HOW SPONGES LIVE, 
8 
Having settled, the young sponge now spin 
itself out upon the rock, and grows and builds up 
fibrous skeleton, while its surface becomes irregular 
and full of large and small holes, and the true spoi 
appears. 
And now comes the curious part of the story. 
As the sponge grows larger it is clear that the < 
itt the middle of its body must be more and more- 
Fig. 12. 
Development of a young English sponge. *- 
3, The swimming sponge of Fig. II, whirl-. 4, 
The same with water squirting from the hole now formed. ". 
same further developed. 6, The perfect sponge with small fa 
where the water enters, ami large holes out ofwhich it .- 
shut (mt from the surrounding water out of which 
food can be taken, and yet these colls want 
as much as those outside. In order to 
about, the sponge animal, inst< rowing I 
solid mass of slime-Cells, ana: 
its skeleton in such a manner as to 
small canals or ] aout it- 
open, as we ha\ e seen, sooner ^v tat 
