84 A. S. PEARSE 



rotation and no more than ten successive reactions were recorded 

 for any of them at one time. Possible errors due to a marked 

 tendency of any individual to turn in a certain direction were 

 avoided by interchanging the screens and cardboards, b, c, and 

 b', c', after every five reactions. In recording reactions, animals 

 which went toward the color corresponding to that of the box in 

 which they had been kept were called " + " ; those in which 

 the crayfishes went toward some other color were " — ". Two 

 series of tests were made, on December 19 and December 31. 

 The crayfishes tested had been, in both cases, in a monochrome 

 environment since December 10. The results of the experiments 

 are shown in Table I ; they indicate no effect due to the pro- 

 longed sojourn of the crayfishes in a particular environment, 

 for there were as many reactions toward other colors as the 

 one by which the crayfishes had been long surrounded. Further- 

 more, Table II, which is based on the same reactions as Table I, 

 shows that there was no striking difference in the number of 

 reactions toward any of the colors used, i. e., no " preference " 

 for any particular color. 



TABLE II 



Number of Times Each Color Was Chosen by Six Male 



Crayfishes 



White 



December 19 48 



December 31 32* 



Total 70* 99 92 98 89 92 



To summarize, the experiments described show that though 

 the colors of the animals may change to some extent, so that 

 they more nearly resemble the background, the reactions of cray- 

 fishes to colored backgrounds are not influenced by a prolonged 

 sojourn (21 days) in a monochrome environment. 



The vSpider Crab, Lihinia emarginata Leach. — Lihinia emargi- 

 nata is easily obtained at Woods Hole and the writer 



*The numbers in this column are smaller than the others because the male 

 which had been in the white box died and, as is indicated in Table I, this animal, 

 therefore could not be tested on December .31. 



