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A COURSE

OF

PRACTICAL INSTRUCTION

IN

ELEMENTARY BIOLOGY.

A COURSE

OF

PRACTICAL INSTRUCTION

IN

ELEMENTARY BIOLOGY

BY

\e? ow"
T. H, HUXLEY, LL.D, Sec. RS,

ASSISTED BY

H. N. MARTIN, BA, MB, D.Sc.

FELLOW OF CHRIST'S COLLEGE, CAMBRIDGE.

London:
MACMILLAN AND CO.

1875.
[All Rights reserved.}

Mn
ly

woe Ae}

Cambridge:
PRINTED BY C. J. CLAY, M.A.
AT THE UNIVERSITY PRESS.

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Vrcwr yon oa vs Mew (ALYY CAPT

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Own Taleweder Tidy

PREFACE.

Very soon after I began to teach Natural History, or what
we now call Biology, at the Royal School of Mines, some
twenty years ago, I arrived at the conviction that the study
of living bodies is really one discipline, which is divided into
Zoology and Botany simply as a matter of convenience; and
that the scientific Zoologist should no more be ignorant of
the fundamental phenomena of vegetable life, than the scien-
tific Botanist of those of animal existence.

Moreover, it was obvious that the road to a sound and
thorough knowledge of Zoology and Botany lay through
Morphology and Physiology; and that, as in the case of all
other physical sciences, so in these, sound and thorough
knowledge was only to be obtained by practical work in

the laboratory.
M. b

vi PREFACE.

The thing to be done, therefore, was to organize a eourse
of practical instruction in Elementary Biology, as a first step
towards the special work of the Zoologist and Botanist. But
this was forbidden, so far as I was concerned, by the limi-
tations of space in the building in Jermyn Street, which
possessed no room applicable to the purpose of a labora-
tory; and I was obliged to content myself, for many years,
with what seemed the next best thing, namely, as full an ex-
position as I could give of the characters of certain plants and
animals, selected as types of vegetable and animal organiza-
tion, by way of introduction to systematic Zoology and Pale-
ontology.

In 1870, my friend Professor Rolleston, of Oxford, pub-
lished his “Forms of Animal Life.” It appears to me that this
exact and thorough book, in conjunction with the splendid
appliances of the University Museum, leaves the Oxford
student of the fundamental facts of Zoology little to desire.
But the Linacre Professor wrote for the student of Animal
life only, and, naturally, with an especial eye to the conditions
which obtain in his own University; so that there was still
room left for a Manual of wider scope, for the use of learners
less happily situated.

In 1872 I was, for the first time, enabled to carry my own
notions on this subject into practice, in the excellent rooms

provided for biological instruction in the New Buildings at

PREFACE. vil

South Kensington. In the short course of Lectures given to
Science Teachers on this occasion, I had the great advantage
of being aided by my friends Dr Foster, F.R.S., Prof. Ruther-
ford and Prof. Lankester, F.R.S., whose assistance in getting
the laboratory work into practical shape was invaluable.

Since that time, the biological teaching of the Royal
School of Mines having been transferred to South Kensing-
ton, I have been enabled to model my ordinary course of
instruction upon substantially the same plan.

The object of the present book is to serve as a laboratory
guide to those who are inclined to follow upon the same road.
A number of common and readily obtainable plants and ani-
mals have been selected in such a manner as to exemplify
the leading modifications of structure which are met with in
the vegetable and animal worlds. A brief description of
each is given; and the description is followed by such detailed
instructions as, it is hoped, will enable the student to know,
of his own knowledge, the chief facts mentioned in the ac-
count of the animal or plant. The terms used in Biology
will thus be represented by clear and definite images of the
things to which they apply; a comprehensive, and yet not
vague, conception of the phenomena of Life will be obtained;
and a firm foundation upon which to build up special know-
ledge will be laid.

The chief labour in drawing up these instructions has

vill PREFACE.

fallen upon Dr Martin. For the general plan used, and the de-
scriptions of the several plants and animals, I am responsible;
but I am indebted for many valuable suggestions and criti-
cisms from the botanical side to my friend Prof. Thiselton

Dyer.
T. H. H.

Lonpon,
September, 1875.

CONTENTS.

I.
YEAsr.

General characters—Fermentation—A ppearances of yeast under the micro-
scope—Structure of yeast cells—Chemical composition—Mode of multiplication
—Growth in Pasteur’s fluid—Physiology of yeast—Laboratory work.

p. I—10.

II.
Prorococcus.

Habitat—Histological structure—Modes of multiplication—Dependence on
light—Physiology of Protococcus—Motile stage—Laboratory work. p. r1—16.

If.
PrRoreus ANIMALCULE. COLOURLESS BLOOD CORPUSCLES.

Ames — Habitat — Movements — Structure — Chemical composition —
Effects of temperature and electric shocks—Encystation—CoLOoURLESS BLOOD
CORPUSCLES—Mouvements—Structure—The influence of various reagents on
them—Physiology of Ameba. Laboratory work. ; + p. 17-23.

IV.
Bacteria.

Form and structure—Movements—Spirillum volutans—Stationary stage—
Zoogloea—Growth in Pasteur’s fluid—Relation to putrefaction—Power of
resisting desiccation—Laboratory work, —. , : . + p. 2428,

x CONTENTS.

Vv.
. Moo.ps.

Fungi—Their spores—PrnicibtL1uM—Habitat—General characters—Form
and structure—Development—Mucor—Habitat—Form and structure—Deve-
lopment, asexual and sexual—Alternation of generations—Mucor Torula—
Laboratory work. : : 5 : - é - Pp. 29—40.

VI.
STONEWORTS.

Habitat and general characters—Development—Mode of growth and micro-
scopicstructure—Protoplasmic movements—Organs of reproduction—Physiology
—Laboratory work. . ; 3 d é Pp. 41—53.

VII.
Tue Bracken Fern.

Habit—Structure, gross and microscopic—The various tissues—Mode of
growth—Development— Prothallus—Sexual organs—Alternation of genera-
tions—Laboratory work. . ‘ , é 4 ‘ ‘ » Pp. 54-67.

VIII.
Ture Brean Puant.

Habit— General structure—Development and mode of growth—Sexual
organs—Homology with the reproductive organs of the Fern—Physiology—
Laboratory work. a 3 : - : : . 3 + p. 68—85:

IX.
Tue Bett ANIMALCULE.

Habit and distribution —Anatomy—Movements— Contractile vesicle —
Ingestion—-Modes of multiplication— Encystation—Laboratory work.

p- 86—g4.
X.

FRESH-WATER POLYPES.
Habit and form—Naked eye appearances—Mode of feeding—Multiplication
Microscopic structure — Relationships to simpler plants and animals —
Laboratory work. i : : . : ‘ + Pp. 95—I03.

CONTENTS. xl

XI.
THE FRESH-WATER MussEL.

General structure—Respiratory organs—Alimentary organs—Circulatory

system—Excretory organs—Reproductive organs—Development—Laboratory

work. ‘ : 3 5 5 ‘i . + Pp. 104—I121.

XII.
THE FRESH-WATER CRAYFISH AND THE LOBSTER.

Habitat—General structure—A ppendages—Segments—Alimentary canal—
Circulatory organs. —Respiratory organs—The Green glands—Nervous system
—Sense organs— Reproductive organs—Development— Laboratory work.

p. 122—151.

XIII.
Tue Froa.

General characters—Development—Specific characters of Rana temporaria
and &. esculenta—The pleuroperitoneal cavity and the alimentary canal—The
neural canal and the cerebro-spinal axis—Objects seen on transverse sections
at various points—Comparison with lobster—The skeleton—The digestive
system—The blood and lymph vascular systems—The ductless glands—The
respiratory organs—The urinary organs—The generative organs—The nervous
system—The sense organs—Laboratory work. ‘ + ps 182—257.

APPENDIX . : . , p- 258.

YEAST (Torula or Saccharomyces Cerevisic).

YEAST is a substance which has been long known on account
of the power which it possesses of exciting the process termed
JSermentation in substances which contain sugar.

If strained through a coarse filter, it appears to the naked
eye as a brownish fluid in which no solid particles can be
discerned. When some of this fluid is added to a solution of
sugar and kept warm, the mixture soon begins to disengage
bubbles of gas and become frothy; its sweetness gradually
disappears ; it acquires a spirituous flavour and intoxicating
qualities; and it yields by distillation a light fluid—alcohol
(or spirits of wine) which readily burns.

When dried slowly and at a low temperature, yeast is
reduced to a powdery mass, which retains its power of exciting
fermentation in a saccharine fluid for a considerable period.
If yeast is heated to the temperature of boiling water, be-
fore it is added to the saccharine fluid, no fermentation takes
place; and fermentation which has commenced is stopped
by boiling the saccharine liquid.

A saccharine solution will not ferment spontaneously.
If it begins to ferment, yeast has undoubtedly got into it in
some way or other.

If the yeast is not added directly to the saccharine fluid,
but is separated from it by a very fine filter, such as porous
earthenware, the saccharine fluid will not ferment, although
the filter allows the fluid part of the yeast to pass through
into the solution of sugar.

M. 1

2 ELEMENTARY BIOLOGY. [.

If the saccharine fluid is boiled, so as to destroy the
efficiency of any yeast it may accidentally contain, and then
allowed to come in contact only with such air as has been
passed through cotton wool, it will never ferment. But if it
is exposed freely to the air, it is almost sure to ferment sooner
or later, and the probability of its so doing is greatly increased
if there is yeast anywhere in the vicinity.

These experiments afford evidence (1) that there is some-
thing in yeast which provokes fermentation, (2) that this
something may have its efficiency destroyed by a high tem-
perature, (3) that this something consists of particles which
may be separated from the fluid which contains them by a
fine filter, (4) that these particles may be contained in the
air; and that they may be strained off from the air by
causing it to pass through cotton wool.

Microscopic examination of a drop of yeast shews what
the particles in question are.

Even with a hand-glass, the drop no longer appears
homogeneous, .as it does to the naked eye, but looks as if fine
grains of sand were scattered through it; but a considerable
magnifying power (5—600 diameters) is necessary to shew the
form and structure of the little granules which are thus
made visible. Under this power, each granule (which is
termed a Torula) is seen to be a round, or oval, transparent

body, varying in diameter from 5 < oth to aad th of an inch

_ a).

The Torule are either single, or associated in heaps or
strings. Each consists of a thin-walled sac, or bag, containing
a semi-fluid matter, in the centre of which there is often a
space full of a more clear and watery fluid than the rest,
which is termed a ‘vacuole. The sac is comparatively tough,
but it may be easily burst, when it gives exit to its contents,

(on the average about ——.

1.] YEAST. 3

which readily diffuse themselves through the surrounding:
fluid. The whole structure is called a ‘cell;’ the sac being
the ‘cell-wall’ and the contents the ‘protoplasm.’

When yeast is dried and burned in the open air it gives
rise to the same kind of smell as burning animal matter, and
a certain quantity of mineral ash is left behind. Analysed
into its chemical elements, yeast is found to contain Carbon,
Hydrogen, Oxygen, Nitrogen, Sulphur, Phosphorus, Potassium,
Magnesium and Calcium; the last four in very small quanti-
ties.

These elements are combined in different ways, so as
to form the chief proximate constituents of the Torula, which
are (1) a Protein compound, analogous to Casein, (2) Cellulose,
(3) Fat, and (4) Water. The cell-wall contains all the Cellulose
and a small proportion of the mineral matters. The protoplasm
contains the Protein compound and the Fat with the larger
proportion of the mineral salts.

These Torule are the ‘particles’ in the yeast which have
the power of provoking fermentation in sugar; it is they
which are filtered off from the yeast when it loses its effi-
ciency by being strained through porous earthenware; it
is they which form the fine powder to which yeast is reduced
by drying, and which, from their extreme minuteness, are
readily diffused through the air in the form of invisible
dust.

