230 CALIFORNIA ACADEMY OF SCIENCES. 



argued that sunlight favors the deposition of pigment, 

 and has been instrumental in the production of the 

 brilliant colors of tropical birds. Others, on the con- 

 trary, maintain that the effect of sunlight is to bleach 

 the plumage, and that the pallor of desert forms has 

 been thus induced. .No one, so far as I know, has had 

 ihe temerity to advocate that both these apparently an- 

 tagonistic views may be correct, and yet an impartial 

 consideration of the matter seems to force us to this 

 position. Mr. Beddard has discussed in a very fair and 

 unprejudiced manner the influence of light upon pig- 

 mentation.* He has given a number of examples show- 

 ing that light frequently does not produce more brilliant 

 coloration, and that animals living in the darkness may 

 lose their color from causes other than absence of light, 

 but he has also adduced a number of cases in which the 

 color was undeniably due more or less completely to 

 light. Thus he says: " As a general rule, those insects 

 whose pupa3 are exposed are brighter in color than those 

 insects whose pupaa are concealed, either in the ground 

 or in a dense cocoon." He mentions the larva of a tiger 

 beetle (Cicindela campestris), "which lives in a hole, from 

 which its head and thorax alone protrude; and these are 

 of the same green as the perfect insect, while the rest 

 of the body is of the usual whitish yellow of a grub " 

 (Andrew Murray, Disguises of Nature, p. 9), and adds: 

 ' Here light may have been influential in distinguishing 

 the two halves of the body." Perhaps the best instances 

 of the influence of light upon pigmentation are the ex- 

 periments of Cunningham upon young flounders, which 

 developed pigment upon the white under side of the 

 body when placed in an aquarium with mirrors on the 

 bottom, and Poulton's instance of the pale cave-dwelling 

 amphibian, Proteus, which became gradually darker 



*1. c. pp. 61-70. 



