118 CORAL AND ATOLLS 



mould its growth in response to the demands of its environ- 

 ment, and in this repair process it possesses a further power, 

 for it can entirely alter the structure of an established colony. 



Numerous examples of this strange process may be seen. 

 A branching Montipora, growing in a gap in the island ring, is 

 found to have every colony dead or damaged in a greater or 

 less extent of its whole growth. The damage is probably due 

 to the fact that currents have altered the physical conditions 

 of the habitat since the founding of the colonies, and that a 

 greater rush of water has brought more sand and moving 

 particles in contact with them, for the apical branches of all 

 the colonies within a definite area will be found broken. The 

 repair of this damage invariably takes the form of an amor- 

 phous encrusting growth covering the debris of the dying 

 colony, the regenerated portion keeping pace with the destruc- 

 tion, and thus keeping the colony living — but living as an 

 entirely different type of its species. 



Madrejpora colonies show the same phenomena, and very 

 strange repair-forms of Pocillopora growing in rough water as 

 encrusting growths may be found. 



When, after repair, a Madrcpora colony assumes an en- 

 crusting form, as it frequently does, the inherent tendency of 

 its growth is still evident, for rising at intervals from its flat 

 surface are numerous dominant zooids, which, were the oppor- 

 tunity afforded them, would form upward -growing branches. 



It is by no means uncommon, in this process of repair, not 

 only for the vegetative growth of the colony to be altered, but 

 for the actual type of the corallum to be changed. When a 

 Montipora repairs its own ill-situated and dying colony by an 

 encrusting growth, the whole minute structure of the coral is 

 changed. Instead of the smooth surface over which the fairly 

 wide mouths of the corallites are dotted, is a coral with an 

 outward appearance notable chiefly for its extreme roughness, 

 due to the development of numerous papillse at the bases of 

 which open the minute corallites. The characters of the 

 original growth and of the repair growth are so entirely 

 different that they would certainly be regarded as two distinct 



