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DROPS OF WATER;
THEIR
MARVELLOUS AND BEAUTIFUL INHABITANTS
DISPLAYED BY THE MICROSCOPE.
BY
AGNES CATLOW,
AUTHOR OF 'POPULAR CONCHOLOGY,' 'POPULAR FIELD BOTANY,' &c.
''' For Nature here
Wanton'd as in her prime, and played at will Her virgin fancies." — Milton.
LONDON I
REEVE AND BENHAM, HENRIETTA STREET, COVENT GARDEN.
1851.
PRINTED BY REEVE AND NICHOLS, HEATHCOCK COURT, STRAND.
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DEDICATION.
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THIS slight introduction to one of Nature's inexhaustible sources of wonder and delight, I inscribe to three Sisters, my affectionate friends ; who, by their cultivated minds and kind sympathy, have so greatly enhanced my pleasure in the pursuit.
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Beaconsfield, March 1851.
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Earth hath its Mountains, lifting high
Their viewless summits to the sky ;
Its Plains, that in their boundless maze,
Baffle the eye's far-searching gaze ;
And Seas, immeasurably deep,
Which, in their secret holds, do keep
Treasures unknown to human thought,—
Treasures by human hands unsought.
Yet hath nor mountain, plain, nor sea,
In all their vast immensity,
More power to speak, through wondering sense,
Of the great God's omnipotence,
Than one smalL^mp of water ! — Yes,
Behold its living world ! (no less)
Of creatures beautiful and bright,
Disporting 'midst its liquid light.
Some, like to rare and clustering gems ;
Like lilies some, with silver stems,
Waving in graceful motion, slow,
(Like measured cadence) to and fro ;
Others like fairy bells appear,
Ringing their chimes in fancy's ear ;—
And there are serpent-forms, that glide
'Midst tiny banks of moss, or hide
Their glittering coats beneath the leaves
Of mimic boughs, — which Nature weaves
By the same hand of power, that made
For man the mighty forest glade !
But vainly words essay to tell
What things of wondrous beauty dwell
Within these liquid worlds concealed,
Till by some magic spell revealed.
Come, watch the myriads as they pass
In bright review before the glass
Of wizard Science ! — then declare
If aught on earth, in sea, or air,
Can with these Water Drops compare. — C. P.
PREFACE.
HAVING for several years derived great and in- creasing pleasure from the use of a good micro- scope, particularly in the investigation of the minute creatures contained in water, and wishing to extend this pleasure to others, I venture to make public the following pages ; for though there are several learned works already on the subject, my experience and observations may be
PREFACE.
more genial to the beginner, than the scientific treatises of more able authors. I shall be satisfied if this little work is soon laid aside for those of higher pretension and greater merit ; and I refer the advanced student to the volumes by Ehren- berg, Pritchard, and Mantell.
To give an idea of the wonders to be found in this new world, to which I wish to lead the reader, I shall describe one scene amongst the many to be witnessed. My readers must fancy themselves spirits, capable of living in a medium different from our atmosphere, and so pass with me through a wonderful brazen tunnel, with crystal doors at the entrance.
PREFACE. XI
These doors are bright, circular, and thick, of very peculiar construction, having taken much time and labour to bring to perfection. A spirit named Science opens them to all who seek her, and feel induced to enter her domains. At the end of the tunnel we find other portals, much smaller, and more carefully constructed, and two or three in number ; when these are opened, we are in the new world spoken of. And now I see your astonishment : your minds are bewil- dered with the variety of new beings and forms you behold, all gliding and moving about without noise and at perfect ease.
Now let me direct your attention, first, to the
Xll
PREFACE.
vegetation you see around you ; and remark how different it is from our own. Here is a plain covered with a plant which resembles number- less yards of green figured ribbon, in a state of entanglement. If you examine the substance, you find it composed of cells linked together in myriads, each cell containing granules which form the seed ; these cells in time break up, the imprisoned grains come forth, and from them arise new plants in countless numbers. Here is another, much thicker, and of a different pattern. Now we come to one, which, instead of being round, like the others, is three-sided. Then look on this- — have we anything to compare to it ? You
PREFACE. Xlll
observe it is formed of two half-circular green masses, joined together on the straight side by a narrow band-like tube : you see it has neither root, branch, nor leaf, and yet it is a vegetable.
Now we will turn from the inanimate, to ani- mated beings. That wonderful living creature you see approaching, is worthy of special exami- nation. You exclaim, " This is not a living creature, but a miniature globe, rolling in this new world into which you have introduced us/5 It has this appearance, certainly ; but that it has sense, motion, and will, I think I can convince you, and moreover that it is not one being alone, but is formed of hundreds of minute beings, all
XIV PREFACE.
enjoying life, and grouped together in this curious manner for mutual support. Let us ex- amine it, and you will then be able to believe the evidence of your own senses. You see before you a hollow globe, formed of a material suffi- ciently transparent for you to see within it. Now look at the green dots with which it is spotted thickly, but evenly, all over; they are living beings, attached to the inner side of the globe, each having an eye and a double proboscis, which it protrudes from an opening in the trans- parent case, and by which it has communication with the exterior, and obtains its food. See how actively each moves this instrument, and what
PREFACE. XV
enjoyment they all seem to have ; their united efforts also, continuously exerted, turn the globe round, and thus the whole progresses rapidly. Look within the globe, and you cannot fail to observe, towards the centre, other smaller globes, formed exactly like the larger one, being already full of little individuals ready to enter on active life. — Now you perceive the transparent case is ruptured in one spot, and you fear the globe has met with an accident, and will perish. On the contrary, it is the prelude to new life. The orifice becomes larger; the minute globes con- tained within are making towards the opening : now one has escaped, and now another ; those
XVI PREFACE.
have entered on an independent existence, and are followed by the rest. But watch the little individuals in the case ; you see they are also, many of them, ready to assert their independence, and are leaving their habitation. At last you see the case lies shrivelled, useless ; — but I desist; I see you are lost in admiration at only one of the creatures of this unknown world to which we have paid a transient visit ; we will, therefore, again beg Science to admit us through her brazen tube, and open the crystal portals, that we may pass into our own world; where, though we meet with no creatures of a compound form, no living globes, we find beings like ourselves, who
PREFACE. XV11
will, when Nature is more closely and affection- ately studied, be lost, like us, in wonder, love, and praise.
Microscopists usually speak of the power of their glasses in diameters, or what is termed, also, linear dimensions; that is, the simple measure across, instead of the compound or superficial measurement : a power of 250 dia- meters (quite sufficient for all ordinary purposes) has a superficial measurement of 62,500. The size of objects is calculated by parts of an inch ; an animalcule may, therefore, be TO, TT&-, or even 12000 of an inch in size : — this may be ascertained by knowing the diameter of the
XV111 PREFACE.
field of view in the glass used. Further par- ticulars may be acquired on this subject by referring to works on the microscope.
DROPS OF WATER
No pursuit in the whole range of learning is more congenial to the human mind than the study of Nature. No one can gaze upon the beauty and complexity of her forms without wishing to dive more deeply into her hidden recesses, and, by in- vestigation, to find out the cause of many won- derful effects constantly brought before the eye. Astronomy may raise our thoughts to the Creator in wonder and astonishment by the magnitude of the stars, and the marvellous wisdom by which they are kept in their course ; but " there are miracles of minuteness as well as of magnitude,"
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2 DROPS OF WATER.
and, as an old writer expresses himself, " the ma- jesty of God appears no less in small things than in great ; and as it exceedeth human sense in the immense greatness of the universe, so also doth it in the sniallness of the parts thereof."
The wonderful power of the Creator is as clearly manifested in the formation of the smallest animalcule, as in that of the largest living being ; and perhaps the former even excites our admira- tion in a greater degree, for when we examine, by the aid of " that mighty talisman of wisdom " a microscope, an object which is so small that the unassisted eye cannot discern it, or which the point of the finest needle would destroy in an instant, and find it perfectly beautiful in all its parts, our wonder is the more increased, and the
THE MICROSCOPE.
mind is lost in astonishment at that power which has brought such things to pass. The reflective mind experiences great delight in the investiga- tion of those minute objects, which to the unas- sisted eye are invisible, but which, by the aid of a good microscope, may be studied at ease ; our curiosity, however, is never satisfied, for, though by magnifying an object we find wonders re- vealed which before were hidden, we know that if our glasses were of a still higher power, we should discover more of the mechanism, and find out the use of many parts, that without this in- creased aid would remain in uncertainty. As our microscopes will probably never be made sufficiently powerful to show clearly all the minute creatures contained in water, we shall
4 DROPS OF WATER.
still remain ignorant of some of them. And this fact forms a parallel case to that relating to the stars ; for astronomers have informed us, that, by the increased power of their telescopes, myriads of stars have been discovered, beyond those seen without this powerful aid, and that every year, as the glasses are improved, more and more stars appear : we may, therefore, in viewing the series the other way, imagine with some degree of pro- bability, that water may still teem with life even beyond the reach of the highest powers of our glasses, and we may never be able to say with perfect truth of any drop of water, that it is free from animal or vegetable life. The thought is as overpowering in the one case as in the other, and we should be thankful that, by the aid of
POWER OF THE MICROSCOPE.
science, such systems are laid open for our inves- gation and study. Dr. Chalmers, in speaking of these two wonderful instruments, says very im- pressively— " While the telescope enables us to see a system in every star, the microscope unfolds to us a world in every atom. The one instructs us that this mighty globe, with the whole burthen of its people and its countries, is but a grain of sand in the vast field of immensity ; the other, that every atom may harbour the tribes and families of a busy population/3
I cannot better commence this slight sketch of some of the minute objects contained in water, than in the words of Professor Jones.—
" Take any drop of water from the stagnant pools around us, from our rivers, from our lakes,
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6 DROPS OF WATER.
or from the vast ocean itself, and place it under your microscope : you will find therein countless living beings, moving in all directions with con- siderable swiftness, apparently gifted with saga- city, for they readily elude each other in the active dance they keep up, and, since they never come into rude contact, obviously exercise volition and sensation in guiding their movements. In- crease the power of your glasses, and you will soon perceive, inhabiting the same drop, other animals, compared to which, the former were elephantine in their dimensions, equally vivacious and equally gifted. Exhaust the art of the optician, strain your eye to the utmost, until the aching sense refuses to perceive the little qui- vering movement that indicates the presence of
ANIMALCULES.
life, and you will find that you have not exhaust- ed nature in the descending scale. Perfect as our optical instruments now are, we need not be long in convincing ourselves that there are animals around us, so small, that in all probabi- lity, perseverance will fail in enabling us accu- rately to detect their forms, much less fully to understand their organization/'
These few pages are almost entirely confined to the description of animalcules* found in water : and as all, or very nearly all, are invisible to the naked eye, no subject can be more interesting than that of these wonderful atoms, which, we
The word animalcule signifies little animal : Infusoria is a term more generally used to designate these little creatures, as they abound in all infusions of animal and vegetable matter.
8 DROPS OF WATER.
have every reason to suppose, are by far the most numerous of those beings possessing life. The variety of form, the extraordinary construc- tion, the rapid movement of some, the stationary life of others, and many other peculiarities, will prove subjects of interest and delight to the thinking mind. The one idea that a single drop of water may afford amusement, and excite asto- nishment for hours, to the investigator, is suffi- cient proof of the wonderful powers of the Creator in this minute portion of his works. These little creatures prove quite fascinating ; and hour after hour will be spent in watching their habits and movements, till the powers of the student are ex- hausted. A good microscope, in fact, opens a new world to the possessor, a world of beings totally
A NEW WORLD. 9
different from anything we have been accustomed to see; and the substance of which they are composed is in general so transparent, that the internal structure is visible to the eye, — even the act of digestion can be perceived, and the food traced from its entrance at the mouth, to its passage into the internal cavities ; the eggs, also, can be seen within the body. These and many other peculiarities have been discovered only by very patient investigation, and several natu- ralists, both English and foreign, have almost devoted their lives to the study : and let no one say it is a useless one, for whatever can help to prove the power and wisdom with which this world was created, cannot be time thrown away. To those who only use the microscope as an
10 DROPS OF WATER.
amusement (and it is a never-ending one) a short time occasionally is well bestowed on one of the most beautiful parts of the creation.
There are upwards of seven hundred species of Infusoria known and described. These are of all shapes and forms, some even assuming a va- riety in themselves ; many possess eyes, others have none ; some move so rapidly that the eye cannot follow them, and others are attached to various substances ; some have very many stomachs, or internal sacs, and others have only one ; others, again, form a compound mass, that is, many in- dividuals live in the same transparent case, and some are so minute that by the aid of the best mi- croscopes they cannot be clearly discerned. But enough has been said to excite the mind, and in-
INFUSORIA AND ALGJE. 11
terest the intelligent reader in the subject, and we will at once proceed to a more detailed history of the peculiarities of Infusoria ; premising that one family, the Desmidiea, which was by Ehren- berg considered as belonging to the animal king- dom, has, after much variety of opinion by natu- ralists, been placed amongst vegetables, and con- sidered as minute forms of Sea-weeds (Alga) \ these will be described slightly in the sequel.
After the first expense in the purchase of a good microscope, amusement may be constantly obtained at all seasons of the year, without any trouble but that of procuring and selecting water likely to contain animalcules, and they are mira- culously abundant everywhere. Many people are disgusted after viewing water through a micro-
12 DROPS OF WATER.
scope, and suppose that all water abounds in living creatures, and that, consequently, we drink them in myriads. This is an error : there are none, or very few, in spring water, and, as no one would think of drinking from a ditch, or stagnant pool, where plants abound, there is little to fear. If necessitated to partake of water abounding in life, the person is either ignorant of its state, or the want is so urgent that the thought does not occur ; and even should it arise, these deli- cate transparent little atoms would not be per- ceived by the taste ; — this fear or disgust may therefore be dismissed. Many waters abound in the larvae of gnats and other insects, and minute creatures of the crustaceous order, but these can generally be seen by the naked eye.
LOCALITIES. 13
In all parts of the world, and in most waters where aquatic plants in a healthy state abound, these invisible creatures may be met with, and not only in stagnant pools, but in running streams, and the broad ocean. Among water- plants these .little beings find shelter and food ; therefore, when water is brought from these localities, some of the vegetation peculiar to the pool, or stream, should be procured at the same time. They swarm amongst duckweed (Lemnd] . Many are found also in clear shallow pools, par- ticularly in the spring. When a pond is ob- served to have a stratum of dust on the sur- face, or a thin film, it wih1 generally be found almost entirely composed of living creatures. This dust-like appearance consists nearly exclu-
c
14 DROPS OP WATER.
sively of species of the most beautiful colours, such as Pandorina, Gonium, &c. A shining film of various colours is also occasionally seen on standing water : this is composed of Infusoria ; a red appearance being often given to water by some species, and by others a yellowish hue. Sheets of water often assume an intense green, from the presence of many of these minute bodies. Lakes have been known to change their colour very mysteriously, and to have caused some alarm in the superstitious ; but it is now known to arise from Infusoria, as they are attracted to the sur- face by the sun in the middle of the day, and descend as that luminary declines ; — thus the lake will be clear, morning and evening, and turbid, or of different colours, in the course of
REPRODUCTION. 15
the day. If stalks of flowers are steeped for a few days in water, it will be found to swarm with life ; even a few dead leaves, or a bit of dry hay, will produce the same effect. At first monads will appear ; these will be succeeded by specimens of the genera Paramecium, Amoeba, and those of the class Eotatoria. I have tried these experiments, and always with success. If the infusion be kept a few weeks (particularly that formed with leaves), one peculiar kind of animalcule will swarm to a most astonishing degree, so that a drop will contain hundreds, so close together that they form quite a crowd, and yet all are in a state of activity, and feeding from the vegetable matter disengaged from the decaying leaves. They are not even con- fined to these localities, for lakes and rivers, the
16
DROPS OF WATER.
fluids found in animals and vegetables, strong acids, and also the briny ocean, are full of these in- teresting creatures. One kind of phosphorescence, (an appearance which is so often observed by the sea-side and at sea,) is occasioned by some species ; and when we remember that this lumi- nosity often extends for miles, we are lost in astonishment at the immensity of their numbers. And here I may mention the evident use of these wonderful beings. They appear wherever decaying animal or vegetable substances are found in water, and are extremely useful in de- stroying what would otherwise taint the air with noxious gases and smells. Minute algae also assist in preserving the purity of the water in which they live ; they serve as food, also, to
IMPORTANCE IN CREATION.
