ON THE VITAL POWERS OP THE SPONGIAD^. 439 



dried immediately on being taken from the sea, but that the other one had 

 been placed in a vessel of sea-water, about half an hour after removal from 

 the sea, and placed in the sun ; nearly all the orifices were then closed, 

 and it was observed by Dr. and Mrs. Lister ths.t a gradual contraction shortly 

 commenced in the membranous veils of the oscula, which continued until the 

 whole of the orifices were opened to the fullest extent, and in this condition 

 they remained. Struck by this explanation and by some other circumstances 

 of a similar nature which I had observed in other sponges, I felt a strong 

 conviction that the Spongiadse possessed the power of" expanding and con- 

 tracting the oscula at their pleasure while in a living condition, and I deter- 

 mined at the first convenient opportunity to work out this interesting problem 

 in their natural history. I accordingly located myself at Tenby, South 

 Wales, at the latter end of last May for the purpose. 



The great cave that runs completely through beneath St. Catherine's 

 Island at Tenby, is highly favourable to such observations as I contemplated 

 making, as it is studded abundantly in every direction with specimens of 

 Halichondria panicea and Grantia compressa, Johnston, and a deep orange- 

 coloured sponge, Hymeniacidon carunciila, Bowerbank, MS. On my first 

 visit to the cave, June 2nd, I carefully noted the appearance of Halichondria 

 panicea and Hymeniacidon caruncula in the condition of repose during the 

 period of low tide, while they were without water and fully exposed to the 

 influence of the atmosphere. 1 found that in Hal. panicea the greater 

 portions of the oscula were completely open, while the tubular orifices of 

 others were either partially or completely closed. On the contrary, in fifty or 

 sixty specimens of Hymeniacidon caruncula they were so completely closed 

 that I could scarcely detect even their position on the surface of the sponge. 

 I carefully removed several specimens of each species from the rocks to 

 which they adhered, taking care not to injure the basal membranes of the 

 sponges. I placed them in shallow dishes of fresh salt water, and in a short 

 time the whole of them began to pour forth streams of water from their 

 oscula with considerable force. I supplied these specimens with indigo 

 rubbed up into a fine powder and infused in salt water ; the rush of the par- 

 ticles to the outer surface of Halichondria panicea and Grantia compressa 

 rendered them of a deep blue colour in a short time, and the ex-current 

 streams continued steadily in action for more than an hour. I then poured 

 oflP the water, that they might reniaia for some hours in the same condition as 

 the specimens were in their natural locality ; at 8 o'clock in the evening 

 I filled up the dishes with fresh salt water, and in a very short time the ex- 

 current action commenced ; and I left it in full action in two specimens of 

 Halichondria panicea at 11 p.m. On examining these specimens at 10 a.m. 

 on the 3rd of June, I found that nearly the whole of the oscula, which were 

 fully distended on the previous evening, were now nearly all closed ; and 

 the mode of closing was in some cases rather peculiar ; the greatest con- 

 traction was at about half a line within the outer edge of the osculum, and 

 by this constriction the closing w£is completely effected, leaving the outer 

 part of the osculum above this constriction in the form of a shallow cup, 

 slightly elevated above the general level of the surface of the sponge. 



Of three specimens of Hymeniandon caruncula placed by themselves in a 

 saucer of sea-water, not a single osculum was apparent at 11 p.m. on the 

 previous night ; but on the following morning, June 3, at 9 a.m., several oscula 

 in each specimen were to be seen in a full state of expansion, varying in size 

 from one to four lines in diameter, and the ex-current streams were steadily 

 poured forth. 



The surface of the sponges exhibited a comparatiTely smooth and dilated 



