26i EAMBLES OF A NATURALIST. 



regularity one invariable and determinate direction, 

 during the whole life of the animal. It is not the 

 same with the lower animals. Here, as we have seen 

 in the instance of the Hydra, the circulation is often 

 confounded with the other functions of nutrition. 

 Between these two extremes, however, there must 

 necessarily be many intermediate connecting links. 



Even the class of Polypes presents some instances 

 of progressive development. Let us open one of 

 those animals which, connected by hundreds upon 

 a sort of common stem, of which they represent the 

 flowers, produce the substance known as coral. In 

 these animals the mouth terminates in a sort of 

 pouch or bag, suspended in the cavity of the body, 

 and constituting an actual stomach, into which 

 the food penetrates. After the latter has been 

 sufficiently digested, the animal rejects by its mouth 

 the coarser residue, and opening an orifice which 

 is situated at the other extremity of the bag, it 

 only suffers the portions of food adapted for its 

 maintenance to penetrate into the interior. From 

 this special cavity within each animal are given 

 off canals, which, being prolonged into the common 

 part or the ])olypary, communicate freely with similar 

 canals coming from all the other polypes — an ar- 

 rangement by which the entire colony profits from 

 the nourishment taken separately by each indivi- 

 dual. 



Something similar to this exists in the case of some 

 of the Medusiie, while in others the functional labour 

 begins to be more definitely characterised. These 

 animals, as we have already said, resemble an in- 