17
animals higher in the scale of creation than them- selves. Captain Sir James Ross, in his Antarctic Voyage, speaking of a small fish found by him in the South Seas, and stating by what means it and many others are fed, says, " All are even- tually nourished and sustained by the minute infusorial animalcules, which we find filling the ocean with an inconceivable multitude of the minutest forms of organic life/3 We may infer from this, the immense importance of the Infuso- ria in the scale of existence, for although only re- motely supporting the higher animals, yet the want of them would be greatly felt. Ehrenberg* states, that a single drop of water may hold five
* A celebrated Prussian naturalist, who has devoted his life to the mi- croscopic investigation of animalcules and other minute objects.
TIT
18 DROPS OF WATER.
hundred millions of the smallest animalcules. What, then, can be the population of a lake, or of the ocean !
I have watched specimens of the genera Flos- eularia, Forticella, and Stentor, for hours at a time, and they have never ceased to feed on mi- nute portions of animal and vegetable substances, brought to them by the current they are enabled to make in the water ; others eagerly pursue their prey, or feed on the decaying vegetable matter floating about : indeed, the appetite of these little creatures seems insatiable. Many genera have a strong chewing apparatus, like a mouth armed with teeth. All seem employed in the same way, though using different methods :--much decaying matter must thus be taken away by
ACTIVITY OF HABITS. 19
this insatiable, though miniature army, provided for the purpose. They, in their turn, afford sustenance to aquatic insects, which are again preyed on by fishes ; and thus food is prepared for more highly organized animals, and lastly for man.
Animalcules have never been observed to rest, or at least to sleep ; but this may be partly owing to the light necessarily used in viewing them, which forms an artificial sun -light, exciting their powers of motion : they may rest during darkness, when they cannot be seen by us. Many are only at- tracted to the surface of the water by the light of the sun, and are difficult to be obtained on a dull day ; they are, however, not much affected by cold or heat, for they are procurable in winter
20 DROPS OF WATER.
as in summer, though not in such profusion : they are found even under thick ice, and I have frequently broken, in severe frost, the frozen sur- face of a pond, and, inserting a bottle, have ob- tained some most interesting kinds. Many of the Polygastrica will bear a great degree of cold, even more so than those of the class Hotatoria, whose organization is of a higher order.
It has, I believe, been generally observed, that the more simple the organization of animals, the more retentive is the creature of life, and this is the case with these minute beings. The Rotifer vulgaris will even bear revivification several times. Dr. Carpenter relates that he tried the experi- ment six times with twelve specimens, and each time some were perfectly restored to animation.
TENACITY OF LIFE.
21
By allowing the drop of water which held them to evaporate, and at the end of twenty-four hours giving them a fresh supply, he succeeded six times in restoring some of them : at last two only were left, and these unfortunately he lost. Ehrenberg affirms, that if thoroughly desiccated they cannot revive, but that they may remain in a lethargic condition if deprived of water for a certain time only. The same naturalist observes that when an animalcule is frozen with the water, it is surrounded by an exceedingly small portion which is unfrozen, occasioned probably by the animal heat of its body; but, should the cold be so great as to freeze this, the crea- ture dies. Animal heat in such an atom ! how marvellous ! Yet they will bear a great degree
22 DROPS OF WATER.
of heat also. The same naturalist says, that the Polygastrica will bear the temperature gradually raised to 120° of Fahrenheit, and some even to 200°, but if raised suddenly they die at 140°. Now, if we consider that water raised to 212° is boiling, we shall be as much astonished at their powers of enduring heat, as cold. Sir James Ross, in his Antarctic Expedition, found upwards of seventy species of Polygastrica with lories, or siliceous shells, in fragments of ice.
It will, therefore, be seen, that animalcules are obtainable at all seasons, and in every place where there are ponds or pools of water ; or they may be procured from water-butts, or by placing leaves, hay, or almost any vegetable sub- stance in a little water, which lias been previ-
VARIETY OF FORM. 23
ously found to have nothing living in it. It has, therefore, been proved, that after the first ex- pense in the cost of a good microscope, and with proper care, so that no repairs are required, the
i
amusement is cheaper than most others ; never ending, and never failing in interest.
A few particulars of the formation, and pecu- liarities of structure, of these wonderful atoms, will now be entered upon.
In the first place, the variety of form is most astonishing, and strikes the observer perhaps more than any other peculiarity. They are of all imaginable shapes, and may be likened to many objects with which we are familiar, — as tops, trumpets, pincushions with pins in ready for use, telescopes, balls, leaves, sticks, threads,
24 DROPS OF WATEll.
bells, hollow spheres, &c. ; there are also others like different kinds of fruit, flowers, fish, eels, and serpents ; others, again, are egg-shaped, round, square, three-cornered, oval, spiral, spindle- shaped, star-shaped; besides some representing funnels, cylinders, flasks, and many having an apparatus which perfectly resembles a rapidly- turning wheel. Most of these forms will be noticed hereafter, when the genera and species are more minutely described.
Animalcules have either a soft naked body, or are covered with a kind of siliceous shell, or horny case, which is transparent, and varies much in form ; in some instances nearly covering the
* "In some cases it is composed entirely of silica; in others, of liine, with a portion of oxide of ixon."-—Pritchard.
MUSCULAR POWER. 25
body, in others only forming a shield. This shell is called a Zorica, and the term loricated is used to point out the species having a shell. None are supposed to have internal bones, but their muscles must be of the most complicated construction, to enable them to move easily and rapidly, which many of them do in an astonish- ing degree. One species (Vorticetta convattarid) is attached to leaves and stalks, by a transparent thread of some length : this it has the power of suddenly contracting when danger threatens, so that the body is instantaneously removed to a distance. The muscles in this thread-like stalk are so contrived, that it assumes on these occa- sions a corkscrew or spiral form, and this action brings the body close to the leaf on which it is
D
26 DROPS OF WATER.
fixed ; after the lapse of an instant the creature gradually uncoils its stem, and is again employed in procuring food. The muscle that produces this motion (so rapid that it cannot be followed by the eye) is seen within the stalk, with a glass having the power of 250 diameters. There are many equally wonderful displays of muscular power to the one here described.
An eye, which is generally of a red colour, is very visible in some genera, but not to be dis- cerned in others, and probably they are destitute of that organ. By some naturalists it is doubted whether these spots are eyes ; but, as animalcules are evidently excited by light, it is more than probable : most of the Eotatoria possess them, some species even having three, and one genus
ORGANS OF LOCOMOTION. 27
having seven or eight, on each side of the head ; but they are less frequent in the first class, though, even there, many species have two and others one. How astonishing that so compli- cated a structure as the eye should exist in so very diminutive a creature !
Their organs of locomotion, or means of moving through the water, are as varied as their 'forms. The simplest method is by the aid of a proboscis, which seems to be useful both in ob- taining food and in giving motion to the body, the creature using it as a kind of paddle, or oar ; in some species there are two of these members. Others, again, have many short ones (called cilia) surrounding what may be termed the mouth, and by which they not only bring food to that
28 DROPS OF WATER.
orifice by their rapid movement, which creates a current in the water, but the same action propels the body with wonderful speed, so that the eye can scarcely follow it. These cilia, when in mo- tion, have the appearance, to the eye of the spec- tator, of a rapidly-revolving wheel, and this ex- traordinary effect is produced in the following way. — Each of these little thread-like members has a rotatory motion, the point describing part' of a large circle, and the base (which is seated on a bulb) part of a small one ; this motion, when all are seen in action at once, gives the appear- ance of a turning wheel, because the apparent revolution of the whole takes place in the same time as the real rotation of a single one. I know nothing more wonderful than this forma-
ORGANS OF LOCOMOTION. 29
tion, and, indeed, it is one of the most interesting spectacles that can be observed by the aid of the microscope. It is supposed by some naturalists to be also the means of respiration. In some genera the cilia are not confined to the opening, but cover the whole body, and by this means they progress rapidly through the water, having a revolving motion, like that of a ball. Some have a gliding movement, similar to the snail or leech ; others, again, have a foot, with which they catch hold of substances that come in their way. In many species, also, bristles are attached to the surface of the body, which may act as fins ; and some kinds have appendages, curved at their extremities, and serving as hooks to attach the animal to sub-
D 3
30
DROPS OF WATER.
stances on which it feeds. Some few are mo- tionless, others revolve on the centre, or move by leaps, or undulations \ and, in fact, the}7 seem to use every kind of motion that can be conceived. Infusoria increase more rapidly than other organized beings. In some of the modes of reproduction they resemble animals of a higher order of creation. Very many species lay eggs, which they attach to water-plants ; others pro- duce their young alive; but many increase by germs, or buds, growing from their own body, which are separated when sufficiently arrived at maturity ; others, again, divide into two or more parts, and each becomes a new animalcule with equal powers. But, perhaps, the most ex- traordinary is the compound formation of the
MODES OF REPRODUCTION. 31
Folvocina family, in which many individuals are enclosed in a transparent globe, where they have increased by self-division : as they grow in size the case enlarges also, but con- tinues entire till they have arrived at maturity, when it bursts, and the inhabitants, as they may be called, are set at liberty, each forming in its turn a new globe, and again increasing by self- division. How wonderful are all these peculiari- ties in beings unseen by the naked eye ! These facts must create an eager desire to witness these marvellous atoms ourselves ; and those who have a taste for investigation in natural history, will here find ample scope for amusement.
It was formerly supposed that animalcules re- ceived their nourishment by absorption through
32 DROPS OF WATER.
the skin, as in many kinds mouths could not be discovered ; but by feeding them on coloured substances, an internal structure has been ob- served equally complicated with that of larger animals, and consisting of muscular and nervous systems, all wonderfully suited to their respective wants. As these creatures are for the most part transparent, the being enabled to feed them on coloured substances, such as indigo, sap-green, and carmine, has given naturalists the power of investigating the internal construction, which would have been impossible without this plan. The method is to place a very small portion of the carmine, well rubbed down with a little water, in a drop containing animalcules ; they will immediately appear very active, and in a
^
CARMINE, ETC., AS FOOD. 33
few seconds the internal sacs will be filled with red colour, whilst the rest of the body will re- tain its original appearance. The cilia, probosci- des, and other appendages will also be much more clearly perceived than without the assistance of the foreign substance. This experiment requires some nicety and care, and the new diet does not seem to injure the animalcules, for, as indigo'and sap-green are vegetable, and carmine is an animal production, they probably do not find them dis- agreeable; but no metallic substance must be used. It is a wonderful fact, that a drop of water exhibiting to the eye only a few particles of ve- getation and sand, may, by the aid of a glass, be found to contain a crowd of animated be- ings, all beautifully and curiously constructed,
34 DROPS OF WATER.
all enjoying life, and providing for their various wants — their beauty so great, that we can scarcely bear to lose sight of them by with- drawing the eye from the microscope; and yet that drop is as nothing in the scale of creation, and we wipe it away with hardly a thought of what it contains, intent on viewing fresh wonders in the next drop we may take up. The educated mind, however, knows that nothing is made in vain, and that even the minute beings under observation have had their influence in maintaining the purity of the water and atmosphere, and thus spreading around, benefits of which the uninstructed are perfectly ignorant.
This introduction will be concluded by a short
FOSSIL INFUSORIA. 35
account of fossil Infusoria. A fossil animalcule ! Is it possible that such minute and delicate bodies can be changed into, and preserved as, fossils ? This is really the case, and the following extracts will prove the truth of this remark.—
Ehrenberg says, " The Infusoria, in conse- quence of their siliceous shells (lorica), form in- destructible earths, stone, and rocky masses. With lime and soda we can prepare glass out of invisible animalcules, use them as flints, pro- bably prepare iron from them, and use the mountain-meal, composed of them, as food in hunger."
To prove this marvellous fact, the following
interesting extracts are drawn from Pritchard's
c History of Infusoria ' :—
36 DROPS OF WATER.
" The shell-like coverings (loricce) are found in large masses, covering many miles of the earth's surface, and occur, when indurated and mixed with argillaceous and other earths, in the form of siliceous rock, slate, &c. These remains of the primeval inhabitants of our globe are re- cords in the pages of history, penned by Infinite Truth, unbiassed by ignorance and prejudice ; and form some of the first-fruits of the effective application of achromatic glasses in our micro- scopes." "It is hardly possible to take up and examine a dozen flints without discovering spe- cies of Infusoria enclosed within them. These may be seen under the microscope, when very thin sections are made/3
As flint is used in the manufacture of glass,
FOSSIL INFUSORIA. 37
the shells of these creatures are thus found coming into use, after the inhabitant has been dead thousands of years. Dr. Mantell remarks, in his ' Thoughts on a Pebble/- -" Investigation has shown that a great proportion of the mass of the (flinty) pebble, is actually composed of the aggregated fossil skeletons of animalcules, so mi- nute as to elude our unassisted vision, but which the magic power of the microscope reveals to us, preserved, like flies in amber, in all their original sharpness of outline and delicacy of structure." An extract from another author will prove that chalk abounds also in remains of Infusoria.- " Throughout the chalk beds there are layers of flint, — that is, masses of silex, or flint, of various sizes, from a pea to a man's head, each lying
E
38 DROPS OF WATER.
detached amidst the chalk. Whence this great quantity of a substance, which seems to be charac- teristic of the chalk formation ? The supposition is, that it has been derived mainly from siliceous coverings of animalcules ! The remains of many of these minute and humble animals have been discovered in the chalk, some of them being the first animals which yet exist in the species upon earth. It has also been found that the flints invariably include the remains of some sponge, or other humble animal form, the lineaments of which are often beautifully preserved amidst the dark glassy substance, and may be detected by a microscope, if not by the naked eye. Now, if the silex from the coverings of the dead Infu- soria, were in solution amidst the settling sub-
FOSSIL INFUSORIA. 39
stance of the chalk, any decaying sponges, Al- cijonia, sea-urchins, or other animals placed there, would be sure to collect the particles of the silex around them, and thus be converted into flints/3 " We refer to beds of
greater or less thickness, composed exclusively of the solid' remains of animalcules — creatures individually so small, that only a microscope could enable human eyes to see them. Such a rock (called Tripoli) is found at Biliu, in Bohe- mia,* and at Planitz, in Saxony. It has been used as a powder in some of the arts, for ages, without any suspicion of its being thus composed. But within the last few years M. Ehrenberg, a
* The series of strata forming this polishing slate is about fourteen feet thick.
40 DROPS OF WATER.
scientific Prussian, has fully ascertained that it consists simply and wholly of the siliceous cover- ings of certain minute creatures, some of which belonged to species still to be found in stagnant water. To common perception, the powder of which the rock may be said to consist resembles flour ; and in Norway, where it is called Berg- mehl (that is, mountain meal), it is actually used in times of famine as food ; for which it is not entirely unsuitable, seeing that there is always a per-centage of animal matter left in it, in addi- tion to the siliceous shields.* So extremely small are the creatures of which these rocks form the sepulchre, that, according to M. Ehren-
* Dr. Carpenter says, this earth contains a large proportion of animal matter, — about 80 per cent, of its weight.
FOSSIL FLOUR. 41
berg's calculation, ten millions of millions of individuals might be required to fill the space of a cubic inch. Yet in the smallest of these crea- tures there have been found several stomachs, besides other organs ; and minute as the cover- ings are, they are variously sculptured or marked, so as to form distinctions of species."