That the ZTorule are living bodies is proved by the
manner in which they grow and multiply. If a small
quantity of yeast is added to a large quantity of clear
saccharine fluid so as hardly to disturb its transparency,
and the whole is kept in a warm place, it will gradually
become more and more turbid, and, after a time, a scum of
yeast will collect, which may be many thousand, or million,
times greater in weight than that which was originally
added. If the Torule are examined as this process of

1—2

4 ELEMENTARY BIOLOGY. [1.

multiplication is going on, it will be found that they are
giving rise to minute buds, which rapidly grow, assume the
size of the parent Torula, and eventually become detached;
though, generally, not until they have developed other buds,
and these yet others. The Yorule thus produced by gem-
mation, one from the other, are apt long to adhere together,
and thus the heaps and strings mentioned, as ordinarily
occurring in yeast, are produced. No Torula arises except
as the progeny of another; but, under certain circumstances,
multiplication may take place in another way. The Torula
does not throw out a bud, but its protoplasm divides into
(usually) four masses, each of them surrounds itself with
a cell-wall, and the whole are set free by the dissolution
of the cell-wall cf the parent. This is multiplication by
endogenous division.

As each of the many millions of Torule which may thus
be produced from one Yorula has the same composition as
the original progenitor, it follows that a quantity of Protein,
Cellulose and Fat proportional to the number of Torule
thus generated, must have been produced in the course of
the operation. Now these products have been manufactured
by the Torule out of the substances contained in the fluid
in which they float and which constitute their food.

To prove this it is necessary that this fluid should have
a definite composition. Several fluids will answer the pur-
pose, but one of the simplest (Pasteur’s solution) is the
following.

Ammonium Tartrate (C,H,(N H,),0)).
Potassium Phosphate (KH,PO,).
Calcium Phosphate — (Ca,P,O,).
Magnesium Sulphate (MgSO,).
In this fluid the Torudce will grow and multiply. But it

1] YEAST. 5

will be observed that the fluid contains neither Protein nor
Cellulose, nor Fat, though it does contain the elements of these
bodies arranged in a different manner. It follows that the
Torula must absorb the various substances contained in the
water and arrange their elements anew, building them up
into the complex molecules of its own body. This is a
property peculiar to living things.

The Yorula being alive, the question arises whether it is
an animal or a plant. Although no sharp line of demarcation
can be drawn between the lowest form of animal and of veget-
able life, yet Torula is an indubitable plant, for two reasons.
In the first place, its protoplasm is invested by a continuous
cellulose coat, and thus has the distinctive character of a
vegetable cell. Secondly, it possesses the power of construct-
ing Protein out of such a compound as Ammonium Tartrate,
and this power of manufacturing Protein is distinctively
a vegetable peculiarity. Zorula then is a plant, but it
contains neither starch nor chlorophyll, it absorbs oxygen and
gives off carbonic anhydride, thus differing widely from the
green plants. On the other hand, it is, in these respects, at
one with the great group of Fungi. Like many of the latter,
its life is wholly independent of light, and in this respect,
again, it differs from the green plants.

Whether Zorula is connected with any other form of
Fungi is a question which must be left open for the present.
It is sufficient to mention the fact that under certain circum-
stances some Fungi (e. g. Mucor) may give rise to a kind of
Torula different from common yeast.

The fermentation of the sugar is in some way connected
with the living condition of the Torwla, and is arrested by all
those conditions which destroy the life of the Torula and
prevent its growth and reproduction. The greater part of the
sugar is resolved into Carbonic anhydride and Alcohol, the
elements of which, taken together, equal in weight those of the

6 ELEMENTARY BIOLOGY. [I.

sugar. A small part breaks up into Glycerine and Succinic
acid, and one or two per cent. is not yet accounted for, but is
perhaps assimilated by the Torule.

This is the more probable as Torule will grow and multiply
actively in a solution in which sugar and Ammonium Nitrate
replace the Ammonium Tartrate of the former solution, in
which case the carbon of the Protein, Cellulose and Fat manu-
factured, must be obtained from the sugar. Moreover, though
oxygen is essential to the life of the Torula, it can live in
saccharine solutions which contain no free oxygen, appearing,
under these circumstances, to get its oxygen from the sugar.

It has further been ascertained that Zorule flourish
remarkably in solutions in which sugar and pepsin replace
the Ammonium Tartrate. In this case, the nitrogen of their
protein compounds must be derived from the pepsin; and
it would seem that the mode of nutrition of such Torule
approaches that of animals.

LABORATORY WORK.

Sow some fresh baker’s yeast in Pasteur’s fluid* with
sugar and keep it in a warm place: as soon as the mixture
begins to froth up, and the yeast is manifestly increasing in
quantity, it is ready for examination.

1 Pasteur’s fluid :

Potassium Phosph.
Pree, Calcium Phosph. .........
~ Magnesium Sulphate
Ammonium Tartrate

[Cane sugar ..............
s WAOr s,s; iss tot oeetestanemucerier gee

The sugar is to be omitted when Pasteur’s fluid ‘without sugar” is
ordered. Pasteur himself used actual yeast ash; the above constituents give
an imitation ash, which, with the ammonium salt and sugar, answers all
practical purposes,

1]

YEAST. 7

A. MorpHoLoey.

1.

ie)

Spread a little out, on a slide, in a drop of the fluid,
and examine it with a low power (4 inch objective)
without a cover-glass. Note the varying size of the
cells, and their union into groups.

Cover a similar specimen with a thin glass and exa-
mine it under a high power (4 or better ¢ objective.
Hartnack, No. 7 or 8, Oc. 3 or 4).

Note the size (measure), shape, surface and mode
of union of the cells.

b. Their structure: sac, protoplasm, vacuole.

a. Sac; homogeneous, transparent.

8. Protoplasm; less transparent; often with a few
clear shining dots in it.

y. Vacuole ; sometimes absent; size, position.
é

The relative proportion of sac, protoplasm, and
vacuole in various cells.

Draw a few cells carefully to scale.

3.

Run in magenta solution under the cover-glass. (This
is readily done by placing a drop of magenta solution
in contact with one side of the cover-glass, and a
small strip of blotting paper at the opposite side.)

a. Note what cells stain soonest and most deeply,
and what part of each cell it is that stains: the sac is
unaffected; the protoplasm stained; the vacuole un-
stained, though it frequently appears pinkish, being
seen through a coloured layer of protoplasm.

Burst the stained cells by placing a few folds of blotting
paper on the surface of the cover-glass and pressing
smartly with the handle of a mounted needle: note
the torn empty and colourless, but solid and un-

ELEMENTARY BIOLOGY. [I.

crushed transparent sacs; the soft crushed stained
protoplasm.

Repeat observation 3, running in iodine solution instead
of magenta. The protoplasm stains brown; the rest of
the cell remains unstained. Note the absence of any
blue coloration ; starch is therefore not present.

Treat another specimen with potash solution, running
it in as before: this reagent dissolves out the proto-
plasm, leaving the sac unaltered.

[Sow a few yeast-cells in Pasteur’s solution in a moist
chamber and keep them under observation from day to day;
watch their growth and multiplication. ]

[Endogenous division: take some yeast which has been
grown in Pasteur’s solution at a temperature below 20° C.;
spread it out in a thin layer on fresh cut potato slices or on
some plaster of Paris, and place with wet blotting paper
under a bell-jar: examine trom day to day with a very
high power (800 diam.) for ascospores, which will probably
be found on the fifth or sixth day.]

B. PHYSIOLOGY.

(Conditions and results of the vital activity of Torula.)
1.

aes oe

[e.

Sow a fair-sized drop of yeast in—
Distilled water.

10 per cent. solution of sugar in water.
Pasteur’s fluid without the sugar.
Pasteun’s fluid with sugar.

Mayer’s pepsin solution’. ]

1 Mayer’s solution (with pepsin) =

Dibydropotassic phosphate............ o'r grm. ~

1.] YEAST. 9

Keep all at about 35° C., and compare the growth of the
yeast, as measured by the increase of the turbidity of the
fluid, in each case. “a” will hardly grow at all, “b” better,
“oe” better still, “d’’ well, and “e” best of all. Note that
bubbles of gas are plentifully evolved from both the solutions
which contain sugar.

That any growth at all takes place,in the case of experi-
ments @ and b,is due to the fact that the drop of yeast added
contains nutritious material sufficient to provide for that
amount of growth.

2. Prepare two more specimens of “d” and keep one in a
cold—the other in a warm (35°C.) place, but otherwise
under like conditions. Compare the growth of the
yeast in the two cases; it is much greater in the
specimen kept warm.

3. Prepare two more specimens of d”; keep both warm,
but one in darkness, the other exposed to the light :
that in the dark will grow as well as the other; sun-
light is therefore not essential for the growth of
Torula.

4. Sow some yeast-cells in Pasteur’s solution in a flask,
the neck of which is closed by a plug of cotton
wool, and heat to 100°C. for five minutes; then set
it aside; no signs of vitality will afterwards be mani-
fested by the yeast in the flask; it is killed by ex-
posure to this temperature.

5. [Take two test tubes; in one place some yeast, with
Pasteur’s solution containing sugar; in the other place
baryta water, and then connect the two test tubes by tightly
fitting perforated corks and a bent tube passing from above
the surface of the fluid in the first tube to the bottom of
the baryta water in the second; pass a narrow bent tube,
open at both ends, through the cork of the baryta water

10 ELEMENTARY BIOLOGY. he

tube, so that its outer end dips just below the surface of
some solution of potash’. All gas formed in the first tube
will now bubble through the baryta water in the second,
and, from thence, any that is not absorbed will pass out
through the potash into the air. An abundant precipitate
of barytic carbonate will be formed which can be collected
and tested. The fermenting fluid, therefore, evolves car-
bonie anhydride. }

6. [Grow some yeast in Pasteur’s solution (with sugar), in a
nearly closed vessel (say a bottle with a cork through which
a long narrow open tube passes): as soon as the evolution of
gas seems to have ceased, distil the fluid in a water bath
and condense and collect the first fifth that comes over:
redistil this after saturation with potassic carbonate, and
test the distillate for alcohol by its odour and inflammability,
and by the sulphuric acid and potassic dichromate test. |

7. [Determine that heat is evolved by a fluid in which active
alcoholic fermentation is going on. Place 200 ce. of fresh
yeast in a flask, and add 1 litre of Pasteur’s fluid with
sugar: put another litre of the fluid alone in a similar flask,
cover each flask with a cloth and place the two side by side
in a place protected from draughts. When gas begins to be
actively evolved from the yeast-containing solution, take the
temperature of the fluid in each flask with a good thermo-
meter; the temperature of the one in which fermentation is
going on will be found the higher.]

1 The object of the potash is to shield the baryta water from any car-
bonic acid that may be in the atmosphere,

Il.
PROTOCOCCUS (Protococeus pluvialis).

Ir the mud which accumulates in roof-gutters, water-
butts, and shallow pools, be collected, it will be found to
contain, among many other organisms, specimens of Pro-
tococcus. In one of the two conditions in which it occurs, Pro-
tococcus is a spheroidal body -_ to a of an inch in
diameter, composed, like TZorula, of a structureless tough
transparent wall, inclosing viscid and granular protoplasm.
The chief solid constituent of the cell-wall is cellulose. The
protoplasm contains a nitrogenous substance, doubtless of a
proteinaceous nature, though its exact composition has not
been determined, and indications of starchy matter are some-
times to be found init. Either diffused through it, or collected
in granules, is a red or green colouring matter (Chlorophyll).
Individual Protococct may be either green or red; or half
greer and half red; or the red and green colours may coexist
in any other proportion.

