26 INVERTEBRATE ZOOLOGY 



Note the spiracles, the external openings of the respiratory 

 organs, the tracheae and the lnngs. 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. 



