142 N. Annandale : The Fauna of Brackish Ponds. [VOL. I, 



this cannot be regarded as a constant character. Judging from 

 Hartlaub's figure {Zool. Jahrh., 1905, suppl. vi, p. 534), his South 

 American specimens represented a depauperated form. The Port 

 Canning colonies, however, are vigorous, the upright stems branch- 

 ing freely and attaining a height of about 15 mm. All the gono- 

 somes (in December) were female, each bearing a single egg, round 

 which the spadix, which was simple, had coiled itself. 



Irene ceylonensis, Browne. 



From one of the brackish ponds at Port Canning ; the medusa 

 originally described from off the coast of Ceylon. 



Trophosome — ■ 



Colony minute, barely visible to the naked eye, colourless; peri- 

 sarc extremely delicate. Hydrorhiza strongly adherent, branches 

 sparingly, does not anastomose, gives rise at intervals to single 

 upright polyps. Hydrotheca nearly cylindrical, with a short pedi- 

 cel, which is about one-seventh as long as the cup and bears more or 

 less distinct annulations ; an operculum present, consisting of a 

 number of triangular flaps which close together above the contracted 

 hydranth. Hydranths highly contractile, with about fourteen ten- 

 tacles , which are capable of great elongation ; the disk shallow ; the 

 hypostome inconspicuous. 



Gonosome — 



Gonosome borne on a long, more or less distinctly annulated 

 stalk, which as a rule carries a single medusa. Two or more younger 

 medusae are, however, occasionally produced at the base of and at 

 right angles to the first, the main axis of which is 

 that of the pedicel. Each medusa is contained 

 in a separate gonotheca, which is ovoid 

 variable in size, always larger than the hydro- 

 theca, and has a single aperture produced by the 

 rupture of the membrane above ; the gonophore 

 is a simple cylindrical body. Medusa at first 

 almost hydra-like in appearance, with the umbrella 

 feebly developed and with four stout, tapering 

 tentacles, by means of which progression is 

 effected. Adult medusa measuring 20 — 25 mm. 

 in diameter, the depth of the bell being less than 

 the breadth. No cirri ; tentacles about 100, some 

 of them often represented by small tubercles; 

 otoliths from one to four in each sense-organ, 

 a sense-organ occurring between each pair of 

 tentacles ; four radial canals ; manubrium stout, 

 conical, colourless ; stomach small ; mouth surrounded by four 

 fringed lobes ; gonads colourless, consisting of linear bands and 

 extending when mature from the base of the manubrium to the peri- 

 phery of the bell. 



Fig. 4. — Gonotheca 

 of /. ceylonensis, x 140. 



