The Republican. [volume] (Oakland, Md.) 1877-current, 1890-05-31
A STUDY OF SENSATION.
AS Observed in the Lowest Forms
of Life.
How the Words ''Irritability" and ''Dis.
elimination" are Used to Bridge
Perplcxing Problems-Sensitive
Plants and Sponges.

If the green scum which accumulates
on roofing tiles and other exposed sur
faces be washed off and the water exam
ined under a microscope, it will be
found to teen with an organism either
entirely green or partly green and red.
This organism is known as the PrOt0c0c-
Gus Cthat is, first berry'O, and is one of
the lowest and simplest forms of true
plant-life. Its color indicates the pres
ence of chlorophyll, and consequently
the power of assimilating carbon from
the carbonic acid of the atmosphere
one of the marks Of a true plant Tho
chief end of the protococcus' life seems
to be to multiply, and this it accom-
plishes by dividing itself in pieces, each
piece forming new individual, which
In turn divides up, to form further
crop This method of reproduction is
common in the lowest forms of life, and
Is known as tiSsion, or splitting off. Lit
tie can be said about the inner life of
the protococcus; but from the fact that
the rapidity with which it multiplies is
affected by conditions external to itself,
it may be assumed that these conditions
in some way or other influence the vi
tality of the organism. This is perhaps
as much as can be said about sensation
in this lowly form of life; yet, while oc-
cupying a position very near the bottom
of the scale, the protococcus is not
without touch of romance. When
Arctic or Alpine travellers meet with
what they describe as red SHOWS, y it is
nothing moro nor less than the humble
but hardy protococcus tlourishing and
multiplying on the surface of the virgin
snow.
From one of the lowest of plants to
one of the lowest of animals is but a
short step and in some roadside ditch
or stagnant pool the 1mTbG finds a
home. The amnba is q mere speck of
jelly-loolling matter, possessing neither
structure nor organization. When this
simple matter is found in connection
with life, whether plant or animal, it IS
known as protoplasm; and protoplasm is
found at the beginning Of every form of
life, from the lowest plant to man him
self The amnba is ever changing it's
form (hcnce its name, which means
changer, and by pushing out finger
looking processes is able to move about
through the water. 1t seems also TO be
able IN some mysterious way to avoid
collisions which might be disastrous to
itself. When smaller organism comes
against the surface of the am9ba, a
contraction of the protoplasm takes
place, and an opening is made whore
the organism struck. Soon the luckless
wandercr is engulfed in the body of the
amRba and diges ted, so far as it will
digest, to form new protoplasm. Whom
the amuba, whose sense of hunger
never seems to fail, is waxing too fat
for its own comfort, tho protruding
fingers now and again drop off, and set
ting up on their own account as new
individuals, repeat the life of the par
ent. From the foregoing, it will be
seen that the amoeba is to a consider
able extent alive to what is going on
around it, and were its structure I'M
known, it might be affirmed that it
possessed the special senses of at least
touch and sight. But it does not possess
tho ghost of any senSe-organ. The con-
traction of the am9ba when struck by
another body resembles tho contraction
of muscular tissue under sudden irrita-
ton: but again, the am9ba has no
tissue of any kind. The parting with
pieces of itself would seem to be de-
Lucrative act. Yet the ameba has no
nerve or brain center where such DELHI
Grafton could be carried on.
Notwithstanding all these negations,
the fact still remains that the am0ba is
sensitive to outside conditions, and
some term or terms are required to de-
scribe this particular form Of sensitive
ness. Biologists appear to be agreed
that the contractile motion of the
amnba is sufficiently described under
the term 'irritaDility" or ''eXcita bility,"
and the other movements are covered
by the term discrimination. These
terms may to certain extent be salts
factory; but their value will be better
understood when actions similar to that
of the am9ba arc considered in one or
two of the higher classes of plants.
When a tiny insect alights on certain
parts of such plants as the sundew or
Venus fly-trap, a co1tractile movement
is at once set up, which usually costs
the luckless insect it's life. If irritated
few times by the point of a pencil or
sharp instrument, the plants seem to
discover tho fraud, and cease to act.
Drops of rain falling with presumably
greater force than that exerted by the
alighting of an insect produce no effect.
The sundew, moreover, is so sensitive
to tho presence of ammonia that it will
indicate its presence IN a solution so
dilute as to be beyond the recognition
of the ordinary laboratory tests.
From the behavior of these plants it
might be surmised that they possess in
some measure the special senses of
touch and taste, and in the case of the
sundew, also smell, to say nothing Of
an intelligence to make use of these
senses. But the anatomy of the sun
dew and Venus Ay-trap shows neither
nerve nor muscle, far less any special
organs of sense. AS with tho ameba,
biologists write down the whole pho
nomcna as due to ''irritability" and
discrimination" These terms, no
doubt, form very convenient bridge
for getting over such problems as the
movements of plants; but they evident
ly fall short of explaining the pho
nomcna.
The ampba being to all intents one
.celled animal, it is comparatively eaSy