I02 



HYDROIDA II 



1913, 1914) that the dimensions ma\- here quite commonly become coarser within the same species as 

 the temperature decreases. In Sertuhirclla pnlyzonias forma gigantca, this common law has been fol- 

 lowed to an extreme, while the transition forms are comparatively few. That they exist, however, 

 is plainly evident from the present material, where in particular certain colonies from Jakobshavn, 

 Greenland, and all those from Bredebugt take up a doubtful intermediate position. 



Vox\\\2igiganira (fig. LIV) is a typical arctic (and antarctic) character form, only exceptionally capable 

 of penetrating into the boreal region. It is extremely common in West Greenland waters, and is also 

 known from East Greenland; occa.sionally also from the north coast of Iceland. Forma /^v/>/r^/, on the other 



■"• 200 m. _ 600 m, (ooom. , I 000 m 



ImK- LIV. l'"ind,s of Si-rtuiaiella polyzonias forma typka • and forma gigantca + in the Northern Atlantic. 

 In the hatched rej^ions the literature notes a common occurrence of the forma typua. 



hand, is cosmopolitan, and occurs also, albeit less frequently, in arctic waters. In the boreal area, it 

 is particularly numerous in the eastern parts. Both forms belong to the middle parts of the littoral 

 region, and rarely move down into the deep sea region. 



Sertularella Gayi (Lamomoux) Hinck,s. 

 1821 Scrlularia Gayi\ Laniouroux, Exposition methodique des genre . , . p. 12, pi. 66, figs. 8—9. 

 1868 Sertularella Gayi, Hincks, A History of the British Hydroid Zoophytes, p. 237, pi. 46, fig. 2. 



Upright, irregular doubh' pinnate colonies with distinctly prominent pohsiphonic main stem 

 and main branches. The outer branches are almost regularly pinnately branched often with their minor 

 branches secondarily ramified. The outer branches arc divided by indistinct oblique joints into short 

 internodia, having on their distal half a large hydrothcca; the hydrothecte are directed alternately to 



