

JOURNAL OF ANIMAL BEHAVIOR 



Vol. 3 MAY-JUNE 1913 ■ No. 3. 



ACQUIRED SPECIFIC REACTIONS TO COLOR (CHRO- 

 MOTROPISM) IN OREGONIA GRACILIS 



H. C. STEVENS 

 From the Psychological Laboratory of the University of Washington 



Seven figures 



■fe' 



OUTLINE Page 



I. INTRODUCTION 149 



a. General statement of the instinct of decoration among Oxyrhynque 



decapods. 



b. Active and passive decoration. 



c. Description of the manner of decoration. 



d. Materials used in decoration. 



e. Supposed purpose of instinct is disguise. 



f. Statement of the problem. 



II. EXPERIMENTS 154 



a. Reaction box, sources of light and experimental conditions. 



b. Description of the mode of orientation. 



c. The effects of thigmotropism and habituation. 



d. Color reactions of crabs which had been exposed to white light. 



e. The reaction times of crabs which had been exposed to white light. 



f. Color reactions of crabs which had been exposed to colored lights. 



Acquired, specific chromotropism. 



g. The influence of color of environment upon the color of the material 



used in decoration, 

 h. The effect of blinding upon the decorating instinct, 

 i. The reactions of blinded crabs to light. 



III. CONCLUSIONS 176 



a. An acquired specific chromotropism has been demonstrated in Ore- 



gonia gracilis. 



b. Blinded crabs decorate themselves as do normal crabs. 



c. Blinded crabs do not react to light. 



d. Acquired chromotropism is probably not limited to the decorator 



crab. 



I. INTRODUCTION 



It has long been known that certain genera of the long-legged 

 spider crabs place foreign bodies upon their legs and carapaces. 

 This act is sometimes called a disguising and sometimes an act 

 of decoration according to the interpretation which is put upon 



