LIFE-PROCESSES OF CORAL COLONY 111 



way a tunnel may actually bridge a space from one plate to 

 another, and its mouth be carried out clear of the general 

 surface of the coral ; for where the tunnel goes the surface- 

 layer of coral ever keeps pace. 



(B) The question of the processes of repair becomes 

 further complicated in those corals, such as the Madreporce, 

 in which all the members of the colony are not of equal im- 

 portance. A¥e have seen, in considering the mode of growth 

 of such corals, that the very first individual in a colony may 

 continue to flourish and lead the growth of the entire com- 

 munity as long as that community lasts. The original zooid 

 which, as an embryo, settled on the basis that formed the site 

 of growth may be the " directive " zooid of the entire colony, 

 and the apical zooid may represent the oldest living animal 

 matter in the community. But besides the " dominant apical 

 zooid," others arise at intervals, by budding from the sides, 

 which are possessed of more inherent vitality than their fellows, 

 and from their first birth they tend to grow out as new direc- 

 tive zooids and lead to lateral branch formation — and besides 

 these more virile lateral zooids are the hosts of individuals 

 which in the normal condition of the growth reach no greater 

 dignity than a uniform projection of their corallites. 



Now when injury or destruction affects a portion of the 

 colony, it reacts on individuals whose functionating values in 

 the economy of the colony are not equal, and so we should 

 expect that the result of injury or destruction would vary 

 according to the different parts of the colony on which the 

 maximum of damage falls. And this is the case. The actual 

 results of repair of various injuries inflicted in experiment, or 

 by Nature, show more clearly the relative values and functional 

 activities of different portions of such a colony than will any 

 amount of theorising or speculation. 



1. If the injury be so inflicted that the branch of a 

 Madrepora colony is broken transversely, and the injury is 

 limited to a mere fracture of the cross-section, then the repair 

 takes place by the activity of the " dominant apical zooid." 



