80 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



Text Figure No. 48. Two of the spicules (oxea) of Xestospongia sapra, X 781. 



The shape of this species is massive. The specimens collected in Moen 

 were about 6 cm high and 9 cm in diameter. The ones at Ailing-lap-lap were 

 mostly somewhat smaller than this, but the one from Yap is described by 

 Dr. Hiatt as being considerably larger, up to 30 cm in total length, although 

 much of its mass was filled up with contained bivalve mollusks. 



The color in life was blackish on the exterior but olive or olive-drab 

 on the interior. The consistency was very soft, specimens falling apart of 

 their own weight when taken out of water. When dry, they became very 

 crumbly. Considerable slime was given off, and the first alcohol into which 

 the specimen was put became somewhat like molasses in appearance and 

 consistency. 



The surface has a very distinctive finely conulose nature, about four 

 conules for each square mm. These structures are so small that it might be 

 better to describe the surface as rugose. As seen with the microscope, each 

 of these tiny prominences is extremely irregular in shape. There are skeletal 

 pores about 180 fi by 360 p in size, filled with genuine pores 20 p to 50 p. in 

 diameter, often about 20 such to each skeletal pore. These genuine pores 

 are not uniformly distributed, but are frequently grouped in bunches of two 

 or three. The oscules are about 2 mm in diameter and 1 to 4 cm apart. There 

 is no special ectosome, unless one considers that the concentration of black 

 pigment near the surface might be so regarded. There is no sharp boundary, 

 however, but a blending between the darker ectosome and the slightly paler 

 endosome. The latter is confused in structure, with spicules packed around 

 gross chambers, as characteristic of the genus Xestospongia. The round 

 flagellate chambers are about 30 p in diameter. 



The skeleton consists principally of oxeas, often about 5 p by 185 ju, in 

 dimensions. Some are as large as 6 ju, by 150 p, others as small as 2 p by 

 120 p. These smaller ones are so very numerous that it is questionable 

 whether they constitute a separate category, or merely are juvenile forms. 



It may be that cxigua of Kirkpatrick actually is the closest relative of 

 sapra, but exigua is described as being gray in color and definitely hard in 

 consistency. Its spicules were considerably shorter, and there is added for it 

 the strange statement that its ascending tracts were hollow. 



The specific name sapra is derived from a Greek word for "rotten wood," 

 as this amply describes both the texture and optical appearance of the sponge 

 in question. 