Here may be added, also, the remarks of other authors on this curious subject. — "In Swedish Lapland, under a bed of decayed mosses, forty miles from Degesfors, in Umea Lapmark, is found a stratum of this substance known there by the name of Bergmehl. When examined by the aid of the microscope, it is found to consist almost entirely of the remains of minute or- ganisms. In seasons of scarcity this is made
E 3
42 DROPS OF WATER.
use of in certain quantities mixed with flour in the manufacture of bread by the poor : not that it contains any nutriment (or, at all events, it pos- sesses it in so small a quantity, as not to be able alone to support life), but on account of its serv- ing to distend the stomach, and thus to prevent the unpleasant sensations attendant on an im- perfectly-filled state of that organ.33 This sub- stance seems also to be occasionally used in China, as is shown by the following statement published in 1839 by M. Laribe, a missionary :- "This earth is only used in seasons of great dearth. One of our Christians, who, at the period of the last famine, fed upon this substance, with five other individuals composing his family, informed me, that when they made use of it,
FOSSIL FLOUR. 43
they bruised it into a very fine powder, mixing three parts with two of rice-powder, or, better, the flour of wheat, to make small cakes, which were seasoned with salt or sugar. Recourse was only had to this in times of great want ; and that being over, no one ever dreamed of making use of it as an article of food. Those persons who employed the fossil flour without mixing it with vegetable meal, scarcely ever escaped death/3 " This mountain meal is principaUy composed of the flinty coverings of the Namcula viridis, Gal- lionella sulcata, and Gomphonema gemmatum, all of which are to be found in a living state/3
Dr. Carpenter, in his interesting work entitled 'Principles of Physiology/ whilst speaking of fossil animalcules, says, "It is peculiarly inter-
44 DROPS OF WATER.
esting to trace such occurrences in progress at the present time. The author has seen water, brought from a lake in the island of St. Vincent, crowded with the shields of races of Naviculte which at present inhabit it ; and the mud which is being deposited in abundance at the bottom of the lake, is almost entirely composed of them/3
There can be few subjects more interesting to the thinking mind than these details of the living animalcule, and its fossil remains.
" These viewless beings, to whom Each tiny drop is as an ample world, each day A life of ecstasy, fulfil their Maker's high behests, And, in obeying, find felicity."
An outline of the history, habits, and loca-
CLASSIFICATION. 45
lities having now been given, an investigation of the scientific classification, and more lengthy details of the most interesting genera and species, will follow ; the reader or student will then be enabled to understand the more learned works of Ehrenberg and Pritchard, whose volumes are so often quoted, and to whom these pages are indebted for many of the~descriptions.
The object of this little book is not to treat scien- tifically of the minute forms mentioned, but only to induce the lover of nature to search into their curious history, and also to prepare the student for more learned works ; the classification will not, therefore, be entered upon minutely — a short account only of the great classes into which they are divided will be sufficient. But it must first
46 DROPS OF WATER.
be stated, that naturalists have some difficulty, in many cases, in determining whether the minute object under examination belongs to the animal or vegetable world. This appears very extraor- dinary, but when the following details have been read, and it is found that what seemed to be a plant, has within it certain granules which, when discharged, act like living beings, swimming about, having all the movements of animals, yet at last fixing themselves to a substance, and after a time assuming the appearance again of vegetation, it will be acknowledged that the sub- ject is one of extreme difficulty. Professor Rymer Jones remarks, that the physiologist has many difficulties, " who endeavours to draw the boundary between these two great kingdoms of nature ; for
CONFERVA. 47
so gradually and imperceptibly do their confines blend, that it is at present utterly out of his power to define exactly where vegetable exist- ence ceases, and animal life begins.''
In some of the fresh-water Conferva which form the green slimy patches seen in ponds, the reproductive organs are the little green grains filling the transparent tubes of which the plant is composed. These, when ripe, leave the tubes, and have a very visible, and voluntary movement in the water, so like animal life, that they have in that state been taken for animalcules. But the Conferva comoides, growing on the coasts of Picardy and Normandy, and mentioned in a work entitled ' Observations stir les Limites qui separent le regne vegetal du regne animal,' is of
48 DROPS OF WATER.
a very remarkable construction, and peculiarly interesting, proving how nearly connected are the two great classes of animals and vegetables. This little plant-like substance is seen at low water, attached to stones, and is in the form of a hair pencil, from half an inch to an inch in length, each thread being finer than a hair, and slightly branched, rounded and compressed : they contain a number of small yellowish bodies, which are first round, then oblong, afterwards more pointed at one end, which becomes transparent. They are packed very closely, but when the cell bursts, they move about in the water in the most amus- ing manner, and keep up a voluntary, incessant motion for a considerable time. They at last fall down in immense numbers on the stones, and
ULV^E.
49
emit a globule of particles which is supposed to be their fry. This substance lengthens, and branches, and again forms long hair-like threads, similar to those from which it sprang. In the green ditch-laver (Ulva buttata, or minima), by the aid of the microscope, may be seen a num- ber of green granules,- — these, when separate and loose in the water, have a rapid movement, as if chasing each other. In time, two ap- proach, and touch one another, then retreat, touch, and retreat again ; then four combine to execute the same movement ; and at last, the whole party thus grouped in fours, dance together in seeming confusion. After a time the motion ceases, and they form the new substance known as Ulva*
* Lindley's Botany.
F
50 DROPS OF WATER.
It will be easily imagined, therefore, from this marvellous account, how difficult it must have been to classify and arrange these little atoms, and, consequently, naturalists have differed greatly on the subject. The microscopist will be greatly struck with many minute green ob- jects, of exquisite form, which will be seen lying quietly at the bottom of the water, having no movement, but greatly resembling a seed, or pod. These have been, and still are by some naturalists, supposed to be of an animal nature, from the movement of the granules contained in their sub- stance, but by late writers they are considered vegetables. They will, however, be inserted here, not only from the interest they excite, but from their frequent occurrence in water in which ani-
CLASSIFICATION. 51
malcules abound, so that the student may not be at a loss as to their nature when they are met with.
Infusoria are comprised under two great classes, Polygastrica and Rotatoria ; the former being dis- tinguished by appearing to have numerous vessels, or stomachs, for carrying on digestion, and the latter having but one. This is Ehrenberg's method of classifying them ; and though Meyen and others think the vessels of the first class are not stomachs, the name must be retained until the fact is ascertained.
After some experience in viewing animalcules with a glass, their general form and outward appearance is sufficient to enable the observer to determine in which class to place them. The Rotatoria have usually a foot near the extremity
52 DROPS OF WATER.
of the body, and rotatory organs affixed to the head : these, and their higher organization, render them in general distinguishable from the Poly- gastrica. Each of these classes is divided into many families, genera, and species, the different kinds amounting to nearly eight hundred well- ascertained species. This number will probably increase, as our microscopes are improved, and observers multiply. We can understand that the labours of microscopists must have been very great, when we consider the extreme difficulty of watching these minute productions. It fre- quently happens that a specimen is lost to view after only a very slight inspection, and perhaps another of the same kind is not met with again for days or weeks. I cannot describe the regret
CLASSIFICATION. 53
I have felt when having to lose sight of a very interesting specimen, perhaps new to me at the time. After watching it for hours, a period must come when the drop containing it will either eva- porate, or an additional drop or two must be mixed with it, and then the probability is that it may never be seen again. If very small, and not fixed to a leaf, this is most likely to happen. The movements of many are also so rapid, and the impossibility of touching them so great, that it is only wonderful we have such correct and minute accounts of these atoms, which are so completely invisible to the naked eye.
As these pages only aspire at being considered an introduction to an interesting study, I shall not enter on a scientific arrangement, further than
F3
54 DROPS OF WATEE.
that of describing the objects I select in regular succession, according to Ehrenberg's classifica- tion, with the exception of the family Bacittaria, which I place first, as the species are now consi- dered (at least, the greater part of them) to belong to the vegetable kingdom. I shall suppose four DROPS OF WATER to be under inspection at diffe- rent times ; and though it seldom happens that the objects I have depicted in each drop are found alone at any period, still I have thought this plan not an unnatural one, giving clearly some idea of classification, and preparing the way for more scientific works, when the subject is made a deeper study. The specimens contained in the First Drop are minute Algae, and other objects nearly allied to them : they are found more particularly in
CONTENTS OF THE DROPS. 55
bog-water, and may be seen in great numbers together. Those contained in the Second Drop are poly gastric, and are often found in prodigious numbers in spring, to the exclusion of others. The individuals of the family Vbrticettina (also Polygastricd) will nearly occupy the Third Drop ; and their beauty is so great, that they fully attract the attention when present in the field of the microscope. The Fourth Drop will be occupied by the class Rotatoria. By this means some of the most striking microscopical objects found in water will have been examined.
DROP I.
I HAVE mentioned in the introductory chapter, that many of the microscopic objects found in water are at present not sufficiently known, to enable naturalists to determine, beyond dispute, whether they belong to the animal or vegetable kingdom. Ehrenberg thinks, to the former be- long all the genera I am about to describe in this section. Dr. Meyen is of opinion that many of these are decidedly vegetable ; and others imagine that all may belong to the latter kingdom. By
MINUTE ALG.E. 57
botanists, some of them are placed among the minute Algae ; and if colour and general outward appearance alone are considered, connected with the fact, that in most cases they are immoveable, the young student will conclude that the botanist is nearer the truth than those who argue for their animal nature. Still, we must come to no hasty conclusion, for if the learned differ on the subject we must be content to wait for further informa- tion; and it is not unlikely that these minute and puzzling atoms may form the connecting link between the two kingdoms. Ehrenberg describes them as polygastric, the body having variable processes, and being covered by a lorica, or shell ; as undergoing self-division, but most of them being connected together by a thread,
58 DROPS OF WATER.
forming chains, or rounded groups. This im- perfect division is similar to that described in the family Vibrionia, amongst animalcules. These facts caused Ehrenberg to conclude, after patient investigation, that they belong to the animal kingdom. Dr. Meyen, on the contrary, argues for their vegetable nature. The want of actual motion in most of them, is a great point in favour of his opinion ; and, regarding the self-division, he affirms that it is very common in the lowest plants, as well as in some of the organs of the higher kinds. The green corpuscles seen within the DesmidieiB are similar to those found in the cells of the Conferva, though Ehrenberg con- siders them as eggs. This group, therefore, may with great reason be looked upon as belonging
MINUTE ALG^E. 59
to the vegetable kingdom;* but another portion, termed the true BaciZZarite, and named Navicu- lacea, after the most interesting genus, have a greater resemblance to animal life, much more spontaneous movement, and currents are also fre- quently observed on the sides, as if minute cilia existed ; still Dr. Meyen classes even these with plants, and observes that they are by no means so free and active as the spores of the Algae. Notwithstanding some uncertainty respecting the true nature of this family, it is very interesting, and some species are possessed of great beauty.
i
* Mr. Ralfs's able work on British Desmidiese appears to set the subject at rest, as regards this section of the family Bacillaria ; for he parti- cularly mentions that the presence of starch (peculiarly a vegetable pro- duction) may be detected in the atoms composing it, by the application of tincture of iodine, which turns them of a violet or blue colour.
60 DROPS OF WATER.
The first section, the Desmidiea, are a family of microscopic Algae, distinguished, like most other plants, by their green colour ; they are formed of vessels or cells containing a green sub- stance. These cells, or joints, separate either com- pletely or only partially, some genera forming long filaments, by the union of many cells, and others are seen generally only in pairs. I shall describe a few of the most singular in appear- ance, and those most commonly found.
The genus Desmidium is seen as a long, pale green filament, formed of many cells. There are two species. Desmidium Swart zii (Plate I. fig. 1) has three edges, forming a triangle when viewed transversely ; when many cells are connected together, and the filament is lying
MICRASTERIAS. 61
longitudinally under the eye of the observer, a dark line is seen to cross alternately from one side to the other — this is caused by the twisted form of the filament, and the line is the third corner of the triangle. It separates into single joints or cells, and then shows its triangular shape, with the green substance within forming a star of three points. This is a species of common occurrence. Desmidium guadrangulatum is more rare, and only seems to differ from the last in the number of sides. There are other genera of these thread- like Algae, but this is the most striking.
The genus Micrasterias contains many sin- gular forms ; they are more or less round, and flat, deeply divided into two lobed segments, or cells, and notched or cleft at the edges, sorne-
G
62
DROPS OF WATER.
times even rayed ; the colour is green, but with the edges or rays transparent, forming beautiful objects for the microscope. They will be viewed with great interest, and are so large as to be visi- ble to the eye without the aid of a glass, but only as a small green clot. The mode of increase is very remarkable : — the two segments are united by a narrow band or tube, and this produces two new minute segments, which gradually in- crease, and separate the two original portions ; the young acquire colour, and soon look like the old ones ; then the latter are entirely separated, each taking one of the newer formations with it. This singular process is constantly being repeated. Micrasterias denticulata (Drop I. fig. 2) is one of the most common found in bog-water : it is
EUASTRUM. 63
very prettily denticulated at the margin, besides the deeper divisions -9 and the white edge, and bright green centre, are strikingly beautiful. M. crenata is smaller, and less denticulated. M. rotata is large, and with, two of the divisions cut in a curved line. There are several other species, but they are rare.
Euastrmn somewhat resembles the last genus, but the species are more oblong in form, and have circular protuberances on the surface. They are attractive, also, from their size. Uuasfmm oUongum (Drop I. fig. 3) is common in pools : the form of it is much longer than broad, with five or six prominences. Euasirum inslgne is smaller, has the segments inflated at the base, and taper- ing into the form of a neck, with the end a little
64 DROPS OF WATER.
dilated ; the prominences are arranged two on each segment. There are more than a dozen species of this genus known.
In the genus Cosmarium the segments are more or less round, and neither dentated nor rayed at the edge. Cosmarium margaritifermn (Drop I. fig. 4) is rather abundant ; there are more than thirty species known.
Xanthidium greatly resembles the last, but is armed with spines, and has a circular projection near the centre of each segment. Xanthidium armatum (Drop I. fig. 5) has short thick spines, placed in pairs round the edge of each segment, each spine having several points, and occasionally some scattered on the disc. This species is often found in masses, floating in the water of shallow
ST AURA STRUM. 65
pools. Xanthidiiim aculeatum has the spines simple, shaped like a horn, and numerous ; other species have them longer, and but few in number.
The genus Arthrodesmm has the segments entire, with a single spine on each side; the two segments, joined by a very narrow band, are broader than long, and smooth. There are often four united together. Arthrodesmm con- vergens (Drop I. fig. 6) has the spines of its seg- ments curved towards each other. A. incus has the spines diverging outwardly, and the ends truncated.
The genus Staurastrum has a great variety of species, amounting to about forty. They are mostly of minute size, and differ but slightly at
66 DROPS OF WATER.
first view from the last genus. The segments are broader than long, and in many species elon- gated into a process. This is of a more angular form than Arthrodesmus. 8. cuspidatum (Drop I. fig. 7) will serve as an example.
Closterium is a very interesting and striking genus. Many of the species are large, and all of a deep green colour ; the form also is very grace- ful, the two valves are elongated, narrow, curved, and often of the form of a crescent, the union of the two being marked in the middle by a pale line, but there is no constriction there, as in the former genera, and there are neither spines, nor prominences of any kind. In some species there are lighter green dots arranged down the length, or scattered about, and in most may be perceived,
CLGSTERIUM.
