BY R. VON LENDENFELD, PH.D. 287 



much smaller than the lacunose oscular tube, and more or less 

 circular. The oscula are scattered irregularly all over the surface 

 of the lamellie. 



The Haliue species differ from other sponges very much in 

 consequence of the great width of their canals, and the exceptional 

 thinness of the dividing membranes. 



The thickness of these dividing membranes is pretty uniform 

 0-016 mm. 



In these membranes which devide the inhalent from the exhalent 

 system we find the ciliated chambers forming one continuous, 

 uninterrupted, dense layer. The chambers are spherical, the 

 inhalent pores numerous and small. Each chamber possesses one 

 cii'cular exhalent pore, which opens into the side of an exhalent 

 canal without a special canal. The chambers take up the whole 

 of the thickness of the dividing membranes and have accordingly a 

 diameter of 1 6 mm. The ground-substance is transparent and does 

 not contain any granules. It shows in other respects the ordinary 

 appearance of the Mesoderm of the Spongidae. The skeleton 

 consists of a network of horny fibre and a dense dermal layer of 

 sand. The sand in the outer, exposed surface is very coarse and 

 forms a thick and hard armour, which is perforated by the pore- 

 canals. On close examination it appears that these sand-granules 

 are attached to one another by a kind of cement, which in its 

 optic appearance and chemical structure (susceptability to staining 

 re-agents) shows no difference from the Spongiolin of the horny 

 fibres. I do not doubt, that the sand-granules are actually attached 

 to one another Vjy Spongiolin. 



On all surfaces of the internal lamellae we find a similar armour, 

 but this is not near so thick and consists of very much finer sand. 

 Spongiolin-cement cannot be demonstrated here. 



The fibre-skeleton rises from a basal horn-plate containing much 

 sand. Radial main, and tangental, connecting fibres are very well 

 defined. 



The main fibres ramify in a penicillate manner, copying in this 

 respect the Canals. All the ascending branches assume the same 

 direction further on and so appear parallel in the distal portions. 



