WILLSIADiE. 



Genus I. Willsia, Forbes (1846), 



Char. Gen, Umbrella globose ; ovaries six, radiating around the base of the 

 short, campanulate, four-lipped stomach ; vessels six, twice dichotomously dividing 

 before they reach the marginal vessel ; a marginal tentacle opposite each branch : 

 ocelli conspicuous. 



Willsia siellata, Forbes. 

 (Plate I, Fig. 1.) 



I have constituted this genus for one of the most elegant of our naked-eyed Medusae, 

 strikingly distinct in its characters from all recorded forms, and quite new. I have dedicated 

 it to my friend Dr. Will, of Erlangen, whose work on the ' Medusae of the Adriatic,' already 

 often quoted, is one of the most valuable and original contributions to this department of 

 zoology ever printed. 



This beautiful little creature is, when full grown, about a quarter of an inch in diameter. 

 The umbrella is nearly globular, quite smooth, and colourless. The sub-umbrella is small in 

 comparison, and hemispheric, or slightly cylindrical in form. The margin bears twenty-four 

 extensile, pale yellowish tentacula, of a minutely granular tissue, and moniliform structure. 

 At the base of each is a bulb or ocellus, of a deep purple red and tawny yellow colour, the 

 darker hues being disposed in an arrangement partly crescentic, and partly eye-like. When 

 highly magnified, the coloured parts are seen to include a cavity containing a central body, 

 which, though not observed to vibrate, is probably the homologue of an otolitic mass. Some 

 specimens were observed which had only twenty tentacula. 



The central peduncle, or stomach, is campanulate, and opens widely by four scarcely 

 undulated lips.* Sometimes the orifice presents a six-lipped appearance, and it is very pro- 

 bable that it may contract itself indifi'erently into four or six divisions. Around the base of 

 the stomach, partly attached to its side, and partly to the sub-umbrella, are the six double 

 ovaries, or reproductive bodies, each of an oblong, somewhat spoke-like shape, and coloured 

 of a tawny yellow. The colour is due to two fulvous masses on each side the gastro-vascular 

 canal, one of which traverses the centre of each ovary. The fulvous masses are bordered by a 



* In the figure there is an appearance as if of a fifth lip, ^vhich is a mistake. 



