172 H. C. STEVENS 



Results: IX-10-1912. 3:30 P. M. Red aquarium. Male. 

 Crab was alive. Not decorated, although ulva had floated in. 

 Yellow aquarium. Female. Animal alive. Decorated with 

 green ulva which floated in during the night. Green aquarium. 

 Female. Animal alive. No decoration, although ulva had 

 floated in. This was 10.30 A. M: Cleaned out aquarium and 

 placed in it two new individuals carefully cleansed. At 3 130 

 P. M. same day, there was no decoration. Blue aquarium. Male. 

 Crab alive. Not decorated. Black aquarium. Female. Animal 

 alive and gaily decorated with torn pieces of the colored paper. 

 There were six pieces of green, four of blue and two of yellow. 

 No crab ever made use of the papers to the extent of this 

 individual. Killed IX-11,1912 and preserved in formalin. 



Third Series 



IX-11-1912. 5:30 P. M. The five aquaria and five crabs 

 carefully cleaned. Five strips, 10 x 60 mm., of each of the 

 five papers were placed in the aquaria. Results : 9A.M. IX- 

 1 2-1 91 2. Red aquarium. Female. Animal alive. Not deco- 

 rated. Yellow aquarium. Female. Animal alive. Not deco- 

 rated. Green aquarium. Male. No decoration. Animal alive. 

 Blue aquarium. Female. Animal escaped. Black aquarium. 

 Animal alive. Decorated with a large piece of red paper on 

 its rostrum and an entire strip of blue paper on its carapace. 

 Preserved 9 in formalin IX-12-1912. 10 A. M. 



The chief conclusion to be drawn from these experiments is 

 that these crabs do not decorate themselves with materials of 

 the same color as the color of their environment. Our experi- 

 ments therefore support the results of Pearse, Mast and others 

 who have carried out similar experiments upon Libinia emar- 

 ginata. One is surprised at the prevalence of the view that 

 these animals "choose " colors of the same color as their environ- 

 ment, when the evidence upon which this view depends for its 

 support is critically examined. Minkiewicz is the only experi- 

 menter who has given assent to the doctrine of selective, pro- 

 tective, concealment. And while he attempts to explain the 

 reactions which result in concealment in a purely mechanical 



8 Formalin was unfortunately chosen as the preserving fluid. It was hoped 

 that individuals might be preserved for demonstration purposes with all their 

 regalia on them. The action of the formalin, doubtless as a result of the aldehyde, 

 has almost completely bleached the colored papers. 



