PROPAGATION OF SPONGES. 387 
detected but in one genus of full-grown marine sponges) a 
constant circulation is kept up, providing the sponge with 
nourishing particles and oxygen, and enabling its system of 
channels to perform the functions both of an alimentary tube 
and a respiratory apparatus. 
Dr. Grant describes in glowing terms his first discovery of 
this highly interesting phenomenon: “ Having put a small 
branch of sponge with some sea-water into a watch-glass, in 
order to examine it with the microscope, and bringing one 
of the apertures on the side of the sponge fully into view, 
I beheld for the first time the 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 con- 
stant 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. JI continued to watch the same orifice at short 
intervals for five hours, sometimes observing it for a quarter of 
an hour at a time, but still the stream rolled on with a constant 
and equal velocity.” 
Subsequent observations have proved that the living sponge 
has the power of opening and closing at pleasure its oscula, 
which are capable of acting independently of each other, thus 
fully establishing the animal nature of these simple organisations, 
in whom latterly even traces of sensibility have been detected, 
such as one would hardly expect to meet with in a sponge. For 
these creatures, as we are entitled to call them, are able to 
protrude from their oscula the gelatinous membrane which 
clothes their channels, and on touching these protruded parts 
with a needle, they were seen by Mr. Gosse to shrink imme- 
diately—a proof that the sponge, however low it may rank 
in. the animal world, is yet far from being so totally inert or 
lifeless as was formerly imagined. 
The propagation of the sponges is provided for in a no less 
wonderful manner than their respiration and nourishment. 
Minute globular particles of sarcode sprout forth as little pro- 
tuberances from the interior of the canals. As they increase in 
