130 THE VOYAGE OF H.M.S. CHALLENGER. 



which branches come oflf at right angles at moderate intervals, and these may bear again 

 secondary branches coming oif nearly at right angles. The stem and tranches are slightly 

 thickened at the ends. In the single specimen in the collection three larger branches 

 arise on one side, of these three the second bears a secondary branch coming off from it 

 below and the third bears two secondary branches which are directed upwards. From 

 the other side of the stem there arises only a short unramified branch which comes oft" 

 straight. The height of the main stem is 50 mm., its thickness above the base 0'5 mm. 

 The first branch arises at a height of 18 mm. above the base. Length of the second 

 branch 23 mm., of the third 21 mm., of a secondary branch 10 mm. The thickened ends 

 of the branches have a diameter of 1 mm. On the stem and branches the polyps are 

 placed mainly on the two sides in alternating rows, on the thickened ends of the branches 

 they are arranged spirally around the whole periphery. 



The calycular portion, within which the anterior part of the polyp can withdraw itself 

 up to the tentacular operculum, forms only a low prominence, scarcely projecting above 

 the ccenenchyma, with a diameter of 0"5 mm. 



The oral region is surrounded by eight groups of upright spicules. The tentacular 

 operculum is formed by the bases of the tentacles, on which only a few spicules occur, 

 to the number of two or three, with converging apices, when the tentacles are folded 

 together they do not quite fill the mouth of the calyx. The operculum scarcely projects 

 above the margin of the calyx and is only slightly higher in the middle than at the edge. 



The ccenenchyma is thick and filled with large, spindle-shaped spicules, which lie 

 close together and are arranged mainly in a longitudinal direction on the stem and 

 branches. They are thick and somewhat flattened, at times curved, sometimes but 

 rarely regular, straiglit spindles. Frequently they are thicker towards the one end and 

 show a tendency to become club-shaped. They are thickly covered with large, rough- 

 surfaced, and sometimes branched warts. The warts on the outer side are always larger 

 and generally provided with spine-like or l)ranching outgrowths. The spicules measure 

 0-43 by 0-12 ; 0-3 by 0-12 ; 0-46 by O'OS mm. 



In the calyx the spicules are thickly placed around the periphery, generally, like the 

 calyx itself, upright upon the ccenenchyma. They are now more club-shaped, curved or 

 straight structures which are provided only with a few sharp spines ; or the}' are struc- 

 tures provided with sharp, sometimes branching spines, and usually somewhat flattened. 

 Their apices project frequently above the margin of the calyx, so that the latter appears 

 to be surrounded by a crown of spines. The size of the spicules of the calyx is 0'2 by 

 0-03; 0-25 by 003 ; 03 by 0-033 ; 0*2 by 0-04 mm. In correlation to the manner iu 

 which tlie calyx, within which the anterior portion of the polyp can completely withdraw 

 itself, is armed, we find the tentacular operculum only feebly developed. In the base of 

 each tentacle there are usually two convergent, slender, curved spicules, l)etween which a 

 third may sometimes lie. 



