LABORATORY DIRECTIONS 

 IN GENERAL ZOOLOGY 



THE FROG 

 Phylum Chord ata Subphylum Vertebrata 



Class Amphibia 



I. ANATOMY AND PHYSIOLOGY 



A. Activities and External Features 



Exercise 1. — Activities. 



(a) Observe living frogs in water and on a table. How is each 

 pair of limbs used for locomotion in and out of water? Which of 

 these modes of locomotion seems to be the primary one for the frog? 

 Give your reasons. Observe the position of the frog as it floats in the 

 water. Is it a good position for a quick retreat to the bottom? Ob- 

 serve just how the frog makes this retreat when frightened. Com- 

 pare the structure and uses of the limbs in the frog and other animals 

 with which you are familiar, such as the dog, ape, duck, and chicken. 

 What is the position of the eyes and nostrils when the frog is floating? 

 Of what use do you think these structural features are to the frog? 

 Is the resting position of the frog when out of water such as to enable 

 it to make a quick escape from danger? On what does the frog 

 depend for protection from other animals? Compare the frog in this 

 respect with the deer, horse, bear, turtle, rattlesnake, and man. Is the 

 frog well or poorly protected? Be prepared to list some of the more 

 obvious means of protection which familiar animals possess. 



Exercise 2. — External Features. 



(b) The following directions apply particularly to the leopard 

 frog, Rana pipiens. They may be used, however, for any of the com- 

 mon species. Examine a preserved frog or one recently killed. Rec- 

 ognize anterior and posterior ends, dorsal and ventral surfaces, right 

 and left sides; be sure you understand the meaning of and can define 

 the terms used here and later. The animal is bilaterally symmetrical, 

 that is, it can be divided into right and left halves each of which is 



