235 



rectangular forms appear to be set on edge so that the rough side is projecting, 

 thus presenting a more rugose appearance. When the verrucas are slightly 

 expanded a row of spicules is seen projecting around the opening, but when 

 contracted these Ht closely together and become hardly recognisable from one 

 another. A very characteristic feature about the crenenchyma is its deciduous 

 nature, the spicules coming off in coherent plates. 



The polyps occur over three sides of the stem and branches, leaving one side 

 of the colony entirely free. They are separated by distances of about To mm. on 

 the larger branches, but on the twigs the bases merge into one another. They 

 are slightly cylindrical when open, but dome-like when closed, and measure 

 al^out 1 mm. in height and the same in diameter. The brown crenenchyma 

 appears between the loosely set spicules and makes them very conspicuous. In 

 a very few of the twigs polyps occur on the dorsal or otherwise bare surface, but 

 when this is the case few or none appear on the reverse side. The anthocodite 

 are completely retractile. There is a distinct sub-conical operculum formed of 

 eight pairs of longitudinally arranged spindles which extend to the base of the 

 tentacles, and a collaret composed of one or two rows of transversely disposed 

 curved .spicules. The spindles of the "points" are sub-parallel but diverge 

 slightly towards the collai'et. 



The axis is horny and composed of longitudinal strands. It is very thick at 

 the base, measuring 5 5 mm. in diameter. It tapers to an almost hair-like fine- 

 ness in the twigs. It is very hard in the older parts, but soft and flexible in 

 the younger branches. The interior contains a soft, white, pulpy core. 



The spicules show great diversity in shape so that only a few of the most 

 characteristic types can be noted. In general they may be termed scales or 

 plates. They are very rough and very irregular in outline. The colour is an 

 opaque white due probably to their extraordinary solidity and thickness. The 

 following are some of the types, with measurements in millimetres : — ■ 



(«) Irregular elongated plates, 2"2 x 0*5 ; 1'5 x 0"5. 



{//) Somewhat circular plates with rugged edges, 0'25 x 0*2 ; 0'35 x 0'32. 



(r) Irregular .scales, 0-5 x 0-25 ; 0-9 x 0-4. 



{d) Plates like " side view of a caterpillar," some with a projecting spine at 

 the upper edge of one end, 0"9 x 0"25 ; 06 x 0"2. 



(e) Numerous small rough spindles, from 0-35 x 0-05 and 03 x 0-03 to 

 01 2 X 001 5. 



On the branches they are of the same types : — 



{(i) 0-9 X 0-3 up to 3 X 0-6. 



{/j) 0-4 X 0-3 ; 0-3 x 0-2 ; 0-5 x 0-2. 



(c) 0-6 X 0-5 ; 0-8 x 04 ; 0-5 x 012 ; 0-4 x 022. 



(d) 1-2 X 0-6. 



{e) 0-3 X 005 ; 0-2 x O'Ol. 



