HYDROIDA II IOI 



Sertularella polyzonias (L,inne) Gray. 

 1758 Seriularia polyzonias, Ljune, Systema naturae, ed. 10, p. 813. 

 1848 Sertularella polyzonias var. «, Gray, List of the specimens of british animals, p. 68. 



Upright colonies with irregularly branched monosiphonic hydrocaulus, no distinct main stem. 

 The branches are divided by oblique nodes into interuodia, each bearing a hydrotheca, turning alter- 

 nately to either side. The hydrotheca? are smooth or slightly wrinkled transversely, barrel-shaped, with 

 a somewhat expanded opening part; the opening margin has four low and broad teeth, between which 

 are attached the four triangular lid plates. The adcauline wall has a longer or shorter free part, 

 according as the hydrotheca diverges more or less sharply from the branch. The polyp has a well- 

 developed abcauline blind sack. 



The gonothecee proceed from close under the base of the hydrotheca;. They are egg-shaped, 

 deeply furrowed transversely throughout their entire length, and have four markedly prominent strong 

 teeth about the distally central opening. 



Forma typica: fine and low colonies. 



Forma gigantca (Mereschkowsky): large robust colonies. 



Material: 



Forma typica: 



Iceland: Bredebugt, depth 35 fathoms (transitional to forma gigantca). 



63°2o' N., 20°i4' W., depth 80 metres. 

 The Faroe Islands: 6 miles N. by W. of Store Kalso, depth 60 fathoms. 



Forma gigantca: 



"Ingolf" St. 127 66°33' N., 20°05' W., depth 44 fathoms 



Greenland: Akudlek — 30—60 — |labelled Sertularella polyzonias] 



Jakobshavn (depth not stated) 



Fgedesminde — - — 



.Store Hellefiskebanke (without further details) 

 — depth 32 fathoms 



Godthaab (without further details) [labelled Sertularella polyzonias] 



Davis Strait, 67°34' N., 55^29' W. [ — I 



Sukkertoppen on Boltcnia (depth not stated) 

 Kara Sea, "Dijmphna" [labelled Sertularella polyzonias]. 



Sertularella polyzonias is divided by many writers into two species, the gigantic arctic form 

 being regarded as a distinct species, Sertularella gigantea Mereschkowsky. Kirch en pauer (1884 p. 

 34) has already drawn attention to the existence of intermediate forms between the two, which cannot 

 show a single qualitative difference, the latter for instance, being distinguished merely by the fact 

 that all dimensions are harmoniously increased. The very fact that this form belongs to the arctic and 

 antarctic water layers, while the other is quite cosmopolitan, warns us to be careful about regarding them 

 as distinct species. Geographical studies on the variations of hydroids have shown (cf. Broch 1909, 



