OCTOBER.
Stentors and Stephanoceri--Description of Stentors--Mode of
viewing them--Their abundance--Social habits--Solitary Stentors
living in Gelatinous caves--Propagation by divers
modes--Cephalosiphon Limnias--A group of Vaginicolae--Changes of
shape--A bubble-blowing Vorticella.
October, the finest of our autumn months, is noted for usually granting
the inhabitants of our dripping climate about twenty pleasant sunshiny
days, and it is probably on this account somewhat of a favourite with
the infusorial world, although the cold of its nights and early mornings
thins their numbers, which reach a maximum in the summer heat. Even in
the dismal year 1860, October maintained its character, and afforded a
great many opportunities of animalcule hunting, during which a constant
supply of Stephanoceri were readily obtained, together with swarms of
_Stentors_, which are not exceeded in interest by any of the Ciliated
Protozoa. The Stentors were abundant on the same weed (_Anacharis_),
that formed the residence of the Stephanoceri, and might be seen in
large numbers hanging from it like green trumpets, visible to the
unassisted eye. In the 'Micrographic Dictionary' they are said to
belong to the Vorticella family, which has already given us several
beautiful objects, and possess a marvellous power of changing their
shape. It is, however, better to follow Stein, who separates them from
the Vorticellids and ranges them in his order Heterotricha, as they have
two distinct sets of cilia, small ones covering the body and the larger
ones round the mouth. Those before us are named after this property
_Stentor polymorphus_,[18] or Many-shaped Stentors, and owe their
exquisite tint to numberless green vesicles, or small cavities filled
with colouring matter like that of plants. This, however, is not
essential to the species which may often be found of other hues. In size
this Stentor varies from a hundred and twentieth to one twenty-fourth of
an inch. It is entirely covered with fine cilia, disposed in
longitudinal rows, and round the head is a spiral wreath of larger and
very conspicuous cilia leading to the mouth.
[18] See Frontispiece.
Having observed the abundance of these creatures, a few small branches
to which they were appended, were placed in the glass trough, and viewed
with powers of sixty and one hundred linear. Some had tumbled down as
shapeless lumps, others presented broad funnel-shaped bodies; while
others stretched themselves to great length like the long, narrow
post-horns which still wake the echoes of a few old-fashioned towns. The
ciliary motion of the elegant wreath was active and rapid, causing quite
a stir among all the little particles, alive and dead; and when the
right sort of food came near the corkscrew entrance to the mouth, down
it went, and if conspicuous for colour, was subsequently seen apparently
embedded in little cavities, which Ehrenberg supposed were separate
stomachs, although that theory is now rejected. One advantage of viewing
these objects in a sufficient quantity of water, to leave them in
freedom, is that they frequently turn themselves, so that you can see
right down into them; and the drawing given in the frontispiece
represents such a view, which is the most favorable for the exhibition
of the mouth. To make out the details of their structure, to see the
nucleus and other organs, the flattening in the live-box is useful, and
it enables much higher powers to be employed.
[Illustration: A, B, C, D, Stentor polymorphus in different degrees of
expansion. A large specimen is one twenty-fourth of an inch long.]
After leaving the Anacharis in a glass jar for a few days, the Stentors
multiplied exceedingly; some clung to the sides of the vessel in
sociable communities, others hung from the surface of the water, and
crowds settled upon the stems, visibly changing their tint, as the
Stentor green was much bluer than that of the plant. Scores swam about
in all sorts of forms. Now they looked like cylindrical vessels with
expanding brims, now globular, now oddly distorted, until all semblance
of the original shape was lost. Many were found in shiny tubes, but
these were never so lively or green as the free swimmers, but mostly of
a dingy dirty hue.
These housekeepers were more timid and cautious than the roving tribe.
They came slowly out of their dens, drew back at the slightest alarm,
never took their tails from home, and only extended their full length
when certain not to be disturbed. Some authors have thought they only
take to private lodgings when they feel a little bit poorly, but others
dispute this opinion, and I do not think it is correct. I have found
these Stentors at all seasons, from January to the autumn, but they are
never so numerous, nor aggregated in numbers like the roving sort.
Whether they are old folks, who are tired of the world and its gaieties,
and devote the remainder of their lives to contemplation, or whether
they are bachelors disappointed in love, I am unable to say; but they
are very inferior in beauty to the "gay and glittering crowd."[19]
[19] Stein says the colourless variety of S. Polymorphus is sometimes
found with a tube, and the S. Roessellii very frequently so provided.
For some weeks my Stentors abounded, and then most of them suddenly
disappeared. They could not have "moved," but probably "went to smash"
by a process peculiar to infusoria, and which Dujardin politely
describes as "diffluence." This mode of making an exit from the stage of
life is more tragical than the ripping up so fashionable in Japan. The
integument bursts, and its contents disperse in minute particles, that
in their turn disappear, and scarcely leave a "wrack behind."
The Stentors obey the injunction to "increase and multiply" by
self-division, which Stein says is always oblique, and the nucleus,
which plays such an important part in infusoria, is band-like,
moniliform (bead-shape), or round. When an animalcule increases by
self-division, a portion of the nucleus goes with each part, and it is
probably the organ which stimulates the change. It is also concerned in
other modes of propagation. "The anus is situated on the back close
beneath the ciliary circle;" and the "contractile vesicle on a level
with the ciliary wreath." Stein records that in November, 1858, he met
green Stentors (_Polymorphus_) encysted, and he figures one in a
gelatinous flask having a stopper in its narrow neck.
Before closing our account of the Stentor, let us revert a moment to the
ciliary wreath, as it may be made the subject of a curious experiment.
