TAHITI. 



527 



it. There is thus a very complete division of labour in the 

 colony. 



In all species of Millepora the 

 mouth-bearing polyps are much 

 more numerous than the mouth- 

 less ones. In some species the 

 gastropores and dactylopores are 

 scattered irregularly over the sur- 

 face of the colonies. In the Tahi- 

 tian species, however, they are 

 for the most part gathered into 

 definite groups or systems, each 

 consisting of a centrally placed 

 gastropore surrounded by a ring 



of five, six, or seven dactylopores, as shown in the accompanying 

 figure, where the circular groups of minute pores are seen 

 scattered over the coral surface. 



The second figure shows, much enlarged, a single system 

 of polyps belonging to one of these pore systems, as it appears 



PORTION OF THE HARD CORAL OF MILLE- 

 PORA NODOSA. 



(Twice the natural size.) 



ENLARGED VIEW OF PORTION OF THE SURFACE OF A LIVING MILLEPORA NODOSA, SHOWING THE 



EXPANDED ZOOIDS OF A SINGLE STSTEM. 



In the centre is the short mouth hearing Gastrozooirl, around are the mouthless Dactylozooid>. 



