34 LIFE AND HER CHILDREN. 
its surface, and the numberless small holes scattered 
about between them ; and on looking carefully down 
one of the large holes, you will see that it leads to a 
long tube, into which a number of small tubes open ; 
while, on the other hand, if you try to follow out any 
of the smaller holes in the same way, you will find 
that they soon come to an end, and branch out side- 
ways into each other, so as to form an irregular net- 
work of short tubes. Lastly, if you cut the sponge open 
and follow out this network, you will discover that 
it always ends by leading, sooner or later, into one 
of the large tubes. What is the reason of this com- 
plicated arrangement of holes, all opening into each 
other, and by whom has it been planned and carried 
out ? 
Again, an examination of the material of the 
sponge will show that it is not a mere structureless 
mass, but is made up of delicate silk-fibres, woven 
together into a kind of fine fluffy 
gauze. By putting a thin slice of 
the sponge under a microscope, 
it is possible to distinguish this 
gossamer tissue very clearly, and 
to see that it is quite loosely 
woven ; and that it is only because 
the texture is so fine, and the 
A thin fragment of a la y erS fit SO cI ° Sel y ° ne ab ° Ve 
bath-sponge seen under the other, that, when looked at 
the microscope. from above, it appears a solid sub- 
stance. There is scarcely a more curious object under 
the microscope than a thin slice of fine sponge, though 
it is almost impossible in a picture to show its curious 
nest-like appearance. How has this web beet? woven so 
