m

THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

PRESENTED BY

PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID

The Microscope, and Wings of Moths.

Plate 1.

1. The Microscope. 2. Scales of Ghost Moth, magnified 80 diameters.
3. Scales on the under side of Ghost Moth's winp, magil. 100 diams. 4. Green Forester Moth.

5. Scales of Green Forester Moth, magd. 100 diams. 6. Scale, mag. 300 diums.
7. Six-spotted Burnet Moth. 8. Scale of Burnct Moth, magnified 420 diameters.

THE

MICROSCOPE,

OR

DESCRIPTIONS OF VARIOUS OBJECTS OF ESPECIAL
INTEREST AND BEAUTY,

ADAPTED FOB

MICROSCOPIC OBSERVATION.

WITH DIRECTIONS FOE THE ARRANGEMENT OF A MICROSCOPE,
AND THE COLLECTION AND MOUNTING OF OBJECTS.

BY THE HON. MES. WARD,

AUTHOB OF "THB TELESCOPE."

ILLUSTRATED BY THE AUTHOR'S ORIGINAL DRAWINGS.

edition.

LONDON:
GKOOMBBIDOE AND SONS,

5, PATERNOSTER ROW

MDCCCLXX.

PBISTTED BY SIMMONS & BOTTEIT,
Shoe Lane, E.G.

CONTENTS.

CHAPTER I.

PACK

ON MICROSCOPES IN GENERAL . . 1

CHAPTER IT.
THE MICROSCOPE UNPACKED 10

CHAPTER, III.
COLLECTION AND MOUNTING OF OBJECTS ... .20

CHAPTER IV.
STRUCTURE or INSECTS' WINGS 30

CHAPTER V.
SCALES OF INSECTS AND FISII 37

CHAPTER VI.
HAIRS AND FEATHERS . * . 52

M352633

IV CONTENTS.

CHAPTER VII.

EYES AND OTHER OBJECTS

CHAPTER VIII.
VEGETABLE PRODUCTIONS ........ 79

CHAPTER IX.
ORGANIC REMAINS, CRYSTALS, AND ARTIFICIAL OBJECTS . . 93

CHAPTER X.
THE ANIMALCULES AND OTHER MINUTE INHABITANTS or WATER 105

CHAPTER XI.
THE ANIMALCULES, CONTINUED .121

CHAPTER XII.
CIRCULATION OF THE BLOOD »••.... 133

PREFACE.

SOME years ago, when the beautiful microscope represented
in our Frontispiece was a somewhat recent possession of
mine, I took much pleasure in exhibiting its wonders to my
friends, at the same time explaining the objects seen.

To write an illustrated account of these wonders was a
step which followed. The little book, with its coloured
plates, aided by minute descriptions, was intended as a
substitute for the actual exhibition. My object was rather
to present these wonders successively to view in the
manner of a panorama, than to guide my readers to the
practical use of the microscope; for, at the time when I
^rote, good microscopes were in the hands only of thf
few.

The case is now altered; excellent instruments, which
wiL answer most purposes, can be purchased for three or
four guineas, and the microscope is likely to become, as
one of its exponents remarks, " the companion of every
intelligent family." Therefore, in again employing pen
and pencil in the service of the microscope, my object
will be to unite the provinces of the Guide Book and the
Panorama ; attending to the former, in the hope of making
my remarks useful to those who are already in possession
of a microscope, while I continue to preserve the latter —
namely, ihe Panoramic method — selecting a few from the
multitude of lovely scenes presented by the microscope, in
order to attract those readers who, unversed in micro-

VI PEEFACE.

scopic marvels, might possibly feel repelled by a complete
and lengthened treatise.

The utmost care has, however, been taken to make
this work strictly accurate in its statements, and exact in
its pictorial representations of the objects described. /£)

The Author can desire no better success for the book
than that its perusal may now and then induce a reader to
obtain a microscope, and by its aid enjoy those realities
which far surpass all pictures and descriptions.

In the days of my microscopic displays, a working
man came, half shily and half pleased, at the persuasions
of a few of my young friends, to look through the instrument
at some striking object. He gazed attentively for a moment,
and then exclaimed, in considerable surprise, "It is beau-
tiful— but, is it true?" "Yes, my friend," (might have
been the reply,) "it is true; it is itself a truth and a reality."
And in this consists the charm of microscopic research.
With a suitable instrument, and a little leisure time at com-
mand, how happily is the observer brought face to face witi.
the minuter parts of God's creation, and how easy it seems
at once to enjoy and to learn. It is like visiting a rich. Kit
hitherto undiscovered region — like opening a page, hitherto
unread, of a treasured volume. And while we explore and
study, we feel a new sense of the unfailing power and infinite
wisdom of the Great Creator, whose mercies are over all
His works.

BELLAIE, Mo ATE, IEELAIID.

THE MICROSCOPE.

CHAPTER I.

ON MICROSCOPES IN GENERAL.

MICROSCOPE— a complete and beautiful
instrument by Ross — stands on my table.
I have had it so long that it feels almost
like a thing indispensable. Yet I recall the time
when its purchase was decided on by a kind parent
as a desirable help to the researches in which I
delighted, and which I had already pursued with a
good deal of diligence, aided only by a common
magnifying-glass. A costly instrument was ob-
tained, worthy too of its high price, from the excel-
lence of its glasses, the extreme finish of all its parts,
and the multitude of appliance's which accompanied it.
It arrived one day from London; its mahogany box
was carefully lifted from the packing-case, and tho
doors were opened. And then I remember feeling
somewhat disheartened ; firstly by a difficulty in
finding the uses of all the bright apparatus which
met my eye ; and next by the want of suitable ob-
jects to examine. From various sources information

1

2 The Microscope.

on these points was collected ; and to convey it in
a simple manner to others is my present object.
There is also another kind of information — of which
I was at the outset made personally independent, by
the possession of an excellent microscope, chosen,
indeed especially bespoken, by an unusually com-
petent judge of such a matter — but which I have
endeavoured to obtain for the sake of others ; I mean
as to what points are especially worthy of attention
in the choice of a microscope, and what luxuries in
its apparatus can be dispensed with, with a view to
obtain a sufficiently good instrument at a low price.

To convey this information, a few words on micro-
scopes in general are desirable. These instruments,
however various in their details, are made on just two
different plans — the simple and the compound. An
explanation of the principle of each will presently be
given ; meanwhile, it will be sufficient to state that a
compound microscope has a long tube, and at least
two glasses, one near each end of the tube, while the
latter has no tube, and may have only one lens.

Reading-glasses, hand- magnifiers, and Coddington
lenses, are, in principle, simple microscopes, though
that name properly belongs to those only which have
a fixed stand : of this class is the smart-looking little
instrument which is represented at No. 1, A, screwed
on to the lid of the mahogany box, into which ifc
packs nicely when not in use. The hand-magnifier,
B, is the simplest of all simple microscopes : it con-
sists merely of one lens, in a tortoise-shell frame,
made to shut up between two other plates of the same

On Microscopes in General. 3

material, like a knife- blade in its handle. Sometimes
three lenses are thus arranged, and by using one or
more of them at a time, the magnifying power is
varied. Of this form was the " magnifying-glass "
already alluded to, which the writer found very useful
before possessing Ross's Microscope. The Codding-
ton lens will be seen represented at woodcut No, 3,
among the collector's apparatus — its glass shutting up
into a neat little cylindrical frame, with a short handle

No. 1 — A Simple Microscope. B. Hand-magnifier.

to which a chain or string can be attached. This in-
strument, and a good little hand-magnifier, like that
shown at No. 1, B, will always be found useful ap-
pendages to the watch-chain — always at hand to
examine objects out of doors. The Coddington lens
has by far the higher power of the two, but from its
requiring to be held very close to objects it cannot
always be used to advantage. The rnagnifying-glass
becomes a microscope when its lens (or combination

4 The Microscope.

of lenses) is fixed to a stand of any kind ; and in its
complete form it should have a little plate of metal, c,
No. 1, called the stage, on which the objects are
placed; a mirror, d, to throw light on the objects from
below ; and a condensing lens, e, for the illumination
of objects from above. Probably there will be a screw
head fixed to rackwork for bringing the lens to the
correct distance required for showing the object clearly.
There will also be various useful pieces, of apparatus,
as a pair of forceps, a box for holding minute live
things, some slips of glass, etc. And there will be
two or three different lenses, which can be used either
separately or screwed together, giving good variety of
magnifying power. The lowest power of such a
microscope would show the " earwig's wing" slightly
larger than at fig. 2, Plate II., and the highest might
nearly reach the magnifying power shown at fig. 9 in
the same Plate. Even a higher degree of magnifying
is attained by an ingenious combination of lenses;
but the performance of even the best of these Jiigli
powers of the simple microscope is unsatisfactory,
compared to the corresponding power of the compound
microscope ; and for still greater magnifying the latter
instrument alone supplies our need.

The difference between its principle and that of
the simple microscope should now be explained. In
the simple microscope we look directly at the object,
with the lens close to the eye ; but in the compound
microscope we use the lens to look, not at the object,
but at an image formed ly another lens placed furthest
from our eye, and next to the object ; that image is

On Microscopes in General. 6

formed (as it were, in the air,} between the two lenses.
It is already larger than the object, and is further
magnified by the upper lens. A very great increase
to the magnifying power is thus obtained, but to ob-
tain it with perfect clearness, and with freedom from
various drawbacks and inconveniences, has long
exercised the cleverness of opticians. The combina-
tion of lenses next the object, called ' ' the object-
glass," requires great care and trouble in its construc-
tion. The proper length for the tube, and due form
for the upper set of lenses (or " eye-glass ") also
demand much attention ; but this care and attention
have not been bestowed in vain, as great excellence
has been attained.

Compound microscopes bear a general resem-
blance to each other in external appearance, (see fig.
1, Plate I.,) yet a distinction may be made among
them into two principal classes; namely, the large,
substantial, and complete instruments, in which perfec-
tion has been the aim, and the smaller and lighter
ones, which have been made with a view to cheapness,
although no trouble has been spared to render them as
good as possible for the price. And for full information
about various simple and compound microscopes, with
most interesting details about their principle and con-
struction, I would refer the reader to Dr. Carpenter's
valuable book, " The Microscope and its Revelations."
While studying the opening chapters of that work,
the reader feels as if visiting the establishments of
various opticians, at home and abroad, arm-in-arm
with an ever ready exponent of every point of interest

6 The Microscope.

connected with the microscope,, free from the bewilder-
ment and fatigue which would doubtless attend an
actual inspection of a number of instruments.

The intending purchaser of a microscope, if limited
as to price, should at least take care that the micro-
scope shows objects clearly, and is perfectly achro-
matic, that is, without those fringes of rainbow
colours always seen surrounding objects in inferior
microscopes. It should also be constructed to
lean backward, (see fig. 1, frontispiece,) as being far
less fatiguing to the observer than the upright
position. It should have at least two different degrees
of magnifying, and one of these should be of low
power, with large field of view, for the purpose of
showing as much as possible of an object at once.
These, with the condensing lens and mirror, to throw
light on or through objects, are the things indispen-
sable. Among the luxuries are screws for moving
the stage back and forward, and from side to side ;
apparatus for exhibiting the beautiful effects of what
is called "the polarization of light," and several
additional magnifying powers. An observer with
some prospect of leisure, and likely to use the micro-
scope a good deal, might do well to purchase an
instrument to which additions could be made from
time to time. The object-glasses are the most ex-
pensive part of the microscope, and the purchase of
an additional one therefore adds a good deal to the
total cost.*

* The object-glasses supplied with microscopes are generally
known as the "two-inch" power, the "quarter-inch," etc. These

On Microscopes in General. 1

While describing the different kinds of microscope,
a few words should be said on the binocular micro-
scope, and the solar and oxy -hydrogen microscopes.

The binocular microscope (No. 2) is an ingenious
application of the principle of the stereoscope to the
compound microscope. Some objects are extremely
well suited to this mode of observation, and some
details which appear confused and unmeaning when
viewed with only one eye, appear to assume form and
solidity in the binocular instrument.

The solar microscope is pronounced in an excel-
lent article, published more than twenty years ago in
the " Penny Cyclopaedia," to be nearly superseded
by the oxy-hydrogen instrument. The principle is
the same in both ; the rays from the sun or from the
brilliant artificial light are thrown on the object, and
then through a kind of simple microscope to a large

names were originally given to convey an idea of the performance
of the compound microscope, as compared with that of the
simple (see Quekett on the Microscope, chap, ii.) It may be
useful to state the powers of each of the object-glasses with the
lowest eye-piece of the microscope used in this work. It will give a
general idea of the powers of object-glasses, but as these vary
slightly in each microscope, the purchaser of an instrument should
always obtain a table of its powers.

Lowest eye-glass and two-inch object-glass 20 diameters.

Ditto, and one-inch object-glass 60 „

Ditto, and halt-inch object-glass 100 „

Ditto, and quarter-inch object-glass 200 „

Ditto, and one-eighth of an inch object-glass ... 420 „

The expression "diameters " will be found explained at page 31.
The two other eye-glasses supply intermediate powers, and the follow-
ing higher powers, 670,900.

8 The Microscope.

screen placed at a considerable distance. These in-
struments cannot be said really to magnify as much
as the compound microscope. The farther the screen
is removed, the larger will be the image, but it will be
at the expense of its light and clearness; this sort

No. 2. — Binocular Microscope.

of instrument is not intended for the purposes of in-
vestigation, but rather as an amusing and instructive
exhibition.

The oxy-hydrogen microscope, though cumbrous

On Microscopes in General. 9

in its appliances, works of course at the pleasure of
the exhibitor : that light shines when wanted ; far
different is the case with the solar instrument, at
least in this climate ! It screws into a hole in a
window shutter, waiting for the sunshine that often
fails to come. A microscope of this sort was the
first ever shown to the writer, who afterwards became
its owner, and recalls to mind the exceeding interest
with which parties of young people would look
together at the objects, imaged in gigantic propor-
tions, the grief they evinced when the light suddenly
faded, and the good humour with which they con-
sented to watch the picture of the drifting clouds,
thrown camera-obscura-wise on the screen by
removing part of the machine. Then how often
even this faded away, rain came on, and the exhi-
bition closed abruptly. It was at the time a dis-
appointment ; but led, I believe, to my trying to
draw microscope pictures less transient than those
on the screen, and to address a larger number than
I could well have assembled around the old solar
microscope.

10 The Microscope.

CHAPTER II.

THE MICKOSCOPE UNPACKED.

IT it now be supposed, reader,, that you
have chosen your microscope, either from
a careful study of books, or by the advice
of some friend "good at need," and have com-
menced to unpack it. You will probably find the
tube and the stand detached; the eye-glasses,
or the single eye-glass, arranged in the case, and the
object-glasses put by into little brass boxes. "You
take out the stand, and place it on your table. Some
microscopes have a tall case, capable of holding the
microscope ready for use, with the tube attached to
the stand. Should yours not be thus arranged, you
will screw on the tube ; but you had better put on the
object-glass first, as there is a kind of ' ' knack " in
making it screw on, and an object-glass might easily
be injured by letting it fall. Choose the object-glass of
lowest power, as easiest to work with ; you will know
it by looking at any small object or piece of printing
through it, as it will show this less magnified than the
other object-glass or glasses. You place the eye-glass
in the upper end of the tube, if it is not already there.
Is the microscope now ready for looking at an

The Microscope Unpacked. 11

object ? Not quite; we must arrange for throwing
light on the object, for that is a great and important
part of the microscopist's craft. You cannot carry the
small objects you examine close to the lamp, to
examine their surfaces, or hold them between your
eyes and the light with a view of seeing their interior
structure; but you can bring the light down upon
them with what is called the " bull's-eye," or conden-
sing lens, (Plate I., fig. 1, C,) or you can send light
through them with a mirror (B). You will find both
packed somewhere, the condensing lens perhaps fit-
ting into the case, and the mirror perhaps already
attached to the stand. Daylight or lamplight are both
suitable for the use of the microscope, but many an
observer finds evening hours to be the only leisure
time. Fortunately the observation of objects by
lamplight is particularly pleasant and satisfactory.
Were I asked to give an opinion as to the preferable
light of the two, I would say, daylight for some sorts
of investigation, as, for instance, for ascertaining the
exact colours of objects; but lamplight, unquestion-
ably, for exhibition.

Do not use a candle, it flickers so unpleasantly,
and its height changes as it burns down ; use a lamp,
a small paraffine or other lamp about the same size
will answer very well. For illuminating opaque
objects, you should raise the lamp on a box, or
something of the kind. Try what a bright little focus
of light you can make with the bulFs-eye lens on a
scrap of paper. It will be easier at first to manage
by leaving the microscope in its upright position than

12 The Microscope.

by bending it backward. Now for an object,, some-
thing fresh, bright, and effective — a little flower, a
blade of grass, or a frond of fern. If London-pride
be in bloom, you cannot do better than place one of
its flowers on the stage, or in the pair of forceps
which probably accompanies the microscope. See
that the light is properly condensed upon it, then
look into the tube ! You will see, perhaps, something
very white and brilliant, but very indistinct, and
placed uncomfortably awry in the field of view ; move
the object a little till it is nicely in the centre, and
turn the screws which raise and lower the tube, till
the little blossom suddenly shows itself like some
superb hot-house flower. If you move it slightly,
while viewing it through the microscope, you will
find that it is inverted — shown upside down ; this is
the case in all compound microscopes, but you soon
become accustomed to it. Now for an attempt with
the transmitted light, (that is from the mirror B.)
The thickness of the London-pride flower will prevent
its being viewed in this way ; try a blade of grass,
and before changing the mode of illumination, view it
as you have just viewed the flower, for that is one
comfort in lamplight, you can so easily put successive
objects in the bright little focus of light, and there
they are at once, visible in the field of view. Thus
you can quickly show the blade of grass as an opaque
object, lowering the tube a little till you see it clearly
— like some rich fabric woven of green and silver,
with occasional stripes of plain green, ornamented
with lines of long, glassy, colourless beads, and brist-

The Microscope Unpacked. 13

ling at each edge with saw-like teeth. Now take
away the bull's-eye lens, place the lamp somewhere
near the mirror, and move the latter about till you
see the light gleaming brightly upward through the
blade of grass. You prepare to look at it, but per-
haps are dazzled by the lamplight. If the mirror has
two sides, one will be concave, the other plane, and
the latter will perhaps suit best with a low power ; or
you may moderate the glare from the concave side
by turning the " diaphragm- plate " (see p. 16), or by
placing a piece of tracing paper under the object.
When all is rightly arranged, you will see the grass,
a rich green fabric still, but altered. The long trans-
parent beads have disappeared ; the plain green lines
are now the brightest part of the object, in conse-
quence of their being the thinnest. The central rib
is nearly black, from its real thickness. The saws at
the edge stand out vividly on the bright back-ground,
and the whole blade shows a sort of cellular struc-
ture, which you would like to see made still larger.
If you have a second eye-glass, you may substitute
it for the one already in use, and thus gain a higher
power, but in many cases you will not find this so
satisfactory a method as that of changing the object-
glass, while the eye-glass remains undisturbed.
Should the object-glass now applied be one of some-
what high power, you will find that, alter the screws
as you will, you cannot get the whole of the blade of
grass sharp and distinct ; that is caused by its want of
flatness, and is often an indication that you are em-
ploying an unsuitably high magnifier ; if, however,

14 Tlie Microscope.

you cannot ascertain what you want with the lower
power, you must be content to see but a small portion
of the object clearly "in focus/' and cultivate the
habit of disregarding the rest.

The beginner will not probably succeed in finding
anything nearly so well suited for observation with the
high object-glasses as some of the beautiful micro-
scopic preparations supplied by opticians. In these,
the object is placed on the centre of a slip of glass,
measuring three inches by one, and covered by a little
piece of thin glass manufactured for the express pur-
pose, and securely joined to the thicker slip. You
will do well to have a few of these at hand, both to
assist you in learning the use of your microscope, and
because if you wish to prepare objects for yourself,
the ready-made ones will show you what your own
work ought to resemble.

A single scale of a moth, like that at fig. 8,
Plate I., would be suitable for looking at with a
powerful object-glass; and a small group of such scales
will easily be procured. Let the microscope incline
backward to whatever height is most convenient as
you sit at your table. Arrange the light properly,*
and place the slide upon the stage — the slide, I
should explain, means the slip of glass with its pre-
pared object. There will be some sort of ledge on
purpose to support it in the inclined position of the
microscope. Find the object's place while the least

* A very complete article on the illumination of objects will be
found in the " Intellectual Observer," for January, 18G3. Its title
is " The Eye and the Microscope," by H. J. Slack, Esq.

The Microscope Unpacked. 15

powerful magnifier is still attached to the tube, and
getting it into the centre of the field, take off the
object-glass of low power and substitute the higher
one. Look in — all is hazy, because the increased
power requires the tube to be lowered. But lower it
carefully, or you may presently find your object-glass
and slide meet with a crash, resulting in the breakage
of one or both. It is well to do this screwing- down
with the eye removed from the tube, and steadily
fixed on the object itself; look edgewise, and screw
downward till the object-glass and object nearly
touch, then place your eye to the eye-glass, slowly
reverse the movement of your hand, and the object
will start into clearness when at the proper dis-
tance ; and if there is an additional screw for what is
called the " fine adjustment," you can perhaps gain
further exactness in the focus.

With a little practice you will soon estimate the
proper distance for each object-glass; and you will
also find it tolerably easy to find the object, even
without first getting it to the centre of the field with
the help of a lower power ; you may move the slide
somewhat rapidly about with your hands till the
object glances across the field, then lay it on the
ledge, reverse the motion which inadvertently whisked
it away, and you will soon see it coming back into the
field of view.

" Which eye shall I shut ?" is not an unfrequent
question of persons to whom a microscope is shown.
Neither, is the answer in which all practised observers
seem to agree. Keep open the unemployed eye, and

16 The Microscope.

for this good reason, that the doing so will go far to
prevent injury to your sight. You will perhaps find
it easier to do this by making a card-board shade to
slip on to the top of the tube ; you can shape it by
cutting off its corners, and it will be well to cover it
with black cloth or velvet. To the rule of keeping
both eyes open, Dr. Carpenter adds another, namely,
that of not continuing to observe any longer than you
can do so without fatigue ; and he reports in his own
case an entire freedom from any injury to his eyes,
after twenty-five years of microscopic study. I can
add a somewhat similar testimony to the safety to
eye-sight of (at least occasional) microscopic occupa-
tion, for I cannot remember ever to have felt my eyes
in the slightest degree fatigued (much less injured)
by the microscope.

But to return to our unpacking of the instrument.
You will find, besides the apparatus now explained, a
few other things. There will be the " diaphragm,"
a metal plate perforated with three or four holes of
different sizes, and constructed to turn on a pivot, for
the purpose of modifying the light from the mirror, or
shutting it out altogether when an opaque object is
examined. There may also be, packed into the box,
two or more bright little concave mirrors, called Lie-
berkuhns (from the inventor's name), and intended
for the illumination of opaque objects. They fit on to
the object-glasses, collect light from the mirror below,
and bend it down on the object. A little black cell,
to fit somewhere below the stage, is sometimes sup-
plied with them, to cut off direct light from the mirror.

The Microscope Unpacked. 17

If you have not this, a round scrap of black velvet or
paper gummed under the slide, will answer the same
purpose.

Then there will be " stage -forceps/' very useful
for holding flowers and similar objects for examina-
tion with the lower powers ; and a " live-box," other-
wise called an " animalcule-cage/' which you will see
represented at No. 3, close to the little bottle ; it con-
sists of two pieces of glass in brass fittings, between
which small water-animals can be placed in a drop of
water, the drop flattened out till the glasses nearly
touch. The upper glass being always very thin,
stands in particular danger of being broken ; a grain
of sand or some hard little piece of root in the en-
closed drop of water will often cause it to crack
across ; but this need not much disconcert the ob-
server, as one of the circular pieces of thin glass,
generally sent with a microscope for mounting objects,
will be likely to fit the live-box, and fastened in with
sealing-wax varnish, or some such cement, will replace
the broken glass, and make all right again.

