LAURENS: MONOCHROMATIC LIGHTS. 267 
TABLE 1. 
Reactions of toads to monochromatic light received through both eye and skin. 
Monochromatic Blue Green _ Yellow Red 
lights of equal 
intensity 420-480 uu 490-550 uy 570-620 uu 630-655 uy 
Directions of | + |—/2+|0} + |—! 4/0} + sag +/O; + |—/+/)/0 
if | 
fe | —. qe eFC Ee eee Oe Or > zOO''O??O Oman a> > —————--—CO Orhan OO COC 
-< | Number of Olea 
3 responses | 251 | 37 230 | 58 194 | 94 | 167 | 121 
ev | | 
3 Percent of exer | | 
responses | 87 | 13 80 | 20 67 33 | 58| 42 | 
The numbers under + indicate total numbers of reactions toward the light; 
under—, away from the light; under +, without reference to the light (indifferent) ; 
under O, no reaction within five minutes. 
By way of summarizing the results of the experiments with single 
monochromatic lights in which both the eye and skin acted as re- 
ceptors, it may be stated that all four colored lights used produced 
positive responses. Blue light was the most effective, and the other 
lights formed a decreasing series, corresponding roughly to their 
relative position in the spectrum, the red light being but slightly 
more effective than darkness. 
B. Reactions with the Eye as Receptor. 
It was natural to suppose that the reactions of toads with both the 
eye and skin acting as receptors, were dependent upon the eye, but 
it was conceivable that they might also depend in some measure upon 
the skin. The skin of many amphibians has been found to be very 
sensitive to white light. Parker (:03) showed this to be the case in 
the frog, Rana pipiens. He also reviewed the literature of the subject 
of the sensitiveness of the skin to stimulation by light, pointing out 
that similar results had been obtained by previous observers on 
Triton and Proteus, among amphibians, as well as on certain fish and 
other metazoans. Later (:05) he showed that the skin of Ammocoetes 
also possessed this sensitiveness to light, the tail being the most 
