1883.] 
731 
Eyeless and Blind Animals • 
possessing normal vision, distinguishes between red and 
blue, giving the former the preference. When both colours 
were approximately equal in intensity there were found in 
the red 474, and in the blue 1 76, the quotient therefore 
being = 2*7. 
Three further series of experiments were made upon blind 
salamanders to test their behaviour in white light respedt- 
ively containing and deprived of the ultra-violet rays. In 
light which was relatively bright, but free from the ultra- 
violet rays, there were found 313 ; in unaltered, but rela- 
tively dim light, there were 149, the quotient being = 2*1. 
A comparison of the two colours green and blue gave, with 
normal specimens, in the green 299, in the blue 98, or a 
quotient = 3*1. With blind specimens there were found, in 
the green 131, in the blue 79, the quotient being = i*6. 
For red-green, with blind animals, the quotient was = 1*8, 
and for red-yellow = 1*4. 
It is therefore proved, in the most decided manner, that 
blind animals are sensitive to quantitative and qualitative 
differences of light. The signification of this fadt may be 
manifold. The first possibility, that effects of heat are con- 
cerned, is excluded by the experiment in which the salaman- 
ders were found thermophobic, so that they should shun 
the red light and seek the blue, whilst the contrary is the 
case. 
Of the two other possibilities, that differences of light are 
recognised either by their chemical adtion or by a diredt 
influence upon the sensation of the skin, Prof. Graber decides 
in favour of the latter, and for the following reason : — Let 
us suppose the entire sensibility of animals for light were 
what the theory of Descent demands or seems to demand, 
— i.e., that the eyes are, indeed, the main organs for the 
perception of light, but that the skin still takes a certain 
share therein, since prior to the differentiation of the eyes it 
was the sole organ for light. Let us then ask what would 
be, on this supposition, the reactions of normal and of blind 
salamanders. Two results may naturally be expedted ; — 
First, in the blind, and therefore exclusively dermatoptic, 
animals there would.be the same preference for certain kinds 
of light as in the ophthalmoptic normal individuals. 
Secondly, the readtions of the former must be decidedly 
slighter than those of the latter. According to the experi- 
ments above described both of these results follow. 
It will at once strike the reader that the experiments of 
Professor Graber have been confined to animals which are 
lucifugous, light-shunning. With animals which are diurnal, 
3B2 
