APRIL.
The beautiful Floscule--Mode of seeking for Tubicolor
Rotifers--Mode of illuminating the Floscule--Difficulty of
seeing the transparent tube--Protrusion of long
hairs--Lobes--Gizzard--Hairy lobes of Floscule not rotatory
organs--Glass troughs--Their construction and use--Movement of
globules in lobes of Floscule--Chaetonotus larus--Its mode of
swimming--Coleps hirtus--Devourer of dead Entomostraca--Dead
Rotifer and Vibriones--Theories of fermentation and
putrefaction--Euplotes and Stylonichia--Fecundity of
Stylonichia.
Few living creatures deserve so well the appellation of "beautiful" as
the _Floscularia ornata_, or Beautiful Floscule, although to contemplate
a motionless and uncoloured portrait, one would imagine that it
exhibited no graces of either colour or form. Mr. Gosse has, however,
done it justice, and the drawing in his "Tenby" is executed with that
rare combination of scientific accuracy and artistic skill, for which
the productions of his pencil are renowned.
[Illustration: The Beautiful Floscule. A.--Partially protruded.
B.--Freely protruded, with three eggs. C.--Appearance of young.
D.--Floscule seventeen hours old. D'.--Jaws of Floscule, as figured by
Mr. Gosse.]
Probably the sketches in several works of authority representing the
long cilia as short bristles, are merely copies from old drawings, from
objects imperfectly seen under indifferent microscopes, and before
the refinements of illumination were understood. Be this as it may, any
reader will be fortunate if on an April, or any other morning, he or she
effects the capture of one of these exquisite objects, although the
first impression may not equal previous expectations, as the delicacy of
the organism is not disclosed by a mode of using the light which answers
well enough for the common infusoria.
When the Floscules, or other tubicolar Rotifers are specially sought
for, the best way is to proceed to a pond where slender-leaved
water-plants grow, and to examine a few branches at a time in a phial of
water with a pocket-lens. They are all large enough to be discerned, if
present, in this manner, and as soon as one is found, others may be
expected, either in the same or in adjacent parts of the pond, for they
are gregarious in their habits. With many, however, the first finding of
a Floscule will be an accident, as was the case last April, when a small
piece of myriophyllum was placed in the live-box, and looked over to see
what it might contain. The first glimpse revealed an egg-shaped object,
of a brownish tint, stretching itself upon a stalk, and showing some
symptoms of hairs or cilia at its head. This was enough to indicate the
nature of the creature, and to show the necessity for a careful
management of the light, which being adjusted obliquely, gave quite a
new character to the scene. The dirty brown hue disappeared, and was
replaced by brilliant colours; while the hairs, instead of appearing few
and short, were found to be extremely numerous, very long, and
glistening like delicate threads of spun glass.
Knowing that the Floscules live in transparent gelatinous tubes, such an
object was carefully looked for, but in this instance, as is not
uncommon, it was perfectly free from extraneous matter, and possessed
nearly the same refractive power as the water, so that displaying it to
advantage required some little trouble in the way of careful focusing,
and many experiments as to the best angle at which the mirror should be
turned to direct the light. When all was accomplished, it was seen that
the Floscule had her abode in a clear transparent cylinder, like a thin
confectioner's jar, which she did not touch except at the bottom, to
which her foot was attached. Lying aside her in the bottle were three
large eggs, and the slightest shock given to the table, induced her to
draw back in evident alarm. Immediately afterwards she slowly protruded
a dense bunch of the fine long hairs, which quivered in the light, and
shone with a delicate bluish-green lustre, here and there varied by
opaline tints.
The hairs were thrust out in a mass, somewhat after the mode in which
the old-fashioned telescope hearth-brooms were made to put forth their
bristles. As soon as they were completely everted, together with the
upper portion of the Floscule, six lobes gradually separated, causing
the hairs to fall on all sides in a graceful shower, and when the
process was complete, they remained perfectly motionless, in six hollow
fan-shaped tufts, one being attached to each lobe. Some internal ciliary
action, quite distinct from the hairs, and which has never been
precisely understood, caused gentle currents to flow towards the mouth
in the middle of the lobes, and from the motion of the gizzard,
imperfectly seen through the integument, and from the rapid filling of
the stomach with particles of all hues, it was plain that captivity had
not destroyed the Floscule's appetite, and that the drop of water in the
live-box contained a good supply of food.
