14 



TABULATE CORALS. 



b), and are destitute of any mouth. The " dactylozooids " per- 

 form the functions of prehension for the colony, and supply 

 food to the " gastrozooids," by which the work of digestion 



Fig. 2. — Enlarged view of a portion of the surface of a living colony of Millepora nodosa, 

 showing the expanded zooids of a single system, a, Central "gastrozooid ;" b. One of 

 the mouthless "dactylozooids." (After Moseley.) 



and assimilation is carried on. The nutritive fluid thus elabor- 

 ated is distributed over the entire colony by means of branched 

 coenosarcal canals, which communicate with the body-cavities 

 of the zooids, and ramify in every direction through the spongy 

 ccenenchyma. 



Of the genera associated by Edwards and Haime with 

 Millepora, Heliopora and its Palaeozoic and Secondary allies 

 are now known to be referable to the Alcyonaria; Fishdipora, 

 M'Coy, belongs undoubtedly to the family of the Montictdipor- 

 idce ; and the Tertiary Axopora, with its fasciculate columella, 

 is of uncertain affinities. Millepora itself is only known as a 

 Tertiary fossil, and as living ; but the Cretaceous genus Poro- 

 sphcera, Steinm., appears to be closely related to Millepora, 

 and therefore also to belong to the Hydrocorallincs. 



II. PociLLOPORiD.^. — The corallum (fig. 3) of Pocillopora, 

 the type of this group, is dendroid or foliaceous, composed of 

 numerous tubular corallites, which are surrounded by an imper- 



