THE FROG AS AN INTRODUCTION TO MAN 209 



fertilized frog's egg will begin to show head, body, and tail. 

 Small gills grow from the neck region, and in about two weeks 

 the young tadpole emerges and swims about. 



2. Where do the 'tadpoles arrange themselves in the aqua- 

 rium ? Of course you see to it that they are in a balanced 

 aquarium as near as possible, and no fish therein. Why ? 



Conclusions. 1. How do young tadpoles breathe ? 



2. Upon what do they feed ? 



Observations. 1. Trace the development of a young tad- 

 pole, either by studying specimens of various ages, prepared 

 mounts, and charts or figures. Do they have gills for any 

 length of time ? 



2. Do the tadpoles ever come to the surface ? 



Conclusions. 1. Do tadpoles need a tail ? Explain. 



2. In what two different ways do tadpoles breathe ? 



Observations. 1. Which pair of legs develops first ? 



2. What soon happens to the tail ? 



3. Does the mouth remain the same ? Can you find teeth 

 in a frog's mouth ? 



Conclusions. 1. When is a tadpole's tail no longer needed ? 



2. How does an adult frog differ from a tadpole, breath- 

 ing, locomotion, food, etc. ? 



3. Write a paragraph tracing the different stages in the 

 development of a frog. 



c. The Toad (Optional) 



Observations. 1. Look in ponds in early May for eggs much like 

 frogs' eggs, but in strings instead of masses. Bring to the laboratory and 

 watch their development. If possible catch some toads and place them 

 in an aquarium. Watch for the laying of eggs. 



2. See that some of the females are separated from the males. Watch 

 to see if they lay eggs. If so, place some of them in a shallow aquarium, 

 as in directions under a. Do they develop ? If not, explain. 



Questions 



1. Explain the story, " Toads are often rained down." 



2. Of what value is the toad to man ? 



SHARPE'S LAB. MAN. 14 