In addition to the single cells, others are found divided by
partitions, continuous with the cellulose wall, into two or more
portions, and the cells thus produced by fission become sepa-
rate, and grow to the size of that form from which they started.
Tn this manner Protococcus multiplies with very great rapidity,
Multiplication by gemmation in the mode observed in
Torula is said to occur, but is certainly of rare occurrence.

12 ELEMENTARY BIOLOGY. [II.

The influence of sunlight is an essential condition of the
growth and multiplication of Protococcus; under that in-
fluence, it decomposes carbonic anhydride, appropriates the
carbon, and sets oxygen free. It is this power of obtaining
the carbon which it needs from carbonic anhydride, which is
the most important distinction of Protococcus, as of all plants
which contain chlorophyll, from Yoruwla and the other Fungi.

As Protococcus flourishes in rain-water, and rain-water
contains nothing but carbonic anhydride, which it absorbs
along with other constituents of the atmosphere, ammonium
salts (usually ammonium nitrate, also derived from the air)
and minute portions of earthy salts which drift into it as
dust, it follows that it must possess the power of constructing
protein by rearrangment of the elements supplied to it by
their compounds.

Torula, on the other hand, is unable to construct protein
matter out of such materials. Another difference between
Torula and Protococcus is only apparent: Torula absorbs
oxygen and gives out carbonic anhydride; while Protococcus,
on the contrary, absorbs carbonic anhydride and gives out
oxygen. But this is true only so long as the Protococcus is
exposed to sunlight. In the dark, Protococcus, like all other
living things, undergves oxidation and gives off carbonic anhy-
dride; and there is every reason to believe that the same process
of oxidation and evolution of carbonic anhydride goes on in the
light, but that the loss of oxygen is far more than covered by
the quantity set free by the carbon-fixing apparatus, which is
in some way related to the chlorophyll.

The still condition of Protococcus, just described, is not the
only state in which it exists. Under certain circumstances,
a Protococcus becomes actively locomotive. The protoplasm
withdraws itself from the cell-wall at all but two points,
where it protrudes through the wall in the form of long
vibratile filaments or cilia, and by the lashing of these cilia

‘

II.] PROTOCOCCUS, 13

the cell is propelled with a rolling motion through the water.
The movement of the cilia is so rapid, and their substance
is so, transparent and delicate, that they are invisible until
they begin to move slowly, or are treated with reagents, such
as iodine, which colour them.

Not unfrequently the cell-wall eventually vanishes, and the
naked protoplasm of the cell swims about, and may undergo
division and multiplication in this state. Sooner or later, the
locomotive form draws in its cilia, becomes globular, and,
throwing out a cellulose coat, returns to the resting state.

For reasons similar to those which prove the vegetable
nature of Zorula, Protococcus is a plant, although, in its
locomotive condition, it is curiously similar to the Monads
among the lowest forms of animal life. But it is now known
that many of the lower plants, especially 1 in the group of Algae,
to which Protococcus belongs, give rise, under certain circum-
stances, to locomotive bodies propelled by cilia, like the loco-
motive Protococcus, so that there is nothing anomalous in
the case of Protococcus.

Like the yeast-plant, Protococcus retains its vitality after
it has been dried. It has been preserved for as long as two
years in the dry condition, and at the end of that time has
resumed its full activity when placed in water. The wide
distribution of Protococcus on the tops of houses and
elsewhere, is thus readily accounted for by the transport of
the dry Protococct by winds.

14 ELEMENTARY BIOLOGY. [1I.

LABORATORY WORK.

A. MorpPHOLoGy.

a. Resting or stationary Protococcus.

1. Spread out some of the green matter in water, and
put on a cover-glass. Examine first with a low, and
then with a high power. Note the size, form, struc-
ture, and colour of the cells.

Size ; (measure)—very variable.

Form; more or less spheroidal, with individual varia-
tions.

Structure ; sac—protoplasm—sometimes a vacuole-—
sometimes apparently a nucleus. (Compare
Torula, I. A. 2. 6.)

Colour ; generally green—sometimes red—sometimes
half and half—sometimes centre red, periphery
green—the colouring matter always in the pro-
toplasm only—most frequently diffused, but
sometimes in distinct granules.

2. Note especially the following forms of cell—

a. The primitive or normal form.

Roundish cells, with a cellulose sac, and unseg-
mented granular contents. Draw several carefully
to scale. Apply the methods of mechanical and
chemical analysis detailed for Torula. (I. A. 3. 4.
5.6.) Note that iodine in some cells produces a
blue coloration (? starch). Treat a specimen with
iodine solution and then with sulphuric acid (75
per cent.): the sac will become stained blue.

I1.]

d.

a

B.

PROTOCOCCUS. 15
Cells multiplying by fission :

Simple fission. The protoplasm divides into
two segments and then forms a_ partition
dividing the sac; the halves either separate
at once, and each rounds itself off and becomes
an independent cell; or one or both halves
again divide, in a similar way, before they
separate, and so three or four new cells are
produced.

Cells multiplying by budding, like Torula; rare.

b. Motile stage.

a. Mount a drop of water containing motile Proto-

B.

coccus, and examine with a high power. Note
the minute, actively locomotive green bodies, of
which two varieties can be distinguished.

Small, green, pear-shaped cells.

Run in iodine, which stains them and also
kills them and stops their movements: note
then the absence of any distinct sac, and the:
two cilia attached to the narrower end.

A form larger than the last and apparently
intermediate to it and the still cells.

Kill and stain with iodine as before. Note
the central granular coloured (protoplasmic)
portion—the loosely enveloping unstained sac
—the two cilia prolonged from the protoplasm
through an opening in the sac.

c. Try to find specimens in which the movements are
becoming sluggish, and see the cilia in motion.

16

ELEMENTARY BIOLOGY. {i1.

[B. Puysroxoey.

Get some water that is quite green from containing a
large quantity of Protococcus; introduce some of it
into two tubes inverted over mercury, and pass a smal]
quantity of carbonic anhydride into each: keep one tube
in the dark and place the other in bright sunlight for
some hours. Then measure the gas in each tube and after-
wards introduce a fragment of caustic potash into each ;
the gas from the specimen kept in the dark will be more or
less completely absorbed (= carbonic anhydride), that from
the other will not be absorbed by the potash alone, but will
be absorbed on the further introduction of a few drops of
solution of pyrogallic acid (=oxygen). Protococcus, there-
fore, in the sunlight, takes up carbonic anhydride and
evolves oxygen. A comparative experiment may be made
with a third tube containing water but no Protococcus. |

ITT.

THE PROTEUS ANIMALCULE (Ameba).
COLOURLESS BLOOD CORPUSCLES.

Amcebe are minute organisms of very variable size which
occur in stagnant water, in mud, and even in damp earth,
and are frequently to be obtained by infusing any animal
matter in water and allowing it to evaporate while exposed
to direct sunlight.

An Ameba has the appearance of a particle of jelly,
which is often more or less granular and fluid in its central
parts, but usually becomes clear and transparent, and of a
firmer consistency, towards its periphery. Sometimes Amcebec
are found having a spherical form and encased in a structureless
sac, and in this encysted state they exhibit no movements.
More commonly, they present incessant and frequently rapid
changes of form, whence the name of “ Proteus Animalcule”
given to them by the older observers; and these changes of
form are usually accompanied by a shifting of position, the
Amoeba creeping about with considerable activity, though with
no constancy of direction.

The changes of form, and the movements, are effected by
the thrusting out of lobe-lke prolongations of the peripheral
part of the body, which are termed pseudopodia, sometimes
from one region and sometimes from another. Occasionally,
a particular region of the body is constantly free from pseu-

M. 2

18 ELEMENTARY BIOLOGY. [III

dopodia, and therefore forms its hindmost part when it moves.
Each pseudopodium is evidently, at first, an extension of the
denser clear substance (ectosarc) only ; but as it enlarges, the
central, granular, more fluid substance flows into its interior,
often with a sudden rush.

In some Amcbe a clear space makes its appearance, at
intervals, in a particular region of the ectosarc, and then
disappears by the rapid approach of its walls. After a while,
a small clear speck appears at the same spot and slowly
dilates until it attains its full size, when it again rapidly
disappears as before. Sometimes two or three small clear
spots arise close together, and run into one another to form
the single large cavity.

The structure thus described is termed the contractile
vesicle or vacuole, and its rhythmical systole and diastole
often succeed one another with great regularity.

Nothing is certainly known respecting its function, nor
even whether it does or does not communicate with the
exterior, and thus pump water into and out of the body of
the Amba, though there is some reason to think that this
may be the case.

Very frequently one part of the Ameba exhibits a
rounded or oval body, which is termed the nucleus. This
structure sometimes has a distinctly vesicular character, and
contains a rounded granule called the nucleolus.

The gelatinous body of the Amaba is not bounded by
anything that can be properly termed a membrane; all that
can be said is, that its external or limitary layer is of a
somewhat different constitution from the rest, so that it
acquires a certain appearance of distinctness when it is acted
upon by such reagents as acetic acid, or when the animal is
killed by raising the temperature to 45° C. Physically, the
ectosarc might be compared to the wall of a soap-bubble,
which, though fluid, has a certain viscosity, which not only

111. ] THE PROTEUS ANIMALCULE. 19

enables its particles to hold together and form a continuous
sheet, but permits a rod to be passed into or through the
bubble without bursting it; the walls closing together, and
recovering their continuity, as soon as the rod is drawn away.

It is this property of the ectosare of the Ameba which
enables us to understand the way in which these animals
take in and throw out again solid matter, though they have
neither mouth, anus, nor alimentary canal. The solid body
passes through the ectosarc, which immediately closes up and
repairs the rent formed by its passage. In this manner, the
Amebe take in the small, usually vegetable, organisms, which
serve them for food, and subsequently get rid of the un-
digested solid parts.

The chemical composition of the bodies of the Amebe
has not been accurately ascertained, but they undoubtedly
consist, in great measure, of water containing a protein com-
pound, and are similar to other forms of protoplasm. They
absorb oxygen and give out carbonic acid, and the presence
of free oxygen is necessary to their existence. When the
medium in which they live is cooled down to the freezing
point their movements are arrested, but they recover when
the temperature is raised. At a temperature of about 35°C.
their movements are arrested, and they pass into a condition
of “heat-stiffening,” from which they recover if that tempera-
ture is not continued too long; at 40° to 45° C. they are killed.

Electric shocks of moderate strength cause Amebe at
once to assume a spherical still form, but they recover after a
while. Strong shocks kill them.

Not unfrequently, an active Amoeba becomes still spon-
taneously, acquires a rounded form, and secretes a structure-
less case or cyst, in which it remains enclosed for a shorter
or longer period.

If Amebe are not to be found, their nature may be
understood by the examination of bodies, in many respects

2—2

20 ELEMENTARY BIOLOGY. [11.

very similar to them, which occur in the blood of all verte-
brate and most invertebrate animals, and are known as the
‘colourless corpuscles.’ They are to be met with in abun-
dance in a fresh-drawn drop of human blood. In such a
drop, after the red corpuscles have run into rolls, irregular
bodies will be seen here and there in the meshes of the rolls.
If one of these bodies is carefully watched it will be seen to
undergo changes of form of the same character as those
exhibited by Amebe, and these motions become much more
active if the drop is kept at the temperature of the body
by means of a hot stage. Each corpuscle is, in fact, a mass
of protoplasm containing a nucleus, and the protoplasm
sends out pseudopodia which are strictly comparable to
those of Amabe. The colourless corpuscles, however, possess
no contractile space.

The colourless corpuscles of the blood of some of the
cold-blooded vertebrates, such as Frogs and Newts, may be
kept alive for many weeks in serum properly protected from
evaporation; and if finely divided colouring matter, such
as indigo, is supplied to them, either in the body or out of
it, they take it into their interior in the same way as true
Ameoebee would. In the earliest condition of the embryo, the
whole body is composed of such nucleated cells as the colour-
less corpuscles of the blood; and the colourless corpuscles
must be regarded as simply the progeny of such cells, which
have not become metamorphosed, and have retained the
characteristics of the lowest and most rudimentary forms of »
animal life.

