132 Mr. W. J. Sollas on the 



u Teasing " was resorted to in the case of some tissues with 

 success, especially when it was found desirable to observe the 

 behaviour of the tissue with reagents. 



Altogether the various methods pursued have, I believe, 

 succeeded in eliciting nearly all the information that could be 

 extracted from the specimens ; and that this is very far from 

 being so complete as could be wished is to a great extent 

 owing to the imperfect manner in which histological charac- 

 ters are exhibited in sponges which have been preserved in 

 spirits without any previous treatment. Mr. Norman's speci- 

 mens are perfect as spirit-specimens ; they were not preserved 

 with a view to submitting them to detailed histological exami- 

 nation. And here it may be worth while suggesting that if 

 in the future it should be desired to preserve sponges with 

 this object, a preliminary soaking in osmic-acid solution of 

 •02 or *03 per cent, should be given to them before placing in 

 spirits ; this will effect nearly every thing that may be desired. 

 With osmic-acid-treated specimens and the help of a freezing- 

 microtome no difficulty should be experienced in obtaining an 

 almost complete knowledge of the minute structure of any 

 sponge. 



We may now proceed with the work of determining and 

 describing species, selecting to begin with the family Tetrac- 

 tiuellidsB. 



Tetractinellidae. 



Genus Stelletta, Sdt. 



Species Stelletta Normani, nov. 



Sponge (PI. VI. fig. 1) more or less spherical in shape, 

 becoming depressed cake-like with age, sessile, attached : in 

 size an ellipsoidal form measured 1^ inch in length, 1^ in 

 breadth, and l T \j in height; a cake-like form 2 by 1| by f inch. 

 From the surface of the sponge the distal ends of long acerate 

 spicules project erectly, rendering it hispid ; trifid spicules 

 accompany the acerates, and, expanding into triradiate heads 

 with simple or bifurcated rays at about one and the same level, 

 form a network-like covering concentric with the surface and 

 about it 1 - inch above it. Entangled among and adhering to the 

 ends of these spicules are numerous Foraminifera, Annelids, 

 and other organisms, as well as mineral particles ; these give 

 a dark greyish colour to the sponge, while its actual surface is 

 of a yellowish-white colour. Oscules not apparent. Pores 

 numerous, dispersed, minute. 



Skeleton. — The skeleton consists of long -shafted spicules, 

 minute hair-like spicules, and stellates. The long-shafted 



