26 INVERTEBRATE ZOOLOGY 
Note the spiracles, the external openings of the respiratory 
organs, the trachee and the lungs. A short distance in front 
of the spinnerets in the ventral surface of the abdomen is the 
single median, minute tracheal spiracle: it is often difficult to 
see. The lung spiracles are a pair of large slits near the anterior 
end of the abdomen, each one at the lateral end of a transverse 
fold of the integument. Between them in the median line is the 
genital pore. In the female spider it is covered by a large and 
complex plate called the epigynum. 
Exercise 1. Cut off the legs on the right side of the body and 
draw an outline of a side view of the spider on a scale of 
from 5 to 10, putting in only the basal portion of the legs 
but all of the pedipalps and the mandibles. Carefully label 
all the parts observed. 
Exercise 2. Draw an outline of the ventral aspect of the body 
on the same scale, putting in and labeling all the parts 
observed. 
Exercise 3. Draw the front end of the body on a scale of 10, 
showing the mandibles and the eight eyes. 
Exercise 4. Draw the pedipalp on a scale of 6. 
Exercise 5. Draw one of the legs on a scale of 6. 
Exercise 6. Cut off a tarsus and study it under a compound 
microscope, noting the shape of the claws and the hairs 
which often surround them. Draw them. 
The internal anatomy of the spider will not be studied in this 
dissection. The heart is an elongated tube which lies, enclosed 
in a pericardial space, in the dorsal portion of the abdomen. 
From its anterior end an aorta extends into the cephalothorax 
and sends off a number of large branches to the legs and other 
organs. 