The Ameba is an animal, not because of its contractility
or power of locomotion, but because it never becomes inclosed
within a cellulose sac, and because it is devoid of the power
of manufacturing protein from bodies of a comparatively
simple chemical composition. The Ameba has to obtain
its protein ready made, in which respect it resembles all true

III. ] THE PROTEUS ANIMALCULE. 21

animals, and therefore is, like them, in the long run, depend-

ent for its existence upon some form or other of vegetable
life.

LABORATORY WORK.

Place a drop of water containing Amebe on a slide, cover
with a cover glass, avoiding pressure, and search over with
+ inch obj.: having found an Ameeba, examine with a higher
power.

1. Size: differing considerably in different specimens.
Measure.

2. Outline: irregular, produced into a number of thick
rounded eminences (pseudopodia) which are constantly
undergoing changes: sketch it at intervals of five
seconds.

3. Structure:

a. Outer hyaline border (ectosarc), tolerably sharply
marked off: granular layer (endosarc) inside this,
gradually passing into a more fluid central part.

b. Nucleus: (absent in some specimens) ; a roundish
more solid-looking particle, which does not change
its form.

c. Contractile vesicle : in the ectosarc note a roundish
clear space which disappears periodically, and after
a time reappears ; its slow diastole—rapid systole.
Not present in all specimens.

d. Foreign bodies (swallowed); Diatom cases, Des-
madre, &e.

22 ELEMENTARY BIOLOGY. [qu

4. Movements:

a. Watch the process of formation of a pseudopodium.
A hyaline elevation at first ; then, as it increases
in size, currents carrying granules flow into it.

b. Locomotion: watch the process,—a pseudopodium
is thrown out, and then the rest of the body
is gradually drawn up to it.

c. If the opportunity presents itself watch the pro-
cess of the ingestion of solid matters.

d. [Observe the movements on the hot stage; warmth
at first accelerates the movements, but as the tem-
perature approaches 40° C. they cease, and the whole
mass remains as a motionless sphere. |

e. [Effects of electrical shocks on the movements. |

5. Mechanical Analysis: crush. The whole collapses, ex-
cept sometimes the nucleus, and even that after a time
disappears: there is no trace of a distinct resisting

outer sac.

6. Chemical Analysis: Treat with magenta and iodine.
The whole stains, and there is no unstained enveloping
sac. Iodine as a rule produces no blue coloration ;
when blue specks become visible it is probable that
the starch which they indicate has been swallowed.

7. [Look for encysted specimens: and for specimens which
are undergoing fission. ]

8. Another form of Ameeba is not unfrequently found
which differs from that just described in being much
less coarsely granular, and in having no well-defined
ectosare and endosarc, and also in having much longer,
more slender and pointed pseudopodia.

1. ] THE PROTEUS ANIMALCULE. 23

B. Wuire BLoop-CorPusciEs, (human).

Prick your finger and press out a drop of blood: spread
out on a slide under a coverslip, avoiding pressure, and
surround the margin of the coverglass with oil. Neglect
the pale yellow homogeneous (red) corpuscles, and examine
the much less numerous, granular, colourless, ones.

Note their—
1. Size: (measure).

Form: changing much like that of the Amceba, but
less actively. Draw at intervals of ten seconds.

3. Structure: Some more and some less granular; but
no distinct ectosarc, endosarc, and vacuole as in the
Ameba. Nucleus rarely visible in the fresh state.
No contractile vesicle.

4. Treat with dilute acetic acid: the granules are cleared
up, and a nucleus is brought into view in a more or
less central position. Ifthe acetic acid has been too
strong the nucleus will be constricted and otherwise
distorted.

5. Stain with magenta, and iodine; the whole becomes
coloured, the nucleus most intensely.

6. Place on the hot stage, and gradually warm up to 50°C.
The movements are at first rendered more active, but
ultimately cease, the pseudopodia-like processes being
all retracted and the whole forming a motionless
sphere.

Let the specimen cool again ; the movements are not
resumed; the protoplasm having passed into a state
of permanent coagulation or rigidity.

7. Repeat the above observations on the white blood-
corpuscles of the frog or newt.

iv,

BACTERIA.

UNDER the general title of Bacterium a considerable variety
of organisms, for the most part of extreme minuteness, are
included.

They may be defined as globular, oblong, rod-like or
spirally coiled masses of protoplasmic matter enclosed in a
more or less distinct structureless substance, devoid of chloro-
phyll and multiplying by transverse division. The smallest

are not more than th of an inch in diameter, so that

1
30000
under the best microscopes they appear-as little more than
mere specks, and even the largest have a thickness of little
more than 70000 a 00 th of an inch, though they may be very long
in proportion. Many of them have, like Protococcus, two
conditions —a still and an active state. In their still con-
dition, however, they very generally exhibit that Brownian
movement which is common to almost all very finely divided
solids suspended in a fluid. But this motion is merely
oscillatory, and is readily distinguishable from the rapid
translation from place to place which is effected by the really
active Bacteria.

In one of the largest forms, Spirillum volutans, it has been
possible to observe the cilia by which the movement is
effected. In this there is a cilium at each end of the

Iy.] BACTERIA. 25

spirally coiled body. No such structure, however, can be
made out in the straight Bacteria, and it remains doubtful
whether they possess cilia which are too fine to be rendered
visible by our microscopes, or whether their movements are
due to some other cause. Many forms, such as the Vibriones,
so common in putrefying matters, appear obviously to have a
wriggling or serpentiform motion, but this is an optical de-
lusion. In this Bacterium, as in all others, the body does not
rapidly change its form; but its joints are bent zig-zag-wise,
and the rotation of the zig-zag upon its axis, as it moves, gives
rise to the appearance of undulatory contraction. A cork-
screw turned round, while its point rests against the finger,
gives rise to just the same appearance.

Bacteria, in the still state, very often become surrounded
by a gelatinous matter, which seems to be thrown out by
their protoplasmic bodies, and to answer to the cell-wall of
the resting Protococcus. This is termed the Zooglea form of
Bacterium.

Bacteria grow and multiply in Pasteur’s solution (without
sugar) with extreme rapidity, and, as they increase in number,
they render the fluid milky and opaque. Their vital actions
are arrested at the freezing point. They thrive best in a
temperature of about 30°C. but, in most fluids, they are killed
by a temperature of 60°C. (140° F.).

In all these respects Bacteria closely resemble Torule ;
and a further point of resemblance lies in the circumstance
that many of them excite specific fermentative changes in
substances contained in the fluid in which they live, just as
yeast excites such changes in sugar.

All the forms of putrefaction which are undergone by
animal and vegetable matters are fermentations set up by
Bacteria of different kinds. Organic matters freely exposed
to the air are, in themselves, nowise unstable bodies, and, if due
precautions have been taken to exclude Bacteria, they do not

26 ELEMENTARY BIOLOGY. [Iv.

putrefy, so that, as has been well remarked, “putrefaction is a
concomitant not of death, but of life.”

Bacteria, like Torule and Protococct, are not killed by dry-
ing up, and from their excessive minuteness they must be
carried about still more easily than Zorule are. In fact
there is reason to believe that they are very widely diffused
through the air, and that they exist in abundance in all
ordinary water and on the surface of all vessels that are not
chemically clean. They may be readily filtered off from
the air, however, by causing it to pass through cotton wool.

LABORATORY WORK.

1. Infuse some hay in warm water for half an hour—
filter, and set aside the filtrate: note the changes
which go on in it—at first clear, in 24 or 36 hours it
becomes turbid; later on, a scum forms on the sur-
face and the infusion acquires a putrefactive odour.

2. Rub some gamboge down in water and examine a
drop of the mixture with a high power: avoid all
currents in the fluid and watch the Brownian move-
ments; note that they are simply oscillatory—not
translative.

3. Take a drop of fluid from a turbid hay infusion—
and examine it, using the highest power you have; in
it will be found muititudes of

Moving Bacteria. Note their—

a. orm; elliptic or rodlike—sometimes forming
short (2—8) jointed rows.

Iv.]

d.

BACTERIA. 27

Size; breadth, very small but pretty constant ;
length, varying, but several times greater than

- their breadth.: measure.

Structure ; an outer more transparent layer enve-
loping less transparent matter: in the compound
forms the envelope alone appears where two
joints come in contact, so that the rod looks
as if made up of alternating transparent and
more opaque substances

Movements ; some vital, and some purely physical
(Brownian). The former various but progressive :
the latter, a rotatory movement round a sta-
tionary centre; study it in a drop of boiled
infusion in which the Bacteria are all dead.

Treat with iodine—only the more opaque parts stain;
probably then we have to do with protoplasm, enve-
loped in non-protoplasmic matter.

Resting Bacteria. (Zoogloea-stage.)

a.

Examine the scum from the surface of a hay
infusion; it exhibits myriads of motionless Bac-
teria, embedded in gelatinous material.

Treat with iodine; the Bacteria stain as before:
the gelatinous uniting material remains un-
stained,

Mixed with the Bacteria proper, both in the pellicle
and the fluid beneath, may be found the following
forms of living beings.

a.

Micrococcus. Bodies much like Bacteria, but
short and rounded, and occurring singly, or in
bead-like rows. They may be found free or in a
Zoogloea stage.

“I

ELEMENTARY BIOLOGY. [Iv.

b. Bacillus. Threads composed of straight cylindri-
cal joints much longer than those of Bacteria, but
of a similar structure: they are always free-
swimming.

c. Vibrio. Like Bacillus, but with bent joints.

d. Spirillum. Elongated unjointed threads rolled
up into a more or less perfect spiral: frequently
two spirals intertwine. In some of the largest
forms a vibratile cilium can be made out on each
end of the thread.

e. Spirochete. Much like spirillum, but longer and
with a much more closely rolled spiral. A very
actively motile but not common form,

Examine various putrefying fluids for Bacteria and
related organisms.

Place some fresh-made hay infusion in three flasks;
boil two of them for three or four minutes, and while
one is boiling briskly stop its neck with a plug of
cotton-wool: leave the necks of the other two flasks
unclosed, and put all three away in a warm place.

a. Ina day or two abundant Bacteria will be found
in the unboiled flask.

b. In the boiled but unclosed flask Bacteria will
also appear, but perhaps not quite so soon as
in a.

c. In the flask which has been boiled and kept
closed Bacteria will not appear, if the experiment

has been properly performed, even if it be kept
for many months.

Vv.
MOULDS (Penicillium and Mucor).

Torula, Protococcus and Ameba are extremely simple con-
ditions of the two great kinds of living matter which are
known as Plants and Animals. No plants are simpler in
structure than Zorula and Protococcus, and the only animals
which are simpler than Amabe, are essentially Amabw
devoid of a nucleus and contractile vesicle. Moreover, how-
ever complicated in structure one of the higher plants may
be in its adult state, when it commences its existence it is as
simple as Torula or Protococcus, or at most as Torula or Pro-
tococcus would be if it possessed a distinct nucleus; and the
whole plant is built up by the fissive multiplication of the
simple cell in which it takes its origin, and by the subsequent
growth and metamorphosis of the cells thus produced. The
like is’ true of all the higher animals. They commence as
nucleated cells, essentially similar to Amcebe, and colourless
blood-corpuscles, and their bodies are constructed by aggre-
gations of metamorphosed cells, produced by division from the
primary cell. It has been seen that Torula and Protococcvs,
similar as they are in structure, are distinguished by certain
important physiological peculiarities ; and the more compli-
cated plants are divisible into two series, one produced by the
growth and modification of cells which have the physiological
peculiarities of Zorula and contain no chlorophyll, while the

30 ELEMENTARY BIOLOGY. [v.

other, and far larger, series present chlorophyll, and have the
physiological peculiarities of Protococcus. The former series
comprises the Fungi, the latter all other plants; only a few
parasitic forms among these being devoid of chlorophyll.

