260 AN HOUR AMONG THE TORBAY SPONGES. 



from the crater of a vomiting volcano. The object of 

 the infused pigment is, by filling the water with 

 opaque atoms, without destroying its fluidity, to ren- 

 der the motion of the currents much more appreciable 

 oy the eye. 



There is, however, another interesting phenomenon 

 to be exhibited by our little Koseate Sponge, but this 

 will be manifest only after a somewhat lengthened 

 period of undisturbed rest, and in a larger volume of 

 water than the stage-cell will contain. Kemoving 

 the specimen to a straight-sided tank, and placing it 

 so as to be very close to the glass wall, we wait a day 

 or two, and then bring the microscope (which must, 

 in this case, be of that construction which allows the 

 mirror and stage to be removed, and the body to be 

 screwed to the edge of the table) horizontally opposite 

 the tank-side, a window (or a lamp, if at night) 

 being on the farther side. Now we see with delight 

 that from the interior of the mimic crater there is 

 projected a membranous tube, of the most exquisite 

 translucency and delicacy of structure, and extending 

 to such a height as to be distinctly visible to the naked 

 eye. Its lower extremity is commensurate with the 

 aperture from which it issues, and the upper contracts 

 to a narrow circular orifice, about half as wide as the 

 tube. It is apparent that this projecting membrane 

 is only a continuation of the common web-like tissue 

 that invests the entire surface, arid it bears, imbedded 

 in its substance, especially at its lower part, some of 

 the glassy rods, yet not so thickly as to interfere with 



