476 ADAPTATIONS TO PHOTIC QUALITY 



repeating the findings on light-adapted specimens. He also contended 

 that the red end of the spectrum is shortened for all fishes (as for the 

 scotopic normal, totally color-blind, or protanopic human eye) . By driving 

 the fishes toward the red end of a spectrum with an advancing shadow, he 

 found that they would still congregate in the light when wavelengths as 

 short as 620-640m[l were still shining on the aquarium; but when the 

 shadow reached to 7,650m[A they suddenly dispersed as if they were in 

 complete darkness. When two lights were shone on the tank from opposite 

 ends, their relative intensities could be adjusted so that the fishes swam 

 indifferently through both colors of illumination. With this procedure 

 Hess found that the green was brightest, that blue, yellow, and orange 

 were less bright, and that red was darkest for the fish. The intensity of 

 any color needed to 'balance' pure yellow was only half that required to 

 balance green. Unlike Graber, he could make his fishes go to red, by 

 making it far brighter than an alternative blue light. 



Bauer worked with Charax puntazzo and Atherina hepsetus, to some 

 extent also with a species of mullet, and a bit with Box salpa. He used 

 filters of glass, gelatine, and paper and made a few experiments with 

 spectral lights. He found that his fishes (except Mugil) were instinc- 

 tively strongly negative to red (?i680-710m[A) and called this peculiar 

 phenomenon 'Rotscheu' or red-fear, red-shyness. Reighard had observed 

 it in Lutianus as noted above, without realizing of course how very many 

 species would show it. Fishes generally seem either to shun red, or to pre- 

 fer it decidedly. This paradox does not appear to have interested the in- 

 vestigators in this field; but, granting that the red is seen as such, red- 

 shyness and red-love both seem to indicate a high attention-value for red. 

 Though red is very common in the body colorations of fishes, it is prob- 

 ably rarely sufficiently illuminated to be seen as anything but black, for 

 the red rays are the first visible ones to be eliminated as light passes down 

 through water. Perhaps it is because red, distinctly visible as red, is so 

 unfamiliar to fishes that it gives them such a start in one way or the other. 

 Both the shunning and the pursuit of red may mean the same thing — 

 that the fish sees the red vividly, that it is strange, and that it fascinates 

 him. Young fish, to which everything is new and strange, seldom ex- 

 hibit red-shyness; and even old fish may get over it in a short time. 



Bauer also established that his fishes were quite indifferent to wide 

 variations in the intensity of white light. He could not get them to settle 

 down in either of any two intensities. Yet when offered red and blue they 

 would go to the blue, and no juggling of the intensities of the two colors 



