66 
LABORATORY EXERCISES 
above the legs. Note the gills. Place one of the gills in water. 
What are its character and shape? How many pairs of gills do you 
find? To what are they attached? What is their function? How 
does water enter them? Draw one of the gills which has been 
placed in water. Note the large stomach in the cephalothorax. 
The stomach connects with the esophagus, which in turn leads to 
the mouth. Just back of the stomach, and on either side, is the 
reddish liver. Note the character and the shape of the intestine. 
Note the light-colored muscles of the crayfish. What is the func¬ 
tion of these muscles? In a specimen from which the contents of 
the body parts have been removed, note the position of the nerve 
cord and ganglia. They are similar in arrangement to those of the 
earthworm. Find some of the ganglia along the cord. Where is 
the '' brain ”? The green glands, before noted, are excretory in 
function. They are below the stomach, in the front of the head. 
(See Waggoner, Fig. 179.) 
EXERCISE 67 
THE LOCUST (Grasshopper) 
If possible, collect live specimens for the preliminary study. 
Freshly killed or preserved specimens may be used for the remain¬ 
der of the exercise. (See Exercise 6.) 
I. The Living Locust. Observe the way in which the locust 
climbs a stem and the way in which it jumps. Watch the move¬ 
ments of the mouth parts. What is the general shape of the body? 
What are the nature and the use of its covering? This covering 
is the exoskeleton. Note the division of the body into the head, 
thorax, and abdomen. How can you distinguish between the abdo¬ 
men and the thorax? Look for the breathing pores, spiracles, a 
pair of which is present on each segment of the body posterior to 
the head. Watch the movements of these spiracles. How many 
legs has this insect? How many wings? 
