THE SPONGES OF THE WEST-CENTRAL PACIFIC 



51 



Text Figure No. 29. Portion of a section of Halisarca melana, X. 682. A: Surface. 

 B: Pore. C: Subdermal space. D: Flagellate chamber; several choanocytes show near 

 the letter. All or part of three additional flagellate chambers are also shown. Many of 

 the amoebocytes, which contain black spherules, and which are responsible for the black 

 color of the species, may be seen throughout the tissue. 



This is a thin crust less than 1 mm thick growing laterally indefinitely. 

 Specimens covering more than 30 square cm were noticed frequently. 



The endosome and ectosome color in life was jet black, and the con- 

 sistency was softly colloidal. 



The surface is shiny and smooth, and the pores and oscules so minute 

 and readily closed that they could not be discovered. 



There is no sharp separation between endosome and ectosome. There 

 are numerous elongate flagellate chambers about 30 fx in diameter and at 

 least 120 ju, long. These chambers are lined with choanocytes, 2 ll in diameter, 

 and unusually thickly crowded together. The chambers are separated from 

 each other, and also supported, by a quantity of amorphous jelly in which 

 amoebocytes can readily be discovered. These are 7 ll in diameter and are 

 crowded with dark pigmented spherules which are about 1 ll in diameter. 



This species is unique within the genus Halisarca for the shiny jet black 

 color. 



The specific name selected is derived from the Greek word meaning 



black. 



