By Dr. OTTO ZACHARIAS.
It is generally correct to say that air, light and moisture form the
chief conditions necessary for the development of organic plant or
animal life. One of these conditions, however, namely light, is not of
equal importance with the two others. For modern investigation and the
discoveries made during the progress of natural sciences have shown
that in the depths of the ocean, where an everlasting darkness reigns,
and where the temperature is extremely low, nevertheless a great
abundance of animal life is to be found, and that there exist living
beings, not only of the lowest organization, but even fishes and
crustaceans of very complicated structure, all of which thrive without
enjoying the slightest ray of light.
A similar example of animal life in the absence of light is to be
found in the fauna of caves and grottoes. This was first made known to
the world by Austrian and American naturalists. The well known
Adelsberg grotto in Krain, and the gigantic Mammoth Cave in Kentucky,
furnished much interesting material for a detailed study of the
biological conditions of subterraneous animal life. It was gradually
discovered that in those dark places there existed not only insects,
spiders, crustaceans, centipedes, worms, and snails, but also a kind
of salamander and fishes. But what gave special interest to these
discoveries was the fact, ascertained by careful study, that not all
of these beings were gifted with normally developed organs of vision,
but that in some these organs had undergone a retrograde development,
while others were entirely blind.
Among the latter, the blind fish of the Mammoth Cave (_Amblyopsis
spelacus_) is especially remarkable, because in this being the
retrograde development of the organ of vision is accompanied by the
production of certain ridges of skin on the body which are endowed
with an extreme sensitiveness of touch, and which, according to a work
lately published by Professor Von Leydig, are composed of little warts
in which the nerve fibers end. Nature, therefore, has in this case
compensated the amblyopsis for his loss of sight by endowing him with
a highly developed organ of feeling.
A similar phenomenon is to be observed in the blind crab (_Cambaras
pellucidus_), which is also found in the Mammoth Cave, for in this
being, according to Professor Von Leydig, the little warts on the
interior feelers, which constitute the organ of smell, have also
received an abnormal development.
[Illustration: FIG. 1.--THE SEMI-BLIND SALAMANDER (PROTEUS ANGUINEUS)
OF THE ADELSBERG GROTTO, IN AUSTRIA.]
Better known than the blind fish and the blind crab of Kentucky is the
_Proteus anguineus_, a kind of salamander, of a pale rose color,
endowed with gills and found in the Adelsberg grotto in Austria. (Fig.
1.)
This amphibium has an eye which lies very deep in the body and is
almost overgrown by the skin. But this eye is by no means as developed
as the organ of vision, for instance, of the water salamander (the
triton) or of the so-called axolotl, for it exists only in a kind of
embryonic development, and contains neither a vitreous humor nor a
lens for the refraction of the rays of light. As, however, the nerve
of vision exists, it is possible that this salamander may be able to
discern in some manner between light and darkness.
The thinking student, when discovering such imperfect organs of sight,
will naturally ask how the eye of this salamander, which is so useless
for its real purpose, has come into existence, and he will weigh the
comparative value of the two following explanations. It may be assumed
that there existed once in the Adelsberg grotto a salamander which was
absolutely blind, and in which, in consequence of an innate power of
evolution, an organ of vision of the lowest kind was gradually formed.
But to this assumption the objection may be raised at once, why nature
should have produced an organ of vision in an animal living in a
grotto, where such an organ is absolutely useless, and where such a
development would be quite as paradoxical and improbable as, for
instance, the development of fins instead of legs in an animal living
on dry land.
On the other hand, one may suppose, and this is the more probable
explanation, that the _Proteus anguineus_ is descended from a kind of
salamander, which possessed perfectly developed eyes in the beginning,
and that the imperfect organ of vision in the descendants living in
the dark caves is the result of gradual degeneration. This is the more
likely to be true as in many other cases, also, we find that organs
which become useless and cannot be employed have gradually
degenerated.
Our common mole furnishes an example. Its eyes also have become small
and are deeply hidden in the muscles, although they are by no means as
much degenerated as in the _Proteus anguineus_, and are still
possessed of a lens and a retina. Their nerve of vision, however, has
become very imperfect, and its connection with the brain is
interrupted, so that the animal for this reason can have no perception
of light. Notwithstanding the above, however, it is doubtful whether
the degeneration and gradual disappearance of the visual organ is in
all cases the result of their being no longer employed, since there
exists in dark caves a kind of beetle, the _Machaerites_, in which
species the female only is blind, while the male has a well developed
organ of sight. In this case it cannot be maintained that the absence
of light has been the cause of the blindness of the female beetle,
because it would have acted equally upon the male. Nevertheless, no
other explanation can be found for the blindness. The problem,
therefore, is hitherto unsolved.
Of late the investigations of naturalists have been extended to the
animal life existing not only in grottoes and caves, but also in mines
and pits created by the action of man, and this has led to many
interesting discoveries and remarkable results. A naturalist who has
especially enlarged our knowledge with regard to the subterraneous
fauna and flora is Dr. Robert Schneider, of Berlin, who made his
studies in the coal mines near Waldenburg and Altwasser, in Silesia,
the salt mines of Stassfurt and the metal mines of Klausthal, in the
Upper Harz Mountains.
[Illustration: FIG. 2.--GROUP OF PYRENOMYCETES, A SPECIES OF FUNGI
FREQUENT IN THE WATERS OF MINES.
a. Found in the mines of Waldenburg; b. In the brown-coal pits
near Westeregeln; c. In the Dorothea pit at Klausthal.]
[Illustration: FIG. 3.
a. Rhizomorpha canalicularis of Hoffmann, b. Club fungus
(Clavaria deflexa) of Hoffmann, found in the mines at Klausthal.]
