118 Dr Grant’s Observations on the Structure 
polygonal pores, whose parietes are formed by fasciculi of 
straight, cylindrical, pointed spicula of considerable strength ; 
and we can perceive particles of matter driven with some force 
through the pores of this detached portion of sponge. Were 
the branch of the coalita not completely under the surface of the 
water, the rush of particles to its porous surface might be mis- 
taken for the result of cohesive attraction, as we see particles 
floating on the surface of water rush towards any dry, solid body 
in their immediate vicinity. If we raise the extremity of the 
branch of the coalita above the water of the watch-glass, and al- 
low the fecal orifice to continue its current under the surface, 
we see that all the particles of dust that light on the surface of 
the water are quickly conveyed along to the exposed part of the 
branch, where they are either arrested from their size, or are 
seen to rush into the pores lying on a level with the surface of 
the water. From the pores, they pass down through the in- 
ternal canals to the fecal orifice, which propels them to the sur- 
face of the water, to recommence their mysterious circulation. 
The pores of the living Spongia coalita are not very obvious to 
the naked eye ; but are seen large and distinct over the whole 
surface of bleached portions found on the shore. 
The pores of the living Spongia panicea are quite visible, with- 
out the assistance of a glass ; and the canals and fecal orifices of 
this animal are uncommonly wide. In a portion of this sponge, 
placed perpendicularly in a glass of clear sea-water, I could per- 
ceive, through the sides of the vessel, with the assistance of a sin- 
gle lens, particles of matter distinctly drawn into the pores. On 
rubbing some powdered chalk lightly on the surface of the 
sponge, and replacing it in the water, I could see, with the na- 
ked eye, at the distance of six inches, some particles of the chalk, 
which still clogged the margins of the pores, successively driven 
into the interior, and disappear. One of the ova of this animal, 
swimming about by its own spontaneous motions, like the ova of 
several other zoophytes observed by Ellis and Cavolini, happen- 
ing to come very near the surface of the sponge, I observed sud- 
denly drawn towards the opening of a pore ; and, from being 
"too large to pass in, it was held in that situation for a time, by 
the entering current, till it disengaged itself, by accelerating the 
motions of the ciliae which cover its surface : for the ova of this 
animal contain many distinctly formed spicula, and are not ca- 
