56 



ZOANTHARIA 



N. W. of Bergen 30—200 fm. M. Olsson 1873, 1878; 90—200 fm. O. Mattson 1880; 100—150 fm. 

 M. Udd strom 1880 R. M. 



N.N.W. of Bergen 90—200 fm. M. Uddstrom, G. Nilsson, M. Olsson 1880 R. M. 



North Sea M. Uddstrom 1880 R. M. 



North Sea north edge of the Fisher Bank 100—160 fm. B. Olsson R. M. 



Size: The colonies form large aggregates sometimes of the size of a clenched fist and almost 

 always fixed on sponges (1 spec, on an Ascidian). In the contracted state the polyps of the largest 

 colonies (PI. I, fig. 16) reach a length of 19 cm. and a breadth at the base of 1 cm. In most of the 

 colonies the polyps are however considerably smaller. 



Colour. In alcohol the colonr varies from dirty yellowish (PI. I fig. 10) to dirty grayish or 

 pure white (PI. I fig. 9 — 11). The dirty gray colour is generally predominant. 



External appearance. The polyps form colonies often of large dimensions, which are attached 

 to large sponges. The ccenenchyme is fairly thin and extensive and sometimes forms narrow out- 

 shoots, on the end of which new polyps are formed (PI. I, fig. 9). A single colony, which by the way 

 was not quite typical, was found on an Ascidian. The polyps generally sit quite close to each other, 

 but sometimes the intervals between may be larger, especially when the ccenenchyme forms string-like 

 outshoots. Even when the tentacles are completely covered by the body-wall, the polyps are generally 

 considerably higher than broad. The breadth is however very considerable, greatest at the base and 

 tapering upwards; sometimes the distal part maybe somewhat swollen, especially in greatly contracted 

 polyps, though never so much as in P. dixoni and anguicomus. Otherwise, the polyps vary much in 

 size, as can be seen from figs. 9— n on PI. I, but there is no doubt that we are only dealing with 

 one and the same species. The body-wall is more or less wrinkled especially in the larger specimens. 

 The capitular furrows are generally distinct and reach up to 18—21 in number. The oesophagus is 

 of moderate length. The siphonoglyphe is distinctly marked, the hyposulcus developed but rather 

 short and does not attain to half the length of the oesophagus. 



The ccenenchyme as well as the polyps is incrusted with sand-grains and sponge needles, to 

 which are sometimes added a few foraminifera. The sand-grains are generally predominant, but in 

 some cases the sponge-needles occur in quantities. The incrustation is not so strong as in P. anguicomus 

 but is very variable. Sometimes polyps are also found which are very little incrusted. 



Anatomical structure. The ectoderm of the body-wall is very high and continuous and 

 contains nematocysts with greatly twisted thread of two different kinds, either large 41— 46/i long 

 and 17—18^ broad or small 24 p long and 12 — 13 fx broad. The number of capsules is variable 

 but the smaller ones are always more numerous than the larger and the proportional occurrence of 

 both kinds of capsules seems to be always the same. When the polyps are not strongly expanded, 

 the mesoglcea is somewhat thicker than the ectoderm. It is provided with numerous cells, cell-islets 

 and lacunae and a well-developed encircling sinus. The cell-islets and lacunae are generally numerous 

 (PI. 7, fig. 5), sometimes however scarce. The lacunae are here and there in distinct connection with 

 the ectoderm and encircling sinus. As a rule the latter is interrupted at a few places by mesoglceal 

 parts and narrow. Sometimes, however, I have found fairly strong mesoglceal bridges together with 

 a broader encircling sinus at the bases of the mesenteries, while the connecting canals between 