67
near the ends, with a high magnifying power, a transparent spot, containing minute granules in constant motion. Some species are smooth, others striated — but this is rarely seen, excepting when the case is emptied of its green matter. The method of increase is very similar to that described in other genera, but differs in some degree. The pale line in the centre becomes double, the intermediate portion gradually in- creases, and then another transverse line becomes visible in its centre ; when mature, complete separation takes place there, and two Closteria are formed. The species are above twenty. C. aceromm (Drop I. fig. 8) is a very pretty object, bright green, and very slender in form ; C. moniliferum rather crescent-shaped, with a
68 DROPS OF WATER.
line of transparent dots down the middle; C. Diante (Drop I. fig. 9) is quite crescent- shaped, small and slender ; C. setaceum (Drop L fig. 10) is perhaps the most beautiful — it is very slender in the centre, the ends tapering into long beaks, and rather curved, which give it an elegant form. These specimens will be sufficient to make the reader or microscopist familiar with the genus.
Spirottfnia greatly resembles Closterium in size and general form, but is easily distinguished by the green matter forming a spiral line from one extremity to the other ; there is no mark of division in the centre, and the ends are round.
Occasionally may be seen very minute bun- dles of green objects, like little faggots ; — these
PEDIASTRUM. 69
belong to the genus Ankistrodesmus, and there is but one species, falcatus.
The next genus, Pediastrum, is composed of many species, all being more or less like a star ; they are formed of several little cells, four or more united together either in a single or double circle : they are very curious, and soon attract notice. I shall only give two species, which I have myself seen repeatedly — P.pertusum (Drop I. fig. 11) and P. Napoleonis (Drop I. fig. 12) : the figures show their extraordinary forms more clearly than any words.
Scenedesmus comprises little objects composed of from two to ten minute cells, arranged in a row, instead of in a circle, as in the last genus. 8. quadricaudata (Drop I. fig. 13) is common.
70 DROPS OF WATER.
This slight sketch of the Desmidiea will suffice to call the attention to an interesting and won- derful family of minute objects, only discernible by the microscope, and therefore unknown to the greater number even of those who interest themselves in botany. If this brief account should excite the curiosity of the lovers of nature to make deeper researches, the valuable work by Mr. Ralfs is recommended as the most useful to assist the student ; — much information has been derived from it for these pages.
Naviculacea. — I shall not again repeat the opinions of naturalists, or the disputes as to the nature of this branch of the family Bacillaria, but merely name the most interesting of the genera. Navicula is so called from its shape, all
NAVICULA.
71
the individuals being more or less in the form of a little boat, — and their quiet gliding motion increases the resemblance. The bright colours, or delicate transparent appearance of the lorica, make these little objects also very attractive ; and I have watched a number of them moving
o
in different directions with great pleasure, for their pace is so slow and gentle that all their habits may be noted. They appear to me to have decidedly a will of their own, and to avoid dangers or obstacles in their path, just as many of those animalcules do which are decidedly con- sidered as belononna to the animal kino;dom : and
O O O '
yet, as Dr. Meyen says they are by no means so free and active as the spores of the Algae, we are again puzzled. When watched with attention,
72 DROPS OF WATER.
they are found to glide slowly along at the bottom of the water, in a straight line, though oc- casionally a little slightly zigzag, as if to avoid the roughness of the glass ; then, when anything obstructs their path, they do not go round it, but immediately turn back on almost the same track, without turning the body, and this motion I have seen a specimen keep up for some time : a little tap on the glass will arrest their progress, and then they immediately reverse their motion. When, however, they meet with a substance which may afford them food, they stop, and either glide under or about it. They appear to have cilia at the sides, for I have often observed small sub- stances propelled along the body of the creature, and even running backwards and forwards several
NAVICULA. 73
times, as if the Namcula might be extracting food from it. I do not know a prettier sight for the observer, than a drop of water containing several of these curious little creatures of dif- ferent colours and shapes, gliding in various di- rections, and all actively engaged in their pur- suits. Ehrenberg describes about forty species, some found in salt water, some in fresh, and others fossil. They are seen single, and in pairs, but never in chains, or bands, like the rest of this division of the family. They are generally broader in the middle than at the ends : some have the two ends very sharp, others are more blunt, and one or two are more round than long ; a few have the ends curved different ways. Some are green, some brown or red, and others almost
H
74 DROPS OF WATETl.
transparent ; a few, also, are of a golden yellow. N. viridis (Drop I. fig. 14), N. amp/iisbtena- (fig. 15), and N. acus (fig. 16), are frequently seen.
The genus Bacittaria, from which the family derives its name, is composed of bodies of sin- gular construction. They seem originally to form connected lines, but, when mature, separate gene- rally only in part, forming zigzag chains : in this state they move slightly, and one marine species, B.paradoxa, when separated from its compa- nions, moves quickly like a Navicula. B. vulgaris (Drop I. fig. 17) is by many botanists looked upon as a vegetable, and named Diatoma floccu- losum : it is found both in fresh and salt water, and has a straight lorica three or four times as long as broad ; and when seen sideways it is in
FRA GIL ARIA. 75
the form of a spindle. B. cuneata (Drop I. fig. 18) is of wonderful construction — each in- dividual is wedge-shaped, and they still preserve the straight ribbon or chain-like form, by being- placed alternately the broad and narrow end together. These chains of the Bacittaria are free and floating ; as well as those of the next genus, Fragilaria, specimens of which are frequently seen to rise in the water, and turn round ; the individuals also, when separated, move forward gently. They may be distinguished from Na- vicida by being square at the ends, instead of pointed, and having two openings instead of one. In F. yrandis there are as many as thirty indi- viduals found linked together. F. rhabdosoma (Drop I. fig. 19) is very slender, and the bands
76 DROPS OF WATER.
drop to pieces very easily, and then the individuals creep about. The last genus of this division is Meridian, the separate individuals of which are wedge-shaped, but, unlike the Bacittaria cimeata mentioned above, they are arranged with all the small ends placed together, so that the band is not straight, but forms a spiral, if many are linked together; if there are but few, then a circle, or part of a circle, may be formed : M. vernale is the species usually seen. How mar- vellous are all these variations, when we consider the minute size of the objects !
The next section of the Bacittaria family is called Echinellea, and the genera are distin- guished from those of the other divisions, by being attached at one extremity to weeds, &c.
ECHINELLEA.
77
They may be seen of various forms, some single, others in groups ; some long and narrow, others wedge-shaped, and occasionally they grow one on the other. The individuals of one genus,
4
Gomphonema, form quite a little tree : each one is wedge-shaped, and at certain periods becomes detached, and creeps about, but it is not known whether it forms another stalk ; it is found attached to Lemna. Those of the genus EcMnetta form a cluster like a fan, and this is caused by the body dividing, but not the stalk, so that the individuals, being wedge-shaped, as they lie side by side, have a fan-like form. These are prin- cipally found in the sea, attached to sea-weeds and mollusca ; but two are found in fresh water. The fourth section consists of curious little
— -
78 DROPS OF WATER.
bodies, found principally in the sea, and too com- plicated to admit of description here ; but I must mention the genus Acineta, which has been added to the Bacillarice. It may be frequently noticed on the stalks of Lemna, and, being extremely pretty, shall be described. The body is affixed by a short stalk, is small, and round or bell-shaped, with numerous rays project- ing from it in various directions, each appear- ing to have a slight knob at the end ; these rays do not vibrate, but are said to be retractile. This I have not observed, for I never could trace movement in any part of this singular little being. It is nearly transparent, very small, and may be almost compared to a pin-cushion with pins in it ready for use, as the knobbed rays
ACINETA. 79
are of some length. In Acineta mystadna these rays are arranged in two bundles ; in A. tuberosa they are fewer in number. This little object shows the amusing variety of forms found in this minute portion of the creation ; and though the specimens seen in this drop of water are some of them of an uncertain character, they have yet considerable beauty and interest, and will not fail to reward the student who diligently searches for them.
DROP II.
IT has been remarked before, that the class Polygastrica derives its name from the globular vessels, seen through the transparent body of the animalcule, being supposed to be numerous di- gestive sacs.* In forty-eight species, eyes are perceptible, and the colour is red, with the ex- ception of one species, in which it is black. They have no feet, but their locomotive organs con- sist of vibratory cilia, which are in constant rapid
* The name is from two Greek words, signifying many stomachs.
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POLYGASTRICA. 81
motion, and by which they move in various ways, some gliding slowly, others rapidly, some again darting from place to place, and many having a rolling motion : indeed, their modes of progres- sion are almost as various as their forms. The methods of reproduction are principally three : — by eggs, which is the most common ; by self- division of the body ; and by the growth of buds, or gemmules, upon the parent. They increase at a most rapid rate, by each of these methods. I have watched the self-division frequently, and more particularly in the Vorticella convattaria, as that interesting animalcule is attached to weeds, so that its movements can be noted with great certainty. I shall describe the process when I more particularly mention that species. There
82
DROPS OF WATER.
are as many genera loricated as illoricated in this class. The Polygastrica are found in all parts of the world, both in fresh and in salt water.
The first family into which this class is divided is named Monadina, containing creatures of the most minute forms, and only interesting to the unscientific observer on that account; most of the individuals requiring very patient investigation, and high magnifying powers, before their move- ments and habits can be sufficiently understood to be minutely described. It has been discovered, however, that some of the genera possess eyes, and most of them cilia ; some only have a proboscis, and others again a tail ; none are enclosed in a lorica, and they increase by self- division into two or four parts, each becoming a perfect individual.
MONAS. UVELLA. 83
The genus Monas is represented in Drop II. by the species M. crepusculum (fig. 1), and is curious as being the smallest of known living beings. It feeds on decaying substances, and may be ob- served in considerable numbers, as a minute co- lourless speck, moving very rapidly, by the aid of a proboscis, and enjoying its transitory life in the society of its kind. Another species is of a deep red, and abounds in salt-marshes on the shores of the Mediterranean, to which it imparts a red co- lour. The M. crepuscalum cannot be seen without the aid of a glass magnifying 300 diameters.
The individuals of the genus Uvetta cluster together so as to form a mass like a mulberry. The species U. glaucoma is found in stagnant water. Ehrenberg was able to see, within the
84 DROPS OF WATER.
body of this minute creature, some green Monads which it had eaten, and by which it was proved not to be herbivorous. With a magnifying power of 800, eggs may be discerned. The genus Polt/toma abounds in water where animal matter is found. It has a double whip-shaped pro- boscis ; as the body increases in size, it has a wrinkled appearance, and at last self-divides into numerous individuals. Polytoma uvella is the only species : it is colourless and of an oblong form. Microglena is characterized as being the first to possess an eye — in other respects it re- sembles the Monad: it is found amongst slimy water-plants. A great portion of the green matter found on stagnant water is formed by in- dividuals of the genus Glenomorum ; they cluster
DOXOCO'CCUS. 85
occasionally, and possess a single red eye, and a double hair-like proboscis. G. tingens is oblong, of a beautiful green colour, and the proboscis is only half the length of its body. Doxococcus niber (Drop II. fig. 2) is a pretty lively little animal- cule, having a peculiar rolling motion ; of globu- lar form, and possessing neither tail nor eye; the colour is a brownish-red; D.pulmsculus is green ; and D. inequalis, irregularly round, trans- parent, and covered with green spots. These interesting little creatures will be readily distin- guished by their globular, form, bright colours, and singular motion, and add greatly to the beauty of the animated scene, which they often diversify. Occasionally they are found in consi- derable numbers, and then they appear to keep
86 DROPS OF WATER,.
up a merry dance amongst themselves, advancing and retreating, or gliding past each other with the most graceful movements. These are the most interesting genera of the family Monadina.
The family Cryptomonadina is distinguished by the individuals having a lorica, or shell, which in some is found to be indestructible by fire. It is either of a box or pitcher shape, and the animals sometimes have more than one proboscis.
The first genus, Oryptomonas, has some of the individuals green, others brown, and they may be known from the genus Doxococcus by observing that when the little creature is stopped in its rotatory motion by anything in its path, it leaps back suddenly. The individuals of the genus Prorocentrum are only found in the sea, and help
PROROCENTRUM. 87
to form the luminous appearance which is so fre- quently observed in the ocean. How marvellous that these little atoms, which require a magnify- ing power of 300, to be discerned, should produce this extraordinary light ! The lorica of the only species, P. micans, is pointed at the extremity, oval in shape, and compressed. The creature has no eye, but a proboscis, and cells can be seen in the interior of the body. It is of a yellowish waxy colour, similar to all the luminous Infusoria. Layenella eucldora has a lorica shaped like a bottle with a neck, and is of a beautiful green colour, but quite clear, and having a bright red eye. It is found in fresh water, with Conferva. Cryptoglena conica has a shield-like lorica, which folds inwardly at the sides, two proboscides, and
88 DROPS OF WATER.
an eye, and is of a bright green colour : it moves briskly, but springs back when obstructed. Tra- chelomonas volvocina (Drop II. fig. 3) is distin- guished by the lorica being spherical, and the proboscis very long and slender ; it is green or brown, but has a red ring on the circumference, which is seen whichever way it turns. Another, T. cylindrica, is of a beautiful green, with a purple circle and red eye.
The family Volvocina contains many very wonderful genera and species, equalled by none among these minute creatures. They are of a compound form, and live as it were in masses. This is caused by their method of self- division, which takes place, not by the body simply dividing into two, but into many parts, and each
PANDGR1NA. 89
of these parts seeming to form a perfect individual though joined to the rest, and all enclosed in a transparent envelope, which expands in size as the individuals approach maturity, and at last open- ing sets them all at liberty. This marvellous structure will be described under each genus, as they differ in form and construction.
The first genus, Gyyes, consists of very inactive creatures : very slight motion of the body only has been perceived, and they are, therefore, not so in- teresting as many others. The lorica is trans- parent, and the enclosed parts of a green colour.
The genus Pandorina is one of the most beautiful for observation by the microscopist. The transparent globular body encloses nume- rous rather dark green animalcules, each pro-
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90 DROPS OF WATER.
vided with a proboscis about twice the length of the body, protruding from the circumference of the globe, and busily engaged in moving the mass, and at the same time gaining food. The whole has much the appearance of a mulberry, whence the name of the English species, P. morum (Drop II. fig. 4), which is found amongst Conferva and Lemna. The regular rolling motion of this beautiful creature adds greatly to the delight of the spectator : this movement is not very rapid, so that it can be watched with ease. I once witnessed the disruption of the transparent case, and the escape of the numerous individuals : some of these had already the wrinkled appearance produced by the preparation for self-division. The globe, as I watched it, seemed to have lost its
GONIUM. 91
rigidity, and each individual was busily engaged in working its way out. I was first attracted by seeing the mass lying without motion, except that the green bodies within were moving rapidly, and by degrees each made its escape after some exertion, and swam away. It was a curious and interesting sight.
Though not surpassing the last in beauty, the genus Gonium is highly interesting, from its sur- prising form and construction. It is compound, and consists of sixteen individuals, each of a round form, having two proboscides, and six cords or tubes which connect it with those sur- rounding it ; the lorica is transparent, and the sixteen individuals are arranged in regular order, four in the centre and three on each side, re-
92 DROPS OF WATER.
sembling " the jewels in the breast-plate of the Jewish high priest.'3 The colour is bright green, so that both form and colour contribute to the beauty of the whole. The four central indivi- duals are generally larger than their external com- panions, and sometimes the clusters appear irre- gular, from some of the individuals having arrived at maturity, and become separated from the rest. If they are all of the same size, the cluster is seen to divide into four, each having four of the ani- malcules, and these again form fresh clusters like the original. I have two or three times observed that one of the individuals, before disconnecting itself from the rest, had divided into sixteen distinct bodies, forming a perfect compound mass, though the size was extremely minute.
GONIUM. 93
When swimming gently in the water, they occa-
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sionally turn on the edge, when it will be clearly seen that the individuals are arranged on a plane. This structure is highly wonderful, and is a proof of the extraordinary variety displayed in the works of nature. The species I have described, G.pecto- rale (Drop II. fig. 5), is found in clear water both salt and fresh : it is abundant in some waters both in spring and autumn ; — in water procured in October I have seen them swarm in great num- bers, and of all sizes. It is a beautiful sight to watch the quick movement of perhaps a dozen specimens at once in the field of the microscope. There are four other species differing slightly from the above, but one, G. glamum, has as many as sixty-four animalcules within its lorica.