Sometimes the particles swallowed were too small to be discerned,
although their aggregate effect was visible; but often a monad or larger
object was ingulfed, but without any ciliary action being visible to
account for the journey they were evidently compelled to perform. The
long hairs took no part whatever in the foraging process, and as they do
not either provide victuals or minister to locomotion, they are clearly
not, as was supposed by early observers, representatives of the
"wheels," which the ordinary Rotifers present. Neither can the
cylindrical jar or bottle be justly deemed to occupy the position of the
lorica, or carapace which we have before described. The general
structure of the creature and the nature of its gizzard distinctly
marked it out as a member of the family we call "Rotifers," but the
absence of anything like "wheels" proves that those organs are not
essential characteristics of this class.
Noticeable currents are not always produced when the mouth of this
Floscule is fully expanded. On one occasion, one having five lobes was
discovered standing at such an angle in a glass trough that the aperture
could be looked down into. The position rendered it impossible to use a
higher power than about two hundred linear, but with this, and the
employment of carmine, nothing like a vortex was seen during a whole
evening, although a less power was sufficient to show the ciliary
whirlpools made by small specimens of _Epistylis_ and _Vaginicola_,
which were in the small vessel. The density of the integument was
unfavorable to viewing the action of the gizzard, but it could be
indistinctly perceived. The contractions and subsequent expansions of
the cup, formed by the upper part of the creature, may be one way in
which its food is drawn in, but there is no doubt it can produce
currents when it thinks proper. Sometimes animalcules in the vicinity of
Floscules whirl about as if under the influence of such currents. Some
may be seen to enter the space between the lobes, swim about inside, and
then get out again, while every now and then one will be sucked in too
far for retreat.
Above the gizzard in the Horned Floscule,[10] I have seen an appearance
as if a membrane or curtain was waving to and fro, while another was
kept in a fixed perpendicular position. Mr. Gosse, speaking of this
genus, observes "that the whole of the upper part of the body is lined
with a sensitive, contractile, partially opaque membrane, which a little
below the disk recedes from the walls of the body, and forms a
diaphragm, with a highly contractile and versatile central orifice. At
some distance lower down another diaphragm occurs, and the ample chamber
thus enclosed forms a kind of _crop_, or receptacle for the captured
prey."
[10] The Horned Floscules (_F. cornuta_) which I have found, and which
bred in a glass jar, were not so large as those described by Mr. Dobie,
as quoted in 'Pritchard's Infusoria.' Mr. Dobie's specimens were 1--40"
when extended; mine about half that size, five-lobed, and with a long
slender proboscis, standing in a wavy line outside one lobe. Mr. Dobie
also describes an _F. campanulata_, with five flattened lobes. The
'Micrographic Dictionary' pronounces these two species "doubtfully
distinct." I have three or four times met with a variety of _F. ornata_,
in which one lobe was much enlarged and flattened, but they had no
proboscis. In what I take for _F. cornuta_, the horn or proboscis has
sometimes been a conspicuous object, and at others so fine and
transparent as to be only visible in certain lights.
"From the ventral side of the ample crop that precedes the stomach,
there springs in _F. ornata_ a perpendicular membrane or veil, partly
extending across the cavity. This is free, except at the vertical edge,
by which it is attached to the side of the chamber, and being ample and
of great delicacy, it continually floats and waves from side to side. At
the bottom of this _veil_, but on the dorsal side, are placed the jaws,
consisting of a pair of curved, unjointed, but free _mallei_, with a
membranous process beneath each."
The Beautiful Floscule could always be made to repeat the process of
retreating into her den, and coming out again to spread her elegant
plumes before our eyes, by giving the table a smart knock, and her
colours and structure were well exhibited by the dark-ground
illumination, which has been explained in a previous page.
An object like this should be watched at intervals for hours and even
days, especially if the eggs are nearly ready to give up their infantile
contents. This was the case with the specimen described, and after a few
hours a young Floscule escaped, looking very much like a clumsy little
grub. After a few awkward wriggles the new-born baby became more quiet,
and on looking at it again at the expiration of seventeen hours, it had
developed into the shape of a miniature plum-pudding, with five or six
tiny lobes expanding their tufts of slender hair. Unfortunately its
further proceedings were not seen, or it would have been interesting to
note the growth of the foot, and the formation of the gelatinous tube,
which is probably thrown off in rings.
