POLYPES. 



73 



structures of the Coral-worms very far excel the mightiest 

 edifices of m8.ii. What was the impious project of Babel, 

 what are the Pyramids of Egypt, compared with the coral 

 reef of Australia — a barrier which extends almost without 

 an interruption for a thousand miles ! 



The notion that the coral-rock was commenced in the 

 fathomless depths of the ocean, and gradually reared to 

 the surface, has been exploded by the discovery of Darwin, 

 that the Coral-polypes cannot exist at a greater depth 

 than some twenty or thirty fathoms. Our limited space 

 will not permit us to do more than allude to his beautiful 

 and ingenious theory, by which all the phenomena of coral 

 formations are explained. It seems certain that every 

 such structure must have been commenced on the inor- 

 ganic rock : and the slow subsidence of these in many 

 instances has produced the various forms of atolls, or ring- 

 islets enclosing lagoons, of barriers, and of fringing reefs. 



Most intelligent persons are acquainted with the more 

 common forms of Madrepores or Corals. Whether exist- 

 ing in massive, ramified, or laminated structures, they com- 

 monly consist of a light porous stone, studded with shallow 

 pits, in which are seen thin perpendicular plates radiating 

 towards a centre. Sometimes instead of pits and a radiat- 

 ing arrangement, the plates are set in rows in an involved 

 and sinuated pattern. Xow, during life, from amidst 

 these plates rises up a gelatinous tissue bearing a mouth 

 with protrusile lips, and an array of sensitive tentacles, 

 all of which on alarm are contracted so as to disappear 

 completely in the stony recesses, leaving nothing apparent 

 but the white and apparently naked plates. Really, how- 

 ever, they are not naked, but are still invested with a 



