150 



THE MECHANICAL FUNCTIONS. 



presenting the greatest similitude to flowers. The 

 Flustra (Fig. 63) is composed of minute and almost 

 microscopic cells, spread over a flat membranous 

 substance, resembling, in the flexibility of its tex- 

 ture and its mode of subdivision, the leaves of plants. 

 These cells are arranged in rows, with great regu- 

 larity, like those of a honey-comb, as is seen in the 

 magnified view of them. Fig. 64. 



In other tribes the base of support is internal, 

 constituting a kind of skeleton or axis; the poly- 

 pous mouths being spread at intervals over the sur- 

 face of the fleshy layer which covers this skeleton. 

 This is the case with the Gorgonia^ Antipathes, 

 and Coral, which exhibit still closer resemblances 

 to the branched forms of vegetable stems. The 

 flesh contains granules of calcareous matter, which, 

 in the dried specimens, adhere to the surface of the 

 stems. Fig. 6^ is a branch of the Corallium rnh- 

 rum, of which Fig. QQ is a magnified portion, show- 

 ing the appearance of the polypes in their expanded 



and contracted states. The way in which the po- 

 lypes are embedded in the flesh is seen in Fig. 67, 

 which represents a section of the GorgoniaBriareus. 

 In many cases the polypes are lodged in cup-like 

 depressions in the surface of the calcareous axis, 

 which affords them some degree of protection. In 



