THE ANNELIDA. 2 67 
When the bottom of the sea is dredged, very frequently from 
deep water old shells and pieces of pottery covered over with 
tubes are brought up. These are formed of calcareous matter, 
and interlace each other in every possible manner. They are the 
abodes of the Serfu/e@—little inhabitants of the salt water, whose 
brilliant colouring strangely contrasts with their modest cell. 
These annelids live in their tubes like moths in the sheath of the 
chrysalis, its shape varying according to the species of its occupant. 
When observing serpule in an aquarium, the greatest precaution 
must be used, for at the least motion they retreat into their tubes. 
At first out of the opening there issues a scarlet bud, borne upon a 
long stem. This is the valve with which the annelid closes the 
mouth of its retreat—the porter who waits at its gate to close 
it against intruders. The button is richly painted with orange 
and scarlet, striped with white. Its upper surface is divided into 
sections by lines which radiate from the centre to the circum- 
ference, each line ending in a microscopic hook. In some species 
this valve is quite flat—a round disc; in others it is a cone— 
the apex pointing down the pipe. The outer surface is not always 
smooth. The Serfula gigantca has two branching horns, like 
those of a stag. The Serpula stillata forms its valve of three plates 
threaded together, so that this secure little creature closes its house 
with a triple door. 
When the annelid comes out of its tube, it gradually unfurls 
a splendid plume, arranged as a spiral. The filaments which 
compose the plume are exquisitely coloured; it waves it in a 
constant and graceful motion. On close inspection, it is found 
to be completely covered with vibrating cils. In most of the 
creatures this delicate apparatus rolls itself up spirally as it 
retreats into the tube. 
Properly speaking, the serpule have no distinct head. The 
upper part of the body is covered by a modification of the mollusk 
mantle, immediately beneath which is the stomach. The central 
part of the body is composed of seven segments, from each of 
which issues a pair of tubercles, which perform the office of feet. 
Out of these fleshy tubes a bundle of bristles can be thrust at the 
will of the animal. The microscope shows that there are twenty 
or thirty of these yellow-coloured, horny filaments; at their 
