The microscope, and some of the wonders it reveals

UC-NRLF

B 3 10 fl 177

ftr

THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

PRESENTED BY

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

TH E

MICROSCOPE,

AND SOME OF THE

WONDERS IT REVEALS.

REV. W. HOUGHTON, M.A., F.L.S.

SECOND EDITION.

CASSELL, FETTER, & GALPIN,

LONDON, PARIS, AND NEW YORK.

LONDON

CASSELL, FETTER. & GALPINT, BELLE SAUVAGE WORKS,

LUDGATE HILL, E.G.

673

CONTENTS.

CHAPTER I.

Introduction- Researches of Leuwenhoek, Grew, and Mal-
pighi — Simple Microscopes — Compound Microscopes' —
Object-glasses — Necessary Apparatus — Binocular Micro-
scopes— Instructions in use of Microscope . . Page I

CHAPTER II.

The Microscope in Botany — Vegetable Cells — The Yeast
Fungus — Circulation in the Cells — Hairs — Raphides —
Spiral Vessels — Stomata ..... Page 17

CHAPTER III.

Sections of Stems, Roots, &c. — Pollen Grains — Germ Cells
of Fucus — Spores of Fungi — Difference between Spore
and Seed — Spores of Horse tails (Equisetacece} — Seeds
of various Plants — Diatomaceee and Desmidiacei~e —
Volvox Globator ...... Page 27

CHAPTER IV.

Difference between Plant and Animal— Professor Huxley
on Protoplasm — yEthalium Septicum — So-called Monads
— Collecting Apparatus— Infusoria — Ophrydium- — S ten-
tors — Vorticella — Wheel Animalculae— Melicerta Page 3^

CHAPTER V.

Stephanoceros and Floscularia — Hydrae — Parasite on Hydne
— Tardigrades — Tenacity of Life in Tardigrades. Page 48

CHAPTER VI.

Circulation of the Blood as seen under the . Microscope in
Tadpoles, Young Newts, Young Fish, Foot of Frog,
various Larvae — Organs of Insects — Eye of Fly — Mouths
of Insects . . . . , . . . Page 56

M36O105

IV CONTENTS.

CHAPTER VII.

Organs of Insects — Wings — Function of the Halteres —
Drum and File of House Cricket— Foot of Fly— Hind
Foot of Bee — Stings and Ovipositors — Spiracles and
Tracheae Pap 71

CHAPTER VIII.

Eggs of Insects — Of Butterflies, Water Scorpion, Man-
gold-wurzel Fly, Gnats — Hairs and Scales of Insects,
and of Fish— Structure of Human Hair, of Bat's Hairs,
of Musk Deer— Structure of Bone . . . Page 81

CHAPTER IX.

Structure of Skin — Pigment Cells— Change from Black to
White in Negro — Perspiratory Glands and Ducts —
Blood Corpuscles — The Microscope in detecting Adul-
terations in Food and Medicine — Crystals . Page 92

CHAPTER X.

The Microscope in Geology— Fossil Diatomaceae— Fora-
minifera — Polycystina — Deep-sea Soundings — Chalk —
Globigerinae — Sponges in Flint— Xanthidia in Flint —
Eozoon Canadense ...... Page 105

CHAPTER XL

Vegetable Origin of Coal — Mineral Composition of Rocks
— Nature of Animals ascertained by Examination of
Minute Fossil Parts — Old Red Sandstone of Russia
determined by a Microscopic Section of a Tooth — Iden-
tity of the Keuper Sandstein of Wurtemberg with the
New Red Sandstone of Warwickshire similarly deter-
mined Page 116

CHAPTER XII.

The Collecting and Mounting of Objects — Test Fluids —
Conclusion Page 123

THE MICROSCOPE.

CHAPTER I.

INTRODUCTORY.

I AM supposing, reader, that at present you are almost,
if not altogether, unacquainted with the use of that
wonderful instrument by means of which objects quite
invisible to the unassisted eye become distinctly seen,
and their minutest structure understood. It will be
my endeavour in this little Elementary Hand-book on
the Microscope, its construction and revelations, to
put you in possession of such knowledge as shall serve
as a basis for further information, and a stimulant to
unceasing inquiry.

The word microscope is of Greek origin, being
derived from two words, n<Kpoc, "small," and <nco7reW)
" I view." Its name, you will see at once, most
appropriately describes its use. I need say very*
little of its history. Simple microscopes or magnify-
ing-glasses were known to the ancient Greeks and
Romans ; while compound microscopes were not in-
vented before the end of the sixteenth century. In
process of time this instrument, through the successive
labours of various men of different ages, has become
developed into a very valuable instrument of scientific
research, whilst the success that has crowned the efforts
of microscope-makers during the last thirty years has

6 THE MICROSCOPE.

been truly marvellous. There is one point in the
history of the microscope which it would be well to
bear in mind, because it may show you how much
may be done by honest and persevering workers
with even inferior instruments. Those who are
acquainted with the researches of Leuwenhoek,
Grew, and Malpighi, all frequent writers in the early
volumes of the Philosophical Transactions, are struck
with astonishment at the discoveries they made with
instruments so much inferior to those in use at the
present day. Truly has an eminent living microscopist
and biologist observed with regard to the researches
of Leuwenhoek, " That with such imperfect instru-
ments at his command, this accurate and painstaking
observer should have seen so much and so wetl as to
make it dangerous for any one, even now, to an-
nounce a discovery without having first consulted his
works, in order to see whether some anticipation of it
may not be found there, must ever remain a marvel
to the microscopist." Of the labours of Grew and
Malpighi the same writer remarks — "Both were at-
tended with great success. The former laid the
foundation of our anatomical knowledge of the vege-
table tissues, and described their disposition in the
roots and stems of a great variety of plants, besides
making out many important facts in regard to their
physiological action ; the latter did the same for the
animal body, and he seems to have been the first to
witness the marvellous spectacle of the movement of
blood in the capillary vessels of the frog's foot, thus
verifying by ocular demonstration that doctrine of
the passage of blood from the smallest arteries to the
smallest veins, which had been propounded as a ra-
tional probability by the sagacious Harvey."*

A simple microscope is familiar to everybody in the
Carpenter on the Microscope, third edition, p. 2, Introduction.

INTRODUCTORY.

form of a reading-glass or hand-magnifier; perhaps
the most useful form for the pocket consists of one
or more lenses, which shut up in a tortoiseshell or
horny frame, with an intervening perforated plate
to act as a diaphragm when the lenses are used alto-
gether. The micrpscopist should never be without
this little pocket-magnifier ; it will be very useful in
examining samples of water containing animalculae,
revealing to him the
presence or absence of
some particular kinds
he maybe in search of,
or enabling him to gain
some clearer idea of the
structure of a fern, grass,
or flower, than the un-
aided eye can afford.
Simple microscopes,
properly so called, are
supported on stands.
That one known as the
Society of Arts Simple
Microscope, manufac-
tured by Mr. Field,
of Birmingham, is a
useful form of simple microscope. It has a tubular*
pillar about five inches high, which screws into the
lid of the box which contains the instrument when
not in use ; a concave mirror is fixed at the lower
end of the pillar, while the upper end carries the stage
and a short horizontal arm in which the lenses, three
in number, may be screwed. A condensing lens, for
opaque objects, can be fitted into any of the four holes
with which the stage is perforated. This instrument
has a range of powers from 5 to 40 diameters.

What is the difference between a simple and a

A Simple Microscope.

THE MICROSCOPE.

compound microscope ? It is this : in the simple
microscope you look directly, through the lens, at
the object; in the compound microscope you do not

look directly at the
object, but at its
image, which has
been magnified by
another lens placed
between the ob-
ject and the lens,
or "eye-piece,"
through which you
are looking. Of
course, great mag-
nifying power is
thus obtained.

Here is a figure
of a microscope;
it represents Na-
chet's smaller com-
pound microscope.
From a careful
study of this figure
you will soon be
able to learn the
parts of which it
consists, and will
gain a general idea
of what a com-
pound microscope
is. It stands, as
you see, on a broad foot, a, out of which a pillar, £,
arises ; at the top of this is a joint, h, supporting the
stage, c, and another pillar, d, which carries the body,
/ with which it is connected by a transverse arm, e.
The body slides up or down within the ring of the trans- *

A Compound Microscope.

INTRO D UC TOR Y. 9

verse arm, like a telescope ; this motion is for coarse
focussing. For fine adjustment it is moved by a milled
head, g, which acts upon a screw inside the pillar d.
The joint at h enables the observer to place the instru-
ment at any angle he may require. The mirror, for
throwing light through transparent objects, is seen at
k ; a condensing lens, for throwing light upon opaque
objects, is seen at i. So much for the mechanical
arrangement. But where are the most important parts
of the microscope — the lenses, upon the combination of
which the magnifying power of the instrument depends?
These lenses, which are known by the names of " ob-
ject-glasses " and " eye-pieces ;; respectively, fit, the
former by a screw, into the bottom of the body, /; the
latter, m, by sliding into its top portion. I would
advise you to learn the names of these different parts
of a compound microscope. Of course, I need hardly
tell you that there is great difference in the forms of
compound microscopes, their mechanical arrange-
ments, and so on; but the above description will
seive to give you a fair idea of the general plan of a
compound microscope.

Let us now look a little more closely into the struc-
ture of the lenses, on which the magnifying power of
the microscope depends. I have already told you that
these are known by the names of " eye-pieces " and
"object-glasses," or "objectives," as they are some-
times termed. The names are easy to remember and
explain their respective uses, the former being looked
through by the eye of the observer, the latter being
placed near the object you wish to examine. The ordi-
nary eye-piece consists of two plano-convex* glasses,
the plane surfaces of each being directed upwards.
That one near the eye is the " eye-glass," the one at

* A plano-convex lens is one which has one of its surfaces plane
or flat, the other convex.

IO THE MICROSCOPE.

the greater distance is called the "field-glass." The
object-glasses consist of three lenses, one of which is
constructed to correct certain optical defects or
"aberrations." Each of these three sets of lenses is
itself compound ; and upon the excellence of the lenses
especially the merits of a good microscope depend.
They ought to define objects with great clearness ;
there must be no haziness about the outlines of the
images, and plenty of light must be secured. If you
notice any coloured rings encircling any object you
are inspecting, your object-glass must be discarded ;
it has not been corrected for this defect, which is
known as " chromatic aberration," and will prove of no
value to you. The microscopist will find two object-
glasses quite sufficient to begin with ; perhaps the inch,
which will magnify, with No. i eye-piece, 30 or 40
diameters, and the quarter of an inch, which, with
the same eye-piece, will give a power of about 200
diameters, will be found the most generally useful.

I need hardly tell you that a microscope should be
perfectly steady, whether the body be inclined at any
angle or stand in a vertical position ; no vibration
should be communicated to the body when the ad-
justment screws are turned for the purpose of focus-
sing. Every microscope should be capable of being
used in three different positions — vertical, inclined,
and horizontal. Nachet's microscopes formerly could
be used only with the body in a vertical position — -one
which is very trying to the muscles of the neck of the
observer if he is working for some hours at a time ;
they are now made to assume the three positions.
Then, again, the stage is a very important part of the
instrument ; it should be three* inches long, by two
and a half broad. Nachet's instruments are too small
for working conveniently. Underneath the stage of
every microscope there should be a revolving circular

AV7Y? OD UC TOR Y. l^

plate, called a diaphragm, in which there are holes of
various sizes for the regulation of the required light
for transparent illumination ; the observer, however,
will often find he can obtain just the quantity and
quality of light required without a diaphragm, by in-
clining the mirror at various angles, or by shading it
occasionally with the hand. A beginner will often
find difficulty in getting the focus. Many instruments
are provided with two adjustments for altering the
focus ; these are the coarse adjustment, which is
effected by rack-and-pinion motion ; and the fine ad-
justment with very delicate motion. In some micro-
scopes the coarse adjustment is obtained by moving
the body of the instrument with the hand, as in the
figure represented ; but that effected by the rack and
pinion is far more pleasant to use.

For the illumination of opaque objects, the con-
densing lens attached to the instrument will be found
useful, but, in addition to this, it is very desirable to
employ another condensing lens, mounted on a sepa-
rate stand, and readily moved in any direction. That
known as the bulPs-eye condenser is very convenient
and useful ; the lens is a plano-convex one, about
three inches in diameter, having a short focus. This
lens must be turned with its plane surface to the light
or lamp, and its convex side towards the object on
the stage of the microscope — experience will determine
the requisite distance : the rays of light passing through
the bull's-eye will form a bright luminous spot upon
the object. There are various other contrivances for
illuminating opaque objects, but the beginner need
not trouble himself with them ; the more simple and
the fewer the appliances, the more progress the stu-
dent will at first make. I have enumerated, I think,
nearly all the apparatus you will find necessary, unless
I mention a earner a hicida, or a neutral tint glass

12 THE MICROSCOPE.

reflector, for drawing the outlines of the magnified
images, or for measuring the objects. The camera
lucida is a four-sided glass prism, set in a brass frame
with a short tube. It is used in this way : you must
take off the cap of the eye-piece, and slip the tube of
the camera upon the top of the eye-piece ; arrange the
microscope in a horizontal position, and look through
the camera at a sheet of paper on the table on
which you are working ; the magnified image of the
object on the stage of the microscope will appear as
if it were on the paper below. With a finely-pointed
pencil you then proceed to take its outline; do not
be disappointed if you cannot see both the image and
the pencil ; persevere, and in a short time you will
succeed in making your drawing. The neutral tint
glass reflector, which is cheaper than the camera lucida,
consists of a small piece of slightly coloured glass
which fits on the top of the eye-piece ; the micro-
scope must be inclined, as before. With a little
practice the draughtsman will be able to draw the out-
lines on the paper.

The polarising apparatus, by means of \vhich
various splendid colours are made to appear, is a
luxury which the beginner may readily dispense with ;
though the effects produced, especially when a thin
plate of selenite is interposed between the analyser
and polariser, are often extremely beautiful ; and
though no doubt in some cases the internal structure
of transparent objects is rendered very evident, yet
for general microscopic work the polarising apparatus
is not necessary.

Various lamps have been suggested as convenient
forms for illumination. I do not think you need
trouble yourself about a choice ; a moderator or
paraffin will serve your purpose well ; only take care to
use a lamp, and not candles, the constant flickering

INTR OD UC TOR Y. 13

of which is trying to the eyes and irritating to the
temper. You should provide yourself with the fol-
lowing necessary accessories to the microscope, (i)
A number of plate-glass slides, three inches in length
and one in breadth; they can be bought with the
edges ground at about six shillings a gross. On these
slides are to be placed the objects you may wish to
examine, or to mount for preservation. (2) A quan-
tity of thin glass of various degrees of thickness, cut
in either square or circular pieces of different sizes.
Thin sheets of this glass, called "cylinder glass," are
manufactured by the well-known firm of Messrs.
Chance, of Birmingham, but they can be procured
at any optician's. The pieces should be kept in
a box with bran or sawdust to prevent them break-
ing, for they are extremely brittle. When an object
is placed on a glass slide for examination it should
always be covered with a piece of this thin glass, in
order to protect the object-glass from injury ; whilst
examining drops of water this is especially necessary.

It would not be easy to do much work satisfactorily
without dissecting-needles and a pair of forceps. The
dissecting-needles are extremely useful instruments for
unravelling entangled objects and various tissues; they
can be readily improvised by the student taking some
well-tempered needles, nipping off a portion of the
heads, and inserting the upper part of the remainder
in wooden handles. The forceps may be used inde-
pendently, or be attached to the stage, for the pur-
pose of holding minute objects under the microscope ;
its form will suggest to you various uses to which it
may be applied.

A few watch-glasses will be found convenient for
several purposes, and some small glass shades, about
five inches in diameter, are useful for protecting from
the dust objects you may be ''mounting." I will

THE MICROSCOPE.

make a few remarks on the "mounting" of micro-
scopic objects in another chapter.

The microscope depicted in the adjoining woodcut
represents one of Nachet's stereoscopic binoculars.

The stereoscopic
effect is produced by
a peculiar Arrange-
ment of prisms. The
binocular microscope,
though it can hardly
be regarded as ne-
cessary for the stu-
dent, is veiy useful
in the examination
of opaque objects of
solid form, and also
of transparent ob-
jects, when we wish
to ascertain the dis-
tinction between
their nearer and more
distant surfaces. The
prolonged use of a
binocular is attended
with less fatigue than
that of the monocular,
and should you de-
sire to procure one,
Messrs. Beck and
Beck, or Mr. Crouch, or Mr. Collins, or any other
well-known maker, will supply you with an excellent
one at the cost of about ten or twelve pounds. An
ordinary monocular microscope can be converted into
a stereoscopic binocular, should you desire it. The
woodcut in page 15 represents three observers using
one of the triple- bodied microscopes of M. Nachet.

A Binocular Microscope.

INTRODUCTORY.

I will now give you a few short instructions in your
use of the instrument. Let it be inclined at a con-
venient angle, screw on your low-power objective, and
slide the eye-piece into the tube at the top of the
body, having previously taken care to see the lenses

Triple-bodied Microscope.

are free from dust; place the object you wish to
examine on a glass slide, and transfer it to the stage
of the microscope ; you will soon learn to obtain the
proper focus. If your object is a transparent one,
you must turn the mirror under the stage until a clear
circular light illumines the field of view; if your
object is opaque, you must use the condensing lens or
the bull's-eye condenser, and throw the light upon the

1 6 THE MICROSCOPE.

object. I should recommend you to practise yourself
with the examination of objects that require low
powers for some time before you try your hand on
such as require high powers and very accurate and
fine focussing. You will at first mistake small particles
of dust, perhaps, for something connected with the
object you are examining. In the examination of
drops of water, numerous bubbles of air will present
themselves in questionable shapes, and you will won-
der what they are. In placing the thin glass over the
drop of water, be careful to let its edge first touch the
water, and then let it slowly fall on it. The surplus
water should be wiped off, and care must be taken
that the upper surface of the cover does not get wet,
otherwise, if you are using a high power, you will get
a misty view. Carelessly dropping or flopping the
cover upon the drop of water is sure to produce air-
bubbles, which may sometimes interfere most inop-
portunely and inconveniently with your getting a good
view of the organ of some restless little animalcule.
Never interfere with the lenses of the object-glasses;
all that is necessary is to wipe the lower surface with
a clean bit of wash-leather. Never leave the object-
glasses uncovered when not in use, and never examine
a drop of water without a thin glass cover over it.
Do not touch the lenses of the object-glasses, or you
will make them dim and misty. Attention to these
instructions will repay you for your trouble, and save
disappointment and probably expense.

CHAPTER II.

USE OF THE MICROSCOPE IN BOTANY.

IT is almost impossible to exaggerate the value of the
microscope in vegetable physiology, and the amount
of information regarding the minute structure of plants
which has been obtained by this instrument. You
cannot, I think, do better than begin your microscopic
studies with some of the various forms of plant-life
that occur abundantly in our ponds, rivers, and
ditches. Many of these are of very simple construc-
tion, and you may proceed from the investigation of a
plant which has a separate existence as a single cell,
to that of such complex and highly differentiated
forms as the oak, the ash, and other mighty trees of
the field or forest. Now the microscope will reveal
to you the interesting fact that the origin of every
plant is a single cell. Dr. Carpenter has well said,
u The plan of organisation throughout the vegetable
kingdom presents this remarkable feature of uni-
formity— that the fabric of the highest and most
complicated plants consists of nothing else than an
aggregation of the bodies termed cells, every one of
which, among the lowest and simplest forms of vege-
tation, may maintain an independent existence, and
may multiply itself almost indefinitely, so as to form
vast assemblages of similar bodies. And the essen-
tial difference between the plans of structure in the
two cases, lies in this : that the cells produced by the
self-multiplication of the primordial cell of the proto-
phyte, are all mere repetitions of it, and of one
another, each living by and Jor itself; whilst those

B

1 8 THE MICROSCOPE.

produced by the like self-multiplication of the pri-
mordial cell in the oak or palm, not only remain in
mutual connection, but undergo a progressive ' dif-
ferentiation ; ' a composite fabric being thereby de-
veloped, which is made up of a number of distinct
organs (stems, leaves, roots, flowers, &c.), each of
them characterised by specialities, not merely of ex-
ternal form, but of intimate structure (the ordinary
type of the cell undergoing various modifications), and
each performing actions peculiar to itself which con-
tribute to the life of the plant as a whole. Hence,
as was first definitely stated by Schleiden, it is in the
life-history of the individual cell that we find the true
basis of vegetable life in general."* What a marvel
for contemplation, this vegetable cell, this living atom,
endowed with such extraordinary and diversified power
of reproduction !

The cells, as Pouchet observes, " represent little
microscopic vesicles, at first globular, but which by
increase and mutual compression become many-sided.
And these elements, which conceal themselves from
our eyes, animated by an inconceivable plastic force,
and multiplying at a prodigious rate, cause new worlds
to arise. ' Give me a lever and a fulcrum,' said
Archimedes, 'and I will lift the globe.' M. Raspail,
almost paraphrasing the geometer of Syracuse, was
able to say, ' Give me a living cellule, and I will re-
produce all creation.' "

You can readily make yourself acquainted with the
form of a simple cell and its growth, by placing a very
small quantity of fresh yeast under the microscope,
with a power of 400 diameters. The whole substance
seems to be nothing but an aggregation of these
minute cells. Look at them ; each is like a little

* " The Microscope," p. 241. Fourth Edition.

USE OF THE MICROSCOPE IN BOTANY. 19

globe, and — like most vegetable cells— consists of a
membranous bag with some fluid contents. The
vegetable cell-wall is generally composed of two layers
having different properties and composition. They
are excessively thin, and difficult of detection, unless
you add iodine or other colouring matter. The inner
layer, which can only be separated from the outer one
"by developmental changes, or by the influence of
re-agents which cause it to contract by drawing forth
part of its contents," is called the primordial utricle,
as " being first formed and most essential to the
existence of the cell." The outer cell is supposed to
be merely a protective covering ; the contents of the
cell consist of colourless protoplasm (organisable
fluid), containing albuminous matter in combination
with starch, gum, sap, and a green, oily substance
called chlorophyl. But let us return to the yeast cells.
They are still of the same form as when we looked at
them before, and independent of each other. I will
add a little newly-made beer, or some albuminous
matter mixed with sugar, and what do we see after the
interval of a few hours ? No longer single uncon-
nected globules, but a number together forming
chains. Each cell has budded out one or two little
projections, which have developed themselves into
complete cells, in their turn giving origin to fresh ones,
and so on continuously as long as the fermenting pro-
cess continues. When this is stopped, the yeast-plant
— it is a fungus called Torula cerevisicz — returns to its
isolated condition once more. In quoting an extract
from Dr. Carpenter, I mentioned the term protophyte*
The yeast fungus is a good example of organisms
designated by this word, which, as its derivation
shows, is intended to define the most simple, primi-

* From TrpoiTor, " first," and <J>VTOV, "a plant."

