BY R. VON LENDENFELD, PH.D. 565 



Canal system. 



The whole sponge consists like the Auleninee described in Part 

 V. of the Monagraph of Australian Sponges in the last number of 

 the proceedings of this Society, of a reticulate structure in its 

 interior. (Fig. 8.) Lamellous fibres, with an average thickness 

 of 1 mm. form a network, which on any section appears very 

 regular. These fibres coxisist of a very hard tissue, with few and 

 small canals and a great abundance of spicules. In the meshes 

 between them (fig. 8) there is a very much softer tissue with 

 wider canals or irregular lacunes. Here only few and insignificant 

 spicules are found. 



Below the poresieves in the concave membranes which extend in 

 the meshes of the surface-network, lai-ge irregular cavities (fig. 16) 

 are met with. The pores ai-e situated, as stated above, in small 

 groups. The sieve membrane is very thin and delicate. The 

 pores can appai-ently be entirely closed by the sponge. The sub- 

 dermal cavity extends far down and gives off branches which 

 ramify to supply the ciliated chambers or extend to form lacunae in 

 other meshes of the interior of the sponge. Most of the lacunae 

 found throughout the interior of the Sponge belong to the inhalent 

 system. Some of the final ramifications of the inhalent system 

 are met with in the fibres of the internal network. 



The ciliated chambers are small and difficult to see, they are 

 spherical and measure 0'02 mm. in diameter ; from the chambers 

 very narrow canals originate and unite to form larger exhalent 

 canals. The chambeis seem to be situated in gi^oups. Such 

 groups occur only in the tissue of the hard fibres, as also in the soft 

 pulpa which occupies the meshes. 



The exhalent canals do not form extensive lacuna? at all. The 

 larger branches and stems are found only in the soft tissue of the 

 meshes. The oscular tubes follow the net-work in their lower 

 part, and are therefore much curved. They are narrow and long 

 and ramify in an irregular manner. 



