136 AMPHIBIA (the frog) 



(9) Color. 



(a) Keep one frog in the light, and another in the dark 



for several hours, and compare their colors. 



(b) Experiment and find out if changing the color of the 



surroundings affects the color. If possible, repeat 

 this experiment with a little tree toad. 



(10) Wrap a wet towel about a frog and pour chloroform 



over it above the nostrils. Now spread the web of 

 the foot out on a glass slide and study the circula- 

 tion under the low power of the microscope. 



Morphophysiologic Study 

 A. External Morphology 



1. Size? Length in inches? 



2. Shape. 



(1) Stout or slender? 



(2) Body divisions present? 



3. The Head. 



(1) Size. Small, medium, large, or very large? 



(2) Shape? 



(3) Movement of lower jaw — vertical or horizontal? 



(4) The Eyes. 



(a) Position on head? 



(b) Shape? 



(c) Size? 



(d) Number of eyelids? 



(e) Color of iris? 



(5) The Ears. Back of the eyes find the tympanum. 



(a) Shape? 



(b) Size? Larger or smaller than the eyes? 



(c) Use? 



(d) Pass a needle through the tympanum into the mouth 



and trace the course of the Eustachian tube. 



(e) Why has the frog no external ear? 



(6) The Nostrils. 



(a) Where located on the head? 



(b) Are they near together or far apart? 



