ZOANTHARIA 



The parieto-basilar muscles are weak, and as far as I have been able to see the longitudinal and 

 parieto-basilar musculature does not extend onto the body-wall or only very little. 



The filaments have the usual structure. The glandular tract contains fairly many, often curved, 

 uniformly broad nematocysts with greatly twisted thread (length 22 26/z, breadth about 7/4 Further, 

 it contains numerous thick-walled capsules about 17^ long. 



The species is dioecious. In most of the polyps ovaries or testes were found though at a fairly 

 early stage. 



Isozoanthus magninsulosus n. sp. 



PI. i, fig. 7. PI. 6, figs. 4-5. 



Occurrence: 64 24' N., 28 50' W. 788m. Bott. temp. 3-5. Ingolf Ex. St. 10. i colony. 



Dimensions in the contracted state. Length of the largest polyp 0-6 cm., breadth 0-3 cm. 



Colour in alcohol: dirty yellowish-brown. It may possibly have absorbed this colour from a 

 brown piece of paper covering the stone on which the colony was fixed, and which coloured the alcohol. 



External appearance. The only colony of this species in the collection consisted of 8 larger 

 and smaller polyps placed fairly close to each other and separated by a large flat and very thin, band- 

 like coenenchyme (PI. i fig. 7), attached to a stone. The polyps are cylindrical not elongated, with 

 distinct capitular forrows. All the polyps were retracted so that no tentacles were visible, the upper 

 margin was rounded. The polyps as well as the ccenenchyme were incrusted with numerous foramini- 

 fera, giving the colony a granulated appearance. The oesophagus is very short, the siphonoglyphe 

 distinct with well-marked hyposulcus. 



Anatomical description. The ectoderm of the body-wall is fairly high, continuous and in 

 the lower part of the polyp provided with fairly numerous and uniformly broad nematocysts about 

 34 n long and 13 // broad with greatly twisted thread. In the capitular region they seem to be wanting 

 but are replaced by small egg-shaped capsules like those in the filaments (length 12 14^, breadth 6^). 

 The mesoglcea is more than twice as thick as the ectoderm and like this incrusted with numerous 

 foraminifera and some few sponge-needles. The incrustation is mostly present in the outer half of 

 the mesoglcea but may often reach further into this. The part of the mesoglcea which is not incrusted 

 contains numerous cell-islets of larger or smaller size (PI. 6, fig. 5). The smaller as well as the larger 

 of these are often in connection with each other, thus forming a lacunae-system which is mostly 

 observed in the lower part of the body (PI. 6, fig. 4). A section through the mesogloea of the body-wall 

 has therefore quite a different appearance from /. multinsulosus , where such lacunae-systems are only 

 seldom found. In sections of / multinsulosus the cell-islets are consequently as a rule round or oval 

 whereas in /. magninsulosus they have a more irregular appearance owing to their connection with 

 each other. The large islets (the lacunae) are also considerably larger in / magninsulosus than in 

 /. multinsulosus. In spite of the presence of a fairly well-developed lacunae-system one cannot speak 

 here of any defined encircling sinus. The entoderm is thin and slightly pigmented. 



The sphincter has the same structure as the other Isozoanthus species described. 



The ectoderm of the tentacles contains numerous spirocysts and fairly many thick-walled nema- 

 tocysts (length 17 ig//). The mesoglcea of the tentacles is often iucrustated. 



