ACTINIJ5. 3 



. Genus Paractis. 



Paractidse with thin and smooth column wall ; tentacles of moderate length and 

 of uniform thickness throughout ; margin not lobed ; individual mesenteries of each 

 pair equally developed. 



Paractis polaris. 



One specimen labelled " Winter Quarters, 24. 8. 03," and taken in 25-30 fathoms 

 (PI. 1, Fig. 2). 



Height of column 2 • 3 cm. ; diameter of foot-disc 3 ■ 5 cm., diameter of oral disc 

 2"5 cm. Tentacles of uniform size, about 0'3 cm. long, in four cycles 

 12 + 12 + 24 + 48 = 96. The base is adhesive and thin, the insertions of the 

 mesenteries being visible through it. It is produced all round wider than the column, 

 which narrows considerably. The body- wall is firm, and near the parapet somewhat 

 thick, where it is slightly puckered by contraction. The mouth opening is visible in 

 the centre of the tentacles, crowded together by contraction. The oesophagus is 

 plicated and the two siphonoglyphs are well marked. 



The sphincter is fairly strong, mesogloeal, and produced to a fine termination. 

 A transverse section (PI. 1, Fig. 3) shows that it lies nearer to the endoderm, and is 

 reticulate in appearance, giving indistinct traces of layering. G-reater details of 

 structure are given in Fig. 4. 



The mesenteries are membranous, and the longitudinal muscles are somewhat 

 ditfuse, but well marked (PI. 1, Fig. 5). The mesogloeal layer is thin, except close to 

 the body-wall, where the parieto-basilar muscle arises, but the lamellse of the muscles 

 are conspicuous and branched. Two cycles of the mesenteries are complete, and these 

 are fertile, including the directives. The specimen is female, ova in various stages of 

 development being seen in sections. 



The radial muscles of the oral disc and the longitudinal muscles of the tentacles 

 are mesogloeal (PI. 1, Fig. 6). In regard to this character McMurrich (8, p. 161), 

 in his comments on the genus Paractis, states that of two forms of the ' Albatross,' 

 collections which, according to the generally accepted definition of the genus, must be 

 assigned to Paractis, one had these muscles ectodermal and the other mesogloeal, 

 and while raising the question as to whether this character is worthy of generic 

 distinction, he places both provisionally under Paractis. Of the ' Discovery ' specimens, 

 in both the one under consideration and the succeeding one the said muscles are 

 mesogloeal. 



Paractis pa paver. 



Actinia papaver Drayton in Dana, p. 143, PI. 4, Fig. 29, op. cit. 

 Paractis papaver Milne Edwardes, p. 249, torn. cit. 



A single specimen labelled " McMurdo Bay, Winter Quarters, 20 fathoms," only 



slightly contracted, with tentacles, oral disc and oesophageal opening plainly visible, 



the last-named being 1 • 5 cm. in diameter, 



