GROWTH OF THE CORAL COLONY 83 



the " dominant zooid " is marked off from its 

 distinctive anatomical feature, for it is sym- 

 metrical. Of tlie many thousands of daughter 

 zooid s budded off" from the " dominant zooid," 

 all are not alike; the great bulk are asym- 

 metrical, and are but little raised from the 

 general surface of the coral, but here and 

 there a prominent and symmetrical zooid is 

 given off. Like the " dominant zooid," these 

 lateral zooids possess the power of perpetual 

 growth, and they are the agents in forming the 

 lateral branches. Under certain conditions 

 only very few of these prominent lateral zooids 

 are produced, and then the resulting vegetative 

 growth consists of long straight stems with 

 but few side-branches. 



The typical form of vegetative growth of 

 the Madrcpora is therefore a branching system, 

 but many variants of this form are developed 

 normally and abnormally. Pseudo plate-like 

 growths are common, and they are formed by 

 the anastomosis of numerous branches in one 

 plane. Again, the importance of the " domi- 

 nant apical zooid " is variable, and some types 

 branch more after the type fashion of 

 the Monti-pora, for a whole apical series 

 of zooids may be symmetrical. 



fellows by a 

 Fig. 21. 



Having now reviewed, in some 

 measure, the various methods of the 

 formation of the vegetative growth of 

 colonies, it is necessary to see how far 

 these forms of growth are to be reckoned 

 as specific qualities. Here a great diffi- 

 culty arises, for an enormous amount 

 of time and careful experiment must 

 be devoted to the proving or disproving 



Vegei'aiive Eepro- 

 DUCTiON IN Corals. 



Diagrammatic section to 

 illustrate the mode of 

 growth of Madrepora : 

 the " dominant apical 

 zooid " is the oldest 

 member. 



of each individual 