94 DROPS OF WATER.
The genus Syncrypta is distinguished by having two loricas, one small one to each indivi- dual, and the other common to the whole cluster, enclosing them in its transparent folds. The long proboscis of each protrudes from the envelope, and gives the globe the appearance of being covered with hairs ; neither an eye nor tail has been perceived. There is one species only, 8. volvox : the shape of the individuals is oval, and of a green colour, with whitish rays in the centre, forming a pretty berry-like cluster when united.
The beautiful creatures composing the genus Synura are met with in clear waters containing Lemna, often in prodigious numbers, so that the field of the microscope will exhibit six or eight at once, all rolling about with the greatest ease and
SYNURA. 95
apparent enjoyment. Now and then they stop at a portion of decaying vegetation, and appear to be taking a slight repast, but as the mass forms a ball, how each individual comes equally into contact with the food is difficult to deter- mine ; it is probable, however, that the principal part of their sustenance is floating in the water, and therefore they procure it even when moving. The whole cluster seems to be moved as with one mind, for I have watched them repeatedly, and
thev move and turn as if all was under the di-
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rection of one individual, and yet they are a com- pound mass, formed of very many animalcules. Each has an oblong yellowish body with a tail, which is attached to the bottom of a cell in the general envelope. Into these compartments they
96 DROPS OF WATER.
can withdraw, and can also stretch themselves out to a considerable length when actively em- ployed. 8. uvella (Drop II. fig. 6), the only species, has the form of a mulberry, and I have watched the individuals when arrived at maturity separat- ing from each other, and at last leaving nothing but the shrivelled remains of their former habi- tation : it is a most interesting genus, and is fortunately not scarce. To show what astonish- ing powers these little creatures possess, I will relate a circumstance I witnessed. A large clus- ter had evidently been injured by pressure, so that half of its members appeared to be mis- shapen and dead. The living end was actively employed in turning round, and for some time I could not comprehend what this action denoted;
UROGLENA. 97
but at last, to my surprise, I found it had twisted itself off from the rest, and it soon swam away, presenting the appearance of a perfect cluster. The mutilated part left behind remained quite still, though I watched it for some time, and I have no doubt the members were dead.
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Each animalcule of the cluster, in the genus Uroglena, has an oblong yellow body, an eye and a tail : by the latter it is fixed to its own par- ticular envelope, and it radiates from the centre. The common globe-like lorica, or mantle, covers them all, but the proboscis projects beyond, and gives the appearance of hairs in constant motion. U. volvox is the only species, and is found in turf-water.
The only species of the genus Eiidorina is
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98 DROPS OF WATER.
E. eleyans (Drop II. fig. 7), and it deserves its name, for there can scarcely be imagined a more elegant creature. It seems to have a property different from the other members of this family — that of casting off the globular lorica, and forming a new one ; probably it has not the power of ex- panding to suit the growth of the congregated animalcules within it ; self- division taking place whilst the clustered portion is retained. The in- dividuals have no tail, but possess a sparkling red eye, and a vibratory proboscis : the body is green, from about fifteen to fifty of these little creatures are assembled under the same transparent covering, presenting a most beautiful appearance. They are often in great numbers, but so exceed- ingly delicate, that it is difficult to preserve
CHLAMIDOMONAS. 99
them for any time ; Pritchard says, that " when- ever it is attempted to retain them in large quantities, the second day will generally exhibit a thick mass of dead ones at the bottom of the vessel. When a few only remain alive, if the water be poured away, and the creatures removed into a vessel of clear water, they will live for weeks.'3 They are most abundant in the spring of the year. A green matter is often observed on ponds and other places, which at a first glance might be taken for a minute weed in great quantities, but if examined with care, it will be found en- tirely formed of the animalcule belonging to the genus CJdamidomonas pulvisculus, so named from its forming a dust-like stratum on the surface. They are often in vast quantities, and when they
100 DROPS OF WATER.
die, the bodies float, and give the surface of the water a green coating. They are compound, like the rest of the family, but there are never more than eight individuals in the lorica. Each has a beautiful red eye, which is seen even after death, and a double proboscis, but no tail.
Spliterosira volvox is the only species of the next genus. It is distinguished by possessing a pale green globular body, an eye, and a single proboscis, but no tail. It divides in an irre- gular manner, within the large transparent globe which covers the whole ; for it is often found, that some of the young are simple, others already in clusters, and some oblong. They are found generally in clear water, or turf- water, and are often as large as those of
VOLVOX. 101
the next genus, from which they differ princi- pally by having a single proboscis.
The Volvox is one of the most lovely of these interesting atoms, and attains comparatively so large a size, that its construction is easily dis- cerned, and in the spring may be found in clear water in great numbers, having a rolling motion, slow and very graceful. The hollow transparent globe contains some hundreds of single animal- cules, attached to the inner surface, each of a small size and green colour, having a red eye and a doable proboscis, which they protrude through an opening in the lorica, so as to give its surface the appearance of being covered with moving hairs. The shell of each individual is in the form of a bell, and it is said they have the
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102 DROPS OF WATER.
power of leaving it when full grown, though they are attached to each other by six cords, or tubes. Besides these numerous minute creatures, the globe often contains many globes like itself, of a small size and green colour. Sometimes as many as eight may be observed. The species V. ylo- bator (Drop II. fig. 8) is the most common, and is found in the spring and summer in shallow pools of clear water : the largest globes measure 3^ of an inch, and the smallest about ^ ; Vol- vox aureus has the enclosed globes of a golden colour, and the individuals green ; and V. stel- latus, as the name implies, has the animalcules of an angular shape, and the young globes con- tained in the large one, are stellated also.
Very little is known of the organization of the
VIBRIONIA. 103
family Ftbrionia, for the minute beings which form it are very difficult to examine, on account of their small size, many of them being invisible to microscopes of low power. If it were not for the circumstance of their linking together, so as to form threads, they would escape our observation. Sometimes two or three individuals only, form the chain or thread, at others a greater number, and from this circumstance it is supposed that they are originally separate, and only join together for mutual support, or that it is caused by the imperfect method of self-division. One genus, Bacterium, has a tremulous motion, but looks like a very fine stiff thread : it requires a power of more than 500, to see the individuals of which it consists. The genus Vibrio is more
104 DROPS OF WATER.
flexible, and the chains move like a snake : I have seen vast numbers in water, in which a few leaves had been steeped. In another genus, Spi- rillum, the threads resemble a corkscrew, and have a brisk, lively motion ; they are found in stagnant water. Some other genera are too obscure to mention.
The family Asiasicea has the power of changing the form of the body at pleasure. The eye, in all the genera, is very conspicuous, excepting in the genus Astasia, in which the species have no eyes. A, licematodes (Drop II. fig. 9) contracts and dilates itself in a curious way ; it is first green, and afterwards becomes of a blood-red colour. Even these little creatures have been a cause of terror to the superstitious, for they in-
EUGLENA.
105
crease at an astonishing rate, and, assuming a blood-red colour, give a tinge to waters, for which the ignorant cannot account. It has a spindle-shaped body. A.pusilla occurs in my- riads, so as to form occasionally quite a stratum on the surface of the water : it has no colour. A. nivalis is found in snow in Switzerland.
Most of the species of the genus Euylena are beautiful objects, the bright colours rendering them very attractive. JEJ. sangmnea (Drop II. fig. 10) is of a spindle shape, the head rounded, tail short, proboscis long : the colour varies — some may be found quite green, which seem to be the young ones, others mixed red and green, and others quite red. E. viridis is green, except the head and tail — these are white,
106 DROPS OF WATER.
and the eye is red. I have seen this species in such numbers, that there appeared a perfect swarm, though the water was obtained as late in the year as October, their elegant form and bright colours rendering it a beautiful sight. E. pyrum is dark green, pear-shaped, and swims rather swiftly. E. pleuronectes is like a small green leaf with a short stalk : it is flat. E. lon- gicauda has the power of twisting its body into a spiral form, and is also somewhat leaf-shaped. This is an elegant animalcule, the form very curious, and the colour sparkling green ; the tail is as long as the body, and, though colourless, is very conspicuous. When two or three are moving gently near each other, they form a very pretty scene. E. acus has a slender body, with
COLACTUM. 107
a pointed tail ; the head and tail have no colour, but the body is bright green, and the eye bril- liant red ; it is a beautiful species, not only from its bright colours, but from the elegance of its form, and its mode of swimming; when sta- tionary, it frequently changes its shape. There are several other species, but those mentioned are the most common : I have found them all in pond-water.
A little creature, attaching itself to other bodies by a foot-stalk, and frequently found on Eotatoria and the crustaceous creatures allied to the water-flea, is called Colacium. I have seen it covering the stalks of the Vorticella con- vattaria, so as to give the whole the appearance of a minute branch of green leaves. The species
108 DROPS OF WATER.
C. vesiculosimi has a very short foot-stalk, the body bright green, and of an oval form ; currents are seen near the fore part of the body, when coloured particles are introduced into the water, so that there is, probably, a vibratory proboscis. C. stentorinum is more cylindrical in form.
The genus Distigma is formed of individuals which neither swim nor produce currents, but they creep at the bottom of water, and change their form in a curious manner : they appear to have delicate black eyes. D. tenax is the largest, and it contracts and dilates very visibly ; the colour is yellowish. D. viride has green granules within. Both are found amongst Lemna and Conferva.
The family Dinofiryonia differs from the last in
DINOBRYON. 109
having a lorica, which has the form of a little
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pitcher ; the body still retains the power of chang- ing its shape at will. One genus, Dinobryon, pos- sesses more beauty than many others among these interesting creatures. D. sertularia (Drop II. fig. 11) is more like the flowering spike of some grasses than anything else to which I can compare it, except, perhaps, a branch of coral : the little creature resembles the Euglena, mentioned before, but is of a pale yellow, and has the power of stretching itself out, and also assuming a globular form within its lorica. It has a red eye, and a long proboscis which assists not only in propel- ling itself through the water, but also the others to which it is attached. Each individual lorica seems to have sprouted from the one below, till
110 DROPS OF WATEIl.
at last there is formed quite a little spike, or shrub, of these delicate loricas, and the elegant inhabitant. It is so extremely transparent that it requires very nice adjustment of both in- strument and light, to see it well; — it is lost sight of by the smallest alteration of the focus, but, when fully seen, is an exquisite object. It is not attached, but moves slowly in the water, turning gently round. I have occa- sionally met with bog-water abounding in this delicate creature : the groups differ in size, some having only two or three collected together, others formed of a dozen, and then nothing can exceed the beauty of this compound mass. It is found principally in the spring.
The family Amcebaa consists of one genus,
AMCEBA. Ill
Amoeba. This singular animalcule has neither foot, eye, nor proboscis ; it appears like a trans- parent bladder, and has the power of putting out at all parts of the body processes which help it to creep slowly — these it contracts and dilates continually, so that it is constantly chang- ing its form ; this renders all the species very interesting objects for the microscope. A. prin- ceps (Drop II. fig. 12) is of a pale yellow colour, and its manner of progression is very amusing to watch. It puts out a portion of its body which appears quite transparent for an instant, and then the granules with which the body is full, run forward into it and fill it ; at the same time other portions undergo the same extension, and thus it moves slowly along. The protruded parts
112 DROPS OF WATER.
of the body do not seem to be always the same, but to arise from any part at the will of this sin- gular creature. A. verrucosa is smaller, and with shorter and more blunt processes. A. diffluens has no colour, and A. radiosa expands its pro- cesses in the form of a star, though when at rest it looks like a lump of jelly.
The family Arcellina differs from the last in having a lorica of a pitcher- or dish-shape, and moves by the soft processes protruded beyond it. The first genus is Diffiugia, which has the pro- cesses cleft into several parts, and the body enclosed in an opake lorica. D. proteiformis (Drop II. fig. 13) is of a globular or oval form, the lorica encrusted with minute grains of sand : the transparent processes are often as many as ten in
ARCELLA. 113
number ; it is found amongst Conferva, as well as the next genus, Arcella, which differs in form, being flatter, and the surface not covered with sand. A. acideata has spines upon its surface, and a large opening. A. vulyaris has the lorica round, and covered with rows of minute granules, and A. dentata is of a hemispherical form, and has the margin dentated. The last genus of this family, Cyphidium, has only one dilated process ; the lorica is pitcher-shaped, with protuberances upon it, which give it a square form : the pro- cess by which it moves may be termed a foot, and resembles the body of the genus Amoeba. OypMdivm aureolum is the only species.
L3
DROP III.
THE objects contained in the drop under con- sideration are of a different character to those in the last. Many of them have very lively movements, others are attached, but at the same time full of life and motion. One family, the Vorticellina, will be found highly interesting, and, most of them being fixed to weeds, they are more easily examined than many others. Two small and insignificant families are ar- ranged before it in the classification. The family
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CYCLIDIUM. 115
Cyclidma contains animalcules having no lorica and no eyes ; bristles, or cilia, are the organs used in locomotion. The genus Cydidium has a compressed body, and the cilia are placed in a single circular row. C. glaucoma is abundant in the spring, and may be known by its oblong body, the ring of cilia, and its peculiar move- ment, which is generally quick ; but frequently the little creature stops, and then springs sud- denly to another spot, with a light, graceful mo- tion. The family Peridin&a possesses a lorica, and probably eyes, and the cilia are in the form of a crown. Some of the genera have a deli- cate proboscis, in addition to the cilia ; they are, however, insignificant in size, and I shall pass them over, to give more space to the next family.
116 DROPS OF WATER.
The individuals of the family Vorticellina form one of the most interesting groups. Some are free, others are attached either singly or many together, forming little tree-like masses, where each individual may be likened to a leaf : this is caused by their imperfect self- division. They have no lorica, but numerous cilia arranged in va- rious ways — in some genera they cover the body all over, and in others they merely surround the mouth, or form a wreath. Eyes have not been observed, but they have some quick mode of knowing when danger approaches, and shun it very rapidly. The mode of increase is by self- division, either by the body completely dividing into two separate individuals, and becoming per- fectly independent of each other, or by the body
STENTOR. 117
dividing, but the two remaining attached by a stalk ; they also increase by buds issuing from the sides of the parent body.
The first genus of this wonderful family is called Stentor-, the animalcules are free, in the form of a trumpet, and of considerable size, as they may be seen without a microscope, floating as specks in the water. I have found the black species so numerous in some waters as to give the appearance of a black powder having been spilled on the surface. All the species are active, lively creatures, and extremely amusing to watch. They adhere, when feeding, by the pointed ex- tremity of the body to a leaf or stalk, and stretch themselves into the form of a trumpet, expand- ing at the larger end where the mouth lies, and
118 DROPS OF WATER.
where a wreath of large cilia are in constant vi- bration, enabling them to draw within the body the food they require : this consists of Monads, and various little creatures ; and as most of the species are transparent, the digestive cells may be plainly seen filling gradually with these unfortu- nate little beings. Stentors increase by self-divi- sion longitudinally, and also by eggs. S. Mul- len is white, transparent, and large. S. Roeselii (Drop III. fig. 1) is equal in size, but rather more yellow in colour. They both contract, when swimming, into the form of an oblong ball, but when fixed, stretch out considerably ; when two or three are attached near each other, and all have their mouth-cilia at work, the current they form in the water is quite extraordinary,
TRICHODINA. 119
and very interesting : small cilia cover the whole of the body. S. polymorplim has green masses within, supposed to be eggs. S. iyneus is yellow, or rather red, and is smaller than the rest. 8. niger is very dark in colour, and does not stretch out to so complete a trumpet-shape as the rest : it swims rapidly, and is very abundant in the spring, making the surface of the water quite black in patches. 8. c&ruleus has the ova blue, which may be seen through its transparent body. The genus Trichodina has no cilia on the sur- face, but a wreath of them at one end of the conical body. Urocentrum has no cilia except a wreath. U. turbo has a transparent, three- sided body, and a short tail : it is found amongst Lemna and other weeds.
