106 ANIMAL BIOLOGY 



the receptacle as many times as may be neces- 

 sary to answer the following : 



1. Tell what you have done. 



2. Describe the movements of the hind legs in swimming. 



3. In which of these movements are the toes spread out ? 



4. In which of these movements, therefore, can the frog 



get the best hold upon the water ? 



5. In which direction must the frog push the harder in 



order to move in the direction that it does ? 



6. In what respects are the posterior appendages well 



fitted for swimming? 



7. In what respects are the anterior appendages not as 



well fitted as the legs for swimming ? 



L> How a frog jumps. 



Place a frog where there is plenty of room, 

 and get it to jump as many times as necessary 

 to answer the following : 



1. Tell what you have done. 



2. Describe the position of the parts of the legs just before 



the frog jumps. 



3. Describe the two movements made by the parts of 



the leg in the act of jumping and when about 

 to land. 



4. In which of these two movements must the frog use 



the greater force ? 



5. Which movement, therefore, throws the frog into 



the air? 



6. In what respects are the legs better adapted for jump- 



ing than the arms? 



N. Internal organs. 



To the Teacher. Put into a covered jar enough frogs 

 to supply each two students with a specimen. Put 

 into the jar some ether, or better, saturate a small 

 sponge with the ether and place it in the jar. When 

 the animals are dead, dissect them as follows : lift 

 up the skin of the ventral wall of the abdomen with 