The Fungi take their origin in spores, a kind of cells,
which, however much they may vary in the details of their
structure, are essentially similar to Torulew. Indirectly or
directly, the spore gives rise to a long tubular filament, which
is termed a hypha, and out of these hyphe the Fungus is
built up.

One of the commonest Moulds, the Penicillium glaucum,
which is familiar to every one from its forming sage-green
crusts upon bread, jam, eld boots, &c. affords an excellent
and easily studied example of a Fungus. When examined
with a magnifying glass, the green appearance is seen to be due,
in great measure, to a very fine powder which is detached
from the surface of the mould by the slightest touch. Beneath
this lies a felt-work of delicate tubular filaments, the hyphe,
forming a crust like so much blotting-paper, which is the
mycelium. From the free surface of the crust innumerable
hyphe project into the air and bear the green powder.
These are the aérial hyphe. On the other hand, the attached
surface gives rise to a like multitude of longer branched
hyphe, which project into the fluid in which the crust is
growing, like so many roots, and may be called the submerged
hyphe. If the patch of Penicillium has but a small extent
relatively to the surface on which it lies, multitudes of
silvery hyphe will be seen radiating from its periphery and
giving off many submerged, but few or no vertical, or sub-
aérial, branches. Submitted to microscopic examination, a
hypha is seen to be composed of a transparent wall (which
has the same ‘characters as the cell-wall of Torula) and proto-
plasmic contents, which fill the tube formed by the wall, and
present large central clear spaces, or vacuoles. At intervals,

v.] MOULDS. 31

transverse partitions, continuous with the walls of the tube,
divide it into elongated cells, each of which contains a
correspondingly elongated protoplasmic sac, or primordial
utricle. The hyphee frequently branch dichotomously; and, in
the crust, they are inextricably entangled with one another ;
but every hypha, with its branches, is quite distinct from
every other. Those aérial hyphe which are nearest the
periphery of the crust end in simple rounded extremities ; but
the others terminate in brushes of short branches, and each
of these branches, as it grows and elongates, becomes divided
by transverse constrictions into a series of rounded spores
arranged like a row of beads. The spores formed in this
manner are termed conidia. At the free end of each fila-
ment of the brush the conidia become very loosely adherent,
and constitute the green powdery matter to which re-
ference has been made. Examined separately, a contdium
is seen to be a spherical body, composed of a transparent
sac, enclosing a minute mass of protoplasm, in all essential
respects similar to a Zorula. If sown in an appropriate
medium, as for example Pasteur’s solution, with or without
sugar, the contdiwm germinates. Upon from one to four
points of its surface an elevation or bulging of the cell-wall
and of its contained protoplasm appears. This rapidly in-
creases in length, and, continually growing at its free end,
gives rise to a hypha, so that the young Penacillium assumes
the form of a star, each ray being a hypha. The hyphe
elongate, while side branches are developed from them by out-
growths of their walls; and this process is repeated by the
branches, until the hyphe proceeding from a single conidium.
may cover a wide circular area, as a patch of mycelium.
When, as is usually the case, many conidia germinate close
together, their hyphe cross one another, interlace, and give
rise to a papyraceous crust. After the hyphe have attained
a certain length, the protoplasm divides at intervals, and

32 ELEMENTARY BIOLOGY. [v.

transverse septa are formed between the masses thus divided
off from one another. But neither in this, nor in any other
Fungus, are septa formed in the direction of the length of
the hypha.

Very early in the course of the development of the
. mycelium, branches of the hyph extend downwards into the
medium on which the mycelium grows; while, as soon as the
patch has attained a certain size, the hyphe in its centre
give off vertical aérial branches, and the development of
these goes on, extending from the centre to the periphery.
The outgrowth of pencil-like bunches of branches at the end
of these takes place in the same order; and these branches,
becoming transversely constricted as fast as they are formed,
break up into conidia, which are ready to go through the
same course of development.

The conidia may be kept for a very long time in the dry
state, without their readiness to germinate being in any way
impaired, and their extreme minuteness and levity enable
them to be dispersed and carried about by the slightest
currents of air. The persistence of their vitality is subject
to nearly the same conditions of temperature as that of yeast.
Not unfrequently Zorule make their appearance, in abun-
dance, among the hyphe and conidia of Penicillium, and
appear to be derived from them; but it is still a disputed
point, whether they are so or not.

If some fresh horse-dung be placed in a jar and kept
moderately warm, its surface will, in two or three days, be
covered with white cottony filaments, many of which rise
vertically into the air, and end in rounded heads, so that they
somewhat resemble long pins. The organism thus produced
is another of the Winigl aie mould termed Mucor mucedo.

Each rounded head is a sporangium; the stalk on which
it is supported rises from one of the filaments which ramify in

* MOULDS. 33

the substance of the horse-dung, and are the hyphe. Each
hypha is, as in Penicillium, a tube provided with a tough
thickish structureless wall, which is partly composed of cel-
lulose, and is filled by a vacuolated protoplasm. In old
specimens, transverse partitions, continuous with the walls of
the hyphe, may divide them into chambers or cells. The
stalk of the sporangium is a hypha of the same structure as
the others. The wall of the sporangium is beset with minute
asperities composed of oxalate of lime, and it contains a
great number of minute oval bodies, the spures. held together
by a transparent intermediate substance. When the spo-
rangium is ripe, the slightest pressure causes its thin and
brittle coat to give way, and the spores are separated by
the expansion of the intermediate substance, which readily
swells up and finally dissolves, in water. The greater part
of the wall of the sporangium then disappears, but a little
collar, representing the remains of its basal part, frequently
adheres to the stalk. The cavity of the stalk does not com-
municate with that of the sporangium, but is separated
from it by a partition, which bulges into the cavity of the
sporangium, forming a central pillar or projection. This is
termed the columella and stands conspicuously above the
collar, when the sporangium has burst and the spores are
evacuated.

The spores are oval and consist of a sac, having the same
composition as the wall of the hypha, which incloses a
mass of protoplazm. When they are sown in an appropriate
medium, as for example in Pasteur’s solution, they enlarge,
become spheroidal, and then send out several thick prolonga-
tions. Each of these elongates, by constant growth at its
tree end, and becomes a hypha, from which branches are
given off, which grow and ramify in the same way. As
all the ramifying hyphe proceed from the spore as a centre,
their development gives rise, as in Penicillium, to a delicate

M. 3

BE: ELEMENTARY BIOLOGY. [v.

stellate mycelium. At first, no septa are developed in the
hyphe, so that the whole mycelium may be regarded as
a single cell with long and ramified processes, and the
Mucor, at this stage, is an unicellular organism. From near
the centre of the mycelium a branch is given off from a hypha,
rises vertically, and after attaining a certain length ceases to
elongate. Its free end dilates into a rounded head, which
gradually increases in size, until it attains the dimensions of
a full-grown sporangium ; and, at the same time, the proto-
plasm contained in this head becomes separated from that in
the stalk by a septum, which is curved towards the cavity of
the sporangium, and constitutes the columella. The wall of
the sporangium, thus formed, becomes covered externally
with a coat of oxalate of lime spines. As the sporangium
increases in size, its protoplasmic contents become marked out
into a large number of small oval masses, which are close
together, but not in actual contact. Each of these masses
next becomes completely separate from the rest, surrounds
itself with a cellular coat, and becomes a spore; while the pro-
toplasm not thus used up in the formation of spores, appears
to give rise to the gelatinous intermediate substance, which
swells up in water, referred to above. The walls of the spores
become coloured, and that of the sporangium gradually thins,
until it is reduced to little more than the outer crust of
oxalate of lime. The sporangium now readily bursts, and the
spores are separated by the swelling and eventual dissolution
of the gelatinous intermediate matter. Sporangia, in which
spores are produced by division of the protoplasm, are com-
monly termed ascz, and the spores receive the name of asco-
spores.

There appears to be no limit to the extent to which the
Mucor may be reproduced by this process of asexual develop-
ment of spores, by the fission of the contents of the sporang-
ium; nor does any other mode of multiplication become

vi MOULDS, 35

apparent, so long as the mould grows in a fluid medium and
is abundantly supplied with nourishment.

But when growing in nature, in such matters as horse-
dung, a method of reproduction is set up which represents the
sexual process in its simplest form. Adjacent hyphe, or parts
of the same hypha, give off short branches, which become
dilated at their free ends, and approach one another, until
these ends are applied together. The protoplasm in each
of the dilated ends becomes separated by a septum from that
of the rest of the branch ; the two cells thus formed open into
one another by their applied faces, and their protoplasmic
contents becoming mixed together, form one spheroidal mass,
to the shape of which the coalesced cell-membranes adapt
themselves. This process of conjugation evidently represents
that of sexual impregnation among higher organisms, but as
there is no morphological difference between the moditied
hyphe which enter into relation with one another, it is
impossible to say which represents the male, and which the
female, element. The product of conjugation is termed a
zygospore. Its cellulose coat becomes separated into an outer
layer of a dark blackish hue, the exosporium, and an inner
colourless layer, the endosporium. The outer coat is raised
into irregular elevations, to which corresponding elevations
of the inner coat correspond.

Placed in favourable circumstances, the zygospore does
not immediately germinate; but, after a longer or shorter
period of rest, the exosporium and the endosporium burst,
and a bud-like process is thrown out, which, usually, grows
only into a very short unbranched hypha. From this hypha
a vertical prolongation is developed, which becomes converted
into.a sporangium, such as that already described, whence
spores are produced, which give rise to the ordinary stellate
mycelium. Thus, Mucor presents what is termed an “ alter-
nation of generations”. The zygospore resulting from a

3—2

39 ELEMENTARY BIOLOGY. [v.

sexual process developes into a rudimentary mycelium, with
a single sporangium which constitutes the first generation
(A). This gives rise, by the asexual development of spores in
its sporangium, to the second generation (B), represented by
as many separate Mucores as there are spores. The second
generation (B) may give rise sexually to zygospores and so
reproduce the generation (A); but, more usually, an indefi-
nite series of generations similar to (B) are produced from
one another asexually, before (4) returns.

When Mucor is allowed to grow freely at the surface of a
saccharine liyuid, it takes on no other form than that de-
scribed; but, if it be submerged in the same liquid, the mode
of development of the younger hyphe becomes changed,
They break up, by a process of constriction, into short
lengths, which separate, acquire rounded forms, and at the
same time multiply by budding after the manner of Torule.
Coincidentally with these changes, an active fermentation is
excited in the fluid, so that this “ Mucor-Torula,” function-
ally as well as morphologically, deserves the name of ‘ yeast,’.

If the Mucor-Torula is filtered off from the saccharine
solution, washed, and left to itself in moist air, the Torule
give off very short aérial hyphee, which terminate in minute
sporangia. In these a very small number of ordinary mucor
spores is developed, but, in essential structure, both the
sporangia and the spores resemble those of normal J/ucor.

v.] MOULDS. 37

LABORATORY WORK.

J, PENICILLIUM.

Prepare some Pasteur’s fluid, and leave it exposed to the
air in saucers in a warm place: if Penicillium spores are at
hand add a few to the fluid in each saucer: if spores cannot
be obtained, the fluid, if simply left to itself, will probably
be covered with Penicilliwm in ten days or a fortnight.
Sometimes, however, the fluid will overrun with Bacteria, to
the exclusion of everything else. And very frequently other
moulds, such as Aspergillus, or Mucor, may appear instead of
or along with Penicillium.

