GROWTH OF THE CORAL COLONY 87 



who have stated that the home of" election of the corals is the 

 surf-heaten edge of the barrier have made an error of ob- 

 servation and of fact. The comparatively lifeless zone of a 

 coral-reef is that part of the barrier Avhich is exposed to the 

 maximum force of the surf, with the rising and falling of the 

 tide. 



Such corals as do grow in the almost perpetual crash of 

 the surf are of a very easily recognised type ; and when con- 

 trasted with the forms of the same species that have lived in 

 calmer waters, they appear to have very few points in common. 

 The type of vegetative growth best suited to resist the force 

 of the waves is of course the rounded or flattened massive 

 boulder ; and the Pontes masses are the typo to which all such 

 growths tend to conform. 



This rounded form of growth is brought about in several 

 different ways : in Porites, and other corals, where the equal 

 reproductive value of all zooids tends to the production of a 

 sphere, it is of course the normal habit of growth ; and so such 

 corals have their natural home in the rouo-her water, and 

 undergo their atypical modifications when developed in other 

 sites. 



All branching forms, when ofrowinsf in rous'h water, are 

 subjected to a change of habit of vegetative growth ; and this 

 change is a very interesting one. It will be pointed out when 

 the process of repair is dealt with, that injury afl'ects various 

 forms of corals differently ; and all these rough-water forms 

 are in reality the result of perpetual injury. 



It would be an obvious disadvantage to a coral to adopt a 

 highly branching form when living on the surf- beaten portion 

 of the barrier ; for the colony would soon be wrecked and 

 broken up by the waves. There is no 3fonfipora in the atoll 

 that lives by election in rough water, but occasionally colonies 

 become exposed to strong currents ; and then the perpetual 

 injury to the upper portions causes the growing clusters to be 

 broken up and confused ; and the resulting growth is an 

 irregular mass of short, stunted branchlets. 



Montipora in rough water may also take on a creeping 