If you have any more apparatus requiring explana-
tion, I must refer you to the work of Dr. Carpenter,
and that of Mr. Quekett,* from which latter I received
much help when beginning to use the microscope.

A few words should be said about the care of the
microscope. It should always be put by when not in
actual use. Little specks of dust on the glasses are
so annoying, that the instrument should be protected

* " Practical Treatise on the Use of the Microscope." Bailliere,
London.

2

18 The Microscope.

from them as much as possible. You should either
replace every part of the instrument in the case, or —
a far more agreeable plan — have a glass shade which
will cover the microscope and its accessories, and
under which they may be quickly placed, and in
doing this the glasses themselves should never be
touched by the fingers.

With all precautions, however, the observer may
find that the glasses do require cleaning. An old or
borrowed instrument may come into your hands, with
an evident indistinctness in its performance. If the
defect consists of a general paleness in the image, this
indicates that the object-glass requires cleaning ; while
large dark blots tell of dust on the eye-glass, and you
can prove it by seeing whether they move when you
turn the eye-glass round. You should proceed as
carefully as possible about the cleaning. Firstly, dust
the surface with a soft camel's-hair brush to remove
loose particles, then wipe the glass with either a very
soft piece of leather or silk handkerchief, and keep it
for that use only, shut up in a little box. You had
best unscrew as little as possible, and replace each lens
as soon as clean, lest you might forget its proper
position.

Dust inside the object-glasses is difficult to reach,
but by holding the open end of the object-glass down-
wards, the camel's-hair brush generally removes it, or
a small pointed bit of wood may be required for press-
ing a piece of soft leather to clean near the edges of
the lens. But all this must be as gentle as possible,
and not to be done where it can be avoided. " Hard

TJie Microscope Unpacked. 19

as the materials are (I quote from the Rev. T. W.
Webb's book on the Telescope), scratching is an easy
process ; and the result of ordinary wiping may be
seen in an old spectacle-glass held in the sunshine/'
completely covered with scratches; surely the most
valuable part of a good microscope deserves better
treatment.

20 The Microscope.

CHAPTER HI.

COLLECTION AND MOUNTING OP OBJECTS.

|ND now let us discourse about objects for the
microscope. I hope the reader, by inspect-
ing the plates, and reading the descriptions
which follow these preliminary chapters, will find some
objects easy both of attainment and preparation.

The collector of objects for the microscope will
most probably have a bias in favour of some particular
branch of Natural History. Entomology was my
favourite pursuit, and this will account for the promi-
nent place occupied in these pages by specimens taken
from the insect world. Some observers may feel in-
clined rather to devote attention to other departments
of nature, to which I have made but scanty allusion ;
my advice to each would be, collect as much as you
can of the things you like best, and learn how to see
and study them — all independent research, especially
where you note down, and if possible, draw what you
see,* is interesting, and may prove to be valuable.

* A camera-lucida is supplied, or an old one can be arranged, to
fit on to the eye-piece of the microscope, and enable the observer to
see at once the magnified image of the object, and a sheet of paper
on which, to trace its outline. When the first difficulty in using it is
mastered, it affords a valuable help in obtaining faithful drawings
of objects.

Collection and Mounting of Objects. 21

But, besides the class of objects which may happen to
be especially interesting to you, you will also like to
have a tolerable variety of miscellaneous things ; and
the collection of these will give interest to many a
country ramble. In summer, especially, both land
and water abound in wonders for the microscope , you
will soon almost instinctively secure the minute lichen,
the delicate frond of fern, the floating thistle-down,
with a view to its subsequent inspection ; and every
pond will yield a rich supply both from the animal
and vegetable world.

No. 3 represents a group of implements suitable
to a fisher for the microscope. Observe the little wide-
mouthed bottle to carry your treasures, the long
stick, to which a muslin net, a spoon, or a small cut-
ting hook can be screwed — the latter being intended
for obtaining pieces of water- weed, to which several
microscopic plants and animals will be found adhering,
and a live-box, which, with the Coddington lens, will
be useful in enabling you to see on the spot what kind
of success has attended you. Also the collector will
probably ere long set up a box of odds and ends,
which may come in usefully. It will look somewhat
like the collection of things which the skilful fly-fisher
gets together ; and a description of it might suggest
the contents of the witches' caldron to the reader's
memory. For instance, hairs from valuable skins, as
those of the tiger, lion, etc., fishes' eyes, remarkable
feathers, scraps of eel's and sole's skin, and sundry
cast-on7 entomological specimens, which most collec-
tors of insects have to spare.

22

The Microscope.

These remarks may sufficiently suggest the methods
by which the objects described in this book were got
together ; for it may be well to mention that I had
the pleasure of preparing nearly all of them, as well
as of drawing and describing them. I can therefore
add from experience a few hints about what is called
the " mounting " of microscopic objects, that is, of
making preparations on glass slides similar to those
supplied by opticians. Many things are fit to look at,
especially with the lower powers of the microscope.

No. 3. — Group of implements for the collector.

by merely placing them on the stage, or holding
them in the forceps ; some should be put into the live-
box; but the glass slide is perhaps the plan most
frequently applicable, as a satisfactory way of pre-
serving the object, and because the thin glass cover
placed over it tends to produce flatness.

I have already advised that you should examine
some slides supplied by an optician. If you do so, it
will soon strike you that all are not prepared in the
same mode. Some have on the centre a little raised

Collection and Mounting of Oljects. 23

cell of glass, or of some black composition, surround-
ing the object, filled with some oil or fluid, and
covered with a thin glass ; some appear to have the
object merely placed on the slide and covered
with the thin glass; while in a great number
you will notice a peculiar clearness, as though they
were incorporated with the substance of the slide
itself. These three modes are known as mounting in
fluid, mounting dry, and mounting in Canada balsam.
The first mode is suitable for various soft and delicate
structures, which require to be kept in a moistened
state : it so happens that I have but seldom practised
it; full directions, however, occupying some pages,
will be found in Dr. Carpenter's and in other works.

The best plan for mounting objects in the dry
method appears to be this : — Take the object, for
instance, the insect's wing on Plate II., fig. 2, after
you have succeeded in spreading it with water and a
camel' s-hair brush on a piece of glass, and have care-
fully removed it when quite dry. Place it on the
centre of the slide, and lay over it a little square or
round piece of thin glass ; hold this steadily down,
and a,pply some thick gold-size neatly round its
edges. This will fix on the cover, and can be after-
wards neatly trimmed, and a piece of coloured paper
with a round hole in the centre, pasted over the slide
to preserve the edges of the cover from injury. The
reason for using gold-size, instead of paste or gum-
water, is that the slight moisture caused by the last-
mentioned cements causes a kind of fungus or mould-
like plant to grow on and around the object, and

24.

The Microscope.

disfigure it. I employed gain, however, in preparing
several of my favourite slides, so small a quantity
being used that but little harm followed. Probably,
all preparers of microscopic objects have ways of
their own, and this was mine: — The first thing to pre-
pare was the coloured paper cover ; and I invariably
use emerald green paper, that I may recognize my
own slides at a glance. Taking a sheet of this paper
(to be had at any fancy stationer's), I make, with a pair
of compasses, a number of those charming little concen-

No. 4. — Method of Mounting Objects.

trie rings which are shown at No. 4, a. To cut up
the paper into little pieces like a, about an inch and a
half wide, and somewhat more than an inch high, and
to cut out the central circles, are pleasant and easy
tasks for spare moments. I generally make a great
number, and leave the centres purposely of various
sizes. When about to mount some objects — and, as
must have been often observed in similar occupations,
it is almost as easy to mount ten specimens, when one

Collection and Mounting of Objects. 25

sets about it as only one— I pick out thin glass
covers of corresponding sizes, each slightly larger
than the circle which it is to fit ; these I make per-
fectly bright and clean by rubbing with a soft hand-
kerchief. Then I lay the little papers white side up,
and putting some gum thinly round the aperture, lay
the cover on it, 6, and leave it to dry, endeavouring
to put it out of the way of dust. When it is dry
(and we know how quickly a thin coat of gum dries,
as in an adhesive envelope if we want for any reason
to open one which we have lately closed), I get the
slide ready to have the object placed upon it, by first
making it as bright as possible, and then placing an
ink spot on the under surface of it to mark its centre,
and of course to be afterwards rubbed off. If I wish
the preparation to look very smart and precise, I
rapidly rule ink lines from the opposite corners, know-
ing their crossing-point will be the exact middle of the
slide, c. Just over that, on the upper surface, I lay
the insect's wing ; then painting a little gum near the
edges of the paper, 6, I lay it down over the wing,
looking to see that the circle frames the object cen-
trally, then I press it down, and lastly trim the
projecting edges of green paper with a pair of scissors.
If I feel it at all possible that I could forget the name
of the specimen, I write it in a temporary way in ink
somewhere on the glass ; but ultimately, (namely,
when I have a number of slides ready,) I place neatly
upon the slide, d, two little cut-out green labels,
(" to make the balance true,'') the right-hand one
with the name of the object, the left with the mag-

26 The Microscope.

nifying power and the mode of illumination which
suit it, the latter particulars being given in some easily
understood abbreviations.

The Canada balsam method involves more diffi-
culty, and is most fully described both by Dr.
Carpenter and Mr. Quekett, as well as in almost
all works on the microscope. The balsam (which
is a very pure turpentine) is placed warm on the
slide, and the object is completely immersed in it.
The glass cover is then put on, and in time, some-
times in a few hours, the balsam becomes quite hard,
and the object remains fixed 'and bright, as a fly in
amber. This method of mounting has many advan-
tages : it adds greatly to the transparency of objects,
thus allowing the details of their structure to be
clearly seen, and it preserves them better than the
dry method. Being a very " sticky " substance, it
should be used in a careful and methodical manner.
It ought to be kept in a wide-mouthed bottle, with
a tall hollow stopper, like the bottles for gum, but
instead of a brush there should be a glass rod, not
fastened to the stopper, but projecting into it, while
its lower end stands in the balsam. With this rod a
single drop of the balsam is neatly placed on the slide,
which is held over a spirit-lamp or laid on a tin vessel
filled with boiling water. The great difficulty about
mounting in balsam consists in the trouble caused by
air-bubbles appearing in it. When the drop is placed
on the slide, a few of these bubbles may appear, but
presently burst from the warmth; but no sooner is the
object well sunk into it than a host of small bubbles

Collection and Mounting of Objects. 27

ooze out in all directions ; then more warming is done,
and sometimes with success ; the thin glass is gently
pressed down over the object — all which is detailed
in the works to which I have already referred.

I have always used, instead of a lamp or hot-water
tin, a night-light for warming the slide ; and I have
found it necessary to pass the latter from end to end
over the flame, as unequal heating would make it
crack across. I sometimes found the air-bubbles
dispelled by a drop of spirit of turpentine, but its
introduction was generally accompanied by a great
spreading of the balsam, and considerable stickiness
about the whole affair; however, benzine, ether, or
spirit of turpentine itself can be used to clean the
slides that have suffered. The slides, when finished,
so far as the placing of the thin glass over the objects,
must be left to cool gradually, and then allowed to
harden for some days, if in a warm place so much the
better ; and after that the superfluous balsam can be
scraped away, and the slide cleaned with a rag soaked
in benzine or turpentine. I generally cover the
objects so prepared with green papers, similar to
those for the dry objects; sometimes, however, I
leave them plain, with a view to employing the tf Lie-
berkuhns" already described, which require light to
be transmitted around the object. For the same
reason I sometimes leave the paper which fastens on
the thin glass in "dry" mounting merely large enough
to answer the purpose, or make the aperture very
large, employing as broad a piece of thin glass as I
can find to cover the object. It is usual to write the.

28 The Microscope.

name of the preparation with a diamond on the glass ;
I prefer the little green labels, however, as they help
to make the slide easily seen on a table, and I put
these on, even if no other piece of green paper is
admissible.

Many objects require special preparation, as flat-
tening out, cleaning in ether, etc., before they are
placed in the balsam. Some should be immersed for
some days in caustic potash, which makes them soft
and yielding; and all are rendered more manageable
by leaving them awhile to soak in spirit of turpentine
before placing them in the balsam. Some prepara-
tions will look badly, and even show air-bubbles when
first done, and yet some months later, from their more
complete hardening perhaps, be found free from de-
fects. For this reason it is often worth while to keep
apparent failures, consigning them to temporary obli-
vion, but scribbling upon them in ink any particulars
worth recording. Slides, however, which are evidently
hopeless failures can always be cleaned in spirits of
turpentine, or in wood-naphtha, which dissolves the
balsam very rapidly; and even the thin glasses can
again be made available. Turpentine which has been
used for cleaning purposes must not be employed in
making new slides. And in all plans of mounting it
is wise to work methodically, and have all requisites
neatly arranged, or various odd matters may show
themselves in the field of view with the object, such as
fibres of wool, cotton, and flax from table covers and
clothes; fibres of feathers from cushions, scales of
clothes- moths, etc.

Collection and Mounting of Objects. 29

And now, reader, for further information about
microscopic objects I refer you to the coloured plates
and the woodcuts which follow, and to my descriptions
of them. The plan employed in their arrangement is
this : we first go through a set of prepared objects,
which could be shown on a winter evening, or at any
time, and then we have an account of a summer enter-
tainment, with the wonders to be observed in the
structure of living things.

The coloured plates are all from my drawings,
but for most of the illustrations of animalcules I am
indebted to two or three experienced microscopists,
as I have never systematically studied this class of
objects, although I have repeatedly examined all to
which I allude in these pages.

For the guidance of those who prepare their own
microscopic objects, as all will do who possess and
really value a microscope, I give a list of the objects
in my plates which are mounted in balsam. It will be
understood that those not included in this list are
mounted in the dry method. Plate II., fig. 1, d, figs.
8, 9 ; Plate I., fig. 8 ; Plate IV., figs. 2, 3 ; Plate V.,
figs. 1, 2, 3 ; Plate VI., figs. 1, 2, 3, 4, 10; Plate VII.,
fig. 10,

30 The Microscope.

CHAPTER IV.

[HE prettily-rounded wing occupying a central
position (fig. 2) at the top of Plate II., is
that of an earwig. If you feel surprised,
reader, to hear that this rather unpopular creature
possesses a pair of lovely rainbow-tinted wings, I must
tell you that iny wonder was at least equal to yours
when I first succeeded in spreading them out, as in
fig. 3. But, in fact, there are few insects without
wings. The wings of moths and butterflies, of flies,
bees, and wasps, and of the dragon-flies, so common
every summer, are easily seen ; but an almost equal
variety of insects possess concealed wings, folded up
beneath wing cases. And these wings are generally
very beautiful and delicate, often showing rainbow
colours just as a soap bubble does, in consequence of
their extreme thinness ; yet so well are they protected
by the wing cases that they remain uninjured while
their owner plunges into water, or gropes his way
through the ground. Observe into how small a com-
pass the delicate wing of the earwig can fold. Fig.
1, «, represents it when fully opened. At fig. 2, 6,
you see it closing like a fan. Fig. c shows the two

".Yiugs of Insects.

Plate -3.

I:

1. Wing of Earwig, shewing its method of folding up.

2. Wing of Earwig, magnified 4 diameters. 8. Earwig flying, natural size.

4. Wing of Whirligig-beetle, magnified 5 diameters. 5. The same, natural size.

. Minute portion of Beetle's wing, magnified 420 diameters. 7. Wasp's wing, folded.

8. Wasp's wings, hooked together, magnified 3 diameters.

9. Hooks on Wasp's wing, magnified 60 diameters.

Structure of Insects' Wings. 31

bends which it then takes ; and at d, how tidily it is
packed ready to lay along the insect's back ! But let
us pause before we hurry it thus out of sight, and
turn again to its pictured representation, fig. 2, as
shown through a small magnifying-glass. The wing
should be held somewhat obliquely to the light, and
then the lovely colours, green, blue, red, and golden,
gleam with a soft radiance.

Do you ask the reason why we examine this wing
simply with a magnifying-glass, instead of with the
large microscope? It is because, taking the entire
wing, it is rather too large an object to be shown at
once. The lowest power of my microscope is twenty
diameters, and this object, you see, measures three-
eighths of an inch in width, so that if magnified to
twenty times that diameter, it would be shown a length
of seven inches and a-half, and, turn it as you might,
could not be fitted into a page of this book. And
here, perhaps, the question may arise, " Is fig. 2 only
four times larger than fig. 1, a t" The answer is, it
is four times its diameter, and this is the measure
employed in works on the microscope, and called the
" linear measure." It signifies that the object, when
stated to be, as in the present instance, ( ' magnified
four diameters," appears four times the height and
four times the breadth that the unassisted eye observes
it. The representation of the wing at fig. 2, takes up
sixteen times the space occupied by fig. 1, a; and
that statement of the amount to which it is magnified
is called the " superficial measure," or measure of the
surface, and can always be calculated by squaring the

32 The Microscope.

linear measure. Thus the wing represented at fig. 4,
being magnified five diameters, is magnified twenty-
five times by superficial measure, and the object repre-
sented at fig. 6, and described as being magnified 420
diameters, occupies a hundred and seventy-six thou-
sand four hundred times more space than that of the
minute structure itself. But the " linear measure" is
in every way the best and most convenient method of
stating the magnifying power employed.

The observer, after examining such an object as
this earwig's wing with a magnifyiug-glass, will do
well to submit it next to the lowest power of the com-
pound microscope, when probably some minute details
may appear demanding still further magnifying. A
power of a hundred diameters in a good microscope is
one which exhibits a great deal. The little folded
wing, fig. 1, d, is nicely shown with it ; its nineteen
folds may be seen squarely and neatly laid over each
other ; you reckon them as a shopman does the yards
of silk in a folded piece. Then, see the wing itself
with this power, you find it covered with very minuto
round marks, and fringed round with fine hairs.

Beetles do not fold up their wings into so small a
compass as those of the earwig, and accordingly tho
strong ribs or nervures are differently arranged. No.
5 represents the folded-up wing of the whirligig beetle
(Gyrinus natator], a little water-insect, remarkable for
its habit of whirling round on the surface of ponds
and brooks.* This wing, when expanded, appears as
in fig. 4, Plate II. With this low magnifying power
* A figure of this beetle will be found in Chapter VII.

Structure of Insects' Wings. 33

we can detect on its surface some pattern or graining
of wonderful delicacy and minuteness. To examine
this, we apply one of the high powers of the micro-
scope, attending, however, to the rule, to use the
lowest with which we can clearly see what we require.
How exquisite, how delicately finished is the appear-
ance of this little wing. An artist's eye looks with
pleasure on the bold curves and rich brown colour of
the large nervures, and the beautiful regularity of the

No. 5.— Folded Wing of Whirligig Beetle,
magnified 15 diameters.

smaller markings. These prove to consist of tens of
thousands of delicate hairs, while the wing is edged
with somewhat longer ones. I have drawn a very
small portion of the wing magnified 420 diameters.
Were I to represent the entire wing on this scale, I
must make it more than ten feet long ; yet it is orna-
mented with the same beautiful regularity over the
whole surface. Will you look, reader, at the real size
of the wing, and judge what must be the minuteness
of its delicate adornment ?

G

34 The Microscope.

In the wasp's wings, represented at fig. 8, we
have to admire their evident adaptation to the in-
sect's mode of life, as well as their beauty. They are
not so carefully stowed away as those of the earwig or
beetle, as it wants to fly so much more frequently. Yet
wasps often go into the ground — and bees (whose wings
much resemble those of wasps) creep into very small
flowers — therefore a pair of large broad wings would
be in their way. The contrivance they are supplied
with is very curious. They have four wings, two on
each side, and the upper wings fold once, lengthwise
(fig. 7), when the insect walks, but when it prepares
to fly, it straightens this wing by the act of raising
it, and the same action hooks the lower wing to it
firmly, giving it all the force of a single broad wing.
Fig. 8 represents the two wings thus joined, and
slightly magnified. To show the minute hooks which
are on the top edge of the lower wing (fig. 9, A,) I
must take my specimen in which the wings are pre-
pared separated from each other, and will magnify
them sixty diameters. The part of the wing on which
the hooks are placed is very small, not more than
one-twentieth of an inch in length. They clasp
firmly over a projecting ledge on the upper wing
(fig. 9, B). This is best understood by observing
a preparation (as in fig. 8), where the wings are
mounted ready clasped, and examining them on both
sides.

The dragon-fly's wings, which never require to be
folded up or reduced in size, are formed for strength
and lightness, and evidently for beauty too. The

Structure of Insects' Wings. 35

wings of the small dragon-flies, so common through
the greater part of summer, with bright blue, or
oftener red, bodies, are beautifully transparent, con-
sisting of a delicate membrane, stretched, as it were,
to a sort of ornamental network. Another dragon-fly,
rather larger, and with a metallic-looking bluish green
body, has more minute divisions in its wings, and in
each wing a brownish patch of shading, producing a
very soft appearance. It has not the little black spot
seen in the smaller species ; it seems as if that orna-
ment would not be in keeping with its softer shades.

But the wing which I have always thought the
most curious in my collection is that of a little beetle,
so small as to possess (so far as I know) no popular
name, but which in learned language, boasts an ap-
pellation of no less than nine syllables — "Trichop-
teryx atomaria." It is a very lively, active little
creature, common under moss in spring ; and is to be
observed like the larger insects coming forth in the
summer sunshine, and taking short but energetic
flights. Its wings are unusually narrow, and each
fringed with hairs half the length of the wing itself.
This long fringe surrounds it except in two places at
the centre, where the wing doubles up so as to allow
it to fold easily ; here it is replaced by short hairs. I
have a slide, showing the folded wing and its case
prepared side by side, and I can see that there is a
sharply- creased " plait " or " tuck " in this central
part, which shortens the narrow shaft of the wing ;
then the point of this shaft is doubled up, then
another fold stows all away neatly, and all the longer

36 The Microscope.

Lairs point nicely downward; while the little wing
occupies less space than the wing-case which is to
cover it.

The hairs on this wing require minute examina-
tion. With even so high a power as 100 diameters,
we fail to make them out ; but a power of 200 shows
them to be each fringed again like a feather, and
the same power shows that at the base of each of
the little wing-cases, which measure at their broadest
part only one sixty-second of an inch, there is a
delicate little comb formed with beautiful regularity,
and having (as I ascertained with the highest power
of my microscope*) one hundred and twenty teeth !
I imagine its use may be to remove all particles of
dust from the long feathery wings before the wing-
cases close over them. The thinly-scattered strong
bristles on the wing-case contrast with the regular
appearance of the tiny comb.

* 900 diameters. It may interest the reader to hear that Mr.
Spence, the late celebrated entomologist, in acknowledging an
account which I sent to him of some of the above objects, wrote,
" I was especially pleased with the figure and description of the
comb-like appendage to the elytra [wing-cases] of the minute beetle,
so admirably figured, of the existence of which appendage I was not
at all aware, never having examined this species with a powerful
lens."

Scales of Insects and Fish. 37

CHAPTER V.

SCALES OP INSECTS AND FISH.

| HE wings of moths and butterflies are actually
very like those of flies and wasps, etc. They
are thin and transparent in themselves, but
covered on both sides with beautiful scales, laid in
rows like the feathers on a bird, each row, in the
generality of specimens, overlapping a portion of the
next, so as to give to their surface, when sufficiently
magnified, very much the appearance of being tiled
like the roof of a house. Each scale has a small foot-
stalk, (Plate I., fig. 8, and Plate III., fig. 10,) which
fits into a minute socket on the transparent membrane
of the wing. The arrangement of the minute sockets
is well shown by making a preparation of a butterfly's
wing nearly divested of its scales. A good deal of
washing and rubbing will be found necessary to
remove them, and then the object is one from which,
when dry, mounted on a slide, and viewed by trans-
mitted light, a good deal may be learned.

