ANEMONES AND CORALS 55 



tects at work night and day, month after month ? Thus do we see 

 the soft and gelatinous body of a polyp, through the agency of 

 vital laws, conquering the great mechanical power of the waves of 

 an ocean, which neither the art of man nor the inanimate works 

 of Nature could successfully resist." 



Fascinating as the subject is, it would be quite impossible in 

 the space at my command to enter into a full discussion of the 

 formation of these Coral reefs and islands. Therefore I must refer 

 my readers to the pages of Charles Darwin's deeply interesting 

 and clearly written " Coral Reefs," which is still considered by 

 palaeontologists and geologists as the most authoritative state- 

 ment on the subject. 



Darwin's assumption as to the substratum of these islands being 

 composed of the calcareous remains of invertebrate marine animals, 

 and his theory of gradual land subsidence as the primary cause 

 of Coral-reef formation, have been fully confirmed by the recent 

 experimental borings carried to a depth of 1,114 ^ ee ^ on the island 

 of Funafuti. That his theory of gradual subsidence may not be 

 applicable in a few cases is quite possible ; other natural causes, 

 such as the abundant deposition of the remains of calcareous . 

 organisms, may have been under favourable conditions sufficient 

 to raise the summits of submerged mountains to a level where the 

 reef-forming Corals can commence to flourish. But these isolated 

 cases all require far more careful and systematic investigation 

 than they have yet received, and though under certain favour- 

 able conditions atolls and reefs may thus be formed without the 

 subsidence of land, their presence in no way upsets Darwin's 

 theory as applied to the innumerable examples of the various reef 

 formations which stud the Indian, Atlantic, and Pacific Oceans. 



The numerous members of the Alcyonaria are characterised by 

 having eight tentacles, or the tentacles in multiples of four not 

 simple like those of the Zoantharia, but each consisting of a main 

 stem with two rows of lateral branchlets. These pinnate x ten- 

 tacles form a single row, or circle ; are enlarged at their base, and 

 each communicates with one of the eight mesenteric spaces. To 

 this order belong the so-called Blue Coral (Heliopora ccerulea), the 

 Sea-pens (Pennatulida), the Sea -fans, Red Coral, and Organ- 

 pipe Coral. 



Pinnate branched. 



