1907.] AND SUPPOSED SPECIES IN CORALS. 549" 



the methods of i^egeiieration are more for the life saving of the 

 colony than of the individual. It is a rule with Nature that the 

 life of the individual is a thing of little moment : Nature has little 

 care for individuals, though she strives always to maintain the life 

 of the species. In a vast community of individuals, as is a coral 

 colony, each separate member is but a part of the whole body, and 

 the preservation of the colony is a thing of more imjjort than 

 the saving of a few individuals. A branching Madrejjore grows 

 naturally upwards into the danger zone, and the terminal branches 

 are inevitably destroyed, with the sacrifice of f\. myriad of zooids ; 

 but the result is a stimulus to lateral branching within the area 

 of safety, and the colony continues to flourish. 



In every massive growth starting to develop on all sides of a 

 nucleus, those zooids that are budded below can never hope to 

 live, and those on the upper surface will in all probability die. In 

 all the processes of repair that have been described, it is not the 

 individual that is mended, for an individual once badly danjaged 

 is not repaired ; but the loss is made good by the growth of new 

 zooids that take on the functions of those lost. Repair in colonial 

 forms does not save the individual from death, but it preserves 

 the life of the colony. Now loss by death in a colony is not 

 always repaired. 



We have seen that the flat tops of the massive growths of 

 Porites remain devoid of living zooids, and in several types of 

 growth, death of a portion of the colony is more or less usual ; 

 among the branching Porites it is normal to find the lower 

 portions of the growth dead, and no attempt made at their 

 repair. 



When it is said that the partial death of a colony is more or 

 less usual in some types of growth, it is not in any way meant 

 that the progress of coral formation is a bxiilding of the living 

 zooids upon the dead bodies of past generations, for the partial 

 death is due, as a rule, to very definite outside causes. 



In this atoll the greatest cause of coral death has been a. quite 

 nnusual one, but it has been a most instructive one, for it brings 

 out some very interesting facts in the life-history of corals. In 

 1876 all the living coral of the south-east portion of the lagoon 

 was entirely destroyed, by the pouring out of foul water from a 

 volcanic vent at the southern side of the atoll. The picture pre- 

 sented by these denuded areas was described by Dr. H. 0. Forbes 

 in 1879, and by Dr. Guppy in 1888; and in 1906 there is still the 

 same tract of dead coral on which the efibrts at re-colonisation 

 have been practically unavailing. 



This remarkable failure of the corals to repopulate a large 

 portion of the lagoon, is probably due to the fact that during 

 the period immediately following the disaster, various algse such 

 as agar-agar and several other species, being of a faster and moi-e 

 hardy growth, stepped in and took possession of the area before 

 the slow growing corals could obtain a proper footing. The 

 growth of algae is in itself hostile to the life of corals, and, 



