1907.1 AND SUPPOSED SPECIES IX CORALS. 543 



proxiinal portion of any zooid is a late change ; and therefore, if 

 the fracture takes place not verj^ far from the end of a branch, 

 the inherent vitality of the terminal zooid predominates, and it 

 starts the repair by continuing to grow out in the direction of 

 its original axis of growth, and by budding new zooids from 

 its sides. 



In a measured specimen that was fractured cleanly across one 

 of the main branches without other injury to the colony, the 

 apical zooid had, at the end of a hundred days, grown out 1 centi- 

 metre and had budded from its sides forty lateral daughter zooids; 

 and the general surface of the fractured end showed seventy 

 newly-formed coralla of old and new zooids. During the same 



Text-fig. 160. 



lype of repair of Madrepores when the "dominant apical zooid" is not 

 destroyed. Process at the end of 100 days. 



interval of time a branch of about the same diameter on the same 

 colony, that had received no injury, had advanced by 1-5 centimetres 

 and had added about a hundred and twenty new lateral zooids ; 

 so that,_ judged as growth in these corals must be judged, the rate 

 of repair is a rapid one. In this case the dominant zooid is apical, 

 a,nd its superior vitality enables it to regenerate and to continue 

 the growth along the lines of original branching; but if the 

 vitality of the " apical directive zooid " is definitely destroyed, a 

 very different state of affairs is brought about. 



2. If the "apical directive zooid " is destroyed, and especially if 

 the damage is extensive and affects a large area of a branch, the 

 predominant functions of the apical zooid are taken over by the 



Proc. Zool. SOC.--1907, ISTo. XXXYII. 37 



