HYDROID ZOOPHYTES. 31 



Genus campanulina. 



The genus Campanulina was instituted by Professor E. van Beneden for a species 

 that is known to produce one of the medusse of the genus Pkialidiam. The 

 hydrosome stage is characterised by the conical hydrotheca closed by an operculum 

 formed of convergent segments of its margin and by the conical hypostome. 



The specimens obtained by the ' Discovery ' have all the important characters 

 of the hydrosome thus described, and so have the specimeiis described by Dr. Hartlaub 

 (9: pp. 10-11; PI. I., figs. 8-9) under the name Ca^npanulina helgicse, from within 

 the Antarctic Circle. 



The absence of the gonophores in both specimens rendered it impossible for us 

 to determine whether they are or are not phanerocodonic. -Even if they had proved 

 to be adelocodonic, however, they should in our opinion be still retained in the 

 genus Campanulina, as the case of Perigonimus antarcticus may serve as a warning 

 that the setting free of the medusae is not a character that can be used as 

 absolutely diagnostic of a genus when applied to these sub-glacial species. It is 

 interesting to note in this connexion that Mr. Hodgson (12 : p. 397) states that 

 Phialidium medusae were abundant in McMurdo Bay. 



Campanulina A. 



Locality. — McMurdo Bay, February 20th, 1902 ; 5-20 fathoms. 



A single colony of this delicate little hydroid was found growing over a stem 

 of Halecium arboreum and over the Perigonimus antarcticus which encrusts it. 



Hydrosome. — The hydrocauli are slender (0 • 05 mm. in diameter and • 5-1 mm. 

 in length)", more or less clearly marked throughout with spiral lines, and very 

 occasionally branched. They arise from a creeping filamentous hydrorhiza. 



The perisarc at the distal ends of the hydrocauli gradually dilates to form the 

 " ovato-conic " hydrothecse, 0'4 mm. in length by O'l mm. in diameter. The 

 hydrotheca itself is very thin and evidently very flexible. Its margin is deeply cleft 

 to form about eight triangular flaps (0 • 1 mm. in length), which can close together 

 to form an operculum. It is difiicult to determine with any certainty the exact 

 number of these flaps, as they are extremely thin and transparent. 



The hydranths, when contracted, completely fill the hydrotheca^. The hypostome 

 is conical and surrounded by a single circlet of about twenty tentacles, • 2 mm. 

 in length. 



Gonosome. — Unkn own . 



Campanulina B. 



iom%.— McMurdo Bay, February 20th, 1902 ; 5-20 fathoms. 

 A single small colony of this form was found on Campanularla verticillata 

 (var. grandis). 



