THE TUBIPORA. 



113 



provided for the movements of the 

 little polyp. As the membrane is 

 placed all round the base of the 

 animal, its contraction brings the 

 polyp towards the opening of the 

 cell, while it is retracted by the 

 contrary action. The minute glo- 

 bules, which appear like strings 

 of beads, are the germs of a future 

 race. How often, in our study of 

 the natural world, may we be re- 

 minded of the poet's words : 



POLYP OF A 

 TUBIPORA. 



" In human works, though labour'd on with pain, 

 A thousand movements scarce one purpose gain ; 

 In God's, one single can its end produce, 

 Yet serves to second too some other use." 



And thus it is not enough that the membrane of 

 this minute polyp should enable it to rise or to descend 

 by a beautifully simple mechanism ; for it extends 

 to where the earthy matter bounds the residence of 

 the animal. Indeed, the calcareous tube, which 

 is its dwelling, is produced by a gradual petri- 

 faction of the membrane itself as it rises ; for when 

 it attains a certain elevation, its funnel-shaped edge 

 expands horizontally, and, doubling itself, forms, by 

 depositing calcareous particles in its substance, a 

 stage composed of two plates soldered together ! 

 As, too, all the polyps act simultaneously in the same 

 manner, and upon the same plane, the stages are pro- 

 duced which bind the bundles together ; for the. 



