ZOANTHARIA 



35 



External appearance. This species forms larger or smaller colonies, sometimes almost of 

 the size of a hand (the colonies dredged off Umenak Fjord). The polyps are connected with each 

 other by a flat, rather thick coenenchyme with a fairly well developed net-work of entodermal canals. 

 The polyps are either placed close to each other as in the Umenak material or emerge from the 

 ccx-nenchyme at greater intervals. They are cylindrical in shape especially in the longitudinally expanded 

 specimens, in the more contracted the middle part becomes somewhat narrower than the capitular 

 region especially. The length is generally at least double the breadth. On contracted polyps the distal 

 margin is rounded not truncate. Daniels sen states however that "when the polyp is retracted the 

 uppermost extremity appears truncated but with a little depression in the middle." As far as I can 

 see, this is not the case but a specimen of E. danielsseni found in the same sample as E. glaciates had 

 this shape, so that Danielssen's description was probably in this regard taken from that species (cf. 

 E, danielsseni}. The capitular furrows are distinct and vary in number. The greatest number observed 

 by me was 28 the smallest 16, the latter in a small specimen. The polyps taken near the coast of 

 Greenland, which generally were considerably larger than the Norwegian ones, had also as a rule a 

 larger number of capitular furrows. In 15 of the first named specimens I counted the following number 

 of capitular furrows 20, 20, 20, 20, 20, 21, 21, 22, 23, 23, 23, 25, 27, 28. Five type specimens had 16, 18, 18, 

 20, 20. Specimens from Alteiifjord have 17, 17, 18, 18, 20, 20, 20, capitular furrows. That the number of 

 furrows may also be high in the Norwegian forms may be seen from the fact, that I found among 

 them a specimen with no less than 52 mesenteries. The incrustation, which consists almost exclusively 

 of sand interspersed with a few sponge-needles, is not very strong and restricted to the ectoderm and 

 the outer part of the mesoglcea. The oesophagus has the iisual appearance lengthwise. The siphonoglyphe 

 is distinct with a well-marked, though not very long hyposulcus. 



Anatomical description. The ectoderm of the body-wall is high and sometimes as thick 

 as the mesoglcea; it is continuous, but may at times show a slight tendency to become discontinuous, 

 and is provided with a thin cuticle. The nematocysts of the ectoderm consist partly of large nema- 

 tocysts with greatly twisted thread (length 2634^, breadth 10 12 p) partly of thick-walled capsules 

 (length i9//), which however occur in small quantities. 



The mesoglcea is thick, sometimes thicker on one side than on the other. In the distal part 

 it contains fairly many cells, often provided with long outshoots (PI. 4, fig. 6). Further, there is a 

 sparse occurrence of cell-islets of moderate size, which however are more numerous in the Umanak 

 specimens. In the proximal part both cells and cell-islets occur more frequently (PI. 4, fig. 7). No 

 muscles are present in the mesoglcea except the sphincter and the mesogloeal muscles of the body-wall 

 which may break through the mesenteries; the structures (muscle-meshes) observed by Danielssen 

 are nothing but breaches in the mesoglcea. Lacunae are absent, except in the sexual region, where 

 some signs of these are seen. The entoderm is remarkably well-developed in comparison with the 

 other layers of the body. 



The sphincter (pi. 4 fig. 2) is very strong. Seen in transverse section the muscle-meshes in the 

 proximal part are separated by large portions of mesoglcea, in the distal part they are divided into 

 large meshes, extending in the direction from within outwards and almost filling the whole breadth of 

 the mesoglcea, or even more split up here, though smaller and lying nearer the ectoderm than the entoderm 



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