HYDROIDA II loi 



Sertularella polyzonias (Liniic) Gray. 

 1758 Scrtidaria polyzonias^ Linne, 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 monosiphouic hydrocaulus, no distinct main stem. 

 Tiie branches are divided by oblique nodes into internodia, each bearing a hydrotheca, turning alter- 

 nately to either side. The hydrothecse are smooth or slightl\- 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 sharph' from the branch. The polyp has a well- 

 developed abcauline blind sack. 



The gonothecae proceed from close under the base of the hydrothecse. They are egg-.shaped, 

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

 teeth about the distally central opening. 



Forma typica: fine and low colonies. 



VoxvcL2i gigantea (Mereschkowsky): large robust colonies. 



Material: 



Forma typica: 



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



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., 2005' W., depth 44 fathoms 



Greenland: Akudlek ' — 30—60 — [labelled Sertularella polyzoinas\ 



Jakobshavn (depth not stated) ■ \ — — — ] , 



Egedesminde — - — 



Store Hellefiskebauke (without further details) 

 — — depth 32 fathoms 



Godthaab (without further details) |labelled Sertularella polyzouuis\ 



Davis Strait, 67°34' N., 55"29' W. | — — — I 



Sukkertoppen on Bol tenia (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 giganlea 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 merel\' 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, 