If, for example, the cilia are viewed at right-angles to their length,
they will seem to form a delicate frill, in which a quivering motion is
perceived. But if the table is shaken by a sharp blow, the frill is
thrown into waves, or takes the form which washerwomen give to certain
female articles by the use of the Italian iron, and the ciliary motion
is thus made to take place in different planes, and rendered strikingly
apparent.
One day turning over the Anacharis in search of subjects, a small brown
tube was noticed, from which a glassy rod protruded like the feeler of a
rotifer. Keeping the table quiet, and watching the result, was soon
rewarded by a further protrusion of the feeler, accompanied by a portion
of the body of the inmate of the tube. The feeler was thrust on this
side and on that, as if collecting information for its proprietor, who,
I suppose, was satisfied with the intelligence, and gradually extended
herself, until she stood out two thirds in length beyond the tube, and
set two lobes of one nearly continuous ciliary organ in rapid motion.
Sometimes the creature, _Cephalosiphon limnias_, bent its neck, if I may
so speak, to the right, and sometimes to the left, and sometimes stood
upright, when the true form of the ciliary apparatus could be seen. The
tube of this creature was opaque, from the adhesion of foreign matter,
and presented an untidy appearance, strangely contrasting with the
clear, neat bottles of the Floscules. These Cephalosiphons are very
whimsical in their ways, and many that were sent to different observers
never exhibited their ciliary wreaths, but performed sundry antics,
disguising their true shape.
[Illustration: Cephalosiphon limnias.]
Somewhat like the Cephalosiphon, though much commoner and without the
siphon, is Limnias ceratophylli, which every collector is sure to meet.
The length of the Limnias varies, according to Pritchard, from 1--20" to
1--40". Our Cephalosiphon, when fully extended and magnified one hundred
and eighty linear, looked about three inches and a half long, and was
therefore very small. Just below the ciliary lobes the gizzard was seen,
with its toothed hammers working one against the other. The masticatory
organ differs from the typical form, as represented in the Brachion; and
Mr. Gosse observes of Limnias that "each _uncus_ forms, with its
_ramus_, a well-defined mass of muscle enclosing the solid parts, and in
form approaching the quadrature of a globe. Across the upper surface of
the mass the _uncus_ is stretched like three long parallel fingers,
arched in their common direction, and imbedded in the muscular
substances, their points just reaching the opposing face of the _ramus_,
and meeting the points of the opposite _uncus_ when closed."[20]
[20] The terms _uncus_, _ramus_, etc., have been explained in Chapter
II, page 28.
There is no connection between Limnias or Cephalosiphon and their tubes,
except that of simple adhesion, which takes place by means of the end of
their foot-stalks.
In a former chapter we have described an interesting relation of the
Vorticella, the Cothurnia, whose elegant crystal vases form a very
artistic abode, characterised by possessing a distinct foot. Other
species of the same family inhabit vases which have no foot or stalk, or
live in gelatinous sheaths less accurately fashioned. Sometimes these
creatures are obliging enough to conform to the specific descriptions
which eminent naturalists have given of them, and also to the characters
which the authorities have assigned to the different genera in which
they have been grouped, but the microscopist will often meet with
difficulties in the way of classification.
[Illustration: Vaginicola (?) (A, elongated; B, retracted.)]
Attached to a piece of weed were a number of cylindrical masses of
brownish jelly, with rounded tops, and situated in an irregular and very
transparent sheath, about twice as high as themselves. Presently they
all rose up to four times their previous height, put forth a beautiful
crown of vibrating cilia, and opened a sort of trap-door to their
internal arrangements. In this position they had a long cylindrical
form, gracefully curved, but of nearly equal width from the mouth to the
base, and they readily imbibed particles of carmine, which tinged sundry
little cavities with its characteristic hue. The slightest disturbance
caused the ciliary wreaths to be drawn in, and the bodies to be
retracted, and descend into their house like a conjuring toy, until the
appearance first described was reproduced.
The general form and structure of these objects was like the drawings
usually given of _Vaginicola_, which is said not to exist in groups,
although two individuals are commonly found in one well-shaped cell.
These creatures, however, did not taper towards the base as Vaginicolae
generally do, and perhaps they became aware of this defect in their
figures, for after a day or two a change appeared, and they assumed a
more graceful form by swelling out in the middle, and then growing
slender down to the bottom, very much like the pattern given by
glass-blowers to little vases of flowers.
It is very important to note the changing appearance of animalcules, and
where the same individuals can be observed from day to day, these will
often be found considerable. It is probable that when such particulars
are fully known, the number of species will be greatly reduced, and the
study of these organisms considerably simplified. I have called the
animals just described _Vaginicolae_, but the reader must be prepared to
find similar bodies, inhabiting well-formed vases, either solitarily or
in couples, the latter condition arising from the fission of one
individual without a corresponding division of the abode.
For a few weeks I continually met with groups living as I have
described, in what may be called amorphous cells, which were often so
nearly like the surrounding water in refracting power, as to be
discerned with some difficulty. No trace could be seen of divisions
into separate cells, but they all appeared to live happily together in
one room, and if one went up all went up, and if one went down all went
down, as if their proceedings were regulated by a community of sensation
or will.
Another little curiosity was a transparent cup upon a slender stem,
which stood upright like a wineglass, and supported on its mouth a
transparent globe. By removing a leaf which prevented the stalk being
traced to its termination, it was found to be a Vorticella, and after
two hours the globe was partially drawn in, and reduced in size. Why the
creature was engaged in blowing this bubble I do not know, and have not
met with another instance of such conduct.