6 Conservative ,
THE PROBLEM OF LIFE.
PAKT 11.
Judging by first impressions , nothing
could be more distinct than animals
and plants. Nobody , whether scien
tific or unscientific , could by any pos
sibility mistake an oak tree for an
elephant. To the unscientific observer
the tree differs in having no power of
free movement , and apparently no
sensation , or consciousness ; in fact ,
only a portion of the attributes of
life. The scientific observer sees still
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more fundamental differences , in the
fact that the plant feeds on inorganic
ingredients , out of which it manu
factures living matter or protoplasm ;
while the animal can only provide
itself with protoplasm from that al
ready manufactured by the plant.
The ox , which lives on grass , could
not live on what the grass thrives on ,
viz : carbon , oxygen , hydrogen and
nitrogen. The contrast is so striking
that the vegetable world has been
called the producer , and the animal
world the consumer , of nature.
Again , the plant derives the material
framework of its structure
from the air , by breathing
in through its leaves the carbonic
dioxide present in the atmosphere ,
decomposing it , fixing the carbon in
its roots , stem and branches , and ex
haling the oxygen. The animal exact
ly reverses the process , inhaling the
oxygen of the air , combining it with
the carbon of its food , and exhaling
carbonic dioxide. Thus , a complete
polarity is established , as we see in
the aquarium , where plant and anim
al life balance each other and the
opposites live and thrive , where the
existence of either would be impos
sible without the other.
Sharp , however , as the contrast ap
pears to be in the more specialized
and developed specimens of the two
worlds , we have here another
instance of the unwisdom of
trusting to first impressions ,
and have to modify our concep
tions greatly , if we trace animal and
vegetable life to their simplest forms
and earliest origins. In the first
place , each individual animal or
vegetable begins its existence from a
simple piece of pure protoplasm.
This develops in the same way into a
nucleated cell , by whose repeated sub
division the raw material is pro
vided for both structures alike. The
chief difference at this early stage is
that the animal cells remain soft and
naked , while those of vegetables se
crete a comparatively solid cell-wall ,
which makes them less mobile and
plastic. This gives greater rigidity
to the frame and tissues of the plant ,
and prevents the development of the
finer organs of sensation and other
vital processes , which characterize the
animal. But this is a difference of
development "only , and the origina
tion of the future life from the speck
of protoplasm is the same in both
worlds.
If , instead of looking at the origin
of individuals , we trace back the var
ious forms of animal and vegetable
life from the more complex to the sim
pler forms , we find the distinction be
tween the two disappearing , until at
last we arrive almost at a vanishing
point where it is extremely difficult
to say definitely whether the organ
ism is an animal or a plant. For this
large family Professor Haeckel sug
gested the name' ' Protista , ' ' as coming
between the lowest animals called
' ' Protozoa , ' ' and the lowest plants ,
or "Protophyta ; " but it has not been
generally adopted for reasons which
are outside the scope of this article.
As development proceeds the dis
tinction between plants and animals
becomes more apparent , although even
here the simplest and earliest forms
often show signs of a common origin
by interchanging some of the funda
mental attributes of the two king
doms. Thus , the essential condition
of plant existence , is to live on inor
ganic food , which is manufactured
into protoplasm , by working up sim
ple combinations into others more
complicated. The diet of plants con
sists of water , carbonic dioxide , and
ammonia ; they take in carbonic di
oxide and give out oxygen , while ani
mals do , as I have already said , ex
actly the reverse. But the fungi live ,
like animals , upon organic food con
sisting of complicated combinations
of carbon , which they assimilate ;
and , like animals , they inhale oxygen
and give oiat carbonic dioxide.
Lichens.
Lichens afford a very curious in
stance of the association of vegetable
and animal functions in the same
plant. They are really formed of two
distinct organisms : a body which is
a low form of alga or sea-weed , and a
parasitic form of fungus , which lives
upon it. The former lias a plant life ,
living on inorganic matter and form
ing the green cells or chlorophyll ,
which are the essential property of
plants , enabling them under the ac
tion of the sun's rays to decompose
carbonic dioxide ; while the parasite
lives like an animal on the formed
protoplasm , of the parent stem , form
ing threads of colorless cells which
envelop and interlace the original
lichen , of which they constitute the
principal mass , as in a tree overgrown
with ivy.
Even in highly-developed plants
we find some curious instances of re
version toward animal life. Certain
plants such as the Dionaea or Venus'
Flytrap , finding it difficult to obtain
the requisite supply of nitrogenous
food in a fluid state from the arid or
marshy soil in which they grow , have
acquired a habit of supplying the de
ficiency by taking to an animal diet
and eating flies. Goujointed with
this is sensitiveness
a more highly-developed
tiveness and the power of what appears I
to be voluntary motion , and a faculty j
of secreting a sort of gastric juice in j
which the flies are digested. It is '
possible , of course , that this power of
disintegrating animal tissue may be
partially due to nicro-organisms in
this curious gastric juice. But it i
must be understood that the fundamental - '
mental property possessed by veget
able life of decomposing carbonic
dioxide and exhaling oxygen depends
on light stimulating a peculiar chem
ical action of the chlorophyll and in
the dark , leaves breathe like lungs
exhaling not oxygen but carbonic
dioxide.
Interdependence.
The records of geology , imperfect as
they are , show a combined progression
from the simple and neutral organisms
to higher and more differentiated
forms , both in the animal and veget
able world. These records are im
perfect because the soft bodies of the
simpler and for the most part micro
scopic forms of protoplasm and cell
life are not capable of being preserved
in petrifications and it is only when
they happen to have secreted shells or
skeletons , that we have a chance of
identifying them. Still , we have a
sufficient number of remains in the
different geological strata to enable
us to trace development ; and it is cer
tain that there has been a complete
parallelism between the evolution of
animal and vegetable life from the
simplest to the most complex forms.
These facts point very strongly to a
process of evolution by which the
animal and vegetable worlds , starting
from a common origin in protoplasm ,
the lowest and simplest form of living
matter , have gradually advanced step
by step , until we have at last arrived
at the sharp antithesis of the ox and
the oak tree. It is clear , however ,
that this evolution has gone on under
what I must call the generalized law
of polarity , by which contrasts are
produced of apparently opposite and
antagonistic qualities , which , how
ever , are indispensable for each
other's existence. Thus , animals
could not exist without plants to work
up the crude inorganic materials into
the complex and mobile molecules of
protoplasm , which are alone suited
for assimilation by the more delicate
and complex organization of animal
life. Plants , on the other hand , could
not exist without a supply of the car
bonic dioxide , which is their princi
pal food , and which animals are con
tinually pouring into the air , from
the combustion of their carbonized
food in oxygen , which supplies them