1. NAKED-EYE CHARACTERS. Note the powdery-looking
upper surface, white in young specimens, pale greenish
in older, and later still becoming dark sage-green :
the smooth pale under surface: the dense tough
character of the mycelium.

2. HIsTOLOGICAL STRUCTURE.

a. The mycelium.

a. Tease a bit out in water, and examine first with
low, and then with a high power: it is chiefly
made up of interlaced threads or tubes—the

a. Hyphe. Note their diameter (measure)—form
—subdivisions (cells)—dichotomous mode of
branching—and structure : the external homo-
geneous sac; the granular less transparent pro-
toplasm; the small round vacuoles. Draw.

38 ELEMENTARY BIOLOGY. ly.

B. The intermixed Torule. Note their size and
number.

b. Hold a bit of the mycelium between two pieces
of carrot, and cut a thin vertical section with a
sharp razor: mount in water and examine with
low and high power.

b. The submerged hyphe.
Small branched threads hanging down from the under
surface of the mycelium: repeat the observations
2. &. a. a.

c. The aérial hyphe and conidiophores.

Tease out in water a bit from the surface of one of the
greenish patches; observe the difficulty with which
water wets it. Examine with low and high power.

Note ;—
a. The primary erect hypha.
8. Its division into a number of branches.

y. The division of the terminal branches by con-
strictions into a chain of conidia. Draw.

d. The conidia.
a. Their Stze (measure).
Form ; spherical.
Structure ; sac, protoplasm, vacuole.
b. Stain with magenta and iodine.
ce. Treat another specimen with potash.
e. The germination of the Conidia, and building up
of the Mycelium.

a. Sow some conidia in Pasteur’s fluid in a watch-glass ;
protect from evaporation, and watch the development

MOULDS. 39

of the mycelium (examine the surface with a low
power); then the formation of aérial ny pls finally
the production of new conidia.

[Sow conidia in Pasteur’s fluid in a moist chamber, and
watch from day to day; note the formation of eminences
at one or more points on a conidium; the elongation of
these eminences to form hyphe ; the branching and inter-
lacement of the hyphe. }

B. MUCOR MUCEDO.

1.

ty

4)

Place some fresh horse-dung under a bell-jar and
keep moist aud warm; in from 24 to 48 hours its
surface will nearly always be covered by a crop of
erect aérial mucor-hyphe, each ending in a minute
enlargement (sporangiunr) just visible with the un-
assisted eye: it is this first crop of hyph and spor-
anges which is to be examined.

Snip off a few of the hyphe with a pair of scissors,
mount in water, and examine with 1 inch obj.

a. Large unbranched hyphe, each ending in a
spherical enlargement (sporangzwm).

Examine with { obj.
The hyphe.

a. Their size; they greatly exceed the hyphe of
Penicillium both in length and diameter.

B. Their structure; homogeneous sac, granular
protoplasm, vacuoles: septa absent except
close to the sporange.

y. Treat with iodine and magenta; the proto-
plasm is stained.

40
6.

ELEMENTARY BIOLOGY. [v.

Treat another specimen with Schultze’s solu-
tion; the wall is stained violet.

b. The sporangia or asci.
Examine with } obj.

a.

b.

C.

Their size and form.

Their structure.

The homogeneous enveloping sac covered by
irregular masses of calcic oxalate.

The granular protoplasmic contents: un-
segmented in some; divided into a great
number of distinct oval masses (ascospores) in
others.

The projection into the sporangial cavity of
the convex septum (columella) which separates
the hypha from the sporange.

The collar projecting around the base of the
columella of burst sporangia.

Stain some with iodine; others with Schultze’s
solution.

c. The ascospores.

he

» 2 BD 8B

Crush some ripe asci by gentle pressure upon
the cover-glass. Examine with $ obj.

The size of the ascospores (measure).
Their form ; cylindrical and elongated.
Their structure.

Stain with iodine and magenta.

VI.

STONEWORTS (Chara and Nitella).

THESE water-weeds are not uncommonly found in ponds and
rivers, growing in tangled masses of a dull green colour. Each
plant is hardly thicker than a stout needle, but may attain a
length of three or four feet. One end of the stem is fixed in the
mud at the bottom, by slender thread-like roots, the other floats
at the surface. At intervals, appendages, consisting of leaves,
branches, root-filaments, and reproductive organs, are disposed
in circles, or whorls. In the middle and lower parts of the
plant these whorls are disposed at considerable and nearly
equal distances ; but, towards the free upper end, the intervals
between the whorls diminish, and the whorled appendages
themselves become shorter, until, at the very summit, they
are all crowded together into a terminal bud, which requires
the aid of the microscope for its analysis.

The parts of the stem, or aais, from which the append-
ages spring are termed nodes ; the intervening parts being
internodes. When viewed with a hand-magnifier the inter-
nodes exhibit a spiral striation.

In Chara, each internode consists of a single, much-elongat-
ed cell, which extends throughout its whole length, invested
by a cortical layer, composed of many cells, the spiral ar-
rangement of which gives rise to the superficial marking
which has been noted. And this multicellular structure
is continued from the cortical layer, across the stem, at each
node. The stem therefore consists of a series of long, axial
cells, contained in as many closed chambers formed by the

42 ELEMENTARY BIOLOGY. [VI

small cortical cells. The nodes are the multicellular parti-
tions between these chambers. The branches are altogether
similar in structure to the main stem. The leaves are
also similar to the stem, so far as they consist of axial and
cortical cells, but they differ in the form and_ proportions
of these cells, as well as in the fact that the summit,
or free end, of the leaf is always a much-elongated pointed
cell. The branches spring from the re-entering angle between
the stem and the leaf, which is termed the azilla of the
leaf; and, in the same position, at the fruiting season of
the plant are found the reproductive organs. These are of
two kinds, the one large and oval, the sporangia or spore-
fruits, the other smaller and globular, the antheridia Both,
when ripe, have an orange-red colour, and are seated upon
a short stalk.

If a growing plant be watched, it will be found that
it constantly increases in length in two ways. New nodes,
internodes, and whorls of appendages are constantly be-
coming obvious at the base of the terminal bud; and these
appendages increase in size and become more and more
widely separated, until they are as large and as far apart
as in the oldest parts of the plant. The appendages at first
consist exclusively of leaves and root-filaments (rhizords),
and it is only when these have attained their full size
that branches, epore-fruits and antheridia are developed in
their axilla. Sometimes rounded cellular masses appear in
the axillee of the leaves, and, becoming detached, grow into
new plants. These are comparable to the bulbs of higher
plants.

If the innermost part of the terminal bud, which con-
stitutes the free end of the axis, or stem, be examined,
it will be found to be formed by a single nucleated cell,
separated by a transverse septum from another. Beneath
this last follows another cell, which has already undergone

wi.) STONEWORTS. 43

division into several smaller cells by the development of
longitudinal septa. This is the most newly-formed node.
Below this again is a single cell, which is both longer and
broader than those at the apex, and is an internodal cell.
Below it follows another node, composed of more numerous
small cells than in the first. Some of the peripheral cells of
this node are undergoing growth and division, and thus give
rise to cellular prominences, which are the rudiments of the
first whorl of leaves. In the still lower parts of the stem the
internodal cells get longer and longer, but they never divide.
The nodal cells, on the other hand, multiply by division, but do
not greatly elongate. From the first, the nodal cells overlap
the internodal cell, so as to meet round its equator, and thus
completely invest it externally. And, as the internodal cell
grows and elongates, the overlapping parts of the nodes
increase in length and become divided into internodal and
nodal cells, which take on a spiral arrangement, and thus
give rise to the cortical layer.

Thus the whole plant is composed of an aggregation of
simple cells; and, while it lives, new nodes and internodes
are continually being added at its summit, or growing point.
The internodal cells which give rise to the centre of the
stem undergo no important change, except great increase
of size, after they are once formed. The nodal cells, on
the contrary, undergo division with comparatively little in-
crease in size. And out of them, the nodes, the cortical
layer, and all the appendages, are developed.

In all the young cells of Chara a nucleus of relatively
large size is to be seen imbedded in the centre of the
protoplasm, which is motionless, and is inclosed in a struc-
tureless cell-wall, containing cellulose. As the cell grows
larger, the centre of the protoplasm becomes occupied by a
watery fluid, and its thick periphery, which remains applied
against the cell-wall, constitutes the wall of a sac, or

44 ELEMENTARY BIOLOGY. [vI.

primordial utricle, mm which the nucleus is imbedded. In
the larger cells the primordial utricle is readily detached
and made to shrivel up into the middle of the cell by
treatment with strong alcohol.

Numerous small green bodies—chlorophyll grains—are
imbedded in the outer, or superficial, part of the primordial
utricle. And they increase in number by division, as the cell
enlarges. These chlorophyll grains are composed of proto-
plasmic matter, which frequently contains starch granules,
and is impregnated with the green colouring substance.

During life, the layer of the primordial utricle which
lies next to the watery contents of all the larger cells is
in a state of incessant rotatory motion, while the outermost
layer which contains the chlorophyll grains is quite still. In
the large cells, so long as the nucleus is discernible, it is
carried round with the rotating stream.

The antheridium is a globular spheroidal body with a
thick wall, made up of eight pieces, which are united by
interlocking edges. The four pieces which make up the hemi-
sphere to which the stalk of the antheridium is attached, are
foursided, the other four are triangular. From the centre of
the inner, concave face of each piece a sort of short process,
the handle or manubriwm, projects into the cavity of the
hollow sphere. At the free end of the manubrium is a
rounded body, the capitulum, which bears six smaller, second-
ary capitula ; and each secondary capitulum gives attachment
to four long filaments divided by transverse partitions into
a multitude (100 to 200) of small chambers. Thus, there
may be as many as 20,000 to 40,000 chambers in each
antheridium (8 x 6 x 4x 100 or x 200). The several pieces of
which the wall of the antheridium is composed, the manubrium,
the capitula, the secondary capitula and the chambers of the
filaments, are all more or less modified cells, as may be proved
by tracing the antheridia from their earliest condition, as

vi] STONEWORTS. 45

small processes of the nodal region, to their complete form.
The cells of the filaments are, at first, like any other cells;
but, by degrees, the protoplasm of each becomes changed into
a thread-like body, thicker at one end than at the other,
and coiled spirally like a corkscrew. From the thin end
two long cilia proceed; and, when the cells are burst, and
the antherozooids are set free, they are propelled rapidly,
with the small end forwards, by the vibration of the cilia.
These antherozooids answer to the spermatozoa of animals,
and represent the male element of the Chara.

The sporangia or spore-fruits are borne upon short stalks,
the end of which supports a large oval central cell; five
spirally disposed sets of cells invest this, an aperture being
left between the investing cells at the apex of the sporangium.
When the antheridia attain maturity they burst, the anther-
ozooids are set free, and swarm about in the water. Some
of them enter the aperture of the sporangium, and, in all
probability, pierce the free summit of the oval central cell,
and enter its protoplasm; but all the steps of this process
of impregnation have not been worked out. The result,
however, is, that the contents of the central cell become full
of starchy and oily matter; the spiral cells forming its coat
acquire a dark colour and hard texture, and the sporangium,
detaching itself, falls into the mud.

After a time, it germinates; a tubular process, like a
hypha, protrudes from its open end, and almost immediately
gives off a branch, which .is the first root (compare the
germination of the spore of a fern below). The hypha-like
tube elongates, and becomes divided transversely into cells,
the protoplasm of which developes chlorophyll. Very soon,
the further growth of this pro-embryo is arrested. But
one of the cells, which lies at some distance below the free
end of the pro-embryo, undergoes budding, and gives rise to
a set of leaves (which are not arranged in a whorl), amidst

46 ELEMENTARY BICLOGY. [VI.

which a bud appears, which has the structure of the terminal
bud of the adult Chara stem, and grows up into a new Chara.

