538 DR. F. w. JONES ON GROWTH-FORMS [June 18, 



definitely dead — veiy often for the reason that parasitic alga3 and 

 sponges attack the dead area. 



It is not till the colonial forms are reached that the powei- of 

 I'epair possessed by the corals is properly seen. In a colony 

 composed of myriads of individuals each actively living, each 

 capable of growth and repair, the very best conditions for repair 

 are at hand, and this is further aided in many cases by the 

 peculiar mode of growth of the colony. There are some inherent 

 characteristics of the lowly animals amongst which the corals 

 rank zoologically that are very wonderful, and that are opposed 

 both to the order of things that prevails in the higher classes, 

 and also to the popular conception of the life-history of the reef- 

 building corals. 



I think it is fair to say that the avei-age belief with I'egard 

 to the building of corals and coral-reefs is that the zooids live 

 and grow, flourish and die, and that their dead bodies form 

 mausoleums on which their progeny fovind their colony, and thus 

 build islands. Now, in contradiction to this, is the biological fact 

 that the actinozooid is a living thing that knows no time of 

 youthful vigour, no waxing to a period of adult life, no waning 

 to senility — it knows no age — it practically knows no natural 

 death. There is no building on the dead bodies of ancestors, no 

 perpetual dying and new birth ; and a colony of Madrepores will 

 contradict this popular fallacy at one glance, for, whatever the 

 age of the growth, the parent anthozooid flourishes till death or 

 accident overtakes the whole. It is a wonderful thing — and one 

 that is not, I think, generally considered — that the age of some of 

 these individuals in every colony must be excessive, even reckoned 

 as we reckon the age of higher animals. When we consider the 

 very slow rate of growth of some corals, and the great size of some 

 of the colonies to be seen every day on an atoll reef, and when we 

 I'ightly understand their mode of growth, and recognise that the 

 pioneer organism of the colony is still flourishing there, we cannot 

 help being struck by the excessive antiquity of that organism as a 

 living entity. Tha,t an apical zooid of a branching Madrepore 

 colony should be ten years old seems wonderful, but these indi- 

 viduals are mere juveniles when some of the component zooids of 

 massive growths are considered. 



Throughout the prolonged life of these lowly animals the process 

 of repair is a possibility, and a strange paradox is presented in 

 some forms, for the most aged member of the colony shows the 

 gi'eatest activity in all the processes of renewal and repair. 



The coral colony increases in size by the budding-oflf of new 

 zooids and the deposition of new calcium carbonate in their tissues, 

 and just as this is the ordinary mode of growth, so it is the 

 ordinary mode of repair. The type of repair naturally tends 

 to follow the type of growth of the injured colony ; and the 

 various genera, of corals might be taken in order and the details 

 of the repair of injury noted for each genus. But it is more likely 

 that some idea of the bionomics of the group will be gathered from 