But the wings in their natural condition, viewed as
opaque objects, are among the most lovely spectacles
presented to us by the microscope. Their appearance
strikes us with new wonder, as we observe the beau-

38 The Microscope.

tiful harmony of their hues, and the elegance of their
adornment. The wings are the only part generally
mounted for the microscope ; but if a whole butterfly
is examined, which may be safely and easily done by
removing one from an entomologist's collection and
sticking its pin into a morsel of cork, which is gene-
rally to be found in the handle of the stage forceps, it
will be seen that the whole bodies of these insects also
are clothed with scales.

In exhibiting the wings of moths and butterflies
the effect is much heightened by a proper arrange-
ment of the light, which should be placed so as to
throw an artistic shadow from every scale. This
suggestion may seem a trifle, but the trite maxim
concerning trifles tending to produce perfection will
excuse its being made.

Fig. 2 shows the scales of a moth very common
on fine evenings in June, called the " ghost moth ;"
they are very like bay leaves in shape. The scales on
the inside of the wing are different, and thinly
scattered (fig. 3). The wings of this moth are
yellowish, having (on the upper sides) what look
like delicately-painted streaks of pink ; these are red
scales.

Some of the scales of moths and butterflies will De
admired for their delicate hues ; others shine with a
brilliant metallic lustre, to which the best painted
representation could scarcely do justice. The " little
green Forester-moth " (fig. 4) is one of these ; it has
scales of two different shapes on its wings (fig. 5), the
longer being brilliant yellowish green, and the shorter

Scales of Insects and Fish. 39

bluish green. When highly magnified, the scales of
this moth are seen to be covered with a sort of orna-
mental carving ; each of the larger scales has six or
seven ridges on it, and rows of hollows between (fig 6).
The smaller scales are very similarly ornamented with
a pattern not quite so much raised.

This little moth is common in the beginning of
June. There is another, somewhat like it in shape,
and still commoner at the same time of year ; it is
called the Burnet-moth (fig. 7) . Its upper wings are
of a beautiful, very dark green, with round red spots ;
its lower wings red, edged with bluish black. The
dark green scales are glossy like satin, and the red
very bright in colour, but dull like cloth or flock paper.
This variety of surface forms a very striking contrast.
The dark scales of the Burnet-moth are sculptured in
a way similar to those of the green Forester. When
these scales are viewed as transparent objects, they no
longer appear green, but the pattern on them, when
viewed with a high magnifying power, assumes a
strange and almost startling appearance.

It must be remembered how small these scales are.
They are only like the finest dust or powder, and a
single one could scarcely be seen with the naked eye.
Yet every scale may be seen (with a magnifying power
of 150) to be marked with some dozen lines, clear and
sharp as staves of music, and between them are rows
of characters wonderfully resembling some old Baby-
lonish inscription (fig. 8).*

* The figure represents this object magnified 420 diameters, not
150. It could, however, be sufficiently well seen with the latter

40 The Microscope.

The scales of the green Forester-moth are somewhat
similarly inscribed, but not with equal distinctness.

Let us again adjust the microscope to view
" opaque objects/' and feast our eyes on a few more
specimens of Nature's mosaic work. The wings of
butterflies and moths have been compared to patterns
in mosaic ; though of course there is this great dif-
ference, that the pieces of mosaic are inlaid ; whereas
the scales of these insects, as I have already said, lie
over each other like feathers, fishes' scales, or tiles on
a roof. Still their general flatness, and the fact of
their delicate shades being usually caused by hundreds
of minute scales — the dark or light ones in greater or
less number according to the hue required — originated
the comparison.

I have examined some, however, in which the
effect of the shading is heightened in a way inadmis-
sible in mosaic work, but sometimes employed by
painters. It sometimes happens, that when an artist
is painting — for instance a landscape — and wishes
to bring out a rock or tree very vividly, he finds it
necessary to make a roughness on that part of his
canvas. A painter, whose works are familiar to
many, on one occasion actually made t)' ^ surface of
his picture rough by causing a small quantity of sand
to adhere to the canvas, and it had the desired effect
of giving brightness to what was then painted over it.

Now there is a yellowish-brown insect called the

power, although the additional size gained by further magnifying
makes it easier to engrave. The same remark applies to many othur
objects represented in this work.

Scales of Moths and Butterflies.

Plate 3.

10

1. Wing of Herald Moth. 2. Sfot on Herald Moth's wing, magnified 60 diameters.

3. Eye-like si.ot on -wing of Emperor Moth. 4. Part of eye-like spot, magd. 60 diams.

5. Scales of Underwing Moth, magnified 80 diameters.

7. Brimstone Butterfly. 8. Scales of Brimstone Butterfly, magnified 150 diameters.
9. Scales of Red Admiral Butterfly, magnified 100 diameters. 10. Scale, magd. 150 diams.

Scales of Insects and Fish. 41

Herald-moth, with, one conspicuous white spot on each
of its upper wings, shining like a star, or with the
peculiar brightness that this representation of it (Plate
III., fig. 1) would exhibit if we were to prick it with a
pin and hold it up to the light. On examining it with
the microscope, I found that this spot consisted of a
thick tuft of white scales, almost like a little brush,
and standing up much higher than the surrounding
parts of the wing (fig. 2).

In like manner the scales of the Emperor-moth,
a large insect with an eye-like spot in each wing, are
rendered much more ornamental by being set sloping
upwards instead of nearly level. There is a beautiful
semi- transparency in the wings of this moth, owing to
the thinness with which its scales are scattered ; but
their sloping arrangement gives brilliancy at the same
time. It is, of course, difficult to represent it on a
flat piece of paper. The eye-like spots are each
about the size of fig. 3, and fig. 4 is intended for a
small part of one of them, magnified sixty diameters.
The colours are white, morone crimson, a sort of
straw-colour and black, a beautiful and harmonious
mixture.

I have noticed another deviation from the plan of
nosaic work in the wing of a moth — one of the tribe
of " Yellow Underwing." The wing is rather dingy,
but with a silvery gloss in some parts, which induced
me to examine it. I found that the scales themselves
were shaded. In one place, for instance, where the
wing is brown and white, the microscope showed that
instead of having rows of white scales and of brown

42 The Microscope.

ones, the same scale was white and brown, and a very
curious and pretty effect it has (fig. 5).

The edges of moths and butterflies' wings are
highly ornamented. The scales are long, .and gene-
rally shaped like fig. 6.

You have probably observed the Brimstone But-
terfly (fig. 7) . It appears in spring, and looks almost
like a faded lime-leaf. You may observe some spots
on the edge of this butterfly's wings ; they are very
small, and appear a sort of rust-colour, but through
the microscope they are white scales tipped with pink,
shaded like those of the moth described last. Fig.
8 represents a few of them magnified 150 diameters.
Such a group, presenting as it does so little apparent
resemblance to the object to which it belongs, often
perplexes the beholders not a little, and tempts them
to describe it by far-fetched comparisons. For in-
stance, the friends to whom I first showed this object
bestowed on it the name of " the Alps at daybreak "
— the sun commencing to shine on the mountains
covered with snow, and the yellow scales below resem-
bling foreground vegetation !

Fig. 9 represents some scales from the under side
of the red Admiral Butterfly's wing, giving an ex-
ample of another and not unusual shape. Each scale
is covered with a number of lines, which look as if
they were ruled on it with the utmost precision (fig.
10). These fine lines are observed on the scales of
many butterflies and moths. A very high magnifying
power generally shows them to be slightly waved, and
frequently crossed by a *3cond set of lines of extreme

Scales of Insects and Fish. 43

minuteness. The degree of distinctness with which
these markings can be shown with various magnifying
powers forms a useful test of the excellence of the
microscope employed, and scales mounted for this
special purpose are supplied by opticians as " test-
objects."

So much for the scales of moths and butterflies.
Some other insects, including several beetles, are also
ornamented with scales. In fact, whenever I see an
insect presenting the peculiarly powdery soft appear-
ance of a moth or butterfly's wing, I always guess
it has scales, and generally find my supposition
correct. The Weevils (Curculionidce is the learned
name) are a tribe of beetles in which these scales may
be well observed. One of them is represented at
Plate IV., fig. 1. It is a dingy slow-moving little
beetle ; but how differently we regard it after we have
once seen it in the microscope ! When magnified
slightly we see that it is covered, or rather sprinkled
over with beautiful little roundish scales, arranged
with considerable regularity. These scales, when
magnified 100 diameters, gleam each like a scallop-
shell of burnished gold, and placed on the dark wing-
case of the beetle, are truly splendid (fig. 2).

There is another Curculio, somewhat similar in
shape to this one, but smaller and more promising in
appearance, as it is of a silvery green colour. It is
very common in April and May ; I have seen hun-
dreds on large beech-trees. Its body is really Hack,
with green scales of surpassing brilliancy. Fig. 3
gives an idea of their shape and arrangement, but no

44 The Microscope.

drawing could convey an idea of their radiant bril-
liancy and lovely colour.

These two last-mentioned objects are exceedingly
interesting when viewed by transmitted light ; small
fragments of them should be mounted for this pur-
pose. The shell of the brown beetle (fig. 2) appears
of a fine golden hue. The scales are of the same colour,
but appear as if sharply drawn in pen-and-ink lines ;
and in the vacant spaces the whole shell is covered with
a very curious system of lines, crossing each other in
the way called te cross-hatching " by engravers. This
same singular appearance occurs also in the shell of
the green weevil, and with many variations as to
arrangement and size, in all weevils which I have
happened to examine. It is particularly conspicuous
in the diamond beetle of Brazil, which is also one of
the weevils, and well known as a splendid microscopic
object when viewed by reflected light.

The green weevil's shell shows still better than
that of the brown, as a transparent object. We see
the same golden ground, but the scales, instead of
being colourless, become a lovely red, tinged with
orange when over the wing-case, and with bluish
pink when they happen to show beyond the edge of
the fragment.

The scales of fishes are interesting and pretty ob-
jects when viewed with the lower powers of the micro-
scope. Fig. 4 represents the scale of the perch. When
magnified four diameters we can easily make out the
graceful curving lines which cover it; these lines
appear as if continuous, and parallel to each other.

Scales of Insects and Fish. 45

They are not quite so, however, in reality, and a
sketch of them, when magnified eighty diameters, will
best explain their appearance (fig. 5).

The scales of the sole, and of many other fish, are
covered with similar lines. A sole's scale is repre-
sented in fig. 6. The lines on it are coarser than those
in the perch's scale, except just in the centre near the
ray-like spikes, where there are some finer lines
curiously arranged. These spikes are the part of
the scale which are outside, and give its roughness to
a sole's skin. The other end is the root of the scale,
and is rather deeply sunk in the skin.

The eel's scales are concealed altogether. When
I first began to prepare objects for the microscope, I
read in some old book that these were worth looking
at; so I procured a dry piece of eel- skin, but it was
long before I could find what I was in search of. I
scraped and scraped with a knife, and examined the
scrapings with a microscope, magnifying them 20 times
— 40 times — perhaps 100 — but no scales appeared.
I forget how I contrived to make them out at last.
But if I take a little piece of eel-skin and view it as
a transparent object, magnified rather more than four
diameters, the first thing I see is that the skin is
covered with star-like spots, and next I observe the
scales lying close together (fig. 7). And this is the
way to get at them : — I take the little scrap of skin
and tear it in two, exactly as if I were splitting a
card, for the skin consists of two layers. I can then
quite plainly see the scales sticking to the under
surface of the spotted piece, that is, lying between

46 The Microscope.

the two layers. I can easily lift them off with a knife,
and mount them for the microscope, while the skin
makes another very pretty object for ifc, not unlike
the spotted coat of a leopard. Four of the scales, and
the divided portions of the skin, are represented in
fig. 8; and fig. 9 is the smallest of these scales magni-
fied fifty diameters. The kind of network pattern is
of the same fineness on the larger scales.

The account which Dr. Carpenter gives of this
apparent network is that the scale consists of " a
layer of isolated spheroidal transparent bodies, im-
bedded in a plate of like transparence;" and these,
he adds, " appear not to be cells (as they might
readily be supposed to be), but to be concretions of
carbonate of lime." These pretty little scales are
white, and, viewed as opaque objects, they look like
black lace ; viewed transparently they are like black
lace, or like white lace held up to the light. The
apparent holes are the " spheroidal transparent bodies "
described by Dr. Carpenter, and his remark on the
transparency of the layer which encloses them is
verified when the scales are mounted in balsam, as
they then become nearly invisible in all ordinary
• modes of illumination.

They appear, however, in much splendour in the
ft polarizing apparatus " of the microscope, to which
I have already alluded (p. 6) as one of the luxuries
which can be dispensed with by a purchaser who is
limited as to the price of his instrument. It can,
however, be added to most cheap microscopes of
good construction, and is, as a matter of course, an

Scales of Insects and Fish. 47

accompaniment of the large and expensive ones. This
apparatus consists of two prisms, one arranged to
fasten below the stage, the other to slip over the
eye-glass ; and the object to be shown by transmitted
light from the mirror. By this arrangement, various
splendid colours are exhibited, and the effect is further
heightened by placing on the stage immediately under
the object, a slide containing a thin plate of the
mineral " selenite," which, when mounted in balsam,
is perfectly transparent, indeed invisible, in the
ordinary mode of illumination. A description of the
appearance of the eel's scale, when viewed with the
polarizing apparatus, will serve as a specimen of the
effects produced by this mode of exhibition.

The scale (fig. 9), which can with difficulty be seen
by common light, now appears, in a particular arrange-
ment of the prisms, to be projected on a black ground,
and to be of a beautiful silvery grey, nearly white at
the edges, and softly shaded to a deeper tint at the
centre ; and conspicuously placed over its surface are
two large black marks, similar to two V's placed
point to point, thus £>~<^ making a figure like a St.
Andrew's cross over the whole scale ; and these also
are very softly shaded at their edges. Now I make
the upper prism revolve slightly ; the two V's com-
mence to revolve also, but presently become much
wider, and gradually change to a pale brown, while
the vacant part of the slide changes from black to
light grey ; till, on the prism having turned one quarter
of the way round, two pale and nearly white marks
occupy the places of the original black V's, the broad

48 The Microscope.

intermediate spaces are light brown, and tlie back-
ground is white. The prism continuing to revolve
till half way round^ exhibits the brown spaces turning,
and gradually forming into vivid black V's as at first ;
and as it revolves through quarters three and four,
appearances exactly similar to those described in
quarters one and two are exhibited.

I now remove the slide of eel's scales for a few
minutes, and place that containing the selenite on the
stage, while the upper prism remains in the position
number one. The whole field of view, instead of
being simply colourless, appears of a rich yellow. I
begin to turn the prism — the yellow fades into white,
then this changes to pearl-colour, and then to brilliant
blue, by which time the prism has only revolved an
eighth. Continuing to turn the prism, I observe the
blue becoming pale much more slowly than was the
case with the yellow, and the prism has reached nearly
three-eighths of the way round before the field of
view has changed to white. Then it quickly changes
to yellow, assuming the brightest shade of that colour
when the prism is just half way round. Then blue
comes with speed as before, and slowly fades, till
yellow takes its place in the original position.

Now, leaving the selenite on the stage, I place the
eel's scale over it. What a richly-coloured object it
has become, all pink, orange, and green. Some traces
remain of the pair of Vs, which would appear there
if the selenite were absent, but instead of being jet
black they are orange, the inside of the Y;s is pink,
and the broad outer spaces are emerald green, while

Scales of Beetles and E

Plate 4.

C

1. Weevil, natural size. 2. Scales of Weevil, magnified 100 diameters.

3. Scales of Green Weevil, magnified UO diameters. 4. Scale of Perch, magnified 4 diameters.
5. Lines on Perch's scale, magnified 100 diameters. 6. Scale of Sole, magnified 9 diameters.

7. Piece of Eel's Skin, magnified 4 diameters.
8. Upper and under layers of Eel -skin, and Eel scales. 9. Scale of Eel, magnified 50 diameters.

Scales of Insects and Fish. 40

all around is the bright yellow background. As the
prism revolves the coloured portions of the scale seem
to revolve and change colour. When the selenite
appears blue the letter V's are blue, the angle inside
emerald green, and the exterior spaces deep pink ;
and this rotation of colours continues till the prism
has gone all round. Now this is the kind of effect
which the polarizing apparatus exhibits. The black
cross is shown on many objects, and the bright colours
appear in many others, with and without the selenite.
It is an exhibition which causes a good deal of plea-
sure and surprise, and I have often enjoyed studying
its phenomena. Yet in general I scarcely like to
bring it forward, feeling that the circumstances of
illumination under which objects are shown with the
polarizing apparatus are so peculiar, that I could not
answer the question, " Is it true ? "* with the same
unreserved affirmative that I should employ in vouch-
ing for the appearance of objects shown in ordinary
light. It may be asked, " Could not the principle of
polarization be explained at the time the objects are
shown, so that observers might take an intelligent
interest in the subject ? " To this I would answer
that some very deep principles of optics are involved
in the matter, and that the full explanation requires
a good deal of time, and would be unsuited alike to a
popular exhibition of the microscope, or to the plan
of a work like the present.

A few words might however be said to give a
general idea of the effect of polarization, and the

* See anecdote in the Preface.

4

50 The Microscope.

remarks in a recent work on microscopic objects are
so much in point that I will repeat them without
abridgment.*

" The effect of polarized light is not only beautiful
to the eye, but of real use to the investigator of
tissues, and in the researches of the pathologist, for
by it the true structure of organic bodies may often
be made clear, when the ordinary white light has
failed to develop it." Here I may remark that a great
number of structures are not acted on by polarized
light; for instance, the butterfly's wing partly divested
of scales, remains simply transparent during the whole
revolution of the prism ; and useful information may
be gained by observing whether an object polarizes or
not j and this holds good alike of microscopic revela-
tions and those of the telescope. The writer continues,
" Hardly in a concise manner can the question be
answered which is so often asked, 'Why are these
objects so coloured, and what is polarized light?'
But I may briefly explain that rays of light reflected
from a body under special conditions, or transmitted
through certain transparent crystals, undergo such
change in their properties, that they are no longer
subject to the same effects of reflection and refraction
as before.

" The common ray of light may be compared to
a glass rod, smooth and white, uniform in texture,
whilst the polarized ray is smooth on one side, rough
and dark on the other. How it becomes so requires

* From "Objects for the Microscope," by L. Lane Clarke.
Groombridge and Sons, London.

Scales of Insects and Fish. 51

too long a dissertation on the laws of light and colour ;
but so it is. And when this polarized ray is either
thrown upon or transmitted through various sub-
stances, it is either reflected, or absorbed and extin-
guished, according to the structure of the object
presented to it. The most brilliant colours are de-
veloped by this process, especially in crystals, feathers,
sections of quill, bone, hoof, horn. A good selection
of these objects is of value to the microscopist."

52 The Microscope.

CHAPTER VI.

HA IKS AND FEATHEES.

[HE scales of fishes, as Dr. Carpenter tells us,
are developed in the substance of the true
skin; whereas the scales of reptiles, the
feathers of birds, and the hairs of quadrupeds are
formed upon its surface, and allied in structure to the
epidermis or scarf-skin. They are essentially com-
posed of collections of cells, and form examples of
innumerable structures in which cellular formation
may be observed. In fact the microscope reveals to
us that all animal and vegetable structures are de-
veloped from cells, and the reader will find a lucid
and interesting account of their formation and changes
in " Hogg on the Microscope," p. 527, etc.

Hairs and feathers are formed and developed on
the same plan essentially. They both grow from a
root, by continual additions of cells to the lower parts,
which cells become elongated, and push the hair or
feather farther and farther upward; and thus it
lengthens. When we pull a hair up " by the root,"
we see a little bulb, which is filled with soft pulpy
cells, and this bulb corresponds to the quill of a
feather, also containing a soft pulp while grow-

Hairs and Feathers. 53

ing, the shrivelled remains of which in a full-
grown quill must be familiar to every one who has
mended a pen.

The quill of a feather, then resembles the root of
a hair; and in like manner, its stem, namely, the
remaining part of the feather, corresponds to the shaft
of the hair. When you have mended the same pen so
often that very little quill is left, you will observe by
cutting off its last remnant, that the stem of the
feather consists of a horny sheath enclosing a white
pith-like substance. These two parts have received
the names of the " cortical " and " medullary " sub-
stances ; and closely correspond with the component
parts of hairs, as shown by the microscope. The
minute size of hairs as compared to feathers is an
obstacle to our readily understanding their structure ;
on the other hand, the beautiful transparency of the
outside, or " cortical substance," enables us to view
them to great advantage when assisted by a good
microscope. The figures in Plate V. give representa-
tions of the appearance of various hairs when highly
magnified. Let us examine the first of them, namely,
the white mouse's hair, represented in Plate V., fig. 1.
Those who are shown it for the first time are sure,
after a brief survey, to look round appealingly for an
explanation of what they have seen, the object is so
unlike anything in their previous experience. It
resembles a number of beautiful glass rods of various
thickness, each containing a running pattern in its
centre. That running pattern engrosses all attention
at first; and next comes the question, why are tho

54 The Microscope.

hairs of such different sizes ? But this is never asked
till the first great puzzle is in some sort got over, as
to the curious running patterns, resembling a sort of
jointed chain in the larger hairs, and a simple row of
beads in the smaller. Let us therefore now study them
in the light of the remarks lately made on the structure
of hair, how that it generally consists of a cortical or
investing substance, of a dense horny texture, and a
medullary or pith-like substance, usually much softer,
and occupying the interior. Now in the hair of the
white mouse both can be very well seen j the apparent
glass rods are the cortical substance or rind of the
hair, and the chain-like patterns which they enclose
are the medullary substance or pith. This consists
entirely of cells, which vary in shape and arrangement
in the hairs of different animals. In the mouse you
see they are large and distinct, and arranged in rows.
In some hairs of the rabbit they lie like the grains on
an ear of Indian corn. In the cat they are closely laid
together, and this is the case also with the otter ; but
at this object I imagine you will pause and inquire,
"What is this scale-like appearance on the otter's
hair ? " and in reply I ask you to remember that
"all animal and vegetable structures are developed
from cells," and that the rind or cortical substance
of hairs has been formed by a succession of cells,
which at its surface become flattened into scales as
the hair grows.

The otter's hair shows this scaly structure to great
advantage.

The internal cells of the mouse's hair show in a

Hairs and Feathers 55

marked and interesting way the pigment cells on
which principally depends the colour of the hair. In
the hair of the white mouse (Plate V., fig. 1) these
cells cannot be perceived ; but in those of the common
mouse (fig. 2) there is a scrap of colouring matter in
each cell, and those little dark spots, seen through the
transparent surface of the hair, give to it its dark
colour. Yet how is it about the position of these
dark spots ? for when we compare figs. 1 and 2, we
observe that the remarkable projections (reminding
one of a succession of vertebrce) are alike empty in both
figures, the little blocks of colouring matter occupy-
ing the intervening spaces. Are these projections
then not cells after all, but solid partitions of some
kind ? No, they are air-filled cells ; we know this by
their appearance when the hair is mounted in balsam,
for they absorb light, and assume a dark and decided
appearance, just as the obnoxious air-bubbles which
so often annoy the microscopist when mounting
objects; and moreover we can often contrive by
heating the glass slide over a flame to get some of
the air out of the end of the hair, and completely
penetrate it with the balsam. Then the white mouse's
hair becomes nearly invisible, except about the point
where the balsam ceases to penetrate, and there a cell
or two remains only half full of air, resolved into a
round bubble ; and the brown mouse's hair shows the
portions of " pigment" standing out in beautiful
distinctness and regularity. It would seem that there
are two kinds of cell in the pith of the mouse's hair,
which we may call vacant cells and pigment cells, the

56 The Microscope.

former reminding one of a long corridor or gallery
with numerous recesses on either side, while the latter
would be represented by sundry glass cases filled with
valuables, standing at regular intervals on its floor,
and inserted in its walls. You will also see that the
dots of pigment in the finer hairs also are placed
between the strongly-marked " beads " instead of
within them ; and the mention of these finer hairs
brings us to another question often asked by ob-
servers, Why has the same animal apparently so
great a variety of hairs ? For instance in the otter's,
we see a large yellowish hair with brown centre, a
transparent hair with lengthened scales, and three
very small chain-like hairs. And human hair is of
many different diameters.

