CALCAREOUS SKELETON OF THE ANTHOZOA. 525 



To sum lip the characters of Heliopora : 



1. The corallum is composed, like that of Madreporaria, 

 of vertical or nearly vertical trabeculse; but instead of 

 the trabeculae being in apposition by their lateral surfaces, 

 as in Madreporaria, they are separated by ccenenchymal 

 tubes. Each trabecula gives out arms at angles of 120°, 

 and the arms unite suturally with similar arms from adjacent 

 trabeculse. 



3. Each trabecula consists of crystalline fibres diverging 

 outwards and upwards from a centre of calcification situated in 

 the centre of the trabecula. 



3. In transverse section the emergent crystalline fibres give 

 rise to the appearance of strise concentric with the centres of 

 calcification. Such striae are most conspicuous in the secondary 

 deposits in the interiors of the calyces. 



4. The separate crystals or bundles of crystalline fibres are 

 not formed within cells, but are formed by crystallisation in con- 

 nection with an organic basis produced by the disintegration of 

 calicoblast cells. 



5. Special structures, here called '' desniocytes,'^ are formed 

 amongst the calicoblasts. They take their origin from certain 

 cells in the calicoblast layer, and become secondarily attached 

 to the mesogloea by processes. Their function is to bind the 

 soft tissues to the corallum. 



Madreporaria. 



As regards the shape and position of the calicoblasts and of 

 the desmocytes there is no great amount of variety among the 

 Madreporaria, though it will appear that my observations con- 

 firm previous statements by Fowler and myself as to the 

 presence of unusually elongated calicoblasts in Muss a and 

 Lophohelia. I have examined a considerable number of 

 species, including Caryophyllia Smithii, Mussa distans, 

 Lophohelia prolifera, Euphyllia (sp. incert.), Porites 

 bulbosus, Madrepora subulata, rosacea, and hyacin- 



