ZOANTHARIA 



57 



these broader canal parts are narrow. This variation in structure of the encircling sinus is however 

 probably due to different states of contraction in the polyps, which may be concluded from the fact, that 

 the more abnormal encircling sinuses had a thicker mesogloea and were more contracted, while the 

 polyps with a more typical encircling sinus were expanded. But the fact also, that both kinds of 

 encircling sinus may be found in the same colony, goes to show, that we are not dealing with a variety. 

 The encircling sinus contains the same kind of nematocysts as the ectoderm of the body-wall. 



The sphincter is more developed than in P. anguicomus and dixoni. While the muscular furrows 

 in the distal part are large and semicircular, they lie on the other hand closer to each other in the 

 proximal part (PI. 3, fig. 6), though this cannot always be quite distinctly seen. The bases of the 

 mesenteries are broken through by the sphincter, a condition that seems always to be present in the 

 Zoanthidae with entodermal sphincter. In this region the sphincter has thus the appearance of being 

 mesoglreal. 



The ectoderm of the tentacles has the usual structure. The spirocysts are very numerous; 

 further, there are numerous thick -walled capsules (length 22 fi) and very few capsules of the same kind 

 as in the body-wall. 



The ectoderm of the oesophagus is fairly high and deeply furrowed or smooth according to 

 the varying state of contraction and provided with numerous, ca. 24 / long, nematocysts. The ectoderm 

 of the sulcus is somewhat thicker than in the oesophagus, while the mesogloea is thicker. 



The number of mesenteries varies between 36 (34?) and 46, but the latter is only seldom found 

 and even specimens with 42 mesenteries seem to be scarce. Of the 14 specimens closely examined one 

 (a small yellowish specimen from the same locality as the colony figured on PI. I, fig. 10), has 34, possibly 

 36 mesenteries, 3 had 36, 4 had 38, 3 had 40, 2 had 42 and i had 46 mesenteries. Below the oesophagus 

 the macro-mesenteries reach only a short way into the coelenteron (in specimens not sexually mature). 

 The longitudinal muscles are distinctly marked but form no or very faint furrows; the parieto-basilar 

 muscles are weak. The distribution on the body-wall of both kind of muscles is fairly considerable. 

 The micro-mesenteries are fairly well-developed, in the aboral part of the oesophagus several times 

 longer than the entoderm of the body-wall is high. 



The glandular tract contains numerous thick-walled capsules with distinct basal part to the 

 spiral thread. They are somewhat broader at the one end and 17 22 jj. long and 5^ broad. Further, 

 it contains capsules with spiral thread of the same appearance as in the body-wall; they seem always 

 to be scarce and have a length of 36 43^ and a breadth of 17 18/*; smaller capsules are also found. 

 Sometimes I have not found any of the large capsules in the filaments. 



The polyps are dioecious. 



In the ccenenchyme, which is more or less incrusted, the canals lie nearer to the under than 

 the upper side. 



For systematic remarks see under P. anguicomus. 



Parazoanthus anguicomus (Norm.) Haddon & Shackl. 



PI. I, fig. 19; PI. II, fig. 21. 

 Zoanthus sulcatus Bowerbank 1867. Proc. Zool. Soc. p. 351. 



anguiconms Norman 1868. Shetland Report. Rep. Brit. Assoc. p. 310. 



o 



The Ingolf-Expedition. V. 4. 



