they can live for a long time under water. I believe that they lie
near the surface for the sake of warmth, especially in the morning;
and we shall hereafter find that they often coat the mouths of
their burrows with leaves, apparently to prevent their bodies from
coming into close contact with the cold damp earth. It is said
that they completely close their burrows during the winter.

Structure.--A few remarks must be made on this subject. The body
of a large worm consists of from 100 to 200 almost cylindrical
rings or segments, each furnished with minute bristles. The
muscular system is well developed. Worms can crawl backwards as
well as forwards, and by the aid of their affixed tails can retreat
with extraordinary rapidity into their burrows. The mouth is
situated at the anterior end of the body, and is provided with a
little projection (lobe or lip, as it has been variously called)
which is used for prehension. Internally, behind the mouth, there
is a strong pharynx, shown in the accompanying diagram (Fig. 1)
which is pushed forwards when the animal eats, and this part
corresponds, according to Perrier, with the protrudable trunk or
proboscis of other annelids. The pharynx leads into the
oesophagus, on each side of which in the lower part there are three
pairs of large glands, which secrete a surprising amount of
carbonate of lime. These calciferous glands are highly remarkable,
for nothing like them is known in any other animal. Their use will
be discussed when we treat of the digestive process. In most of
the species, the oesophagus is enlarged into a crop in front of the
gizzard. This latter organ is lined with a smooth thick chitinous
membrane, and is surrounded by weak longitudinal, but powerful
transverse muscles. Perrier saw these muscles in energetic action;
and, as he remarks, the trituration of the food must be chiefly