350 NATURAL HISTORt". 



cula and thrust down into the capacious stomach. So 

 voracious are these animals that they will attempt to 

 swallow articles which their stomachs can not possibly 

 accommodate. In this case the animal will perhaps hold 

 the mass partly in and partly out of the stomach firmly 

 with its tentacles, pushing it farther in as fast as the low- 

 er part of the mass is digested. 



609. In 599 I spoke of the arrangements of the ten- 

 tacles of different animals. The structure of the tenta- 

 cles of the Actiniae is very peculiar. Their power of 

 holding on is owing to a multitude of cells, in which 

 there are coiled up in a spiral form fine wire-like fila- 

 ments. These can be shot forth from their cells to a con- 

 siderable length, and this being done with a multitude 

 of them enables the animal to hold on fast to its prey. 



610. Some of the Polypes of this order have a skele- 

 ton. It is formed inside of the animal at its lower part, 

 and it is fastened to the spot where the Polype lives. 

 We may consider it as a foundation frame-work for its 

 body. Resting on this, it puts forth its arms continually 

 to take its food. 



611. But this skeleton differs from the skeletons of all 

 other animals in one respect. Other animals retain their 

 skeletons all their lifetime ; but the Polype does not. It 

 is constantly making new skeleton. It is a singular proc- 

 ess, and I will describe it to you with its results. Th 

 very lowest part of the Polype is continually dying, and 

 with it the skeleton which it covers. But as this dies 

 the animal keeps its full size, for the body is continually 

 supplied with new living substance on the borders of the 

 dying portion. It grows just as fast as it dies. It there- 

 fore is all the time moving upward, making new skele- 

 ton, and leaving the old below. The result, you plainly 

 see, would be a column of dead skeleton with the Polype 

 at the top of it. In this column, after a while, the living 

 part is but small in comparison with the dead part below. 



612. This result you see represented in Fig. 272, one 



