, . ZOANTHARIA 



44 



does not differ from that of the other Zoanthidae. He has even made a mistake with regard to the 

 arrangement of the mesenteries, as can be seen from his fignre showing the grouping of the mesenteries 

 where he has not observed the couple of mesenteries forming the macro-type. This is for example 

 seen from the fact, that fig. 4 Tab. 24 shows 18 macro-mesenteries, whereas fig. 3 only has 16, which 

 according to the later number of macro-mesenteries is in agreement with the description. As I think 

 it superfluous to point out Danielssen's mistakes in detail, I shall in the following pay no attention 

 to his anatomical description of this species, but only describe the structure as I found it in a type- 

 specimen from Bergens Museum, supplemented by examination of the material collected by Nordgaard 

 and during the Ingolf Expedition. 



The body-wall is more or less incrusted with sand-particles, here and there sponge-needles 

 occur and sometimes also foraminifera. The incrustation reaches a longer or shorter distance into the 

 mesogloea, which however is not so much filled with the incrustation that its structure cannot be seen. 

 The ectoderm is continuous with a generally thin but sometimes thicker cuticle on which are fixed 

 particles of detritus Though comparatively broad the ectoderm is considerably thinner than the 

 mesoglcea and is, as usual, most developed in the capitular region. In the greater part of the body- 

 wall there is a fairly frequent occurrence of nematocysts with greatly twisted thread (length 31 — 41 /i, 

 breadth 12 fi). The mesoglcea is thick and contains small cells of more or less frequent occurrence 

 PI. 6 fig. 2). Ectodermal canals are also found though very seldom. On certain sections of one of the 

 type-specimens I observed some elongated cells, the long outshoots of which were parallel to the 

 margin of the mesoglcea. They lay either very far into the mesoglcea or near its inner margin. If 

 the position of these cells were not variable, they might possibly be considered as the remnants of a 

 ring-sinus, which however can hardly be the case, as these elongated cells are not of constant occur- 

 rence. An encircling sinus is absent. The entoderm is not large and several times thinner than the ectoderm. 



The sphincter is entodermal and in transverse sections deep semicircular folds may be seen 

 (fig. 5, PI. 3). Where the sphincter breaks though the mesenteries one may, as in all Parazoanthus- 

 species, obtain sections which if viewed externally give the impression that the sphincter is mesoglceal, 

 but this is not the case. 



The structure of the tentacles and the oral disc is in agreement with other Zoanthidae. The 

 ectoderm of the tentacles contains numerous spirocysts and many 14— 17 /* long, typical thick- walled 

 capsules. The longitudinal musculature of the tentacles is fairly strong. The mesogloea of the tentacles 

 is also incrusted. 



According to the more or less contracted state, the oesophagus is rounded, oval-shaped or more 

 flattened. The siphonoglyphe is fairly distinct, but the mesoglcea is only somewhat thicker than in the 

 other parts of the oesophagus. The ectoderm of the oesophagus is considerably larger than the thin 

 mesogloea. The difference in height between the ectoderm of the oesophagus and the siphonoglyphe 

 is on the other hand quite inconsiderable. Owing to the small development of the oesophagus I have 

 not been able to make glycerine-preparations. 



Mesenteries. Of 4 specimens examined 2 had 32, 1 had 36 typically arranged mesenteries. The 

 4th specimen with 34 mesenteries had 9 macro and 7 micro-mesenteries on the one side, while on the 

 other side there were 18 mesenteries irregularly arranged. This side namely was partly arranged 