120 DROPS OF WATER.
The genus Vbrticella is one of the most in- teresting amongst the Infusoria. The species V. convattaria (Drop III. fig. 2) is the most common, has a bell-shaped body, is perfectly transparent, and attached by a flexible stalk of considerable length to weeds, &c., so that it can be watched with great ease ; and a more amusing sight cannot be met with, than a number of these beautiful beings grouped together, all busily engaged in procuring food by the aid of their cilia, which they keep in constant motion, thus producing a strong current in the water, and drawing into their mouths small atoms upon which they feed. When any object alarms them, they immediately contract the strong muscle, which, with a power of 250 diameters, may be
VORTICELLA. 121
seen within the stalk : this motion carries the body instantaneously to a considerable distance ; after a short time it uncoils again, and the ani- malcule renews its occupation. This stalk, which is about five times longer than its body, is a marvellous structure : — the muscle within, at the will of the animal, can contract into many coils, so suddenly that the eye cannot follow the motion, though the effect is seen by the removal of the body to a distance ; — the uncoiling is not so sudden, and much more graceful. Vorticella group themselves together in hundreds, when the scene is very animated, first one and then another contracting ; and often the whole party recede at once, as if animated by the same will, then they expand again, and the same scene is
M
122 DROPS OF WATER.
displayed; the current in the water, formed by the group, causing numerous little ani- malcules and vegetable productions to whirl about in a curious way. This current may be observed more clearly still, if a small portion of carmine or indigo be placed in the water, at the same time the animalcules will be found to eat it in vast quantities, the stomach cells be- coming coloured either red or blue. They in- crease rapidly by three different methods. Though the act of depositing eggs has not been perceived, still young ones appear in vast numbers attached near the old ones to the same substance, and gradually increasing in size. A full-grown one will frequently be seen to have a double appearance, and if this is watched, a
VORTICELLA. 123
fissure will soon be perceived — two bells will be formed, and in time one will twist itself off, and, swimming freely about for a period, at last fix itself, and form a stalk. One extraordinary cir- cumstance has been witnessed by those who have watched minutely — that the lower portion of what may be called the new being, and which was attached to the stalk, now becomes the mouth, and is surrounded with cilia, whilst the upper part closes and produces the stalk. I have frequently observed a circle of cilia in ac- tive motion on the lower part of the newly- formed bell, even before it had left its parent, but have never been so fortunate as to observe what follows. When this newly-formed creature is swimming about, it might be, and has been, taken
124 DROPS OF WATER.
for a new genus. Besides tins extraordinary method of increase, buds have been perceived on the sides of the bells, which gradually increase in size, and form new individuals. By these various means their numbers augment astonish- ingly, and this increase may be watched, if a stalk of duckweed or other substance to which a few are attached, be put by itself in a small vessel of water, and examined by the microscope every day. I have often selected a small group, and keeping it in a vessel alone, have observed them increase to several hundreds in the course of a short time. They fall from their stalks and die, if deprived of air, for I have more than once kept a number under a glass cover, for twenty-four hours/ and found half lying dead in
CARCHESIUM. 125
heaps at the bottom, and in double that time all had perished. This species is found principally on duckweed. V. campanula is larger than V. convallaria, and rather brown in colour : it has a bell-shaped body, but truncated in front. The single animalcules may be discerned without a glass ; and a mass of them appears like a bluish matter attached to water-plants. There are several other species, all differing slightly from those mentioned, but having the same gene- ral appearance and habits.
The next genus is Carc/tesium, and it differs from the last in its imperfect mode of self- division. There is one main stalk, which has the power of being contracted in coils, like that of the last genus ; but it is branched, and each
M 3
126 DROPS OF WATER.
division bears a bell. C. polypinum (Drop III. fig. 3) has a bell-shaped body of a white colour, and in size is equal to the Vorticella convallaria. These groups are particularly beautiful, and the actions very amusing to watch. Each individual bell has the power of contracting slightly, and drawing in its cilia, but the long stalk is only common to the whole number; how they agree to contract that, it is difficult to say, and yet they are constantly repeating this movement, and again stretching themselves out in the most elegant manner.
The genus Epistylis has a stiff, inflexible, hollow stalk, which is generally branched, like the last genus. E. plicatilis has a forked stern, the bell-shaped body has rather a yellow
EPISTYLIS. 127
cast, and, when contracted, has a folded ap- pearance. E. anastatica has an oval-shaped body, and does not form folds when contracted : it is often found on the shells of small mollusca. E. digitalis is small, but much branched, and is often abundant on the body of the Cyclops qua- dricornis, where it appears to be indifferent to the rapid movement of that active creature, whose passage through the water one would suppose must destroy the life of so delicate a being. E. grandis has not an erect stalk, but it is often of great length, even as much as several feet : it looks like blue slinie to the naked eye. E. nutans has the body drooping when the cilia contract, though it is upright when they are expanded. It is curious to see this little crea-
128 DROPS OF WATER.
ture suddenly fall into a drooping posture when danger approaches, as if its minute stalk had a joint near where it is attached to the main stem ; after the lapse of a moment, it again rises, and renews its search for food. E.parasitica is small and solitary. There are several other species.
The species of the genus Opercularia have a stiff stalk, and much branched ; but the bells, or little bodies, are of different shapes and sizes. The genus ZootJiamnium has a flexible stalk, and the bodies of different forms. Z. arbuscula is much divided, forming objects like beautiful little trees, or plumes of feathers. Most of these curious genera of the family Vorticellina may be seen with ease by the aid of a good microscope, and will amply reward the patient investigator by the
OPHRYDINA. 129
pleasure derivable from watching the habits and peculiarities of these extraordinary and beautiful little beings.
In the next family, Oplirydina, I shall only mention two genera — Vaginicola and Cothurnia. Vagmicola crystallina (Drop III. fig. 4) has a transparent, crystalline, pitcher- shaped lorica, fixed to the stalks of duckweed ; the body is bright green, from the granules with which it is filled, and often appears double : it expands slowly as if afraid, and protruding from its lorica, it then unfolds its cilia for a short time, but again suddenly retires. V. decumbens has the lorica flat on the stalk or leaf — not erect, like the last. Cothurnia imberbis (Drop III. fig. 5) has the transparent lorica round at the bottom,
130 DROPS OF WATER.
and supported by a short stiff stalk : the body is yellow; — often attached in numbers to the Cyclops quadricornis.
We now come to a part of the classification where the families and genera are exceedingly difficult to describe ; I shall only, therefore, mention a few of the most striking, leaving the student to refer to works of greater science when the excited curiosity is anxious to be satisfied. The little creatures are of higher organization than those described before, and many of them much larger. They are all more or less bladder- shaped, the body generally covered with delicate cilia, some possessing loricas, and others none; some, bristle-like appendages, and a few having long necks ; they either swim about or creep on
TRACHELOCERCA. 131
plants. One genus is named the swan-neck animalcule, from the extreme length of that part in some of the species ; indeed, they may be called all neck, for the body is small com- paratively, and they are more frequently seen with the neck alone projecting from the edge of a leaf. Trachelocerca olor (Drop III. fig. 6) has a spindle-shaped body, with a very long flexible neck, dilated at the end, where the mouth is situated. The animal creeps at the bottom of the water, or on the leaves, and is constantly moving its graceful neck in all directions amongst the weeds : when two or three are feeding close together, it is curious to watch the actions of this flexible member.
Another singular creature, somewhat similar
132 DROPS OF WATER.
in form to the last, though differing in many es- sential particulars, is the Trachelius anas : it has what at first sight might be taken for a neck, but the mouth not being placed at the end, it cannot be so considered. The mouth is at the base of this long appendage, and may be seen occasionally whilst the long process is waving about ; this, and the cilia on the body, are the organs by which it moves.
Bursaria truncatella (Drop III. fig. 7) is another marvellous being, large, and easily dis- cernible by the naked eye ; found in water where there are decayed beech-leaves. It is oval in form, truncated in front, and having a simple row of cilia there, but the body is entirely covered with small ones disposed in rows. It
BURSARIA. 133
glides about in a quiet manner, between the portions of vegetable matter, and appears to have the power of compressing its body to suit the size of the passage. The internal cells are very transparent, and I have seen Rotifers and other small animalcules lying within, as if only just swallowed. Having procured some water which contained a large number of these crea- tures, I had an opportunity of making observa- tions about their death, which I do not see men- tioned by naturalists :- -whilst watching a very fine one, I perceived that a part of its body seemed to be separating from it, particularly the contents of the internal cells ; this continued for some time, until at last the whole body had dispersed, and was lying on the surface of the
N
134 DROPS OF AVATER.
water in minute portions; but the most mar- vellous part of the proceeding was, that the cilia continued to vibrate the whole time, not only as long as the body was partially hanging to- gether, but each little portion, as it floated away from the larger mass of the body, had consider- able motion in it from the action of the cilia, and this continued for full five minutes, or perhaps more, after each portion had separated from the main body. The animalcule itself remained turning slowly round during the process ; and the motion only ceased when all was dis- persed. I witnessed this curious fact many times before I discovered what may be considered the reason of this extraordinary dispersion : I believe it to have been caused by the evaporation
BURS ARIA. 135
of the water, as its death always seemed to take place after the drop had been under the micro- scope a certain time, and though there was still sufficient water remaining for the body to move within it, with some freedom, there might not be enough for its comfort and life. I caused the death of many specimens, before this idea occurred to me, and I have not met with any- thing similar to it, except once, in the case of a Stentor, which I saw disperse in the same extra- ordinary way. That the bodies of these little creatures should be dissipated in the water after death is not surprising, but that they should commence breaking up during life, — at least, that the cilia should retain so much muscular power when separated from the body, — is won-
136 DROPS OF WATER.
derful. The more we watch these little creatures, the more we find to admire and interest us.
I must mention the Paramecium aurelia (Drop III. fig. 8), because it is found sometimes so very abundant in stagnant water. I have seen it in such numbers in one drop, that the little creatures were almost close together, and yet all gliding about in seeming enjoyment : they were in water in which I had steeped a few leaves for some weeks. They have an oval cylindrical body, and have short cilia placed in long lines, those near the mouth rather longer. The di- gestive cells are very numerous ; and it is stated that these little creatures have the sense of taste, for if a mixture of carmine and indigo be put into the water, some will take only one substance,
EUPLOTES. 13?
and some the other — and this can be seen by the colour in the stomach-cells.
The last genus I shall mention in the class Polygastrica is Euplotes, a genus with which ob- servers soon become familiar, not only from the beauty of the species, but from the peculiar move- ment of these little creatures. They are of an oval form, very transparent, and brightly coloured with spots of green and red ; they have cilia, and are furnished also with what are called setae, and styles ; these are hair-like appendages variously situated, which, by their quick mo- tions, enable the animalcule to move most rapidly through the water ; they also dart back sud- denly, and, turning round, again advance to the place where they were gaining food : this back-
N 3
138 DROPS OF WATER.
ward and forward motion is frequently repeated, and occasions them to be easily recognized. They make a powerful current with the cilia near the mouth. Euplotes char on (Drop III. fig. 9) is, I think, the most common, and is found in infusions. E. patella is larger, more round in form, and abounds most where duck- weed is growing. There are several species of this interesting genus found in sea-water.
- -
:
s . r
. : . . •
. n
'
. -. < i u s
• • -
DROP IV.
THE animalcules comprised under the class Ro- tatoria are of a higher organization than those already mentioned ; the body is of a more definite form (not changing its shape, or dividing spontaneously, as is the case with many of the Polyffastrica), having but one digestive cell, in the form of a tubular alimentary canal, being pro- vided with a rotatory organ, and in general a single foot, or process, by which it clings to sub- stances in the water. Of the cilia, and their
140 DROPS OF WATER.
wonderful construction, I have spoken in the in- troductory chapter ; — by their means a whirlpool is caused in the water, smaller creatures are
drawn into it, and swallowed bv the mouth : this
i/
apparatus forms, also, their means of locomotion, and in many genera the swimming is very rapid. These delicate cilia can be withdrawn at pleasure, and covered securely by the rest of the body. The gullet contains a set of sharp teeth, which grind down the food very rapidly, and which may
be seen constantlv in action whilst the animalcule
i/
is feeding. The foot — or tail, as it is sometimes termed — is in many genera of very wonderful con- struction ; it is formed so as to enable the little creature to make it long or short at pleasure, by one part sliding within another, on the same con-
ROTATO1UA. 141
struction as the tube of a telescope. It is very interesting to watch this exquisite mechanism, and to observe how wonderfully all the parts are adapted to each other. The Actinurus Neptunius shows this formation in the greatest perfection. Other genera have a disc at the extremity, like the leech, by which they hold very tightly ; and many have one or more toe-like divisions.
The Rotatoria are reproduced by eggs, either hatched within the parent body before exclusion, or fixed to weeds and other objects floating in the water. Some few genera attach the eggs to their bodies, and carry them about for some time, appearing not to be in the least inconvenienced. The number of eyes varies in the different genera : they are generally red. As the Rotatoria are
142 DEOPS OF WATER.
large, comparatively speaking, a glass magnifying 250 diameters is quite sufficient to see them with perfect ease. I shall only describe a few of the most common genera, referring the student to Ehrenberg's or Pritchard's excellent works, where each species is minutely described, and as ably illustrated as means will allow.
One of the first genera of the Rotatoria, though it will not be the first to attract the atten- tion, is a creature somewhat resembling a long narrow fish with a forked tail. The IchtJtydium podura has a transparent, colourless body, long, and constricted so as to form a head ; it swims rapidly, but is generally seen creeping : the tail is formed of two parts, like a pair of pincers.
The next genus, Chtetonotus, is more common,
FLOSCULARIA. 143
and peculiar, having its body clothed with hairs, the form also resembling in some degree that of a caterpillar : it is generally seen creep- ing on the stalks of duckweed, and occasionally swimming with considerable ease. C. larus is the most plentiful species, and particularly abundant in muddy water.
The genus Floscularia, though consisting of species always attached to water-plants, and there- fore less lively than most of the Rotatoria, is very beautiful, and highly interesting. The indivi- duals each dwell in a transparent case, which is affixed to plants, and the body is attached by a slender foot to the base, having the power of ex- panding or contracting itself at pleasure. When contracted, it is shorter than the cell, but, if
144 DROPS OF WATER.
watched, will be found gradually to expand, and to stretch itself far beyond the edge of the case, and then to unfold its curious, rotatory organ, which is divided into six lobes, each provided with many cilia. A current is then observed in the water, though the cilia are not seen to move ; small objects are drawn into the mouth very rapidly, and swallowed, to be ground down by the chewing apparatus, which may be observed constantly at work. When danger approaches, the creature contracts suddenly, and is safe within the case in an instant ; this protective case is so exceedingly transparent, that even the brightest light will fail to render it visible, unless it is partially covered with loose matter which has been drifted to it by the water; or it may
FLOSCULARIA. 145
be seen, when this is not the case, by colouring the water with carmine. The presence of eggs, also, near the body of the parent, shows that there is a case, though it may not be visible to the eye. F. ornata (Drop IV. fig. 1) is the most com- mon species: it has longer cilia than F.probosci- dea, but no proboscis. The mode of increase is by eggs, which are deposited within the case, and are of considerable size, and of an oval form : I have seen four or five within the transparent covering of the old one, and once witnessed the young animalcule hatching. The two red eyes are very distinctly visible when the little creature is nearly ready to burst the shell ; and on one occasion, observing that these eyes were more conspicuous than I had previously seen them, I watched very
o
146 DROPS OF WATER.
attentively, and at last had the pleasure of seeing the young one escape first into the case of the parent, and from thence into the water, where, though so small, it was conspicuous from the bright red eyes ; but it swam so rapidly, that I could with difficulty follow it ; and at last it was lost among the surrounding weeds, which seemed to form a wide world for the little creature. After a short life of freedom it attaches itself like its parent, and forms a case. In some waters these interesting and beautiful creatures abound. I have counted between thirty and forty speci- mens on one stalk of duckweed, in all stages of growth : — those of middle age are bright and clear, the case nearly invisible and containing no eggs, the body slim, and very elegant in
STEPHANOCEROS. 147
form ; the old ones have the case large, covered with extraneous matter, and with as many as five eggs clearly seen within it, — the body larger, of a more plump form, much coloured, and capable of stretching out, when feeding, to a very considerable length.
