214 



THE VOYAGE OF H.M.S. CHALLENGEE. 



The trunk has a leathery, rigid character, and a rough, granular surface. It is 

 thickest towards the upper end, and gradually diminishes in size downwards. At its 

 lower end come off thin, cylindrical stolons, which adhere to foreign bodies and sometimes 

 clasp around them. In the largest specimen such stolons are given off from the lower 

 fourth of .the stem, which is bent round horizontally. 



The stem is prolonged into the polyp-bearing head-portion, giving off larger and 

 smaller branches on all sides, and dividing at the end into two or three branches. The 

 branches stand out partly at right angles and are partly directed somewhat obliquely 

 upwards, especially the upper ones. Their ramification recalls very much that of the 

 preceding species. Usually several secondary branches come off from one short branch. 

 These branches terminate in a number of twigs. The twigs form together an umbel, with 

 a number of from five to eight divergent, stipitate polyps, which with their stalks attain 

 a length of 2 mm., with a diameter of 0'8 mm. in the head. Owing to the divergence of 

 the terminal polyps each head appears from without to be isolated and separated from the 

 next by an interspace, yet the umbels are so close to one another that the ramifications 

 of the branches are only indistinctly visible between them. The average length of the 

 branches, up to the end of the ramifications, is 8 to 12 mm.; the diameter of an umbel 

 12 to 15 mm. The little heads are .surmounted to a greater or less extent by a spicule 

 belonging to the peduncle, their own spicules are arranged e» chevron from the base to 

 the margin, but do not form tooth-like projections ; hence the tentacles are covered with 

 stifi' spicules which, when they are folded together, form a quasi-opercular covering. 



The mesoderm of the trunk is thickly packed with numerous variously-shaped spicules, 

 which form a complete coat of mail. These are thick spindles covered with knotty or 

 branched warts, placed in close successive whorls; length IS mm., breadth O'lZ mm. 

 There are also short spindles of similar shape with truncated ends, often bent, and then 

 covered on the convex side with rather stout, branched processes and warts, length 

 0-3 mm., breadth 0-12 mm. Often there occur also twin forms, in the shape of irregular 

 warty crosses and stars, measuring 0-3 by 0-17 mm. ; also little jagged calcareous bodies, 

 often club-shaped, with branched outgrowths, 0-12 mm. long by O'OB mm. thick, and 

 quite irregular forms measuring O"! by 0-06 mm. The larger spicules are usually white, 

 the smaller irregular forms orange. The stalk has always a more intense orange, or a 

 paler yellowish colour, according to the predominance of one or the other kind of spicule. 

 Where the branches begin long spindles occur, which soon completely supplant the other 

 spicules, and are chiefly placed transversely. These spindles are slender, curved, usually 

 /-shaped, and covered with fine spines, they are of a yellowish, white, or rosy-red colour. 



