128 RRITiSH SPONGES: 



the oyster, and separation of its valves, the inner layer soon be- 

 comes likewise perforated, and the yellow matter is theii seen 

 projecting through the holes on both sides of the shell at the 

 same time. By removing successively the outer layers, we 

 easily discover that the internal excavations communicate freely 

 with each other, and with the apertures on the surface, and that 

 all the pulpy matter which fills them, and projects through the 

 superficial openings, is connected within so as to form one con- 

 tinuous fleshy mass pervading the whole shell." — Grant. 



Dr Grant has given an interesting history of this production, 

 which he says is distinctly irritable, polypiferous, and ovipa- 

 rous. " During the months of March and April, when these 

 observations wei*e made," says this distinguished zoologist, " nu- 

 nfierous small yellow ova were seen in the vicinity of the canals, 

 agreeing much in their form, colour, size, and mode of distribu- 

 tion with those of the Spongia papillaris and Spongia pani- 

 cea, which were then nearly in the same stage of advancement. 

 The projecting tubular papillae possess a complicated structure, 

 and a high degree of contractile power, and exhibit a singular 

 series of appearances, when the zoophyte is attentively examined 

 while at rest in pure sea-water. When under water, the papillae 

 are seen projecting from the apertures of the shell, sometimes 

 to the length of a line and a-half ; they present a wide circular 

 opening in their centre, and a rapid current of water issues 

 constantly from them, conveying occasional flocculi of a grey 

 membranaceous matter. But on being touched with a needle, 

 or withdrawn from the water, the opening gradually closes, the 

 current ceases, and the whole papilla continuing slowly to con- 

 tract, is withdrawn completely within the aperture of the shell. 

 The papillae, viewed in their contracted state, present a smooth, 

 rounded short extremity ; but when they begin to advance be- 

 yond the surface of the shell, their extremity becomes flat and 

 slightly dilated, assumes a villous appearance, with open fissures, 