B 2

20

THE MICROSCOPE.

tive, and elementary forms of vegetation. Vegetable
cells are of various shapes and sizes ; they may be
globular (Fig. i), or square, hexagonal (Fig. 2), cy-
drical (Fig. 3), spindle-shaped,
&c. &c. Sometimes the cell-
walls grow unequally at different
points, so as to produce angular
projections by which the cells
cohere ; or they grow out into
long arms, thus producing stel-
late cells, as in the pith of the
rush, a thin section of which,
when viewed by reflected light,
is a very pretty microscopic object. Thin sections of
any soft vegetable tissues are readily made with a
razor or very sharp knife. Starch is found abun-

Fig. i.— Globular Cells.

Fig. 2.— Hexagonal Cells.

Fig. 3.— Cylindrical Cells.

dantly in the cells of a great many vegetables. The
granules vary much in form and size, and are gene-
rally so characteristic of the plants, that it is an easy
matter to detect, by means of the -microscope, adul-
terations in food. Fig. 4 represents a thin section of
a potato, showing the cells and starch-granules con-

USE OF THE MICROSCOPE IN BOTANY. 21

tained therein. Starch is the most generally diffused
substance, except protoplasm,* met with in vegetable
cells ; it occurs in all classes of plants, except funguses.
It can always be detected by the application of iodine,
which immediately turns the granules blue. I should
recommend you to make yourself acquainted with

Fig. 4. — Section of Potato, showing Cells and Starch Granules.

various forms of starch-granules of several common
plants, such as wheat, rice, Indian corn, and arrow-
root. It is supposed by some microscopists that the
structure of a starch-granule is composed of a series
of concentric shells or layers, which are firm as they
approach the outside wall, but are less dense and
more full of water as they approach the centre or
nucleus. The granules may be isolated from the
cells by macerating slices in water for a few days.

* The name is applied to the nearly colourless granular viscid
substance, nitrogenous in nature, which constitutes the formative
matter in the cells. From Trpwror and 7r\tto-/ua, " form."

22 THE MICROSCOPE.

One of the largest forms of starch-granules is that of
tons-. Jes-mois ( Canna ) .

The circulating movement of particles in the cells
of certain plants is an extremely interesting sight, and
in some can be observed without much difficulty.
Those generally selected for exhibiting this phenome-
non are Char a nitella and the American weed Ana-
charis alsinastrum. The long ribbon-like leaves of
Vallisneria spiralis — a plant not indigenous in this
country, but which may be purchased in Covent
Garden and elsewhere — show this cyclasis, or circu-
latory movement, of chlorophyl particles admirably.
You must take a very thin strip or layer from the
surface of a youns: leaf, using a sharp knife ; place
this upon a glass slide with a drop of water, and cover
it with very thin glass, using a power of 300 or 400
diameters. The circulating corpuscles will be seen to
traverse the cell-walls round and round. Should the
circulation stop, you should submit the strip to gentle
heat, when it will go on again. The hairs of certain
plants exhibit the same phenomenon, such as those
of Tradescantia Virginica, the Virginian spider- wort ;
Anchusa paniculata, one of the borage family ; the
young hairs of the nettle show the same rotation
under a very high power. Crystals, or raphides as
they are termed, are found in many plants, and are in-
teresting microscopic objects. The name " raphides,"
from the Greek word r aphis, "a needle/' was first
applied to crystals having a needle-like form; but it
is now used in a general sense to express any crys-
talline formation. These bodies are found usually
within the cells in almost any part of the plant —
in the stem, leaves, bark, or pith. In the bulbs of
the lily tribe they occur extensively. You can readily
see them in the cuticle of the common onion ; strip
off a small piece, and view it with a power of

USE OF THE MICROSCOPE IN BOTANY. 2$

about 200 diameters, and you will notice some very
pretty groups of octahedral or prismatic crystals.
They are generally composed of oxalate of lime, or
of carbonate, sulphate, and phosphate of lime. Dr.
Carpenter says that "certain plants of the cactus
tribe, when aged, have their tissue so loaded with
raphides as to become quite brittle, so that when some
large specimens of C. senilis, said to be a thousand
years old, were sent to the Kew Gardens from South
America, some years since, it was found necessary for
their preservation during transport to pack them in
cottcn like jewellery."* What office these crystalline
bodies fulfil, or whether they fulfil any at all, is not
known. Raphides have been artificially produced
within the cells of rice-paper. Mr. Quekett filled the
cells with lime-water by means of an air-pump, and
placed the paper in weak solutions of oxalic and phos-
phoric acids. " The artificial raphides of phosphate
of lime were rhombohedral ; while those of oxalate
of lime were stellate, exactly resembling the natural
raphides of the rhubarb."

The spiral vessels of plants will amply repay you for
investigation by their extreme beauty : they are easily
seen by macerating the stems or leaves in water, or
by boiling them. These spiral vessels are cylindrical
tubes with cone-like ends, within which fibres wind in
a corkscrew fashion. In some cases the tube contains
only one spiral fibre ; in others as many as twenty
have been counted (Fig. 5). These vessels are found
in all parts of plants excepting the roots. They a-e
very beautiful in the seeds of certain plants, as in the
strawberry and hazel-nut. Every one is familiar with
the brown coating that surrounds the common nut ;
scrape a portion of this membrane off the kernel, and

* " The Microscope," p. 400.

THE MICROSCOPE.

soak it in water for a time ; tear it in pieces with a
pair of needles, and examine under the microscope
with reflected light, you will see a great number of
glistening fibres. It seems probable that the use of
these spiral vessels is to convey air to the plants, thus

Fig. 5 — Spiral Vessels.

Fig. 6.

forming a system of internal respiration, which at once
suggests an analogy to that of insects, the tracheae of
which very closely resemble the spiral vessels in the
vegetable kingdom. Spiral vessels, however, are some-
times found to convey fluid. The various kinds of
ducts, or the canals through which fluids are carried
to different parts of plants, will form objects for study ;
spiral, annular, dotted, scalariform, and reticulated
ducts are interesting varieties of form.

Among other important organs, the stomata, or little
openings by which almost all leaves with distinct
cuticles are perforated, must be mentioned. These
organs are really mouths through which respiration

USE OF THE MICROSCOPE IN BOTANY. 25

and exhalation are carried on in plants ; they lead
into cavities beneath the epidermis. The usual form
of the stomata consists of a number of rounded cells,
bordering the opening, with a couple of kidney-shaped
cells of a large size in the centre ; between these is a
narrow slit when the mouth is open, and a raised seam
when it is shut. In some plants the stomata do not
open on the surface of the leaf, but lie in depressions
in it ; these are lined and guarded with a number of
hairs, as in the oleander (see Fig. 6). You would do
well to make yourself acquainted not only with the
function, but the various forms of the stomata. The
examination of their structure is easy. Take a leaf
or flower of almost any plant, tear a thin slice off its
under surface, put it in a glass slide with a drop of
water, cover it with thin glass, and use a power of
about 200 diameters. Examine the outer surface of
the object first ; then you will see the cells and slit
of which I spoke. Now examine the other side, and
notice the cavity into which the slit is directed.
Stomata are usually more abundant on the lower sur-
face of leaves ; but in plants whose leaves float on the
water they are found only on the upper surface, as In
the water-lilies ; in plants whose leaves are always
submerged there are no stomata ; in grasses and such
plants as grow in an erect form they are found on both
surfaces equally distributed. As many as 160,000 of
these little mouths have been counted on each square
inch of surface on leaves of some plants. In the
liverworts, as in Marchqntia polymorpha, the stomata
are of very complex structure. These organs are not
found in the roots of plants, nor in the ribs of the
leaves : and they are absent from fungi, lichens, and
sea-weeds.

The study of hairs, which are so abundant on many
plants, will afford you much pleasure and instruction,

26

THE MICROSCOPE.

so variously formed and beautifully constructed as the
microscope shows them to be ; they are generally
attached to the cuticle by one end, having the other
one free. To the naked eye the hair of the Trades-
cantia Virginica, for instance, looks like a single thread-
like process ; under the microscope it is found to
consist of three or four successive cells. I ought to
say that vegetable hairs are always of a cellular cha-
racter. Some
hairs appear to
be attached to
the epidermis by
their centre por-
' tion, and assume
very pretty stel-
late or starlike
forms. Such cases
are, no doubt,
merely clusters
of hairs each
attached by its
lower extremity.
Fig. 7 represents
the sinuous cells and starlike hairs of the leaf of the
Deutzia scabra, a very beautiful and favourite micro-
scopic object. These hairs are covered with a siliceous
coating, and when viewed by reflected light shine with
great brilliancy. Hairs may consist of single cells, or of
numerous ones arranged one above the other, or they
may be branched, or toothed, or plumose ; indeed
their forms are almost unlimited. In some hairs you
may see a single cell which contains an elastic coiled-
up spiral fibre. Hairs may be, as we all know by ex-
perience, either harmless to touch, or hurtful. The hair
of the common nettle contains at the base a poison-
ous fluid, which is conveyed into the wound through a

Fig. 7. — Starlike hairs of Deutzia scabra.

USE OF THE MICROSCOPE IN BOTANY. 2*J

duct ending at its finely-pointed extremity. We are
here reminded of the analogous case of a viper's
tooth in the animal kingdom. The phenomenon of
cyclosis, of which I have already spoken, takes place
probably in all kinds of hairs. Mr. Wenham says,
" The difficulty is to find exceptions, for hairs taken
alike from the loftiest elm of the forest, to the Humblest
weed that we trample beneath our feet, plainly exhibit
this circulation." To witness it, however, very high
powers of the microscope and great care are neces-
sary. In your examination of hairs, remember to tear
off a part of the cuticle from which they grow. If you
take hold of the hair itself, it will be almost sure to
break ; place the piece in a drop of water, with a thin
glass covering, and the forms of the various kinds will
reveal themselves.

CHAPTER III.

USE OF THE MICROSCOPE IN BOTANY — (continued}.

You will, no doubt, be much interested in examining
the structure of the hard portions of plants, such as
the stems, roots, seeds, &c. In many cases you will
find a sharp knife or razor sufficient for making sec-
tions of the parts you wish to study ; such substances
as the stony fruits of various trees require a more
expensive apparatus in order to prepare them for
investigation. I shall therefore take no notice of
these hard substances at present. You must take care
to prepare the stems or roots before you make your
sections ; if the wood be green, you must soak it for
some days in strong spirit, in order to get rid of any
resinous matter it may contain. After this, let the

28 THE MICROSCOPE.

specimen be macerated in water for a few days ; this
will remove the gum. If the portion of wood you
wish to study be dry, you must moisten it in water for
some time to soften it, then treat it as you would
green wood. It may be necessary in some cases to
use boiling water to render the stems sufficiently soft
for making sections. Wet the surface of the wood,
and cut off as thin a transverse section as possible.
Instruments called " section instruments " are sold for
this purpose, and very handy and useful some of them
are ; you can add one to your microscopic apparatus
after you have had more experience ; but you will
find that, with care and perseverance, you will succeed
in making very thin sections of stems, which will show
their different parts, such as the pith, medullary rays,
bundles of wood and bark, quite satisfactorily. In
the examination of the reproductive organs of plants,
you will find exhaustless matter for study and contem-
plation. Every one is familiar with the dusty particles
contained within the stamens of different plants, called
pollen (Fig. 8). Various and very
beautiful are these pollen forms, and
easy enough to examine, so far as
the external appearance goes. Per-
haps their most common form is
spherical or elliptical ; but many
beautiful geometrical forms are met
L with, such as cubic, tetrahedral, poly-
gonal, &c. In structure, the pollen grain generally
consists of an internal cell membrane, with one
or more outer layers of firmer texture. In some
instances, as in the Zostera marina, there is
only an inner membrane. The outer covering may
be smooth, or rough with numerous spiny pro-
jections, or reticulated, or divided into several seg-
ments or bands, or beset with numerous pores

USE OF THE MICROSCOPE JN BOTANY.

29

regularly or irregularly scattered. Pollen grains are
developed in the stamens (Figs. 10 and n), which are
the pollen-cases ; when they have arrived at maturity,
that stage at which they are fitted for the purpose of
fertilisation, the pollen-cases burst, and clouds of
pollen are shot forth like dust. Have you not often
dusted your nose with the yellow pollen of the garden
Eschscholtzia ? You have also, I dare say, been often

Fig. 9 -—Pollen mass of
Orchis Maculata.

Fig. ii. — Fou reel led
Fig. 10.' — Stamens of Anther of Persian
Iris. Laurel.

struck with the astonishing quantity of pollen some-
times found on a single stamen. A very little is
absolutely required for the fertilisation of the pistil :
why, therefore, this extraordinary abundance ? A great
deal of pollen, as you may suppose, runs to waste.
Such is the structure and position of the pistils of many
plants, that contact of the pollen-grains with the
ovule is often impossible except for the agency of the
winds, or of various birds and insects. The internal
cell contains a fluid (fovilld) which is supposed to

30 THE MICROSCOPE.

be the fructifying substance. The development of
the pollen-grain after it has touched the soft viscid
tissue of the pistil is very remarkable ; one or more

little processes bud
out of the grain (Fig.
13); in time this tube
or,'»process becomes
much elongated (Fig.
14); it insinuates itself
between the cells of
the stigma, until, con-
tinually elongating it-
self, it arrives at the
ovule at the bottom
of the ovaries which
are thus fertilised by it.
The illustrations here
given will show these
changes in the pollen-
grain which we have
been considering. " In
tracing the origin and
early history of the
ovule, very thin sec-
tions should be made
through the flower-
bud, both vertically
and transversely ; but
when the ovule is large and distinct enough to
be separately examined, it should be placed on the
thumb-nail of the left hand, and very thin sec-
tions made with a sharp razor ; the ovule should
not be allowed to dry up, and the section should
be removed from the blade of the razor by a wetted
camel-hair pencil. The tracing downwards the
pollen tubes through the tissue of the style may be

Fig. 14.

Fig. 13.

USE OF THE MICROSCOPE IN BOTANY. 31

accomplished by sections (which, however, will seldom
follow one tube continuously for any great part of its
length), or, in some instances, by careful dissection
with needles. Plants of the orchis tribe are the most
favourable subjects for this kind of investigation,
which is best carried on by artificially applying the
pollen to the stigma of several flowers, and then
examining one or more of the styles daily. i If the
style of flower of an Epipactis (says Schacht), to which
the pollen has been applied about eight days pre-
viously, be examined in the manner above mentioned,
the observer will be surprised at the extraordinary
number of pollen-tubes, and he will easily be able to
trace them in large strings, even as far as the ovules.
Viola tricolor (heart's-ease) and Ribes nigrum and
rubrum (black and red currant) are also good plants
for the purpose ; in the case of the former plant,
withered flowers may be taken, and branched pollen-
tubes will not unfrequently be met with/ The en-
trance of the pollen-tube into the micropyle* may
be most easily observed in orchidious plants and in
Euphrasia; it being only necessary to tear open
with a needle the ovary of a flower which is just
withering, and to detach from the placenta the ovules,
almost every one of which will be found to have a
pollen-tube sticking in its micropyle. These ovules,
however, are too small to allow of sections being
made, whereby the origin of the embryo may be dis-
cerned ; and for this purpose, (Enothera (evening
primrose) has been had recourse to by Hortmeister,
whilst Schacht recommends Lathr&a squamaria,
Pedicularis palustris, and particularly fedicularis

* From juxpoc, " small," and <7rw\n, "a gate," the minute perfora-
tion through the skin of a seed.
t Dr. Carpenter on the Microscope, p. 430.

32 THE MICROSCOPE.

You will find much to attract your attention and
excite your admiration in some of the lowest forms of
vegetation. The lichens, mosses, sea-weeds, fungi,
will all demand your notice, and none will fail to
repay you for the pains of a careful investigation.
Some of the fresh-water algae are extremely beautiful
and readily procurable, whilst, should you pay a visit

Fig. 15. — Receptacle of Fucus, containing Sporangia "germ cells."

to the sea-side, the "flowers of the sea" when gathered,
in some form or other, on every shore, will supply
a wide field for investigation. The common Fucus
vesiculosiis, whose ovoid capsules you explode at
almost every tread of the foot ; or the nearly equally
common F. platycarpus will amply repay you for
careful research. You will notice the receptacles at
the extremity of the fronds ; in the group of Fuci there
is no doubt about a true sexual mode of fructification

USE OF THE MICROSCOPE IN BOTANY. 33

(Fig. 15). The fungi, again, will demand your atten-
tion ; the minute reproductive bodies thrown off from
the gills of the Agaric group in countless millions,
known by the name of "spores," will interest you
much. Gather a common mushroom or other fungus,
cut off the stem near the gills, place it with the gills
downwards on a sheet of paper, black or white ; leave
it in this position for several hours ; on taking it up
you will notice the gills have deposited a quantity of
dust-like stuff upon the surface of the paper. The
colour varies according to the families to which
the fungi respectively belong; in the mushroom the
" spores " are pink, in some fungi they are rust-
coloured, in others white, in others black. Just
notice how beautifully the deposited spores represent
the form of the gills, then scrape a portion off the
paper, and submit it to microscopic examination.
Bear in mind this distinctive difference between a
"seed" and a "spore" — a seed contains an embryo,
a spore has none.

The little brown patches on the under side of some
of the ferns will attract your attention ; these are the
spore-cases of different forms, and variously disposed
according to the genus of plant on which they occur.
The spore-case, in some genus of ferns, is surrounded
by a curious elastic band, which, when the spores con-
tained within are ripe, suddenly jerks itself straight,
tears open the case, and disperses the minute spores
in all directions. You can witness the germination of
fern-spores by placing some on a damp surface, and
exposing them to light and heat. At first each one
puts forth a tubular prolongation ; the cells of the
spore multiplying by subdivision both transversely
and longitudinally, give rise to a flattened leaf-like
expansion, which from its under surface developes
both root-fibres and reproductive organs. Every one

c

34 THE MICROSCOPE.

is acquainted with those curious-looking plants called
horsetails (Equisetacea) ; you will find them interesting
microscopic studies. Take hold of one ; you notice
how rough it is ; this roughness is caused by a quantity
of silex which permeates the whole of the structure of
the horsetail. To such an extent does this in some
cases take place, that " even when its organic portion
has been destroyed by prolonged maceration in dilute
nitric acid, a consistent skeleton still remains/' These
horsetails are reproduced from spores on a spike at
the end of some of the branches. To each spore are
attached two pairs of elastic filaments; at first they
are coiled up round the body of the spore ; at the
liberation of the spore they extend themselves. " If a
number of the spores be spread on a slip of glass
under the field of view, and whilst the observer
watches them a bystander breathes gently upon the
glass, all the filaments will be instantaneously put in
motion, thus presenting an extremely curious spectacle,
and will almost as suddenly return to their previous
condition when the effect of the moisture has passed
off."* I have frequently witnessed this curious spec-
tacle, and you can easily do so yourself by following
Dr. Carpenter's directions, which I have just quoted.
The Equisetacecz develop themselves from these spores
after the manner of ferns ; on this account the name
" fern allies " has been applied to their family.

You will find endless variety of form and markings
in the seeds of plants. Seeds as microscopic objects
under a low power and by reflected light, or viewed
under the binocular, are often extremely beautiful.
Take the seed of the poppy ; notice the network
markings upon its surface ; or the seed of the carrot
with its long starfish-like radiating processes. Make

* Carpenter, p. 383.

US£ OF THE MICROSCOPE IN BOTANY. 35

a transverse section of any seed, you will find it has
two coats, an outer and inner membrane called re-
spectively testa and tegmen; you will see the embryo
either surrounded by albumen or immediately invested
by the coats. The following easily procured plants
will furnish you with samples of seed-forms : poppy,
stitchwort, mignonette, snapdragon, saxifrage, sweet-
william, foxglove. You can add to this list almost
indefinitely.

Every stream, ditch, and pond will supply. you;
with many forms of algae, known as Diatomacecz and
Desmidiacetz* Once these organisms were supposed to
belong to the animal kingdom, on account of some
ot them exhibiting motion ; there is no doubt, how-
ever, that both these families are true vegetables'.
They are found in masses of jelly-like substance
attached to the stems or leaves of various aquatic or
marine plants, or they envelop any submerged plant
with loose brownish flocculent matter. The Diatomacece,
or brittleworts, are invested with a covering of silex ;
this fact you can readily demonstrate for yourself by
boiling the minute plants in nitric acid, having pre-
viously washed them well, so as to free them from
extraneous matters. The organic vegetable matter
is destroyed ; the siliceous portion remains. The
Desmidiacece, another family of confervoid algae, are
destitute of any siliceous covering ; they are generally
of a green colour, and are found, like the Diatomacece,
investing submerged plants or other bodies. These
microscopic algae, under a power of 300 to 400
diameters, are very striking objects; they come "in
such questionable shapes " that you cannot help but
" speak to them." Now circular, now filamentary,
beautifully jointed, now like small boats in outline,
now crescent-shaped — in fact, every variety of form
exhibiting — these algae, I have no doubt, will occupy

C 2

THE MICROSCOPE.

much of your time. And here I should wish to
give you some advice which you will find useful as
a beginner. It is well at first to make yourself ac-
quainted with various forms of plant-life — to run
cursorily at first, but mind, only at first, over various
objects. You will thus gain a sort of general notion
of the interesting field of operations before you.
Real special work — and I hope you are going in for
real work — must begin after you have made a general
survey of the land in which you wish to make con-
quests. It is not well
for a beginner to embark
all at once, without some
general knowledge of
the field of labour, into
special work.

All these plants, you
will see, evolve oxygen
when exposed to the
light of the sun ; those
bubbles which bespangle
that brown-coated stem
from the confervae are
bubbles of oxygen, which
at once disclose, even

in the absence of further proof, their vegetable nature.
Many other forms of undoubted vegetable nature
which have been, at one time or another, claimed by
the zoologists as belonging to the animal kingdom,
might be enumerated. Prominently we may notice
that curious protophyte not uncommon in stagnant
water, called Volvox globator. Look out for specimens
in the spring and summer months ; they are easily
seen where they abound, about the size of a small
pin's head, and of a greenish colour : they will attract
your eye when they roll along in the glass bottle in

Volvox Globator.

