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THE POPULAR SCIENCE MONTHLY. 



low of the rock, and in a quarter of an hour had resumed its for- 

 mer darkness/' * 



I have recently made a number of observations upon the com- 

 moner New England frogs which show that our species possess 

 the power of color adaptation to a large extent. The prettiest of 

 our frogs is the common wood frog (Rana sylvatica), a pale, red- 

 dish-brown species, nearly an inch and a half long when adult 

 (Fig. 1), but very often found in the smaller immature condition 

 (Fig. 2). It is most commonly seen on the carpets of pine needles 

 in the woods, where its color is precisely like that of the bed of 

 needles on which it lives. When found in fields and meadows 

 away from the woods it is seldom reddish brown, being usually 

 either light fawn color or dark brown. 



A fine large wood frog was brought to my laboratory August 

 8th, and placed in a glass vivarium near a window. I began to 

 study its color changes August llth, at noon, adopting as a color 

 standard the plates in Ridgway's admirable Nomenclature of 

 Colors,f and the figures in parentheses hereafter refer to those 

 plates. At the time mentioned the frog was light fawn color 

 (III, 22) on the back. That night it escaped from the vivarium 

 and wandered about the laboratory, being found the next day at 

 1 P. M. It was then much darker than before, the fawn color hav- 

 ing changed to Van Dyke brown (III, 5), and the sides being dark 

 clove brown (III, 2). Mr. Sylvatica was next placed in a dry glass 



jar, and put in a corner of the 



room with a white wall on 

 two sides of it. Three days 

 later (August 15th, 11 A. M.) it 

 was an extremely light fawn 

 color on the back (III, 22, but 

 lighter), with the sides very 

 light drab, approaching e'cru 

 drab (III, 21). 



A little water was next 

 placed in the bottom of the 

 jar, and it was put beside a 

 blackboard, where it was left 

 until August 23d. The frog 



was then cinnamon color (III, 20), with sides dark drab. I then 

 placed it in an open window on a whitish bottom, and the next 

 day it was light brown. At 2 P. M., August 24th, I put it on a jet- 

 black shelf, with black surroundings. Forty-five minutes later 

 it was very dark, nearly mummy brown (III, 10), but darker. At 



FIG. 2. WOOD FROG. Immature. 



* Poulton, Colors of Animals, p. 83. 



f A Nomenclature of Colors for Naturalists, by Robert Ridgway, Boston, 1886. 



