Growing, Breathing, and Other Things 
just as interesting. On the under side 
of the Spinner’s body near the front of 
the abdomen, are two small, slit-like 
openings. Hach slit opens into a small, 
sac-like cavity. In this space are a 
number of thin plates of membrane 
lying close together like the leaves of a 
book. These are the lungs, or the 
lung-books as they are usually called. 
Through the plates numerous blood- 
vessels ramify. When the air enters 
the lung cavity, the oxygen passes 
through the thin walls of the leaves, 
into the blood, and is carried all over 
the body. 
There is a little spider that lives in 
the water, yet manages to breathe 
air, just as all her relatives do. She 
makes a unique little silk room like 
a bell. This bell rests in the water, 
mouth downward, and because it is 
filled with air no water can enter it. 
So the Spinner rests perfectly safe in 
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