POLYPI. CORALLIFERI. 411 



minute Polypes, (Madrepora* Muricata, $c.,) often 

 known as the White Coral. Its form is branching, 

 and appears composed of numberless oblong cells, 

 overlapping each other, and set much like the blos- 

 soms of our common Heaths ; the mouth of each cell 

 displaying the star-like radiation of stony leaves, 

 above-mentioned. It is of these that Lamouroux 

 says, " Some by their union or aggregation, form 

 a long narrow ridge or reef which extends uninter- 

 ruptedly several degrees, opposing an immoveable 

 rampart to the great currents of the sea, which it 

 often traverses, the solidity and magnitude of which 

 increase daily. Sometimes this line of madreporic 

 rocks assumes a circular form ; the Polypes that 

 inhabit it gradually elevating their rocky dwelling 

 to the surface of the sea ; working then in a shel- 

 tered basin, they by little and little fill up its voids, 

 taking the precaution, however, to leave in the upper 

 part of this impenetrable wall, openings by which 

 the water can enter and retire, so as to renew itself, 

 and furnish them with a constant supply of their 

 aliment, and of the material with which they erect 

 their habitation."-]- It must, however, be admitted 

 that recent observations have made it necessary in 

 some degree to qualify these statements. It ap- 

 pears probable that the Polype only works in water 

 already comparatively shallow, and that where islands 

 are raised above water, or reefs are elevated to the 



* Mador, moisture, and porus, a pore, 

 t Expos. Method, des Poly piers. 



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