CHAPTER ix. 



AMPHIBIA. 



FIELD STUDY OF FROGS. 



CLAD in rubber boots, the student can visit the frogs at then 

 home. Walk along the bank of a creek, or wade through a marsh. 

 Try to "see the frogs before they see you." But if they see you 

 first and jump or swim away, try to follow them up and see where 

 they go. Do they soon reappear? How does their color suit 

 their surroundings? Would you suggest a more suitable color? 

 What seems to be the main idea in the colors they show ? What 

 reason for the difference of color of the dorsal and ventral sur- 

 faces? What enemies has the frog that would discover it from 

 above ? How does its dorsal color serve it ? Compare its color 

 with that of its surroundings. Why should a frog be white 

 beneath? What enemies has a frog that would see it from 

 beneath? What effect would the white color have? Suppose 

 the frog were dark below ; would it make any difference in the 

 ease with which it could be seen from below? Suppose it were 

 spotted over the ventral surface as it is over the dorsal surface? 

 When a frog is floating, how much is out of water? What parts 

 of it are out of water? In the spring watch the frogs that con- 

 gregate in ponds. Do they all croak? If not all, which ones do 

 the croaking? Watch to see how the eggs are laid. What are the 

 eggs like? How are they placed ? In still water or in a current ? 

 In deep water or shallow? Do any animals eat the eggs? How 

 long does it take for the eggs to hatch? Take the temperature 

 of the water and see if this makes any difference. Do the eggs all 

 hatch nearly at the same time, or is there considerable difference? 

 Do many of the eggs fail to hatch ? 



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