USE OF THE MICROSCOPE IN ZOOLOGY. 37

which you have collected some specimens. I have
generally found Volvox globator in stagnant ponds
containing a profusion of aquatic vegetation. The
ordinary size is about -^ of an inch in diameter.
" When examined with a sufficient magnifying power,
the volvox is seen to consist of a hollow sphere,
composed of a very pellucid material, which is
studded at regular intervals with minute green spots,
and which is often, but not constantly, traversed by
green threads connecting these spots together. From
each of the spots proceed two long cilia; so that
the entire surface is beset with these vibratile fila-
ments, to whose combined action its movements are
due. Within the external sphere may generally be
seen from two to twenty other globules of a darker
colour and of varying sizes ; the smaller of these are
attached to the inner surface of the investing sphere,
and project into its cavity; but the larger lie freely
within the cavity, and may often be observed to revolve
by the agency of their own ciliary filaments. After
a time the original sphere bursts, and the contained
spherules swim forth, and speedily develop themselves
into the likeness of that within which they have been
evolved." When you see, as you will do, various
organisms swimming freely about in a drop of water,
you will be inclined to put them down as belonging to
the animal kingdom. Suspend your judgment; it is
quite probable what you see are motile cells of certain
vegetable organisms. What is the difference between
a plant and an animal ?

* Carpenter, " Microscope," p. 251.

CHAPTER IV.

USE OF THE MICROSCOPE IN ZOOLOGY.

IN the last chapter I asked the question, "What is
the difference between a plant and an animal?" — a
question more easily asked than satisfactorily answered,
for when we examine very low organisms, we seem to
touch the confines of the two kingdoms ; but these
confines are very difficult to determine — indeed, some
scientific men have denied any absolute distinction
between the two kingdoms. They assert that, not-
withstanding the manifold differences in form and
structure, there is a " physical basis of life underlying
all the diversities of vital existence;" that "a three-
fold unity — namely, a unity of power or faculty, a
unity of form, and a unity of substantial composition —
does pervade the whole living world." According to
that eminent biologist, Professor Huxley, the formal
basis of all life is protoplasm, simple or nucleated ;
and in the lowest plants, as in the lowest animals,
a single mass of such protoplasm may constitute the
whole plant, or the protoplasm may exist without
a nucleus. How, then, it is asked, is one mass of
non-nucleated protoplasm to be distinguished from
another? Why call one plant and the other ani-
mal? The only reply is that, so far as form is
concerned, plants and animals are not separable, and
that in many cases it is a mere matter of con-
vention whether we call a given organism an animal
or a plant. There is a living body called &thalium
septicum, which appears upon decaying vegetable sub-
stances, and in one of its forms is common upon
the surfaces of tan-pits. In this condition, it is to

USE OF THE MICROSCOPE IN ZOOLOGY. 39

all intents and purposes a fungus, and formerly was
always regarded as such ; but the remarkable in-
vestigations of De Bary* have shown that in another
condition the ^Ethalium is an actively locomotive
creature, and takes in solid matters, upon which
apparently it feeds, thus exhibiting the most charac-
teristic feature of animality. Is this a plant, or is it
an animal ? Is it both ; is it neither ? Some decide
in favour of the last supposition, and establish an
intermediate kingdom, a sort of biological No Man's
Land, for all these questionable forms. But as it is
admittedly impossible to draw any distinct ' boundary
line between this No Man's Land and the vegetable
world on the one hand, or the animal on the other, it
appears to be that this proceeding merely doubles the
difficulty, which before was single, t

Notwithstanding, however, the great difficulty, if
not impossibility, of drawing a distinction between
some of the lowest forms of the animal and vegetable
kingdoms, as a general rule the boundaries are suffi-
ciently distinct. I have called your attention to the
remarks of Professor Huxley on this subject, in order
that you may see what great problems the microscope
helps to solve. I will now direct you to a considera-
tion of some of the minute forms of undoubted animal
life which every pond or ditch contains in endless
variety and profusion. Of so-called monads — extremely
minute organisms found in water containing decom-
posed vegetable or animal matter, several supposed
species of which have been described — I need say but
little. There can be no doubt, notwithstanding the
opinion of Ehrenberg, that the Monadina family con-

* "Die Mycetozoen." Leipzig, 1864; also an abstract in Hoff-
meister's "New System of Botany."

t "Oft the Physical Basis of Life." — Fortnightly Review, Feb.,
1869.

40 THE MICROSCOPE.

sists of a heterogeneous group, some forms of which
may be the zoospores of algse, others the germs of
animalcules. The Monadina, which quite recently
have been regarded as the most minute living crea-
tures discovered, comprising several distinct genera —
such as Monas, Euglena, Uvella, Syncrypta, Chlamydo-
monas, Bodo, and many more — can no longer stand as
a family representing different mature animal forms.

For obtaining microscopic objects from the pond,
stream, or ditch, all you want is a wide-mouthed bottle
or two, a bit of wire, a walking-stick, a lens, and a
canvas or strong muslin net. A cutting hook to screw
into the end of your walking-stick will be useful in
nipping off the stems of aquatic plants, which always
harbour many forms of animal life. Several kinds of
animalcules, wholly invisible to the unaided eye as
single objects, are discernible as groups ; among which
I may mention to you the green masses of Ophrydium
versatile, and various Vorticellce, which may be fre-
quently seen encircling submerged stems or other
bodies with a dirty-white flocculent mass. Ophrydium
versatile lives in societies of many thousands together,
in balls of a whitish jelly-like substance. The colour
of the animalcules is green, and this gives the colour
to the masses of jelly in which they live. The size of
these balls varies from that of a pea to that of a man's
fist. In form each individual is very like a Stentor,
especially when it is free — for these little creatures
can leave the jelly-like ball, and swim treely in the
surrounding fluid — but as long as an Ophrydium is an
inmate of the jelly ball, it possesses, at the hinder
end, a very long thread-like tail, much longer than
itself; this tail seems to anchor the animalcule securely
in the gelatinous substance. You may meet with
these balls in clear water in the spring and early sum-
mer months.

USE OF THE MICROSCOPE IN ZOOLOGY.

1 he little creatures called Stentors are very interest-
ing to study. Each one looks like a miniature
green trumpet, and is visible to the unassisted eye.
Look carefully at the engraving : you notice that
the goblet-shaped mouth is sur-
rounded with a circle of hairs ;• these
are called cilia, from the Latin word
meaning eyelashes, a designation
appropriate enough. There are
many curious forms of these ciliated
protozoa, and it will be a source of
much pleasure to you to make their
acquaintance from time to time.
The whole body of the stew tor is, as
you observe, covered with cilia —
organs which play a very useful and
prominent part in these creatures'
lives. They serve both for the pur-
poses of progression — for by these
numerous hairs the animalcules row
themselves about with wonderful
rapidity — and also, when arranged
in a circlet round the mouth, for
obtaining food. The constant lash-
ing of these cilia produces currents of water, which
convey to the animalcule particles of food, whether
of an animal or vegetable nature. These Stentors are
of various colours — it is supposed there are many
species of the genus ; five or six have been described
— either white, black, blue, or green; and like their
relations, the Ophrydia, are capable of assuming
various forms. They increase, like numerous othei'
forms of low animal life, by self-division. Such split-
ting may take place either longitudinally or obliquely,
and each part may form a perfect animal. You will
often witness animalcules in the act of separating into

Fig. 16.— Stentor.

42 THE MICROSCOPE.

two portions ; this method of reproduction is ana-
logous to that of the budding of plants. But even in
animals so small as, and even much smaller than, a
Stentor, a true sexual reproduction takes place. It is
to the researches ot Balbiani that we are indebted
for our knowledge of this most interesting fact. It
seems pretty certain that, both in the case ot animals
and plants, a contact of sperm-cell with germ-cell is
at times absolutely necessary for the continuation of
the species. You will be able to make yourself satis-
fied of the existence of this phenomenon amongst the
infusoria, after some experience in the use of the
microscope; so at present I will not make further
remarks on the subject. Great patience is necessary
if you would gain an accurate idea of the structure or
functions of any minute organ of these little crea-
tures. In no case is the old Latin proverb, "Nil
sine labore," more true than in microscopic work ;
and the same may be said of the converse, " Labor
omnia vincit."

What strange form of animal life am I gazing at
now ? A group of some dozen or more of creatures,
each growing from a long, spirally-twisting stalk ; some
individuals, you see, are in the act of splitting, others
have left the stalks; some are just beginning to
uncoil, others are partly, others wholly uncoiled. The
mouths, you observe, are surrounded with cilia. I
will rub a little paint, say carmine or indigo, on this
glass slide, and dip my camel-hair brush into it ; now
I let a little drop of this find its way between the
glass cover and the slide on which the specimens I
am examining lie. Now you see the action of these
cilia. How the particles of colour are whirled about
in all directions ! How wonderfully rapid is the move-
ment of these spiral stems, or foot-stalks ! The name
of this little creature is Vorticella^ or the Bell Flower

USE OF THE MICROSCOPE IN ZOOLOGY.

43

Animalculse (Fig. 17). Other interesting forms of the
Vorticellina family you are sure to meet with, such as
Epistylis and Carchesium. In individuals of the former
genus, the
flowers droop
from a stem
in a tree-like
form, the foot-
stalks having
no retractile
power; in Car-
chesium the
bells orflowers
spring from a
single non-re-
tractile trunk,
but the stems,
which are very
numerous, are
all retractile.
On the stems
and leaves of various aquatic plants you will see
other interesting little creatures of the same family —
each inhabiting a tube. A great number of species

have been described ;
but you will recognise
the general form when I
tell you that the animal-
cule is like a Stentor. It
is very curious to witness
this animal protrude itself
out of its case. Within
its case, which is often
very transparent, and
which perhaps would es-
Fig. ig.-carchesium. cape your detection were

Fig. 17.— Vorticella.

44

THE MICROSCOPE.

it not for the small particles of dirt which have
attached themselves to it, the animal is seen as a
round mass. By-and-by it slowly extends itself till it
reaches the open mouth of the tube ; then the an-
terior orifice expands, the circlet of cilia is put in
active motion, currents of food-producing water are
brought within the action of the cilia, and, all of a
sudden — quick as lightning — the little creature, by

contraction of its
muscular tissues,
subsides into the
form of a ball, as
before. From
their habit of living
in a sheath these
creatures are
called Vaginicoltz.
The wheel-ani-
malcules (Rotiferd)
will afford you un-
limited amusement
and instruction.
You will recognise
their form from
the accompanying
figure. We advance a step most decidedly here. The
animals that have hitherto come before our notice
are of low organisation compared with the Rotifer a.
How shall we describe the structure of a Stentor
or an Ophrydium ? Imagine an animated mass hol-
lowed out into one large general cavity. There
is a mouth, with its circlet or circlets of cilia,
and a stomach — some animal organisms, such as
amseba and sponge, have not got so much even as
this — a contractile vesicle, apparently the rudiments
of a circulating system, and two nuclei, which represent

Fig. 19. — Wheel-animal culae.

USE OF THE MICROSCOPE IN ZOOLOGY. 45

the reproductive apparatus ; but in the wheel-animal-
cule, and other Rotifers, you will see a differentiation
of parts and a specialisation of organs. There is evi-
dently an integument or skin through which certain
viscera or internal organs can be discerned ; one of
the most conspicuous organs is what is sometimes
badly named the gizzard. This piece of organic
machinery, consisting of strong muscular substance, fur-
nished, according to the species, with various pointed
teeth, seems in these animals to be always going \ its
function is manifest even at a glance. You will notice
that various substances, drawn down in the vortex
caused by the action of the cilia, pass through this
manducatory organ, which, like a pair of miniature
mill-stones, grinds the food as it passes between them.
You will often notice both eggs and young ones
within the bodies of the wheel-animalcules, and very
curious it is to see under the microscope the move-
ments and contortions of a restless embryo rotifer.
The Rotifera possess, moreover, an intestinal canal,
a water-vascular system, and longitudinal muscles.
There is much difference of opinion as to their
proper place in the zoological scale. Some naturalists
think that these wheel-animalcules have their affinities
with worms, others with crabs.

You will be almost in ecstacies of delight at first
becoming acquainted with the Melicerta ringens, an
exquisite little creature, pretty common in pools and
ditches, where it may be found sometimes in extra-
ordinary profusion, attached to the stems and leaves
of various aquatic plants. The Melicerta is a worm-
like creature, about as thick as a horsehair, and the
twelfth part of an inch in length^ It is itself the
architect of a very pretty little tubular house in which
it dwells. You should try to make the acquaintance
of Melicerta, for in the whole aquatic world there is

46 THE MICROSCOPE.

scarcely a more interesting object for contemplation.
Search for these creatures in mill-pools and ponds
through which a current of water gently flows. If a
portion of water-weed be brought home and placed in
a glass vessel, and the leaves of the plants be care-
fully examined with a lens — the long thread-like leaves
of the water crowfoot (Ranunculus aquatilis) are a very
favourite habitat — you will probably detect delicate
projecting objects of a reddish-brown colour, light or
dark, however, according to the nature of the bottom
of the pool. These are the tubular cases of Meliccria.
If one of these, still attached to the bit of weed, be
placed on a slip of glass, and viewed under the micro-
scope with a power of about 50 diameters, you will
notice that this tube is made of several series of round
clay or mud pellets. By-and-by, if you will be careful
not to shake the table on which the specimen is
placed (for Mdicerta is a coy and timid creature), you
will see the occupant slowly unfold the anterior portion
of its body from the orifice of the tube. At first, as
Mr. Gosse has well described it, "a complicated mass
of transparent flesh appears involved in many folds,
displaying at one side a pair of hooked spines, and at
the other two slender truncate processes projecting
horizontally. As it exposes itselt more and more,
suddenly two large rounded discs are expanded,
around which at the same time a wreath of cilia is
seen performing its surprising motions. Often the
animal contents itself with this degree of exposure,
but sometimes it protrudes further, and displays two
other smaller leaflets, opposite to the former, but in
the same place, margined with cilia in like manner.
The appearance is now not unlike that of a flower of
four unequal petals ; from which resemblance Linnaeus,
who compared it to a ringent labiate corolla, gave it
the trivial name of ringens, by which it is still known.'*

USE OF THE MICROSCOPE IN ZOOLOGY. 47

By continuing to gaze on this marvel of creative skill,
you will notice that it every now and then bends its
corolla-shaped head down upon the tube, holding it
there a second or two, and then raising it up again.
What is the meaning of this ? Melicerta is adding a
brick to its house ; sometimes you will see the bricks
roll off after deposition, in consequence of the material
not being sufficiently tenacious. The bricks are
made of the same substance so generally used by
human architects — namely, of clay, the only difference
being that the bricks of the rotifer are round and soft.
Under a power of about 200 diameters you will
observe a singular cavity below the large discs of the
head ; this cavity gradually becomes filled with
particles of clay ; a number of cilia line the cavity,
and by their action cause the particles of clay to
rotate rapidly and to be consolidated. When the
brick is formed the animal bends down its head and
fixes it to the tube, and then begins to form another
pellet. The particles of clay, or other adhesive
material, are drawn into the cavity where the bricks
are formed, by the ciliary action of the discs, a small
channel conducting them from the upper portion of
the disc to the cavity in question. If portions of
indigo or carmine be mixed with the water in which
the Melicerta lies, the animal will make use of them,
and add rings of red or blue to its dwelling-place. It
is impossible, I think, to imagine a more interesting
instance of animal architecture than that exhibited by
this little creature.

The Rotifera, from their great transparency, are
excellent objects for study ; many, forms, moreover
are readily obtained — the scum attached to aquatic
plants, the dirt in your pipes on the roof of your
house, the soil on the roots of the moss of your slated
roof, the mud at the bottom of ponds and ditches, will

48 THE MICROSCOPE.

afford many specimens for examination. There is
every variety of form : some are naked ; others are
loricated, or have a consolidated integument encircling
their bodies; others construct houses in which they
reside. Two beautiful forms, the Floscularia and Ste-
phanoceros, will demand a short notice in the next
chapter.

CHAPTER V.

USE OF THE MICROSCOPE IN ZOOLOGY (continued).

THE Stephanoceros and Floscularia are both very
beautiful and delicate little creatures ; they should be
examined, to get a general idea of their form and
characters, with a power of about 60 diameters. The
former animal has an oblong body on a long tapering
stalk ; a circlet of fine elegant tentacles, with two rows
of cilia on the sides, surrounds its upper portion ; like
the Melicerta^ this little creature dwells in a tube, but
not mechanically constructed, like that of the first-
named animal. You will not easily satisfy yourself
of the existence of this tube, so extremely transparent
as it is ; but by turning the mirror at different angles,
you will notice a jelly-like case, which appears to be a
secretion from the animal's body. Groups attached
to weeds are visible to the naked eye; they prefer
clear water, and may be kept alive for weeks in a
vessel of water. On the slightest alarm, the Stepha-
noceros retreats within her cylindrical tube. Floscu-
laria is another exquisite microscopic object, and
common enough on the stems or leaves of water-
plants. This creature, too, dwells in a transparent case ;
in form, it is like Stephanoceros, except that the head-
portion is divided into six lobes or projections, each

USE OF THE MICROSCOPE IN ZOOLOGY. 49

one having an immense quantity of extremely fine
bristles. As the animal protrudes itselt out of its case,
these hairs appear in a dense mass, but soon the lobes
separate, and the tufts of bristles on each spread them-
selves out in a graceful fan-like torm. What is the
use of these long bristles ? I am unable to tell you.
Although the animal is destitute of the ciliary wheel-
like wings that characterise the Rotifera generally, its
whole organisation, and the mechanism and functions
of the grinding jaws or gizzard, clearly indicate its
relationship with that class ot animals. We must not
linger more on these and similar exquisite little forms
of animal life ; let me direct your attention to a very
strange-looking creature called the Hydra, of which
genus there are three well-marked British species —
namely H. viridis, H. vulgaris, and H.fusca. The first
is of a beautiful grass-green colour, the second and third
of a pale brown, sometimes nearly white. The arms or
tentacles of the last-named species are very long. These
animals are found only in fresh water, and generally
such as flows very slowly or is quite still. As you will
find the study of these creatures full of the deepest
interest, I will give you a description somewhat fully.

The best way to obtain specimens is to take a
handful of weeds from any clear pond or ditch, and
place it in a glass vessel of water. After waiting
half an hour the hydrae will probably be seen in
various attitudes, some hanging loosely down, others
gracefully curving themselves upward and throwing
out tentacles many times longer than their bodies;
others shooting up their arms above their heads ;
others contracting themselves into mere jelly-like dabs ;
others attaching themselves by both extremities to the
side of the glass ; others floating on the surface of the
water, their-tail ends preserving them from sinking.
Their colours, too, may be nearly as various as their

D

THE MICROSCOPE.

attitudes — white, red, light flesh, or beautiful grass-
green. The body of the hydra is of a gelatinous
nature, altering in shape as it changes its position ;
when contracted, in some species a mere tubercle with
short radiating papillae ; when extended, becoming a

narrow cylinder.
One end expands
and forms an ad-
herent disc j the
other has a mouth
surrounded by nu-
merous exceedingly
contractile arms or
tentacles, varying
in number accord-
ing to the age and
species of the in-
dividual. The
hydra's body is
composed of two
membranes, techni-
cally termed ecto-
derm and endoderm,
the former being
the external cover-
ing, the latter the
internal lining of the cavity. The tentacles are tubes,
which are, in fact, prolongations of these two mem-
branes. They are the arms by which the animal seizes
its prey, and they are placed a little, below the mouth,
which, when closed, protrudes like a snout above them.
Both membranes have irregularly rounded nodules on
their surface. These nodules, especially in the tenta-
cles, contain capsular bodies (thread-cells), in which
may be seen (the hydra being crushed between bits of
glass, under a high microscopic power) curious organs.

Hydra attached to a Weed.

USE OF THE MICROSCOPE IN ZOOLOGY. 51

consisting of spines and filaments, supposed by some
to have the power of stinging. There are traces of
muscular fibres in the tentacles, but whether sufficient
to account for their extraordinary extensibility is
doubtful. Some have supposed their elongation to be
caused by the water, which, finding its way into the
hydra's body through the mouth, may pass through
extremely narrow channels into the tentacles. The
tentacles of Hydra fusca are the most wonderfully
extensible of all; growing gradually finer than the
lightest gossamer, they become invisible except to
the eye of the microscopist.

The hydrae are very voracious, and readily kept in
confinement for some time. They feed on small
Entomostraca ', and on minute larvae of gnats and naid
worms. Their stomach is a simple cavity. Some
authors speak of a short narrow duct leading from the
stomach to the centre ot the disc, whence they say
through a tiny aperture excrementitious particles may
be seen to pass. Of this intestinal canal I have never
discovered any sign in the species I have examined.
Food is quickly assimilated by the hydra, and the
indigestible portion expelled through the mouth, as
in the Actinice. The movements of the hydra are
very slow, but performed in the same manner as those
of the leech, their position being also varied by a
gliding motion of the disc. Sometimes this disc,
protruded above the water, acts as a float, and the
animal is borne along on the current. Hydrae may be
found in spring, summer, or autumn, and in the latter
season they give birth to eggs and die. I have found
H. viridis in very mild winters. Their mode of in-
crease is twofold — gemmation and the ordinary mode
of reproduction. The first takes place throughout
the summer, the latter only at the end of autumn.
When increasing by gemmation, a small swelling first

D 2

52 THE MICROSCOPE.

appears on the hydra's body; this grows larger, and
divides at its apex into several minute papillae, which
afterwards become the tentacles. When reproducing
by ova, the observer will notice certain peculiar eleva-
tions on the body of the hydra, some, in the middle
of the body, round; others, at the bases of the
tentacles, of a conical shape; perhaps one or two ot
each kind. The round elevations contain the ova;
the conical, the spermatozoan bodies. The ovum,
when ripe, pushed through the body-wall, and impreg-
nated, becomes attached to some water-weed, and
awaits the warm spring to be developed into the young
hydra. But I have never succeeded in meeting with
these detached ova, and they appear to have been
only noticed by few. Trembley and Baker record
many and various experiments practised by them on
the hydra; and the former gives us a number of
admirably executed figures. The result of these ex-
periments may be summed up in the language of
Dr. G. Johnston: — "If the body is halved in any
direction, each half in a short time grows up a perfect
hydra ; if it is cut into four or eight, or even minced
into forty pieces, each continues alive and developes
a new animal, which is itself capable of being mul-
tiplied in the same extraordinary manner. If the
section is made lengthways, so as to divide the body
into two or more slips, connected merely by the tail,
they are speedily re-soldered, like some heroes of fairy-
tale, into one perfect whole ; or if the pieces are kept
asunder, each will become a polype, and thus we may
have two or several polypes with only one tail between
them ; but if the sections be made in the contrary
direction — from the tail towards the tentacula — you
produce a monster with two or more bodies and one
head. If the tentacula — the organs by which they
take their prey, and on which* their existence might

USE OF THE MICROSCOPE IN ZOOLOGY, 53

seem to depend — are cut away, they are reproduced,
and the lopped-off parts remain not long without a
new body. If only two or three tentacula are em-
braced in the section, the result is the same, and a
single tentaculum will serve for the evolution of a
complete creature. When a piece is cut out of the
body, the wound speedily heals, and as if excited by
the stimulus of the knife, young polypes sprout from
the wound more abundantly, and in preference to
unscarred parts ; when a polype is introduced by the
tail into another's body, the two unite and form one
individual ; and when a head is lopped off, it may
safely be engrafted on the body of any other which
may chance to want one. You may slit the animal
up, and lay it out flat like a membrane with impunity ;
nay, it may be turned inside out, so that the stomachal
surface shall become the epidermis, and yet continue
to live and enjoy itself, and the animal suffers very
little by these apparently cruel operations,

'Scarce seems to feel, or know
His wound,'

for, before the lapse of many minutes, the upper half
of a cross section will expand its tentacula and catch
prey as usual \ and the two portions of a longitudinal
division will, after an hour or two, take food and
retain it. A polype cut transversely in three parts
requires four or five days in summer, and longer in
cold weather, for the middle piece to produce a head
and tail, and the tail part to get a body and head,
which they both do in pretty much the same time."

