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LAURENS: MONOCHROMATIC LIGHTS. pits 
clamata, which were positive in white light, when exposed to different 
colored lights obtained by passing white light through colored solu- 
tions, turned away from red light, and moved toward blue light; that 
they also moved toward green and yellow light, but were not oriented 
by either. When given the choice between red and green light, which 
were admitted at opposite ends of a receptacle, the frogs moved away 
from the red to, or toward, the green. When given the choice between 
red and yellow, they moved away from red to yellow; and when given 
the choice between red and blue, they moved immediately toward the 
blue. 
Reese (:06) found both Necturus and Cryptobranchus to be negative 
to white light, the head of Necturus and the tail of Cryptobranchus 
being the most sensitive regions. In both of these forms, blue light 
was found to be more effective in bringing about responses than was 
red. 
Holmes (:07, p. 349), in discussing the light reactions of frogs, said, 
‘in all animals thus far investigated it is the blue and violet rays that 
are the most influential in evoking the phototactic response; the 
effectiveness of the other colors of the spectrum diminishes in order 
from blue to red. If frogs are placed in a box illuminated through 
one end with blue light, and through the other with red, they soon 
gather at the blue end. If they have the choice between yellow and 
green, they go toward the green; in general it may be said that where 
they are able to go toward one of two colors of equal intensity they 
move to the color lying nearest the violet end of the spectrum.” 
Eycleshymer (:08, p. 304), while rearing larvae of Necturus, 
placed strips of black, white, red, yellow, green, and blue paper beneath 
the glass aquaria in which they were kept. At first, he could observe 
no “preference” for one color over another, though later he obtained 
evidence “that by far the highest percentage of larvae were found 
over the green, whether this was placed on the side of greatest or least 
diffuse daylight.”” Decapitated larvae “were most frequently found 
on the colors in the half of the spectrum toward the violet end.” 
Pearse (:10, p. 176) found that the toads Bufo fowleri, and B. 
americanus were positive in white light, in the eyeless as well as in 
the normal condition; but, when they were tested in colored lights 
obtained by passing white light through colored solutions (p. 187), 
the reactions did not agree with those of normal frogs. When Rana 
palustris, in the normal condition (p. 189), was tested, blue light was 
found to be most effective in the production of positive responses, 
and red the least, with a gradual decrease in effectiveness between 
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