ON THE VITAL POWERS OF THE SPONGIADiE. 445 



The systems of large cloacal or ex-current canals are very visible by the 

 aid of a 2-inch lens while the sponge is distended and in full action, but in 

 its inactive and contracted tjondition they are not so readily to be traced. 

 About 1 o'clock I perforated the dermal membrane with a needle in two places, 

 directly above one of these large canals, and immediately applied drops of 

 sea-water charged with indigo, but no immediate result arose from this expe- 

 riment. At 5 o'clock of the same day, June 13th, I observed that the 

 punctured orifices were much smaller, and had become oval in form, and at 

 11 o'clock P.M. they were scarcely visible. At 10 o'clock on the following 

 morning, June 14th, previously to placing the sponge in water, they were 

 not visible ; but after the expansion of the sponge by the inhalation of water 

 they were barely distinguishable, but the orifices were entirely closed by 

 membrane, apparently as thick and strong as the adjoining uninjured portions 

 of the dermal membrane. 



It is thus evident that the formation of new oscula on the lines of inter- 

 marginal ex-current canals is not due to accidental circumstances, but that 

 they are instinctively formed or closed up in accordance with the physiolo- 

 gical necessities of the animal. This law is also demonstrated by the fact, 

 that when a slice of considerable dimensions was removed from the upper 

 surface of a specimen of this species, when three large orifices were generated 

 by the sections at right angles of as many large canals, none, either of the 

 large orifices thus created, or of the numerous smaller ones, remained open 

 after a lapse of twenty-two hours. 



June 14. — During the whole of this day the largest osculum of the group 

 at the small end of the sponge continued in strong and steady action ; all the 

 other oscula remaining inactive and closed. 



June 15. — No traces of the punctured wounds above the large intermar- 

 ginal canals were visible. The sponge commenced action at 10 o'clock a.m., 

 ■when water was put to it in exactly the same manner as recorded on the 

 14th, and the action was confined to the single large osculum at the small 

 end of the sponge. At half-past 11 a.m. the whole of the remaining oscula 

 opened, and commenced pouring forth streams of water vigorously. The 

 smaller oscula of the groups at the small end of the sponge were apparently 

 permanently closed, and the single large osculum had much increased in 

 diameter. 



I continued my observations on this sponge from the 16th to the 28th of 

 June, with variable results. Some days it remained perfectly inert, but it 

 generally inhaled and exhaled water with more or less vigour for some 

 hours each day ; and I could usually induce action by pouring on it a small 

 stream from a few inches above it, or by running the water over it for a few 

 minutes with a spoon. 



On the 29th I poured the water from it and some other specimens of the 

 same species at 7 a.m., and placing it in a pan on fresh fuci, I brought it 

 with me to London, where I immersed it in sea-water which I had brought 

 with me at 7 o'clock p.m. I continued to treat it as heretofore, and on giving 

 it some fresh sea- water on the Istof July, it slowly commenced action from the 

 large osculum at the small end of the sponge. On weighing it after having 

 been immersed about an hour in water, July 1st, I found it weighed 128 

 grains after having been immersed in water two hours. I was induced to 

 weigh it, from observing that it was paler in colour than usual, and had a 

 more rugged or warted surface than customary. On the 10th of June, at 

 10 A.M., I had previously weighed this sponge, first, after having been out of 

 the water the whole night, when it weighed 137 grains, and at 12 o'clock of 

 the same day, after being in water two hours, when it weighed 144 grains, 



