150 LIFE AND HER CHILDREN. 
others as active as any animal in the sea, and the 
first step towards these is the common lugworm which 
fishermen use for bait. This worm, which makes the 
round coils of sand we meet with on the coast, moves 
freely about but is not very active, for it has no eyes 
and lives much underground, glueing together the sand 
as it passes along, and forming a tunnel for itself 
through which it can pass. Its gills are no longer round 
its head, as among the fixed worms, but it carries them 
on its back as thirteen pairs of lovely scarlet tufts. 
And now we come to the wonderful defensive 
weapons which life has bestowed upon these wander- 
ing worms. The lugworm safely hidden in its tunnel 
does not need any, but the lovely Nereis (N, Fig. 
54), which has a well -developed head, with eyes, 
tentacles, and sharp jaws, leads a much more active 
and precarious life. It hides under stones and shells, 
or moves about rapidly in the water, and can use 
its bristles not only as oars to swim with but also as 
swords, sabres, and hooks. For these fine bristles 
are not simple hairs as they appear, but have saw-like 
edges and hooked tips, and are really formidable 
weapons, both of attack and defence, although the 
smaller specimens of the creature which you find on 
the shore often look like mere threads, unless seen 
under a magnifying glass. 
But if the Nereis is beautiful and terrible, how 
much more so is the marvellous sea-mouse (A, Fig. 
5 4), which we sometimes see thrown up on the shore, 
while small ones may be found by turning up stones 
on the sand. No one would believe at first sight 
that this creature is a worm, covered as it is with 
broad scales and bristling with tufts of hair. Yet if 
