122 



ACTINIARIA 



streaks. In the Actiniaria such a structure has not been observed before. Though a more extensive examination 

 of the filaments of Halcampa arctica is desirable, I am, however, able to state that the filaments of this species 

 at least indicate a structure like that of the filaments of the Zoanthids. The furrows and the ridges of the ciliated 

 streaks also here pass into similar furrows and ridges on the intermediate streaks which are also here sup- 

 ported by mesogloeal off-shoots. The nuclei in the lower part of the intermediate streaks look a little differ- 

 ent from those of the ridges. I therefore think that also here bands of the ciliated streaks are prolonged into 

 the furrows of the intermediate streaks. Still a control examination of this feature on better material is 

 desirable. The furrowed part of the intermediate streaks is, however, not as broad in H. arctica as in the 

 Zoantliids. It almost only includes the cun^ed part of the intermediate streaks, while at least half the inter- 

 mediate streaks, adjoining the median streak, are unfolded. The figure 14, PI. 2 shows a longitudinal section 

 of the intermediate streaks {is, is^ and of the ciliated streak {cs). The section has hit the filament a little 

 obliquely. On one side (downwa^rds in the figure) the unfolded intermediate streak {is) has been sectioned, 

 on the other side the sulcated part of the intermediate streak (/sj) is seen. The figure 15, PL 2 also shows 

 a similar section, a little more magnified, almost cutting through the apex of the wings of the filaments. 

 Remarks: The Halcampa-species, until now described, especially H.duodecimcirrata, arctica, chrys- 

 anthellum, arenaria and farinacea, are so very nearly related to each other that it is difficult to find any 

 good species-characters. Probably there are small differences between them, but in order to judge of the 

 constancy of these differences a closer examination is required. The nematocysts and spirocysts are of about 

 the same size as those of the mentioned species. If H addon's statement that only 6 mesenteries are fertile 

 in H. chrysanthellum, is correct, — a renewed examination of this point is desirable — this species is well 

 characterized. As my material of H. arenaria and farinacea is too poor — both species certainly belong to 

 the genus Halcampa as the sphincter is mesogloeal — I will not now discuss these species any further. Con- 

 cerning H. arctica and duodecimccrrata it is possible that we have to do with only one species having its habi- 

 tation proper in the Arctic Sea, where it reaches its largest size, but also distributed at the shores of Nor- 

 way and Sweden and the Eastern sides of Denmark right into the Baltic Sea, simultaneously becoming smal- 

 ler and smaller in size — the numerous specimens from the vicinity of Bomholm and Scania all were very 

 small. For the present it may be the best to retain these forms as different species. To which species Sars's 

 short description alludes, is difficult to decide with certainty. It is possible that his duodecimcirrata is iden- 

 tical with my arctica as a specimen from Ure dredged by Sars and examined by myself had rather richly 



