WORMS 171 
The annelids are divided into four classes, one of which, the 
Gephyrea, has not the characteristics which distinguish the group. 
The classes are easily recognized by conspicuous features. Some 
have bristles; others have scales; others have tentacles around 
the head and inclose themselves in tubes. Many are highly 
colored, and all are of great interest to the naturalist from the 
diversity of their habits, form, and structure, and from the analo- 
gies they bear to other and higher types of animals. 
The annelids are the highest type of worms, their organs 
having attained more special functions. The sense-organs of eye 
and ear are more developed, and the nervous system has distinct 
centers, or ganglia, the first and largest ganglion being a part of 
the head. They are found in abundance everywhere. Some 
species grow to the length of one foot or two feet. Some are 
carnivorous, others vegetarian, and many are mud-eaters, swal- 
lowing sand and mud for the sake of the organisms they con- 
tain. They themselves are food for fishes, which devour them 
in vast quantities, rooting them out of their burrows or cap- 
turing them at night, at which time they swim about. 
CLASS CHATOPODA 
(‘' Bristle-footed”’) 
The bristle-worms. This class of worms has bunches of bristles 
on both sides of each segment of the body, which serve as organs 
of locomotion, or bristle-feet. 
The bristles emanate from 
outgrowths of the body 
known as parapodia, which 
are practically limbs. The 
parapodia are sometimes 
divided into distinct lobes 
or branches. The bristles 
are of various shapes and 
often of brilliant color. They 
vent.cirr Vs 
A magnified parapodium of Nereis dumerilit: dors. 
are usually horny, sometimes «ir’., dorsal cirrus; vent. cirr., ventral cirrus; 8, sete. 
simple, sometimes divided into joints, and vary in shape in different 
genera. The parapodia have, besides the bristles, a second set of 
