138 THE MECHANIC AL FUNCTIONS. 



that power of contraction which had, for so many 

 ages, been ascribed to it.* 



Dr. Grant has also shown the trne nature of the 

 currents of fluid issuing at different points from the 

 surface of these animals, as well as the absence of 

 all visible movements in the orifices which give exit 

 to the fluid. Never did he find, in his experiments, 

 the slightest appearance of contraction produced in 

 any part of the sponge, by puncturing, lacerating, 

 burning, or otherwise injuring its texture, or by the 

 application of corrosive chemical agents. He gives 

 the following account of his discovery of the fluid 

 currents ; " I put a small branch of the Spongia 

 coalita, with some sea-water, into a watch-glass, 

 under the microscope, and, on reflecting the light 

 of a candle through the fluid, I soon perceived that 

 there was some intestine motion in the opaque 

 particles floating through the water. On moving 

 the watch-glass, so as to bring one of the apertures 

 on the side of the sponge fully into view, I beheld, 

 for the first time, the splendid spectacle of this 

 living fountain, vomiting forth, from a circular 

 cavity, an impetuous torrent of liquid matter, and 

 hurling along, in rapid succession, opaque masses, 

 which it strewed everywhere around. The beauty 

 and novelty of such a scene in the animal kingdom, 

 long arrested my attention, but after twenty-five 

 minutes of constant observation, I was obliged to 

 withdraw my eye from fatigue, without having seen 

 the torrent for one instant change its direction, or 

 diminish, in the slightest degree, the rapidity of its 



* See his papers on this subject in the Edinburgli Philosophical 

 Journal, vol. xiii. p. 95 and 333, from which most of the facts 

 mentioned in the above account are taken. 



