Burlington weekly free press. [volume] (Burlington, Vt.) 1866-1928, 1909-12-30
EVOLUTION OF THE EYE.
Question whether II OrininntcS in III,
skin or In the lirains

Question whether 1t Oripinn,cs in the
Skin or In the brains.
In the concluding lecture in his Lowell
Institute course on tho sense organs W
man and their evolution. Prof George
Howard Parker considered Tho evolution
Of the eye.
The first consideration was that of the
pineal gland, which is what Is left Of
structure precisely like an eve The gland
has long been known to the older natural
lists. and in humans was supposed to he
the seat Of the soul There is only one
such organ" they argued ut IS single.
and there is only one soul. but" said the
speaker. such reasoning does not count
now with Investigators Some If the
animals that possess the pineal eye were
noted the lanprey eel and the saaman-
der In the latter there is transparent
scale on the top of the head. beneath
which is an organ that in its structure
is on the same lines and principles as the
usual eye. 1t has its nerves that run
away 10 The pineal gland In the eel it il
very small In humans the pineal gland
has No eye and is situated under the
brain.
The second point for elucida ton was
4
brain. The main features are, in the first
place. that the development OF brain. AZ
illustrated in successive stages of the
chicken embryo. is from a thckening
along the back Of the very young and al
most formless chick which hollows in
brings It's edges together. making a tube
and then sinks into the substance of the
flesh. This is the vertebral nerve col
umn Of the higher orders. What Mr.. Bal.
four argued was that the eyes formed
themselves first the skin and this
folded in We're carried with It's surface
into the brain and developing from thii
found their places near the surface as We
know them.
Many interesting matters were COM
mented on in passing. one of these IS
that the lens of the eye is a development
OF the skin II is in no way connected
with the eye as it comes from the brain
yet a lens forms at Just the right dis.
lance relation to the eve-cup, and later
Joins ii. making a single complex organ
There is something that defines the ioc1'
ton Of the lens that is not yet explain.
ed. This is shown by curious ex1eri uents
that have been made with tadpole EN-.
bryos. These are SO young that they are
not sentient individuals, merely coisc-
tons of cells beginning to take definite
shape. 1t is possible to cut these and tc
Joint them together in odd WAYS such as
the tail of one to the head Of another
The parts fuse together and curious e<-
perimental animals have been grown m
such small animals the rudimentary eye.
cup has been taken out and grated some
whore else on the body. on the tail, for
example, and almost always there ha.
developed a lens in proper relation to tie
misplaced eye.
: In considering the question whether Il
would be possible for an eye to travel
from the skin into the brain the speaker
noted the travelling of eyes of founders.
w en- young the founder is like any
other fish and swims like other fishes.
But later in life it becomes fitted for A
bottom fish and swims with what was ona
vertical side now parallel to the bottom.
lie becomes a fat FISH and in this stag
hes both eyes on the top side. This man
he the right side or the left side Of the
FISH hut the eyes are on the same side.
To get together. one of TIE eves travels
along the surface ard over what was
originally the tor Of the head The pro-
cess 80 change takes only few DAYS.
but it is a critical time Tor the youn,
, sea-squirts likewise have an eye that
travels; In them 1t goes through the
head. II makes little difference however.
for the whole substance of the animal ~
transparent and the light can reach the
eye just as well when it is in the center
of the head as II ii We're ON the surface.
The single eye-spot of these creatures led
naturally TO the AmphioXus. lowest of
the backbone creatures and lacking sumo
OF the senses. 1t has no sense OF equi-
brium and no hearing, but along the on
tire length Of the creature there il line
of spots, which experiment. shows In no
sensitive to light Here are visual cells
in consdera hlc quantity grouped some
what irreguarly along line parallel -
the backbone. These Professor Parker
notes to be direction eyes.
Direction eyes are fixed organs that
catch the light from a given direction
only. and such organs are we'll known
among certain orders of animals They
show all the Characteristics OF regular
eyes, excepting motion
In conclusions the speaker reviewed the
story of the senses Nery briefly in chrome
logical order. Touch was the earliest Of
all, The AmphioNuS has that and some
smell so that both OF these are very
primitive senses. The next group above
this lowest Of Nertehrates is that in which
the lamprey eel finds itself, and This adds
taste and sight. Hearing is the most re-
cent OF all senses and the most perfect