Chap. XX.] 



STRUCTURE OF MILLEPORA. 



457 



The Dactylozooids catch food for the colony, and deliver it to 

 the Gastrozooids, which alone are able to swallow and digest it. 

 All the polyps of the colony 

 are in communication at their 

 bases with the canal system 

 already described, and by means 

 of these canals the nutritive 



fluids derived by the gastro- ""i^fe -. ' " -° - '°'' ' I'^J-'i^ ^ 

 zooids from the food are dis- 

 tributed to the entire colony 

 and nourish it. There is thus 

 a very complete division of 

 labour in the colony. 



In all species of Millepora 

 the mouthless polyps are much portion of jhe uaku loral of 

 more numerous than the mouth- millepora nodosa. 



bearing ones. In some species ^^^'''''^ '^" "^*"'"*' "'"^-^ 



the gastropores and dactylopores are scattered irregularly over 

 the surface of the colonies. In the Tahitian species, however, 



E.NLARGEU VIEW OF PuKlIiiN iil HIE SUKFACE OF A LIVIXC, MILLEPORA 

 NODOSA, SHOWING THE EXPANDED ZOOIDS OF A SINGLE SYSTEM. 



In the centre is the short mouth beai ing Gastrozooid ; .around are the mouthless 

 D.ictylozooids. 



they are for the most part gathered into definite groups or 

 systems, each consisting of a centrally placed gastropore sur- 



