ANIMAL SENSE PERCEPTIONS. 335 



therefore believe to exist. The Baboon could only represent the 

 phenomenon under the colours as they appeared to him, but if 

 such colours have a different appearance to me, both picture and 

 subject would still be identical, and prove absolutely nothing. 

 To take an extreme illustration. Suppose what is white to me 

 is black to my Baboon, and vice versa. If my animal faithfully 

 paints a white flower as black, as it sees it, the picture must still 

 show a white flower to me, because of our different sense appre- 

 ciations.* 



Leeches (Clepsine) afford a good instance of the variety in 

 sense perception. Prof. Whitman has paid much attention to 

 these animals, and writes : — *' Pass the hand over a dish in which 

 a number of Clepsines are resting quietly on the bottom, and at a 

 distance of a few inches above the animals, taking care not to 

 make the least jar or other disturbance. If the animals are 

 quite hungry, the slight shadow of the hand, imperceptible 

 though it be to our eyes, will be instantly recognized by them, 

 and a lively scene will follow, every Leech rising up, supported 

 on its posterior sucker, and swinging at full length back and 

 forth, from side to side, round and round, as if intensely eager to 

 reach something. Put a Turtle in the dish, and see what a 

 scramble there will be for a bloody feast. The shadow of the 

 hand was to these creatures like the shadow of a Turtle swim- 

 ming or floating over them in their natural haunts, and hence 

 their quick and characteristic response. A piece of board 

 floating over them would have the same effect. Although so 

 sensitive to a small difference in light, the Clepsine eyes can give 



'■' This may also be illustrated by the perceptions of persons suffering 

 from red-blindness. As Bernstein observes : — " The world must appear to 

 them quite differently coloured to what it appears to us. What looks to us 

 white, must to them have a greenish-blue appearance, because red is wanting 

 in it ; and yet they call it white, because it comprehends the whole of their 

 series of colours " (' The Five Senses of Man,' p. 115). Even our own sense 

 perceptions may be only temporary. We call a body white when it reflects 

 all the colours of the spectrum in the proportions in which they are contained 

 in sunlight. As Bernstein further remarks : — " It is very probable that the 

 kind of light which we call ' white ' would not remain the same if the pro- 

 portion of the colours in the light of the sun were to alter ; and since we 

 suppose even the sun and its light may not remain the same for ever, it is 

 quite possible that our descendants may have a perfectly different idea of 

 white to what we now have " {ibid, p. 162). 



