MEDUSA. 55 
the gonads develop the band becomes sinuously folded and broadens. In the young 
adult the band is about 4 mm. in width and somewhat semicircular in shape. 
There is no sub-genital cavity as in Awrelia aurita. The gonads protrude from the 
stomach and hang down from the sub-umbrella like the gonads of a Chrysaora. 
In the meta-ephyra stage the genital sacs have the appearance of simple sac-like 
enlargements, with very thin walls ; on the wall of the stomach inside are situated two 
rows of gastric filaments and the embryonic genital band. By the time the gonads 
have reached maturity the genital sacs have become lobated (Plate VL, fig. 5). 
Internally the proximal end of the sac is covered with numerous gastric filaments, and 
its distal end or bottom holds the gonads, which are now arranged in more complicated 
and somewhat irregular folds. 
The tentacles are very much laterally compressed, especially in the basal portion, 
but the distal portion is more round and tapers off to a slender point. Along the 
whole length of the tentacle, on the inner side, runs a band or ridge, which is closely 
studded with clusters of nematocysts. The outer side of the tentacle is smooth and 
free from clusters of nematocysts (Plate VI, fig. 6). The tentacles are hollow 
throughout their whole length, a flat tube-like cavity running close to the inner edge. 
They are apparently in a semi-contracted condition, and the tube-like cavity is 
contracted into a series of transverse folds, which, when viewed from the outer edge 
of the tentacle, have the appearance of a series of rings. The folding or wrinkling 
is present in all fully-grown tentacles, and is sufficiently conspicuous to be noticed 
by the naked eye. 
In the adult there are normally sixteen sense organs, alternating with sixteen 
tentacles. The rhopalium, or tentaculocyst, is not well protected in this Medusa— 
neither by lying back in a groove nor by a covering formed by the marginal lobes. 
It is situated on the wall of the niche formed by the marginal lobes, and points 
upwards towards the aboral side of the umbrella. The rhopaliar canal, which leads 
from the circular canal to the sense organ, is broad and flat in the adult. Over the 
rhopaliar canal and on the surface of the umbrella is situated a small patch of darkly 
coloured cells, in the midst of which there is generally a slight depression forming 
the dorsal sensory pit. The pit has the appearance of being in a rather rudimentary 
condition and is occasionally absent. 
Although the marginal lobes are more or less torn, there are no indications of 
any further increase in number, beyond the original thirty-two of the ephyra stage, 
by subsequent division. The ex-umbrellar side of the lobes is covered with numerous 
warts containing nematocysts. The lobes show a slight variation in shape, and fill 
up the space between the sense organs and the tentacles. As these are not always at 
equal distances apart, some of the lobes are broader than others. 
Vanhoffen’s description of the adult is based upon a large fragment of the 
marginal part of the umbrella, and Maas had only one quadrant of an umbrella to work 
upon. Vanhéffen describes and clearly figures tentacular lobes on the margin of the 