This apparent variety of size, which happens to
add a good deal to the effect of a group of hairs as
seen with high magnifying powers, is caused by three
different circumstances. Firstly, many animals have
two kinds, namely, firm and long hairs, and fine down.
Secondly, many hairs are somewhat flat, and therefore
look narrowest when seen edgewise. Thirdly, the
hairs of many animals are differently formed in dif-
ferent parts of their length.

The next remark may be that the distinctions of
rind and pith do not seem to hold good with all the
hairs. True enough ; and this sort of variety meets
us in many natural history researches. A general
rule is stated, and then the words "frequently,"
<f commonly," or, as the old adage has it, ' f almost
and very nigh," have to be put in to prevent mis-

Specimens of hair, magnified 200 diameters.

Plate 5.

1. Hair of White Mouse.

2. Hair (if Common Mouse.

3. Hair of llahbit.

Hairs and Feathers. 57

takes. For, observe the hair of the horse in which
the pith is narrow and interrupted in two specimens,
and altogether absent in a third, and some specimens
of wool, in none of which it occurs ; and on the other
hand, the hair of the fallow-deer, almost entirely made
up of cells, and in which the rind can only be seen as
a very thin layer at each side.

In that of the musk-deer (a few specimens of
which reached me, after coming in a letter from India
on chance of their proving interesting) the cortical sub-
stance may be said to be reduced to a minimum. For
I observe the hair to be composed from edge to edge
of angular cells (which have been well compared to
the cellular tissue of vegetables), and I miss the thin
layer of rind observable in the fallow-deer's hair.
But, adjusting the microscope so as to catch the exact
focus for this edge, a faint appearance of overlapping
scales can be detected. On again altering the focus
to catch the surface of the hair, I see the outside set
of cells terminating in a beautiful kind of network,
much resembling Gothic tracery, and very similar to
that of the fallow-deer, and in a specimen mounted in
balsam this appears to be the real outside of the hair.
But on examining one mounted dry I perceive the
scales as a film of utmost delicacy just concealing the
Gothic tracery slightly, as a piece of tissue paper would
veil the page you are reading if laid over it ; and the
overlapping edges of the scales appear very similar to
those on the broad parts of the otter's hair.

And now, as to human hair, about which I can
imagine the reader has been wishing to hear. Is it all

58 The Microscope.

rind or all pith ? Following Dr. Carpenter's account
of it, I have to state that it approaches most to the
latter condition, but is peculiar in its structure. When
the focus of the microscope is very carefully adjusted,
I can see a thin transparent layer edging each side of
the hair, just as in the deer's hair. Within this layer
is the cellular substance that constitutes the principal
part of the hair, the numerous straight lines marking
the form which the cells have taken. The hair owes
its hue to the pigment contained in some of the cells ;
and the grey colour which gradually steals through
one's hair, placing a line of silver here and there, is
caused by the absence of the pigment.

A section made transversely (that is, across, as
you would slice a cucumber, or cut a lemon in two)
shows the outer rind of the hair clearly as a trans-
parent structure. Occasionally there is a distinct line
of large cells in human hair in the centre of the small
and lengthened ones, giving an appearance somewhat
resembling that in the larger hair of the horse, and
some writers regard these as the only portion properly
called medullary ; but good reasons have been given
for considering both kinds of cells as equivalent to the
medullary substance in other hairs, and giving the
appellation of " cortical " to the thin transparent out-
side layer, and the delicate overlapping scales, which
show on a specimen mounted dry. The examination
of the root of a hair is easily managed, and interesting
when a high magnifying power is at command. The
root should be placed on a glass slide, with only a
small portion of the hair, and in a drop of water. A

Hairs and Feathers. 59

thin glass should then be laid over it, and gently
pressed down with the hand, or with some small im-
plement, as a pencil ; then the delicate rootlets extend
themselves, and the central bulb, somewhat like a
hollow lamp -wick, shows its complicated structure.
The reader who tries this experiment will certainly be
pleased and interested, and will perhaps, while ad-
miring the traces of design and contrivance in this
familiar object, remember the affecting words which
tell us, "The very hairs of your head are all
numbered."

Where minute investigation is not the object, hairs
can be shown in great beauty by light from the con-
densing lens, when they will appear glittering like bril-
liant chains on a dark background; or apiece of white
paper may be placed below them, which shows some
of them in a very pleasing manner ; and most of them
are suitable objects for the polarizing apparatus.

The hairs of insects are at all times familiar to the
collector of microscopic objects, as most preparations
of the limbs and heads of insects bristle with them in
all directions. Some of the longer hairs, however, as
those of the bee, cockchafer, etc., can be mounted
separately.

The feathers of birds show their cellular structure
best by selecting those which are very small and thin,
and mounting them in Canada balsam ; and another
suitable object will be found in the fine down placed
next the body of the bird.

Various brilliant feathers can be shown to some
advantage as opaque objects with the lower powers of

60 The Microscope.

the microscope ; yet, on the whole, it may be pro-
nounced that they are scarcely so agreeable to the
eye as when seen in their natural size. The homely
goose-quill affords an object likely to prove more
attractive to the intelligent observer, its point of
interest (in common with all firm and smooth feathers)
being the mode in which its barbs or fibres adhere to
each other. How often have I stroked the feathers of
a quill back and forward, and wondered why its fibres
parted so reluctantly ; and still more have I wondered
that it should be so easy to stroke them into their
places again !

A little investigation will explain the mystery.
I have arranged under one of the lower powers of
the microscope a very flat little feather, and I find
that it consists (as you know) of a central shaft, with
a great many barbs springing from it. These I will
call " minor feathers." On one side of the " minor
shafts " (as we may call them) there is a row of smooth
flat little filaments ending in tapering points. Except
for the tapering point it is not unlike a blade of a
knife in shape. On the other side of each of the little
shafts is a row of filaments, not ending in points, but
in a series of hooks.

When the feather is smoothed down, and all the
minute portions of it are in their places, it will be
observed that the " minor shafts " are very close
together, and the rows on each side of them overlap
each other. In this way every filament ending in a
series of hooks lies over three or four of the little
knife-shaped filaments in the neighbouring row, and

Hairs and Feathers. Cl

each of these latter is held in its place by several
hooks. Thus they are not easily pulled asunder, and
the last thing to yield is the tapering point which the
hooks pass with a jerk.

You will also see that the tapering points belong-
ing to the filaments turn up a little ; this adds to
the firmness with which the latter are held by the
hooks. The hooked filaments are set near the upper
edges of the plank- shaped shafts ; the knife-like fila-
ments on the opposite sides are lower down, and both
stand out very stiffly.

Thus the natural position of these hooks is above
the neighbouring row, and duly fastened to it. When
we begin to smooth down the feather, the filaments
cannot fail to clasp each other. They do it, like a
released spring, in the act of straightening themselves,
and when they have resumed their natural shape the
feather has regained its beautifully level smoothness.
Such are the curious self-acting hooks on the feathers
of birds.

62 The Microscope.

CHAPTER VII.

EYES AND OTHEE OBJECTS.

|HB boiled eye of a fish provides an object
singularly well-adapted to the higher powers
of the microscope, and one which can
be prepared with little difficulty. Probably some
of my readers in their childish days, seeing
a cod-fish or haddock placed on the dinner-table
as a head dish, have begged for one of its eyes
— not the whole jelly-like mass, but the pretty white
thing inside, the size and shape of a marble. The
prize gained, they have — if old enough to be trusted
with a penknife — cut away the white brittle outside
of the ball, and discovered the beautiful little trans-
parent sphere within. And then they have found that
they can peel a transparent delicate rind of fibres off
this little sphere, but only to find beneath it another
layer exactly similar, and another below that, and so
on till it becomes almost too small to hold. Our
present business is with this little sphere and its
peelings.

I will suppose that I have placed a few of these
on a glass-slide, and have fastened a thin glass over
them, as they would quickly become brittle if left

Eyes and other Objects. 63

exposed. But before you look at their appearance
when magnified, shall we pause for a few minutes to
inquire what place the white ball occupied in the
economy of the fish's eye ? and what was the jelly-
like mass which surrounded it ? Both may well occupy
our attention, as having united to form that most beau-
tiful piece of mechanism, an eye. The jelly-like mass
is the dismantled frame-work of an exquisite minia-
ture camera-obscura, of which the little white sphere
(transparent till boiling rendered its outside portion
opaque) was the lens : for the eyes of fishes, as well
as our own eyes, and those of all the other verte-
brated animals, are constructed on a plan exceedingly
similar to that of the camera-obscura. Its plan is not
difficult of comprehension; here I speak not of its
portentous form as a photographic engine, but when it
is literally a dark room for the exhibition of a land-
scape. It was first described so long ago as 1589, by
a Neapolitan philosopher, Gianbattista Porta; his
first plan was a simple dark room, with a closely fas-
tened shutter, in which a small hole should be made,
and the light permitted to fall on a white screen or
wall ; for he found that an image of the outside view
would be thus obtained. And that this effect would
follow, we can easily show, by holding a card pierced
with a round hole near a lighted candle, when we shall
see an image of the candle flickering on the wall, in
the card's shadow. But Porta bethought him of a
great improvement in his dark room contrivance, and
states it as a secret, which he had long concealed, and
had at one time intended always to conceal, that if a

(34 The Microscope.

convex lens be applied to the aperture, all external
objects will be shown in the vivid brightness of
nature, so " that those who see it can never enough
admire it/'

We can imagine the astonishment and delight of
the earlier spectators of Portals camera-obscnra ; but
what would have been their amazement to be told
that they themselves, and every bird, beast, and fish,
already possessed two optical instruments similar in
principle, and far superior in refinement of construc-
tion.

The eye-ball is a little room, nearly spherical in
its form ; its outside wall is white, except at the front,
where it has a large, round, and slightly-projecting
window, called the cornea ; much like a watch-glass.
Behind this window is a permanent circular blind,
with a round aperture in its centre ; this is the Iris,
and the aperture is called the Pupil, and if you look
through it and try — disregarding your own chubby
image on the cornea — to get a glimpse of the little
room's interior, you will see that this is lined with
black, as every camera-obscura is or ought to be
to prevent confusion and indistinctness from double
reflections. The white outside circle is what I have
called the outside wall, and you can see at the left
where it is interrupted by the cornea, behind which
you can make out the section of the iris and its aper-
ture. The cornea is kept distended by a fluid like
water, and a similar purpose with regard to the rest
of the eye is served by a jelly-like transparent sub-
stance, called the vitreous humour. The line imme-

Eyes and other Objects. 65

diately surrounding this is the black lining of the eye,
and the remarkable structure suspended in the
vitreous humour, not in its centre, but near its front,
is the crystalline lens — spherical in fish, but of the
form called double-convex in man and in various
lower animals. The shaded appendage at the right
of the eye is the optic nerve, which expands inside the
eye-ball into a delicate cup-shaped membrane called
the retina, exactly answering to the slightly concave
round table inside a landscape camera.

I have seen all this mechanism shown with a cow's
eye, cleverly arranged by a physician, who exhibited it
to a large party. The front view of the iris in a
detached eye is not a very agreeable sight; but I
believe most of the lookers-on forgot its unpleasant-
ness when the section of the eye was made, and the
crystalline lens displayed in its brilliant polish and
transparency

The lenses in our own eyes (according to an in-
teresting article in the "Penny Cyclopaedia") are
" composed of an infinite succession of thin concen-
tric laminae, arranged with the utmost regularity one
within another, like the coats of an onion, and every
such stratum or elliptic shell is made up of a series of
exquisitely minute fibres laid side by side." The
writer goes on to say that similar though not precisely
the same arrangements are observed in the eyes of
other animals ; and that in fish these fibres f ' are
curiously hooked together by fine teeth." The lens
is always enclosed in a delicate skin or capsule — this
can easily be made out in the boiled eye of a fish ; so

5

66 The Microscope.

can another circumstance, believed to be very import-
•int to the optical perfection of the eye, namely, that
its lens, composed all through of a substance princi-
pally consisting of albumen (like white of egg),
gradually increases in density from its surface to its
centre. And now let us see these curious peelings,
which are no other than collections of the fibres above
described.

One of these layers, which extend from top to
bottom of the lens, like the meridians on a globe, and
in the cod-fish, haddock, and many others, meet at
points to which the name of ' ' poles " has been given.
Magnified six diameters, as you will see, nothing
remarkable appears. There are some indications of
its being covered with fine lines, so we will there-
fore examine them, magnifying them 130 dia-
meters.

They now appear on every part of the layer, and
are beautifully regular. Look at the real size of the
fragment, and think how delicate these lines must
be!

We can just distinguish that they are waved lines
with a magnifying power of 100 diameters; but we
see the real form of the lines very distinctly on mag-
nifying them 670 diameters. Every line is toothed in
this way, and every fibre which your pen-knife strips
off the lens, could be divided into as many narrow
pieces as it contains lines. I have frequently torn
them into minute threads, which proved to be single
fibres, or two or three together. The little teeth lock
into each other, very much in the manner in which

Eyes and other Objects. 67

the outside portions of a " dissected map " are fastened
together.

These lines present slight dissimilarities of appear-
ance in the lenses of different kinds of fish, and speci-
mens of a number might gradually be collected. Op-
ticians also supply interesting preparations preserved
in fluid, of the minute fibres from the eye of a cow
and other animals, also of the iris, and the black pig-
ment lining of the eye-ball. I have before me as I
write, a specimen labelled " Fibre of Lens of Human
Eye," and I naturally view it with interest, mingled
with reverence, because it once formed part of that
which has been aptly named the " window of the
soul/' It consists of a multitude of separate fibres,
broader than those of the cod-fish, and with compara-
tively smooth edges, exhibiting, however, sufficient
roughness to enable them to catch the edges of the
neighbouring fibres.

These fibres, it is stated, converge in the human
eye to a Y-shaped figure instead of to poles, as those of
the cod-fish do. The fibres in a trout's lens meet at
straight lines, and various other forms have been ob-
served and noted.

A considerable resemblance to the plan which has
just been imperfectly described may be traced in the
eyes of crustaceous animals, as the crab and lobster,
in those of insects, of spiders and other creatures.*
There may be the greatest diversity of arrangement :
the eye may be fixed or movable, single or immensely

* See Dr. Spencer Thompson's interesting work on " The Struc-
ture and Functions of the Eye." Groombridge and Sons.

68 The Microscope.

multiplied; yet something will generally be found
answering to the lens, the retina, and the pigment.

The eyes of the dragon-fly, cricket, and lobster,
all resemble each other in being composed of a very
great number of minute lenses joined into a single
group, each one of these lenses being (according to
the best naturalists) "a distinct organ of vision."
The lenses are arranged side by side in a form that
allows of their being close together without loss of
room.

If they were in circles a great deal of space would
be wasted, and so there would be also were they
eight-sided. But they are usually formed with six
sides, just the same shape as the cells in a honeycomb,
so that no room whatever is lost. Naturalists have
counted twelve thousand lenses in each eye of the
dragon-fly. These lenses can be mounted in such a
way that they will keep their shape.

It may sound like a difficult thing to count so great
a number ; but they are arranged with such extreme
regularity that their amount is readily calculated.
Magnified 36 diameters, they are like a piece of lace ;
and there is another thing which they also much re-
semble— the wire-netting that is often put round
garden plots to keep out rabbits, just like gigantic
lace with holes about the size of half-crowns.

Let us imagine an. experiment with a piece of this
wire-netting. Suppose we should provide ourselves
with several dozens of round spectacle-glasses, and
set one in each of these holes, and hold the piece of
wire-netting at a certain distance from a wall — the

Eyes and other Objects. 69

effect would be that we should see on the wall several
dozens of pictures of whatever there was behind the
lenses. Now, with the solar or oxy-hydrogen micro-
scope, a result very similar to this can be obtained
with an insect's eye. With the former instrument, as
already described (chapter 1), the shadows of objects
can be shown (when the sun shines) on a white screen
held up to receive them. And when I place a scrap
of the dragon-fly's eye in the solar microscope, I see
in every compartment of its shadow a brilliant point
of light, which is a little picture of the sun.

This proves them to be lenses ; and it can be shown
in another way. If we had a piece of wire-netting
with spectacle-glasses mounted in its holes, and we
held it between our eyes and a window, we should see
a great number of little windows, and whatever view
appeared through them, just as many as our machine
contained of spectacle-glasses. If we held our eyes
too close to it we could see the net-work well enough,
but the view through it would be hazy. By removing
our eyes farther off we should see the little pictures
quite clearly.

We can imitate all this with a scrap of dragon-fly's
eye ; the piece I select contains about fourteen lenses.

I am sitting in a room opposite a window, though
at some distance from it. The window is thrown
up nearly as high as it will go, and there is an old
arm-chair standing close to it at the left-hand side.
Through the window I can see a range of farm- offices
with a slated roof; there is an archway in this range
of buildings, and over it an old carved stone is let

70 The Microscope.

into the wall. There is a large elm-tree beyond the
buildings, and I can see its branches over the roof,
standing out against the sky. I have the microscope
on the table before me, inclined as much as if it were
a telescope, and facing the window, and I arn looking
through it at the scrap of a dragon-fly's eye, with a
magnifying power of 250 diameters.

First, I screw the microscope very close to it, that
I may see the beautiful hexagons clearly. Next, I
gradually move the microscope a little farther from
the object ; the hexagons now become indistinct, and,
as it were, melt into each other, but in the centre of
each appears every particular of the view I have just
described ! There are the sashes of the window, the
arm-chair, the slated roof, the archway, the carved
stone, and the distant tree !

A sight of this singular object suggests various
questions to the mind of the thoughtful observer.
How did the insect see through all these eyes ? Why
did it possess such an extraordinary number ? and, To
what part of our eyes did these numerous little lenses
correspond ? A few words then may be acceptable
on the structure of insects' eyes.

The hexagonal lenses correspond to the combined
action of the crystalline lens and cornea of our own
eyes. Behind each of them is a little " dark room,"
not spherical, like ours, but shaped like a very long
hollow cone or pyramid. These thousands of pyramids
are all completely isolated, from each other by layers
of dark pigment, and at the inner extremity of each
there is a delicate filament, which is no other than a

Eyes and other Objects. 71

branch of the optic nerve, and its position is exactly
at that distance from the lens at which experiment
has shown the proper focus would be found. Thus
we see in these eyes arrangements closely correspond-
ing to the lens, black lining, and retina of our own ;
there is also a resemblance to be found to the iris
and pupil, as the pigment closes in behind each lens,
leaving only a small aperture. And by all these con-
trivances, the rays which have passed through the
several lenses " are prevented from mixing with each
other ; and no rays, save those which pass in the axis
of the pyramids, can reach the fibres of the optic
nerve/'* It is therefore believed that in looking at
an object, an insect can see clearly only the point
exactly opposite to the centre of each lens. "The
image on the retina may be compared to a mosaic
composed of a great number of small images, each of
them representing a portion of the object seen. The
entire picture is, of course, more perfect in proportion
as the pieces are smaller and more numerous.'^ And
the reason why the dragon-fly (as well as other insects)
has so great a number of eyes may well be concluded
to be this — that its eyes are not capable of turning
round, as ours are, but being supplied with this pro-
digious number, the greater portion of its head being
studded over with them, it suffers no inconvenience
from having them fixed and immovable, as it is thus
enabled to see at once in almost all directions.

The interesting structure, above described, of the

* Carpenter's " The Microscope and its Revelations," p. 672.
f Agassiz and Gould's " Comparative Physiology," p. 70.

72 The Microscope.

interior mechanism of an insect's eye can be examined
in a section, mounted in fluid; its preparation is a
matter of much nicety, but the outer lenses (also
known as " corneules") are hard and easily managed.
They require only to be washed at the inside with
water, applied by a camel's-hair brush, which removes
the fibres and pigment. The whole of one mass of
lenses can be detached with a pair of scissors, and
when washed, can be mounted by nicking its edges to
make it lie flat. It is then ready to examine with one
of the lower powers of the microscope, and I know no
more extraordinary and splendid object. It is really
like twelve thousand well -polished lenses, beautifully
precise in their hexagon forms about the front part of
the mass, and largest there ; while their form accom-
modates itself to their position near the edges. The
arrangement of light known as " back-ground illumi-
nation," shows this object in peculiar splendour. Some
additional apparatus is supplied for affording this sort
of illumination; but even without this addition, the
effect can be produced sufficiently for many purposes
by placing the lamp as low as possible, and at some
distance from the stage, and throwing light upwards
with the condensing lens placed obliquely, so that no
rays reach the observer's eye except those that are
caught by the object, which accordingly appears in
extreme brilliancy on a dark field of view.

To show the experiment of the multiplied views, a
very small fragment of the eye will be found most
convenient, and different little pieces of management
must be used to add to the effect. It is well to have

Eyes and other Objects. 73

but one window in the room, or to darken the others ;
to choose one which commands a few conspicuous
objects, and to close its shutters slightly, so as to
avoid the glare from their panels. The microscope
must be raised on a box, and put as near to the
horizontal position as it can be without causing the
slide to fall against the object-glass ; or this result may
be prevented by fastening the slide to the stage with
elastic bands, or an atom of wax. I have tried to
devise a plan for showing the action of the lenses by
lamp-light ; and can recommend that of inclining the
microscope raised on a box as for the daylight experi-
ment, and looking directly at the shade of a modera-
teur lamp, on which some device, cut out in black
paper, is temporarily attached — for instance, two
initial letters, about an inch and a half in height, cut
from a printed placard. They are to be seen repeated
in beautiful clearness all over the object, and like the
little views, in their true position, not inverted, for the
very interesting reason that each lens is acting as an
additional object-glass to the microscope.

A similar experiment may be shown with the eyes
of most other insects, but scarcely so conveniently
with any as that of the dragon-fly, its lenses, especially
at the front of its eyes, being larger than those of
most others. A considerable difference will be found
in the number of lenses belonging to insects' eyes.
It is calculated that the ant has 50 lenses, the house-
fly 4000, while as many as 34,650 have been counted
by the naturalist Geoffroy in the eyes of a but-
terfly.

74 The Microscope.

Where these are few in proportion to the size of
the eye, they are less regular in shape than when they
are numerous. This appears in the eye of the cricket.
The irregularity appears most near the edge,, where it
takes a sudden bend, and where a set of regular
hexagons could not pack together ; and still nearer
the edge, some of the lenses have only five, or even
four sides.

Crabs' eyes are composed of hexagons ; those of
lobsters and shrimps of squares.

The eyes of lobsters, crabs, etc., are mounted on
a foot- stalk, so that they are rather more movable
than those of insects. They are, however, smaller in
proportion to the size of the creature's whole body
than those of insects usually are.

And now, passing from the mechanism of the eye
to the multitude of other wonders from the animal
kingdom, to be observed in any good collection of
microscopic objects, we naturally feel embarrassed with
riches. See them all — understand them all — would
be the aspiration of many an enthusiastic microscopist ;
and no unworthy wish, nor one altogether unattain-
able when the privilege of leisure time is added to
the advantages of a good microscope, well-prepared
objects, good books of reference, and the requisite
amount of industry and intelligence.

