Pomona College, Clarcmont. California 31 



IV. May 27. Heat and cold. Placed a frog in water of 30'^ 

 C, left it for an hour and one-half. 



At the end of this time it was decidedly lighter. 



Placed a frog in water of 3" C, left it for an hour and one-half. 

 At the end of this time it was decidedly darker. 



There was a great deal of difference in the color of the two 

 frogs at the end of the experiment. 



V. May 28. Frog in water 30^ C. Left one hour. Much 

 lighter than one in cold. 



Frog in water 3° C. Left one hour. Much darker. 



Reversed the frogs at 2:24 o'clock. 



At 2 :45, the two frogs had reached the same color. 



VL June 1. Frog in water of 30'- C, left one hour. Much 

 lighter. 



Frog in water 3° C, left one hour. Much darker. 



VIL May 26. Acid. Placed one frog in a weak acid (HCL) 

 solution. Left for several hours. There seemed to be no change 

 in color — possibly a little lighter than the control. 



Control. Placed one frog in water, otherwise its environment 

 was the same as the one in acid. 



No change in color. 



VIII. Alkali. Placed one frog in a weak alkali (NaOH). 

 Left it for several hours. There seemed to be no change in color — 

 possibly slightly darker than the control. 



EXPERIMENTS WITH A LOCAL FROG 



IX. Rana draytonii 

 May 27. 



X. Cold 3° C. Found a frog among the others identical in 

 color. 



Left in cold for one hour. Darker at the end of this time in 

 comparison with the control. 



XL May 29. Light. Placed Rana draytoyiii in sunlight for 

 an hour and one-half. At the end of this time it was very much 

 lighter. 



Control. Kept the control in semi-darkness. Did not change 

 color. 



Conclusions : 



1. These frogs change color under certain conditions of heat, 

 cold, light, dark, or excitement. Acids and alkalis have little if 

 any effect. 



2. a. Heat and light cause the frog to lighten in color. 

 There is evidence that heat is the true agent, and light only as it is 

 associated with heat. 



b. Cold and dark cause the frog to darken in color. 



