294 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



seawater, in the manner described in my paper on Anstralian 

 Aplysinidse (1), I obtained the specimen figured, and I think that 

 the pores in the sieve-membrane will never be much more dilated 

 than there. 



The pores in the interior are of course not surrounded liy such 

 large sand-gi-anules as those in the outer sui'face, one of which is 

 represented in the figure (Plate XXVII., fig. 9.) 



Below the sieve-membrane we find a short cylindrical canal 

 leading into the sub-dermal cavity (Plate XXVII., fig. 7, Plate 

 XXIX., fig. 12.) 



As mentioned above, these canals are liable to movements in the 

 interior; where the skin is soft; but they do not change in the 

 outer surface, where they are surrounded by a hard immovable 

 cortex. Consequently we find shape and size of these canals subject 

 to great variations in the interior where they are sometimes very 

 much constricted and then appear very nai'row, wliereas those in 

 the outer surface are always of the same size. 



The cortex being much thicker outside than internally, we find 

 these canals also much longer where they traverse the outer cortex 

 than anywhere else. 



Below, these canals expand conically and open into the common 

 sub-dermal cavity which undermines the whole of the surface. 



The flat lacunae, which, tangentally extended and underlying 

 the outer skin form the sub-dermal cavity are interiu])ted here 

 and there by low columns of tissue connecting the skin with the 

 body. The cavity itself is very irregular (Plate XXIX., fig. 12) 

 and from its lower limit numerous inhalent canals originate with 

 trumpet-shaped extensions, which mostly tend upwards (Plate 

 XXIX., fig. 12). 



These canals are rather irregular, more or less cylindiical, and 

 measure O'06-Ol. mm. in diameter. 



They are mostly simple as in Aplysilla. Ramifications are only 

 rarely met with. Where they do occur the ramification is 



(1) B. von Lendenfeld. Ueber Ccelenteraten der Siidsee. TI. Mitthei- 

 lung Neue Aplysinidse, Zeitschrift fiir wissenschaftliche Zoologie. Band 

 XXXVIII. 



