32 THE AQUARIAN NATURALIST. 



ing phenomenon when placed in a watch-glass with 

 sea-water under a microscope. 



" The Spongia panicea presents the strongest cur- 

 rent which I have yet seen, and has the greatest thick- 

 ness of body of any spreading sponge which I have met 

 with on the rocks of this part of the Frith of Forth. 

 Two entire round portions of this sponge were placed 

 together in a glass of sea- water, with their orifices 

 opposite to each other at a distance of two inches ; 

 they appeared, even to the naked eye, like two living 

 batteries, and soon covered each other with flocculent 

 matter. I placed one of them in a shallow vessel, 

 and just covered its surface and highest orifice with 

 water. On strewing some powdered chalk on the 

 surface of the water, the currents were visible to a 

 great distance ; and on placing some pieces of cork or 

 of dry paper over the apertures, I could perceive them 

 moving by the force of the currents, at the distance of 

 ten feet from the table on which the specimen stood. 

 A portion of soft bread, pressed between the fingers 

 into a globular form, with a diameter larger than that 

 of the orifice, and placed over it, was not moved away 

 in a mass by the stream, but was gradually worn 

 down by the current beating against its sides, and 

 thus propelled to a distance in small flakes. A por- 

 tion of unburnt coal, twice the diameter of the ori- 

 fice, was instantly rolled off the mouth of this living 

 fountain, in whatever position I attempted to make 

 it rest upon it. A globule of mercury of equal dia- 

 meter with the orifice, let fall upon it through a glass 

 tube, was not removed nor shaken, and completely 

 stopped the current. I now pierced with a needle a 



