290 a monograph of the australian sponges, 



Surface. 



As raentioned above in the diagnosis of the genus, the surface 

 is liable to very great variations according to the development of 

 the dermal lamella. 



The whole sponge consists of a horny comb-like reticulation of 

 lamellae, (Plate XXVII., tig. 4), which is enclosed by a dermal 

 lamella. This latter is the only portion of the sponge visible from 

 without. This lamella is perforated by numei-ous pores. The 

 appearance of the surface depends on the distribution, shape and size 

 of these pores. They cannot be enlarged or constricted by the sponge. 

 In some specimens these pores are round, circular, on an average 

 2 mm. wide and 3-4 mm. apart, as in the specimen represented 

 in Plate XX VI., fig. I. Exceptionally these pores may be still 

 smaller and further apart, as it is sometimes found particularly in 

 the basal portion of the sponge. Generally howevei-, the pores are 

 larger and then they become polygonal, being so close together that 

 there would be no room for them if they were I'ound. A specimen 

 with pores of this kind is represented in Plate XXVI., fig. 2. 

 Here the pores measure 3-4 mm. across, and the tissue between 

 them is only 1 mm. wide. Rarely the pores are still larger, and 

 then of course the dermal lamella disappears altogether, as such. 

 Then the pores are as large as the cavities in the honeycomb 

 structure of the interior of the sponge. (Plate XXVII. , fig. 5.) 



There seems to be no correlation whatever between the shape 

 of the si)onge and the development of this dermal lamella with 

 its pores. 



These pores are neither inhalent nor exhalent. They are 

 indifferent. 



Vestibule. 



The most interesting peculiarity of our sponge, to which I have 

 already alluded above, is its structure. This is always the same, 

 however much the shape and surface of the specimen may change- 



The whole sponge is like a honey-comb covered by a beehive 

 perforated with numerous pores. These pores, which have been 

 described above, are in direct commuiition with the spaces beneath ; 

 they lead into them from without. 



