MEDUSA. 23 
One of the intermediate stages has its mouth widely expanded, so that a good 
view is obtained of the interior of the stomach. The papille are arranged in 
longitudinal rows, which are interradial and adradial in position. The interradial 
papille are a little longer than the adradial ones, and evidently were the first to 
develop. In the adult the papille have the appearance of being rather irregularly 
scattered over the stomach, but they are not present in the perradial portions. The 
papille extend only over the areas occupied by the gonads. As these papillae are 
simply outgrowths of the wall of the stomach, their function is probably digestive. 
After finding papille in this species [ examined specimens of Koellikeria (Rathkea) 
fascicularis (Péron) and found the stomach well covered with them. I do not think 
that papille have hitherto been recorded inside the stomach of any Hydromeduse, 
but on account of their minuteness they may easily have been overlooked. 
The oral tentacles in the youngest stage of the series are three to four times 
dichotomously branched, and the number of branches increases with age. The 
adult has its oral tentacles at least seven times dichotomously branched. The 
branching is sometimes irregular, and a semi-contracted oral tentacle has a tree- 
like appearance. The distal branches all terminate with a small cap containing 
nematocysts. 
The radial canals are broad and are adjacent to the ectodermal lining of the 
sub-umbrella. The ectoderm cells opposite the radial canals are quite different in 
shape and appearance from the flat epithelial cells which form the sub-umbrellar 
lining. They are distinctly columnar (fig. 4) and project out so as to give a jagged 
outline, and are, moreover, within a well-marked groove, which runs along the whole 
length of the umbrellar cavity. I have not seen these grooves with specialised 
columnar cells in any other Medusa, but owing to their minuteness they are not easily 
detected, except in transverse sections. There are also indications of columnar cells 
forming a narrow interradial line, about three cells wide, but here the groove is absent. 
The gonads practically cover in an even layer (fig. 5) the whole outer wall of the 
stomach, but they are divided into four separate masses by very narrow perradial 
bands of ectoderm which are completely free from genital cells. 
The number of tentacles in each of the eight groups depends upon the growth 
and age of the individual. The youngest specimens of the series have three tentacles 
in each group, and the large adults have seven (fig. 3), which is probably the 
- maximum. The number of tentacles in the perradial and interradial groups are 
frequently the same, but not always. One large adult has seven tentacles in the 
perradial groups and five in the interradial (fig. 2). Among the intermediate stages 
specimens occur with five tentacles (perradial groups) and three (interradial groups). 
In each group of tentacles the central tentacle is always the largest, and the central 
perradial tentacle is larger than the central interradial tentacle. The difference in the 
size of the tentacles is due to a difference in age. ‘The central tentacle in each group 
is the first to appear, and as the central perradial tentacles are the largest, the Medusa, 
