484 ACTINIA OR SEA-ANEMONE. 



other, so as to form a considerable number of chambers arranged 

 round the central digestive sac. There is not any regular com- 

 munication between the chambers and the stomach ; although it 

 would seem that an opening must be occasionally formed, as 

 young Polypes are often sent forth by the mouth ( 1 131). The 

 partitions all have openings, however, by which the chambers 

 communicate with each other ; and there is also a free entrance 

 from them into the tubes of the hollow tentacula, which are 

 formed of a membrane like the envelope of the body, and are 

 provided with an orifice at their extremity, which the animal 

 has the power of closing. 



1126. The muscular structure of the substance of the Acti- 

 nice is very distinct in the larger species, and confers upon the 

 animal considerable power of prehension. Dr. Grant mentions 

 that he has caused the common Actinia crassicornis to lift a 

 basin of sea-water, weighing more than six pounds, by making 

 it swallow the perforated shell of a Purpura, through the aper- 

 ture of which a cord had been passed. By this cord the basin 

 was lifted, without the Actinia quitting its hold either of the 

 shell in its contracted stomach, or of the basin to which its foot 

 was attached. It is not surprising, therefore, that these Polypes 

 should be able to master not only shell-fish and other animals 

 that have little means of active resistance, but even crabs, prawns, 

 and other Crustacea of considerable size. These indeed seem to 

 constitute its ordinary food. The luckless individual which 

 walks over one of these stomachs, gaping for its prey, is imme- 

 diately secured by its tentacula, and in spite of its struggles is 

 drawn into the mouth, which seems capable of distention to an 

 almost unlimited degree. Sometimes the tail of a shrimp, or 

 some other hard projecting appendage, will occasion a little 

 trouble, and may be seen in active movement outside the mouth, 

 when the mass of the body has been swallowed ; but this is soon 

 restrained by the tentacula, which entwine themselves round it, 

 and gradually convey it into the stomach. These tentacula 

 possess a remarkably tenacious power, which is attributed to the 

 presence of a multitude of organs known as thread-cells or Jili- 

 ferous capsules imbedded in their substance. 



