CAYO HUT I A AND THE REEF 63 



ably extended seaward to some extent by the 

 well-known process of reef expansion. No better 

 example could be presented than that before us to 

 demonstrate the constant warfare going on be- 

 tween the upbuilding coral polyps and the hosts 

 of destructive agents that tend to break down and 

 destroy the reef. The greater part of the solid 

 material on this particular patch is dead coral 

 undergoing gradual disintegration by myriad bor- 

 ing organisms and giving to the mass of rock an 

 indescribably rough and altogether fantastic ap- 

 pearance. Living coral polyps are constantly 

 finding lodgment upon dead blocks of more or 

 less altered coral rock and starting anew the up- 

 building process. As might be expected such new 

 growth is more apparent upon the outer or sea- 

 ward portion of the reef, where, in general, the coral 

 is more flourishing and appears to be growing with 

 considerable vigor. On the inner side of the reef 

 are many flattish blocks of complicated structure 

 which appear to be fragments of coral once rid- 

 dled and bored by worms and mollusks but now 

 with crevices and holes filled with sand and cal- 

 careous mud and the whole apparently recemented 

 together. In these blocks but little trace of the 



