102 A. S. PEARSE 



prawns selected a particular color, without the presence of a 

 particular weed. Until it has been proven that such is the case, 

 we have not sufficient evidence, I believe, to permit the asser- 

 tion that any crustacean selects an environment to suit its own 

 color. 



The caddis-fly larva. — Poulton ('90, p. 77) says: "The well 

 known cases of caddice-worms (Trichoptera) are partly for con- 

 cealment and partly for defense, they are built of, . . . any 

 suitable objects which are abundant at that bottom of the 

 stream in which they live." He uses the caddis-fly case as an 

 example of "adventitious protection" where "animals cover 

 themselves with objects which are prevalent in their surround- 

 ings and are of no interest to their enemies." The experiments 

 described in this paper show that caddis-fly larvae do not select 

 objects for their cases which will make their colors correspond 

 with the general tint of the background. Nevertheless, they are 

 protectively colored as a rule. 



The spider-crab. — In 1907 Minkiewicz published an account 

 of the reactions of spider-crabs; in which he stated that he 

 had induced individuals of several genera {Maja, Pisa, Inachus, 

 Stenorynchus) to select certain strips of paper, from a variety 

 of colors, which corresponded to the background on which they 

 rested. Furthermore, Minkiewicz maintained that crabs which 

 had selected decorations of a certain color showed a positive 

 chromotropism toward the same color when they were placed 

 in a particolored dish. These results seemed remarkable for 

 Bateson ('89) had previously performed similar experiments 

 with three species from the same genera used by Minkiewicz 

 and reached quite different conclusions. He says (p. 214) : "There 

 is certainly no disposition on the part of Stenorynchus dressed 

 in any color, say green, to take up a position amongst green 

 weed or indeed amongst weed at all, and so on, while some indi- 

 viduals which have taken up their station among w^eeds do not 

 dress themselves at all." Poulton ('90) also, quoting Bateson, 

 says: "Stenorynchus does not betray any disposition to remain 

 in an environment which harmonizes with its dress." 



The writer's experiments on Libinia support Bateson 's con- 

 clusions. Before Minkiewicz 's results are accepted the species 