There are other genera of attached Rotatoria,
which I will slightly describe, but that above
*
mentioned is the one most generally seen. Ste- pltanoceros Eichhornii is a very wonderful crea- ture, and of considerable size, but unfortunately very rare. The case, is so transparent, that it is rarely seen unless the water is coloured with paint : it is larger than that of the Floscularia ornata, and Dr. Mantell describes it as " attached like a collar round the body at the upper margin,
148
DROPS OF WATER.
near the base of the rotators ; so that its border becomes inflected when the animal shrinks down towards the bottom of the case/3 The ro- tators here spoken of are five deep lobes of the rotatory organ, each having fifteen circular rows of cilia one above the other, up to the points ; these lobes, or arms, the animal spreads out when it emerges from its case, and occasionally uses them as a " prehensile instrument." They are extremely beautiful and curious, and in a con- stant state of activity, frequently shrinking into the case, and again emerging and displaying the beautiful form of the lobes. Dr. Mantell once saw one he was watching, capture a Stentor by the aid of these arms, but he does not say whether it was eaten. They seem principally to
LIMNIAS. 149
feed on Monads, and other small creatures. The eggs are retained within the case till they are hatched. The Stephanoceros has one eye, which is very conspicuous in the young state.
The Limnias has only two lobes to its rota- tory organ, and the case, though at first white, becomes of a brown colour, and is often covered with other substances which adhere to it. The rotatory organ of the Limnias ceratopliylli (Drop IV. fig. 2) has a singular appearance when the creature is feeding ; — the cilia surrounding the lobes are very short, and, when vibrating very rapidly, have the appearance of a moving band of light round the edge, which is very deceptive to the eye, and the mind can scarcely conceive that the effect is produced by so simple a cause as small
o3
150 DROPS OF WATER.
vibratory cilia ; below this apparatus are seen the grinding jaws in motion. The animal frequently bends its body, first to one side, and then to the other, as if it were looking over its dark case for prey ; and at that time are seen several processes, which form part of the body. The Melicerta, another genus of stationary Rotatoria, has four lobes : the case has a granulated appearance, and is of a brownish-red colour.
Of the free genera of this class, a few species, more highly interesting and more common than the rest, can be alone described.
Microcodon cto^(Drop IV. fig. 3) is a beautiful little animalcule, being in shape like a bell, with a long undivided foot, which it has the power of bending at right angles to its body ; the rota-
NOTOMMATA. 151
tory organs are shaped like the figure eight, and have bundles of bristles projecting beyond ; it seems to have a small red eye. It is a lively little creature, and extremely difficult to observe with accuracy.
Notommata longiseta (Drop IV. fig 4) is of a very curious construction and appearance, and easily known by its long double tail, which is often more than three times the length of its body ; the two portions are needle-shaped, one longer than the other, and slightly curved : the body is small and cylindrical, the rotatory organs nu- merous, and not conspicuous. It is an active creature, and has the power of leaping, or at least changing its position suddenly, for I never ob- served that this action gave it much onward
152 DROPS OF WATER.
movement; it seems more frequently to turn round only, and is probably assisted in this action by the long stiff forked tail, or foot. It appears to feed on other species of Rotatoria, as well as the smaller Polygastrica.
Synchceta pectinata (Drop IV. fig. 5) is a beautiful animalcule, but very difficult to watch, from its quick motions, and the transparency of its body. It occasionally, however, fixes its short forked tail, and then twirls round rapidly for some time, vibrating its numerous rotatory organs, and drawing towards it many objects in the water. Between the clusters of ciliated organs, are strong bristles, which are easily seen when the creature is thus comparatively quiet. The body is short, tapering towards the short
SCABIDIUM.
153
pointed tail, but very broad at the head, which has two shoulder-like appendages, giving it a peculiar look, and rendering it, with other circum- stances, easily distinguished. It has a large red eye. Altogether, this is an interesting specimen, but from its liveliness rather tantalizing, for it may be followed for a considerable time before it remains sufficiently tranquil for any of its pecu- liarities to be noted. Another species, found in the Baltic, produces a phosphorescent light, observed by Dr. Michaelis.
Scandium longicaudum has a long foot, twice the length of the body, and seemingly jointed in the middle. It is divided at the extremity into two toes : with the aid of this curious ap- pendage, the animalcule has the power of leaping
154 DROPS OF WATER.
or springing very quickly, not to a great dis- tance, but changing its place, and half turning round at the same time. It has one eye, and a compound rotatory organ, armed with a hooked bristle ; the body is oblong. This is an interest- ing object, and found in the summer, though not very commonly.
Another leaping animalcule, the Polyarthra trigla (Drop IV. fig. 6), is of very singular con- struction. The body is almost square, and on each side are six strong narrow fins, or bristles, which enable it to swim quickly, or leap sud- denly. It carries its eggs attached to the outside of the body. The small poly gastric animalcule, the CoZacium, mentioned at page 107, is often found infesting both its body and fins, and yet
LEPADELLA. 155
its progress through the water does not seein to be impeded.
Eattulus lunaris (Drop IV. fig. 7) is one of the smallest of the Rotatoria, but often seen in turfy pools, and soon distinguished by its dimi- nutive size and curved body ; the foot is short, and curved also.
The genera mentioned from Notommata to Eattulus have no lorica.
The individuals of the next family are clothed with a lorica ; some of the genera are common, and interesting. Lepadella ovalis (Drop IV. fig. 8) is often seen in immense numbers in stagnant water, and is a pretty and lively animalcule, though said not to possess eyes ; it guides itself, however, with unerring precision,
156 DROPS OF WATER.
and, if deficient in sight, Las other senses of equal value. The lorica is flattened, and of an oval form ; the small foot divided at the end, and moving about in every direction. It ap- pears to fix the foot on some substance in the water, and then to move the body rapidly on every side, as if in search of prey; the small rotatory organs are in constant motion.
Mastigocerca carinata (Drop IV. fig. 9) is one of the most elegant of these interesting crea- tures : its oval body, with a crest on the back, seems to take a variety of shapes as it spins round in the water ; its long needle-like tail is straight when swimming in one direction, at others bent at right angles to the body whilst it is stopping to examine food. It does not swim so
EUCHLANIS.
157
rapidly as many others, and thus is more easily examined : its rotatory organ is small, and divided into four parts ; it has one eye, and the body is so transparent that the internal parts are easily seen, giving colour and seeming solidity to this otherwise fragile-looking creature. The crested and raised part of the lorica on the back, is very curious, but the use of it is doubtful; other genera have a lorica of similar construction.
Euclilams triquetra is of large size and sin- gular form, but is unfortunately rare, and only found in turf-water. The lorica is very trans- parent, and three-sided, the crest on the back, and the rather sharp flattened sides, forming, when seen endways, a perfect triangle t the tail is divided into two sharp points, and proceeds
158 DROPS OF WATER.
from the under side of the lorica, not from the end of the body. The rotatory organs are divided into several bundles.
Salpina mucronata (Drop IV. fig. 10) is com- mon, but not less interesting on that account. It is smaller than the last, but of sufficiently large size to render it easy to watch its move- ments. It is lively, but often attaches itself by its forked tail to weeds, for some time, when busy in procuring food ; indeed, it is, I think, particularly voracious, for I have watched a spe- cimen seemingly thus employed, for two hours at a time. In my opinion, this animalcule feeds on vegetable substances almost entirely, for I have frequently seen it clearing away the green pulp from the stalks of duckweed, and leaving
SALPINA. 159
transparent spots, which before were opake. The three-sided rather rough lorica is of very curious form ; the under side is flatly rounded, the back crested, the sides also project, and the space between is hollowed out ; at the end, where the head is placed, it has four points, or horns, and at the base only three, where the two-forked tail projects. It has a compound rotatory organ, which it withdraws completely into the lorica when alarmed. The red eye and toothed jaws are easily discerned, the latter moving very ra- pidly when the creature is feeding. The eggs are large, frequently found attached to weeds, and so transparent that the young are visible within ; these, when nearly arrived at maturity, produce a vibratory motion, easily seen. This animalcule
160 DROPS OE WATER.
is found principally among duckweed, and is pretty numerous in spring and summer.
Metopidia lepadella greatly resembles the genus Lepadella mentioned before, being flat, oval, and having a forked foot, but it has two red eyes. It is very transparent, particularly the sides ; is lively, and not uncommon.
The Slephanops lamellaris is a very pretty creature, and is easily known by its head having a kind of hood extended over it, which is trans- parent, and cannot be withdrawn within the lorica, but probably serves as a defence to the delicate cilia. Its swift movement renders it difficult to observe ; and before I had seen the little creature actually withdraw its cilia, I imagined the hood was an appearance only,
CALLIDINA. 161
caused by the rapid movement of the cilia and the swift motion through the water, but repeated observation undeceived me.
The individuals of the family next under con- sideration are not cased in a lorica, and are very peculiar, from the form being more or less spin- dle-shaped, and from their having the power of sliding some portions of the body within each other, like the tubes of a telesc6pe, so that it is either long or short at the will of the creature. This construction is very wonderful, when we consider the mechanism and muscular power required to effect it. Actinnrus Neptunius is the most striking example of this peculiarity. The genera are as follows :-
The Cattidina elegam is found in bog- water,
TIT
162 DRO£S OF WATER.
and in water in which oak-leaves or bark has been steeped. It is of an elegant spindle-form when stretched out, the rotatory organs small, the foot forked, and having also processes above ; the body is very transparent, and the jaws can be distinctly seen engaged in grinding down the food. At first sight it greatly resembles the fol- lowing genus, but the rotatory organs and want of eyes distinguish it.
Rotifer vulgaris (Drop IV. fig. 11). — This in- teresting animalcule was one of the earliest, dis- covered by the aid of the microscope. It was first described by Leeuwenhoek about 150 years ago, and has never since ceased to be a favourite with those possessing microscopes. It is easily obtained in spring and summer, being abundant
ROTIFER. 163
in most waters where decaying vegetables are found ; or a store of them may be kept in a jar by following a plan which has been mentioned to me by one interested in the subject. " Fill a three- or four-gallon jug with rain-water (not butt- water), which will serve for a year or two to keep a half-pint mug at the same level (with water from the jug). Into the mug put a few sage-leaves tied together, and when they are not to be obtained, in winter, a little bundle of hay about the size of the joint of a finger will answer as well. When the sage-leaves decay and sink, put in a fresh supply ; the Rotifer vulgaris will always be found at the surface near the sage- leaves ; and when dirt forms at the sides of the mug, if a small portion of it be taken up with
164 DROPS OF WATER.
the water, the animal will adhere to it by its tail, and display its wheels. I kept them in the same mug for ten years.33 This transparent creature is fusiform, or spindle-shaped, tapering gra- dually to the foot when expanded, but when "contracted it is thick, and the head and tail dis- appear within the body ; the joints are not visible when the creature is expanded, but when con- tracting, their curious conformation is seen, and the method of sliding one within the other clearly observable. The foot, or tail, has six processes, placed two and two at the joints. The upper ex- tremity of the body has a pair of wheels, distinct from each other, and of very wonderful construc- tion ; when the wreaths of cilia which form them are in full motion, they produce strong currents
ROTIFER. 165
in the water ; and small particles of food are brought within reach of the mouth, and swal- lowed rapidly, to be ground up by the powerful jaws placed below. There are two red eyes, and a long process, which is considered as the respiratory tube; these form what may be termed the head, and they can all be with- drawn at pleasure. The mode of progression is by swimming rapidly, with the wheels expanded, and body and tail stretched out, or. when moving on weeds, &c., by using first the head and then the tail, so as to form a kind of step; — when feeding, it attaches itself by the tail, and, ex- panding its wheels, seems to be happily and busily employed. It is an amusing sight to watch the current thus made, particularly if a
166 DROPS OF WATER.
little paint be put into the water; but I can imagine no sensation more wretched to those unfortunate little creatures, that come within the vortex caused by these powerful wheels, if they are aware to what it leads : they are often whirled round many times, before they either enter the mouth, or are so happy as to be refused by the monster. I have seen them re- peatedly, when beyond the influence of the cur- rent, fall down, as if spent with fatigue or fright. The eggs of the Rotifer can be seen distinctly in different stages of maturity within the body, and even the wheels of the young ones have been seen in motion by some observers. This species increases most rapidly ; from one individual a million may be produced in ten days. They are
ROTIFER. 167
found both in sea- water and in infusions, as well as in water which abounds in plants ; and they have been observed in the cells of Sphagnum obtusifolium, which is a kind of moss, with whitish leaves, growing in bogs and swampy places. Roeper says, that the cells have openings into the water, so that the animalcule may creep in, but he also relates that he has found them in the cells of parts of the plant not exposed to the water. If the cells of the Sphagnum are open at times, I can easily imagine that the Rotifer will creep in, for my own observation nearly proves that they will occupy any small cavity, where they perhaps may feel that they may feed in safety. I founded my opinion upon the following facts, which I observed last spring
168 DROPS OF WATER.
frequently. I flattered myself for some time that I had discovered a new species, but after re- peated observation, I came to the conclusion that it was in all probability the R. vidgaris, or a species of Philodina living as I may say in retire- ment. It appeared to me, that these specimens had placed themselves in the empty cases of the Floscularia, but they were invariably so much covered with extraneous deposit, that I could not decide the matter satisfactorily. The wheels, jaws, and respiratory tube alone, were visible beyond the edge ; and as it expanded and contracted within the case, in a similar manner to the Flos- cularia, I at first thought it was, like that ani- malcule, attached to, and the architect of, the case ; but as I never saw any of the specimens
ROTIFER. ' 169
leave the snug retreat in which they had fixed themselves, even though I watched many ex- amples, I still somewhat doubt, especially as there were no specimens of R. vulgaris swimming about. These specimens might prove to be species of Philodina, though I think those ani- malcules, as well as the Rotifer, have never been observed to form cases.
I have mentioned the tenacity of life in this animalcule, in the Introduction, and would advise the experiment to be tried by all interested in the truth. An instance of revivification of an equally small creature may be mentioned. The disease in corn, called ear-cockle, or blight, is caused by a very minute eel-like animal, which fills the seed, and remains dormant for some years, until the
d
170 DROPS OF WATER.
grain is opened and placed in water, then thou- sands of these minute creatures make their ap- pearance, and after some time revive, and swim about. I have tried this with corn four years old ; there is, therefore, nothing unlikely in the statement that the Eotifer may revive after being apparently dried for a length of time.
Actinurus Neptunius (Drop IV. fig. 12). — This extraordinary and elegant creature greatly re- sembles the Eotifer vnlgaris, but is easily distin- guished by the extreme length and wonderful for- mation of its tail, which, when at the full stretch, has a most striking appearance. The joints shut one within the other, like the tube of a telescope, and this action the animalcule is constantly re- peating when searching for food : it fixes the tail
ACTINURUS. 171
to some substance, and then stretches it and the body out to an immense extent, displaying its rotatory organs, and feeding for an instant, it then contracts, and pursues the same course in a contrary direction. The body is more slender than the Eotifer ; it has two eyes, and the chewing apparatus is very distinctly seen. The tail has three points, or toes, and two little horns attached to one of the joints : these expand, when the parts are stretched out, but as this form would prevent the. joint above that to which they are attached, sliding over them, they have the power of lying flat, and the tube closes without any impediment. This interesting animalcule is not so common as the individuals of the last genus, though frequently found with them.
