the folds internally and the smooth surface externally. When studying the section, 

 one is struck by the presence of masses of small round structures of light-brown 

 colour, crowded together and forming a thick layer around the whole stomach. As 

 far as one can judge from this material, they seem to be spherical crystals of radial 

 structure. They have not been observed in other forms of the species, but occur 

 in all eight individuals representing the var. groenlandica. The individuals agree also 

 in other respects. 



They have been collected at Sukkertoppen, West Greenland, bottom, clay; 

 depth, 60 fms. 



Dendrodoa lineata has been distinguished by the absence of longitudinal vessels 

 between the folds, four ovarian branches and wart-like processes of the test. The 

 characters of both the internal and external structure having proved to be constant, 

 the form lineata has been regarded, in the present paper, as a good species. 



The forms of Dendrodoa aggregata here treated of inhabit almost exclusively 



K. Sv. Vet. Akad. Handl. Band 63. N:o 2. 7 