You will often notice some very interesting para-
sites upon the various species of Hydra. One very
curious little fellow delights to run up and down .the
hydra's tentacles, like a miniature railway-truck. In
form the creature resembles a dice-box, only it is as

54 THE MICROSCOPE.

broad as it is long ; a wreath of cilia surrounds both
the top and the bottom edges. Now it leaves the
hydra, soon, however, to return to it again. The
name of this little parasite is Trichodina pediculiis. I
am of opinion that these hydra-lice are indicative of
a not very healthy condition of their hosts ; but
whether they are annoying or not I cannot say.
The curiously-formed stinging organs of the hydra
seem to be of no service in warding off these minia-
ture Trichodina.

There is one curious creature which I must intro-
duce to your notice, and which you may not unfre-
quently find in the surface mud of any pond. I shall
never forget my first acquaintance with this animal,
about twenty years ago. So struck was I with its
absurd and grotesque appearance, having at that time
but little acquaintance with microscopic forms, that I
could hardly believe the evidence of my senses, and
I called in a servant to look at the strange creature,
and to tell me that I was not dreaming. Well, what
was the creature ? It was a Tardigrade, a very " slow-
goer" indeed, but the strangest of beasts ; it was
something like a naked sloth, only it had four pairs
of legs instead of two. These legs — such things to call
legs — were each provided with four claws ; there was
no tail ; its mouth was changeable in form, now
blunted, now pointed with pouting lips. A curious
oval-shaped muscular body, with peculiar style-like
appendages was very conspicuous ; this was the ani-
mal's gizzard. The style-like processes, or horny rods,
are said to be protrusile ; but though I have fre-
quently examined tardigrades since I first made their
acquaintance, I do not think I ever saw these rods in
a protruded state.

These animals, like the rotifers, are capable of
bearing exposure to very great heat without being

USE OF THE MICROSCOPE IN ZOOLOGY. 55

any the worse for it; indeed, they were believed to
be capable of resuscitation. Spallanzani has a chapter
with the following heading : " Animals which can be
killed and resuscitated at pleasure." Of course such
an idea is absurd; the fact, however, remains that
certain creatures, rotifers, tardigrade s, anguillulae, can
be reduced by great heat to almost thorough dryness,
can be kept in this condition for a length of time, and
yet will revive on the application of moisture. Every
one who is acquainted with the history of these animals
is aware of the experiments made on them by M.
Pouchet, so I shall conclude this chapter with an
extract -from
"The Uni-
verse" of that
distinguished
French savant:
" It is true we

are, in OUr A Tardigrade.

day, obliged to

erase the charming romance of palingenesis, with
which our forefathers amused themselves. Still, we
must say that, although the Rotiferae cannot be resus-
citated when they are once dead, their tenacity of life
is one of the most extraordinary phenomena. Their
resistance to cold is something marvellous, and we do
not even know where it stops ; the lowest temperature
that we can obtain in our laboratories does not seem
to have any effect upon them. I have seen these
animals defy a cold which would kill a man a hundred
times over. Rotiferae placed in an apparatus where
the temperature was 40° below zero, Centig. (40°
Fahr.), issued from it full of vitality."*

" The natural history of the Rotiferae is a

* "The Universe,'.' p. 56.

^ 6 THE MICROSCOPE.

marvel from beginning to end. I have sometimes
removed them quickly from the freezing apparatus,
and thrown them into a stove heated to 80 u Centig.
(176° Fahr.); when they emerged from this they
were seen to recover their animation, and run about
full of life. In this twofold testt and formidable
transition from cold to heat, these Microzoa passed
rapidly through a change of 120° Centig. (216°
Fahr.) without being in the least inconvenienced by
it." After what I have said and quoted, I am sure
you will wish to make a few " slow-going" acquaint-
ances.

CHAPTER VI.

USE OF THE MICROSCOPE IN ZOOLOGY (continued}.

ONE of the most interesting spectacles afforded by
the microscope is that which is furnished by the cir-
culation of the blood. This may readily be seen in
the gills of the tadpole or newt, in the tail of the tad-
pole, the foot and tongue of the frog, in newly-hatched
fish, such as young trout, perch, sticklebacks, &c.
The tadpole in its early stages of existence is essen-
tially a fish, breathing the air contained in the water
by means of external gills alone. If you will examine
a very young tadpole, you will see these gills in the
form of a pair of fringes at the sides of the head ; at
the bases of these are also the rudiments of the in-
ternal gills. The external gills rapidly disappear at
the end of four or five days; but the internal gills,
which were mere rudiments at first, are undergoing
rapid development. " It is requisite," says Dr. Car-
penter, " that the tadpole subjected to observation

Circulation of Blood in a young Tadpole.

58 THE MICROSCOPE.

should not be so far advanced as to have lost its early
transparence of skin ; and it is further essential to the
tracing out the course of the abdominal vessels, that
the creature should be kept without food for some
days, so that the intestine may empty itself. This
starving process reduces the quantity of red corpuscles,
and thus renders the blood paler ; but this, although
it makes the smaller branches less obvious, brings the
circulation in the larger trunks into more distinct
view." The circulation of blood in a young tadpole
is a most astonishing spectacle. The plate will serve
to give you some slight notion of the internal organs ;
by-and-by, when you become more experienced, you
should read Mr. Whitney's remarks on that subject
in Vol. X. of the Transactions of the Microscopical
Society, 1862. If you desire to study the circulation
of blood in a frog's foot, you should select a young
specimen with a thin web. But how are you to keep
the frog quiet under inspection ? Microscope-makers
sell an especial apparatus for this purpose, called a frog-
plate ; but you can easily cut out a wooden imitation,
which will serve your purpose completely. Provide
yourself with a piece of thin wood or cork, about nine
inches long and three inches wide; towards the middle
of its length cut a hole about half an inch in diameter.
Wrap the whole of the frog, except one leg, in a piece
of wet calico, and fasten him, but not too tightly, on
the cork-plate ; spread out the exposed foot over the
aperture, and by means of a few small pins fasten the
foot to the cork. Then put the cork-plate upon the
stage of the microscope, and secure it by means of
tape. Moisten the frog's web with a spot of water,
and examine it under the microscope with a power of
about 100 diameters, and you will see a wonderful
sight. Torrents of blood flow with great rapidity,
crossing and re-crossing each other ; sometimes there

USE OF THE MICROSCOPE I XT ZOOLOGY. 59

is a momentary check, and the blood-corpuscles col-
lect together in one spot. Perhaps the frog is too
tightly fastened, or alarm may have interfered with
the heart's action. You will notice several dark
opaque bodies in the substance of the frog's feet ;
these are pigment cells.

The water larvae of various kinds of insects, small
Crustacea, such as Daphnia pulex, &c., will reward you
for a patient study of the circulatory system in these
creatures. Both in the larva, pupa, and imago stages
insects have not a heart, but a long dorsal vessel, which
is really made up of a series of contractile cavities,
one for each segment of the body, opening one into
another from behind forwards, the whole being divided
by valvular partitions. This is the typical form of the
circulatory system. It must be confessed, however,
that there is much difficulty in always making out
these valvular partitions. The larvae of any of the
EphtmcricUz are capital objects for examination. A
smaller specimen laid upon a glass slide, with a drop
of water and a thin glass cover over it, will serve well
to show you the circulation of blood in insects. You
will notice that the blood is almost colourless, that the
corpuscles are oat-shaped. " The current enters the
dorsal vessel at its posterior extremity, and is propelled
forwards by the contractions of the successive cham-
bers, being prevented from moving in the opposite
direction by the valves between the chambers, which
only open forwards. Arrived at the anterior extremity
of the dorsal vessel, the blood is distributed in three
principal channels ; a central one, namely, passing to
the head, and a lateral one to either side, descending
so as to approach the lower surface of the body. It
is from the two lateral currents that the secondary
streams diverge, which pass into the legs and wings,
and then return back to the main stream. It is from

6o

THE MICROSCOPE.

these also that in the larva of the Ephemera margin ata
the smaller currents diverge into the gill-like append-
ages with which the body is furnished."

The various organs of insects will supply you with
inexhaustible subjects for study and interest. A com-
mon fly from your window pane will furnish you with

Eye of Fly magnified.

matter for examination for some time ; and I would
recommend the common fly as a sample of insect
structure. Under a simple lens you will observe the
numerous facets of the eyes, the number and position
of the nervures on the wings ; you may then select its
various members for examination. Cut off the head,
and view it as an opaque object by reflected light;
you. will notice that each eye is made up of numerous

USE OF THE MICROSCOPE IN ZOOLOGY. 6 1

little hexagonal figures, forming so many eyes, or ocelli,
as they are termed. In the common fly the two eyes
contain about 4,000 of these hexagonal facets, or ocelli.
The eyes of insects differ according to the species,
both in position, number, form, and colour. The eyes
of the common white butterfly are composed of about
17,000 ocelli; in the dragon-fly there are upwards
of 20,000.

By making a very careful vertical section you will
discover that each ocellus is in shape like a pyramid ;
the upper part, or corneule, forming the base, the apex,
or lower part, which is drawn to an extremely fine
point, coming in contact with some delicate extremi-
ties of nerve-fibres which branch out from the optic
nerve. It has been shown that each corneule is a
double-convex lens, made up of the junction of two
plano-convex lenses possessing a different refractive
power, by which arrangement, probably, the aberra-
tions are diminished, as they are by the combination of
"humours" in the human eye. "That each 'corneule'
acts as a distinct lens may be shown by detaching the
entire assemblage by maceration, and then drying it
(flattened out) upon a slip of glass ; for, when this is
placed under the microscope, if the point of a knife,
scissors, or any similar object, be interposed between
the mirror and the stage, the image of this point will
be seen, by a proper adjustment of the focus of the
microscope, in every one of the lenses."*

The pyramids, which consist of a transparent sub-
stance, representing, it is supposed, the " vitreous hu-
mour," are separated from each other by a layer of
dark pigment, which at one point closes in, but leaves
very minute papillary apertures for the entrance of rays
from the corneule, which, passing down the pyramids,

* " The Microscope," p. 662.

6? THE MICROSCOPE.

impinge upon the nerve-fibres at the apex of the pyra-
mid. " Thus the rays which have passed through
the several 'corneules' are prevented from mixing
with each other, and no rays, save those which pass
in the axes of the pyramids, can reach the fibres of the
optic nerve. Hence it is evident that, as no two
ocelli on the same side have exactly the same axis, no
two can receive their rays from the same point of an
object, and thus, as each composite eye is immovably
fixed upon the head, the combined action of the entire
aggregate will probably only afford but a single image,
resembling that which we obtain by means of our
single eyes."*

In other words, this explains the reason, and
answers the question often asked. Why insects, which
have so many eyes, do not see images of the same
object as numerous as their eyes? I should mention
that, besides these composite eyes, insects possess also
rudimentary single eyes, like the spiders; these are
situated on the top of the head ; they are termed
stemmata, and are generally three in number. It is a
curious fact that the larvae of insects undergoing a
complete metamorphosis have these single eyes (stem-
mata) only; the two large composite eyes are de-
veloped during the latter part of the pupal life. If
you have gained a fair knowledge of the structure of a
fly's eye, you can pass on to another organ for study.
Let us take the proboscis, with which we are all so
familiar. The parts of the mouths of insects cannot
fail to afford you an almost boundless source of grati-
fication and delight, and notwithstanding their almost
infinite varieties, they are always composed of the
same essential elements. " You would not think so
indeed ; you would naturally suppose, looking at the

* Dr. Carpenter, " The Microscope," page 663.

USE OF THE MICROSCOPE IN ZOOLOGY. 63

biting jaws of a beetle, the piercing proboscis of a
bug, the long elegantly-coiled sucker of a butterfly,
the licking tongue of a bee, the cutting lancets of a
horse-fly, and the stinging tube of a gnat, that each of
these organs was composed on a plan of its own, and
that no common structure could exist in instruments
so diverse."* But such is the case ; underlying the
great varieties of form in the details there is a com-
mon type. In order, therefore, to get some good
definite idea of the typical insect mouth, you should
examine the parts in that of a beetle, which possesses
them in their most distinct form. You will notice,
then, in a beetle (i) an upper lip, or labrum; (2^ a
lower lip, or labium; (3) a pair of jaws, or mandibles,
which frequently are provided with strong teeth, and
open laterally on either side of the mouth ; (4) a pair
of secondary jaws, maxillce, situated beneath the
mandibles ; these serve to hold the food, the man-
dibles or biting jaws working on it, and to convey it
to the mouth ; (5) one or two pairs of jointed appen-
dages attached to the maxillae, called maxillary palpi ;
(6) a pair of labial palpi. The. under lip, or labium,
is generally composed of several parts, the basal part
being called the chin, or mentum — a wide horny piece
— the upper part being often much prolonged, forming
what has been termed the ligula. Now, it is this
tongue-shaped organ that we see so highly developed
in the common fly, blow-fly, and other relatives. The
plate, p. 64, represents a magnified view of the under side
of the fly's tongue. The broad dark part at the bottom
of the figure is the mentum \ b is the portion formed
by the metamorphosis of the maxillae, being modified
into a kind of sheath for the mandibles, which, in the
fly, assumes the form of a pair of sharp cutting lancets.

* Gosse's " Evenings at the Microscope," page 168.

Proboscis of Fly.

USE OF THE MICROSCOPE IN ZOOLOGY. 65

If you have ever been bitten by a horse-fly, you will
have a lively appreciation of the effects of these
lancets piercing your skin. At c you will notice the
maxillary palpi. But by far the most beautiful piece
of mechanism in the mouth of the fly is the end of
the labium, which consists of two lobes forming the
ligula (a). It is a wide muscular membrane, which con-
tains a number of delicate semi-spiral tubes, through
which the little insect sucks up fluids. These tubes
remind one strongly of the trachea, those exquisite
little spiral vessels by means of which insects breathe,
only there is this difference in their construction — in .
the tracheae the rings are a continuous spire, in the
ligula they are distinct, and do not, as in the tracheae,
surround the whole tube, but perform about two-thirds
of a circle.

" In the Diptera, or two-winged flies, generally, the
labrum, maxillae, mandibles, and the internal tongue
(where it exists), are converted into delicate lancet-
shaped organs, termed setce, which, when closed
together, are received into a hollow on the upper side
of the labium, but which are capable of being used
to make punctures in the skin of animals or the
epidermis of plants, whence the juices may be drawn
forth by the proboscis. Frequently, however, two or
more of these organs may be wanting, so that their
number is reduced from six to four, three, or two. In
die Hymenoptera (bee and wasp tribe), however, the
labrum and the mandibles much resemble those of
mandibulate insects, and are. used for corresponding
purposes. The maxillae, c, (see page 66), are greatly
elongated, and form, when closed, a tubular sheath for
the ligula (e), or ' tongue/ through which the honey is
drawn up ; the labial palpi (£), which are greatly deve-
loped and fold together like the maxillae, so as to form
an inner sheath for the ' tongue,' while the ligula itselt

E

66

THE MICROSCOPE.

Mouth of Bee.

(e) is a long, tapering, muscular organ, marked by an
immense number of short annular divisions, and
densely covered over its whole length with long hairs.
It is not tubular, as some have stated, but is solid ;

USE OF THE MICROSCOPE IN ZOOLOGY.

when actively employed in taking food, it is extended
to a great distance beyond the other parts of the mouth ;
but when at rest it is closely
packed up and concealed
between the maxillae.
' The manner/ says Mr.
Newport, ' in which the
honey is obtained when
the organ is plunged into
it at the bottom of a
flower, is by "lapping,"
or a constant succession
of short and quick exten-
sions and contractions of
the organ, which occasion
the fluid to accumulate
upon it, and to ascend
along its upper surface
until it reaches the orifice
of the tube formed by the
approximation of the
maxillae above, and of the
labial palpi and this part
of the ligula below/ " *

The head of the gnat
is a wonderful organ, and
is provided with numerous
sharp instruments, the
effect of which when punc-
turing the skin is known
to everybody. I ought, Head of Gnat,

however, for the credit of

the sex, to say it is the female alone that practises
blood-letting, the males being harmless in this respect.

* Carpenter's " Microscope," page 667.

E 2

68 THE MICROSCOPE.

The hemispherical head of the gnat, with its two large
compound eyes, will be seen at once to be furnished with
a long, cylindrical proboscis (<:), a pair of antennae (<?),
and a pair of labial palpi (b\ This cylindrical probos-
cis is the homologue of the labium, or lower lip ; it is
covered with lined scales for a considerable portion of
its length, and is expanded at the tip into three pairs
of concave leaves. On the upper side of this pro-
boscis is a groove, out of which spring six long, thin
filaments (d\ representing the mandibles, maxillae,
tongue, and labium. " The labium," writes Mr. Gosse,
" does not enter the wound. If you have ever had
the philosophic patience to watch a gnat while punc-
turing your hand, you have observed that the knob
at the end of the proboscis is applied to the skin, and
that then the organ lends with an angle more and
more acute, until at length it forms a double line,
being folded on itself, so that the base is brought into
close proximity to the skin. Meanwhile the lancets
have all been plunged in, and are now sunk into your
flesh to their very bottom, while the labium, which
formed merely the sheath for the whole, is bent up
upon itself, ready again to assume its straight form as
soon as the disengaged lancets require its protection."*
The proboscis, or hausiellum, of the Lepidoptera
(butterfly and moth tribe) will furnish you with a large
stock of interesting matter for study. The long spiral
organ must be familiar to the most castia', observer.
An examination of the structure of a butterfly's mouth
will show us that the most important organs are here
represented by the maxillae, which are immensely
elongated. The labrum and mandibles have their
homologues in three small triangular plates, not easy to
discover ; the labial' palpi appear one on each side of
the spiral coil. The maxillae are united, and form a
* " Evenings at the Microscope," page 183.

USE OF THE MICROSCOPE IN ZOOLOGY. 69

tube by the union of their grooves; the juices of the
flowers are sucked up by means of the proboscis, but
what the precise mechanical action may be is a matter
of doubt. On the tips of the haustella of some of
the Lepidoptera are small papilliform bodies, project-
ing at a considerable angle ; it has been conjectured
that they are organs of taste, but nothing is known as
to their functions.

In the flea, the mandibles are represented by a .
pair of very sharp, razor-like instruments, which are
situated on each side of the tongue ; the maxillae,
which appear in the form of a pair of elongated
flattened bands, serve as sheaths for the mandibles.
The labial palpi also, in the flea, are cutting instru-
ments. You must not expect to be able to make out
all these details without a good deal of patient care,
and without many failures at first ; but persevere, and
you will be rewarded by success in time. I would
recommend you to begin with the study of the struc-
ture of insects' mouths, by selecting some large beetle,
as a cockchafer. After you have killed it, cut off the
head, and examine the various parts with a low power
of the microscope. Place the head in a gutta-percha
trough of water, and with dissecting-needles separate
the component parts, viewing the insect's head first
on the dorsal aspect, then on the ventral ; be careful
to notice the relative position of the parts, and do
not proceed to the examination of another species
till you have thoroughly mastered one. You lose
no time by such a proceeding ; oh the contrary, you
are really saving time, because the knowledge acquired
by such thorough kind of work will so imprint itself
on your mind, that you will be saved much time that
would otherwise be lost, from repeated attempts to
verify some point which a careful preliminary study
would have settled at a glance.

CHAPTER VII.
THE MICROSCOPE IN ZOOLOGY (continued).

EVERY part of an insect is worthy of attentive study ;
the head with its various appendages, the wings, legs,
eyes, spiracles, stings, and ovipositors, &c. &c., will
come under your examination. You. must often have
been struck with the extraordinarily rapid movements
of various insects through the air. You have been
lying awake in an early morning on your bed, and
have noticed the ease and grace with which the little
house-fly performs, in company with his companions,
his dancing gyrations. Now one individual darts
backwards with the rapidity almost of thought, and
another is soon seen to accomplish the same feat.
Her gauze-like wings, moved by the strong muscles
of the thorax, vibrate 600 or 800 times in a single
second, and even considerably more if she will it.
Our little fly, say Kirby and Spence, in her swiftest
flight will go more than the third of a mile a
minute. Now compare the infinite difference of the
size of the two animals (ten millions of the fly would
hardly counterpoise one racer), and how wonderful
will the velocity of this miniature creature appear!
Did the fly equal the racehorse in size, and retain its
present powers in the ratio of its magnitude, it would
traverse the globe with the rapidity of lightning. The
organs by means of which such wonderful results are
accomplished must be worthy of your patient ex-
amination. The wings of many insects, as bees and

" Introduction to Entomology," vol. ii., p. 362.

