452 FRANCIS B. SUMNER 



came fairly translucent, so that the underlying surface was more 

 or less visible through them. 



3. In the black-walled, white-bottomed box, different fishes 

 behaved differently, depending upon the individual peculiarities 

 of the specimens, or upon their previous treatment. When placed 

 here in the dark condition, most specimens remained fairly dark, 

 even after a lapse of some days. But they were, notwithstanding, 

 commonly affected somewhat by the white bottom, being notice- 

 ably paler than those in an all-black box, and in some cases exhibit- 

 ing a peculiar blotched or marbled appearance, as if attempting to 

 adapt themselves to black and to white at the same time." 

 In one instance, a fish became nearly as pale as did the average 

 specimen in an all-white box. 



Two fishes which had been placed in this box in the dark condi- 

 tion, and which had remained dark for four days, were transferred 

 to an all-white box. In the latter they attained nearly or quite 

 the maximum degree of pallor within a single day. Upon being 

 returned to the black-walled, white-bottomed box, they remained 

 pale for two days, i.e., as long as they were kept there. 



Two other specimens, which had remained dark for two days in 

 this box, became pale in seven hours or less when the white mov- 

 able wall was inserted. Upon removal of the latter, at the end of 

 one day, however, the fishes promptly began to darken, and be- 

 came nearly or quite as dark as before. Yet another two, which 

 were put in when pale, remained so for two days. 



Thus, while there can be no doubt as to the influence either of 

 the white bottom or of the black walls in these experiments, the 

 relative importance of the horizontal and vertical surfaces seems 

 to differ in different cases. The same is seen to be true of the next 

 sort of box considered. 



4. In the white-walled, black-bottomed box, dark fishes in 

 every case remained fairly dark, though they were in some cases 

 influenced by the white surfaces around them, for about half of 



^' No such contrasts were here produced, however, as were shown upon the 

 spotted bottom. (See above.) 



