GONIONEMUS VERTENS. 



129 



disk touches the top of the water, the Medusa inverts itself, and sinks, 

 with its tentacles fully expanded, until it reaches the bottom, or an- 

 other piece of sea-weed, where it attaches itself, and after remaining 

 suspended a little while, repeats the same operation ; when attached, 

 it requires strength enough to break the tentacles to make them loose 



Fig. 197. 



Fig. 198. 



their hold. I have never found single individuals, but have always 

 seen them in large numbers swimming among the sea-weed in the 

 manner described. The form of the spherosome is that of an oblate 

 spheroid, cut in two by a plane passing through the north and south 

 poles, the plane of intersection containing the circular tube ; there are 

 sixty-four tentacles, fifteen between each chymiferous tube, placed so 

 closely together that they seem all to unite at the 

 base. The tentacles, when contracted, resemble a 

 scythe fastened by a band to the circular tube 

 (Fig. 199) ; the pigmen1>cells are numerous, and 

 give the circular tube the appearance of having 

 a large row of violet knobs, to which the tentacles 

 are attached. There is one part of the tentacle, 

 near the tip, which seems to be more thickly cov- 

 ered by lasso-cells, and by which the Jelly-fishes 

 attach themselves ; when the tentacles are fully 

 expanded, they always make an angle at that point, as if they had 

 been broken, and the parts joined together again. (Fig. 197.) The 



Fig. 197. Gonionemus vertens, as it appears when attached by its tentacles. 

 Fig. 198. Gonionemus vertens, in motion ; natural size. 

 NO. II. 17 



