On the Human Tail. 
416 
[July, 
that is concerned in the production of light and colour. 
Schultz believes that they both serve as elements of light, 
although the perception of light is the more immediate func- 
tion of the rods, while that of colour exclusively belongs to the 
cones; should these be congenitally absent or partly de- 
veloped it follows that the retina, and consequently the eye, 
must be insensible to certain portions of the speCtrum 
colour-blind. 
The physical and physiological bearings of the colour 
sense are too vast and important to be disposed of within a 
brief space ; I must therefore content myself by stating for 
the present that the range of human vision, like that of 
hearing, is subject to great variations in different indi- 
viduals, and that a great disproportion exists between the 
aCtual number of natural colours and the limited amount 
of sensory colours. The conclusion to be drawn from this 
observation is, that, “ normally every visual mechanism is 
physically and physiologically fitted to respond to but a 
small number of the great bulk of natural colour vibrations, 
and thus virtually proving that every such mechanism is 
truly colour-blind.” — (Oliver). It has been said of Chevreul 
that he was able to distinguish 14,420 tones of colour ; 
more recently, too, it has been found that the human eye is 
totally unable to receive all the vibrations of colour which 
must exist in the speCtrum. We know that it does not 
recognise the terminals of either end — the red and violet — 
and how many unrecognised natural colour differences 
actually exist between the red and the violet ends of the 
ordinary speCtrum. Through the want of power of perception 
in the retina it is quite impossible to say or imagine. — 
(Oliver). 
VIII. ON THE HUMAN TAIL. 
S NTI-EVOLUTIONIST writers, who, as a rule, are 
not biologists, still concern themselves about man’s 
supposed want of a tail. They have, indeed, been 
repeatedly told that the anthropoid apes are in this respeCt 
exactly on a level with man. If they were sincerely anxious 
for the the truth they might easily convince themselves that 
