THE SPONGES OF THE WEST-CENTRAL PACIFIC 



229 



Text Figure No. 157. Spicules of Jasplakina nux. A: Oxea, X 182. B: Triact, X 182. 



C: Portion of a triact, one arm broken off sharply, X 782. D: Microtriact, X 782. 



E: Oxyeuaster, X 782. F: Raphide, X 782. G: Microxea, X 782. 



canals. It is packed with the smaller spicules, and contains some of the triacts. 

 From each of the pores, a canal descends into the sponge interior, practically 

 perpendicular to the surface. These canals have a diameter of about 40 ll, 

 like that of the pores. As they penetrate more deeply into the endosome, they 

 branch frequently, and a somewhat confused structure results. There are 

 numerous flagellate chambers which are eurypyllous, 40 ll by 60 ll in dia- 

 meter. A suggestion of radiate structure is afforded by the fact that the larg- 

 est spicules of the endosome are practically always perpendicular to the 

 surface. 



The skeleton comprises these above-mentioned large oxeas, about 12 ll by 

 830 fi in size. Also there are very numerous oxeas, about 2 ll by 100 ll, and 

 very small microxeas, 0.5 /x by 25 ll. There are oxyeuasters with rather 

 smooth rays, 15 ll to 36 ll in total diameter. These undoubted asters have four 

 or more rays. Then there are spicules which may be regarded as euasters and 

 have only three rays. Some of these spicules which give indication of being 

 derived from the preceding category are only 22 ll in total diameter, the rays 

 being about 12 ll long. A few are present which have still larger rays, and 

 some occur with rays which are at least 6 ll by 250 ll. Furthermore, some 

 broken fragments seem to indicate that there were also present triaxon 

 spicules with rays as thick as 10 ll, and perhaps these may have been even 

 longer than the above-mentioned 250 ll. The latter spicules obviously approach 

 the calthrops condition, as found in the family Halinidae. 



This sponge is quite unique, but may be compared to a certain extent 

 with Dorypleres biangulata Lindgren, 1897, page 483, from the East Indies. 

 This had larger oxeas and did not have the smallest microxeas nor the very 

 distinctive large triaxon spicules. It was, however, similar in general appear- 

 ance, and, in particular, it had the coloration of the species nux. 



The name here selected is derived from the classical word indicating 

 "night" and refers to the black color. 



