THE DISK. 291 



berant ; and there is a dark granular disk, which is 

 sometimes contracted considerably within the circum- 

 ference, and at others expanded so as to reach beyond 

 the webs which connect the bases of the tentacles. Fig. 

 2 shews a well expanded polype, as seen laterally: there 

 is a neck below the disk, and then a flask-shaped 

 body ; this latter fills the narrow limits of the cell, so 

 that the polype has no power of withdrawing itself ; 

 it can do no more when alarmed than draw the tips 

 of its tentacles together, and contract them into a 

 ball ; and this it does with that spasmodic grasping 

 clutching sort of action that I noticed in the young of 

 Laomedea geniculata. A beautifully distinct circu- 

 lation of granules in a fluid was seen pervading the 

 medulla of the sterd and branches to the cells. The 

 whole polypidom was much infested with fine radiating 

 fibres, doubtless parasitic ; and with some Vacjinicolce. 

 I counted seventeen tentacles in one, nineteen in 

 another. 



