TUEBINARIA. 1 1 



turned away from the axial parent polyp. These buds of the second generation probably form 

 parts of rings round theii' parents. 



Each polyp of the successive generations, after growing out radially for a certain dis- 

 tance, bends up so tliat its aperture either looks up or faces the axis of the cup, according 

 to the angle at which the first ring of buds leaves the sides of the parent polyp. It is obvious 

 .that, but for this bend upwards of each generation of polyps, the successive generations, 

 budding at an angle to their parents away from the axis of the cup, would soon cause the edge 

 of the corallum to curl round against the stalk of the cup. As it is, indeed, the early cup 

 often becomes a creeping or encrusting form, when tlie angle at which the buds leave their 

 parents is large. Typically, however, the method of budding thus described leads to the 

 formation of a cup which will be deep and conical, or flat and shallow, according as the 

 budding polyps slope upwards at a smaller or larger angle to the axis. 



The outline of the rim of the young cup will, again, be perfectly regular if the buds of the 

 first ring develop at the same level ; but if at different levels, then the rim of the young cup 

 will follow the line formed by the buds round the central polyp. 



This central axial polyp is seldom, if ever, recognisable in the base even of the youngest 

 cup. It appears very early either to die down, or to be completely submerged by the ccenen- 

 chyma. This submergence of polyps is seen throughout the Turbinarians. The downward 

 ilow of nutrient matter, which is ever adding the necessary thickness to the stalk outside, 

 fills up the inside of the cup so fast that the polyps are (with some exceptions) unable to 

 keep pace with the growth in thickness of the ccenenchyma, and are, as a rule, found im- 

 mersed, often altogether obliterated. This I believe to be the usual fate of the central polyp. 

 "We may note that the downward flow of the nutrient fluids from the polyps round the axial 

 polyp of a Madrepore, in thickening the wall of the latter, typically submerges the earliest 

 formed and lowest buds. 



Although, as a rule, each Turbinarian polyp only buds in the definite ways above 

 described, when submerged by ccenenchyma, and also in thick glomerate forms, it may put 

 out fresh buds, which opeu on the rising surface of the ccenenchyma. Thus, while typically 

 young calicles are only found at the growing edges of the corallum, they may also occur in 

 patches (Plate XVIII.) at other parts of its upper surface (cf Ehreuberg's words, "riec mere 

 gemmascentibus nisi monstruose"). 



The JSpitheca. — The basal plate upon which the axial polyp develops is left behind, and 

 seems merely to form a cementing substance between the stalk and the substratum. A 

 secondary epitheca may, liowever, appear on the under sides of fronds, especially where they 

 tend to touch the substratum. It is obvious, therefore, that the Turbinarians are purely 

 coenenchymatous corals. Tlie skeleton of the axial polyp is built up entirely of the septa, 

 and their synapticular connections, forming together the cceneuchymatous waU of the polyp. 

 Out of this wall, and without any connection with the epitheca, the buds develop. The 

 epitheca has, in fact, dropped out of the skeleton in all its subsequent developments, except 

 where a secondary appearance of it takes place, as above stated. The whole corallum is built 



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