506 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



cavities are met with. (Plate 37, fig. 1.) These are larger below 

 the inner surface than below the outer surface. The sub-dermal 

 cavities below the inner vestibule surface are irregular, tangental, 

 and mostly longitudinal canals of an irregulai'ly oval transverse 

 section. 



Their largest diameter may attain 3 mm. Such immense sub- 

 dermal cavities are rare. 



The sub-dermal cavities below the outer surface are similar,, 

 irregularly longitudinal canals, which, however, are very much 

 narrower. These are also much more flattened tangentally 

 and attain a width of 1 mm. and height of 0*5 mm. 



From these extensive cavities canals extend down towards the 

 interior of the sponge, whieh have an average diameter of 

 0*1 mm., a cii'cular or oval transverse section, and which extend 

 likewise in a more or less longitudinal direction. They ramify 

 continually, and the smallest final ramifications which have the 

 same shape as the larger canals, measure 0-02 mm. in diameter. 

 (Plate 37, fig. 1). The ciliated chambers form f of spheres and measure 

 0-032 mm. in diameter. The exhalent canals are similar in shape, 

 size and direction to the inhalent ones, and join to form larger 

 stems, which no longer extend longitudinally but curve towards 

 the askeletous portions of the sponge attaining a more and more 

 transverse direction the larger they become. The askeletous 

 portions of the sponge. (Plate 37, fig. 1), are very much less dense 

 than other parts and consist mostly of wide Lacunse, separated 

 from each other by tender membranes as in Euspongia irregu- 

 laris. These Lacunse join and finally open into the short and 

 wide oscular tube. They average a diameter of 0*6 mm., the 

 membranes which divide them from each other are only 

 0-005 mm. thick in certain places. In portions also of the 

 askeletous part ciliated chambers are found (Plate 37, fig. 1), 

 particularly in the depth; no chambers open directly into the large 

 o.scular tube which measures 1-2 mm. in diameter. 



Often the skeleton is interrupted throughout the entire width of 

 the sponge lamella between the vestibule space and the outer 



