434 STUDIES IN EVOLUTION 



The form of the buds is first that of a triangular pyramid 

 or prism, and is due to the mechanical conditions of growth. 

 During subsequent increase they touch and truncate each 

 other, changing from triangular to five- and six-sided prisms. 

 Complete symmetrical normal development produces a coral- 

 lum with equal hexagonal calices. The process of intermural 

 gemmation changes the sides of the parent cells to angles, 

 and the older corallites, originally in juxtaposition, become 

 separated from each other by new series of interstitial 

 calices. 