THE MICROSCOPE.

wasps, dragon-flies, two-winged flies, are made up of
a double layer of membrane, with a number of veins
or " nervures," within which there are generally found
air-vessels, or tracheae. These nervures, by their

Common Fly.

subdivision and reunion, form in some cases an ex-
ceedingly beautiful network ; this is especially ob-
servable in some of the smaller Neuroptera. Besides
spiral vessels, or tracheae, the nervures contain a fluid
supplied from the body, so that both air and blood
circulate in them ; the membrane of the wing often pre>
sents an appearance of cellular areolation, as you will
see in the above figure of the common fly. Although
to the unassisted eye the membrane appears to be
clear, transparent, and homogeneous, under the micro-
scope you will see it is covered with short stiff hairs ;
in the fly there is a single hair in each areola, of the
form of a curved spine. In the wings of the Hy-

THE MICROSCOPE IN ZOOLOGY, 73

menoptera — as the bees, wasps, &c. — there often exists
a beautiful apparatus for connecting together the two
wings on either side, so that they may present one
large flat surface wherewith to strike the air and not
overlap one another ; along the front edge of the hind
wing there is a row of curved hooks ; the front wing
near its base is doubled over so as to form a groove
or slit into which the hooks fasten. You will see this
structure readily enough in the wings of the wasp.
In some insects the wings are strengthened by a thick
layer of horny substance intervening between the two
membranes, as in the Coleoptera, or beetle tribe, where
the front wings are no longer instruments of flight,
but coverings for the hind wings. In the Orthoptera
(grasshoppers, crickets, &c.) the front wings contain
much horny matter, but they are not consolidated to
the same extent as in the beetle tribe. If you will
examine a fly or other two-winged insect, you will
notice at the base of each of the front wings two
small projecting organs (halteres), the rudimentary
representatives, it is believed, of the posterior wings.
What is the function of the halleres ? Dr. Braxton
Hicks considers they minister to the sense of smell.
Mr. Lowne, in his recent excellent monograph on the
anatomy of the blow-fly, thinks they are organs of
hearing. Each haltere is a little fleshy cylinder ter-
minating in a small knob, having a thickened base
clothed with fine hairs. The globular extremity is
hollow, according to Mr. Lownes, and contains
numerous round spots, which he regards as otoconia.
The wing of the house-cricket contains the apparatus
by means of which its well-known characteristic
sounds are produced. I have a specimen before me
as I write. On each of the upper wings there is a
large clear space of a sub-triangular form, bounded
on one side by a thick dark-coloured nervure with

74 THE MICROSCOPE.

three or four longitudinal ridges ; the inner margin
of this nervure spreads out into a thin, narrow mem-
brane ; other nervures, much smaller than the dark
one, border the space which forms a drum, or tym-
panum. In front of the drum is clearly to be seen a
transverse side with numerous file-like teeth, from the
middle portion of which side there proceed three
nervures ; two are simple ; the other, which is con-
nected at the base to the file by three short and
strong processes, branches into two parts. All these
three nervures are strong at the base, and then become
attenuated ; they stretch across the tympanum till they
touch and become part of the narrow membrane of
the large dark nervure spoken of above. The insect
then produces the sound by rubbing the wings to-
gether; the files are rapidly drawn one across the
other, and the sound greatly intensified by the action
of the drum, or tympanum, I have endeavoured to
describe. I ought, however, to say that some ob-
servers believe the sound is produced by the rubbing
of the file across the large longitudinally -ridged
nervure. It would be difficult to decide the point,
but I can readily conceive either mode would produce
the well-known sound.

You will be struck with the beautiful iridescent
hues observable in the wings of some insects. The
aphides, or plant-lice — those noxious pests known to
farmers as " smother fly/' and to the popular mind as
"blight" — exhibit this iridescence in a remarkable
degree. By turning the wing you may be examining
to various directions, you will ascertain the angle at
which the iridescent hues are best seen.

The feet of insects will be sure to occupy your
attention, and their study to afford you delight. The
foot of the house-fly is a very common microscopic
object, and one especially interesting. It has long

THE MICROSCOPE IN ZOOLOGY.

75

Plant Lice.

been a question how the fly and other insects can
maintain their position in an inverted attitude. The
foot, or tarsus, of the fly consists of five pieces, " the
first of which contains a pair of muscles which move
the second upon it, but the remaining four contain
none," The last joint has a pair of pads (pulvillt)^

76 THE MICROSCOPE.

and above them a pair of sharp hooks. On the.
interesting question alluded to above, I shall give you
what Mr. Lownes has lately written thereon. " The
foot-pads are amongst the most interesting parts of
the insect, because they enable it to walk upon
smooth surfaces in an inverted position, apparently
in defiance of the laws of gravity. Long ago this was
first ascribed, by Dr. Derham, to the exhaustion of
air from the foot-pads ; recently it has been supposed
to be due to the exhaustion of air from the extremities
of the hairs with which the pad is closed; others
have ascribed it to the hold which these minute hairs
take of trifling irregularities of surface; but none of
these explanations are correct, and one of the earliest
notions upon the subject is the nearest to the truth —
that is, that the feet secrete a glutinous fluid which
glues them to the surface on which the insect walks.
When the pads are carefully examined, it will be seen
that they have no cup -shaped cavity beneath them,
but that they are hollow with a nipple-like pro-
tuberance projecting into each. This will be seen
more plainly by pressing upon the tarsus which forces
it into the pad ; by cutting off the end of the pad
first it may be exposed in this manner, and will be
found to consist of a closed sac. This sac fills the
whole of the last four tarsal joints, and is lined with
pavement epithelium; it secretes a perfectly clear viscid
fluid, which exudes from it into the pad, and fills its
cavity, as well as the hollow hairs with which its under
surface is covered. These hairs open by trumpet-
shaped mouths, and the disc of each mouth is kept
full of the fluid. Sometimes, when the insect is cap-
tured and held between the finger and thumb, it
exudes so rapidly that the pads are soon covered with
a little glistening drop of it, which may be collected
upon a glass slide, where it rapidly solidifies. It is

THE MICROSCOPE IN ZOOLOGY.

77

insoluble in water, and solidifies under that fluid.
The whole contents of the tarsus becomes solid very
rapidly as soon as the insect is dead, or the part is
removed.

" There is no essential difference in the pads of flies
and the pulvilli of beetles, moths, and other insects ;
the same fluid is secreted in all. The
only difference is that the pads of flies
are membranous and transparent, in-
stead of hard and opaque.

" The feet of the smaller house-fly
are the best to show the manner in
which the viscid fluid exudes from the
extremities of the trumpet-shaped hairs,
as they are \ery large in this species,
and a glistening bead of fluid can be
seen plainly at the extremity of each
hair by placing the living insect under
the microscope. The footprints left
upon glass by flies consist of rows of
dots corresponding to these hairs ; this
is best seen in those of the lesser house-
fly from their greater size. The whole
appears precisely analogous to the
manner in which caterpillars and spiders
suspend themselves by silken threads.
In both cases the fluid is exuded from minute pores,
and bears the weight of the insect, the only difference
being in the nature and quantity of the fluid exuded.
Much discussion has arisen as to the manner in which
flies liberate their feet, and it has even been objected
that they would become so firmly adherent after a
time that the insect would be glued to the spot.
Nothing can be simpler than the arrangement by
which the foot is liberated, and in the healthy insect
the secretion probably never becomes solid as long as

78 THE MICROSCOPE.

it remains in contact with the foot. It is sufficiently
glutinous, even in the fluid, or rather semi-fluid, state
it assumes as it exudes, to sustain the weight of the
insect, when the strain is put equally upon all the
hairs, of which there are about 1,200 on each pad;
but when the pad is removed obliquely, so that each
row is detached separately, the resistance amounts
practically to nothing. A neat experiment will
demonstrate this, even to the most sceptical. If a
piece of adhesive label be cut for convenience into a
pear-shaped disc, an inch in diameter, and caused to
adhere to the hand by slightly damping it, a force of
many pounds applied to the narrow extremity in the
axis of the paper- will not stir it, whilst it is imme-
diately removed with very little resistance, when the
force is applied so as to lift it gradually up.,

" The direction and length of the hairs upon the pad
are so adapted to the oblique direction in which the
strain is put upon them when the tarsus is straight,
that the insect has a perfectly secure hold; this is
immediately released as soon as the tarsus is curved,
which is effected by the long slender tendon already
mentioned. In the small house-fly, the pads them-
selves are capable of being curved, for the tarsal tendon
branches, and is inserted into the distal extremity of
the pad."*

I will select one more insect's foot for examination,
and that shall be the hind-foot of the bee. I have
just caught a hive-bee as it was gathering pollen from
mignonette, a flower to which bees resort much for
the sake of the pollen-grains. I see on each of the
hind-legs a reddish-yellow globular mass of substance
adhering to its middle portion. After killing the bee
by putting it under an inverted tumbler with some

* "Anatomy of the Blow-fly ; " pp. 20— 22.

THE MICROSCOPE IN ZOOLOGY.

79

bruised laurel leaves (the effect of the fumes of prussic
acid on bees is very rapid), I
cut off its hind-legs, and with
a camel's-hair brush and water
wash away that pollen mass.
At the juncture of the femur
and tibia I notice a deep nick
or cavity, and on submitting
this to microscopic investiga-
tion, I find a number of red-
dish-coloured spines arranged
around the cavity of the femur;
the upper part of the tibia is
also hollowed out into a cavity ;
the remaining part of the tibia
contains a number of brushes
or hairs, by means of which the
pollen is taken from the flowers
of various plants. But how
does the pollen get from the
brushes into the pocket? It
is evident this cannot be done
from the same leg. The bee
rubs the pollen-grains off one
leg into the pocket of the other,
and the series of strong comb-
like spines render material aid
in their deposition there. When-
the bee is loaded, off she flies
to the hive, where the pollen
mass is mixed with honey, de-
posited in cells, forming the
"bee-bread" with which the
young bee-grubs are fed.

The stings and ovipositors of insects are very inte-
resting objects to study. The Hymenoptera will afford

Hind Foot of Bee.

8o THE MICROSCOPE.

numerous forms of these instruments. In the bees,
wasps, hornets, ants, the last segment of the body is
provided with a sting ; the ichneumon, saw-flies, gall-
flies, are furnished with an ovipositor; in external
form there is not very much difference between an
ovipositor and a sting. The sting consists, in wasps,
bees, &c., of two very sharp dart-like organs, with
barbed teeth at their points ; this apparatus is enclosed
in a horny, elongated sheath; near the root of the
sting you will find a membranous bag, which contains
a poisonous fluid ; between the darts there is a canal,
down which the venom is poured into the wound
made by them. The ovipositors of insects differ
somewhat in form, but they all consist of a long tube
protected and covered by a cleft sheath. That curious
hymenopterous insect, not uncommonly met with in
this country, the Sir ex gigas, and generally taken for
some kind of hornet by the ignorant of such matters,
has a very strong ovipositor, by means of which the
insect can bore into hard timber. The Cynipidtz, or
gall-insects, so extremely common on various parts of
the oak, have a very delicate ovipositor, with a toothed
edge ; using this instrument as a kind of saw, the little
insect bores a hole in some part of the tree, and
deposits therein its egg. It is supposed that some
irritating fluid is dropped into the hole at the same
time as the egg, which produces what are known as
" galls." These serve both as shelter and food for the
young grubs of the gall-flies. You will be struck with
the beauty of the spiracles and tracheal system of in-
sects, the apparatus by means of which the respiration is
carried on. In insects the blood is oxygenated by the
admission of air into every part of the body, even into
the most minute; the air enters through the spiracles,
which are situated at each side of the body, and pass-
ing down the tracheae, which branch off into numerous

THE MICROSCOPE IN ZOOLOGY. 8*

ramifications, is conveyed to every part of the system.
" The structure of the air-tubes," as Dr. Carpenter
says, " reminds us of that of the spiral vessels in
plants, which seem destined (in part at least) to perform
a similar office ; for. within the membrane that forms
that outer wall, an elastic fibre winds round and round,
so as to form a spiral closely resembling in its position
and functions the spiral wire-spring of flexible gas-
pipes ; within this again, however, there is another
membranous wall to the air-tubes, so that' the spire
winds between their inner and outer coats." There is
much difference in the form of the spiracles, or stigmata,
as they are also called ; but in most cases the opening
is protected by a sieve or grating formed by hairs or
branches of the integument; these prevent particles
of dust, &c., from getting into the air-vessels. Some
of the large caterpillars of the Sphinx-moths show the
stigmata very clearly even to the naked eye.

CHAPTER VIII.
THE MICROSCOPE IN ZOOLOGY (continued).

You will find much to admire in the examination of
the eggs of insects, which are often of great beauty.
The butterfly tribe (Lepidopterd) furnish some of the
most interesting forms, and those ot the garden white
or cabbage butterfly are too common on the leaves of
that vegetable. The eggs of the water-scorpion (Nepa
cinered) are very curious ; they are of an oval form,
and one end is surmounted by seven stiff reflexed hairs
or filaments. The eggs of the mangold-worzel fly
(Ant homy ia beta) have their surfaces very symmetri-
cally marked. In the summer of 1861 these flies

F

82

THE MICROSCOPE.

were so numerous that they committed serious damage
on the crops in many parts of England. From the
eggs are produced small larvae, which at once bore a
hole in the leaves, and tunnel between the cuticles ;

Egg of Mangold- Worzel Fly magnified.

whole fields soon present an appearance as if the
leaves of the plants had suffered from some scorching
influence. The larvae, when full grown, drop out of
the leaves and turn to pupae in the earth. The eggs

of the common gnat
( Ctilex pipietis} are de-
posited, by the aid of
the insect's hind-legs,
in a small boat-shaped
mass, which floats upon
the surface of the water.
They are of a longish
oval form with a small
knot at the top, and all
are packed closely to-
The larvae, whose peculiar twistings and

The Boat, Eggs, and Egg of a Gnat.

gether.

jerkings must be familiar to everybody who has ever
looked into a rain-tub, are very active little creatures,
and interesting objects for microscopic study.

The hairs and scales which beset the surface of
many insects will long afford you delight. The dust
which so readily comes off the wings of butterflies and
moths will be found to exhibit, under the microscope,
very beautiful forms. These scales are deposited in
regular layers upon each side of the membranous

THE MICROSCOPE IN ZOOLOGY. 83

wings — for if you rub the dust off the wings, you will
see they are membranes — like the tiles on the roof of
a house. It is the scales that give the brilliant hues
to the wings; one patch being red, another green,
another brown or yellow. There is great variety of
form in the scales even of the same insect ; those on
the wings are generally broad, those on the legs long
and slender. Now examine carefully the form of a

The Gnat and her Boat of Eggs.

single scale ; you will see that each one is furnished
with a short pedicel or foot-stalk ; carefully wash
away all the dust off the wing you are examining, and
attend to the membrane only, You will see regular
rows of small sockets ; into' these sockets the foot-
stalks of the scales are fitted. The foot-stalks of the
scales vary according to the species. The little azure
blue butterfly (Polyommatus Alexis)^ so common in the
summer months, will supply you with a form of scale
termed "battledore scale," the footstalk of which
forms quite a long handle. These scales are marked
by longitudinal ribs, which swell into round elevations

84 THE MICROSCOPE.

at intervals, each with a black point in its centre.
The metallic lustre of the scales of the diamond
beetle -of South America (Curculio imperialis) will
astonish you from its gorgeous magnificence. I have
a specimen before me as I write, but I cannot de-
scribe it better than in the words of Mr. Gosse. " We
look at it by reflected light, with a magnifying power
of 130 diameters. We see a black ground on which
are shown a profusion of what look like precious
stones, blazing in the most gorgeous lustre. Topazes,
sapphires, ametl.ysts, rubies, emeralds seem here sown
broadcast, and yet not wholly without regularity, for
there are broad bands of the deep black surface where
there are no gems, and, though at considerable diversity
of angle, they do all point, with more or less precision,
in one direction — viz., that of the bands. These gems
are flat, transparent scales, very regularly oval in form,
for one end is rather more pointed than the other ;
there is no appearance of a foot-stalk, and by what
means they adhere I know not. They are evidently
attached in some manner by the smaller extremity to
the velvety black surface of the wing-case. The
gorgeous colours seem dependent in some measure on
the reflection of light from their polished surface, and
to vary according to the angle at which it is reflected.
Green, yellow, and orange hues predominate ; crim-
son, violet, and blue are rare, except upon the long
and narrow scales that border the suture of the wing-
cases, where these colours are the chief reflected."*
Mr. Gosse, however, thinks there is some positive
colour in their substance.

The scales of fish, the feathers of birds, the hairs of
insects, insect-larvae, and mammalia, will afford you
matter for contemplation and study. Scales of fish

* " Evenings at the Microscope," page 99.

THE MICROSCOPE IN ZOOLOGY. 85

are developed in the substance of the true skin ; but
those of reptiles, the feathers of birds, the hairs, nails,
claws, and horns of mammalia, are developed, not
within, but upon the surface of the true skin. The
scales of fish are either ctenoid, i.e., furnished at their
posterior extremities with comb-like teeth, as the
scales of the sole ; cycloid, having scales more or less
round, as in the salmon, roach, herring, &c. ; ganoid
(from a Greek word ganos, " splendour "), having scales
whose substance is essentially bony, hard, and highly
polished (this kind has few existing representatives,
but numbers are found as fossils) ; or placoid, i.e.,
having scales separately embedded in the skin, and
projecting from its surface in various forms. "In
studying the structure of the more highly developed
scales, we may take as an illustration that of the carp,
in which two very distinct layers can be made out by
a vertical section, with a third but incomplete layer
interposed between them. The outer layer is com-
posed of several concentric laminae of a structureless
transparent substance, like that of cartilage ; the outer-
most of these laminae is the smallest, and the size of
the plates increases progressively from without in-
wards, so that their margins appear on the surface as
a series of concentric lines, and their surfaces are
thrown into ridges and furrows which commonly have
a radiating direction. The inner layer is composed of
numerous laminae of a fibrous structure, the fibres of
each laminae being inclined at various angles to those
of the laminae above and below it. Between these
two layers is interposed a stratum of calcareous con-
cretions, resembling those of the skin of the eel;
these are sometimes globular or spheroidal, but more
commonly 'lenticula/ that is, having the form of a
double-convex lens."* The scales of the eel are con-

* Dr. Carpenter, page 702.

86 THE MICROSCOPE.

cealed within the skin; they are oblong in shape,
and seem to be composed principally of round cal-
careous bodies, arranged in many regular concentric
series. The scale of the eel is a beautiful object for
the polariscope.

If you will pluck a hair out of your head, and hold
it between your forefinger and thumb, with the root of
the hair upwards, and then move your finger and
thumb up and down, you will notice the hair to
ascend ; now do the same with the root downwards,
and the hair descends. How is this ? Let us examine
its structure under the microscope. Under a magni-
fying power of about 400 diameters, you will notice
that the outer surface of the hair is marked by irregular
lines, the indications, as Dr. Carpenter remarks, of
the imbricated arrangement of the flattened cells or
scales which form the cuticle layer, for all hairs
essentially consist of two elementary parts, a ciiticle, or
investing substance, of a dense horny structure, and a
medullary, or pith-like substance, usually of a much
softer texture, occupying the interior. The cuticle
part consists of flattened scales arranged in an imbri-
cated manner ; the medullary substance is composed
of large spheroidal cells. In human hair the cuticle
layer is very thin ; the medullary portion, which is of
a fibrous nature, constitutes the principal part of the
shaft of the hair. These fibres may be separated from
each other if the specimen be macerated in sulphuric
acid for a time, and then crushed between two pieces
of glass. Each fibre is a long spindle-shaped cell.
The imbricated scales of the cuticle layer may be
isolated if the specimen be treated with an acid or an
alkali. It is in consequence of the position of these
imbricated scales that the upward or downward motion
of the hair, when moved between the finger and
thumb, takes place, the ed^es of the scales being

THE MICROSCOPE IN ZOOLOGY. 87

arranged in the direction of the apex of the hair. The
colour of the hair is due to the presence of pigment-
granules and air-cells diffused through its substance.
The hairs of bats are very curious ; they have projec-
tions on their surface, formed by extensions of the
scales of the cuticle layer. The hair of a species of
Indian bat reminds one of the branch of an equisetum,
long, narrow, leaf-like scales being arranged round the
shaft in regular whorls. In the mole and other
insectivora the cells of the medulla are very distinct.
Amongst ruminant animals great variety occurs in the
structure of the hair, whilst the camel's hair exhibits
pretty nearly the same structure as that of the higher
classes. The musk-deer's hair consists almost entirely
of the inner medullary layer ; the cuticle layer is
nearly absent. Nor must we regard this structure of
the hair of animals merely as an interesting subject,
for as Mr. Gosse has well said, in his charming " Even-
ings at the Microscope," England's time-honoured
manufacture, that which affords the highest seat in
her most august assembly, depends on the imbricate
surface of hairs. "The hat on your head, the coat on
your back, the flannel waistcoat that shields your
chest, the double hose that comfort your ankles, the
carpet under your feet, and hundreds of other neces-
saries of life, are what they are because mammalian
hairs are covered with sheathing scales.

" It is owing to this structure that those hairs which
possess it in an appreciable degree are endowed with
the property of felting; that is, of being, especially
under the combined action of heat, moisture, motion,
and pressure, so interlaced and entangled as to be-
come inseparable, and of gradually forming a dense
and cloth-like texture. The ' body/ or substance, of
the best sort of men's hats is made of lamb's wool
and rabbit's fur, not interwoven, but simply beaten,

88 THE MICROSCOPE.

pressed, and worked together between damp cloths.
The same property enables woven woollen tissues to
become close and thick ; every one knows that worsted
stockings shrink in their dimensions, but become much
thicker and firmer, after they have been worn and
washed a little; and the ' stout broadcloth' which has
been the characteristic covering of Englishmen for
ages, would be but a poor open flimsy texture but for
the intimate union of the felted wool-fibres, which
accrues from the various processes to which the tabric
has been subjected.

" In a commercial view, the excellence of the wool

Hair of Larva of Dermestes.

is tested by the closeness of its imbrication. When
first the wool-fibre was submitted to microscopical
examination, the experiment was made on a specimen
of merino : it presented 2,400 serratures in an inch.
Then a fibre of Saxon wool, finer than the former, and
known to possess a superior felting power, was tried :
there were 2,700 serratures in an inch. Next a speci-
men of Southdown wool, acknowledged to be inferior
to either of the former, was examined, and gave 2,080
serratures. Finally, the Leicester wool, whose felting
property is feebler still, yielded only 1,850 serratures
per inch. And this connection of good felting quality
with the number and sharpness of the sheathing scales
is found to be invariable."

