FOR WAGGONER’S BIOLOGY 
79 
tion to the surface of the water? Why cannot a frog remain under 
the water for an indefinite period? Watch the frog swim. How 
does it propel itself? Watch a frog move about outside of the 
water. What enables it to jump so far? 
II. The External Structure. 
1. What is the size of the mature frog? Of what parts does the 
body consist? What is the nature of the body covering? Com¬ 
pare with that of the sunfish. What is the color and what mark¬ 
ings are present on the upper surface? Compare the under with 
the upper surface. Why is the difference in color of advantage to 
an animal which lives in water? Note the looseness of the body 
covering. Of what advantage is this looseness? 
2. The Head. Compare the size of the head with that of the 
whole body. What is its shape? What is the size of the mouthf 
Determine in what direction the lower jaws move. Examine the 
eyes. What are their location, size, and shape? How many eye¬ 
lids are present in each eye? Gently touch the eye of the living 
frog. Note how the eyes can be withdrawn into the orbits. (The 
orbits are depressions in the skull which partially enclose the eye¬ 
balls.) Back of the eyes look for the eardrums, circular areas of 
tightly drawn skin. Locate the nostrils. What is their use? 
3. The Limbs. Compare the fore and hind limbs in respect to 
size. Note the parts of the fore limb. These are the upper arm, 
fore arm, and hand. Find the corresponding parts in the hind limb. 
They are the thigh, shank, and foot. How many fingers has the 
hand? How many toes has the foot? Compare with your hands 
and feet. Note that the hand and foot are “ webbed.” Of what 
use is this characteristic to the animal? 
4. Make a drawing of the dorsal view of the frog. 
III. The Internal Structure. Examine a preserved specimen. 
1. Open the mouth. Find the teeth near the edge of the upper 
jaw and in the roof of the mouth. In the lower jaw note the 
attachment and the size of the tongue. How is the tongue adapted 
for capturing insects? In the lower jaw note the circular eleva- 
