189 



The central portion is (jiiite homogeneous in character and is apparently 

 amorphous ; but in the younger part it is evidently composite, the small particles 

 giving different extinctions. It cannot be argued from this, however, that the 

 axis is sclerogorgic, because the boundary-lines of the different parts may be the 

 organic remains of the dead calicoblasts. At the same time, it is important to 

 note that in similar sections of Mditodes little or no difference could be found. 

 This subject is worthy of further study, seeing that it is used as a basis of classifi- 

 cation. When the internodes were decalcified, there was a considerable residue 

 of organic matter. 



The cffuenchyma is very thick (Plate VI. fig. 2), in some parts 2-5 mm. 

 It is supi)orted by small, densely packed spicules of various shapes, which make 

 it very brittle ; and hence the markedly deciduous character, so often referred 

 to. On the surface there is a layer of spicules arranged so that all their warty 

 ends project outwards, and form a specially hard protective layer. Owing to 

 the enormous jjrepouderance of spicules, it was almost impossible to cut sections. 

 Decalcification resulted in a complete collapse of the ccenenchyma. 



The nutritive system consists of (1) a longitudinally arranged set of canals, 

 one corresponding to each groove on the axis ; (2) a branching system through- 

 out the ccenenchyma connecting these with the individual polyps. The main 

 canals have soft flaccid walls, are circular in section, and have a diameter in 

 some cases of about 1 mm. 



The polyps (Plate VI. fig. 3) are scattered over the whole ccenenchyma 

 at intervals of 05 to 01 mm. There are no verruca^ so that when the antho- 

 codia^ are withdrawn the surface presents a dotted appearance. Round each 

 of the openings the spicules are grouped in eight bundles, and so form a stellate 

 figure. The expanded polyp has a length of 125 mm. 



The tentacles are 0*5 mm. in length, with a diameter of 5 mm. at their 

 base. They are flat and lanceolate, and bear a single row of short, thick, 

 cylindrical pinnules. They are first infolded so as to form a somewhat 

 elongated cone, and then the whole is withdrawn within the level of the 

 ccenenchyma. The polyp-cavities (Plate VI. fig. 2) are vase-shaped, and 

 have a depth of 125 mm., with a maximum diameter of similar dimensions. 



In some of the specimens under consideration reproductive bodies of enor- 

 mous size are present. These are situated either singly or in pairs, though in 

 some cases three are to be found. They have a diameter of about 1 nun., and 

 are apparently in an advanced stage of development. They are of the same 

 colour as the general ccenenchyma and present a glistening appearance. 



The si)icules are very diverse in charactei-. Tlie following are some of the 

 more prominent types, with measurements of length and breadth in milli- 

 metres : — 