I will conclude this section by an account of three
curious feet — those of the common spider, the house-
fly, and boat-fly, the two latter being insects properly
so called, and the former belonging to the more highly
organized family of the Arachnidce.

Eyes and other Objects. 75

The last joint of the spider's foot generally termi-
nates in two or three hooks or claws, with comb-like
teeth, as you may see in Plate VI., fig. 1. Fig. 2
represents them on a larger scale — they are shown
as "transparent objects/' and for this reason you
can see part of the far claw through the centre
one.

This group of claws has been well described as
a " sensitive small hand, which twists, and spins,
and weaves, and builds nests for its young, and
snares for its food/'* It is also observed to be a
cleaning instrument. A spider has been seen to
spend an hour or more in scraping the delicate
threads of its web, when dust or soot had collected
on them ; and if they were too thoroughly incrusted,
these little claws broke the thread, rolled it up, and
threw it away.f

What a different foot is the fly's ! (Fig. 3.) It
is an object almost certain to be found in any micro-
scopic collection, however small; and yet there has
been considerable uncertainty about the nature of its
mechanism.

Naturalists have always wished to explain how
flies can walk up a window, or even upside down on
the ceiling of a room ; and there is no doubt that the
curious flat appendages at the last joint of the foot
enable them to do so. These appendages appear to be
of the quality of parchment, and air-tight, and the

* On the " Feet of Arachnidse." By L. Lane Clarke. " Intellec-
tual Observer," April, 1863.

f See " Objects for the Microscope." By L. Lane Clarke, p. 65.

76 The Microscope.

theory which was long held about them was this —
that they are suckers ; that the air presses on them,
and that no air can get under them, as a vacuum
is formed beneath by the raising of their central
parts.

There appears much to be said in support of this
theory, and the sucker is an instrument by no means
unknown in nature. The feet of a lizard — called the
Gecko — are supplied with a contrivance of the kind,
and this is also the case with some of the water-
beetles; I have seen one of them hold on quite
tightly to the edge of a basin by means of the suckers
on its feet. It would appear, however, that the fly
cannot f c support its position 3} in this way. An acute
observer of nature, Mr. Blackwall, at Manchester,
noticed that flies under the glass of an exhausted air-
pump were still able to adhere to it, and, in fact,
could not be detached without the employment of a
small degree of force. This observation led to many
experiments being tried; and it was found that the
adhering power exists, not exactly in the flat append-
ages, or pulvilli, but in the minute hairs which sur-
round them, and, being tubular and terminating in
minute disks, partly act as suckers, and emit a fluid
which makes the adhesion perfect.*

Fig. 4 represents a foot of the boat-fly, so called
from its rowing itself in the water with a pair of feet
much resembling oars. This is one of its hind feet,
and it will be observed that, besides being very flat,

* See Mr. Hepworth's communications to the " Quarterly
Journal of Microscopic Science," Yols. II. and III.

Eyes and other Objects. 77

it is fringed with long fine hair, which adds consider-
ably to its force as an oar. The insect (fig. 5) is a
very singular one altogether, and very common in
ponds all the year round, I believe j at least, I have
seen it in January composedly rowing about under the
ice. It is amusing to watch its movements when at

No. 6.— Whirligig Beetle.

liberty; its natural position, when at rest on the
surface of the water, is like that represented at fig. 6,
floating on its back, with oars stretched out, and
bright eyes on the alert, so that, on the approach of
an enemy, it can quickly dive below with a few
powerful strokes. It can also fly, as represented in

78 The Microscope.

fig. 7, and possesses a weapon of defence, in the
shape of a pointed beak or proboscis, capable of in-
flicting a very sharp prick. Like the house-fly, and
scores of other insects, this single specimen would
afford a considerable number of microscopic objects.
The same may be said of the little Gyrinus, or
whirligig beetle, the wing of which is already figured
(Plate II.) .

A woodcut of the whole insect is given on p. 77,
magnified eight diameters. This little beetle, the length
of which is about a quarter of an inch, is particularly
worthy of close examination, from the various appli-
ances with which it is endowed to provide for the
wants of its aquatic life, and from the rare beauty
and finish of every portion of its structure.

Vegetable Productions. 79

CHAPTER VIII.

VEGETABLE PRODUCTIONS.

REMARK in Hogg's "Treatise on the Mi-
croscope" shows the important part which
that instrument has performed, in adding to
our knowledge of the vegetable world : " Since the
introduction of the achromatic microscope," he says,
" we have obtained nearly the whole of the valuable
information which we now possess relative to the
minute structure of vegetables." The discoveries
which have been made in this branch of study are
detailed in a most instructive manner in that work,
and in Dr. Carpenter's, and would probably give
some help even to an advanced student of vegetable
physiology ; while, to those who know nothing of
plants beyond their external beauty, they impart a
half-depressing glimpse of the world of truth un-
known to them, and yet discovered by the diligence
of others. Yet an attentive study of their observa-
tions on a few familiar microscopic vegetable objects
gives much additional interest to a subsequent exami-
nation of them.

As mere objects of display, few things give more

80

The Microscope.

pleasure to the young than the exhibition of whole
flowers (small ones, of course,) with the lowest power
of the microscope. Some little weeds rise to the
apparent splendour and importance of hot-house
plants ; almost any weed, blossom, or grass is worth
looking at, and sure to delight the younger ones of a
family, while it suggests to them how well worthy of
examination are the common things by which they
are surrounded ; a thought which may prove of great
value to them at a future day.

No. 7.— Additional Object-glass for viewing Flowers.

I found the lowest power of my microscope still
too powerful to show as large a field as I desired, and
I therefore made a (somewhat indifferent) extra object-
glass., to magnify about twelve diameters, by simply cut-

Vegetable Productions. 81

ting a round hole in a cardboard box, blackening the
latter, placing a lens inside, and slipping it on to the
lower end of the tube (No. 7). It answered exceed-
ingly well for opaque objects, though showing its non-
achromatic short-comings when used with transmitted
light.

For the benefit of those who wish to go deeper
into the interesting subject of the structure of
plants, I will name a few of the most characteristic
objects which can be procured from the vegetable
kingdom.

Cuticles. — The cuticle is that transparent skin
which peels easily off the leaves of the lily, and
various other plants, and off the petals of flowers.
The microscope shows that it is formed of one layer
of cells, containing air, and serving to protect the
fluid-filled cells within ; yet, as these latter require
the entrance of a due proportion of outer air, the
cuticle is fitted up with ventilators in the form of
pores, called the stomata, curiously arranged to open
and shut.

The internal cells of plants. — " The origin of every
plant is a single cell ; the perfection of a plant, from
the tiniest moss to the loftiest oak, is in a countless
multitude of simDle cells, containing various sub-
stances needful for its growth, and of an infinite variety
of shape and substance."*

Cell- contents. — Starch-granules abound in the cells
of a good potato, and (according to Dr. Carpenter)
" in some part or other of most plants." Oil is con-

* " Objects for the Microscope," p. 13.

6

82

The Microscope.

tained in the well-known red globules stilted on little
stalks on the stem of the moss-rose. It is also to be
found in some internal cells in an orange-rind, and in
the leaves of the myrtle and magnolia. Some plants
contain crystals in the ceils of their cuticles ; the
hyacinth affords an example. Wax, gum, and sugar
are also to be detected in cells.

The rotation of cell-contents is one of the most

No. 8. — Vallisneria spiralis ; (a) the plant growing in a jar of water ;
(b) portion of the leaf, magnified.

curious and beautiful spectacles afforded by the micro-
scope. The best examples of it are found among
plants which grow under water; and of these the
Vallisneria spiralis is peculiarly fitted for its exhibition.
The Vallisneria is an aquatic plant that grows abun-

Vegetable Productions. 83

dantly in the rivers of the south of Europe, but is not
a native of this country ; it may, however, be readily
grown in a large glass jar with a little mould at the
bottom, No. 8 (a) . Its long grass-like leaves are too
thick to allow the transmission of sufficient light
without some special preparation. It is, therefore,
requisite to make with a sharp knife a thin slice
or shaving of the leaf, not of the outer surface,
but of that next to it ; and this must be placed in a
little water in the live-box. A power of 200 dia-
meters should be used. The whole field of view will
then appear occupied by cells similar to the small
number figured at No. 8 (6), with bright green par-
ticles revolving in each, in a steady and regular motion,
strictly limited to the boundary of each cell. It some-
times happens that the slicing operation will have put
a temporary stop to the rotation ; but a slight
warming of the live-box will quickly cause it; to re-
commence.

Spiral fibre. — A substance often deposited in the
interior of cells, tightly coiled up till a little moisture
applied causes it to uncoil suddenly. It can be very
curiously shown by cutting a thin and small slice off
the outside of a collomia seed, and placing it in the
live-box of the microscope, with a magnifying power
of about sixty diameters. The cover of the live-box
should be placed over it at first without water, that
the focus may be nicely arranged. Then the cover is
to be lifted up, a small drop of water put on its
under surface, and this pressed down over the slice
of seed. This being done, the spirals will spring

84 The Microscope.

out in all directions with a strange appearance,, as if
of life.

Woody fibre. — To be seen by examining thin sec-
tions of wood, of which beautiful specimens can be
procured from opticians, and in which may be traced
the process of their formation. Sections of roots and
stalks are also interesting.

Hairs. — These are formed of lengthened cells ;
the variety in their forms is wonderful, and many of
them are objects of great beauty. For instance, the
little purple tuft of them in the centre of the spider-
wort looks like numerous strings of amethysts of
oval shape — that in the centre of the scarlet verbena
like a tiara of pearls. The rotation of cell-contents
can be observed in some of the finer hairs of the
spider-wort, as well as in those of dock and
groundsel.

Pollen. — The fine powder which is to be seen on
the anthers of full-blown flowers, has long been known
as an excellent object for the microscope. It can be
mounted on slides, but looks best when fresh — best of
all when scattered on the velvet-like petal of the
flower to which it belongs.

Seeds. — Many of the smaller seeds are beautiful
objects in their natural state for the lowest power of
the microscope, being sculptured with sundry pits,
knots, and network patterns. Some are furnished
with wing-like and other appendages, which can be
highly magnified with good effect; and the outside
fibres of many are interesting ; for instance, the col-
lomia, already described, and the outer covering of

Feet of Insects, Petals of Geranium, etc.

Plate 6.

1. Foot of Spider, magnified 18 diameters. 2. Claws of Spider, magd. 100 diams.

3. Foot of Fly, magd. 20 diams. 4. Foot of Boatfly, magd. 4 diams.

5. lioatfly. 6. Boatfly floating. 7. Boatfly on the wing. 8. Petal of Geranium.

9. Piece of Geranium Petal, magd. 8 diams. 10. Minute portion of Petal, magd. 150 diams.

11. Pollen of Clarkia. pulchella, mag. 100 diameters. 12. Pollen of Crown-imperial, im:g. 100 diams.

13. Grain of the above, magd. 300 diams. 14. Pollen of Salvia patens, magd. 100 diams.

Vegetable Productions. 85

wheat and grass- seeds, known as bran, and composed
of remarkably regular and dense cells, which continue
distinguishable even after the grain has been roasted
and ground.*

Ferns, mosses, sea-weeds. — These examples of the
lower orders of vegetation are all particularly suited
to microscopic research ; so also are those vegetable
growths, familiar to us under the names of fungus,
mildew, blight, and mould ; as well as certain micro-
scopic vegetables found in water — the desmids and
diatoms, interesting as being on the border-land
between the lowest form of vegetable and of animal
life, showing a singular power of locomotion which
has caused many naturalists to describe them as
animalcules, till subsequent researches have seemed to
prove their vegetable nature.

It will be seen that a few of the objects referred
to in the preceding list, are figured in Plates VI. and
VII. In the former, fig. 8 represents the petal of a
geranium, which, when viewed without the micro-
scope, appears of a beautiful shaded pink colour.

Fig. 9 represents the little space marked A in fig.
8, as it appears when magnified eight diameters ; and
fig. 10 shows an extremely small portion of it — such a
piece as might be enclosed as in a frame in the eye of
the finest needle — as seen through one of the higher
powers of the microscope. The points in the centres
of the interstices are of a very deep rich red ; the
rays proceeding from these points are of a lighter

* Carpenter, p. 451.

86 The Microscope.

tint, and so also are the lines of the network of
cells.*

Fig. 1 1 represents the pollen of " Clarkia pulchella."
A small quantity of it looks, when highly magnified,
like an immense heap of glass rings, of three-cornered
form (fig. 11). That of the crown imperial is more
like grains of wheat. Fig. 1 2 represents some of this,
and fig. 13 shows some of the grains, magnified 300
diameters ; and it is wonderful to observe that their
surfaces are covered with a delicate pattern, just
perceptible with this high magnifying power.

The pollen of " Salvia patens " is flat and round
(fig. 14). These pollen-grains can be viewed either
as opaque or transparent objects. They appear to
great advantage by the "background illumination,"
described at page 72. A single grain of the pollen
of " Salvia patens " happening to be alone in the field
of view, with a dark background, curiously suggests
the planet Jupiter to one's mind, with its round yellow
disc, and belts stretching across.

The figures of Plate VII., with the exception of
fig. 10, might be said to represent "the seed-vessels
observable on the backs of fern-leaves/' But so
different in structure are ferns from the true flowering
plants, that the expressions "leaves" and "seeds"
are not considered admissible in these days of careful
investigation, when objects are no longer classified by

* It should be observed that the drawing (Plate VI., fig. 10) was
made from a dried specimen, in which the lines of the network are
more sharply marked, and the different shades of red appear more
detached from each other than in the fresh petal.

Seed-vessels of Ferns, and Section of Limestone.

Plate 7.

I. Seed-vessel of Fern when unripe, magnified GO diameters. 2. Seed-vessel of Fern, at the
moment when the ring straightens itself. 3. Leaflet of liluck Maidenhair Spleenwort Fern.

4. Two sori, or collections of seed-vesse.s, of Spleenwort Fern, magd. 12 diams. 5. Sorus of

Hart's-tongue Fern, magd. 6 diams. 6. Tart of a leaflet of Shield Fern.

7. Sorus, magd. 10 diams. 8. Sori of 1'olypody Fern, magd. 7 diams. 9. Sori and part of

leaflet of Hare's-foot Fern, magd. 5 diams. 10. Thin section of Limestone, magd. 20 diams.

II. Group of twenty seed-vessels, natural size. 12. Group of twenty seed-vessels, magd. 6 diams.

13. Leaflet of Polypody. 14. 1'art of a leaflet ol Hare's-foot Fern.

Vegetable Productions. 87

mere external characteristics. It appears that we
should say " fronds " and " spores/' because the
former are produced in a different manner from the
leaves of other plants, being rolled up in a crosier-like
form, which gradually unfolds, and the spores do not
by any means correspond to seeds, seeing that in their
nature they rather resemble buds; as in due time,
when placed on a damp surface, and exposed to suffi-
cient warmth, they enlarge by the addition of cells,
and produce singular structures somewhat agreeing in
nature with the stamens and pistils of flowering plants.
These curious facts, discovered in 1848, by Count
Suminski, are described with beautiful figures in the
work of Dr. Carpenter. We see the bud-like spore,
the elongating cells, the structures that have been
likened to stamens and pistils; and there are also
strange moving filaments, which may be likened to
pollen-grains ; but fern-seed itself appears to be even
more unattainable than it was considered in Shaks-
pere's time,* for there is indeed no such thing,
nothing which truly corresponds to the idea of a
seed, as we understand the term in speaking of most
other plants.

Almost all ferns have their seed-vessels, or to
speak more precisely, their thecce, on the backs of the

* "We have the receipt of fern-seed, we walk invisible." — K.

Henry the Fourth, Part I. Act II. " Fern-seed was supposed to

have the power of rendering persons invisible. The seed of fern is
so small as to escape the sight ; to find it, therefore, was supposed
to require a magic operation ; and in the use, the seed was sup-
posed to communicate its own property.— Note in "Illustrated
Shakspere," vol. iii. (Tyas.)

88 The Microscope.

fronds. These vessels are exceedingly small — smaller,
indeed,, than the seeds of most plants — and they are
arranged in a great variety of ways in the different
kinds of fern ; but in nearly all ferns they are globular,
contain a number of extremely minute spores, and
grow from the back of the frond on a curiously -jointed
stalk, and this stalk runs up one side of the theca, and
bends round it like a ring.

This ring is elastic, and so long as the spores are
unripe, and the theca soft and green, it maintains
its bent shape, and acts as a band. But when the
theca becomes stiff, and the spores ripe, the elastic
ring suddenly straightens itself with a great jerk,
tears the theca open, and scatters the tiny spores in
all directions ! Plate VII., fig. 1, represents one of
the thecae of a fern, called the Black Maidenhair
Spleenwort ; and fig. 2 a similar theca with the ring
in the act of straightening itself.

I have often brought a number of fern-fronds into
the house to examine while fresh with the microscope ;
and as the heat of the room hastened their drying, the
rings soon began to straighten themselves, the thecas
to tear, and the spores to scatter about. I have
shown this to friends, and been asked, " What are
those live things ?"

Fig. 3 shows part of the frond, of the size of the
original ; the slit-like marks are the groups of theca3.
In fig. 4 one of these groups of thecas and part of
another are shown magnified twelve diameters. From
this an idea may be gained of the animation of the
scene.

Vegetable Productions. 89

Each group of thecse in the tribe of spleenwort
ferns is protected on one side by a " cover," as it
is called, shaped somewhat like one half of a pea-
pod. -Another fern called Hart's-Tongue, a strong,
large, showy plant, somewhat resembling dock, has
two covers, one on each side of the group (fig. 5).
The Common Polypody fern has no covers at
all; its theca3 stand up in round groups, very like
heaps of oranges, their colour being bright yellow
(fig. 8).

The " Shield-fern," common in dry ditches, has
its " cover " constructed not unlike a little umbrella
standing up in the centre of each group of thecge.
Fig. 6 represents part of a leaflet the size of nature,
and fig. 7 one of the groups of thecae magnified.

There is a very great diversity in the shape of
these <e covers," and a collection of the native ferns,
arranged for the purpose of showing these, forms a
beautiful series of objects for the microscope. They
should be gathered before they are quite ripe, and
placed at once in blotting-paper to dry, if the object
is to mount them as slides for the microscope; in
which case some sort of little raised frame must be
placed on the glass, as without this the thickness of
the specimen would prevent the covering-glass from
being easily fastened down.

But ferns examined in a jresh state are objects of
great beauty, and are readily prepared, as nothing
has to be done farther than to lay a portion of the
frond on the microscope's stage. The richness of the
greens and browns will attract the eye pleasantly;

90 The Microscope.

and the soft juicy appearance of the theca3 when
unripe, the pretty effect, when, farther on in the year,
some will be unripe and pale, some ripe and dark in
the same group, and the fairy-like aspect of a group
of thecee when they are detached with the cover, and
placed in view like a miniature dish of fruit, are all
sights sure to gratify the beholder.

The common Brake fern has its thecse curiously
concealed round the edges of the fronds, the margins
of which turn down over them. Another little
native fern, the Scaly Spleenwort, has its whole
stalk as well as the backs of its fronds covered
with scales resembling bits of lace ; and the thecse
lie thickly between them, like ribbons in the border
of a cap.

The collector of native ferns will naturally feel
inclined to examine foreign ones also ; and this can
be easily done, as beautiful exotic ferns are in much
favour in the conservatory.

Fig. 9 represents part of the frond of a foreign
fern, tha,t known as the Harems-Foot, or Davallia.
Its groups of thecse are on the tips of the leaf-
lets; the covers are somewhat like little pockets,
and, when filled with thecaa, resemble baskets of
flowers.

It will occur to the reader, that there must be a
very great number of spores on the fronds of ferns.
This is the case ; and in the Hart's-Tongue fern, which
has remarkably small spores and thecae, the amount
is quite prodigious. Each frond bears on an average
80 sori (collections of thecse), containing from 3000

Vegetable Productions. 91

to 6000 — that is, on an average containing 4500 theca3
in one sorus, making 360,000 on the whole frond.
And these thecaB each contain about 50 spores. So
that a single frond of Hart's -Tongue fern carries no
less than eighteen millions of spores !

92 The Microscope.

CHAPTER IX.

ORGANIC REMAINS, CRYSTALS, AND ARTIFICIAL OBJECTS.

]HE microscope affords a great deal of informa-
tion to the geological inquirer, not only with
regard to the real nature of various animal
and vegetable remains which are found as fossils in
the different strata, but also with regard to the com-
position of the strata themselves.

Fossil trees have been found in various strata, more
or less perfect. Sometimes their fibres have been
completely penetrated by the mineral " silica," some-
times by carbonate of lime, and when this has occurred,
their minute cells and vessels are well preserved, and
it is quite possible to make thin sections of them
capable of being compared with those of recent wood.
There are certain markings of cells and fibres by
which the wood of a cone-bearing tree (larch, for
instance,) may be readily distinguished from such
trees as the oak and elm. Other characteristics mark
the palm tribe, and all these structures may be
observed in the fossil woods of the newer strata. In
the earlier strata, the cone-bearing trees and the
palms are, with rare exceptions, the only forms dis-
covered; and in coal, which the microscope has

Organic Remains, Crystals, and Artificial Objects. 93

proved to be nothing else than a mass of decomposed
vegetable matter, the arrangement of its minute in-
ternal structure shows that it must have belonged
exclusively to the cone-bearing tribe of trees. In
some coals, the structure can only be indistinctly dis-
cerned ; in others it is very plainly to be recognized ;
and it would appear that the Araucaria is the modern
plant to which coal makes the nearest approxi-
mation. The decomposed wood of which coal
consists appears to have "been reduced to a
pulpy state by decay, before the process of con-
solidation by pressure, aided perhaps by heat, com-
menced."*

And just as these productions of the vegetable
world can be referred to their true classes by the
microscope's help, so certain fossil spines, bones, and
teeth, found in so fragmentary a state that but little
of their form could be traced, have been identified by
an examination of their minute structure with that in-
strument. In a somewhat similar way, the microscope
has assisted in throwing light on the past history of
the earth's strata.

The little microscopic vegetables named diatoms,
or, at greater length, Diatomacece (to which allusion
has already been made), are found living both in fresh
and salt water, and their remaius, hardened by the
presence of silica, are also to be found in quantities at
the bottom of fresh-water lakes, or on the bed of the
ocean. When a geologist therefore meets with an

* Carpenter, p. 752

94 The Microscope.

extensive stratum of earth, which, when examined
with the microscope, turns out to be entirely com-
posed of fossilized diatoms, he feels no doubt that it
has once been the bottom of a lake or sea.

And there are minute animals which give similar
evidence with respect to the great chalk formation,
and to the limestone rock which forms so considerable
a portion of the earth's crust.

As I write, a slide is placed on the microscope
stage, containing a little mud apparently, obtained
some years ago by deep-sea soundings from the bed
of the Atlantic Ocean, one thousand eight hundred
and thirty fathoms deep, to wit, more than two miles. I
view it with a magnifying power of twenty diameters,
and see that it consists of a multitude of minute nau-
tilus-like shells, some broken, some perfect, and of
several shapeless fragments. These little shells are
not of the nautilus species, their inmates having been
discovered to be widely different from those of the
nautilus shell. They are of the very numerous class
designated Foraminifera, and Dr. Carpenter states
that they are found living on the upper surface of the
" ooze " forming the bed of the Atlantic, while its
lower layers are almost entirely composed of dead
shells of the same type.

