MRDUS^.. 23 



Ono of the intermediate staores has its moutli widely expanded, so that a good 

 vii'W is olitained of the interior of the stomach. Tiie papilhe are arranged in 

 l()ngitu<linal rows, which are interradial and adradial in position. The interradial 

 papilla? are a little longer than the adradial ones, and evidently were the first to 

 develop. In the adult the papilla? have the appearance of heing rather irregularly 

 scattered over the stomach, hut they are not present in the perra<lial portions. The 

 papillae extend only over the areas occupied by the gonads. As these papilla? are 

 simply outgrowths of tlie wall of the stomach, their function is prolmbly digestive. 

 After finding papilhu in this species I examined specimens of KnrUikerin {Rathken) 

 fascicularif! (Peron) and found the stomach well covered with them. 1 do not think 

 that papilhu have hitherto been recorded inside the stomach of any Ilydromedusse, 

 but on account of their minuteness they may easily have ]»ecn 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 

 l)ranching is .sometimes irregular, and a semi-contracted oral tentacle has a tree- 

 like appearan(;e. 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 wliich 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 umlncllar cavity. I have not seen these grooves with specialised 

 columnar cells in any other IMedusa, ])ut 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 growtli 

 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 prol)ably 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 iiitcrmiMliate stages 

 specimens occur with five tentacles (perradial groups) and three (interradial groups). 

 In each group of tentacles the central tentacle is always the laigest, and the central 

 perradial tentacle is larger than the c;entral interradial tentacle. Tlie ditterence in the 

 size of the tentacles is due to a difference in age. The central tentacle in each group 

 is the first to ajt])car, and as the central ])crradial tentacles are the largest, the .Medusa, 



