12 B. W. PRIEST ON THE HEXACTINELLIDiE. 



The framework of both species shows how the hexradiate type is 

 maintained throughout, although at first appearance it seems lost in 

 the process of growth. 



You will see that the fibre of both is formed by an extension of 

 silicified sarcode, over a regular arrangement of sexradiate spicules, 

 indicating that, whilst in a young stage, what is now siliceous was 

 then horny, but that during the progress of growth of the sponge, 

 silica was deposited, which gradually extending over the fibre, enclosed 

 the original spicules. This conclusion was arrived at from the fact 

 that in some specimens of Farrea occa and Aphrocallistes Bocagei, 

 the anastomosing fibre was charged with minute sex-radiate and 

 scopuline spicules of the sarcode imbedded in a confused way, show- 

 ins:' that the silicitication of the fibre was more or less of a secon- 

 dary formation. 



Fig. 10, PI. Ill, shows the lattice-work of Farrea occa, Fig. 12, 

 the same of Aphrocallistes beatrix, and Fig. 11, PI. Ill, a frag- 

 ment of Farrea occa, after Carter, enclosing a scopuline spicule 

 with pointed rays. 



All the sponges of this family will stand boiling in nitric acid, 

 losing only the organic matter, the skeleton coming out a beautiful 

 structure as if made of the purest glass. Of course the rosettes and 

 minute spicules of the sarcode falling through the meshes and col- 

 lecting at the bottom of the vessel, can be washed with water care- 

 fully, and mounted so as to be examined with higher powers than 

 can always be used when they are in situ. 



We must now pass on to the second Family of this Order, or 

 those sponges whose skeleton spicules are held together by amor- 

 phous sarcode. 



Perhaps foremost will stand tlaeHyalonema, the now well-known 

 Glass rope Sponge, first brought over from Japan, and described 

 by the late Dr. Gray in 1835, subsequently dredged off the 

 coast of Portugal, and since then at various places by the "Porcu- 

 pine," " Challenger," and other expeditions. This sponge having 

 been now so often and well described, along with the deceptions 

 practised by the Japanese regarding its position, &c, I shall take 

 one of a comparatively new genus, named Rossella, after Sir John 

 Ross, who brought over a few spicules only. This genus contains 

 three species, viz., R. Antarctica (Carter), R. Fhillippensis (Gray), 

 and R. velata (Thompson). Taking Rossella Phillippensis, that 

 being the specimen I have on the table, it is, in form, generally glo- 