A section of limestone will be found to present an
appearance somewhat similar to that of the ooze of
the Atlantic ; for all limestone is composed of a mass
of extremely minute animal remains, among which the
Foraminifera abound, as also in chalk. It is not very
difficult to make a section of limestone. A small thin

Organic Remains, Crystals, and Artificial Objects. 95

fragment is to be selected, and ground down on a
hone till its surfaces are tolerably flat. When too
thin to be held longer in the fingers, one of its
sides should be fastened with Canada balsam to a glass
slide, and the grinding process gone on with till the
limestone becomes so thin as to be a pale grey and
partly transparent.

Plate "VII., fig. 10, represents a portion of a sec-
tion of nearly black limestone, which I saw prepared
in this way ; and its resemblance to the slide of Atlan-
tic mud is interesting.

From the consideration of coal, chalk, and lime-
stone, which, although they are in the mineral
domains, bear evidence of organic composition, we
may turn to the substances which are truly inorganic.
When these present any appearance of symmetry in
their forms, it is because their particles have arranged
themselves in that peculiar manner known as crystalli-
zation. Each substance which crystallizes at all, does
so after a certain type or plan. Not that all crystals
of the same substance will surely look alike; but it
will be found that the same plan of crystallization will
exhibit itself under a great variety of forms. Various
natural specimens are interesting, when shown in thin
sections; granits and agate may be mentioned as
examples ; and crystals can be obtained artificially by
making strong solutions of various salts, placing a drop
of ^ach on a glass slide, and allowing it to evaporate
slowly. Such crystals are in many cases splendid
objects for the polarizing apparatus.

The actual process of crystallization may be ob-

96 The Microscope.

served with tlie microscope, and that in a variety of
interesting ways. For instance, the formation of the
metallic crystals of silver may be thus viewed, and
few objects give greater pleasure. A solution of
nitrate of silver is laid on the slide, a few copper
filings are dropped upon it, and instantly each grain
of copper becomes the centre of a brilliant tree-like
crystal of silver, growing rapidly as one views it, till
it reaches and perhaps shoots across another branch,
and the whole field is soon covered with glittering
foliage. And this is interesting as a chemical experi-
ment, showing the effect of " affinity." The copper
robs the silver of its nitric acid, obliging the silver to
appear in the metallic state.

Or we may simply watch the effect of crystalliza-
tion in a salt without further admixture. Let us place
a drop of muriate of ammonia, rather thinly spread out
upon the slide. In a few moments some needle-like
crystals, straight and keen, dart across the field, and
then minor needles dart from them at right angles.
Now some half-dozen large darts spring forward — we
think of a charge of bayonets, when suddenly every
weapon turns into a spruce-fir tree, with branches of
unusual straightness.

This object is not altered by polarization ; but salt-
petre polarizes well. A drop of the solution remains
inert for 'a while, scarcely visible on the black ground
which we have obtained by a particular arrangement
of the prisms. Suddenly at the edges of the drop we
notice a few bright little crystals, like small books seen
in perspective, floating just within the boundary.

Organic Remains, Crystals, and Artificial Objects. 97

While we look, they have grown imperceptibly, and
new ones have joined them ; presently all the edges of
the drop are crowded with these brilliant little books,
pink, green, blue, orange, and other fine colours.
Suddenly there come down upon them certain long
keen sabre-like crystals, which we may liken to paper-
cutters : this occurs when the film is nearly dry.

Dr. Carpenter's and other works give the names
of a great number of crystals suitable for microscopic
observation. Eeferring the reader to these, I shall
now only describe the arrangement which I have
found satisfactory for displaying them. A reader
happy enough to have a considerable knowledge of
chemistry will easily find out how to vary the experi-
ments.

Such a reader will very probably have various
little appliances at hand preferable to those which I
describe; mine may, however, be commended as
answering their purpose, and enabling the exhibitor
to avoid disfiguring stains from the nitrate of silver.
To proceed, then ; the various solutions, of which a
small teaspoonful will be quite sufficient to prepare,
may be made in one of those colour-trays generally
accompanying paint-boxes, and containing half-a-
dozen hollows. It is well to write neat little labels,
and gum one near each hollow, say "nitr. silver/'
" sulph. copper/' ' ' sugar of lead/' ' ' saltpetre," ' ' mu-
riate amm." You should have at hand a bottle of
rain-water, a few slips of glass of the usual size, and
some narrow pieces of glass, or glass rods ; also two
or three rags, one as a complete drudge to wipe off

7

98 The Microscope.

nitrate of silver when required, regardless of the black
stains which will presently appear upon it. The salts
will dissolve quickly in their compartments, and as
they will (except coloured ones, as the sulphate of
copper,) appear like clear water, you will find the con-
venience of having each labelled.

The microscope should now be properly arranged,
because in many cases the process of crystallization is
very rapid, and the best effects would be lost during a
few minutes of delay. The tube should be inclined
slightly, and the power employed should be about sixty
diameters, which serves for most crystals. A slide
should be laid on the stage, with a scrap of paper or
some small object placed upon its surface. The focus
must be adjusted on this, and if the crystallization is
to be viewed as an opaque object, a good light must
be thrown upon it from the bull's-eye lens. All being
ready, the scrap of paper may be removed, and a drop
of the solution lifted by one of the glass rods or
narrow slips, and placed on the slide. For exhibiting
metallic crystals dark slides will be found very con-
venient.*

The copper or zinc filings for dropping into the
solution must be in readiness. It is worth while to
make deep little envelopes to contain them, like those
in which small garden-seeds are sold. A little of the
filings can be shaken on to the flap of the envelope,

* Mr. Dancer, of Manchester, has kindly presented some of these
dark slips of glass to me, and has furnished me with information on
the subject of crystallization, as well as of microscopic photo-
graphy.

Organic Remains, Crystals} and Artificial Objects. 99

while the rest is kept back ; the few loose grains are
dropped on to the solution, and the lovely crystalliza-
tion at once commences; but it requires a little
practice to show it with certainty, and at the best
moment.

If a simple salt has to be shown by transmitted
light, the microscope's mirror must be arranged ac-
cordingly, and then, the solution being placed on the
slide, must be watched, especially at its upper part,
which will appear in the microscope to be the lower ;
the film being thinnest there, the crystallization will
probably commence in that part. Some salts require
the slide to be more or less warmed, and a wax night-
light always occurs to my mind as the very tidiest and
simplest way of doing this. A few trials will show
whether warming is advisable or not. The process of
crystallization can be shown over and over again by
wiping away the solution each time, and cleaning the
slides ; and considering the powerful destructive ten-
dencies of some salts, it might be well to end the
performance by wiping the colour-tray itself, lest its
Gontents might get on clothes and do mischief. It
may chance that some of the crystals will have been
more than usually beautiful, and the experimentor may
wish to preserve them; this can generally be effected
by dropping Canada balsam over them, or a little oil,
after which they can be covered with thin glass, and
mounted in the ordinary way.

We are presently to imagine ourselves enjoying a
summer entertainment, observing living creatures in
the animalcule cage, in the " ample field " of a watch-

100 The Microscope.

glass, or otherwise arranged as may seeni best. But
before taking leave of " prepared slides/' a few words
must be added on a class of microscopic objects which
the reader has most probably met, and viewed with
surprise and curiosity. I mean the Microscopic Pho-
tographs. They may be classed as wonders of the
photographic camera, rather than of the microscope ;
but as they cannot be seen without the help of the
latter instrument, a notice of them may be considered
not out of place in the present work.

A few specimens of these may generally be formed
in collections. To the unassisted eye they look much
like other objects mounted in balsam; all that is
visible on the slide is a neat little disc of thin glass,
with a tiny grey dot in its centre, smaller than a pin's
head. But the slide bears a label, oddly contrasting
with the scientific matters suggested to us by the
slides which we have hitherto considered, and showing
that the object ia a miniature of some well-known
engraving, portrait, or inscription. "We place it on
the stage, and see it magnified to the dimensions of
an ordinary book illustration, and appearing like a
tolerably good lithograph. An observer unaccustomed
to the microscope can scarcely believe that a number
of well-executed faces and figures, or several lines of
clearly legible printing, can be contained in a space so
extremely small ; and the ocular proof that it really is
so, affords much interest and surprise, and at the
same time conveys a tangible idea of the micro-
scope's power. These little photographs have ac-
quired considerable popularity; and I do not wish

Organic Remains, Crystals, and Artificial Objects. 101

the reader who looks in this book for some account
of their history, the method of their production, and
the use (if any) which has been made of them, to look
in vain.

The idea of employing the photographic principle
in producing specimens of printing so small as to
be legible only with the microscope, occurred to Mr.
Dancer, of Manchester, so long ago as the year 1839.
This was several years before the discovery of the
collodion process, and accordingly these were daguerre-
otypes. Mr. Dancer reduced a bill twenty inches in
length to one-eighth of an inch ; but as the nature of
the deposit on silver plates prevented the lines being
fine enough to admit of being viewed with any but
the lower powers of the microscope, he laid the
matter aside, till the year 1852, when Mr. Archer's
discovery of the collodion process enabled him to
produce far minuter specimens. He paid considerable
attention to the subject, and has since that time exe-
cuted some specimens which are indeed marvels of
photography.

At a meeting of the Manchester Photographic
Society, on April 6th, 1859, a microscopic photograph
by Mr. Dancer was exhibited, consisting of two pages
of " Quekett's Treatise on the Microscope/' reduced
to one sixteen-hundredth part of a superficial inch
(that is to say, if the two pages made a square, such
square was one-fortieth of an inch in diameter.) They
included three thousand six hundred and thirty-
one letters, and at the same rate the whole volume of
five hundred and sixty pages could be contained

102 The Microscope.

in a space of three-eighths of an inch square*
(No. 9).

These photographs are taken with a photographic
camera, in which, instead of the large lens which has
stared at most of us in these days of cartes-de-visite,
one of the object-glasses of a microscope is used.
The pictures are taken on very carefully-
prepared iodized collodion, and developed
by pyrogallic acid or sulphate of iron.

No. 9. When dry, they are mounted in Canada
balsam to protect them.

Microscopic photographs were also the independent
invention of Mr. Shadbolt, in the year 1854. He
exhibited a number of them in that year, ranging
from the one-twentieth to the one-fortieth of an inch
each way, one of which was a pretty extensive view of
Paris.

There is another class of objects which may be
described along with the microscopic photographs,
although the method of their production is quite dif-
ferent. These are some exquisitely minute specimens
of ruled lines and of writing done upon the glass with
a diamond point.

Many microscopes are furnished with what is
called an eye-piece micrometer, used, as the name
imports, for measuring minute spaces. It consists of
a series of delicate lines, ruled by ingenious machinery
on glass at regular intervals, and crossed with others.
So many as ten thousand lines have been ruled in this
way in the diameter of an inch. The test-objects

* " Photographic Journal," for April 15th, 1859.

Organic Bemains, Crystals, and Artificial Objects. 103

known as "M. Nobert's" afford another example of

this process of machine-ruling. ' ' As at present sup-

plied, they consist of a slip of glass

(No. 1 0),on which, by careful observation

with the naked eye, may be observed

what looks like a single shadowy line,

sparkling in bright light with the play of

prismatic colours. By moderate power

(fifty diameters), with good glass and

careful illumination, twenty distinct

bands may be counted (that is, in the

breadth and not the length of the line) ;

the finer, however, very shadowy and

evanescent. With 100 diameters, the

four coarsest should be shown in distinct

lines ; as the power is increased, more and more of the

bands will be resolved, till with 500 diameters, the

separate lines composing all but one or two of the finest

of the bands should be clearly seen"* (No. 11).

No.lO.— Nobert's
Test-Lines.

No. 11.

It is calculated that the coarsest lines are about
the thirteen-thousandth of an inch from each other,
and the finest the eighty thousandth.

Of microscopic writing, some remarkable speci-
mens were shown at the International Exhibition of

* From an article on "Nobert's Test-Lines," by Mr. Tuffea
West, F.L.S., in " Recreative Science," vol. i.

104 The Microscope.

1862. One of these was a piece of writing, con-
taining four thousand one hundred and thirty- seven
letters in the one thousand and fifty-fourth of an inch.
The letters were filled with black-lead of extreme
fineness. I was shown this specimen when at the
Exhibition; the writing was a clear text hand, and
quite legible through a high magnifying power. It
was executed by Mr. W. Webb. The instrument
used was also exhibited, and may be described as
a long rod or lever, carrying at its lower end a
pencil, which is traced over the original writing
that is to be reproduced in miniature. The short
arm of this lever is concealed in a box above, and
acts upon a second lever, the arrangement being
repeated until the motion which originates with the
hand below is reproduced in the required degree of
minuteness. The extremity of the lever moving
through this small space carries a diamond point,
which is pressed against a plate of glass, producing
by its action a piece of microscopic writing, corres-
ponding with the full-sized design over which the
long arm of the lever is traced below. This sort
of instrument is called a pantograph, or pentagraph.
Still more wonderful were the specimens produced
by Mr. Peters's pantograph, and exhibited by the
Microscopic Society.

I am informed that M. Froment, of Paris, pro-
duced specimens of this kind of writing so long ago
as 1851, and that some executed by him exhibit
all the symmetry of copper-plate engraving.

The Animalcules in Water. 105

CHAPTER X.

THE ANIMACULES AND OTHER MINUTE INHABITANTS OP
WATER.

jHE animacules in water — what, in the water
we drink ? Such, perhaps, is your question,
reader, on observing the title of this chapter ;
and I hope you will simply feel pleasure, and not a
shade of regret at the loss of a long-believed horror,
when you hear that animalcules do NOT inhabit spring-
water, and you might look in vain for them in many a
clear pool or flowing stream. It would be difficult
perhaps to say whence we have each derived the tradi-
tion that all water is full of animalcules ; but my im-
pression is, that some worthy Oriental in a story-book
impressed my young mind with the belief. He was a
Brahmin, and boasted to a European sage that he
never ate anything which had life. The sage forth-
with demanded a glass of water, and exhibited the
supposed swarming animalcules with a microscope,
whereupon the Brahmin dashed the too-instructive
instrument on the ground. With my present ex-
perience I should feel but little alarmed for the
fate of my microscope, if its destruction were to

106 The Microscope.

follow on the discovery of animalcules in a drop
of pure-looking water; but the case was different
when I first used the microscope, till by slow de-
grees I discovered that these minute creatures in-
habit stagnant water, occurring in countless numbers
around decaying plants, and also in ponds where
submerged weeds are growing, and, like the large and
visible animals, must be sought out and found, some
in one place and some in another.

It has so happened that I have never systemati-
cally studied their ways, or endeavoured to draw their
likenesses.* My fishing in the ponds and streams
was undertaken with a view to obtaining the beetles,
boat-flies, shells, and other comparatively large deni-
zens of the water, and also suitable objects for exhibit-
ing the wonderful spectacle of the circulation of the
blood in the unhurt and living animal. But as the same
water which produced the water-beetle, the stickleback,
and the newt, was likely to furnish also the wheel ani-
malcule, the Bell-flower, and a host of smaller restless
creatures, I became familiar with their appearance,
and hoped at some time to study them, and profit by
the discoveries which of late years have been made
concerning them by various eminent observers. To
a certain extent I have realized this wish ; but am ren-
dered independent of the task of drawing them by the

* The fignres here given of animalcules, with the exception of No.
13, and a few others, are taken by the permission of the publishers
from Mr. Slack's " Marvels of Pond-Life." But in each case I have
examined the object depicted, and can vouch for the accuracy of its
representation.

TJie Animalcules in Water. 107

many accurate and beautiful illustrations which can
now be obtained of all the remarkable kinds which I
have seen, and of many which I have not hitherto ob-
served. Mr. Slack's work, " Marvels of Pond-Life,"
figures the animalcules with much spirit and accuracy,
aided by descriptions alike faithful and graphic. But,
more than this — though the book is small, and the
style anecdotal, the subject is fully treated in its various
bearings, with all the lights obtainable from contem-
poraneous research. A microscopic student, anxious
for pleasantly-given information about the animalcules,
can hardly do without Mr. Slack's book.

And this being the case, I shall give but a short
account of them here, merely indicating their principal
classes, and the methods of obtaining them, which I
have found successful. To tell the story of my pond ex-
perience in the spring and summer of the present year,
will be as good a way as any for introducing the subject.

I was particularly anxious last March to obtain
some young tadpoles, during the few weeks in which
specimens could be had, showing the circulation in
the "branchiae," or external gills, an object which
I had carefully watched and figured several years ago.
I had observed a promising supply of frog-spawn in a
kind of pond, at a few hundred yards' distance from
one of the large peat-bogs so characteristic of this
country ; and I sallied forth to secure a small quantity
of it, and at the same time to fetch some water likely
to contain animalcules.* My implements were a

* The locality was in the King's County, a few miles from the
village of Clara,

108

The Microscope.

group of apparatus somewhat similar to those repre-
sented in woodcut No. 3 (page 22), only that instead of
a single small phial — I brought about four — for the pur-
pose of obtaining samples from other ponds and ditches ;
for some ditches nearer to the bog abounded in conferva

No. 12.— Arrangement of Microscope for viewing minute Water
Animals.

The Animalcules in Water.

109

into the water; some pieces of weed from each place
were dropped in, and a larger bottle was employed for
holding a little of the frog-spawn, which tor the informa-

Nat. Size:

No. 13. — Young Tadpole, Stems of Duckweed, and various Ani-
malcules magnified twenty diameters.

tion of those who have not seen any, is a jelly-like sub-
stance, looking not unlike a quantity of white currants
laid closely together, and containing a round black

110 The Microscope.

shot in the centre of each. At least such is its early
form; for the frog-spawn which I brought into the
house had begun to change its aspect, and instead
of little black shot-like balls, contained bean-shaped
morsels, which each day assumed more and more the
appearance of young tadpoles. I left a small portion
of this frog- spawn in a wine-glass, and I put the con-
tents of the bottles into sundry saucers and finger-
glasses, and proceeded to examine their contents, by
placing a drop from each (one at a time of course) in
the live-box, and transferring this to the microscope's
stage. In this way I observed a good variety of ani-
malcules, and pleasantly revived my recollections of
them. The young tadpoles throve very well in the
wine-glass, and in due time arrived at the stage in
which I wished to examine them.

It is possible to observe these in the live-box, or
in a watch-glass ; but my experience of either plan is
that tadpoles wriggle most unpleasantly, and never
more so than when one is making minute and difficult
observations upon them. So I called to mind how
pleasantly I examined them some years ago, through
the sides of a wine-glass, with the Coddington
lens ; and it occurred to me, ' ' why not attempt to use
the tube of the microscope in the same way ?" For
the young tadpole, when about the size of a grain of
oats, though very fidgety when under constraint, has
a habit when left to its own devices of resting motion-
less for several minutes at a time. It possesses a
fringe-like arrangement around its mouth, enabling it
to hold on to any filmy remnants of the frog- spawn or

TJie Animalcules in Water. Ill

other floating matter, and thus suspend itself in an
upright position. Several of the tadpoles in the wine-
glass were generally to be seen suspended in this
way ; and some of these were quite close to its inner
surface.

I removed the microscope tube from the stand,
and mounted it, as shown in No. 12, upon a cushion
raised on a large book, so that I could look as
through a telescope into the wine-glass. The drawing
represents the arrangement for lamp-light, but I pre-
ferred using this plan in the daytime. It answered
exceedingly well, much better than the Coddington
lens, and my observations about the tadpole will be
given in the concluding chapter. Those observations
at first engrossed my attention; but presently it
struck me, how picturesquely are the animalcules
shown, in perfect liberty, threading their way amidst
the transparent forest of duckweed stems, or growing
plant-like upon them, or on the inside of the glass
itself, and how great a variety of them appears in the
field of view ! I commenced to make a list of them ;
it may serve as a sort of inventory of the set likely to
be found in a duckweed-covered pond. Other kinds
—to be presently named — were in the additional
vessels, but all here were actually in the wine-glass
along with the tadpole (No. 13).

1. — The Stentors. Trumpet-shaped and bright
green. Sometimes like a post-horn, almost as slender
as a horse-chestnut leaf-stalk, sometimes shorter and
broader ; some are thimble-shaped, and moving freely
about. One of them pale brown, nearly colourless.

112 The Microscope.

2. — The Vorticellce (bell-flower animalcules) . Some-
times double-headed, sometimes swimming freely, with
no stalks.

3. — The short wheel-animalcule, creeping leech-like
by arching its body and drawing up its foot to its
head, then putting its head forward, and so on. It
carries a pair of wheels, apparently on its head, and
can swim freely through the water.

4. — The astonishing, transparent, bagpipe-like
creature, rolling over slowly.

5. — The swan-like little creatures.

6. — The bright green animalcules, covered with
hairs, very common.

7. — The colourless animalcules, bean-shaped, like
the green, and commonest of all.

8. — Smaller colourless animalcules, also very
common.

9. — Animated straw-mat, very bristly, and ap-
parently hot-tempered, always making sudden darts.
Ornamented with three or four little movable commas.
It was sometimes to be seen in side view, darting
along stalks.

10. — The stiff-branched pillar, almost like a plant,
though resembling Vorticellce ; standing on the duck-
weed stalk, and occasionally moving one of its bells
slightly.

11. — The animated blackberries— brown, however,
not black — solemnly rolling over and over.

12. — The chain-like filaments, their links fastened
generally at opposite corners.

] 3. — The little wedges OH branched stems.

The Animalcules in Water. 113

There were a few others besides these, which
appeared when a small portion of the duckweed and
a drop of the water were examined in a live-box ; but
the above were all seen with the microscope through
the wine-glass's side. I found it not difficult to
remove for closer examination, any particular group
of stentors, or tolerably large animalcules, by raising
them with a shovel-like wedge of paper. Another
well-known and excellent plan for securing small
objects in the water is to use a " dipping- tube." This
being made of glass, and open at each end, you place
your finger on its top, and gently push its lower end
close to the object ; then slightly raise your finger,
and a little water will suddenly rise into the tube,
probably carrying the object with it, which you
can then lift on to a slip of glass, or to the live-box.

A glass trough has been contrived for holding
animalcules and growing plants, and allowing these
to be examined from outside, it looks not unlike one
of the " baths " used in photography. Dr. Carpenter
figures it, and also gives a view of an "aquarium
microscope/' the instrument's tube being mounted on
a stem which can be attached like a vice to a table ;
still I have described my own plan, as it may be said
to require no apparatus.

And now for a little book-lore on the subject of
the tadpole's small neighbours. In the infancy of
microscopic knowledge, all the minute water-animak
which were too small to be discerned without a micro-
scope, and which could not be very clearly examined
even with the microscope, that instrument being then

S

114 The Microscope.

in an imperfect state, were classed together. The
name Animalcule was given to them, and applied to
a heterogeneous assemblage, including not only the
true animalcules, but a number of minute plants,
crustaceans, and larvae. One by one these have been
removed, and referred to other positions. It was an
easy matter to do this with regard to many of the
crustaceans and larvae, but the case is different with
a few of the plants, and also with some of the animals ;
naturalists are by no means agreed about the classifica-
tion of these, because thorough and complete observa-
tion of each species is necessary, to trace out its life-
history, before its place in the scale of creation can be
ascertained. There are numerous animalcules about
which this kind of observation has never been made ;
a wide field of research is therefore open to the micro-
scopic student.

The word animalcule, if we look at its derivation,
is nothing more than "wee animal," but it has a
distinct meaning ; for it includes just two well-marked
tribes of minute living creatures, to which the names
of Rotifera and Infusoria may be given, and excludes
certain perplexing little forms which are seen to move,
and yet generally set down as plants ; and also certain
small animals which are essentially different in struc-
ture from the rotifers and the infusoria, and are
designated the " root-footed," or Rhizopods.* These

* The classification adopted by Dr. Carpenter is here followed.
The two groups of animalcules, "having scarcely any feature in
common except their minute size," and one being of very low and
the other of comparatively high organization, were first recognized

The Animalcules in Water. 115

last-named creatures are of very simple organization,
and akin to the sponges, which, as Dr. Carpenter
says, have "been banded from the animal to the
vegetable kingdom, and back again several times in
succession."