The hairs of insects, caterpillars, &c., are of infinite
variety of form. The hairs of the larva of the bacon
beetle (Dermestes} are of two kinds : in one, the shaft
is covered with minute spinous secondary hairs closely

THE MICROSCOPE IN ZOOLOGY. 89

packed together ; the spines or scales in the others are
placed in regular whorls, the highest of which is .com-
posed of knobby spines, the whole shaft being " sur-
mounted by a curious circle of six or seven large fila-
ments attached by their pointed ends to its shaft,
whilst at their free extremities they dilate into knobs."
I have no doubt that you will find much to occupy
your attention, and to afford you delight in the exami-
nation of thin sections of bone. " Bone consists of a
hard and soft part ; the hard is composed of carbonate,
phosphate, and fluate of
lime, and of carbonate and
phosphate of magnesia, de-
posited in a cartilaginous
or other matrix ; whilst the
soft consists of that matrix,
and of the periosteum which
invests the outer surface of
the bone, and of the me-
dullary membrane which

lines its interior or medullary cavity, and is continued
into the minutest pores." You can, if you like, pre-
pare the sections of bone for examination, or you can
buy specimens already ground and mounted at a small
cost. With a thin sharp saw you must make as thin
a section as possible, and this must be ground down
on a hone, or be rubbed between two smooth hones
till you get the desired tenuity. Let the specimen
be further polished on a piece of plate glass, in order
to obliterate the scratchings caused by the friction on
the hone. If it is a long bone you wish to examine,
you should make a longitudinal section ; if a flat bone,
the section should be made parallel to its surface.
You will then see it is traversed by a great number of
canals, called Haver sian canals, after their discoverer,
Havers. These canals are in connection with the

9o

THE MICROSCOPE.

central cavity, and like it are filled with marrow. By
examining a transverse section of a long bone you
will see that the small orifices of the canals are in the
centre of the layer forming the bone, which is arranged
round them in concentric rings ; between these layers
are small open spaces called lacuna. They are cavi-
ties from which the canaliculi — extremely minute
spider-like tubules, which perforate the bony layers and
communicate with the central Haversian canal — pro-
ceed. Blood-vessels, from the membrane surrounding
the bone termed the periosteum, are traceable intQ the
Haversian canals. The canaliculi are too small to
allow the admission of blood-corpuscles. I may here
mention the effect of madder, when given to- an animal
in its food, upon the osseous system. The bones
become coloured with a
deep red tinge. The bones
of a pigeon were rendered
red in about twenty-four
hours ; it took three weeks
to colour the bones of a
young pig. Both the external
and internal laminae of the
bone are found to be affected
by the colouring matter,
proving thereby that the
action takes place on those
parts which lie in contact
with blood-vessels.

You will be interested to
hear that an intimate know-
ledge of the structure of bone, as acquired by
the aid of the microscope, has proved of immense
value in determining the tribe of animals to which
bones belonged. I shall quote Dr. Carpenter's graphic
words : " From the average size and form of the

Section of Humerus of Turtle.

THE MICROSCOPE IN ZOOLOGY. 91

lacuna, their disposition in regard to each other and
to the Haversian canals, and the number and course
of the canaliculi, the nature of even a minute fragment
of bone may often be determined with a considerable
approach to certainty, as is shown by the following
examples, among many which might be cited — Dr. Fal-
coner, the distinguished investigator of the fossil re-
mains of the Himalayan region, and the discoverer of
the gigantic fossil tortoise of the Sivalik hills, having
met with certain small bones about which he was doubt-
ful, placed them in the hands of Professor Quekett
for minute examination; and was informed, on micro-
scopic evidence, that they might certainly be pronounced
reptilian, and probably belonged to an animal of the
tortoise tribe ; and this determination was fully borne
out by the evidence, which led Dr. Falconer to con-
clude they were toe-bones of his great tortoise. Some
fragments of bone were found some years since in a
chalk-pit, which were considered by Professor Owen
to have formed part of the wing-bones of a long-
winged sea-bird allied to the albatross. This deter-
mination, founded solely on consideration derived
from the very imperfectly preserved external forms of
these fragments, was called in question by some other
palaeontologists, who thought it more probable that
these bones belonged to a large species of the extinct
genus Pterodactylus, a flying lizard, whose wing was
extended upon a single immensely prolonged digit.
No species of Pterodactyle, however, at all comparable
to this in dimensions was at that time known ; and the
characters furnished by the configuration of the bones
not being in any degree decisive, the question would
have long remained unsettled, had not an appeal been
made to the microscopic test. This appeal was so
decisive — by showing that the minute structure of the
bone in question corresponded exactly with that of

92 THE MICROSCOPE.

the Pterodactyle bone, and differed essentially from
that of every known bird — that no one who placed
much reliance upon that evidence could entertain the
slightest doubt on the matter. By Professor Owen,
however, the validity of that evidence was questioned,
and the bone was still maintained to be that ot a bird ;
until the question was finally set at rest, and the value
of the microscopic test triumphantly confirmed, by
the discovery of undoubted Pterodactyle bones of cor-
responding, and even of greater dimensions, in the
same and other chalk quarries."*

CHAPTER IX.

THE MICROSCOPE IN PHYSIOLOGY.

BY the aid of the microscope we become acquainted
with the wonderful structure of skin and other animal
tissues. This figure represents a section of human skin,
which is found to consist of two principal layers — the
cutis vera, or true skin, and the cuticle, or epidermis,
which covers it. A thin vertical section of the skin
of the finger shows the upper layer, or cuticle, at a; the
lower part, or cutis vera, at b; sweat-glands, e, with
their ducts, at c, leading to the orifices ; the small
granular clusters at / are fat-cells ; the dull-coloured,
wavy portion at b is the rete mucosum, or stratum
Malpighii. Mingled with the cells which make up
the epidermic covering are found others, which, from
their secreting colouring matter, are called pigment-
cells. An extraordinary number of blood-vessels,
twisting so as to form a complete network of capillaries
and numerous nerves, are distributed through the cutis

* Dr. Carpenter, page 764.

THE MICROSCOPE IN PHYSIOLOGY.

93

rera, and you know it is impossible to prick any part
of your finger with the fine point of a needle without
piercing some of these capillaries and drawing blood.
The cuticle, or outer covering, is destitute of blood-
vessels and nerves ; it consists of a series of layers of

.a

cells " that are continually wearing off at their outer
surface, and renewed at the surface of the true skin,
so that the newest and deeper layers gradually become
the oldest and most superficial, and are at last thrown
off by desquamation. In their progress from the
internal to the external surface of the epidermis, the
cells undergo a series of well-marked changes. When

94 THE MICROSCOPE.

we examine the innermost layer, we mid it soft and
granular, consisting of germinal corpuscles in various
stages of development into cells, held together by a
tenacious semi-fluid substance. This was formerly
considered as a distinct tissue, and was supposed to
be the peculiar seat of the colour of the skin ; it
received the designation of Malpighian layer, or rete
mucosum. Passing outwards, we find the cells more
completely formed ; at first nearly spherical in shape,
but becoming polygonal where they are flattened one
against the other. As we proceed further towards the
surface, we perceive that the cells are gradually more
and more flattened until they become mere horny
scales, their cavity being obliterated; their origin is
indicated, however, by the nucleus in the centre of
each. This change in form is accompanied by a
change in the chemical composition of the tissue,
which seems to be due to the metamorphosis of the
contents of the cells into a horny substance identical
with that of which hair, horn, nails, hoofs, &c., are
composed."* You will notice, on reference to the
figure, that the lower stratum of the epidermis — i.e.,
the Malpighian layer — is regularly hollowed out into
small depressions, into which the upper surface of the
cutis vera rises in the form of little ridges, or papilla,
from which nerves and blood-vessels arise. The colour-
ing matter contained in the " pigment-cells " is most
abundant in the Malpighian layer ; they are generally
polygonal in form, and contain a number of extremely
minute roundish black granules. I have before me a
small portion of the dark-coloured vascular membrane
of the eye of a sheep, called the choroid, and see the
numerous cells of the layers of pigment very plainly.
In dark-coloured races the pigment cells of the skin

* Carpenter on the Microscope, p. 718.

THE MICROSCOPE IN PHYSIOLOGY. 95

are black ; in white races they are pink. It is clear
that these pigment cells are confined to the cuticle
and Malpighian stratum alone ; for the cutis vera of
a negro is as pink as that of the fairer races, so that
the colour is not even " skin deep/' The subject of
epidermic pigment-cells has always appeared to me to
be full of deep and curious interest. How are these
pigment-cells affected ? Why are they black in the
negro, olive in the Mongolian, copper-coloured in the
North American, pink in the Saxon ? Why are they
altogether absent in the Malpighian layer of albinoes ?
The sun would appear to have the power of darkening
the pigment-cells, for the exposed parts of a negro
are blacker than those which are unexposed. The
Jews, moreover, who settled centuries ago in India,
"have become as dark as the Hindoos around them."
But even in the same individual these epidermic pig-
ment-cells are subject to change. " Can the Ethiopian
change his skin ? " asks the Hebrew prophet. Cases
of such change of colour have occasionally occurred.
" One case is that of a negro slave in Kentucky, aged
forty-five, who was born of black parents, and was
himself perfectly black until twelve years of age. At
that time a portion of the skin, an inch wide, encircling
the cranium, just within the edge of the hair, gradually
changed to white, also the hair occupying that locality.
A white spot next appeared near the inner canthus of
the left eye ; and from this the white colour gradually
extended over the face, trunk, and extremities, until
it covered the entire surface. The complete change
from black to white occupied about ten years ; and
but for the hair, which was crisped or woolly, no one
would have supposed at this time that his progenitors
had offered any of the characteristics of the negro,
his skin presenting the healthy vascular appearance of
that of a fair-complexioned European. When he was

g6 THE MICROSCOPE.

about twenty-two years of age, however, dark copper-
coloured or brown spots began to appear on the face
and hands, but these have remained limited to the
portions of the surface exposed to light. About the
time that the black colour of the skin began to dis-
appear, he completely lost his sense of smell ; and
since he has become white, he has had measles and
hooping-cough a second time." This occurred in
1852. A case of partial disappearance of the black
colour of the negro's skin was brought by Dr. Inman
before the Zoological section of the British Association
at Liverpool in 1854.*

You notice the perspiratory glands and ducts figured
in the engraving at c and g. By means of these organs
a transpiration of fluid holding excrementitious matters
in solution takes place. -The glands consist of a
number of long convoluted tubes, at first dividing into
two branches, and then re-uniting into a single tube or
duct opening at the surface of the epidermis. The
number of these perspiratory pores is enormous.
" To arrive at something like an estimate of the value
of the perspiratory system," says Mr. Erasmus Wilson,
" I counted the perspiratory pores on the palm of the
hand, and found 3,528 in a square inch. Now each
of these pores being the aperture of a little tube of
about a quarter of an inch long, it follows that, in a
square inch of skin on the palm of the hand there
exists a length of tube equal to 882 inches or 7 3! feet.
The number of glands in other parts of the body is
sometimes greater, sometimes less than this ; 2,800
may be taken as the average number of pores in each
square inch throughout the body. Now the number
of square inches of surface in a man of ordinary
stature is about 2,500 ; the total number of pores,

* Carpenter's " Principles of Human Physiology," p. 851, note.
Sixth Edition.

THE MICROSCOPE IN PHYSIOLOGY. 97

therefore, may be about seven millions, and the length
of the perspiratory tubing would thus be 1,570,000
inches, or nearly 28 miles. "

I have in a previous chapter called your attention
to the circulation oi the blood in various animals ; the
blood itself is an interesting subject for study. Blood
consists, in a great measure, of numerous floating cells,
called corpuscles. These are of two kinds, the red and
the white. The former are always in the shape of a
flattened disc, but they differ in size and configuration:
In man and in most of the mammalia they are circular;
in the camel tribe, however, they are oval, as they are in
birds, reptiles, and fishes. In the blood of oviparous
vertebrata, the blood-corpuscles have a dark central
spot, or nucleus, composed apparently of a mass of
small granules. If a drop of acetic acid be added
to the blood-discs under examination, this will be
distinctly seen, the opacity of the nucleus being
increased. The average size of human corpuscles
nas been estimated at about -g-gVo °f an mcn m dia-
meter. " The smallest red corpuscles known," says
Dr. Carpenter, " are those of the musk-deer, whilst the
largest are those of that curious grcup of batrachian,
(frog-like) reptiles which retain their gills through the
whole of life ; and one of the oval blood-discs of the
Proteus, being more than thirty times as long and
seventeen times as broad. as those of the musk-deer,
would cover no fewer than 500 of them. According
to the recent estimate of Vierordt, a cubic inch of
human blood contains upwards of -eighty millions of
red corpuscles, and near a quarter of a million of the
white."

A small drop of blood should be placed on a glass
slide, and carefully protected by a thin glass cover,
taking care to exclude air-bubbles ; the red corpuscles
will be seen, many adhering together like rolls of

98 THE MICROSCOPE.

coins ; by gently moving the glass together you will
cause them to separate and to roll over. The blood-
discs of mammals are entirely destitute of the granular
nucleus spoken of above. The discs of the blood-
corpuscles of the mammalia are double-concave in
form, and the dark spot in the centre is merely an
effect of refraction, for by adding a little water to
them, they gradually become flat and then double-
convex, the dark spot disappearing. They can be
made to assume the concave form again by treating
them with fluids of greater density than their own
contents.

The white corpuscles are much fewer in number
than the red, usually not more than as i to 350 ; they
are for the most part globular in form, though subject
to much variation.

In a medico-legal point of view, it is obvious that a
knowledge of the shape and relative sizes of the red
corpuscles might be of great use. Suppose, for instance,
that a man was brought before the magistrates on a
charge of murder ; certain marks of blood are found
upon his clothes. He insists, it may be, that they are
blood-stains of some bird, say a pheasant. The
microscope shows the form of the corpuscles to be
circular ; clearly, then, the stains in question are not
those of any bird, which has oval corpuscles. Intimate
acquaintance with the forms of the blood-discs of
many animals would decide the animal from which
they came.

The microscope has been much used in the exami-
nation of articles of food and medicine, and has re-
vealed the existence of a great deal ot fraudulent
practices on the part of unscrupulous tradesmen, who
are in the habit of adulterating different productions.
" The happy application of the microscope," says Dr.
Hassall (" Adulterations Detected in Food and Medi-

THE MICROSCOPE IN PHYSIOLOGY. 99

cine "), " to the subject of adulteration, has furnished
the means of detecting a host of adulterations, the
discovery of which had before, for the most part,
been considered to be impossible." By means of the
microscope, the various forms of cellular and other
tissue, starch granules, woody fibres, spiral vessels, &c.
&c.,are revealed; as the various substances have their
distinctive characteristic forms, a mixture of one or
more substances with what is sold as a pure and
unadulterated substance, becomes evident. The fol
lowing remarks of Dr. Hassall, one of our highest
authorities on food adulteration, will be read with
interest : —

"When we survey with our unaided vision any
animal or plant, we detect a variety of evidences of
organisation or structure ; but there is in every part
of every animal or vegetable production an extra-
ordinary amount of organisation wholly invisible to
the unarmed sight, and which is revealed only to the
powers of the microscope. Now this minute and
microscopical organisation is different in different parts
of the same animal or plant, and different in different
animals and plants, so that by means of these
differences, rightly understood, the experienced micro-
scopical observer is enabled to identify in many cases
infinitely minute portions of animal or vegetable tissues,
and to refer them to the parts or species to which they
belong.

" Thus by means ot the microscope, one kind of
root, stem, or leaf may generally be distinguished from
another ; one kind of starch or flour from another ; one
seed from another, and so on. In this way, the micro-
scope becomes an invaluable and indispensable aid
in the discovery of adulteration.

" Applying the microscope to food, it appears that
there is scarcely a vegetable article of consumption,

G 2

100 THE MICROSCOPE.

not a liquid, which may not be distinguished by means
of that instrument. Further, that all those adultera-
tions of these articles which consist in the addition
of other vegetable substances, and which constitute by
far the majority of adulterations practised, may like-
wise be discovered and discriminated by the same
means.

"The same remarks apply to all the vegetable
drugs, whether roots, barks, seeds, or leaves. We are
not acquainted with one such drug which may not be
thus distinguished.

"The seeds even belonging to different species of the
same genus may frequently be distinguished from each
other by the microscope— a point in some cases of very
great importance. A remarkable instance of this has
fallen under our observation. The seeds of the dif-
ferent species of mustard, rape, &c., may all be distin-
guished under the microscope by differences in their
organisation. To show the importance of the dis-
crimination in some cases, the following instance may
be cited. Some cattle were fed with rape-cake, and
died with symptoms of inflammation of the stomach
and bowels. Nothing of a poisonous nature could
be detected on analysis ; but it was suspected that the
cake might be adulterated with mustard-husk, al-
though even this point could not be clearly established
by chemical research. Under these circumstances
the cake was sent to the author for examination, who
had but little difficulty in ascertaining that it was
adulterated with mustard-seed, which, from the large
quantity consumed, was doubtless the cause of the
fatal inflammation. Not only can the seeds of dif-
ferent plants of the same genus be frequently discrimi-
nated by the microscope, but in some cases those
belonging even to mere varieties of species. Tne
microscope in some cases can even inform us of the

THE MICROSCOPE IN PHYSIOLOGY. IOI

piocesses or agents to which certain vegetable sub-
stances have been subjected. Illustrations of this are
afforded by the starches of wheat and barley ; it can be
determined by the microscope whether these are raw,
baked or boiled, or whether malted or unmalted."*

Cocoa adulterated with Potato Starch.

This figure shows a sample of cocoa adulterated with
potato-flower ; at a you will notice the starch-granules,
cells, and spiral vessels of cocoa ; at b you will see
the large characteristic granules of potato-starch.

Milk is a substance very frequently adulterated.
" If the testimony of ordinary observers, and even of
many scientific writers, is to be credited, there are few

* "Adulterations Detected in Food and Medicine," pp. 44, 45.

102

THE MICROSCOPE.

articles of food more liable to adulteration — and this
of the grossest description — than milk." In a sample
of good milk shown below you will observe myriads
of beautifully-formed globules of fatty matter, of
various size, and reflecting the light strongly. Some-

Milk, showing fat-globules (a) and pus corpuscles (b).

times the milk is rendered unwholesome from the
presence of a number of pus corpuscles, as in the
figure ; where the fat-globules are few, the milk is
poor or deficient in cream, representing the state
known popularly known as " skim milk."

" The most prevalent and important adulteration of

THE MICROSCOPE IN PHYSIOLOGY. 103

milk is that with water. Now, some few persons who
have not reflected closely upon the matter, may be
disposed to make light of the adulteration of milk with
water, and to speak in rather facetious terms of the
cow with the iron tail ; but it is surely no light matter
to rob an important article of daily consumption, like
milk, of a large portion of its nutritious constituents.
But the adulteration with water is not the only adul-
teration to which milk is liable ; the large addition of
water frequently made to it so alters its appearance as
to cause it to assume the sky-blue colour so familiar to
us in our school-boy days, and so reduces its flavour
that it becomes necessary to have recourse to other
adulterating ingredients — namely, treacle, to sweeten it,
salt, to bring out the flavour, and annatto, to colour it.
Further, there is no question but that chalk, cerebral
matter •, and starch have been, and are occasionally,
though rarely, employed in the adulteration of milk.
With regard to the use of chalk, a manufacturer of pre-
served milk recently informed us that it sometimes
happened to him to find carbonate of lime or chalk at
the bottom of the evaporating dishes or pans on the
evaporation of large quantities ot London milk."

These remarks will be sufficient to show you the
use of the microscope in the detection of adulteration
in food. Dr. Hassall's book will supply you with
abundance of information on the subject, should your
microscopic predilections point that way.

It is very curious to see the formation of crystals
taking place under the microscope. If you evaporate
a solution ot common salt on a glass slide, and allow
it to cool, and then cover it with a bit of thin glass,
you will see some beautitul cubes of chloride of sodium.
In the same simple way you may obtain crystals of
several salts for examination. On the other side are
represented forms of the crystals of ammonio-phosphate

104

THE MICROSCOPE.

of magnesia, the prismatic form* of which are extremely
beautiful when viewed with the polariscope (a). The
other forms depicted are those of oxalate of lime,
which, it will be seen, assume various shapes (b). When

occurring in the cells of plants these crystals are fre-
quently deposited in a needle-shaped form (raphides),
or they may be rectangular or rhombic prisms with
pyramidal ends, often forming groups radiating from
a centre. The formation of the crystals of silver is a
beautiful thing to see. Place a solution of nitrate of

THE MICROSCOPE IN GEOLOGY. 105

silver on a glass slide, drop a few copper filings upon
it ; a brilliant arborescent form of crystallisation takes
place, growing rapidly as you look at it. This is an
interesting case of affinity. The nitric acid imme-
diately combines with the copper, and the silver
appears in the metallic state.

CHAPTER X.

THE MICROSCOPE IN GEOLOGY.

THE geological student will gather a vast amount of
information by means of the microscope. He will be
able to determine the nature of the minute animal and
vegetable remains that are found in various strata ot
the earth's crust, as well as the composition of many
of the strata themselves. Huge mountains have been
shown, by the aid of the microscope, to be composed
of countless millions of minute organisms, such as
Diatomacecz, Foraminifera, &c. " Startling and almost
incredible as the assertion may appear to some," as
Mr. Hogg truly observes, " it is none the less a fact
established beyond all question by the aid of the
microscope, that some of our most gigantic mountain
ranges, such as the mighty Andes, towering into space
25,250 feet above the. level of the sea, their base occu-
pying so vast an area of land, as also our massive
limestone rocks, the sand that covers our boundless
deserts, and the soil of many of our wide extended
plains, are principally composed of portions of in-
visible animalcules. And, as Dr. Buckland truly
observes, ' The remains of such minute animals have
added much more to the mass of materials which com-
pose the exterior crust of the globe than the bones of
elephants, hippopotami, and whales/ " In some cases

io6

THE MICROSCOPE.

these remains consist for the most part of the siliceous
shells of the Diatomaceae, at one time supposed to be
of animal origin, but now of undoubted vegetable
nature ; in other cases, enormous deposits are found
to consist principally of the shells of the Foraminifera,
minute animals of low organisation. Chalk hills are

Forms of Diatomaceae.

formed almost entirely of the remains of these little
creatures, whose shells are often of most exquisite
forms. Ehrenberg has computed that a cubic inch
of chalk may contain the remains of a million
of these creatures. "The Paris basin, 180 miles
long and averaging 90 in breadth, abounds in in-
fusoria and other siliceous remains. Ehrenberg, on
examining the immense deposit of mud at the har-
bour of Wismar, Mecklenburg-Schwerin, found one-

THE MICROSCOPE IN GEOLOGY. IOJ

tenth to consist of the shells of infusoria, giving a
mass of animal remains amounting to 22,885 cubic
feet in bulk, and weighing forty tons, as the quantity
annually deposited there. How vast, how utterly in-
comprehensible, then, must be the number of once
living beings, whose remains have in the lapse of time
accumulated." Richmond, in Virginia, is built upon
a stratum, the so-called " infusorial earth," which is
eighteen feet thick, and extends over a wide area ;
this is found to consist principally of the siliceous
shells of Diatomaceae.

