HYDR01DA. — MALE. < 



former species rather than to the latter. Campenhausen's figure 

 of the hydrothecae serves perfectly for 8. orthogoni urn, and 

 Allman's figure of the gouangium of his species seems to be only 

 an idealized representation of that of Busk's species, which 

 varies greatly in the degree of development of the transverse 

 ridges. 



A feature sometimes very noticeable in 8. mbvenfricosum 

 is the presence of a distinct lining or inner layer of the hydrotheca- 

 wall, which in many cases has so far become separated from the 

 outer perisarc as to constitute a distinct inner tube, running from 

 the base to the summit of the hydrotheca, and not fitting closely 

 to the outer wall throughout, but more or less detached from it at 

 intervals ; especially in such parts as the slight inflation 

 commonly found at the base, and the angle at the upper part of 

 the adcauline side. In the middle portion of the hydrotheca and 

 near the aperture it is usually so intimately united to the outer 

 wall as to be indistinguishable, but it may separate at any portion 

 and become conspicuous through its irregularly crumpled 

 condition. It is observable in many specimens from which all 

 trace of the hydranths and ccenosarc has disappeared, while in 

 other instances no trace of it can be distinguished. It may be 

 connected with the regeneration of the hydranths, though it is 

 often not to be detected in hydrothecae of which the border has 

 been reduplicated, while it is frequently very distinct in specimens 

 where regeneration does not appear to have taken place. 



In many of the hydrotheca? of 8. subventricoswm are found ova, 

 220-230 /x in length, 165-180 /x in width, perfectly elliptical, 

 yellow in colour, and situated exactly in the bend of the 

 hydrotheca?, to the diameter of which their own is nearly equal. 

 Some are quite fresh-looking, others empty and shrivelled. The 

 polypidoms in which these were found were quite empty other- 

 wise, all traces of the original soft parts having disappeared, both 

 from the trophosome and the gonangia. In a specimen of 

 8. patulum, probably from Port Phillip, I found what appeared 

 to be the remains of similar bodies. It would be a singular 

 instinct which should lead some animal to select especially the 

 empty polyparies of Synthecium wherein to deposit its eggs, but I 

 can suggest no other explanation, 



Loc, : — Great Australian Bight, on large Plumularians, 40 to 

 100 fathoms. 



Genus Diphasia, Agassiz. 



DlPHASIA SUBCARINATA (Bltsh). 



Sertularia sub-carinata, Busk, Voy, "Rattlesnake,' i., 1852, 

 p. 390. 



Diphasia mb-carinata, Bale, Cat. Austr. Hyd. Zooph., 1884, 



p. 102, pi. iv., fig. 1, pi, xix., fig. 18 ; Kirkpatrick, Sci. Proc. 



Hoy. Dublin Soc., vi. (n.s.), 1890, p. 604; Ritchie, Austr. 



Mus. Mem., iv., 1911, p. 850. 



