498 ME. H. M. BEENAED OlST 



growing stocks have characters very unlike those of the larger 

 stocks close to which they are growing, and from which it is 

 probable, though not always certain, that they have been derived. 



Growtli-forms. — Very young colonies consisting of a small mass 

 of reticulum filling up an epithecal saucer are frequently met with. 

 I have, however, never met with one in which the parent calicle 

 was still recognizable. Such, however, must of course be postu- 

 lated. The appearance, in cases in which th.e wall is reticular, is 

 almost indistiuguishable from that shown by young Moatipores 

 (see figs. L & 2, Ann. & Mag. N. H. (6) xx. pi. ii.). I have not 

 found any young colonies of forms with membranous walls. A 

 knowledge of the early colonies would be very desirable : con- 

 sidering the ease with which, in a large stock, one type of calicle 

 passes into a very dififerent type, we might expect them to vary 

 considerably from the adult. 



The budding of sliallow, saucer-like calicles from the sides of 

 other shallow calicles is not likely to be very plastic. Bat among 

 other causes of form-variation, we may note the local thickening 

 of the walls. "When this is very irregular and confined to small 

 groups of calicles, it leads to the formation of bosses and knobs 

 from which branches are easily developed. In this way purely 

 branching forms many have been evolved, but the branches are 

 for the most part thick and coarse ; elegantly branching forms 

 are rare. 



Considerable variation occurs as to the depth to which the 

 colony descends in branching forms. We find all extremes : 

 merely the tips for a centimetre or two may be alive, or the living 

 layer may extend right down to the base of the stock, twenty 

 centimetres or more. 



As reef-build erSj this genus of Stony Corals lias long been 

 famous. It is a conspicuous component of the outermost edge 

 of the reef where the surf is most violent. The unfavourable 

 conditions of existence at such spots may supply us with a 

 clue to the dwarfing of the polyps, this having resulted in the 

 building-up of almost solid coral-masses. Hence again, though 

 branching forms are fairly numerous, they are insignificant as 

 compared with the rounded masses of almost solid coral-rock 

 (often many feet in diameter) which are most frequently met with. 

 In the West Indies, we read of thick tangles of branching Porites 

 spreading over the surface, but the branches are coarse, thick and 

 matted together. 



