STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 175 



spongCj and at the same time become hour-glass shaped in 

 transverse section (fig. 14), while each has a slight depression 

 at its extreme end (fig. 12). The extraordinary regularity 

 with which these chambers are arranged, and the very definite 

 relation which they bear to the lines of huge oxeote spi- 

 cules in the dermal cortex, will be sufficiently evident from 

 the figures referred to. The inhalant pores are thickly scattered 

 over the dermal surface between the parallel lines of oxeote 

 spicules. They lead into spaces which are at first somewhat 

 lacunar, but soon give place to sharply defined '^ inter-canals " 

 as they pass in between the radial chambers (vide figs.). The 

 gastral cortex is very thin, and the exhalant canals are con- 

 sequently very short. 



The canal system of Ute argentea, another Australian 

 species, has been figured by PolejaefF (8). It appears to 

 diff'er from that ofU. syconoides principally in the relatively 

 greater thickness of the dermal cortex, and consequent 

 shortness of the radial chambers, and in the less regular 

 arrangement of the inhalant canal system. 



In a colonial species from Port Jackson, which I have named 

 Ute spiculosa (4), we find the canal system much more 

 irregular, in accordance with an unusually strong develop- 

 ment of the mesoderm and its contained skeleton. The gastral 

 cavity is narrow and cylindrical, occupying about one third of 

 the total diameter of the sponge. The flagellated chambers 

 are long and narrow, and more or less radially arranged. They 

 do not extend nearly through the entire thickness of the 

 sponge wall, and they communicate with the gastral cavity 

 through long, sometimes branched exhalant canals. The 

 inhalant canal system consists of scattered pores on the dermal 

 surface, leading into elongated canals which lead down between 

 the chambers, but the typical radial arrangement of the canal 

 system is greatly obscured by the strong development of the 

 mesoderm, and the dense, irregular skeleton. There is a very 

 thick dense cortex on both dermal and gastral surfaces. 



In Ute Spenceri (4), from the same locality, we find 

 another species with a very strongly developed mesoderm and 



VOL. 35, PART 2. NEW SER. 



