504 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



As the variety-name implies JSuspongia canaliculata dura is tlie 

 hai'dest. 1 kilogramm weight compresses a large specimen only 

 about 3 mm. Euspongia canaliculata elastica is very much softer. 

 1 kilogramm compresses it about 8 mm. Euspongia canaliculata 

 moUissima is a little less elastic than the two other species and 

 about as hard as Euspongia canaliculata elastica. 



Surface. 



The surface is the same in the three varieties. There are no conuli, 

 and it therefore appears very smooth. In this respect our species 

 differs widely from Euspongia officinalis and many other species. 

 With a inagnifying glass one perceives that the surface is covered by 

 a very regular network of a uniform appearance throughout. There 

 is no difference whatever in the surface of the extensive vestibule 

 spaces and the external sui-face. This network is similar to the 

 one described above of Euspongia irregularis. Tt is produced by a 

 network of I'aised lines on the surface. The meshes are 0'16 mm. 

 wide, and the lines of the network itself 0*08 mm. broad. 



The protruding net is filled with sand-grains, there are however, 

 no siliceous spicules as in Euspongia irregularis. The sand- 

 grains measure from 0-15 to 0*28 mm. In the meshes of this 

 network the pore-sieves are situated, which possess a great many 

 small pores from 8-20 in number. 



These pores are the commencement of the inhalent canals. 



Corresponding to the grooves in the skeleton described above, 

 there are askeletous portions of the sponge. These are accoi'dingly 

 disposed mostly in longitudinal lines. On their surface, which is 

 not diff'erent from the surface of other parts, except that it some- 

 times appears more or less retracted or collapsed, the small circular 

 Oscula are found which measure 1-2 mm. in diameter. The Oscula 

 are disposed in lines, and on an average 10-15 mm. apart. 



