CHAPTER XIII 
THE WORM GROUP 
159. The Worm Group. — Here are found several distinct 
groups of animals that in advanced text-books of zoology 
are treated separately. The word “ worm ” is an old term 
which properly describes such animals as the earthworm, 
sea-worm, leech, tapeworm, flatworm, and a few others. 
The word “ worm ” cannot be correctly used for such larvae 
of insects as the “ apple tree worm ” or “ currant worm.” 
The worm group is divided into two classes: those 
whose body is composed of numerous segments (seg'ments) or 
rings, such as the earth¬ 
worm, the sea-worm, and 
the leech; and those 
whose body is not seg¬ 
mented, such as the tape¬ 
worm and flatworm. The 
first class comprises the 
true worms, which are 
known as Annelida 
(a-nel'i-da). The second class, the unsegmented worms, have 
no single technical name, and are not believed by scientists 
to be true worms. They comprise a number of worm-like 
animals which have hardly any features in common. Here 
are found the fresh-water planarians, the parasitic tape¬ 
worms, liver flukes, and numerous round worms, of which 
the hair worm is an example. 
The planarian worm is one of the simplest of these un¬ 
segmented worms. It is found under stones submerged 
175 
Figure 163. — A Planarian Worm. 
These fresh-water worms are abundant 
during the summer and are easily col¬ 
lected for class study. 