The mountain meal (bergh-mehl) of Norway, Lap-
land, Saxony, sometimes forming a stratum nearly
thirty feet thick, is similarly composed. Most of these
deposits consist of marine forms of Diatomaceae, but
in our own islands, as at Dolgelly in North Wales,
Mourne Mountain in Ireland, Mull in Scotland, depo-
sits of fresh-water origin have apparently been formed.
In the Foraminifera the skeleton usually consists of a
many-chambered calcareous shell investing a jelly-like
body ; many of these are perforated with numerous
little apertures. In the Polycystina, an allied group of
the same rhizopod type of animal life, the investing
shell is perforated with very large apertures, and it is
siliceous ; " the apertures are often so large and nu-
merous that the solid portion of the shell forms little
more than a network, thus indicating a transition to
the succeeding group, the Porifera, or sponges. The
Polycystina possess wonderful beauty, and are capital
objects for the binocular microscope ; its stereoscopic
perfection, as Dr. Carpenter remarks, causing them
to be presented to the mind's eye in complete relief,
so as to bring out, with the most marvellous and
beautiful effect, all their delicate sculpture.

The Polycystina are probably as widely diffused
as the Foraminifera ; they have been brought up by

I08- THE MICROSCOPE.

the sounding-lead from the bottom of the Atlantic, at
depths of from 1,000 to 2,000 fathoms. We are told
that they were probably more abundant during the
later geological periods, having been detected by Pro-
fessor Ehrenberg in the chalks and marls of Sicily and
Greece, and of Oran, in Africa, and also in the
diatomaceous deposits of Bermuda, and Richmond
(Virginia).

" It is an admitted rule in geological science, that the
past history of the earth is to be interpreted, so far as
may be found possible, by the study of the changes
which are still going on. Thus when we meet with
an extensive stratum of fossilised Diatom acese in what
is now dry land, we can entertain no doubt that this
siliceous deposit originally accumulated either at the
bottom of a fresh-water lake, or beneath the waters of
' the ocean ; just as such deposits are formed at the pre-
sent time by the production and death of successive
generations of these bodies, whose indestructible casings
accumulate in the lapse of ages, so as to form layers
whose thickness is only limited by the time during which
this process has been in action. In like manner, when
we meet with a limestone rock entirely composed of
the calcareous shells of Foraminifera, some of them
entire, others broken up into minute particles, we
interpret the phenomenon by the fact that the dredg-
ings obtained from some parts of the ocean-bottom
consist almost entirely of existing Foraminifera, in
which entire shells, the animals of which may be yet
alive, are mingled with the debris of others that have
been reduced by the action of the waves to a frag-
mentary state. Now in the fine white mud which is
brought up from almost every part of the sea-bottom
of the Levant, where it forms a stratum that is con-
tinually undergoing a slow but steady increase in
thickness, the microscopic researches of Professor

THE MICROSCOPE IN GEOLOGY. 1 09

Williamson have shown that not only are there multi-
tudes of minute remains of living organisms, both
animal and vegetable, but that it is entirely, or almost
wholly, composed of such remains. Amongst these
were about twenty-six species of Diatomaceae (sili-
ceous), eight species of Foraminifera (calcareous), and
a miscellaneous group of objects, consisting of calca-
reous and siliceous spicules of sponges and Gorgoniae,
and ot fragments of the calcareous skeletons of echi-
noderms and mollusks. The deep-sea soundings which
have recently been obtained from various parts of the
ocean-bed afford results more or less similar; the variety
of form, however, usually showing a diminution as the
depth increases. From an extensive comparison of
the forms of recent Foraminifera brought up from dit-
ferent depths, Messrs. Parker and Rupert Jones con-
sider themselves able to predicate the range of depth
within which any particular collection may have been
taken ; and thus to determine, in the case of deposits
of fossil Foraminifera, within what range of depth they
were probably formed."*

Very interesting results have attended the various
deep-sea expeditions that have taken place the last
few years in different parts of the Atlantic. It has
been estimated that nearly two hundredweight of the
sea-bottom, revealing, contrary to preconceived notions,
a submarine life at a depth of more than 2,000 fathoms,
has been dredged up and examined. One of the
most curious questions relates to the deposits in the
deep water of the Atlantic, and their connection with
the Cretaceous period of geologists. For very many
years the origin of chalk has been a point of discus-
sion. If you will rub a bit of whiting in a drop ot"
water on a glass side, cover with thin glass, and use a

* Carpenter on the Microscope, p. 755.

HO THE MICROSCOPE.

power of 400 or 500 diameters, you will notice a great
quantity of rounded flattened bodies. Ehrenberg, I
believe, was the first person to observe and describe
these little particles. Formerly these bodies were sup-
posed to be mineral concretions of particles derived
from organic bodies. They were called crystalloids,
and are thus described in the " Micrographic Dic-
tionary," under the word chalk: "The cementing
material of chalk consists of very minute, numerous,
and remarkable bodies, called crystalloids; they are
elliptical, or rounded and flattened, from TOO^O to
a-gVo in length, the most numerous perhaps -^Q-Q.
Some of them consist of a simple ring ; in others it is
marked with pretty regular transverse lines, so as to
make it appear jointed; in others, again, there is a
thinner central portion, often exhibiting one or more
granules. M. Ehrenberg regards these as arising from
the disintegration of the microscopic organism forming
the chalk into much more minute calcareous particles,
and their reunion into regular elliptical plates (or
discs) by a peculiar process, differing essentially from
and coarser than that of crystallisation, but com-
parable with it ; one probably preceding all slow crys-
talline formation, and causing, but not alone, the
granular state of solid inorganic matter." Recent
investigations, however, afforded by the mud, or ooze,
obtained from the deep sea, have been supposed by
some to confirm the opinion, first, I believe, made
public by the Rev. J. B. Reade, that these so-called
crystalloids are organic. They are now known by
the name of coccoliths and coccospheres, and have
been found abundantly in the sticky mud of the
Atlantic sea-bed. These bodies, be they animal or
vegetable, are of extreme low organisation, and are
not confined to deep water, for Dr. Wallich has ob-
tained them off the coast of Plymouth at about seven-

THE MICROSCOPE IN GEOLOGY. I J I

teen fathoms. Whatever be their nature, whether
organic or not, it is certain that these bodies abound
in extraordinary numbers in chalk and in the ooze at
the bottom of the Atlantic, and seem to indicate a
similar origin and an essential identity of the chalk
with modern deep-sea mud. But besides these cocco-
liths and coccospheres so called, chalk contains other
bodies round in form, having many chambers in
communion with each other, of microscopic size and
beautiful construction. These calcareous bodies are
of various forms. Professor Huxley very aptly com-
pares one of the commonest to a badly-grown rasp-
berry, being formed of a number of nearly globular
chambers of different sizes congregated together. These
bodies have hence been called Globigerincz, and some
specimens of chalk consist of little else than Globi-
gerinae and the granular bodies already mentioned.
What a subject for contemplation have we here !
Immense chalk cliffs extending for hundreds of miles,
the vast fabric the work of minute creatures invisible
to the naked eye ! In England this chalk formation
extends diagonally from Lulworth, in Dorset, to Flam-
borough Head, in Yorkshire, a distance of over 280
miles "as the crow flies. In some places it is more
than a thousand feet thick. Nevertheless, as Pro-
fessor Huxley says, "it covers but an insignificant
portion of the whole area occupied by the chalk forma-
tion of the globe ;" for if all the points at which true
chalk occurs were circumscribed, they would lie within
an irregular oval about 3,000 miles in long diameter,
the area of which would be as great as that of Europe,
and would many times exceed that of the largest exist-
ing inland sea — the Mediterranean ; and all this wide-
spread component of the earth's surface consists for
the most part of the skeletons or calcareous shells of
Globigerinae ! But recent investigations have shown

112 THE MICROSCOPE.

that the chalk-forming process is even now going
on at the bottom of the North Atlantic Ocean
over an immense area, and this is brought about for
the most part by the same agencies as built up the
hills and deposits of the Cretaceous period. This
deep-sea mud is substantially chalk, and covers an
area of about 1,700 miles from east to west. " It is a
prodigious plain — one of the widest and most even
plains in the world. If the sea were drained off, you
might drive a wagon all the way from Valentia, on the
west coast of Ireland, to Trinity Bay, in Newfound-
land. And except upon one sharp incline about 200
miles from Valentia, I am not quite sure that it would
be necessary to put the skid on, so gentle are the
ascents and descents upon that long route. From
Valentia the road would lie down-hill for about 200
miles to the point at which the bottom is now covered
by 1,700 fathoms of sea-water. Then would come
the central plain, more than a thousand miles wide,
the inequalities of the surface of which would be
hardly perceptible, though the depth of water upon it
now varies from 10,000 to 15,000 feet; and there are
places in which Mont Blanc might be sunk without
showing its peak above the water. Beyond this, the
ascent on the American side commences, and gradually
leads, for about 300 miles, to the Newfoundland shore.
" Almost the whole of the bottom of this central plain
(which extends for many hundred miles in a north and
south direction) is covered by a fine mud, which, when
brought to the surface, dries into a greyish-white friable
substance. You can write with this on a blackboard
if you are so inclined, and to the eye it is quite like
very soft, greyish chalk. Examined chemically, it
proves to be composed almost wholly of carbonate of
lime ; and if you make a section of it, and view it with
the microscope, it presents innumerable Globigerinae

THE MICROSCOPE IN GEOLOGY. 113

embedded in a granular matrix."* These calcareous
shells, which belong to the Foraminiferous group, con-
tain living inhabitants ; at least, those which lie on the
surface layer of the ooze do, whilst deeper layers are
chiefly made up of the empty shells of Globigerinae.
The animal is "a mere particle of living jelly, without
defined parts of any kind, without a mouth, nerves,
muscles, or distinct organs, and only manifesting its
vitality to ordinary observation by thrusting out and
retracting, from all parts of its surface, long filamentous
processes which serve for arms and legs. Yet this
amorphous particle, devoid of everything which in the
higher animals we call organs, is capable of feeding,
growing, and multiplying ; of separating from the ocean
the small proportion of carbonate of lime which is
dissolved in sea-water ; and of building up that sub-
stance into a skeleton for itself, according to a pattern
which can be imitated by no other known agency."
And here I must guard you against Dr. Carpenter's
opinion, that the deposit of Globigerina-mud " has
been going on over some part or other of the North
Atlantic sea-bed from the Cretaceous epoch to the pre-
sent time — as there is much reason to think that it did
elsewhere in anterior geological periods — this mud
being not merely a chalk formation, but a continuation
of the chalk formation, so that we may be said to be
still living in the Cretaceous period" — an idea which,
to use Sir Charles Lyell's words, is as inadmissible in a
geographical as a geological sense. You are doubt-
less familiar with those flinty nodules so extremely
abundant in the chalk formation ; you are certainly
familiar with that common, but very interesting article,
a sponge. What connection has the framework of the
softest of animals with one of the hardest of stones ?
The microscope reveals the fact that flint contains

* Huxley's " Lay Sermons," &c. — " On a Piece of Chalk."

H

114 THE MICROSCOPE.

the remains of sponges, for it is not uncommon to
find the external forms and markings characteristic
of their organisms preserved, whilst thin sections of
flint show a spongeous texture in the interior. Fora-
miniferal shells, and bodies termed Xanthidia^ with
their long spinous projections (the sporangia of Des-
midiaceae), are often found embedded in flint. The
siliceous spicules of sponges are also found in jaspers
and agates. The pretty little round concretions of the
Oolitic formation, so conspicuous in Bath stone, have
been formed concentrically round a nucleus which is
often a foraminiferal shell. The green sands which
occur in various deposits from the Silurian to the
Tertiary period, and which, when occurring beneath
the chalk, are known as the Greensand formation,
have been shown by the microscope to consist of the
siliceous casts, coloured by silicate of iron, of fora-
miniferal shells, or those of minute Mollusca. I must
not forget to mention the discovery in late years, by
Dr. Carpenter, of the nature of the serpentine limestone
in the Laurentian formations of Canada. This deposit
consists of a regular series of stratified rocks, and
underlies the equivalents, not merely of the Silurian,
but also of the Upper and Lower Cambrian systems
of this country. We are told that these rocks spread
over an area of 200,000 square miles, and that they
are composed of a species of foraminiferal shell called
Eozoon Canadense. "The geological position of this
fossil, indicating the vast remoteness in time of its exist-
ence as a living organism, is scarcely more remarkable
than its zoological relations ; for at what (so far as we
at present know) was the dawn of animal life upon
our globe, it affords evidence of a most extraordinary
development of that rhizopod type of animal life,
which now presents itself only in forms of compara-
tive insignificance, a development which enabled it to
separate carbonate of lime from the ocean-waters, in

THE MICROSCOPE IN GEOLOGY. 11$

quantity sufficient to produce masses rivalling in bulk
and solidity those of the stony corals ot later epochs,
and thus to turnish (as there seems good reason to
believe) the materials of those calcareous strata, ot
whose occurrence in the Laurentian series it had pre-
viously been impossible to give a satisfactory account."*
Wonderful, truly, it is to reflect that such enormous
results are brought about by the operations of an
animal of such extreme simplicity. These rhizopods
seem to have performed in the seas ot the Laurentian
epoch the same part in the production of limestone
rocks which was subsequently taken by coral polypes,
echinoderms, and mollusks, as well as by minuter
forms of Foraminifera ; " and it is a fact not without
an important significance/' Dr. Carpenter also remarks,
" that this the lowest type of animal life known to the
physiologist, should have thus culminated in the very
earliest period in the history of the life of our gldfoe
with which the palaeontologist is at present acquainted.
. , . . . The physiologist has here a case in which
those vital operations which he is accustomed to see
carried on by an elaborate apparatus, are performed
without any special instruments whatever — a little
particle of apparently homogeneous jelly, changing
itself into a greater variety of forms than the fabled
Proteus, laying hold of its food without members,
swallowing it without a mouth, digesting it ^ without a
stomach, appropriating its nutritious material without
absorbent vessels or a circulating system, moving its
parts without muscles, feeling (if it has any power to
do so) without nerves, propagating itself without a
genital apparatus, and forming a shelly covering that
possesses a symmetry and complexity not surpassed by
those of any testaceous animals. "t

* Dr. Carpenter in Intellectual Observer, vii. 278.
^ Introduction to the Study of the Foraminifera. Ray Society,
p. vii.

R 2

CHAPTER XI.

THE MICROSCOPE IN GEOLOGY (continued).

IT has long been suspected that the extremely useful
substance called coal is nothing else than a con-
solidated mass of decomposed vegetable matter ; it
is not, indeed, uncommon to find certain markings or
indications of a vegetable origin in a lump of coal,
and the microscope has enabled us to determine the
nature of that vegetation by revealing its structure.
It shows us that the coal vegetation was in a great
measure coniferous in its nature, "that it probably
approximated most nearly to that group of existing
Coniferae to which the Araucaria belong." It is one
characteristic of coniferous wood to exhibit a number
of glandular dots on the woody fibres ; now these
glandular dots are often to be seen in sections of coal.
Owing to the extreme friability of coal, its examination
is attended with some difficulty, for it is no easy
.matter to reduce slices to the necessary degree of
tenuity. The following mode of examining the
structure of coal is taken from the " Micrographic
Dictionary:" — "The coal is macerated for about a
week in a solution of carbonate of potash ; at the end
of that time it is possible to cut tolerably thin slices
with a razor. These slices are then placed in a watch-
glass with strong nitric acid, covered, and gently
heated ; they soon turn brownish, then yellow, when
the process must be arrested by dipping the whole
into a saucer of cold water, or else the coal would
be dissolved. The slices thus treated appear of a
darkish amber colour, very transparent, and exhibit
the structure when existing most clearly. The speci-

THE MICROSCOPE IN GEOLOGY. 117

mens are best preserved in glycerine, in cells ; we find
that spirits render them opaque, and even Canada
balsam has the same effect."

Mr. David Forbes, in a very interesting paper —
"The Microscope in Geology" — in the Popular Science
Review for October, 1867, has shown how much may
be learnt of the mineral composition of rocks by a
careful and patient use of the microscope. Previous
to Mr. David Forbes' application of the microscope
to determine the composition of rocks, very little
appears to have been done, with the exception of Mr.
Sorby's memoirs on such special points of inquiry.
Mr. David Forbes' collection of sections of rocks and
their constituent minerals were, for the most part,
made by himself; it amounted, in 1867, to upwards of
2,000, and represents a wide geographical distribution.
" As long as the geologist encounters in the field any
rocks of so coarse or simple a structure as to admit
of their being resolved by the naked eye into their
constituent mineral species, or of distinguishing the
fragments of previously existing rocks, of which they
may have been built up, he may speculate with a fair
chance of success as to their probable origin or mode
of formation. When, however, as is often more the
rule than the exception, rocks are everywhere met
with presenting so fine-grained and apparently homo-
geneous a texture as to defy such attempts at ocular
analysis, all speculations as to their nature and for-
mation, based merely upon observation in the field,
can but be compared to groping in the dark, with the
faint hope of stumbling upon the truth.

" In these cases the geologist must call in the aid of
chemistry and the microscope ; by chemical analysis
he learns the per-centage composition of the rock in
question, and the microscopic examination informs
him how the chemical elements are mineralogically

Il8 THE MICROSCOPE.

combined, and at the same time affords valuable in-
formation as to the physical structure and arrangement
of the components of the rock mass, tending to
elucidate its formation and origin." Let me select
one or two instances out of several given by Mr.
D. Forbes. You are, perhaps, acquainted with the
mineral termed Obsidian, or Volcanic glass, which is
produced by the fusion of felspathic rocks or those
which contain alkaline silicates. The glassy appear-
ance testifying to an apparently complete vitreous
condition would, at first sight, defy all attempts to
discover the structure ; nevertheless, some part of the
mass will be found to be sufficiently devitrified to
allow of its structure and mineral composition being
recognised, and Mr. D. Forbes has figured a very
pretty section of obsidian in which the pyroscenic and
felspathic constituents of the rock are very clearly
apparent. Rocks, according to their structure, fall
naturally into one or other of two great classes — (i)
Primary, or Eruptive; and (2) Secondary, or Sedi-
mentary. Now, in some cases it is impossible to
determine by mere ocular inspection to which of
these classes a certain rock may belong. Microscopic
examination shows that whatever be the geological
age of these primary rocks, or from whatever part of
the earth's surface they may be taken, they " possess
certain general and definite structural characters dis-
tinguishing them at once from all other rocks."

There occurs, either found embedded in or breaking
through the coal-measures of Staffordshire, a rock
popularly termed " White Horse," from often having
the appearance of a whitish clay ; the coal-measures
at points of contact with the rock are frequently burnt
and altered. " The origin of this rock, whether sedi-
mentary or igneous, was disputed until the more
recent geological and chemical examinations of it

THE MICROSCOPE IN GEOLOGY. 1 1 9

have proved satisfactorily its identity with the Rowley
basaltic rock." In external appearance, the mineral
uralite resembles augite, but its chemical composition
is that of hornblende ; the microscope distinctly re-
veals the fibrous structure characteristic of the horn-
blende.

Some years ago, you may remember, a geological
heresy was maintained by some, that granite had not,
after all that had been said, an igneous origin. Let
us see what part the microscope played in determin-
ing the question. Mr. Sorby discovered in the quartz
of granites numerous minute fluid cavities, thus show-
ing that granites have solidified at a heat far below
the fusing points of their constituent minerals, and at
such a pressure as to enable it to entangle and retain
a small amount of aqueous vapour, which naturally
must have been present during its liquefaction.
" The presence of these fluid cavities in the quartz of
granite was immediately blazoned forth as proof posi-
tive of the non-igneous origin of granite ; whereas, if
Mr. Sorby' s memoir had actually been read, it would
have been seen that he had found fluid cavities per-
fectly identical with those of granite, not only in the
quartz of volcanic rocks, but also in the felspar and
nepheline ejected from the crater of Vesuvius; and
that the presence of fluid, vapour, gas, and stone cavK
ties are common both to the volcanic quartz-trachytes
and to the oldest granites ; and the inference drawn
by Mr. Sorby from the results of his researches, is
that both these rocks were formed by identical agen-
cies." As with regard to- the volcanic, so with the
sedimentary rocks ; a microscopic examination alone
will afford correct information as to their origin; but I
must refer you to Mr. David Forbes' most interesting -
memoir for further details. Mr. D. Forbes gives
the following instructions how to prepare rock sec-

120 THE MICROSCOPE.

tions : — "A fragment, from one quarter to three-
quarters of an inch square, and of convenient thick-
ness, is chipped off the rock specimen in the direc-
tion of the required section, and ground down upon
an iron or pewter plate in a lapidary's lathe, with
emery, until a perfectly flat surface is obtained. This
surface is then worked down still finer by hand on a
slab of black marble, with less coarse emery; then
upon a Water of Ayr stone, with water alone, and lastly
finished by hand with water on a slab of black marble.
By these means the surface acquires a sufficient
polish, without being contaminated with rouge or
other polishing-powder or oil, as is sometimes the case
with purchased sections of rocks. This side of the
rock is now cemented by Canada balsam on to a small
piece of plate glass,, about i| in. square, and fin.
thick, which serves as a handle when grinding the
other side on the emery plate as before. This grind-
ing is continued until the section is so thin as to be
in danger of breaking up from the roughness of the
motion, upon which it is completed, by further grind-
ing with emery by hand on marble, and finished first
upon Water of Ayr stone with water, and afterwards
upon black marble, as before described. The section
is now removed from the plate glass, and mounted in
Canada balsam on a slide, covering its upper surface
with a thin glass as usual/'

By the aid of the microscope the geological investi-
gator is able to ascertain the nature, and even to con-
struct the entire form of an animal long ago extinct,
by the examination of minute parts that have been
preserved in the tomb of the earth. Fossil corals,
fragments of the shells or spines of Echinodermata,
and of such molluscous shells as present distinct ap-
pearances of structure, may be identified by its
means. A knowledge of the structure of teeth,

THE MICROSCOPE IN GEOLOGY. 121

bones, the dermal skeleton of vertebrate animals, will
enable the microscopist to name the animal to which
the parts belonged. You are, of course, aware that
the different strata are more or less characterised by
the organic remains which they contain. In some
cases the strata may be so similar in composition, that
it is impossible to determine its position on the geo-
logical chart in the absence of organic remains. Many
thousand pounds would have been saved to the
pockets of certain land proprietors had they con-
sulted the geologist or microscopist before they sank
shafts for coal in beds which could not possibly con-
tain any. Extending over many parts of Russia, there
occurs a certain rock formation, whose mineral cha-
racters might justify its being likened either to the
Old or New Red Sandstone of this country, and whose
position relatively to other strata is such, that there is
great difficulty in obtaining evidence from the usual
sources as to its place in the series. The nature of
this formation could be determined by the organic
remains which it might yield, but in this case they
were few and fragmentary, and consisted chiefly of
teeth which were seldom found entire. It was at first
supposed from the great size of these teeth, that they
belonged to Saurian reptiles ; hence the formation
must have been considered New Red. External form
may be deceptive ; so recourse was had to a micro-
scopic section of the tooth, the result of which was to
show that it belonged to an undoubted fish, called,
from the dendritic disposition of the tissues, by the
name of Dendrodus. This decided the all-important
point, for as the genus Dendrodus is exclusively
Palaeozoic, the rock in question belonged not to the
New, but to the Old Red formation ; therefore there
would be no possibility of finding coal in it.

