14 Thomson;, South African Corgonacca. 



10 mm., and the diameter of the primary stem about 3 mm., 

 that of the branches near the middle of the colony about 2 mm. 

 The axis of the internodes is solid, hard and dense, with- 

 out canals, and almost entirely composed of calcium carbonate, 

 with only a trace of fibrous or horny matter; it contains short 

 rod-like or needle-like spicules towards the outside. The axis 

 of the internodes is pink, that of the nodes dark brown m 

 colour. The nodes have no canals, they are composed of: (i; 

 spicular coenenchyme at the outside, \2) a thick area of horny 

 or fibrous tissue, and (3) a spicular or limy part in the centre. 

 The polyps mainly originate from three sides of the stem 

 and branches, leaving the fourth or ventral side free, 

 although those of the lateral and dorsal surface are seen from 

 this side. The arrangement of the polyps on the stem and 

 branches is not quite uniform, but the general disposition is 

 that of a series of polyps along each lateral surface, and a 

 somewhat intermittent and irregular row between them. They 

 are situated both on the nodes and internodes, and are 

 more numerous on the apical branches. The tentacles are 

 usually almost completely retracted within the calyces, the 

 latter then having an 8-partite dome-shaped appearance, with 

 a small circular opening, within which the minutest portion of 

 eight tentacles can sometimes be seen. The spicules project 

 very much on the surface of the calyces, especially near the 

 apices and are roughly arranged in rings. The polyps are 

 about 2 by 1.3 mm. in diameter, and 1.5 mm. in height. The 

 interval between the polyps varies, some are i millimetre apart, 

 others are almost in contact. 



The coenenchyme is thin, has a granular appearance, due 

 mainly to the presence of red spicules^ but partly to a few white 

 ones. Minute longitudinal, sinuous ridges and grooves occur 

 on the external surface of the coenenchyme, more especially on 

 that from which no polyps originate. 



The lower nodes are more distinct than the upper ; the 

 first from the base is 4 mm. in height, and 3 by 2 mm. in 

 diameter. One of the upper nodes is 2.5 mm. in height, and 2.5 

 by 2 mm. in diameter. The base of the colony expands into an 

 enlargement, the exact limits of which it is difficult to deter- 

 mine, owing to the presence of an encrusting Polyzoan. 



The spicules of the polyps are mostly white, they are as 

 follows: — ia) straight spindles, {b) very much curved spindles, 

 (r) spindles produced outwards at one end into two or three 

 prongs, tending to become cross-shaped, (.</) clubs, much shorter 

 than the spindles, (<?) clubs, approaching the foliaceous type. 

 The spicules of the coenenchyme are mainly red in colour, 

 they are as follows: — {a) straight spindles, (Jo) curved spindles, 

 (c) short clubs, {d) approximately foliaceous clubs, {e) oblong 

 spicules with processes, (/) spicules resembling foliaceous clubs, 

 but which have lost the shaft, they are heads or irregular 

 spheres. 



