HOW SPONGES 1.1 \ A. 
45 
Fig. 15- 
but against the smaller but dangerous animal 
might be washed into it. In another spoi 
ulcs point towards the mouth at the top, so thai 
creature which has got in can be easily thn 
but one trying to get in would be spiked directly. 
Lime - sponges 
arc to be found in 
most parts of the 
world, and some of 
them arc very beau- 
tiful from the ar- 
rangement of their 
spicules. But these 
look, after all, like 
mere rough attempts 
at spike - building 
when compared with 
the wonderful spic- 
ules which arc 1 made 
by the flint-build- 
ing sponges. 
Fig, 1 5 shows 
only a very few of the forms of flint spicules which 
are known. They look, under the micros 
if the sponge-animal were an artist trying 
many curious patterns he could invent; and 
Dr, Bowerbank has shown that each 
shapes has some special use, cither in 
enemies, in supporting the sponge, or in • 
entangling the smaller animals which form the I 
of the sponge animal. ( >t'tcn as man 
to seven different shapes may be found ii 
sponge, forming N\ theii coml 
Spicules of flint round in tl 
flint-sponges, R 
almost invisible to the nal 
