102 Dr Grant’s Observations on the Structure and 
of the apertures on the side of the sponge fully into view, I be- 
held, for the first time, the splendid spectacle of this living foun- 
tain vomiting forth, from a circular cavity, an impetuous torrent 
of liquid matter, and hurling along, in rapid succession, opaque 
masses, which it strewed every where 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 course. I continued to watch 
the same orifice, at short intervals, for five hours, sometimes ob- 
serving it for a quarter of an hour at a time, but still the stream 
rolled on with a constant and equal velocity. About the end of 
this time, however, I observed the current become perceptibly 
languid, the opaque fiocculi of feculent matter, which were 
thrown out with so much impetuosity at the beginning, were 
now propelled to a shorter distance from the orifice, and fell to 
the bottom of the fluid within the sphere of vision ; and, in one 
hour more, the current had entirely ceased. 
The following morning, I separated, with great caution, from 
the rocks, a variety of flat and branched sponges, and examined 
their currents through the microscope, with a candle, in a dark- 
ened apartment, which is certainly the mode of seeing these cur- 
rents best through the double reflecting microscope. The cur- 
rents of water were distinctly visible in every species of sponge 
which I examined ; and, even where the apertures were scarcely 
seen by the naked eye, the microscope shewed a powerful current 
issuing from them. In all the specimens, the currents were seen 
to flow continually from the apertures, however long they were 
observed ; and the discharge of excrement which always accom- 
panies the stream never fails to make its appearance, even 
though the purest water is employed. The velocity of the 
stream, in the same species, corresponds very much with the en- 
tireness of the branch employed, its recentness from the sea, and 
the fewness or smallness of the apertures in a given space. The 
branched species shew the currents best by this mode of exami- 
nation, because they can be adjusted to the microscope with least 
mutilation of their bodies, and are most conveniently managed 
irom their smallness and lengthened form. The Spongia exmlita, 
