50 



THE SPONGES OF THE WEST-CENTRAL PACIFIC 









Text Figure No. 28. Portion of a section of Halisarca metabola, X 146. A: Surface. 



B: Canals. 



There is no distinctive dermis or cortex; and, under the microscope, 

 the endosome shows as a crumbling mass of fragments in which the flagellate 

 chambers readily may be made out. They are eurypyllous and are up to 

 60 ix by 80 jjl in measurement. The tissues of this sponge contain some 

 protoplasmic structures of a peculiar appearance, as though some of the 

 ground mass was full of parallel strands, each about 0.5 fx in diameter. This 

 fiberlike tissue may be a nonliving mesogloea or skeletal ground substance ; 

 no mineral nor horny skeleton whatsoever is present. This lack character- 

 izes the genus Halisarca. This species is somewhat distinctive for the above- 

 mentioned ground substance but most strikingly for the change in color from 

 yellow to black. 



The species name selected is taken from the Greek word indicating a 

 pronounced change. 



Halisarca melana, new 



Text Figure No. 29 



This species is here represented by the following : 

 U.S.N.M. No. 22915, My No. M. 220, here designated as type, collected Sep- 

 tember 1, 1949, by divers in Iwayama Bay, Koror, in the Palaus. The 

 depth was 2 meters, and the substrate was dead coral. 