To view the details of the structure of a Floscule, it must be placed in
a live-box or compressorium, and if specimens are scarce, they should
not be allowed to remain in the limited quantity of water those
contrivances hold, after the observations are concluded, but should be
carefully removed, and placed in a little vial, such as homoeopathists
use for their medicine. By such means an individual may be kept alive
for many days. It is also interesting to place a little branch of the
plant occupied by Floscules or similar creatures, in a glass trough,
where they may be made quite at home, and their proceedings agreeably
watched by a one-inch or two-thirds power. These troughs,[11] which can
be obtained of the optician, should be of plate glass, about three
inches long, nearly the same height, and about half an inch wide. If
narrower, or much taller, they will not stand, which is a great
inconvenience. The pieces of glass are stuck together with marine glue,
and a very simple contrivance enables the plants or other objects to be
pressed near the front, and thus brought into better view. A strip of
glass, rather narrower than the width of the trough, is dropped into it,
and allowed to fall to the bottom. Then a piece of glass rather shorter
than the trough, and rather higher than its front side, is placed so as
to slope from the front of the bottom towards the back at the top. The
piece of glass first dropped in keeps it in the right position, and the
trough is thus made into a V-shaped vessel, wide at the top and
gradually narrowing. Any object then placed in it will fall till it fits
some part of the V, where it will remain for observation. A small wedge
of cork enables the moveable piece of glass to be thrown forwards, until
it assumes any angle, or is brought parallel to the front of the trough.
[11] The shallow cells with thin sliding covers devised by Mr. Curteis
(of Baker's), are still more convenient when no pressure is required,
and the objects are small. When not under the microscope they can be
kept full of water by immersion in a tumbler.
A power of five or six hundred diameters generally enables a movement of
small globules to be seen at the extremity of the lobes of the Floscule,
and the gizzard may be made plain by dissolving the rest of the creature
in a drop of solution of caustic potash. It also becomes more visible as
the supply of food falls short. Mr. Gosse describes the body as "lined
with a yellowish vascular membrane," and young specimens exhibit two red
eyes, which may or may not be found in adults. When these eyes of
Rotifers are not readily conspicuous, they must be sought for by opaque
illumination, or by the dark-ground method which, especially with the
parabola, is successful in bringing them out.
Naturalists, and possibly the specimens also, do not always agree in
the number of lobes assigned to the "Beautiful Floscule," and although
it is easy enough to count them in _some_ positions, the observer may
have to exercise a good deal of patience before he is certain whether
they are five or six. For a long evening only five could be discerned in
the specimen now described, but the next night six were apparent without
difficulty or doubt. The hairs also will not appear anything like their
true length or number, unless the object-glass is good, and great care
is taken not to obscure them by a blaze of ill-directed light.
[Illustration: Chaetonotus larus (swimming).]
After the Floscules had been sufficiently admired and put aside, for
observations to be repeated on future occasions, a Rotifer attracted
attention by his merry-andrew pranks, throwing himself in all directions
by means of two long and extremely mobile toes attached to his
tail-foot. Then came a creature swimming like an otter, thrusting his
head about on all sides, and looking much more intelligent than most of
his compeers of the pond. Looked at vertically, he was somewhat
slipper-shaped, the rounded heel forming his head, then narrowing to a
waist, and expanding towards the other end, which projected in a fork.
All round him were long cilia, which were conspicuous near the head, and
a fine line indicated the passage from his mouth to the stomach, which
seemed full of granular matter. Presently he took to crawling, or rather
running, over a thread of conferva, and then his back was elegantly
arched, and his cilia stood erect like the quills of a porcupine. This
was the _Chaetonotus larus_.
[Illustration: Chaetonotus larus (crawling).]
In Pritchard's "Infusoria," the views of those writers are followed who
rank this animal amongst the Rotifers, and place it in the family
_Icthidina_. To help out this theory, the cilia upon the ventral surface
are imagined to form a "band-like rotary organ;" but in truth they bear
no resemblance whatever to the so-called wheels of the ordinary
Rotifers, nor is there anything like the gizzard which true Rotifers
present. Ehrenberg treated it as a Rotifer, and Dujardin placed it among
the Infusoria, in a particular class, comprehending symmetrical
organisms. The 'Microscopic Dictionary' remarks that its "structure
requires further investigation,"[12] and while the learned decide all
the intricate questions of its zoological rank, the ordinary observer
will be pleased to watch its singular aspect and lively motions. Its
size, according to the 'Micrographic Dictionary,' varies from 1--710" to
1--220", and while its general proceeding may be watched with an inch or
two-thirds object-glass, and the second eye-piece, a power of five
hundred linear (obtained by a quarter or a fifth) is required to make
out the details of its structure. If placed in a live-box with threads
of conferva, and a little decayed vegetation, it may be observed to
group about among them, and shake them like a dog.
