34 
LIFE, IN ITS LOWER FORMS. 
body. But whither goes this current 1 The pores lead 
into large channels, which also run through the body, like 
the drains from individual houses, which run into the 
main sewers ; and these open on the exterior of the body 
by more or less conspicuous orifices called oscula, or mouths. 
From these latter the effete water is poured in forcible 
streams, and thus a circulating current is maintained. 
It was Dr Grant who first established the fact of this 
current from personal observation. His account of the 
discovery is full of interest. “ I put a small branch,” he 
observes, “ of the Spon/jia coalita, with some sea- water, into 
a watch-glass, under the microscope, and, 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 toi’rent 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 course. I 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.” The vehemence of the current then began 
to diminish, and in about an hour ceased.* 
No one can have looked with any attention at the rocks 
* Edin. Phil. Joura. xiii. 102. 
