HYDROIDA II 



I 4 I 



species is rare off the west coast of Greenland, and appears to be altogether lacking on the east coast. 

 In Iceland waters, it is frequent on the west coast, and in Damnark Strait, and is also common on 

 the east coast; common on the ridge between Iceland and the Faroe Islands, and around the latter 

 Islands. In the North Sea, it is one of the most common species, and occurs also as a common form 

 along the coast of Norway right up to the North Cape. 



Thujaria sp. aff. hippuris Allman. 

 From the "Ingolf" St. 24 (63°o6' N., 56°oo W., depth 1199 fathoms, 2,4°) we have some colonies 

 of a Thujaria, the identity of which cannot be determined with certainty. The colonies are slenderly 

 pinnate, with branches openly set; the stem is very slightly pronounced, and in colonies 

 10 cm. high shows incipient spiral coiling at the top; the broad plane of the branches 

 here assumes a horizontal position, while elsewhere it is always vertical. The branches 

 form almost a right angle with the stem. The stem has two rows of hydrothecse, and is 

 divided into internodia bearing as a rule four branches, two to either side, alternately 

 placed. There are three hydrothecie between two successive branches on the same side 

 of the stem, the lowest in the branch angle. The branches are irregularly segmented, 

 with two to five, or rarely more, hydrothecse on the internodium. The hydrothecae are 

 set in two rows on the branches; their plane of symmetry coincides with the broad plane 

 of the branches; they are alternately placed on the slightly zigzag branches (and stems) 

 and separated, in the same row, by intervals exceeding the length of the hydrotheca 

 (fig. LXXVI). The hydrothecse are deeply imbedded, and have a short free distal part 

 of the adcauline wall; the length of this is at the outside half the opening diameter. 

 The hvdrotheca opening is round, with an even margin, and no indication of teeth or TAu/aria sp.aM. 



~. , r hippuris. Part 



sinus; there is a large round opercular plate abcauhnally fixed. The colonies are untor- o{ a branch 

 tunately all sterile, with no indication of gonangia formation. (X 40). 



The colonies described appear in their general features to present some considerable likeness to Thu- 

 jaria hippuris Allman, but are even more slender and with more widely set hydrothecse than noted for the 

 species in question (cf. Allman 1874, p. 473, pi. 45 fig. 2, and Kr am p 1913, p. 26). The shape of the colony in 

 Thujaria hippuris is very nearly the same as in Thujaria thuja. The largest colonies in the material show 

 that the present species would also probably be of the same form when fully grown; the pinnate arrangement 

 of the colonies, and the lack of secondary ramification in the branches, can therefore only be regarded as 

 juvenile characters. The slight specific differences otherwise existing in the genus Thujaria call, how- 

 ever, for caution. The hydrotheca; in the colonies here concerned are not entirely imbedded, as is 

 otherwise stated to be the case with Thujaria hippuris, but have a very short free distal part on the 

 adcauline side; there is also a wider interval between the hydrothecse in the same row, and the bran- 

 ches are bent slightly zigzag fashion. These points render it somewhat doubtful whether the spe- 

 cimens in question really belong to Thujaria hippuris, and the identity cannot be determined with 

 certainty until the variational conditions of the species in question have been further elucidated. The 

 enormous depth at which the colonies occur is very interesting, and will possibly serve to explain its 

 extremely slender form. 



