38 LIFE AND HER CHILDREN. 
take place in those cells which lie all round the 
outside of the rest ; each one of them puts forth a 
minute whip-like lash called a cilium (from cilium, 
an eyelash), so as to form a fringe round the whole 
body, and then the young sponge, being ready to 
make its own way in the world, bursts through the 
skin of the bag, and wav- 
ing its lashes, swims out 
an oval-shaped body (2, 
Fig. 1 1) into the sea. 
Here, you will notice, 
we have a body, not 
. made as in the simplest 
The birth of the Sponge. Adapted . . f 
from Carter. slime-animals of a mere 
1, Sponge-egg, a, The yelk within piece of slime, but COm- 
the envelope, b. posed of a number of 
2, Young sponge swimming:, c, ,, ., , 
Nipple projecting where a large cells, the inner ones round 
hole will.afterwards form, d, Root- and without lashes, like a 
cells by which the young sponge f Am(eba while 
afterwards fixes itself to the rock. fe r 
the outer ones, each with 
his little whip, are like a colony of monads (see Fig. 3), 
surrounding the animal. 
By means of these it swims along and feeds ; and 
as it grows, a small nipple, c, afterwards to become a 
hole, appears at the tip, while a group of larger cells (d} 
collect at the hinder end. By means of these cells 
the little animal attaches itself to the spot where it is 
to spend the rest of its life, sometimes to a pebble, but 
generally to the solid rock. Small sponges often fix 
themselves to living shells, and Dr. Johnstone tells us 
that he met with a sponge on the back of a crab, 
which walked about quite unconcerned with its light 
burden, though it was many times larger than itself. 