None of these Rhizopods chance to occur among
the crowd represented at page 109. Some of the
plants, however, which once passed as animalcules,
maybe observed. The " animated blackberries" of
my list are specimens of " Protococcus," a plant, the
development of which was observed by Dr. Cohn, who
published its " memoir" at Bonn, in 1850. Its
powers of rolling over and over, and even of impelling
itself forward, are not singular among microscopic
plants. The several forms assumed by protococcus in
different stages of its growth, have led to its being
taken for a number of distinct genera of animalcules,
and described under several names.

The " chain-like filaments " in my list are two
specimens of Diatoma vulgare, represented on a larger
scale in the figure on p. 116.

It belongs to the numerous and widely-spread
tribe of the diatomacess, a long word, which simply
means "cut (or broken) through," and appears to

as distinctly separate in structure by Professor Ehrenberg. He
named these two groups Polygastrica and Rotifera. The former
name was based on a theory which is now pronounced to be erroneous
and Dr. Carpenter substitutes for it the name Infusoria, once applied
to all the animalcules, from the prevalence of many of them in
infusions of hay and other vegetable matter ; but to the higher group
he still gives Ehrenberg's name of Eotifera, as appropriate to the
" wheels " carried by many of its members.

116

The Microscope.

indicate the readiness with which their component
parts separate. They were set down as animals by
the eminent Professor Ehrenberg, but are now classed
as plants by a number of careful investigators.

The " little wedges on branched stems," No. 13
in my list, are also diatoms, by
name Gomphonema geminatum.

The diatoms might in strictness
be excluded from a chapter on ani-
malcules; still as some naturalists
continue to class and describe them
as animals, some notice of them may
be considered admissible ; especially
as many examples of the tribe, when
dried and mounted on slides are
well-known microscopic objects of
extraordinary beauty ; and the
reader may look at these with added
interest, after comparing them with
these humbler specimens found in
a living state.

A great variety of form occurs
in the different species of diatoms. In the Diatomavul-
qare, represented above, which gives its name to the
whole group, its component cells are oblong, and gene-
rally in a state of partial separation, being joined by a
gelatinous hinge at the corners. Sometimes, how-
ever, two or more cells may be seen side by side, as
in the third link from the right in the figure. Other
diatoms, besides this one, have the same curious
arrangement for joining at their corners ; two of these,

No. 14.— Diatoma
vulgare.

The Animalcules in Water. 117

called Isthmia and Biddtdphia, inhabit sea-water, and
are very beautiful. But in some diatoms the cells are
closely joined, and form a nearly straight filament. If
the sides of the cells (generally called the " frustules "
of diatoms) are not parallel to each other, a curved
filament is produced.

Sometimes diatoms have stalks to which they grow
singly, or in a branched arrangement, as seen in Gom-
phonema ; others have a mucous or gelatinous cover-
ing, in which a number of the frustules lie. Some are
quite free, appearing singly, and these are of various
shapes — oval, triangular, boat-shaped, and round;
these last seeming like disks, and to be found (when
in their living state) adhering to sea-weeds.

These free diatoms have a strange power of moving
about. Those of the genus Navicula are familiar
objects to the microscopic observer. Several of them
may sometimes be seen together in the field of view ;
they are shaped like the decks of tiny ships, reminding
the beholder of the plan of some great sea-fight, where
the vessels appear in various directions; and while we
look, we notice that they are gliding along, but with
no visible means of propulsion. This motion is well
described by Mr. Tuffen West, artist of the beautiful
illustrations to the late Professor W. Smith's ' ' Synopsis
of the British Diatomacese."

He says, " It is not the rapid meteor-like whirl
of the infusorial animalcules, but a gentle gliding in
one direction, the distance and the time occupied in
traversing it being clearly defined, and readily noted
by a good watch ; there is then a brief period of rest,

118

The Microscope.

and the return journey is duly proceeded with." He
adds, " The reasons for, and way in which these
motions are effected, are involved in some obscurity."*
Professor Smith has suggested that forces operating
within the frustule may combine to impel it ; but it
would seem that nothing upon the subject has been
proved.

The shape of a diatom cannot always be ascertained
by looking at it in one
direction, as it is often of
some thickness (compara-
tively speaking), and its
front view very different
from that of the side. It
is made up of two portions
or valves, externally con-
vex, and hollow within.
No. 15 represents the front and side view of one
of those which appear as disks, when their sides
only are observed. A dissimilarity of appearance cor-
responding to this may be observed on a close
inspection of the lowest groups of Gomphonema, in
No. 13; their frustules seen in front resemble a figure
of 8 rather than a wedge. The valves of the diatoms
are sculptured with lines, dots, and other markings,
arranged so as to form patterns of exquisite tracery.
Some of these are of such extreme minuteness as to be
among the most difficult tests for the higher powers
of the microscope ; of these Pleurosigma (formerly
called Navicula), hippocampus is a well-known
* " Diatoms " by Tuffen West, « Recreative Science," vol. i., p. CD.

No. 15. — Coscinodiscus in
outline — a, side view;
6, front view.

The Animalcules in Water. 119

example, though by no means the most " difficult" of
these test-objects.

The most remarkable feature of the diatoms may
be said to be this, that their valves are made of flint ;
the contents are soft, but the flinty part remains,
skeleton-like, even after the diatom has been im-
mersed in nitric acid, or exposed to the action of fire.

Mr. Tuffen West, in the article already referred to,
says that a good way of readily observing the mark-
ings on diatoms is to place them on talc, and expose
this to a gentle red-heat. Accordingly one day,
happening to observe some roots of duckweed fes-
tooned with a quantity of diatoma and gomphonema
filaments, and some specimens of navicula moving
about near them, I placed them on a little disc of talc
(found among the apparatus of an old microscope), and
bearing well in mind the vegetable nature of diatoms,
and their consequent absence of feeling, carefully laid
the talc on a red-hot poker. I removed it when the
latter had become cold, and at once mounted the talc,
by turning it downwards on a glass slide, and fasten-
ing it with paper in my usual way. The effect of the
fire was interesting ; the duckweed had turned into a
faint heap of ashes, but the numerous diatoms showed
in great clearness both of outline and markings.

Dr. Carpenter remarks that the flinty covering of
the diatoms may rather be described as consolidated
with silex (flint) than altogether composed of it. He
states that Professor Bailey contrived to dissolve the
silex with hydro-fluoric acid, and there remained a
delicate membrane, bearing all the markings of the

120 The Microscope.

siliceous envelope; and he considers that this is a
cellulose coat, which becomes interpenetrated by silex.
It will be remembered that the delicate cells can be
traced in fossil wood (page 92) , when their walls
have been similarly penetrated by silex or by carbo-
nate of lime ; and, just as they remain almost inde-
structible, so do the tiny diatoms, testifying of their
existence in past ages, as they occur fossilized in
countless myriads in different parts of the world.

An extensive stratum of earth, eighteen feet in
thickness, underlies the whole city of Richmond, in
Virginia. When specimens of this earth are examined
with the microscope, they prove to be almost entirely
composed of the shells, broken and perfect, of dia-
toms, in great variety, and exquisitely beautiful. A
similar stratum of so-called " infusorial earth" occurs
in Bermuda, and a group of the diatoms from the
latter are on the microscope's stage while I write.
They are all circular, and named Heliopelta — ({ shield
of the sun," and round as Norval's shield ! See a
specimen of Heliopelta, reader, if you can; and if
you will examine it with various magnifying powers
and modes of illumination, you will be at once asto-
nished and delighted at the perfection of its structure,
and the wonderful delicacy of its tracery; and will
feel pleased at being in some degree informed as to
its nature.*

* The reader will find all the most beautiful diatoms named and
briefly described in L. Lane Clarke's " Objects for the Microscope."

The Animalcules, continued. 121

CHAPTER XI.

THE ANIMALCULES, CONTINUED.

now to proceed with, or rather commence,
our identification of the animalcules in No.
13. The two orders spoken of by Dr. Car-
penter are both represented here, although the latter
class is in a minority, as it has but one example,
number 3, the " short wheel-animalculee." We shall
consider it last, along with some fine examples of the
same class which occurred among water-plants in my
other collections.

The beautiful vorticellae, or bell-flower animalcule,
shall claim attention first. You may see them (for the
bell-flowers congregate together like so many cam-
panulas in a flower-border) mounted on their delicate
hair-like stems, occasionally swaying to and fro.
There ! one has disappeared with a sudden movement ;
has it dissolved ? No ; it has only drawn back ; and
here again it comes slowly forward, its head globular,
instead of vase-shaped, and its stalk coiled into an
elegant corkscrew form, which gradually straightens
itself. Then the globular head, by some movement

122 The Microscope.

difficult to follow, again becomes a vase. Meanwhile,
another and another of the group draws back, dis-
appears, and again advances, till the observer is half
perplexed by the multitude of corkscrew stems and
moving bells. But this is not all ; for all the little
chance particles in the water are in lively whirlpool
movement around every stationary vase. We connect
this in our minds (and rightly) with the little tuft-like
structures visible at the edges of each ; these seem to
stir with a motion that can best be described by the
phrase " twiddling."

Such is the appearance of these structures at
first sight, and when special arrangements are not
made for illumination. But when this latter point
is duly attended to, we can observe that the bells
are surrounded by a complete wreath or border of
transparent moving filaments, called " cilia ;" and
we shall meet these curious organs again and again
while observing the animalcules. They serve for
attracting their food from the surrounding water;
and in many animalcules they act as a means for
propelling themselves where they will — if such an
expression can be used with reference to the infu-
soria, whose movements seem scarcely dictated by
a conscious will. And that these " ciliary movements"
are not indicative of consciousness seems possible,
since, as Dr. Carpenter observes, "we know that
ciliary action takes place to a large extent in our own
bodies without the least dependence upon our con-
sciousness, and that it is also observable in the struc-
tures developed by the spores of some plants/'

The Animalcules, continued. 123

Be that as it may, the movement of the cilia gives
an air of peculiar liveliness to a group of animalcules.
Some possess them around their mouths only, like the
vorticellse, but around those mouths the particles dance
like sparks from a revolving firework. A vorticella,
too, sometimes detaches itself from its stalk, as ob-
served at page 112, and it then uses its cilia for pro-
pulsion through the water. Others again, as the
stentors, and the lively infusoria numbered 6, are
nearly covered with them. Their shape and size can
only be made out when they chance to move slowly ;
it then appears that each filament bends from its root
to its point, returning again to its original state, and
that there is a sort of " feathering" action, like the
stroke of an oar. This being repeated all round a
wreath of cilia, conv*eys a strange likeness to a really
progressive movement. It is with an effort of the
better judgment, based on a recollection of their ap-
pearance when detected in slower motion, that the
observer manages to rest assured that the object looked
-at does not consist of a number of little filaments,
chasing each other round a circle, or, in the case of
the rotifers, of a little toothed wheel, revolving bodily
upon a fixed axle. But the same illusion will take
place occasionally with regard to other moving objects,
each of which we know experiences no progressive
change of place. The appearance of moving waves
caused by "the wind that shakes the barley" is a
familiar instance ; and one which impressed me
forcibly, was the apparently wheel-like movement of
some circular devices in gas, when the principal streets

124 The Microscope.

in London were illuminated some years ago, in honour
of a distinguished visitor. It was not till I had
clearly ascertained that each jet was fixed, but sub-
jected to a whirling motion from the air, that I realized
that the whole thing did not turn on a central pivot.

The expansion of a vorticella's cilia, after its sud-
den retreat and gradual emerging, can be detected by
a little practice and management of the microscope's
focus screw. It will swing its globular head into full
view, and suddenly its rim will open out, and the
fringe of cilia show for an instant in extreme delicacy ;
and then, off they go, in their rapid whirling move-
ment.

The portly stentors, however, show the cilia in
splendid style. The one which is represented thim-
ble-shaped, and careering along at the right of No.
13, is using its cilia as paddles to propel it, while
the three temporarily fixed, and generally of trumpet
shape, are attracting food to their mouths. This
animalcule (that is to say, the bright green species
of stentor, Stentor polymorphus, or the many-shaped,)
is quite visible to the unassisted eye. They will
often occur in great numbers (and the same may be
said of other animalcules) in a piece of water on
one fishing occasion, and be quite scarce, or appa-
rently altogether absent, at another time.

Number 4 is another animalcule. It is the
" bagpipe-like creature" of my list, and I believe
was Trachelius ovum.

The " stiff- branched pillars," so described in my
list in contradistinction to the slender waving stem of

TJie Animalcules, continued.

125

the vorticellce, are called Epistylis, and are allied to
the vorticellaa. They bear a considerable resemblance
to the branched vorticella, called carchesium — a really
splendid object. I have seen it occasionally, and
Mr. Slack describes it very truly when he says,
( ' A group of these
creatures presents
a spectacle of ex-
traordinary beauty
— it looks like a
tree from fairyland,
in which every leaf
has a sentient life."
Ten or more bells,
with long thin
stems, exactly like the ordi-
nary vorticellas, will be seen
mounted on a stalk; and, in
the specimens which I ex-
amined, the stalk, which was
four or five times the thickness
of the other stems, had to a con-
siderable degree the contractile °' ' '"" P18?13'
power. It would draw the whole set of bells back-
ward with a force and suddenness quite startling;
and then, ever so gently and gracefully, the elegant
spiral stalk would unbend, and all the bells extend
themselves. And this can be well shown in the mode
of background illumination, when the beautiful stems
and vases, at all times transparent, and but slightly
tinged with a greenish or straw colour, appear as if

126 The Microscope.

moulded in sparkling glass,, and every stem seems
twisted into a graceful spiral pattern. One almost
speculates as to the possibility of modelling the whole
thing on a large scale, with black velvet background,
as an ornament of rare elegance ; but where would be
the added charm of its living grace and varied move-
ments ?

The account Dr. Carpenter gives of the branched
vorticellas is, that these infusoria, as well as many
others, multiply, plant-like by division. One sees an
usually wide head, and the same, after some hours,
may be observed to be actually double (see p. 112).
Then, in many cases, it breaks itself off, and reaches
the stage of existence, where it swims freely, and after
a while it fixes itself, and developes a new stalk.
Sometimes, however, instead of at once breaking off
when the double-headed stage is attained, the dividing
' ' extends down the stalk, which thus becomes double
for a greater or less part of its length ; and thus a
whole bunch of vorticellae may spring (by a repetition
of the same process) from one base. In some mem-
bers of the same family, indeed, an arborescent struc-
ture is produced, just as in certain diatoms, by the
like processes of division and gemmation." Here Dr.
Carpenter refers to a figure, which is no other than
that of the diatom " Gomphonema geminaimn;3' and,
on finding this, the reader may ask, "Why is that
diatom called a vegetable, and epistylis and vorticella
animals ? " There are certain considerations regard-
ing the different manner in which plants and animals
extract nourishment — the former directly from the

The Animalcules, continued. 127

elements that surround them, the latter from sub-
stances already organized — which afford a method of
drawing a distinction; but, as Mr. Slack tells us,
" the learned do by no means agree " on the question
" What is an animal ? and how does it differ from a
vegetable ? " and he amusingly characterises the dif-
ference as being " observable enough if we compare a
hippopotamus with a cabbage, but which grows
' small by degrees and beautifully less/ as we con-
template lower forms."

Something of the interest of a riddle, then,
attaches to these researches; but, more than this,
there is an especial charm in the contemplation of
these simply-framed plants and animals, which seems
to conduct us near to the elementary law or principle
on which all organized beings are formed.*

Passing over numbers 6, 7, and 8 of my list,
which I did not re-examine, but
which I believe to have been, the
first a Paramecium, characteris-
tically covered with long rows of
cilia, which I described as "hairs,"
and the last two members of the
Kolpod family, there remain the
rotifer, the swan-like animalcules,
and "animated straw-mat." This
last was Stylonichia, and I find NO. 17.— Stylonicliia.
that Mr. Slack makes mention
of its bristles and its comma-like appendages, both
of which are developments of cilia, and known as

* See " Marvels of Pond-Life,'* Introduction, and chap. xiii.

128 TJie Microscope.

styles and undni, or little hooks. They are also
described at considerable length by Mr. Gosse, in his
most interesting book, " Evenings at the Microscope."
The swan-like creatures appear somewhat similar to,
but not identical with, an animalcule represented in
Mr. Gosse's book and elsewhere as " Trachelocerca
olor."

And now we turn to the rotifer ; and in so doing
we get at once (it would seem) into very high com-
pany. They are as far removed in complexity of
structure from the other animalcules which we have
been considering, as the mosses are from the very
simplest plants; yet they have ever been described
along with their humbler neighbours. Had they a
voice to complain of this treatment, we could but
make an answer similar to that which Esop's husband-
man made to the expostulating stork, " Show me your
company, and I'll tell you what you are;" an ani-
malcule, though possessing various exalted character-
istics. For, in the wheel-animals, we witness what
the learned call a " differentiation " of parts and tissues,
and a " specialization" of organs. The head is plainly
distinguishable from the body, the skin or integument
is distinctly different from the internal tissues, "we
can detect a nervous ganglion or miniature brain, the
gizzard in a complicated piece of vital mechanism,
such as we have not met with before, and in various
parts of the transparent inside we see organs to which
particular functions are assigned."*

The rotifers form a numerous tribe, and many

* " Marvels of Pond-Life," p. 35.

The Animalcules, continued.

129

of the species are exceedingly abundant, occurring
in water where vegetable substances have decayed,
but rather to be expected when the active stage
of decay is over. Like the infusoria, they will
appear after a while in water where hay or leaves
have been infused — a fact which Dr. Carpenter
connects with the circumstance that
these animalcules can be completely
dried, and will yet return to activity on
being moistened ; for he says they may
be wafted in a dry state in the atmos-
phere, and thus removed from place to
place.

No. 18 represents the common wheel
animalcule (Rotifer vulgaris) which I
found repeatedly near the duckweed, as
well as among other water-plants. The
wheel-like organs show particularly well
in this specimen of the tribe. Their
appearance has been so often and so No 13
well described, that I need only vulgaris. A,giz-
remark that they do indeed look Sue v^siolt
exactly like a pair of pretty little
toothed wheels, revolving at a rapid rate. All this
is caused by the independent movement of the
separate cilia, as already explained, but the illusion
is so perfect, that we are not surprised to find that
the old microscopists thought these were really wheels;
thus the writer of the article " Animalcule," in the
Encyclopedia Britannica, edition of 1790, regularly
describes them as such, but informs us, whafc wo

9

130 The Microscope.

might not unnaturally expect, that the difficulty of
understanding how the rotation could be contrived,
' ' hath caused many people to imagine that there was
a deception in the case;" and it is interesting to
observe how those incredulous people in due time
have arrived at the truth.

The singular organ, A, is variously known as the
gizzard, masticating apparatus, jaws, and mouth.
It is to be observed, especially when the rotifer
fixes itself by its tail-foot and puts its " wheels"
into motion, working away actively as if grinding
the food; and, no doubt, it is thus employed. It
works with a peculiar force and smoothness, re-
minding the beholder of the movement of well-oiled
machinery. This organ is characteristic of the
rotifers; all possess this, though the wheels are by
no means universal among them.

Dr. Carpenter divides the Rotifera into four
groups, which I shall name, having been fortunate
enough to meet with specimens of each. He follows
the division propounded by M. Dujardin, which is
based on the several modes of life of the different
rotifers. For some always continue attached by the
foot to a leaf or other permanent resting-place ;
others can thus attach themselves, but are also able
to move, leech-like, or by rowing themselves by
means of their cilia through the water ; a third group
habitually swim, and rarely attach themselves ; while
a fourth creep slowly, and indeed seem to resemble
Rotifer vulgaris in little except the possession of some-
what similar jaws.

The Animalcules j continued. 131

Of the first of these groups, tlie Beautiful Floscule
(Floscularia ornata) and Melicerta ringens are most
interesting examples. I found both of them in April,
single specimens of each, and examined them with
sufficient care to enable me to appreciate the book-
descriptions of them, which had already excited my
curiosity.

The floscule was among a debris of water-weeds,
and appeared like a brown bulb on a stalk when
viewed with a low magnifying power ; but the moment
it greeted my eye, I thought ' ' here is a floscule, and
I shall see it thrust out its long hairs like an old-
fashioned drawing-room hearth-brush V The next
instant, it was plain that this had occurred; I well
remember the feeling of interest with which I sub-
stituted a power of 200 diameters for the lower
magnifier at first used. The floscules possess a
gelatinous tube, quite like a confectioner's glass jar ;
this I did not contrive to see, but I realized the rest
of Mr. Slack's description.

<e She slowly protruded a dense bunch of the fine
long hairs, which quivered in the light, and shone
with a delicate bluish green lustre, here and there
varied by opaline tints. The hairs were thrust out in.
a mass, somewhat after the mode in which the old-
fashioned telescope hearth-brooms were made to put
forth their bristles. As soon as they were completely
everted, together with the upper portion of the
floscule, six lobes gradually separated, causing the
haiis to fall on all sides in a graceful shower, and
when the process was complete, they remained per-

132

The Microscope.

No. 19.— The Beautiful Floscule. A, partially, B, fully expanded.
C, D, young Floscules. D', jaws of Floscule, as figured by Mr. Gosse.

The Animalcules, continued.

133

fectly motionless, in six hollow fan-shaped tufts, one
being attached to a lobe." A slight knock given to

No. 20.— Meiicerta ringens.

any part of the microscope always caused the flosculo

134 The Microscope.

to draw itself in ; but it would immediately recom
mence the beautiful process of expansion.

I lost sight of this floscule from the partial drying
up of the drop of water which contained it. The
specimen of Melicerta ringens occurred, precisely as
was to be expected, on a stalk of duckweed. This
is the wonderful animalcule which actually builds a
house for itself of globular pellets laid neatly together.
Mr. Gosse watched an animal of this species while in
the act of building its tube, and has • described what
he witnessed, in the " Transactions of the Micro-
scopical Society," vol. iii., 1863. It makes the separate
bricks of its edifice from the solid particles in the sur-
rounding water, collected by means of its wheel-appa-
ratus, and probably cemented by a glutinous substance
of its own producing.

The melicerta, like the floscule, often indulges its
shyness by retiring deep into its tube, and into its
self ; but if the dark tube is watched for a while, we
become aware of some sort of commotion at its mouth ;
then some feelers look out, and next a thick shapeless
lump, as if of flesh, appears, and then quickly enough
the four leaf-like expansions are turned out with a
deal of force, their cilia revolving at a great rate. A
knock on the table or microscope makes it retire, just
as is the case with the floscule. The melicerta tubes
are visible to the naked eye, and, being opaque and
dark, are very easily kept in sight. I placed mine
in a small quantity of water, guarding this as best I
might from evaporation, when called for a few days
from home, but on my return the tube proved to have

The Animalcules, continued.

135

lost its tenant. I tried the experiment of mounting
it in balsam, which answered perfectly. The object
is now before me, under a high magnifying power.
It stands like a tower, its front battlements showing
well, and those farthest from the eye appearing in
distant perspective. The round bricks, by mutual
pressure have assumed the hexagonal form, giving an
ornamental appearance to the little edifice.

The second tribe of rotifers, namely, those which

No. 21.— Philodina.

frequently attach themselves by the foot, but which
are able to swim, has been represented by the com-
mon wheel-animalcule. The rotifer represented in
No. 21, pliilodina, is another example. Its method
of walking is similar to that practised by the
common rotifer; and, like it, this rotifer can
draw itself into a globular and rather uninterest-
ing form when at rest, and disinclined for wheel-
exercise.

