ZOANTHARIA 47 



which in the full-grown specimens especially are very elongated in shape, lie very far from each other. 

 They are narrowest at the base but expand somewhat towards the distal part. The capitular furrows 

 are very indistinct. The upper margin of the polyps is somewhat rounded. The polyps as well as 

 the ccenenchyme are richly though not very conspicuously incrusted. 



The oesophagus is short, the siphonoglyphe distinct. Hyposulcus? 



Anatomical description. The ectoderm of the body-wall is high and reaches almost the 

 same size as the mesogloea. Except in the capitular region it contains fairly many nematocysts with 

 greatly twisted thread, length 2934^, breadth 10 12 p. Particles of detritus are found in and on 

 the ectoderm. The mesogloea is moderately developed , and very much incrusted with foraminifera 

 (dissolved in the section on PI. 7, fig. 2), sand and sponge-needles, the latter heaped up especially in 

 the capitular region. Scattered granular cells of moderate size, sometimes also larger, occur fairly 

 commonly here (PI. 7, fig. 2). The entoderm is considerably thinner than the ectoderm. 



The sphincter is long and strong, of the same appearance as in other Isozoanthus-species. 



Regarding the tentacles I am unable to give any other information than that their ectoderm 

 as usual contains numerous spirocysts. 



In the oesophagus the ectoderm is high, the mesogloea thin, whereas in the siphonoglyphe the 

 conditions are reversed. 



In the single specimen sectioned, the number of mesenteries, as far as I was able to see on 

 the somewhat torn sections, was 34, 10 macro and 8 micro on the one side and 9 macro and 7 micro 

 on the other. The micro-mesenteries are moderately developed. The longitudinal musculature is but 

 moderately developed, forms few or no folds at all, the parieto-basilar muscles weak. So far as I was 

 able to see on the not well-fixed material the longitudinal and parieto-basilar muscles extended only 

 a moderate distance on the body-wall. 



The filaments have the usual structure. The glandular tract region contains large nematocysts 

 with coiled thread (length 26 ^4 ft, breadth 10 12 ft), but they only occur sparsely as is also the case 

 with some smaller, similar capsules (length 14 p, breadth 5 ft) and some thick-walled capsules broader 

 at the one end (length 22 ft). Inside the filaments in the entoderm of the mesenteries we also find 

 many nematocysts (length 1417^, breadth 10 lift) and numerous elongated, generally curved nema- 

 tocysts (length 2226^, breadth 5/4 These capsules probably do not belong to the animal, but are 

 foreign nematocysts taken up by the ectoderm (2 specimens examined). 



The animals were not sexually ripe. 



Remarks. The above-mentioned species is undoubtedly closely related to Isozoanthus dubius 

 from St. 45, but differs from the latter mainly in the larger nematocysts, and the stronger sphincter. 

 Later examination of a larger material may possibly show that they can be thrown together to form 

 one species, but till then I think it best to separate them. 



Isozoanthus dubius n. sp. 



PI. 2, fig. 19. PI. 7, fig. 3. 



Occurrence: 6i32'N., 943'W. 643 Dan. fms. Bott. temp. 4-17. Ingolf Exp. St 45 i colony. 

 Dimensions: Length of the largest polyp 0-8 cm., greatest breadth 0-30111. 