As regards the subterraneous flora, Dr. Schneider's investigations
resulted in showing that the plants which thrive in the dark regions
under ground are those which possess no chlorophyl and are sensitive
to light. Those which vegetate most luxuriantly there are the _fungi_,
and among them especially the _pyrenomycetes_, which are frequent in
the waters of mines. Their general aspect is shown in a 480 times
magnified form in Fig. 2. They resemble fine threads of delicate
structure, and where found are always discovered in great abundance.
Most conspicuous by their shape and considerable size are the
_rhizomorphæ_, Fig. 3a, and they are remarkable, not only for their
brilliant phosphorescence, but also for the peculiar fact that they
are only found in places where light does not enter. These
_rhizomorphæ_, though this is not easily recognizable from their
external appearance, also belong to the fungi and are often seen in
strings of the length of over a meter and the thickness of a quill,
spreading out in peculiar branches and hanging down from moist beams
in dark places. Sometimes they grow like seaweed in the water of the
mines, and in this case they give much embarrassment to the miners,
because they are apt to obstruct the channels constructed for leading
off the superfluous water. In the mines of Freiberg these
_rhizomorphæ_ exist in great abundance, and Humboldt already mentions
specimens of the length of 4½ feet. Miners in Germany call them
_zwirn_ (thread). The student of natural sciences, when encountering
these peculiar forms of vegetation, will ask in how far they are the
product of their surrounding circumstances (i.e., of the absence of
light or the presence of moisture), and in order to find a reply to
this question experiments have been made to grow these _rhizomorphæ_
under different conditions of existence. These experiments have shown
that from several species of _rhizomorphæ_ other ordinary fungi can be
developed, and that the subterraneous specimens therefore may be
considered a degeneration and variation of the fungi found above the
surface of the ground.
[Illustration: FIG. 4.
a. Agaricus myurus of Hoffmann, a subterranean fungus. b.
Himantia villosa, a species of rhizomorpha found in the Upper
Harz Mountains.]
In Fig. 4b the _Himantia villosa_ is represented, a rhizomorpha found
in the mines of the Upper Harz Mountains, thus showing another form of
this vegetable growth. Though it is difficult, as above stated, to
recognize by their shape the rhizormorphæ as fungi, the origin of the
peculiar _Agaricus myurus_ of Hoffmann (Fig. 4a) will be much easier
discovered, though a retrograde development and degeneration has taken
place also in this fungus. It still shows, however, the elements of a
regular toadstool, only that the stem is much elongated and looks like
a thread or a tube, while the cap is small, and this explains how, by
gradual degeneration, the cap may disappear entirely, leaving nothing
but a stem, as, for instance, in the case of the _Clavaria deflexa_,
the club fungus, shown in Fig. 3b.
In connection with the above it may be well to speak of the fungi
constituting the mould which often covers the roof and the doors in
the brown-coal mines of Halle, specimens of which are shown in Fig. 5.
[Illustration: FIG. 5.--FORMS OF MOULD FUNGI FOUND IN THE BROWN-COAL
MINES NEAR HALLE A. S.]
We now come to the animal life in mines and pits. This is mostly
represented, of course, by lower organisms, as infusoria and worms.
Thus, in the slime on the bottom of the waters in mines, several
species of _amoebæ_ are found, which consist of microscopically
small animated bodies, continually floating about, nourishing
themselves by absorbing organic matter, possessing sensation,
propagating, etc., and, in fact, having actually the qualities of real
animal nature. Further, we find in those subterraneous waters a
species of the sun infusorium (_Actinophrys_), which is especially
frequent in the mines of Klausthal. Fig. 6 shows one of these
peculiar little beings. Also the _Stylonychia_ (Fig. 7) is a
characteristic inhabitant of those places, and always present there.
[Illustration: FIG. 6.--THE SUN INFUSORIUM (ACTINOPHRYS).]
[Illustration: FIG. 7.--THE RAPACIOUS INFUSORIUM (STYLONYCHIA).]
It moves with great rapidity in the water by means of the numerous
hairs covering its body, can turn quickly in any direction, and thus
is enabled to catch suddenly the little beings on which it lives and
which it hunts; for which reason the stylonychia is called the
"rapacious infusorium."
The above are organisms which can be seen only through the microscope,
but the fauna of mines contains also larger organisms, though they are
not found as regularly and are not as characteristic for those places
as the forms mentioned hitherto. Among these organisms there are
several species of worms, spiders, gnats, and, above all, crustaceans
of the lower class. The most interesting of the latter is perhaps a
variety of the sand flea (Fig. 8--_Gammarus pulex_). The crustacean
found in the pits of mines, which is related to the sand flea, shows,
according to Dr. R. Schneider, a slight degeneration of the organ of
sight, which has taken place in consequence of its adaptation to the
dark places, in which this variety of the _Gammarus pulex_ is found,
which can make no use of eyes, while the sand flea possesses them
fully developed. Otherwise, however, the two varieties are almost
absolutely alike, differing only in some details.
[Illustration: FIG. 8.--THE SAND FLEA (GAMMARUS PULEX).]
From the above the reader will see that "breathing in the rosy light,"
as Schiller calls it, is not an absolutely necessary condition for the
existence of organic beings, but that life exists everywhere, where
there is air and moisture, and a temperature which is not always below
freezing point, though even eternal frost does not exclude life
entirely, as is proved by the existence of the glacier flea, showing
that even in the icy coverings of the Alps life still is possible.
Mephistopheles may therefore well say:
"From water, earth, and air unfolding,
A thousand germs break forth and grow
In dry and wet, and warm and chilly;
And had I not the Flame reserved, why really,
There's nothing special of my own to show!"
--_Leipziger Illustrirte Zeitung._
* * * * *
[NATURE.]