A< TI.M.K. 



Genus PAKACTIS. 



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

 of uniform thickness throughout : margin not lobed ; individual mesenteries of cadi 

 paii' cojiiallv developed. 



PAKACTIS I-OI.AKIS. 



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



(PI. 1. Fig. 2). 



Height of column 2'3 cru. ; diameter of foot-disc 35 cm., diameter of oral disc 

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

 12+12 + 24 + 48 = fM>. 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 bodv-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 bv contraction. The oesophagus is 

 plicated and the two siphonoglyphs are well marked. 



The sphincter is fairlv strong, tuesogloeal, and produced to a tine termination. 

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

 reticulate in appearance, giving indistinct traces of layering. (ireatcr details of 

 structure are given in Fig. 4. 



The mesenteries are membranous, and the longitudinal muscles are somewhat 

 diffuse, but well marked (PI. 1, Fig. 5). The meso<doe;d layer is thin, except close to 

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

 are conspicuous and branched. Two cvdcs 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 o|' the oral disc and the longitudinal muscle.- of the tentacles 

 are mesoglocal (PI. 1, Fig. 6). In regard to this character McMumch (8, p. 1<>1), 

 in his comments on the genus /'<i/'<n-f/x. states that of two forms of the 'Albatross.' 

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

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

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

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

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



rnesogloeal. 



PARACTIS I-.U-AVKK. 



Aftiniit t/ii/iarir Dniyum in ])aua, p. Ha, PI. 4, Fig. i".i. />. fit. 

 /'in-ai-tix /Hi/inrrf Milne Kilwank-s, p. :M'.i, Imn. tit. 



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

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

 the last-named being 1*5 cm. in diameter. 



