34 FOOT-NOTES TO EVOLUTION. 
Within the brain of man, resting on the optic lobes, is a 
little roundish structure scarcely larger than a pea, 
known as the pineal “ gland” or “ conari- 
Tne eoneateye: um.” It has no evident purpose or 
function, and a philosopher a : 
once suggested that it might = 
be the seat of the soul. It 
is larger in the embryo, and 2 —— ee 
still larger in the brains of yg, r.—Pineal body in the liz- 
some of the lower vertebrates.  ard_(Hatteria) developed as 
: : , rudimentary eye; /, pineal 
Recent investigations have eye. After Spencer. 
shown that it is especially de- 
veloped in certain lizards, and that in them it ends ina 
more or less perfect eye, which is placed between the 
others in the centre of 
the forehead. These 
lizards have in fact 
three eyes, and the pi- 
neal body is the optic 
nerve of thethird. In 
the common horned 
toad the pearl - like 
scale above the pineal 
eye can be readily rec- 
ognised. The shrunk- 
en rudiment found in 
man is therefore what 
is left of an ancestral 
third eye, probably 
; ——* once characteristic of 
Fic, 2.—Pineal eye of the lizard b 
(Hatteria). After Spencer. vertebrates, but now 
displaced and de- 
stroyed by the increased development and greater per- 
fection of the outer pair. By the theory of descent the 
presence of the pineal body in man is a simple result 
