ON THE VITAL POWERS OF THE SPONGIAD^. 443 



ceased to act and was again completely closed, while the other two groups of 

 oscula were still in full action. 



I frequently examined the condition of the sponge until past 11 o'clock 

 p.^f., and found the ex-current action of both the large groups of oscula in 

 full force. The action of the ex-current streams had been more vigorous 

 and continuous than on any day since the commencement of my observations 

 of it, and the elevation of the water at the surface above the oscula had been 

 larger than ordinary, indicating a greater amount of force than usual. At 

 half-past 11 P.M., when I poured off the water for the night, the two large 

 compound oscula were in full play. 



June 9.' — At 10 o'clock I put fresh sea-water to the sponge, and within a 

 minute the ex-current action was apparent at both the large groups of oscula, 

 and in a few minutes became in full vigour. The central smaller single 

 osculum was perfectly closed, and not the slightest appearance of it was to 

 be detected with a 2-inch lens. The action in the two groups of oscula 

 continued in full force until half-past 12, when the group at the small 

 bend had ceased to act, and the smaller oscula of the group had contracted 

 to about half their full diameter. I placed a drop of water charged with indigo 

 immediately above this osculum, and watched the effect with a 2-inch lens, 

 and was surprised to find that its action was reversed, and the molecules of 

 indigo passed into it with a considerable degree of rapidity. I repeated the 

 application of the drop of water charged with indigo several times, and the 

 result was the same. Occasionally the ex-current action was resumed for an 

 instant, and a large molecule of indigo would be expelled, but the next mo- 

 ment the in-current action would be resumed. At half-past 1 I repeated 

 the application of the drops of water charged with indigo with the same 

 result,' when it suddenly broke forth again into strong ex-current action, ele- 

 vating the surface of the water immediately above it in the usual manner, 

 and continued thus to act. The reversal of the action in the osculum in 

 this instance was apparently effected by the vigour of the action in the 

 other group of oscula ; the whole of these organs being more or less con- 

 nected, not only by the intermarginal canals, but also by the general system 

 of interstitial canals of the mass of the sponge. 



At half-past 2 o'clock the action of both of the groups of oscula had 

 entirely ceased. At 10 minutes to 3 o'clock I drained oft' the water, and put 

 fresh sea-water to it, and the ex-current action from both groups commenced 

 again in less than a minute, and were in full action in about 2 minutes. The 

 action continued untill 11 p.m., when the water was drained off for the night.. 



June 10. — At 10 a.m. I put fresh water to the sponge. The ex-current 

 action commenced immediately from the large groups of oscula, elevating 

 the surface of the water as usual. The central osculum remained perfectly 

 closed, presenting the appearance of a new membrane having been formed 

 over its orifice, and be! w it on the side of the sponge 1 observed that a 

 new osculum had been formed about the same size as the largest of those 

 already existing. The stream poured from this osculum was as powerful as 

 any of the older ones, and it elevated the water at the surface strongly, 

 although the line of action was in a diagonal direction, and therefore passing 

 through a greater distance than those that were ejected in nearly a straight 

 line upward. At 11 1 left the whole of these oscula in full play. On 

 my return at 3 o'clock all action had apparently ceased. On carefully 

 examining the state of the oscula I had left in full action, I found that the 

 closing membrane of each was contracted in such a manner as to close each 

 orifice all but a centi'al opening, so small as to appear by the c:l.' a 2-inch 

 lens scarcely capable of admitting the point of a pin. I drained otf the water 



