MEDUSA. I. 



93 



7) Lat 6i47' N., Long. 729' W., west of the Faeroe Islands. August i5th 1895. "Ingolf. - 



2 specimens, one of which is 10 mm wide with 32 tentacles; the gonads (female) are short and thick. 



Br i tish Isles: 



8) Lat 5948' N., Long. i23' W., south end of the Shetland Islands. July 22nd 1905. Depth 

 85 m. "Thor" stat. 122 (05). 2 specimens, one large and one middle-sized. 



9) Lat. 5736' N., Long. 7O5' W., Little Minch, west of Scotland. May 27th 1908. Depth 90 m. 

 Young-fish trawl, 65 m wire. "Thor" stat 8 (08). - - 2 specimens, the largest of which is 10 mm wide 

 with mature female gonads, 3 mm long. 



The largest specimens, found by Browne at the British coasts, were 21 mm in diameter and 

 had 39 tentacles. Among the specimens from Iceland here mentioned several appear to be of more 

 considerable size (up to 25 mm) and, particularly, to possess a larger number of tentacles (up to 58). 

 In all other regards the specimens agree completely with the British Phialidium hemispharicum, so 

 that I do not hesitate to refer them to the same species. It seems quite natural that this species 

 might be found off the southern coasts of Iceland, where the hydroid Campanularia johnstoni* is fairly 

 common (according to Saemundsson 1911 and Broch 1918). 



The fully expanded tentacles are 23 times as long as the diameter of the bell (according to 

 my observations from Plymouth). The tentacular bulbs are fairly broad, spherical, owing to the high 

 development of the ectoderm on the lateral sides of the bulb. The ectoderm is likewise fairly highly 

 developed on the adaxial side (Plate V, fig. 3). The lumen of the bulb is actually somewhat laterally 

 compressed. Plate IV, fig. 14 shows a section through a marginal vesicle of this species. The 

 marginal vesicle is spherical, half-way inserted on the margin of the bell. There is, as a rule, 2 mar- 

 ginal vesicles between every successive pair of tentacles, though in younger specimens there is usually 

 but one; in large specimens there are not seldom 3 marginal vesicles between two successive tentacles. 



In specimens from Iceland the number of tentacles may amount to 58 (this number has been 

 found in 3 specimens). Table XI presents a tabular view of the number of tentacles in 29 Icelandic 

 specimens of different sizes. The calculation of the average numbers of tentacles is based on the exact 



Table XI. Number of tentacles in specimens of different sizes of 

 Phialidium hemisphcericutn from Iceland. 



Diameter 



Number of tentacles 



' During my stay at Plymouth in 1914 1 confirmed the observation of Browne, that Campanula johnstoni is the 

 hydroid corresponding to Phialidium hemiipharicum. 



