ACQUIRED SPECIFIC REACTIONS TO COLOR 155 



This species alone was used in our studies. These studies were 

 aimed at a solution of the following problems: 



The color reactions of crabs which have been exposed to 



white light. 

 The color reactions of crabs which have been exposed to 



colored light. 

 The influence of the color of the environment upon the 



color of the material which is used for decoration. 

 The effect upon the disguising instinct, of blinding the 



crabs. 



5. The orientation of blinded crabs to light. 



6. The function of the dorsal hairs. 



All reactions to color were carried out in a light-proof reaction 

 box which was 45 cms. in length, 30.5 cms. in breadth, and 

 17.5 cms. in depth. Two windows 8.5 cms. by 11 cms were 

 cut in one end of the box. A partition 10 cms. by 17.5 cms. 

 was nailed to the bottom of the box midway between the two 

 windows. At the opposite end of the box, a V-shaped pen was 

 made by nailing a strip of wood 10 cms. wide by 17 cms. long 

 perpendicularly to the floor of the box and so placed as to bisect 

 the corner angles of the box. An opening 5 cms. in breadth 

 was left at the apex of the pen and on the side towards the 

 source of light. Colored lights were obtained by placing colored 

 glasses or filters in the windows which have already been men- 

 tioned. See Figure 1 for a plan of the box. A square hole, 

 large enough to admit the head of the observer, was made in 

 the lid. Light was excluded by means of a hood of cloth. 



The sources of light were three glasses and two filters. The 

 glasses were ruby red, a green, and a colorless glass. The color 

 analyses and spectral transmission of these glasses were made 

 by the Bureau of Standards of the United States Government. 

 These analyses are given below. According to a statement 

 made by the Director of the Bureau of Standards, 'The prop- 

 erties of the clear glass are so nearly those of absolutely color- 

 less glass that we have not undertaken the very expensive 

 investigation that would be necessary to determine them." 

 The yellow light was obtained by means of a potassium dichro- 

 mate solution (10 gms. to 300 cc. of distilled water) contained 

 in a flat-sided glass filter the cubic dimensions of which were 



