Sponge-fauna of Norway. 261 



face of the cortex, where its dense sarcodic coating becomes 

 metamorphosed into fibrous ligaments ; only in some such 

 manner as this can the additional globates needed for the 

 increased area of the cortex, consequent on the growth of the 

 sponge, be explained. It is, moreover, suggested by the fact 

 that in embryonic Geodice the globates are at first absent in 

 the cortex, and make their earliest appearance within the 

 mark. 



The stellate spicules, as we have already stated, are pro- 

 duced within the interior of cells ; they may frequently be 

 observed within a cell resembling one of the vacuolated con- 

 nective cells, with transparent sarcode filling up the angles 

 between their rays (PI. XL fig. 22) . 



Classification. — It may be thought singular to refer to 

 Geodia a sponge which apparently possesses neither the 

 cribriform oscular area nor the large body-cavity which 

 characterize that genus. But it is to be recollected that we 

 have been describing a young specimen, the structure of which 

 is in all respects so similar to that of Geodia Barretti that no 

 one could refuse to refer it to that species, and, next, that, ac- 

 cording to Bowerbank's descriptions, Geodia Barretti clearly 

 belongs to the genus to which we have assigned it ; for, 

 setting aside the absence of a large body-cavity, which is not 

 really essential to Geodia, we have the genuine Geodia cha- 

 racter displayed by Bowerbank's specimens in the possession 

 of a large cribriform oscular area. In our sponge this area is 

 represented by the walls of the oscular tube, which may, with 

 growth, become a mere shallow depression, or may enlarge, as 

 Bowerbank's descriptions show, into a cavity as much as two 

 inches in depth. 



Locality. Kors Fiord, Station No. 23. Depth 180 fathoms. 



EXPLANATION OF THE PLATES. 

 Plate X. 



Fig. 1. The cut face of a young specimen of Geodia Barretti divided lon- 

 gitudinally through the oscular tube (nat. size). 



Fig. 2. Transverse section through the wall of the oscular tube below the 

 cortex : s, sphincters ; e, excurrent vessel, cut across obliquely ; 

 r, rugae of its walls ( x 11). 



Fig. 3. Upper surface of the sponge, showing the single oscule at the 

 summit (nat. size). 



Fig. 4. Tangential section through the wall of the oscular tube, showing 

 sphincters, s, in the middle of polygonal areas (X 11). 



Fig. 5. Transverse section, showing one side of the oscular tube in the 

 cortex, the greatly thickened globate-laver, and the thin dermal 

 roof (X 11). 



Fig. 6. Transverse section through the mark and cortex, showing the 

 arrangement of the water-canals : ch, ch, chones ; a-, crypts ; 



