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



the base than towards the apex. The very short twigs are thickly studded with polyps, 

 the spirals being in very close proximity. The polyps themselves form heads which 

 have a great resemblance to those of Spongodes. They are 1'5 mm. high, and 0"8 

 mm. in diameter. In each polyp-head is a calyx portion, formed of rough spindle-shaped 

 spicules. Into this the oral region of the polyp cannot be withdrawn, but it lies with 

 the collar upon the margin of the cup. The calyx is attached obliquely to the twig ; 

 its outer wall is the higher, the spicules there projecting somewhat beyond the oral 

 region of the retracted polyp, in a spinous fashion. 



On the oral region may be distinguished a broad collar, composed of a ring of 

 spicules. Above these are eight pairs of large spicules with their points converging 

 towards the ends of the tentacles. These are imbedded in the base of the tentacles, 

 for which, when folded, they form a protection. 



The spicules are in general spindle-shaped, and covered with warty protuberances. 

 The large spicules of the outer layers of the stem and branches are sometimes straight, 

 sometimes curved, or approximately y^shaped. They are covered with warts ending in 

 delicate spines. Their dimensions are 2 - 8 by 0'224 mm.; T82 by 0"198 mm. ; 0'91 by 

 0"098 mm. In the thicker branches they lie irregularly in a thick layer. In the thinner 

 twigs they form longitudinal rows, being arranged parallel to the axis ; they also 

 become more slender, and are in part beset only with the delicate spines. 



Long spindles also occur, especially in the angles formed by the secondary twigs ; 

 they attain a length of 2 - 24 mm., and a breadth of 0'154 mm. Others have dimen- 

 sions of 1-014 by 0-112 mm. ; 0-91 by 0-098 mm. 



The spicules of the calyx are thick, and covered with blunt warts, spindle-shaped, 

 straight, or slightly curved; dimensions 1*27 by 0'624 mm. Those of the collar are 

 slender, slightly curved, blunt at one end and pointed at the other, bearing sharp thorns ; 

 dimensions 0"56 by 0'04 mm. 



The cover of the tentacles is composed of similarly formed, somewhat more markedly 

 curved, spicules; dimensions 0'38 by - 021 mm. The spicules which line the walls 

 of the inner canals are, in part, long, club-shaped, but commonly straight, and more 

 or less rounded at their extremities, bearing small sharp spines; dimensions 0'952 

 by - 06 mm. In addition there occur fine, small, spindle-shaped bodies, with sharp 

 erect spinules ; dimensions - 14 by 0'03 mm. ; 0'168 by - 03 mm. 



The colour of the colony appears of a coral-red, with a tint of violet, polyp heads 

 white. The spicules of the stem and of the branches are in part dark purplish red, 

 in part pale rose, at times white. Those in the neighbourhood of the four larger stem 

 canals are white. 



Habitat. — Bay of Amboina. 



