ZOANTHARIA 25 



red annulus." In the preserved state most of the specimens were dirty-coloured light brown. Some of 

 the specimens were grayish e. g. those from Altenfjord. The colony taken during the Michael Sars 

 Expedition was black with incrusted, small, black sand-grains and the colony originating from Iceland 

 Ofjord was even darker than is generally the case with this species. 



The external appearance has been well described by Danielssen, who has also given 

 some rather good drawings of the external appearance of the colonies. The species forms free, unfixed 

 colonies of 1 — 6 seldom more polyps connected with each other by a small tube-shaped ccenenchyme, 

 which is generally so inconsiderable that the polyps seem to grade smoothly over from one to the 

 other (see fig. 14, 17 PI. I). The more developed polyps are narrow at the base, but expand gradually 

 towards the distal part, so that the animal has its greatest breadth in the capitular region. The small, 

 not fullgrowu polyps approach the cylindrical shape. Sometimes the polyps are provided with cross- 

 furrows, which undoubtedly have only been caused by contraction. The capitular region has generally 

 quite distinct ridges and furrows. The number of furrows varies considerably according to the size 

 of the polvps. Danielssen states that the species has 18 capitular furrows, here they vary between 

 14 and 15 in small specimens and in the large between 16 and 20, and in one polyp I have even 

 counted up to 22. But generally the majority seem to have 18 furrows. Of 116 specimens 42 had 18 

 capitular furrows, 26 had 16, 17 had 17, 9 had 19, n had 20 and 1 specimen 22. Of the smaller 

 specimens 14 polyps had 15 capitular furrows and 5 had 14. On the majority of the small specimens 

 the capitular furrows were however so indistinct, that the number could not be determined with any 

 certainty. The body-wall is more or less rough owing to the greater or less incrustation. 



The tentacles are arranged as usual and seem to correspond in number with the mesenteries. 

 The oesophagus is short with a well-marked siphonoglyphe and a fairly long and broad hyposulcus. 



The anatomical structure has also been described by Danielssen, but on several points 

 incorrectly, as e. g. with regard to the arrangement of the mesenteries, which does not differ from that 

 of the other Zoanthidae. The ciliated streaks on the macromesenteries however have been observed 

 by Danielssen who gives a comparatively good picture of them (fig. 5, Tab. 22 Danielssen, 1890). 

 But on the other hand the arrangement of mesenteries and the length of the filaments on fig. 4, Tab. 22 

 of the same work are not in agreement with the reality. Some anatomical details are also given by 

 Haddon & Shackleton (1891). 



The ectoderm of the body-wall is fairly high, continuous and contains nematocysts with twisted 

 thread (length 24—30^, breadth 10— 12 /t). They are equally broad and common except in the capitular 

 region where they are scarce. The ectoderm is provided with a distinct cuticle, on which particles 

 of detritus are attached. According to the state of contraction of the animal, the mesoglcea may be 

 thin or very thick, but is several times thicker than the ectoderm. It is provided with fairly numerous 

 cells with long outshoots, whereas cell-islets only very seldom occur (pi. 5, fig. 4). Sometimes the latter 

 may be found at the base of insertion of the mesenteries but as a rule they are not present at these 

 places, a fact I have ascertained by means of a large number of sectioned specimens from different 

 localities. 



Haddon and Shackleton state (1891 p. 635), that on the specimens sent them by Daniels- 

 sen there was "a well-marked lacuna in the mesoglcea at the base of the insertion of each mesentery." 



The Ingolf-Expedition. V. 4. 4 



