43 LIFE AND HER CHILDREN. 
are so arranged as to build up the small canals and 
the large tubes in their right positions; and though all 
may look confused to us, yet there is no part which the 
water cannot reach in its passage through the sponge. 
At first in the coarser sponges the fibre is thick 
and loosely woven, and though it is tough-and almost 
impossible to bite or 
digest, yet it leaves 
such large openings as 
to afford but a poor 
protection. In these 
sponges flint spicules 
are still built in with 
the fibre,scattered about 
in all directions : and, 
because of the sharp- 
ness of the spicules, 
their skeletons are of 
very little use to us. 
But little by little, in 
sponges of a finer web, 
in which the tough silky 
Cup-sponge growing in the sea. Real cu v 1 
size ; about a foot high.-//, Fignicr. fibres are so ctosely 
matted together as to 
repel all intruders, we find the sponge-animal begin- 
ning to neglect the formation of spicules, and content- 
ing itself with building in fragments of sand, making 
those gritty sponges so disagreeable to handle. And 
by and by it ceases even to do this, and in the fine 
soft Turkey sponge we find the holes so small that 
no enemy large enough to do harm could enter, while 
the densely woven fibres offer a most unpalatable and 
indigestible morsel to. any creature which might have 
