300 DISCOVERY REPORTS 



Specific characters. Adult: Umbrella watch-glass-shaped, twice to three times 

 broader than high. Stomach short, with four short perradial lobes. Mouth with four 

 large fimbriated lips. Gonads extending over the outer half of the radial canals and 

 reaching nearly down to the ring canal ; slightly folded. Tentacles sixty to eighty-five, 

 and a few young tentacular bulbs, the maximum number probably about lOO. Marginal 

 vesicles small, one between every two tentacles, with a single statolith. Colour: 

 Stomach, gonads, and basal bulbs of tentacles pale yellow (in formalin). Size: 

 Umbrella 22 mm. in width and 10 mm. in height (largest specimen). 



The first collection contains about sixty specimens, obtained from November 1898 

 to February 1899; in the second collection there are about 800, collected in Stanley 

 Harbour from 6 November 1901 to 27 March 1902, forming a good series from a very 

 early stage up to the adult. There is also one young one in the third collection, taken 

 on 28 October 1909 at Port Egremont. The smallest specimen in the first collection is 

 about 2 mm. in width and height, in the second collection there are several in still 

 younger stages, down to o-6 mm. in diameter. In these tiny medusae the apical canal, 

 which connected the medusa with the hydroid before liberation, is still visible, so that 

 they apparently represent an early stage of the free medusa, shortly after liberation. 



Development of the medusa. The umbrella in the youngest stages is about as high 

 as broad, or a little higher than broad, but as it increases in size it gradually becomes 

 broader, thinner, and flatter. The stomach in the early stages is quadrangular, but 

 becomes cross-shaped when empty and contracted. In the intermediate stages the 

 stomach shows the commencement of four short perradial lobes, which become larger 

 and more conspicuous in the adult. The mouth in the early stages has four little lips, 

 with a plain margin ; in the intermediate stages folds appear on the margin (Plate XVII, 

 fig. 5); in the adult the lips are large and have a well-marked fimbriated margin 

 (Plate XVII, fig. 8). 



The gonads are visible in the very earliest stages as minute globular swellings near the 

 top of the lower half of the radial canals ; they soon become oval and gradually increase 

 in length. The growth of the gonads is illustrated in a series of drawings (Plate XVII, 

 fig. 9) ; they are all drawn to the same scale and the measurements are taken from the 

 ring canal. The gonads grow outwards or downwards with the growth of the umbrella 

 and occupy the outer half of the radial canals. They also become folded; the folds first 

 appear in the intermediate stages. 



The tentacles have globular or pear-shaped basal bulbs (Plate XVII, fig. 7) and are 

 rather thin and short, spirally coiled when contracted. In some of the large adult 

 specimens there is a decided tendency towards twinning, either two tentacles on one 

 bulb, or two bulbs, with tentacles, joined together. 



The marginal vesicles, or statocysts, are small, closed vesicles, and contain a single 

 statolith (Plate XVII, fig. 7). The normal number is one between every two tentacles, 

 and by this the Falkland specimens are distinguished from most other species of 

 Phialidium. Occasionally two statocysts may be found between two tentacles, but only 

 in one or two places on the margin of one and the same specimen. 