[12] See a valuable paper by Mr. Gosse, "History of the Hairy-backed
Animalcules," 'Intellectual Observer,' vol. v, p. 387, in which the
known species are described and reasons given for following Vogt and
ranging them with the Turbellarian worms.
We have said that water-fleas were among the inhabitants of a bottle
filled at the pond, and as they go the way of all flesh, it is common to
find some odd-looking animalcules ready to devour their mortal remains.
These are creatures shaped like beer-barrels, upon short legs, and which
swim with a tubby rolling gait. Looking at one of these little tubs
lengthwise, a number of lines are seen, as though the edge of each stave
projected a little above the general level, and transverse markings are
also apparent, which may be compared to hoops. This is the _Coleps
hirtus_, which differs from the usual type of Infusoria, by being
symmetrical, that is, divisible into two equal and similar halves. The
dimensions of this species vary from 1--570 to 1--430, and its colour
varies from white to brown. It has been observed to increase by
transverse self-division, and has two orifices, one at each end, for
receiving food and ejecting the remains. It often requires some little
trouble to get a good view of the cilia, which are arranged in
transverse and longitudinal rows. A power of one hundred and fifty
linear is convenient for viewing it in motion, but when quiet under
pressure, one of five or six hundred may be used with advantage.
[Illustration: Coleps hirtus.]
Among the rubbish at the bottom of the bottle, in which the coleps was
found, was a minute dead Rotifer, the flesh of which was fast
disappearing, but upon being examined with a power of nine hundred and
sixty diameters, it was observed to swarm with extremely minute
_vibriones_, the largest only appearing under that immense magnification
like chains of bluish-green globules, not bigger than the heads of
minikin pins, while the smallest were known by a worm-like wriggling,
although their structure could not be defined. These _vibriones_ are
probably members of the vegetable world, and they always appear when
animal matter undergoes putrefaction.
M. Pasteur has brought forward elaborate experiments to show that the
development of the yeast plant is an act correlative to alcoholic
fermentation, and in like manner the growth of _vibriones_ may stand in
correlation to putrefactive decomposition.
[Illustration: A, Euplotes (patella); B, side view of ditto; C,
stylonichia.]
Ehrenberg considered them animals, and fancied he detected in them a
plurality of stomachs; but the vegetable theory is the more probable, at
any rate of the species under our notice, which is often seen, though
not always so minute.
At this time two interesting animalcules were very plentiful--the
_Euplotes patella_, and _Stylonichia_, both remarkable as exhibiting an
advance in organization, which approximates them to the higher animals.
In addition to cilia they possess _styles_, which take the place of the
limbs of more elaborately-constructed creatures, and give a variety to
their means of locomotion. The _Euplotes_ is furnished with an oval
carapace covering the upper surface, which in different individuals, and
probably at different ages, exhibits slightly varied markings round its
margin, which in the specimen drawn above consisted of dots. They can
run, climb, or swim, and exemplify a singular habit which several of the
infusoria possess, that of moving for a little time in one direction,
and then suddenly, and without any apparent cause, reversing it. If the
reader is fond of learned appellations, he can call this _diastrophy_,
but we do not know that he will be any the wiser for it.
The Stylonichia are oval animalcules, surrounded by cilia, and having
moreover a collection of styles, both straight and curved, the latter
called _uncini_, or little hooks. They swim steadily on, and then dart
back, but not so far as they have advanced, and may be seen to keep up
this fidgety motion by the hour together. Pritchard tells us Ehrenberg
found that a single animalcule lived nine days; during the first
twenty-four hours it was developed by transverse self-division into
three animals; these in twenty-four hours formed two each in the same
manner, so that by self-division only (without ova), these animalcules
increased three or four-fold in twenty-four hours, and _may thus produce
a million_ from a single _animalcule in ten days_. Such are the amazing
powers of reproduction conferred upon these humble creatures, powers
which are fully employed when the surrounding circumstances are
favorable, and which, in the aggregate, change the condition of large
masses of matter, and bring within the circle of life millions upon
millions of particles every minute of the day.