1112 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



open into the gastral cavity by means of distant circular pores 

 l'l-2 mm. in diameter. These poi-es are pretty regularly disposed 

 towards the Osculum on an average 5 mm. apart. Near the base 

 as near as 2 mm. 



S2ncules : The skeleton consists of gastric quadriradiates, trira- 

 diates of the Parenchyma (two kinds), dermal acerates and long 

 acerates around the Osculum. Tlie gastHc quadriradiates are very 

 curiously shaped. One ray protrudes into the Gastral cavity. 

 This centripetal ray is slightly bent upwards, conic and slightly 

 rounded at the end, it measures 0-1 x 0-0074 mm. One of the 

 three other rays, which are tangental, is very much longer than the 

 other two, and points away from the Osculum. This ray measures 

 0-15 X 0"005, it is conic, slightly rounded at the end, and regularly 

 curved, turning the concave side towards the Gastral cavity or 

 canal. The angle between this ray and the centripetal one is about 

 110°, with the tangental rays about 133°. The paii'ed tangental 

 rays measure 0*05 — 0'06 x 0'003 mm. These quadriradiates are 

 met with not only in the Gastral wall, but also in the larger exhalent 

 canals. The further away from the stomach, the smaller the 

 longitudinal and centripetal rays become. Triradiates of tlie 

 Parenchyma of the two kinds. Regular ones with mostly straight 

 cylindrical rays with rounded ends, measuring O'l x O'OOo, and 

 sagittal triradiates, the unpaired ray of which is situated centri- 

 f ugally and longer than the other two with which it encloses angles 

 of about 125° ; it measures 0-15 x 0'005. The paired I'ays 

 0-08 X 0-004. All rays straight, conic and sharp pointed. Dermal 

 acerates in clusters of 15-20, immersed in the Sponge one-tenth of 

 their entire length, pointed at both ends, tapering towards the 

 terminal end throughout the projecting part nearly vertical on the 

 surface, measuring 1 x 0-007 mm. The clusters of these spicules 

 are very close to one another, so that the Sponge appears hairy 

 velvet like. The clusters are not determined in their position by 

 the ciliated tubs below, as in Grantessa. The acerate spicules of 

 the Oscular frill measure 2 x 0-0065 and taper towards the upper 

 end. The distal half is only 0-0006 thick, very flexible and moves 

 backward and forward like a soft thread, with the liquid in which 

 the Sponge is immersed. 



