THE EARTHWORM AND HIS WORK . 
149 
where they may remain for several weeks. Then put 
them in a one per cent, solution of chromic acid for five 
or six days. Remove 
them from this' solu¬ 
tion, wash them thor¬ 
oughly in water and 
place them in a dish 
with turpentine, al¬ 
lowing them to re¬ 
main there for a few 
days longer. They 
may then be dried, 
when they are ready 
for use. The worms should be spread out in flat- 
bottomed dishes during the processes of tanning. 
With specimens thus prepared or simply hardened in 
alcohol, the class should write the answers to the fol¬ 
lowing questions: 
Do the worms all have the same number of seg¬ 
ments ? 
Do you find several rings together which seem to be 
enlarged ? This is the clitellum or reproductive girdle. 
How many segments from the clitellum to the head 
end ? 
Is the body of the angleworm smooth ? Does it 
appear more rough when the finger is moved in any 
special direction ? The roughness is caused by bristles 
or setcz. Do they all point in the same direction ? 
How many rows of setae along the body ? How 
many setae on a single segment ? 
Does the worm have an internal skeleton ? Does a 
thin cuticle separate easily from the body of a worm 
which has been soaking in water for a time ? 
Can you make out the shape of the segment in front 
of the mouth ? 
Summary of Drawings. ( a ) The whole worm, nat¬ 
ural size. 
(J?) The segments near the head X 6. 
Fig. 120.—An Earthworm. 
