THE FROG AS AN INTRODUCTION TO MAN 207 



"The Common Toad." Bulletin 46, Hatch Experiment Station, Am- 

 herst, Mass. 



Chamberlain, F. M., " Edible Frogs of the United States and their 

 Artificial Propagation." Report of U. S. Fisheries Commission, Part 

 23, 1897, pp. 249-261. Illustrated. 



"Frogs, Toads, and Carp as Eradicators of Fluke Disease." Reprint 

 Annual Report Bureau of Animal Industry, 1901, U. S. Department of 

 Agriculture, pp. 220-222, fig. 7. 



PROBLEM XXXVIII 



A study of the development of the frog (metamor- 

 phosis). ,* 



Collecting 



Observations. 1. Look for frogs' eggs in fresh-water ponds 

 late in March or early in April. To what do you find them 

 attached ? 



2. Collect some in a pail of water and bring them to the 

 laboratory or recitation room. Place them in a shallow aqua- 

 rium with some algse or other water plants, and keep it sup- 

 plied with water as needed. 



Conclusion. Where and when do frogs lay their eggs ? 



a. Conditions Favorable to Development 

 1. TEMPERATURE 



Observation. Place some eggs in shallow dishes, as saucers. 

 Place one lot in a moderately warm room, another lot in a 

 cold room, and a third lot on cracked ice. Observe often for 

 about ten days and record results. 



Conclusion. What is the relation of temperature to the de- 

 velopment of frogs' eggs ? 



2. OXYGEN 



Observation. Place a large number of eggs in a saucer of 

 water. Place a few eggs from the same batch in the same 



1 Toads' eggs may be used with the advantage of being laid later in the 

 season. 