We have then, in Chara, a plant which is acrogenous (or
grows at its summit), and which becomes segmented by the
development of appendages, at intervals, along an axis;
which multiplies, asexually by bulb-like buds, and also multi-
plies sexually by means of the antherozooids (male elements)
and central cells of the sporangia (female elements); in
which the first product of the germination of the impregnated
ovicell is a hypha-like body, from which the young Chara is
developed by the gemmation and growth of one cell; so that
there is a sort of alternation of generations, though the
alternating forms are not absolutely distinct from one another.

Chara flourishes in pond-water under the influence of
sunlight, and by the aid of its chlorophyll, so that its nu-
tritive processes must be the same as those of Protococcus,
From its complete immersion, and the absence of any duct-
like, or vascular tissues, it is probable that all parts absorb
and assimilate the nutriment contained in the water; and
that, except so far as the reproductive organs are concerned,
there is a morphological differentiation of organs, unac-
companied by a corresponding physiological differentiation.

Mitella is a rarer plant than Chara, and is simpler in
structure, its axis being devoid of the vertical layer. In
other respects, however, it is very similar to Chara, and its
structure is more easily made out.

[The Characew, or plants belonging to the genera Chara and
Nitella, are found in all parts of the world, and are in many
respects closely allied to the Alyce, or water-weeds. But no Algee
are provided with an axis and appendages possessing a similar
structure, or following the same law of growth, nor have any
similar reproductive organs. The antherozooids of the Characee
are, in fact, similar to those of the mosses, from which however
the Characee differ widely in all other respects. ]

vi] STONEWORTS. 47

LABORATORY WORK.
A. NAKED-EYE CHARACTERS.

Note the slender elongated axis (stem); the whorled
appendages (leaves); the nodes and internodes ; the shortening
of the latter towards the apex of the stem; the rhizoids.

a. The roots; small; serving chiefly for attachment,
the plant getting most of its nutrition, through
other parts, from matters dissolved in the water.

b. Lhe leaves; their sub-divisions (leaflets); their
form, size, &e.

ce. The spore-fruits and antheridia; their position,
size, form, colour.

Draw a portion including two or three internodes.
B. HISTOLOGICAL STRUCTURE,
a, The stem.

J. Examine the outside of a fresh internode with a low
power, or a pocket-lens, to see the spirally arranged
cortical cells.

1S

Hold a bit of fresh stem between two pieces of carrot,
or imbed it in paraffin, and, with a sharp razor, cut
thin transverse and longitudinal slices through nodes
and internodes. Note the cavity of the large central
cell (medullary or internodal cell) in the internodes;
the cortical cells, set on obliquely round the medullary
cell; the nodal cells, and the interruption of the central
cavity at the nodes.

we

Examine similar sections in specimens treated with
spirit, and also preparations made by teasing or press-
ing out in glycerine bits of stem from chromic-acid (0-2
per cent.) preparations: make out in these,—

ELEMENTARY BIOLOGY. : [VI

The nodal, internodal, and cortical cells.

The wall (sac), protoplasmic layer (primordial
utricle), nucleus, and vacuole of each cell. (The
nucleus, is not always to be found in old cells.)
Draw.

Examine sections from the fresh stem to make out
the points detailed in B.a.3. 8. The protoplasm and
nucleus are difficult to see. Note the chlorophyll-
granules. (See B. b. y.)

Stain sections of the fresh stem with iodine, and
magenta: note the results.

b. The leaves.

Examine fresh and chromic-acid specimens,

a.

B.

The large uncovered terminal cell.

Then a series of internodal cells, separated
from one another and covered in by nodal cells:

the sac, protoplasm, nucleus, and vacuole of
each.

The chlorophyll: collected into oval granules,
and arranged so as to leave an oblique
uncoloured band round each cell; the position
of these granules in’ the more superficial
layer of the protoplasm.

The protoplasmic movements (see C. a.).

The terminal bud.

Dissect out chromic-acid specimens as far as pos-

sible with needles, and then press gently out in
glycerine. Note in different specimens—

71.]

d.

M.

STONEWORTS. 49
a. The terminal or apical cell:

a. Its form: hemispherical, the rounded surface
free; the flat surface attached to the cell below it.

B. Structure: sac, protoplasm, nucleus; no vacuole
present.

Sometimes two nuclei; preliminary to division.

8. Its mode of division; across the long axis of
the stem, giving rise to two superimposed
nucleated cells.

b. The further fate of the new cells which are
successively segmented off from the terminal
cell; work back in your specimens from the
terminal cell.

a. The new cells are successively nodal and inter-
nodal; the latter enlarge, develope a large
vacuole, and ultimately form the medullary
cells of the internodes; they never divide.

8B. The nodal cells divide freely, and do not
increase much in size; they form the nodes, and
the cortical cells.
c. The development of leaves: by the multiplication
and outgrowth of nodal cells.
Their growth at the base, the terminal leaf-cell
soon attaining its full size and not dividing.

d. The development of branches; from nodal cells
in leaf-axils, which take on the character of ter-
minal cells.

The spore-fruits.

Examine fresh, under a low power.

ELEMENTARY BIOLOGY. [v

a. Made up externally of five twisted cells, bearin
at their apices five smaller, not twisted cells,

8. Cut sections from imbedded specimens, an
examine with a high power: make out th
large central nucleated cell; the fatty an
starchy matters contained in it; stain wit
iodine.

y. Press out chromic acid specimens in glycerine
make out the above points (d. a. 8).

6. Examine chromic acid specimens for youn;
spore-fruits, and press them out in glycerine
make out in the youngest the five roundisl
cells surrounding a central one; then in olde
specimens the elongation, and twisting of th
external cells, and the separation of their apice
as five distinct cells.

e. The Antheridia.

a. Examine, with a low power, a ripe (orange
coloured) one.

a. Make out its external dentated cells.

8. Tease out a ripe antheridium in water; an
examine with a high power; note the flat
dentated, nucleated external cells; the cylin
drical cell (manubrium) springing perpendicu
larly from the inner surface of each; th
roundish cell (capitulum) on the inner end o
the manubrium; the six secondary capitul
attached to the capitulum; the thread-lik
filaments (usually four) proceeding from ead
of the secondary capitula,

vi]

b.

B.

STONEWORTS. 51

The structure of these threads; each consists
of a single row of cells, containing in unripe
specimens nucleated protoplasm ; in older spe-
cimens each contains a coiled-up antherozooid.

The antherozooids.

Their form and structure; thickened at one
end and granular; tapering off gradually to-
wards the other end which is hyaline, and has
two long cilia attached to it.

The movements in water of ripe anthero-
zovids.

[Sometimes Chara cannot be obtained, when Nitella,

another genus of the same natural order, and of similar
habit and structure, can. Nearly all the points above
described for Chara can be made out in Nitella, with
the following differences: the cortical cells of the stem
and leaves are absent, and, in the commoner species,
the plant is not hardened by calcareous deposit; the
branches arise, not one from a whorl of leaves, but two ;
and the five twisted cells of the spore-fruit are each
capped by two small cells, instead of one.]

C. PROTOPLASMIC MOVEMENTS IN VEGETABLE CELLS.

a.

Chara. Take a vigorous-looking fresh Chara or
Nitella-cell (say the terminal cell of a leaf), and
examine it in water with a high power. Note
the superficial layer of protoplasm in which the
chlorophyll lies; it is stationary: focus through
this layer and examine the deeper one; note
the currents in it, marked by the granules they
carry along: their direction; in the long axis
of the cell, wp one side and down the other,
the boundary of the two currents being marked

4—2

'B2

ELEMENTARY BIOLOGY. [ VI.

by the colourless band, in which no movements
occur. Try to find the nucleus; it has usually
disappeared in cells in which currents have com-
menced, but when present is passive and carried
along by them. Sometimes it is very difficult,
on account of the incrustation of the leaf-cells of
Chara, to make out the protoplasmic movements
in them; if this is found to be the case, the
manubrial cells from an antheridium should be
used instead.

Tradescantia, Examine in water, with a high |
power, the hairs which grow upon the stamens:
they consist of a row of large roundish cells, each’
with sac, protoplasm, nucleus, and vacuolar
spaces. Note the protoplasm; partly forming a
layer (primordial utricle) lining the sac, and
heaped up round the nucleus, and partly forming
bridles running across the cell in yarious di-
rections from the neighbourhood of the nucleus
and from one part of the protoplasm to another;
observe the currents in these bridles; from the
nucleus in some, towards it in others.

Vallisneria, Take a leaf beginning to look old;
split it into two layers with a sharp knife and
mount a bit in water; examine with a high
power. Note the larger rectangular cells, be-
longing to the deeper layers, with well-marked
currents in them, which carry the chlorophyll
granules round and round inside the cell-wall.

If no currents are seen at first, gently warm
the leaf by immersing it for a short time in water
heated to a temperature between 30° and 35°C,

vI.]

d.

STONEWORTS. 53

Anacharis. Take a yellowish-looking leaf: mount
in water and examine with a high power; the
phenomena observed are like those in Vallisneria.
They are best observed in the single layer of cells
at the margin of the leaf.

Nettle-hair. Mount an uninjured hair in water
with the bit of leaf to which it is attached
(it is essential that the terminal recurved part
of the large cell forming the hair be not broken
off) ; examine with the highest available power ‘
currents carrying along very fine granules will be
seen in the cell, their general direction hemg
that of its long axis.

VI.

THE BRACKEN FERN (Péeris aquilina).

THE conspicuous parts of this plant are the large green
leaves, or fronds, which rise above the ground, sometimes to the
height of five or six feet, and consist of a stem-like axis or
rachis,from which transversely disposed offshoots proceed, these
ultimately subdividing into flattened leaflets, the pinnules.
The rachis of each frond may be followed for some distance
into the ground. Its imbedded portion acquires a brown
colour, and eventually passes into an irregularly branched
body, also of a dark-brown colour, which is commonly called
the root of the fern, but is, in reality, a creeping underground
stem, or rhizome. From the surface of this, numerous fila-
mentous true roots are given off. Traced in one direction
from the attachment of the frond, the rhizome exhibits the
withered bases of fronds, developed in former years, which
have died down; while, in the opposite direction, it ends,
sooner or later, by a rounded extremity beset with numerous
fine hairs, which is the apex, or growing extremity, of the
stem. Between the free end and the fully formed frond
one or more processes, the rudiments of fronds, which will
attain their full development in following years, are usually
found.

The attachments of the fronds are nodes, the spaces
between two such successive attachments, internodes. It
will be observed that the internodes do not become crowded

VII] THE BRACKEN FERN, 55

towards the free end, and there is nothing comparable to
the terminal bud of Chara with its numerous rudimentary
appendages.

When the fronds have attained their full size, the edges
of the pinnules will be observed to be turned in towards
the underside, and to be fringed with numerous hair-like pro-
cesses which roof over the groove, inclosed by the incurved
edge. At the bottom of the groove, brown granular bodies
are aggregated, so as to form a streak along each side of the
pinnule. The granules are the sporangia, and the streaks
formed by their aggregation, the sort.

Examined with a magnifying glass, each sporangium is
seen to be pouch-shaped, like two watch-glasses united by
a thick rim. When ripe, it has a brown colour, readily
bursts, and gives exit to a number of minute bodies which
are the spores. :

The plant now described is made up of a multitude of
cells, having the same morphological value as those of Chara,
and each consisting of a protoplasmic mass, a nucleus and
a cellulose wall. These cells, however, become very much
modified in form and structure in different regions of the
body of the plant, and give rise to groups of structures called
tissues, in each of which the cells have undergone special
modifications. These tissues are, to a certain extent, recog-
nizable by the naked eye. Thus, a transverse section of the
rhizome shews a circumferential zone of the same dark brown
colour as the external epidermis, inclosing a white ground
substance, interrupted by variously disposed bands, patches,
and dots, some of which are of the same dark-brown hue as
the external zone, while others are of a pale yellowish-brown.