172 DROPS OF WATER.
Philodina erythrophthalma is another slender- bodied animalcule, with a tail resembling the Rotifer, and two wheels as rotatory organs : it is found in vegetable infusions. P. roseola is flesh- coloured : Ehrenberg says that this species lays its eggs in heaps, and remains with the young for some time, forming one family. P. aculeata is distinguished by having soft spines upon the body, which give it a remarkable look ; the respi- ratory tube has a thickened end.
We now come to the last family into which these little creatures are divided ; it is called BracMontfa, and consists of several genera, con- taining species of great beauty. They have a lorica somewhat resembling the shell of a tor- toise ; the rotatory organs are divided into more
NOTEUS. 173
than two parts, though the two at the sides seem more particularly used as active organs. One genus, Anurcea, has no tail or foot, the others have a powerful instrument of this kind ; three of the genera carry their eggs attached to the outside of the body, giving them a very curious appearance, but seeming not to impede their progress through the water.
Noteus qiiadricornis (Drop IV. fig. 1 3) is a very fine and interesting animalcule, of considerable size, and, being broad and flat, soon attracts the eye. The lorica is nearly round, much flattened, rough, and on one side seems divided into com- partments ; it has also two spines near the tail, and four at the head ; the whole very transparent,
allowing the body to be seen within. There
_
174 DROPS OF WATER.
is no eye. The head is formed of a two- wheeled organ, and a ciliated part divided into three lobes ; with these the creature forms a strong current in the water, drawing towards it many small objects floating past, and occasionally selecting one, which then enters the mouth, where the jaws are ready to receive it. I have frequently seen it swallow small Polygastrica, one after the other, very rapidly. The tail, which is thick and very powerful, projects from the lorica, between the two spines at the base : it grasps a stalk with this forked tail, and then, raising the body, ex- tends its wheels, and feeds with avidity. It occa- sionally jerks the body backwards and forwards with great force, still holding by the tail, as if it were greatly excited, showing the strength of its
ANUR^IA. 175
muscles, and its health and vigour. It is fre- quently seen with eggs attached to the body, and is often found in water where decayed leaves and Algae are abundant.
Anurcea squamula (Drop IV. fig. 15). — There are many species of this genus, but they are all known by being without a tail or foot, and most of them carry their eggs attached to the body ; they possess an eye, and swim very rapidly. The lorica of the species squamula is smooth, rounded at the base, having horns in front, rather flat when seen sideways, and slightly curved : it has usually one egg of considerable size attached. A. stipitata has the lorica nearly square, with six spines in front, and one at the base, which might be taken for a tail, but it is quite rigid.
176 DROPS OF WATER.
The genus BracJiionus has a lorica like a tortoise- shell, and both front and base are spined; in some species it is smooth, in others rough. The rotatory organs are double, and the tail or foot is forked; the eggs are attached, and sometimes as many as ten are thus carried about. It has a single eye. B. poly acanthus (Drop IV. fig. 14) is one of the most common. It has a smooth lorica, with two very long spines and three short ones at the base, the upper part having many ; the wheels do not extend much beyond the edge of the lorica : the tail is strong, and powerfully grasps any substance in the water. B. militaris has the lorica rough, four spines at the base, and twelve long ones at the upper end. B. urceolaris is often seen in vast numbers in
PTEROD1NA.
177
fresh and brackish water : it has a smooth lorica, round at the base, and six short spines in front ; it is nearly as large as Noteus quadricornis. B. ru- bens is similar in shape, but the body is reddish. Pterodina patina (Drop IV. fig. 16). — This is one of the most delicate, beautiful, and transpa- rent of these lovely little beings. When viewed with a magnifying power of 250 diameters, it appears about the size of a sixpence, the lorica nearly round, and having no processes like the other genera of this family : it is exceedingly flat, and so transparent that, with the exception of some parts of the body, it is difficult to see this animalcule if the water is very clear. The ro- tatory organ is double, forming two wheels ; the tail, or foot, is thick, rather clumsy, and furnished
178 DROPS OF WATER.
with a disc at the end, by which it holds to sub- stances : it proceeds from near the centre of the under surface of the lorica, and is clearly seen when the creature turns on its side, which it does frequently in swimming. It has two eyes. When alarmed, it withdraws its wheels into the case, as well as the tail, nearly, and lies quite still for a moment, soon, however, becoming active again, and then nothing can be more inter- esting than the quiet movement and elegant appearance of this animalcule. It is not com- mon, but found sparingly in summer, principally among Lemna ; I once found it as early as February, but in small numbers. P. ettiptica has a lorica of an elliptical form. P. clypeata is found in sea- water: it has an oblong lorica,
LARVAE, ETC. 179
shaped somewhat like a vase, and smaller than the other species.
Many other creatures of small size, besides Infusoria, will of course be met with in water, but they will soon be recognized as belonging to other classes of the animal kingdom. Several long, worm-like creatures, are the larvae of the gnat and midge, or perhaps those of the dragon- fly or Tipula. There are several species, also, of Vibrio, which will soon be distinguished if the one found in sour paste is known. Then there is a pretty and very lively little creature frequently seen where duckweed abounds, the Lyncivx splia- ricus. It is enclosed in a round, transparent shell, the only projection being a beak, and the
180 DROPS OF WATER.
occasional protrusion of a foot ; the eyes are black : it feeds on animalcules, and pursues its prey with great activity. The Cyclops quadricornis, or water-flea, is larger than the Lyncius, and has branching horns, or arms : it is very transparent, and the lungs may be seen clearly in motion : it has but one eye. In some species, of which there are several abounding in stagnant pools, the eggs are enclosed in a membrane, and at- tached to the outside of the body. The Cypris is another curious creature, often found in great numbers : the body is enclosed in a kind of horny bivalve shell, which is not transparent; horns, or arms, are occasionally protruded from an opening, by the action of which it moves quickly. Their shells are found in myriads in
CONCLUSION. 181
a fossil state. The Amymone satyra may be ob- served in clear water, and is a beautiful object for the microscope : it is rather oval in shape, with four legs, two antennae, and one bright red eye, the whole body tinged with yellow, and very transparent; it moves quickly, but in jerks. These are a few only of the interesting objects which may be observed in water, besides ani- malcules.
I have now described as many genera and species of these exceedingly beautiful little beings, as the young student will probably be able to find in the course of several seasons ; but with diligent search, and frequent use of the micro- scope, nearly all these may be seen, and admired,
182 DROPS OF WATER.
in any neighbourhood, particularly as water may be conveyed (with care) even from a distance. I believe it is considered safer to fill the bottle in which the water is carried full to the cork, as the motion is then trifling, for the shaking of a half-filled bottle kills all the delicate kinds. When a drop of water, tolerably full of life, is placed under the microscope, all seems confusion to the inexperienced eye, the varied forms and rapid movements cause bewilderment in the mind of those who really wish to make a study of the names, habits, and peculiarities of these living atoms; but after some use of the glass this feeling subsides, and some one specimen attracts the attention, its shape is remembered, refer- ence is made to the illustrations, and there some
CONCLUSION. 183
species similar in form will probably be traced ; then, by referring to the description, the name of the genus or species may be found, with its cha- racteristics and habits. A species, when once impressed thoroughly on the mind, and its name remembered, soon ceases to attract attention, however frequently it may pass, if the eye is fixed on an animalcule which is new to the ob- server ; thus the confusion is soon lessened, and each drop at last produces so many old friends, that we have leisure to watch their movements, and be amused with their varied habits of life, and extraordinary modes of obtaining food. To those fond of watching the sports and movements of creatures of a larger growth, these little atoms will be never-failing sources of amusement ; and
184 DROPS OF WATER.
even should the observer only seek to wile away an hour, the objects are always novel and full of interest ; but to those who delight in examining the wonderful works of creation, there can be no greater source of pleasure than the possession of a good microscope, and the power of beholding minute beings, all of which are so totally dissimilar to those seen without this assistance. The gift of a microscope to a young inquiring mind, may, therefore, prove one of the purest sources of quiet pleasure, and lead to the cultivation of a taste for natural history in general, in the study of which so many hours may be profitably spent, which would, perhaps, otherwise be wasted in trifling or idle amusements. Allow me, then, to press this fascinating pursuit, not only on those who
CONCLUSION. 185
are already lovers of Nature, but on those who are seeking for amusement and occupation. I can promise with some confidence that they will at all events not meet with disappointment, and will with more probability discover that a never- failing source of delight and interest has been opened to them, — a new and almost unknown region, peopled with minute beings whose beauty cannot be surpassed or described ; —
Where, even in a water drop, These wondrous creatures revel, filling up The seeming void of nature ; even as planets, By the naked eye unseen, perfect The glorious firmament.
ALPHABETICAL LIST
OF
GENERA AND SPECIES.
Page. Acineta mystacina . .... 79
tuberosa ...... 79
Actimirus Neptunius (Drop IV. fig. 12) . . ". 170 Amoeba diffluens . ..... 112
princeps (Drop II. fig. 12) . . Ill
radiosa . 112
verrucosa ....... 112
Amymone satyra . . . . . . .181
Ankistrodesmus falcatus . . . . . 69
Anureea squamula (Drop IV. fig. 15) . . 175 stipitata . . . .175
188 ALPHABETICAL LIST OF
Page.
Arcella aculeata . . . . . . .113
dentata . . . . . . .113
vulgaris . 113
Arthrodesmus convergens (Drop I. fig. 6) . . 65
incus ....... 65
Astasia hsematodes (Drop II. fig. 9) . . . 104
nivalis . . . . . 105
pusilla ....... 105
Bacillaria cuneata (Drop I. fig. 18) . . . 75
paradoxa ... ... 74
- vulgaris (Drop I. fig. 17) . . . 74
Bacterium ...... 103
Bracliionis militaris . . 176
polyacanthus . . . . . 176
rubens ... . . 177
urceolaris . . . . . . .176
Bursaria truncatella (Drop III. fig. 7) . . . 132
Callidina elegans . . . . . .161
Carchesium polypinum (Drop III. fig. 3) . . 126
Chsetonotus larus . . . . .143
Chlamidomonas pulvisculus . . . . . 99
Closterium acerosum (Drop I. fig. 8) . 67 Diana? (Drop I. fig. 9) . 68
GENEKA AND SPECIES. 189
Page. Closterium moniliferum . . . . . 67
setaceum (Drop I. fig. 10) . . . 68
Colacium stentorinum . . . . . .108
vesiculosum 108
Cosmarium margaritiferum (Drop I. fig. 4) . 64
Cothuriiia imberbis (Drop III. fig. 5) . . . 129 Cyclidium glaucoma . . . . .115
Cryptoglena conica . . . . . . 87
Cryptomonas . . . . . . . 86
Cyclops quadricomis . . . . . .-180
Cypliidium aureolinn 113
Cypris . . . . . . . .180
Desmidium quadrangulatum . . . . . 61
Swartzii (Drop I. fig. 1) . . . . 60
Difflugia proteiformis (Drop II. fig. 13) . . . 112 Dinobryon sertularia (Drop II. fig. 11) . . . 109 Distigma tenax . . . . . . .108
wide 108
Doxococcus inequalis 85
pulvisculus ....... 85
niber (Drop II. fig. 2) 85
Echinella 77
Epistylis anastatica 127
190 ALPHABETICAL LIST OP
Page. Epistylis digitalis . 127
grandis ....... 127
nutans ....... 127
parasitica .128
plicatilis ..*.... 126
Euastrum insigne 63
oblongum (Drop I. fig. 3) . . . 63
Euchlanis triquetra . . . . . .157
Eudorina elegans (Drop II. fig. 7) . . . 97
Euglena acus . . . . . . .106
longicauda ....... 106
pleuronectes . . . . . .106
pyruin ....... 106
- sanguinea (Drop II. fig. 10) . . . . 105 viridis 105
Euplotes charon (Drop III. fig. 9) . 138
• patella ....... 138
Eloscularia ornata (Drop TV. fig. 1) . . . 145
proboscidea. ...... 145
Fragilaria grandis . . . . . . 75
— — rhabdosoma (Drop I. fig. 19) . . . 75
Glenomorum tingens ..... 85
Gomphonema ...... 77
GENERA AND SPECIES. 191
Page.
Gonium glaucuin . . . , . . . 93
pectorale (Drop II. fig. 5) . . . 93
Gvges . . . 89
\i O
Ichthydium podura . . . . . .142
Lagenella euchlora . . . . . . 87
Lepadella ovalis (Drop IV. fig. 8) . , . . 155
Lininias ceratophylli (Drop IV. fig. 2) . . 149
Lyncius sphaericus . . . . . .179
Mastigocerca carinata (Drop IV. fig. 9) . . . 156
Melicerta .150
Meridion vernale . . . . . . 76
Metopidia lepadella 160
Micrasterias denticulata (Drop I. fig. 2) . . . 62
Microcodon clavus (Drop IV. fig. 3) . . . 150
Microglena 84
Monas crepusculum (Drop II. fig. 1) . . 83
Navicula acus (Drop I. fig. 16) . . . 74
amphisbsena (Drop I. fig. 15) . . . 74
viridis (Drop I. fig. 14) . . . .74
Notommata longiseta (Drop IV. fig. 4) . . . 151
Noteus quadricornis (Drop IV. fig. 13) . . .173
Opercularia . . . . . . .128
Pandorina morum (Drop II. fig. 4) . . . 90
192 ALPHABETICAL LIST OF
Page. Paramecium aurelia (Drop III. fig. 8) . . 136
Pediastrum Napoleonis (Drop I. fig. 12) . . . 69
pertusum (Drop I. fig. 11) . . . . 69
Peridinsea . . . . . . . .115
Philodina aculeata . . . . . .172
erythrophthalma . . . . . .172
roseola ....... 172
Polyarthra trigla (Drop IV. fig. 6) . . . . 154
Polytoma uvella . . . . . . . 84
Prorocentrum micans . . . . . . 87
Pterodina clypeata . . . . . .178
elliptica ....... 178
patina (Drop IV. fig. 16) .... 177
Eattulus lunaris (Drop IV. fig. 7) . . . . 155 Rotifer vulgaris (Drop IV. fig. 11) . . . 162
Salpina mucronata (Drop IV. fig. 10) , . . 158 Scaridium longicaudum . . . . .153 Sceuedesmus quadricaudata (Drop I. fig. 13) . . 69
Spheerosira volvox 100
Spirillum ........ 104
Spiroteenia . . . . . . . 68
Staurastrum cuspidatum (Drop I. fig. 7) . . 66
Stentor creruleus 119
GENERA AND SPECIES.
193
Stentor igneus Miilleri
niger
polymorphus
Roeselii (Drop III. fig. 1)
Stephanoceros Eichhornii Stephanops lamellaris . Synchasta pectinata (Drop IV. fig. 5) Syncrypta volvox Syimra uvella (Drop II. fig. 6) Trachelius anas .... Trachelocerca olor (Drop III. fig. 6) Trachelomonas cylindrica
volvocina (Drop II. fig. 3)
Trichodina . ...
Urocentrum turbo
Uroglena volvox ....
Uvella glaucoma .
Vaginicola crystallina (Drop III. fig. 4)
decumbens
Vibrio
Volvox aureus
globator (Drop II. fig. 8)
Page. 119
118 119
119 118 147
160
152
94
96
132
131
88
88
119
119
97
83
129
129
103
102
102
194
LIST OF GENERA AND SPECIES.
Volvox stellatus .... Vorticella campanula
convallaria (Drop III. fig. 2) .
Xanthidium aculeatum .
— armatum (Drop I. fig. 5) Zoothamnium arbuscula
Page. 102
125
120
65
64
128
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