You will be interested in another similar case. The

122 THE MICROSCOPE.

identity of the Keuper Sandstein of Wirtemburg, with
the New Red Sandstone of Warwickshire, has been
satisfactorily demonstrated by means of the micro-
scope. Some years ago, Professor Jaeger found in
the German Keuper formation some remarkable fossil
teeth, which were of great size, conical or canine in
form, and distinctly striated. In 1840 Professor
Owen found similar teeth in the New Red Sandstone
of Coton End quarry, Warwickshire. What was the
nature of the animal to which these teeth belonged ?
From external characters it had at first been inferred
that the teeth were those of some Saurian reptile ; but
the results of a microscopic examination of the teeth,
both from the German Keuper and the New Red Sand-
stone of Warwickshire, revealed a very remarkable
and complicated structure; hence, provisionally, the
creature to which the teeth were supposed to belong
was named Labyrinthodon, by Professor Owen ; but
this peculiar internal structure of the tooth — a structure
formed by "the convergence of numerous inflected
folds of the external layer of cement towards the
pulp cavity" — is typically presented also in the teeth
of fish-lizards and lizard-like fish ; hence it might be
reasonably inferred that the labyrinthodon would
combine with its reptilian characters an affinity with
fish. The subsequent discovery of some of the bones
of the labyrinthodon, as the vertebrae, jaws, hume-
rus, femur, and toes, &c., have gone far to establish
this inference ; and there is much reason to believe
that that strange creature, the labyrinthodon, was a
gigantic frog-like animal five or six feet long, with a
mixture of fish and crocodilian characters, and that in
all probability it was identical with the animal whose
footprints have been discovered in the quarries of the
grey quartzose and red sandstone of Saxony, and in
the sandstone quarries of Stourton, in Cheshire.

CHAPTER XII.

THE COLLECTION AND MOUNTING OF OBJECTS — TEST-
FLUIDS.

THERE is little need that I should say much on the
collection of objects you may wish to examine ; a
little experience will prove the best instructor. If
you wish to collect Desmidiacese and Diatomaceae,
you should take with you two or three wide-mouthed
bottles with corks, a tin scoop, a sharp hook for cut-
ting off stems of aquatic plants, which are often covered
with minute vegetable organisms (these two last should
be made to screw on to a long light bamboo rod),
and a lens. The Desmidiacese occur in slow-running
rivers, pools, ditches, especially those on boggy moors.
They often form a greenish cloud on the stems and
leaves of water-plants, or on the ground. They may
be taken up from the ground by the scoop, or from
the stems of plants by your fingers. If placed in
bottles and exposed to the light, these vegetable forms
will grow, and you may employ your time advan-
tageously in studying the development. Diatomaceae
are also found in profusion on the stems and leaves
of aquatic plants, presenting themselves as coloured
fringes, or forming a covering to stones or rocks in
cushion-like tufts, or spread over their surface as
delicate velvet, or depositing themselves as a filmy
stratum on the mud, or intermixed with the scum of
living or decayed vegetation on the surface of the
water. They are often mixed with sand and mud;
and the best way to get rid of these impurities is to
place the lot in a saucer of water, and expose it to the
light, when the diatoms may be skimmed from the
surface. Various beautiful forms occur upon sea*

124 THE MICROSCOPE.

weeds, and on the mud at the bottom of the sea.
You may also procure numerous forms from the
stomach of various sea-creatures, such as oysters,
sea-cucumbers, sea-squirts, soles, and other flat-fish.
It is a distinctive character of this group to have
encircling their various forms an external coat of silex,
which would appear to be almost indestructible. We
have seen how an accumulation of them give rise to
deposits of considerable thickness ; and guano, it is
well known, contains many forms, some of extreme
beauty. If you wish to collect Diatomacese from
guano, you should wash a portion several times in
water, and stir it well ; then let it rest for some hours,
so as to give the lighter forms time to sink; then
pour off the water, and if necessary give the sediment
another washing. You must now use strong acids;
the deposit is to be placed in a test-tube with hydro-
chloric acid, and gently heated. After the sediment
has subsided, pour off the acid, and heat it with a
fresh dose ; pour off again, and heat with nitric acid
two or three times, and apply heat for three or
four hours of about 200°; then wash the sediment
till the acid is removed. "The separation of siliceous
sand, and the subdivision of the entire aggregate of
diatoms into the larger and the finer kinds, may be
accomplished by stirring the sediment in a tall jar of
water, and then, while it is still in motion, pouring oft
the supernatant fluid as soon as the coarser particles
have subsided ; this fluid should be set aside, and as
soon as a finer sediment has subsided, it should again
be poured off; and this process may be repeated
three or four times at increasing intervals, until no
further sediment subsides after the lapse of half an
hour. The first sediment will probably contain all
the sandy particles, with perhaps some of the largest
diatoms, which may be picked out from among them ;

TEST- FLUIDS. 125

and the subsequent sediments will consist almost ex-
clusively of diatoms, the sizes of which will be so
graduated that the earliest sediments may be ex-
amined with the low powers, the next with the medium
powers, while the latest will require the higher powers
— a separation which is attended with great conve-
nience/'* small portions of the sediment should then
be mounted in Canada balsam, or set up dry between
two pieces of thin glass. For mounting microscopic
objects you will require a pair of fine-pointed forceps
for holding the objects to be mounted, a pair of stout
needles fixed in handles, a spring dipt for holding
down the covers whilst the balsam is cooling, and a
small spirit-lamp.

Canada balsam — a natural combination of resin
with the essential oil of turpentine — may be procured
from any druggist It is thick and viscid, but becomes
softer on the application of heat ; you must be careful
to keep it very clean and to exclude the air, which
would render it too thick for immediate use. To
mount in Canada balsam, place a drop on the glass
slide by means of a glass rod, then apply gentle heat,
immerse the object in it, and if there are no air-
bubbles, place the glass cover on, apply the spring
clip, and set aside for the balsam to harden. You will,
however, have need to exercise much patience ; for
no sooner is the object placed in the balsam than all
at once many air-bubbles make their unwelcome ap-
pearance ; you must, therefore, boil the balsam over
the spirit-lamp, if the texture of your object will allow
you to do so, and the heat will probably drive out the
intruding bubbles. It is advisable to prepare some
objects before mounting in Canada balsam by soak-
ing in oil of turpentine for some minutes. Insect

* Carpenter, page 315.

Sold by Messrs. Baker, Mr. Collins, and others.

126 THE MICROSCOPE.

structures, Foraminifera, &c., may be thus treated;
the oil of turpentine entering into the cavities or
tissues, excludes the air.

Spirit and distilled water form an excellent medium
for preserving animal tissu'es; one part of alcohol,
60 over proof, to five parts of distilled water, will
t>e found of sufficient strength for preserving many
substances. Methylated alcohol, which pays no duty,
answers very well, and it may be obtained at the
price of five shillings and sixpence per gallon. A drop
of this dilute alcohol is to be placed, by means of a
glass rod, on the glass slide, the tissue is to be sunk
into it, and covered with thin glass ; care must be
taken to exclude air-bubbles, the superfluous fluid
drained off, and the edge of the glass cover and ad-
jacent portion of the slide wiped quite dry. A ring
of cement — gold size may be especially recommended
— is to be laid round the edge of the thin glass, so as
to fix the cover on the slide. After this coating has
hardened, apply a second and a third.

A solution ot glycerine with camphor-water is another
valuable fluid for preserving structures. Price's gly-
cerine is superior to any other for microscopic pur-
poses. The proportion of glycerine and camphor-
water will depend on the nature of the object to be
mounted ; for general purposes, one part of glycerine
to two parts of camphor-water will be found useful.
There are various other preservative fluids and cements
which are very useful in microscopic work, but those
I have named will be sufficient for most practical
purposes.

Test-liquids are of immense use to the microscopist ;
they are employed to remove certain substances which
he wishes to get rid of, or to detect the presence of
particular substances in the object under examination.
For instance, suppose I wish to obtain the animal

TEST-FLUIDS. 127

basis of a bone or shell, I must dissolve the calcareous
portions by means of a mixture of hydrochloric and
nitric acid ; if I wish to get rid of the organic matter
in sponges, so as to obtain the mineral portion in a
separate state, I can do so by boiling the objects in
a solution of caustic potash; if it is desirable to
harden animal tissues, this can be done by maceration
in strong alcohol, or in a solution of chromic acid,
"so dilute as to be of a pale straw colour, which
is particularly efficacious in bringing into view the
finer ramification of nerves." If, on the other hand,
I wish to detect the presence of some particular sub-
stance in the object I am examining — say of starch
granules — I apply a solution of iodine in water (i gr.
of iodine, 3 grs. of iodide of potassium, i oz. of
distilled water), and the starch is turned blue; if
albuminous substance is present, the test gives it an
intense brown. Acid nitrate of mercury colours
albuminous substances red. A solution of caustic
potash or soda, by means of its solvent power, is ex-
tremely useful in rendering animal and vegetable
structures transparent. If you wish to clean any glass
slides or covers, and to get rid of the Canada balsam
or cement, you can readily do by means of spirits
of turpentine.

I shall conclude this very imperfect sketch of some
of the marvels of the microscope by quoting some
very valuable words of advice of an eminent micro-
scopist, Dr. Lionel S. Beale, F.R.S. :—

" No one engaged in the pursuit of any branch of
natural science is more tempted to be led into too
hasty generalisation than the microscopic observer.
It is his duty, therefore, to avoid drawing inferences
until he has accumulated a vast number of facts to
support the conclusions at which he has arrived. True
generalisations and correct inferences promote the

128 THE MICROSCOPE.

rapid advancement of scientific knowledge, for each
new inference may form the starting-point of a fresh
line of investigation ; but, on the other hand, every
false statement, regarded as an observed fact, forms
a terrible barrier to onward progress, since, before
the slightest useful advance can be made, it is neces-
sary to retrace our steps, it may be for a long way,
before we can hope to recommence our onward course.
Again, a much greater amount of evidence is always
required to overthrow a false conclusion than is
sufficient to propagate the original mistake, and
there can be no task more unsatisfactory than that
of being called upon to controvert the opinions and
deductions. of others. Years must be passed in patient
investigation before a man can expect to be able to
trust himself as an observer of facts, and it is only by
careful and unremitting exercise that he will gradually
acquire habits of attentive observation and the power
of thoughtful discrimination, which can alone render
his conclusions reliable. Indeed, though he labour
hard and earnestly, he will scarcely have properly
educated himself ere his powers begin to decay, and
he become liable to err from the natural deterioration
in structure of the organs upon which the observation
of his facts entirely depends."

* "How to Work with the Microscope," Fourth Edition, pp.
i33, 189.

INDEX.

^Ethalium septicum .
Algse ......

Anacharis alsinastrum
Anchusa paniculata .
Animalcules

PAGE

• 39

• 35

. 22
. 22
40

Anthomyia betae, Eggs of 81
Apparatus for Microscope 13

Bats, Hairs of .... 87
Bell-flower Animalcules . 42
Blood, Circulation of . . 56
Bone, Structure of . . . 89
Butterfly, Eggs of . . 8 1, 83

Cactus, Raphides in . . 22

Camera Lucida .... 1 1
Canada Balsam . . .125

Carchesium .... 43

Cells, Vegetable ... 17

Chalk 109

Chara nitella .... 22

Cilia ....... 41

Circulation in Plants . . 22

Coal 116

Collecting Apparatus . . 123

Condensing Lens ... 1 1

Corpuscles of Blood . . 97

Cricket, Drum and File of 73

Crystals 104

Cutis vera 92

Cynipidse 80

Deep-sea Soundings . . 109

Dendrodus 121

Dermestes, Hairs of . . 88

Desmidiaceae .... 35

PAGE

Deutzia, Hairs of . . . 26
Diatomaceae . . .35, 105
Difference between Animal
and Plant .... 38

Eel, Scales of .... 86

Eggs of Insects .... 82

Eozoon Canadense . . 14

Epipactis 31

Epistylis 43

Equisetum, Spores of . 34

Eyes of Insects ... 60

Fat-cells in Human Skin. 92
Ferns, Spores of ... 33

Flea 69

Floscularia 48

Fly, Foot of .... 74
Food, Adulterations in . 98
Foot of Frog, Circulation

of Blood in ... 58
Foraminifera . . . .109
Fossil Diatomaceae . .105

Fucus 32

Fungus 33

Glass Covers .... 13
Globigerinae . . . .ill
Gnat, Head of .... 67
Grew, Researches of . . 6

Hairs, Structure of , . 86, 87
Halteres, Functions of . 73
Hind-foot of Bee ... 79
Hydra ..... 49

Hymenoptera, Stings of . 80
I

130

INDEX.

p
Illumination of Objects .

AGE

II

40

122

12
122
6

6
25

45

8
14

117

39

"5

62

95

81

10

123

121

40
30

93
94

12

28
107

39

p
Quekett on Artificial Pro-
duction of Raphldes .

AGE

23
22

122

44

85
83
84
27
80
93
24
80

"3

4i
48

79
24

56-
54

iS

121

80

22

22
36

43

44

72

114
18

Keuper Sandstein . . .

Lamps for Microscope
Labyrinthodon ....
Leuwenhoek ....

Malpighi, Researches of .
Marchantia

Red Sandstone, New, of
Warwickshire . . .

Scales of Fish ....

— : Butterflies . .
- Dj^uiond Beetle

Sections of Stems, &c. .
Sirex gigas
Skin, Structure of . . .
Spiral Vessels ....
Spiracles
Sponges in Flint .
Stentors

Melicerta
Microscope, Simple . .

Mineral Composition of

Stephanoceros ....

Mounting Objects . . .
Mouths of Insects . . .

Negro, Change from Black
to White in ....
Nepa, Eggs of ....

Object-glasses ....
Objects, Collecting of .
Old Red Sandstone . .

Tadpole, Circulation in .

Tenacity of

Test Fluids
Tooth of Dendrodns . .

Tradescantia ....

Vallisneria spiralis . .
Volvox globator . . .

Ovules of Pollen-grains .

Perspiratory Glands and
Ducts ....

Wheel Animalcules . .
Wings of Insects . . .

Xanthidia in Flint . . .
Yeast Fungus ....

Pigment- cells . . .
Polarising Apparatus .
Pollen-grains . . .
Polycistina ....
Protoplasm ....

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OUR PICTURE BOOK.

TALES FOR THE LITTLE ONES.
MY SUNDAY BOOK OF PICTURES.
SUNDAY GARLAND OF PICTURES
AND STORIES.

SUNDAY READINGS FOR LITTLE FOLKS.

"LITTLE FOLKS" OWN LIBRARY.

Each Book containing several entertaining Tales for Children. Crown i6mo,
with Illustrations, cloth limp, 6d. each.

EVERYBODY'S BOY.

THE CROOKED SIXPENCE.

NEVER AFRAID.

HOPAGOG'S LEG.
NELLY.
LUCKY TYM.

LITTLE TOM STIRLING.

Casselly Fetter 6° Galpin : London, Paris &° New York.

Selections from Cassell, Fetter & Gal pin's Books
for Children and Young People (continued}.

Little Folks. Vols. L, II., III., IV., V., and VI. Con-

taining over 2,000 Pictures, and full of Tales, Pieces of Poetry,
Little Stories, Facts and Anecdotes, and Little Folks' Own Letters'
Riddles, Games, Puzzles, Drawing Copies, &c. Coloured boards 35 •
cloth gilt, gilt edges, 55. each. The Set of Six Volumes, strongly bound
in cloth, price 2is.

*«* LITTLE FOLKS is published in Weekly Numbers at id. and
Monthly Parts at 6<t.

Notable Shipwrecks. Being Tales of Disaster and
Heroism at Sea. By UNCLE HARDY. 320 pp., crown Svo. With
Frontispiece. Second Edition. Cloth, 53.

Soldier and Patriot. The Story of George Washington.
By F. M. OWEN. Illustrated. 256 pp., crown Svo, cloth, 35. 6d.

Half-Hours with Early Explorers. By T. FROST.

Containing Narratives of the Adventures and Discoveries of the Early
Explorers. Profusely Illustrated. 240 pp., fcap. 410, cloth, 55.

Stories about Animals. By the Rev. T. JACKSON,

M. A. A Familiar Description of the Life and Habits of the different
varieties of the Animal World. Profusely Illustrated. 256 pp., extra
fcap. 410, cloth, 55.

Stories about Birds. By M. and E. KIRBY, Authors

of " Chapters on Trees," &c. &c. An Interesting Account of the Life
and Habits of the various descriptions of the Feathered Tribes.
Profusely Illustrated. 256 pp., extra fcap. 410, cloth, 55.

The Old Fairy Tales. A Choice Collection of Favourite

Fairy Tales. Edited by JAMES MASON- With 24 full-page and
numerous other Illustrations. Super-royal i6mo, cloth, 25. 6d.

Pictures of Sohool Life and Boyhood. Being

Selections from the Best Authors, Edited by PERCY FITZGERALD,
M.A., F.S.A. Crown Svo, 256 pp. and Frontispiece, cloth gilt, 33. 6d.

Great Lessons from Little Things. By JOHN TAYLOR.

A Series of Practical Lessons on Bible Natural History. Full of
Illustrations. 176 pp., extra fcap. 410, cloth gilt, 35. 6d.

Patsy's First Glimpse of Heaven. By the Author

of " Scraps of Knowledge." Illustrated, is.

The History of a Book. By ANNIE CARRY. Illustrated

throughout. Extra fcap 4to, cloth, 35. 6d.

Peeps Abroad for Folks at Home. By CLARA

MATEAUX. Profusely Illustrated. Fcap. 4to, cloth. 55.

Home Chat with Our Young Folks. By CLARA

MATEAUX. Fifik Edition. With Two Hundred Engravings. Fcap.
4to, cloth lettered, 260 pages, 55.

Sunday Chats. By CLARA MATEAUX. Profusely Il-
lustrated. Second Edition. Fcap. 4to, cloth gilt, 55.
Leslie's Songs for Little Folks. With Twelve Pieces

of Music by HEMRY LESLIE, and Frontispiece by H. C. SELOUS.
Illustrated. Secc nd Edition. Cloth gilt, 35. 6d.

Cassell, Fetter 6° Galpin : London, Paris 6° New York.

THE "LITTLE GEMS" SERIES.

Cloth, 6d. ; or cloth gilt, gilt edges, is. each.

Shall weKnow One Another?

By the Rev. Canon RYLE, M.A.

Twenty-fifth Thousand.
Home Religion. By the late

Rev. W. B. MACKENZIE, M.A.

Sixteenth Thousand.
The Grounded Staff. By the

Rev. ROBERT MAGUIRE, M.A.

Second Edition.

Words of Help for Every-
day Life. By the Rev. W. M.

STATHAM. Third Edition.

The Voice of Time. By J.

STROUD. Twenty-fourth Thou-
sand.
Pre- Calvary Martyrs, and

other Papers. By the late Rev. J.

B. OWEN, M.A. Second Edition.
All Men's Place. With other

Selections from the Sermons of

GEORGE WHITEFIELD.
God's New World. With other

Selections from the Sermons of

JOHN WESLEY.

TALES ON THE PARABLES.

By ISA CRAIG-KNOX. Consisting of Stories of Modern Life, illustrative of
* the Truths taught in the Parables of the New Testament ; each being

i_i_ :„ ;«.__ir ;__ /SJ i. .

complete in itself, price 6d. each : —

Seed-time and Harvest.
Cumber er of the Q-round.
The G-ood Samaritan.
Lost Silver.
The Pearl.

Yes or No.

The Covetous Man.

Leaven.

The Debtors.

Old Garments.

. The Series can be also had in Two Volumes, cloth gilt, is. 6d. each.

THE "GOLDEN CROWNS" SERIES.

Being -a-^eries of Short Tales for Sunday Reading. By Rev. COMPTON
READ?, M.A., Chaplain of Magdalen College, and some time Vicar of
Cassington, Oxon. Illustrated with Frontispiece in each book, and
bound in cloth, each book being complete in itself. Price 6d. each-

1. The Maiden's Crown. i 4 The Father's Crown.

2. The Wife's Crown. 5. The Little Girl's Crown.

3. The Orphan's Crown. I 6. The Poor Man's Crown.

%* The Complete Series in One Volume, cloth gilt, gilt edges, is. 6d.

*&• The following CATALOGUES of Messrs. CASSELL,
FETTER & GALPIN'S PUBLICATIONS are now ready, and may be
procured from all Booksellers, or post free from the Publishers:

CasselTs Complete Descriptive Catalogue, contain-
ing a List of their numerous Works, including Bibles and Religious
Literature, Children's Books, Editcational Works, Fine Art Volumes,
Serial Publications, &*c.

CasselFs Educational Catalogue, containing a Descrip-
tion of their numerous Educational Works, with Specimen Pages and
Illustrations, and also supplying particulars of CASSELL, PETTER &
GALPIN'S Mathematical Instruments, Water- Colours, Drawing Boards,

T Squares, Set Squares, Chalks, Crayons, Drawing Books, Drawing
" ' ;ls, Drawing Pencils, &c. &c.

Cassell, Fetter 6° Galpin : London, Paris &> New York.