ON THB VITAL POWERS OP THE SPONOIAD^. 44f 



same sponge in contact in pairs ; at half-past 1 1 p.m., on pouring off 

 the water carefully, I found some of the pairs had slightly adhered to each 

 other. 



I left them in contact without further disturbance, and it is evident that 

 adhesion will, to a certain extent, be effected in eight or nine hours, an 

 amount of exertion of vital action that was scarcely to have been expected. 

 At half-past 9 o'clock on the following morning, June 6th, I found the junc- 

 tion of the four pairs of sponges had been strongly and completely effected 

 during the night, and while deprived of water. The united portions in two 

 of the pairs were three-eighths of an inch in length. No traces of the lines 

 of separation that existed on the previous day could be detected with a 2-inch 

 lens, and the uniting membrane stretched from one to the other, without the 

 slightest depression or indication of the former state of separation. Thus we 

 find a strong and complete junction effected in each of the four cases in so 

 short a time as eighteen hours. 



None of these specimens when taken from the rock were compressed or 

 otherwise injured, and in none of them were there any oscula visible. On 

 the following morning, when supplied with sea-water after having been left ex- 

 posed to the air and without water during the night, the numerous oscula 

 made their appearance, and the ex-current action became general and very 

 vigorous, creating currents in every possible direction at the surface of the 

 dish of water in which they were kept. 



June 7. — I examined them again at half-past 9 o'clock, and found the 

 adhesion between the specimens had been strengthened ; I gave them fresh 

 water, but not finding any action taking place at 12 o'clock, I removed them 

 and pickled them in bay-salt and water. 



I repeated this experiment on the adhesion of individuals of the same spe- 

 cies many times and always with the same results. Specimens oi Hal. panicea, 

 when placed in contact, also adhered to each other, but they did not appear 

 to adhere either so rapidly or with so much force as in Hym. caruncula. 

 When specimens of Hal. panicea and Hym. caruncula were placed in close 

 contact, no adhesion whatever took place. 



I fully expected this result, as I had often examined the two species grow- 

 ing closely pressed against each other on the rock, and always found that, 

 although the contact was close and apparently forcible, no adhesion could 

 ever be detected. 



On several subsequent occasions I placed pairs of specimens of Hymenia- 

 cidon caruncula in contact at about 1 1 o'clock p.m., after draining the water 

 from them, and in every instance I found the adhesion took place as readily 

 without, as with immersion in water. 



Reparative powers. 



The remarkable activity of the vital power, as displayed in the rapidity and 

 strength with which individuals of the same species adhered to each other, 

 naturally led me to imagine that the power of repairing injuries would be no 

 less great than that of simply coalescing, and I determined to investigate 

 this branch of their economy. 



June 8. — At half-past 1 p.m. I wounded a specimen of Hymeniacidon 

 caruncula, rather exceeding 2 inches in length, in two places. In one case 

 I made a clean cut across it nearly half an inch in depth ; in the other I 

 out a notch in it about three- fourths of an inch in length, and the eighth 

 of an inch wide and deep. At 5 p.m. a manifest alteration had taken 

 place in the latter case. The edges of the wouad at the dermal membrane 

 were no longer angular, but were rounded off, and a very thin membrane 



