CLADOXEMxV RADL\TUM. 21 & 



little contractility (fig. 5). They serve the medusa as organs of attachment, the terminal 

 caijitulum having tlic power of closely adhering snckcr-likc to any surface to which it may be 

 apiilied, and the little medusa may be often seen attaching itself by means of these appendages to 

 the sides of the glass jar in which it is confined. 



The ocellns is very conspicuous. It is situated in tlic walls of the Ijulbous expansion, in 

 which the tentacle originates, and on tliat side of it which is turned away from the axis of the 

 medusa. It consists of an accunudation of pigment-granules, appearing of a deep crimson by 

 reflected light, and having a spherical refracting body imbedded in them (fig. 5). 



In a very early stage the marginal tentacles of the medusa are quite simple (fig. 1), I)ut when 

 it is about to free itself from the trophosome they present each a single appendage (fig. 9). Tliis 

 consists of one of the smooth capitate organs of adhesion, while that portion of the tentacle which 

 lies beyond it is covered with knot-like groups of thread-cells. As development proceeds the 

 organs of adhesion increase in numljer to three, the nodulated branches being at the same time 

 given off in succession, from tlie more distal portion of the tentacle, until they acquire the complete 

 number which characterises the adult medusa. During no period of the development of the 

 medusa could I detect the presence of an ectotheca. 



While the medusa is in the act of swimming the tentacles are contracted and curved 

 npwards round the margin of the umbrella. The cirri, or nodulated appendages of the tentacles, 

 are at the same time more strongly contracted, but the appendages destined for attachment always 

 remain extended (fig. 5). While floating passively in the water (fig. 3) the tentacles with their 

 appendages are extended to their entire length, and then hang down in a graceful tassel-like 

 cluster from the margin. 



The most remarkable attitude, however, is assumed when the medusa has fixed itself to the 

 side of the aquarimn (fig. 4). It then adheres to the glass by means of the sucker-like capitula, 

 which terminate the organs of attachment. On these appendages the medusa is elevated as on 

 SI) many feet, while all the rest of tentacle is extended to the ntmost, and thrown back over the 

 umbrella. The cirri are at the same time fully extended, and as they are now turned outwards, 

 float freely in the surrounding water, spreading themselves out with their thread-celUloaded 

 spherules, as if in search of prey. A more fascinating object it is scarcely possible to conceive of 

 than this wonderful little planoblast, whether moving in rapid darts through the water with alter- 

 nate systole and diastole of its crystal bell, or carried along passively by some gentle current with 

 its long pendulous tentacles drooping from the margin, or fixed by its suckers with these same 

 tentacles now tin-own around it in n whole grove of long flexile stems and undulating 

 branches. 



29 



