II.-HYDEOID ZOOPHYTES. 



By Sydney J. Hickson, M.A., F.R.S., Professor of Zoology in the Victoria 



University of Manchester; and 

 F. H. Gravely, B.Sc, Research Scholar in the Victoria University of Manchester. 



(4 plates.) 



The collection of Hydroid zoophytes made by the ' Discovery ' Expedition proved 

 to be remarkably rich and interesting. At the first inspection there seemed to be 

 but few species, and these (with the exception of a few solitary forms of Lampra) 

 were large, ramified and gorgonia-like in consistency ; but a careful examination of 

 these large colonies soon revealed other species of epizoic habits which rapidly 

 increased in numbers as our investigations proceeded. In the end the number of 

 distinct species was twenty-five, or about twice as many as we expected to find. 



The large colonies of Halecium arhoreum support Perigonimus antarcticus, 

 Stylactis halecii, Campanularia everta, C. laevis, Campanulina, and Halecium 

 tenellum. 



Perigonimus antarcticus supports Campanulina A., Eudendrium insigne, and 

 Lafoeina longitheca. Eudendrium insigne was also found on a specimen of the 

 Alc'yonarian genus Ceratoisis. Sertularella plectilis and Campanulina B. are 

 attached to a colony of Campanularia verticillata. 



Of the twenty-five species only two — Obelia geniculata from the Auckland 

 Islands, and Dictyocladium fuscum from Coulman Island — were found outside the 

 limits of McMurdo Bay and the edge of the great ice barrier. In other words, 

 twenty-three of the twenty-five species represent the hydroid zoophyte fauna of 

 the most southerly limit of our knowledge of marine zoology. Two species — 

 Lampra microrhiza and Plumularia glacialis — were found only at the east end of 

 the barrier. 



It seems probable that the part of McMurdo Bay from which these specimens 

 came is covered with a continuous sheet of ice for the greater part of each year 

 and in some years has no open water. There is good reason for believing that 

 the great ice barrier is afloat, and consequently the few specimens obtained by the 

 Expedition at the east end of the barrier may represent samples of a fauna that 

 extends for some distance under the barrier towards the South Pole. 



We may regard this collection of Hydroid zoophytes as the representatives of 

 a sub-glacial fauna, and subject to the condition that larvae or free swimming 



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