How Animals Work. 



channel-way navigable by ships between the reef and 

 the mainland, the reef either encircling an island or 

 stretching as a natural barrier along the coast, like the 

 wonderful reef which fronts the north-east coast of 

 Australia with a length of nearly a thousand miles; 

 and (3) atolls, or lagoon islands, which are low reefs, 

 rising but a few feet above the highest tide level, and 

 enclosing a lagoon. 



An atoll presents a most remarkable appearance to 

 the voyager, as seen from the deck of the approach- 

 ing vessel. Rising out of the deep blue sea is seen 

 a low, more or less circular belt of land, dotted 

 with feathery-crowned cocoanut palms. A white line 

 of breakers fringes the shore, thundering upon it and 

 sending up great fountains of spray, while within the 

 encircling reef the waters of the lagoon shine with un- 

 ruffled surface like a burnished mirror. One would 

 imagine that the hardest rock must yield to the per- 

 petual onslaught of the mighty waves that day and 

 night break with cataract force against the reef, and 

 that in a few years all trace of land would disappear 

 beneath the surface of the sea. " Yet," as Dr. Hartwig 

 writes, " the insignificant coral islets stand and are 

 victorious ; for here another power, antagonistic to the 

 former, takes part in the contest. The organic forces 

 separate the atoms of carbonate of lime one by one 

 from the foaming breakers, and unite them in a sym- 

 metrical structure. Let the hurricane tear up its thou- 

 sand huge fragments ; yet what will this tell against the 

 " accumulated labours of myriads of architects at work 

 night and day, month after month ? Thus do we see 

 the soft and gelatinous body of a polyp, through the 



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