306 



THE OCEAN WORLD. 



of the coral, and the study of their anatomy confirms this conclusion. 

 In their case the digestive organs are no longer a simple sac with a 

 single orifice ; there is a mouth, a pharynx, a gullet, a gizzard, a mem- 

 branous stomach and intestines, with a special opening. We have 

 descriptions of some species in which the gizzard seems to be provided 

 with a certain number of interior teeth forming a wonderful pavement 

 a living mill for the purpose of grinding the food before it enters 

 into the second stomach. The organization of this small creature 

 reveals to our eyes a wonderful amount of combination of admirable 

 art immeasurably surpassing all that the most perfect human industry 

 and human genius can accomplish. 



After this general view of the organization of the group, we shall 

 proceed to introduce the reader to some of their more characteristic 

 species. 



Under the leaves of water-lilies (Nymphea), pond-weed (Potamo- 

 geton), or upon floating fragments of submerged wood, are generally to 

 be found certain Bryozoaires, animals described by Trembley under the 

 name of plumed polyps. These are Plumatellde (Fig. 121). These 



little diaphanous creatures 

 constitute colonies which 

 under the microscope re- 

 semble small branching 

 shrubs ; they consist of small 

 slender tubes grafted one to 

 the other, and having from 

 forty to sixty retractile 

 tentacula, which expand 

 like the petals of a flower ; 

 they are furnished with 

 vibratile cilia, the move- 

 ments of which serve the 

 purpose of leading food into 



Fig. 121. Plumatella crlstallina magnified (after Koesel). the mouth 



Another genus, which is found in ponds in France, and which is also 

 found in fresh water in Britain, is the Cristatella of Cuvier. " Perfect 

 specimens of C. muecdo occur from six lines to twenty-four in length by 

 two or three in breadth," says Sir J. Gr. Dalyel, " of a flattened figure, fine 

 translucent green colour, and fleshy consistence. Some of the shorter 



