HYDROMEDUSAE 297 



bulbs. Statocysts eight, adradial, with two or more statoHths. Colour: Stomach, gonads, 

 and basal bulbs pale yellow (in formalin). Size: 17 mm. in width and 11 mm. in height 

 (largest specimen). 



The first collection contains eight specimens, taken in Stanley Harbour on 10 Novem- 

 ber and 6 December 1898, which comprise a series extending from an intermediate to 

 the adult stage. In the second collection there are numerous specimens (about 120), 

 showing a complete series from a very early stage, o-8 mm. in diameter, to inter- 

 mediate stages, about 6 mm. wide ; they were taken in Stanley Harbour from 

 22 February to 27 March 1902. There are also some few specimens, 1-8 mm. wide, in 

 the third collection, taken on 19 January and 3 February 1910, probably also in Stanley 

 Harbour. 



The umbrella in the early stages is a little higher than wide, with thick walls; it 

 gradually becomes broader in proportion to its height as it grows. 



The stomach is decidedly quadrangular in shape, having also a quadrangular base, 

 without perradial lobes ; in the young stages it is somewhat longer than broad, but in 

 the intermediate and adult stages it is not quite as long as broad. The mouth, when 

 closed, has four conspicuous perradial lips ; in the early stages it has a plain margin, but 

 when the medusa is about 3 mm. wide a folding of the mouth rim begins to appear, and 

 in the intermediate and adult stages the margin is distinctly folded. The folds are 

 numerous and closer together near the apex of the lips. There are also four large 

 interradial folds which, when the mouth is closed, form small secondary lips placed at 

 right angles to the primary perradial lips. 



The gonads in the early stages are visible as minute dots in the middle of the radial 

 canals. As the medusa grows, they become elongated and at the same time are 

 gradually displaced towards the distal parts of the radial canals ; when the umbrella is 

 about 5 mm. wide the gonads are oval swellings on the fourth 1/5 or the fifth 1/6 of the 

 radial canals. In the intermediate stages, 6-10 mm. in width, the gonads form a thin 

 narrow ridge, broken into slight wave-like folds (Plate XVII, fig. 3). In the adult they 

 hang down from the radial canals, and the wave-like folds are more curved and con- 

 spicuous. They also occupy a great length of the radial canals, leaving only a very 

 small space vacant at each end of the canal. The gonads are parted in the median line 

 on the subumbrella side. 



The basal bulbs of the tentacles are large and globular or pear-shaped, with a heart- 

 shaped base, and evenly covered with nematocysts (Plate XIX, fig. 3). The tentacles, 

 when moderately extended, are somewhat longer than the diameter of the umbrella 

 and very thin; they are closely packed with transverse circular bands of nematocysts 

 (Plate XIX, fig. 4), except in their proximal part where the bands are more or less con- 

 fluent. The basal bulbs are hollow (Plate XIX, fig. 5) and in the proximal part of the 

 tentacle the endoderm cells are placed in several rows, but there is no central hollow 

 space, except very close to the basal bulb; in the greater part of the length of the 

 tentacle, from the point where the nematocyst bands are completely separated from 

 each other, the endoderm consists of one single row of cylindrical cells. 