The third tribe are pretty little animals, often
possessing a cuirass or carapace of hard material,

136

The Microscope.

somewhat resembling the shell of a crab. No. 22
represents salpina, one of the species. I have occa-
sionally found the empty shells of some
of these rotifers, and contrived to mount
one of them in Canada balsam.

The fourth tribe which M. Dujardin
has included among the rotifers consists
of the Tardigrada, or slowsteppers,
popularly called "water-bears." They
are very fully described in " Marvels of
Pond-Life •" but a sight of the original
is required to give a full idea of the
creature's comical aspect. I first ob-
served it when examining a quantity
of weed in a live-box. The head
and a, pair of feet were suddenly poked into view,
and I thought, " here is a small larva/3 and

No. 22.—
Salpina.

No. 23.— Water-Bear.

expected a long body in several joints to follow,
when all at once the creature showed in its complete-
ness, walking along a stalk, and more like a young

TJie Animalcules, continued. 137

puppy with eight legs than can easily be believed !
Mr. Slack says his specimens had no visible eyes, and
that these organs are, according to Pritchard's book,*
ff variable and fugacious." My water-bears had eyes,
and of very respectable size and blackness. The first
specimen which I met, being given sufficient room
to climb by slightly raising the live-box' s cover,
seemed for some minutes as if staring at me, and in
that position not a little resembling the white polar
bear, its colour being somewhat pale. I felt inclined,
when looking at this animal, to side strongly with
those naturalists who (as Dr. Carpenter mentioned)
regard the Tardigrada as altogether distinct from the
true rotifers. Mr. Slack's account of them is, that
they are, physiologically speaking, poor relations of the
great family of spiders.

* Pritchard's " History of Infusoria"

138 The Microscope.

CHAPTER XII.

CIECULATION OP THE BLOOD.

|HE little tadpole suspended in the water at
No. 13 now claims our attention. He is an
individual of far higher standing than the
animalcules, being a vertebrated animal, and is the
tadpole of Rana temporaries, the common frog — which
I mention because young toads and newts are also
called tadpoles when in their aquatic state.

The microscopic spectacle which it presented to
especial advantage on April 10th, and for some days
later, was the circulation of the blood in the branchise
or external gills, those four hand-like appendages
which may be seen, two on each side of its head.

Plate VIII., fig. 5, represents a few of the capilla-
ries in the web of a frog's foot, under a very high
magnifying power. Each of these is filled by a
transparent fluid, in which are to b© seen the " isolated
floating cells " known as the "blood-corpuscles."
These are of two kinds, the " red " and the " colour-
less." The red always present the form of flattened
discs, which are circular in man and in most of the
beasts, and oval in the birds, reptiles, and fishes. They
are hollow, and contain a coloured fluid. The colour-

Circulation of tlie Blood. 139

less corpuscles occur only exceptionally among the
host of red ones. Dr. Carpenter states that for a
time they appear identical with the corpuscles found
floating in " chyle " and " lymph/' but are liable to
change their form ; and that their size is to a remark-
able degree similar in all the vertebrated animals,
whereas there are great differences in the dimensions
of the red corpuscles in the various species. One of
the colourless corpuscles may be seen in fig. 5 at the
right, and near the top. The " red " corpuscles of
the frog are exceedingly thin and flat, except at the
centre, where there is an oval or almond-shaped
thickening, which can be observed in a few of those
in fig. 5. These corpuscles are very pliable, and are
to be seen rolling over and over, and bending them-
selves at angles ; and occasionally a single one will
be observed caught for a few moments by some pro-
jection, till other corpuscles in passing sweep it into
the current ; and this description will also apply to the
movement of the corpuscles in some other animals as
observed with the microscope.

Circulation may be observed in various creatures
not belonging to the vertebrated classes ; to which,
however, the red corpuscles are peculiar.

Two objects were always kept in mind — namely, to
get a sight of the circulation in as many different
stages as possible ; and to do it without tyranny or
violence. Never yet have I injured fish, frog, or newt
on the microscope's stage ; their joyous return to com-
parative liberty has gladdened me also, and many a
walk I have taken up hill and down dale for the ex-

140 The Microscope.

press purpose of releasing them at the identical place
where they were captured.

I took notes at the time of a few facts which I
observed, and I made some rather elaborate drawings,
from a small number of which Plate VIII. is taken. I
also noted down, and will now relate, the manner
which I found convenient for securing the different
creatures, and which I still prefer to any other
methods.

The animals which are most easily obtained are
small fish, as sticklebacks, frogs, and (during spring
and a part of summer) tadpoles.

The stickleback being, according to Mrs. Glass's
immortal maxim, " first caught," can be secured in
this way : — A glass slide should be got ready, also a
little lump of jeweller's cotton, and a piece of soft
thread, about a quarter of a yard long. Then the fish
can be taken out of the water, and laid on the glass,
its head near one end, so that its tail might come near
the centre of the slide (No. 24, a). The cotton is to
be made quite wet, and laid over the fish, leaving only
its tail visible, and the thread, also made wet, is to be
wound round, b ; no fastening will be necessary. The
fish can move its tail a little, but will probably seldom
do so, and the tail-fin can be spread out, if required,
by a camel's-hair-brush. The use of the lump of
cotton is to prevent the threads from pressing the
fish anywhere too sharply, and also to retain as much
moisture as possible around the gills. Thus arranged,
the fish may be kept several minutes on the slide, a
few drops of water being occasionally spilt over it.

Circulation of the Blood.

141

When making the drawing from which Plate VIII.,
fig. 2, is taken, I often put the fish back into the
water, choosing for the purpose the interval when I
required to go over my sketch with pen-and-ink.
After a while, I placed the fish again on the slide,
sketched more, and ascertained points that had been
doubtful in the inking. There was no difficulty about

/

A It

No. 24 — Arrangements for exhibiting the circulation.

finding the portion wanted on its tail-fin. The
"achromatic condenser/' which I always use when
viewing the circulation, makes a disc of light exactly
where the object is placed ; so that with the unas-
sisted eye I could judge when I had placed the right
part of the fin over the light, and some familiar por-

142 The Microscope.

tion of it was sure to be in the field of view when the
microscope's tube was lowered.*

A tadpole cannot be arranged in exactly the same
manner as a stickleback ; for if it be tied down by
merely placing it on the glass, with cotton over it, the
circulation stops, because this creature does not
naturally lie on its side, its body being flat horizon-
tally rather than vertically (see c, d, No. 24). But if
cotton be placed both over and under it, it will be
secured, and the circulation will remain free. The
cotton should be left thin at e, that the tail may not
be too high above the level of the slide. The tadpole
should be laid somewhere about /, then turned over,
and it will generally come right with its tail laid
properly on the slide. The cotton can then be secured
as in the case of the fish. The tadpole's tail-fin is
somewhat liable to become too dry, to the detriment
of the circulation; it is therefore a good plan to lay
a thin scrap of glass over it to keep in a drop of
water which may be placed between; and this can
also be adopted with the fish.

The arranging of the frog involves much more
trouble, but being a most interesting and indeed
splendid object, it is worth taking some pains to
exhibit it. When once it is arranged, too, there is
none which can be shown with more certainty ; and
the frog being not out of its element the while, can be
kept longer in view than one would like to attempt

* The achromatic condenser is an arrangement by which the light
from the mirror can be directed with great clearness upon the object
examined, by placing an object-glass below the stage.

Circulation of the Blood. 143

with a fish or tadpole. It is to be placed in a little
bag, and this is to be tied on the brass " frog-plate/'
sometimes supplied with a microscope, or on the
wooden imitation of it, which can be very easily cut
out with a penknife. The shape is shown at No. 24,
g, and the bag may be also seen, containing the frog
with one foot left out, the claws of which are fastened
by bits of thread to some little wooden pegs. The
frog-plate must have two other pegs on the under
side to fasten it to the holes generally to be found in
the microscope's stage ; it should also have a square
hole over which the frog's foot is to be extended, and
I found it convenient that it should have some fixed
strings attached to it. The great point is not to give
the frog room to draw in its foot, and the pair of
strings tied in front of its head generally insure
this.

The circulation in small water-newts, and various
water larvae and crustaceans, may be easily shown by
placing them in the live-box with a drop of water.
No. 25 represents a small and singular crustacean,
called Daplmia pulex. The remarkable branching
appendages over its head are anfcnnce, or feelers ; and
it has but one eye, consisting of several lenses en-
veloped in a single cornea, which encloses them all.
The whole of the circulation may be seen, though in
a vague and rudimentary manner, in this little crus-
tacean. There is a rapidly beating heart near its
back, and from this colourless particles may be seen
flowing and performing a circuit of the whole frame.
Daphnia breathes not exactly by gills, " but by means

144

The Microscope.

of fringed plates on the outside of the third and fourth

pairs of legs."*

The circulation shows to vastly more advantage

with the vertebrated animals. Plate VIII. fig. 1, repre-
sents the three-spined
stickleback, slightly
smaller than nature,
and fig. 2 represents
a portion of its tail-fin
when magnified thirty-
five diameters. The
flat white spaces repre-
sent the bones, and it
will be observed that in
four places the blood-
vessels are carried
across these in fur-
^ rows excavated as it
were in the substance
No. 25.— Daphnia pnlex, magnified 16 of the bone. A vein
diameters, b, natural size.

and artery, placed in

pairs, may be observed at each side of the bones ;
and in some places these may be seen crossing
and recrossing each other in a fantastic manner.
The arteries may be recognized by their flowing
from the heart, and the veins by their flowing
towards it, as indicated by the arrows. The narrow
vessels connecting the large ones are the capillaries.

The pale, or rather colourless, appearance of the
corpuscles may surprise the observer. The fact is,

* Baird's "Nat. Hist, of British Entomostraca,"

Circulation of the Blood, in Stickleback and Frog.

Plate 8.

1. Stickleback. 2. Small portion of Stickleback's tail-fiu. magnified 35 diameters.

3 I'art of Frog's foot. 4. Minute portion of the web, magnified 100 diameters.

o. Capillaries in web of Frog's foot, magnified 5SO diameters

Circulation of the Blood. 145

that taken singly, they are but slightly tinged with
colour, and it requires the presence of several layers
of them to exhibit the well-known redness. A single
corpuscle, however, when seen edgewise, if it be a
large one, as that of a frog, will exhibit some depth of
colour, and the larger veins, where a great number
of corpuscles are flowing together, will appear of
a decided red. To illustrate this by an example
familiar to the microscopist, a dozen glass slides laid
on each other, or a single slide viewed edgewise, will
appear green, although any of these when laid flat
and looked through singly, will, if made of good glass,
appear nearly colourless.

The black markings and the star-like spots on the
fin are collections of pigment. Similar spots are
scattered over the web of the frog's foot on both
sides, but scarcely interfere with the view of the cir-
culation, because the lively movement of the latter
contrasts well with their stillness. But, as this con-
trast is wanting in a drawing, I have in the figures
omitted these spots, to allow the course of the circu-
lation to be traced without interruption.

The curious observer who will catch a full-grown
frog, and like to hold it when caught, may observe a
few little pink blood-vessels crossing the web. The
foot being tightly held, they will probably appear
quite as evident as in fig. 3 ; and the reason of this
will be that they are veins, and that the grasping
of froggy's ankle has impeded their circulation. If
the frog, reptile-like, shows signs of preserving an
apathetic stillness, the grasp may be relaxed, and

10

14G The Microscope.

the vessels will presently become much paler, because
the arrested blood will have recommenced its progress.
When the web is magnified about thirty-five
diameters, it affords a most curious spectacle. The
largest web in fig. 3 contained two principal veins
and an artery. This latter crossed the web where
the letter a is marked; it ran with amazing
rapidity in its broader parts, but at length ramified
into capiP«^ies, and slackened its pace. The two
veins moved much more slowly. They were well sup-
plied in their centres with corpuscles from the capil-
laries, and each vein flowed from about the centre of
the web towards the large veins placed above to the
frog's third and fourth toe. Thus the sinuous vein to
the left of a flowed downwards from a point parallel
to a, and upwards in a contrary direction; but I
noticed that the point of separation was not uniformly
in the same spot.

When a portion of the web is viewed with a
power of 100 diameters, it becomes evident that some
of the capillaries lie near the surface of the web —
some deeper in its substance, and some close to the
under surface. Some of these latter again, often
seem to find their way suddenly to the upper surface,
and cross over and under others without communi-
cating with them. Some of them are very small and
sparingly supplied with corpuscles; and these are
only visible occasionally when their existence is shown
by two or three stray corpuscles passing through
them. The substance of the web is not perfectly,
transparent, and seems, when the microscope is at the

Circulation of the Blood. 147

right focus for showing the capillaries, as if marked
with a sort of grained pattern (figs. 4 and 5).

The capillaries represented in fig. 4 are only those
which lie near the surface. An examination of the
arrows which mark their directions will show how they
all flow to a twisted vessel, which pours the corpuscles
received from them into the large red vein. The large
red vein ! — for, as viewed when highly magnified, it
is indeed a torrent — and they who use a microscope
learn to regard the distinctions of great and small
as only relative. But let us consider, relatively speak-
ing, how small these vessels must be. The space
represented at fig. 4 is magnified 100 diameters. In
the drawing it is two inches and a quarter wide, by
rather less than an inch and three quarters high. The
hundredth part of that is about one forty-fourth of an
inch by one sixtieth, a space that could be included,
with room to spare above and below, in the upper
loop of any small ' ' g )J in the page you are reading !

Remembering this extreme minuteness of the
capillaries, the feeling with which we look on them
when magnified, as in fig. 5, becomes one of deep
reverence, and the more so because we observe them
ministering to a directly beneficent purpose. It may
seem like a mere ' ' dealing in the marvellous " to draw
attention to the fact that the whole of the capillaries
represented at fig. 5, could be covered up by one of
the full-stops at foot of the plate ; but I do so, because
by no other method could I so readily convey a correct
impression of the real size of these vessels, and that
of the corpuscles which they contain.

148 The Microscope.

The young tadpole's gills begin to be sufficiently
transparent for microscopic observation when it is
about the size represented in No. 24, h. At that time
its tail is opaque, and the tail-fin or web very slightly
developed. The same tadpole's gills will on the
following day be seen to have grown, and during
about two days more they will show well, the tail-
fin also becoming broad and transparent, and circula-
tion showing well in every part of it. After this
time the gills begin to shrink in size (a process called
"absorption"), and can be observed (as I found)
during about six days in the same tadpole. No. 24, i,
shows the tadpole on the last day in which the
branchige are worth examining. The interesting
spectacle can, however, be observed each spring for
about three weeks in all in any locality, because
families of tadpoles in various stages of advancement
can be found in different ponds. By the time the
tadpole's gills have disappeared (being for a while
concealed under gill- covers, somewhat like those of
fishes) the circulation in the tail-fin, d, No. 24, has
become a most beautiful object, and it continues to be
so till after the tadpole has developed all its feet, and
assumed much of the angular outline of the frog.
After this time the tail begins to shrink in size,
becoming absorbed just as was the case with the gills.
The frog (as the creature must now be called), is a
droll-looking object, when leaping with about a
quarter of an inch of tail remaining; and in a few
days even this remnant will have dwindled away.

The circulation seen in the web of a tadpole's tail

Circulation of the Blood. 149

is that of the capillaries of the system, as in the fish
and frog. More than this can, however, be seen, as
appears by Mr. Whitney's account of " The Circula-
tion in the Tadpole," in the "Transactions of the
Microscopic Society," vol. x. 1862. The heart was
distinctly observed with its various vessels, and the
narrative may be read in Dr. Carpenter's work on the
microscope, accompanied by a figure of the tadpole.
Dr. Carpenter adds that it shows the structure just at
a time when the animal is neither fish nor reptile, and
is the more remarkable in a physiological point of
view. The great interest attaching to such an obser-
vation, when conducted with due knowledge of the
true points of inquiry, may excuse the training, or
rather starving process which was used to render the
tadpole transparent, and which is politely described as
an exclusively water-diet. For myself, I should feel
satisfied with the spectacle presented by the beautiful
little water-newt, which possessed the requisite trans-
parency without any special treatment.

The newt is called by Linnasus Lacerta aquatica,
or the water lizard, but is now correctly classed with
the amphibia, from its affinity to that group in various
respects, including the completeness of its transfor-
mation from the condition of a fish to that of a reptile.
For although it continues in its full-grown state to be
rather more aquatic in its habits than the frog, and
retains its long tail instead of losing it by absorption,
it exactly resembles the frog and toad in the early
possession of branchiae, which are subsequently lost and
replaced by lungs, suited for breathing atmospheric air.

150 The Microscope.

The name lissotriton, or smooth, newt, has been
given to this species, to distinguish it from a larger
one called triton, which has a rough skin. The lisso-
triton is a beautiful and harmless little creature. When
full grown it is about three inches long. The male and
female are curiously dissimilar. The former is spotted
like a trout, and during the spring and summer
possesses a handsome keel-like crest along its back,
and a broad tail, both of which shrink considerably in
the autumn. Its underside is tinged with orange, and
altogether it is a great beauty among the amphibia ;
whereas its mate is brown and unornamented, except
by two narrow lines of gold colour, bordered with
black. I describe them from drawings made some
years ago on the 26th and 27th of March.

The young smooth newt retains its external bran-
chiae to a much greater period than is the case with
the frog-tadpole ; although it would seem, from what
I have observed, and also from Professor BelPs
remarks on this subject, that there is a great variety
in the period at which the branchiae disappear in this
species. I have, however, constantly met these young
newts when nearly two inches in length, still possess-
ing these beautiful appendages, which, instead of being
pale, as at first, appear of a fine chestnut-orange
colour ; but they have lost much of their early trans-
parency, and therefore for microscopic observation the
newts answer best when of a smaller size. The great
size of the corpuscles, as compared with the size of tho
animal, makes the object exceedingly striking. They
are oval, like those of the frog, but larger, being (in

Circulation of the Blood. 151

round numbers), one eight-hundredth of an inch in
length, while those of the frog are one eleven-hun-
dredth ; and both these are singularly large compared
to those of man ; these latter are but one three-thou-
sand two-hundredths of an inch in diameter.

The little newt was much more tractable than the
tadpole when placed in the live-box. It would remain
perfectly still for several minutes at a time and showed
no signs of discomfort. It was so small, and in
appearance so fragile, that I never touched it with
my hands, but always caught and lifted it with an ex-
temporized paper spoon, and poured it on to the live-
box. On looking attentively one day at its under
side, before placing it for inspection in the micro-
scope, I could distinguish a delicate pink spot
apparently fading and reappearing a number of
times every minute. The circulation in the branchiae
was then a familiar object to me, and was similar to,
but more beautiful than, that of the young tadpole. I
was also familiar with the appearance of the circula-
tion in the little newt's broad tail — but this pink spo'
was something new to me, and was doubtless th(
heart, centre and origin of the movement which I had
hitherto traced only in detached portions. My sup-
position proved correct ; and I hope some reader may
be led by these remarks to capture and examine a
little water-newt — and proceed much further than my
limited knowledge permitted me to do, in recording
the details of the wonderful spectacle which it presents
to view.

152 The Microscope.

And here my Microscopic Teachings end. But,
reader, shall we not rather say, HEEE THEY BEGIN ?
A teacher who truly loves his art or science is best
pleased when those whom he has instructed outdo in
after years their early lessons. And such is my feel-
ing about this little book. I wish that those who
read it may enter on many fields of observation to
which I have not directed them — for instance, the
productions of the sea, a mine of interest ! — and also
that they may study the objects which I do describe in
more completeness, and with a far deeper understand-
ing of their meaning than I have done. If my book
has helped to place them on the way to such studies,
as may enable them to add to the general stock of
knowledge, I shall not regret the time and application
it has cost me — not as it might once have been, as
the delightful employment of abundant leisure, but, on
the contrary, a serious occupation, done amidst inter-
ruptions and under pressure of numerous home duties,
in the feeling that I had a few things to say which
might be pleasant and instructive to some readers at
the present time, and to my own dear children by and
by. To those readers I commend it, hoping that it
will assist them in the study of Nature ; hoping, too,
that it will suggest thoughts which the heart can feel
more readily than the tongue can speak them, of the
unsearchable greatness of Him who made these
things.

INDEX.

PAGE

Animalcules, abodes of 106

Aquarian Microscope 113

Bell-flower Animalcule... 112, 121

Birds, down of 59

Blood, circulation of 138

Boat-fly 76

Brimstone Butterfly 42

Burnet-Moth 39

Camera Lucida ,. 20

Camera Obscura, eye com-
pared to 64

Canada Balsam 26

Carchesium 125

Cells, development from ... 52

Cilia 122

Coal 93

Coddington Lens 3

Collomia Seed, spiral fibre of 83
Compound Eyes of Insects... 68
Corpuscles, paleness of ...... 144

Condensing Lens 11

Cricket, eye of 74

Crustaceans, circulation in... 143
Crystalline Lens, fibres of ... 65

Crystallization, to view 96

Crystals 95

Cuticles of Plants 81

Deer, hair of 57

Diameters, meaning of 31

Diaphragm Plate 16

Diatoms and Desmids 85

Diatoms as Test-objects 118

PIG*

Diatoms fossil y3

recent 01,115

Dipping Tube, to use 113

Dragon-fly, eye of 69

wing of 34

Drawing 20

Earwig, wing of 30

Eel, scales of 47

Emperor Moth 41

Epistylis 125

Eyes, care of the !<>

Eye, structure of .".... 64

Feather, booklets of 60

Fern-seed 87

Fishes, circulation in 140

Fish, eyeof « 62

Floscule 131

Flowers, mode of viewing ... 80

Fly, foot of 75

Foot of Frog to observe, 138
142, 145

Foraminifera 94

Fossil Trees 92

Frog Spawn 108

Geranium, petal of 85

Ghost Moth 38

Glare, plans for moderating.. 13

Green Forester-Moth 38

Hair, root of 58

structure of 53

Hairs as opaque objects 59

154

INDEX.

PAGE

IleliopeUa 120

Herald Moth 41

Human Hair 57

Illumination of Objects 11

Infusoria 114

Insects, concealed wings of. . . 30

eyes of 68

hairs of 59

Jaws of Rotifer 130

Lamp for Microscope 11

Lieberkuhns 16

Limestone, animal remains in 94
"linear and Superficial

Measures 31

Live-box 17

Lobster, eye of 74

Magnifying Glass 2

Melicerta Ringens 131

Micrometer 102

M icroscope, binocular 8

— . care of the 18

compound 5

oxy hydrogen ... 8

• simple 2

solar ... 7

Microscopic Objects, L.

Clarke on 50

Microscopic writing 103

Mirror, use of 11

Mounting Objects 20

Mouse, hair of 53

Musk Deer, hair of 57

Navicula 117

Nobert's Tests 103

Object-glasses, powers of ... 7

Objects, collection of 20

Otter, hair of 54

Perch, scale of 45

Philodine 135

PAGK

Photographs, Microscopic ... 100

Polarization 46

Pollen 84

Pond-life, Marvels of 106

Protococcus 115

Quill, internal structure of... 53

Red Admiral Butterfly 42

Rhizopods 115

Rotifera 114

Salpina 136

Scales of Insects 37

Sole, scale of 45

Spider, foot of 75

Spring Water, no animal-
cules in 105

Stage-forceps 17

Stentors , Ill, 124

Stickleback, to observe 140

Stylonichia 127

Tadpole, to observe circula-
tion in 138, 148

to observe pills

of 110, 138

Tardigrada 136

Test-objects 43, 119

Trichopteryx, wing of 35

Vallisneria, rotation in 82

Vorticelte 112,121

Wasp's Wings 34

Water Bear 136

Water Newt, circulation in... 143

Weevils, scales of 43, 44

Wheel animalcule 129

Wheel- movement, apparent 122
1?9

Whirligig Beetle 32, 77

White Mouse, hair of 53

Yellow Underwing Moth ... 41

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