The dark brown dots are scattered irregularly, but the
major part of the dark brown colour is gathered into two
narrow bands, which lie midway between the centre and
the circumference. Sometimes the ends of these bands are

56 ELEMENTARY BIOLOGY. [vl

united. Inclosed between these narrow, dark-brown bands
are, usually, two elongated, oval, yellowish-brown bands ;'
and outside them, lie a number of similarly coloured patches,
one of which is usually considerably longer than the others,

A longitudinal section shews that each of these patches
of colour answers to the transverse section of a band of
similar substance, which extends throughout the whole length
of the stem; sometimes remaining distinct, sometimes giving
off branches which run into adjacent bands, and sometimes
uniting altogether with them.

At a short distance below the apex of the stem, however,
the colour of all the bands fades away, and they are traceable
into mere streaks, which finally disappear altogether in the
semi-transparent gelatinous substance which forms the grow-
ing end of the stem. Submitted to microscopic examination,
the white ground substance, or parenchyma, is seen to consist
of large polygonal cells, containing numerous starch granules;
and the circumferential zone is formed of somewhat elongated
cells, the thick walls of which have acquired a dark-brown
colour, and contain little or no starch. The dark-brown bands,
on the other hand, consist of cells which are so much elongated
as almost to deserve the name of fibres and constitute what is
termed sclerenchyma. Their walls are very thick, and of
a deep-brown colour; but the thickening has taken place
unequally, so as to leave short, obliquely directed, thin places,
which look like clefts. The yellow bands, lastly, are vascular
bundles. Each consists, externally, of thick-walled, elongated,
parallel-sided cells, internal to which lie elongated tubes
devoid of protoplasm, and frequently containing air. In the
majority of these tubes, and in all the widest, the walls are
greatly thickened, the thickening having taken place along
equidistant transverse lines. The tubes have become flat-
tened against one another, by mutual pressure, so that they
are five- or six-sided; and, as the markings of their flattened

vit.] THE BRACKEN FERN, 57

walls simulate the rounds of a ladder, they have been termed
scalariform ducts or vessels. The cavities of these scalariform
ducts are divided at intervals, in correspondence with the
lengths of the cells of which they are made up, by oblique,
often perforated, partitions. Among the smaller vessels, a few
will be found, in which the thickening forms a closely wound
spiral. These are spiral vessels.

The rachis of a frond, so far as it projects above the
surface of the ground, is of a bright green colour; and, in
transverse section, it presents a green ground-substance, inter-
rupted by irregular paler markings, which are the transverse
sections of longitudinal bands of a similar colour. There are
no brown spots or bands. Examined microscopically, the
ground-substance is found to be composed of polygonal cells
containing chlorophyll. These are invested superficially by
an epidermis, composed of elongated cells, with walls thick-
ened in such a manner as to leave thin circular spots here
and there. Hence, those walls of the cells, which are at
right angles to the axis of vision, appear dotted with clear
spots; while, in those walls of which transverse sections are
visible, the dots are seen to be funnel-shaped depressions.

The pale bands are vascular bundles containing scalari-
form and spiral vessels. The outer layer investing each
is chiefly formed of long hollow fibres with very thick
walls, and terminating in a point at each end. These scleren-
chymatous fibres have oblique cleft-like clear spaces, pro-
duced by interruptions of the process of thickening in their
walls.

The vascular bundles, the green parenchyma, and the
epidermis are continued into each pinnule of the frond.
The epidermis retains its ordinary character on the upper
side of the pinnule, except that the contours of its component
cells become somewhat more irregular. On the under side,
many hairs are developed from it, and the cells become

ns ELEMENTARY BLOLOGY, [var

stnetlarly moditied tn form, their walls being thrown oul
tito Tobes, whieh interlock with Chose of adjacent cells,

Between many of these cells an oval space is left, forming
a channel of communication between the titerior of the
frond and the exterior, ‘Phe opening of this space is) sar
mounted by two rentform cells, the coneaviltes of whieh
are darned towards one another, while ther ends are in
coutaet. The opening tefl between the applied concave
Fhees is ak sfomate; and, as the sfometes are present in
Immense iimbers, there is a free commatiniention between
the outer air and the dafercedfadar passages which exist
in the substinee of the frond. Phase cells af the green
parenchyma of the frond whieh form the iaferior half of its
thickness, tn thet, are irregularly elongated, and) frequently
produced: inte several processes, or stellate, hey come into
contied with adjacent: cells only by comparatively small
parts oof there stafaees, or by ¢ho ends of these processes,
They thus bound) passages between the eelks, difercedlutay
passages, Which are full of air, and are in commotntention
with strihay, bat narrower, passives, which extend through-
out Che substunce of the plant,

The vascular bundles break up in the pinnules, and
follow the course of the so ealled vevus which are visible
Upon Tis surties ; duets being continued: ito their ultimate
ramitien ions,

The rootlets prosent an outer coat of epidermis, enclosing
petrenchy mia traversed by ac eentral vascular bundle. ‘They
inerease Tn leneth by the division and subdivision of the
eolls at the growing point, but this potat is net situated ab
the very surfiee of the rootlet, as the growing poi at the
evCremiby of the rhizonie isy butts covered hy a eap of eclls.

When the spores ave sown tpen danip earth, ora tile,
or aoship oof vhiss, and hopt thoroughly moist and warm, they

germinate, Hach gives rise bon tubular, hy phaclike, prolongs.

VIL] THE BRACKEN FERN. 59

tion, which developes a similar process, the primitive rootlet,
close to the spore. The hypha-like prolongation, at first,
undergoes transverse division, so that it becomes converted
into a series of cells. Then, the cells at its free end divide
longitudinally, as well as transversely, and thus give rise to
a flat expansion, which gradually assumes a bilobed form, and
becomes thickened, in some parts, by division of its cells in
a direction perpendicular to its surface. The protoplasm of
these cells developes chlorophyll granules, whereby the bilobed
disk acquires a green colour; while numerous simple radicle
fibres are given off from its under surface, and attach the
little plant, which is termed a prothallus or prothallium, to
the surface on which it grows.

The prothallus attains no higher development than this,
and does not directly grow into a fern such as that in which
the spores took their origin; but, after a time, rounded or
ovoidal elevations are developed, by the outgrowth and division
of the cells which form its under aspect. Some of these are
antheridia. The protoplasm of each of the cells contained in
their interior is converted into an antherozooid, somewhat
similar to that of Chara, but provided with many more cilia.
The antheridium bursts, and the antherozooids, set free from
their containing cells, are propelled through the moisture
on the under surface of the prothallus by their cilia.

The processes of the second kind acquire a more cylin-
drical form, and are called archegonia. Of the cells which
are situated in the axis of the cylinder, all disappear but that
which lies at the bottom of its cavity. This is the embryo
cell, and when the archegonium is fully formed, a canal leads
from its summit to this cell. The antherozooids enter by
this canal, and impregnate the embryo cell.

The embryo cell now begins to divide, and becomes
converted into four cells; of these, the two which lie at the
deepest part of the cavity of the archegonium subdivide and

60 ELEMENTARY BIOLOGY. [ VII.

ultimately form a plug-like, cellular, mass, which imbeds itself
firmly in the substance of the prothallus. Of the remaining
two cells, which also undergo subdivision, one gives rise to the
rhizome of the young fern, while the other becomes its first
rootlet. It appears probable that the plug-like mass absorbs
nutritive matter from the prothallus, and supplies the rhizome
of the young fern, until it is able to provide for itself. As
the rhizome grows, and developes its fronds, it rapidly attains
a size vastly superior to that of the prothallus, which at
length ceases to have any functional importance, and dis-
appears.

Thus Pterts presents a remarkable case of the alternation
of generations. The large and complicated organism com-
monly known as the “Fern” is the product of the impreg-
nation of the embryo cell by the antherozooid. This “ Fern,”
when it attains its adult condition, developes sporangia; and
the inner cells of these sporangia give rise, by a perfectly
asexual fissive process, to the spores. The spores when set
free germinate; the product of that germination is the incon-
spicuous and simply cellular prothallus; an independent
organism, which nourishes itself and grows, and on which,
eventually, the essential organs of the sexual process—the
archegonia and antheridia—are developed.

Each impregnated embryo cell produces only a single
“fern,” but each “fern” may give rise to innumerable pro-
thallia, seeing that every one of the numerous spores de-
veloped in the immense multitude of sporangia to which the
frond gives rise, may germinate.

vit] THE BRACKEN FERN. 61.

LABORATORY WORK.

A. THE FERN-PLANT ; ASEXUAL GENERATION,

a, External characters.
a. The brown underground stem or rhizome: its
nodes and internodes,
b. The roots springing from the rhizome.
c. The leaves or fronds arising from the rhizome at
intervals.

a. The great amount of subdivision of the frond:
its main axis (rachis) ; the primary divisions or
pinne ; the ultimate divisions or pinnules.

8. The sori; small brown patches along the mar-
gin of the under surface of some of the pin-
nules,

d, The nodes and internodes of the rhizome. The
absence of a terminal bud on it.

b. The rhizome.

1. Cut it across and draw the section as seen with the
naked eye.

a. The outer brownish layer (epidermis and sub-
epidermis.)

b. The yellowish-white substance (parenchyma) form-
ing most of the thickness of the section.

c. The internal incomplete brown ring (sclerenchyma)
imbedded in the parenchyma.

d. The small patches of sclerenchyma scattered
about in the parenchyma outside the main
sclerenchymatous ring.

19

é.

ELEMENTARY BIOLOGY. [VII

The yellowish tissue (vascular bundles) lying inside
and outside the ring of sclerenchyma.

Cut a longitudinal section of the rhizome: make out
on the cut surface b. 1. a. bc. dd.

Cut a thin transverse section of the rhizome, mount
in water and examine with 1 inch obj.

a

d.

The single layer of much thickened epidermic
cells,

The small opaque angular contours of the sub-
epidermic cells (external sclerenchyma).

The large polyhedral more transparent paren-
chymatous cells.

The small opaque angular contours of the cells of
the internal sclerenchyma,

The great openings of the ducts and vessels in the
fibro-vascular bundles.

Draw the section.

Examine with } obj.

a.

b.

a.

The epidermis : its thick-walled cells.

The parenchyma : its large thin-walled cells: their
sac, protoplasm and nucleus: the great number of
starch granules in them.

The various patches of sclerenchyma, made up of
thick-walled angular cells.
The vascular bundles. Note in each:—

Outside, a single layer of cells containing no
starch-granules (sheath-cells).

Vit]

or

é.

THE BRACKEN FERN. 63

Within the sheath-cells a layer of small paren-
chymatous cells containing starch.

Within the last layer come the bast-cells ; small
rectangular cells with slightly thickened walls,
and arranged in several rows.

Within the bast layer, come one or more rows
of larger thin-walled cells,

The cross sections of the vessels: their greatly
thickened walls, and large central cavity con-
taining no protoplasm.

Scattered here and there, in the spaces between
the angles of the vessels, are small parenchyma-
tous cells containing starch-granules.

Treat with iodine: the protoplasm stained brown ;
the starch-granules deep blue, rendering some of
the cells quite opaque and almost black-looking.

Cut a thin longitudinal section of the stem and
examine with 1 inch and then with $ obj. Make out
the various tissues described in 3 and 4,

a.

The epidermis and parenchyma, much as in the
transverse section.

The sclerenchyma is seen to be made up of greatly
elongated cells, tapering towards each end.

The vascular bundles ; note in them—

The sheath-cells and parenchyma much as in
the transverse section.

The vessels: elongated tubes presenting cross
partitions at long intervals. Two forms of
vessel will be seen, viz. scalariform vessels,

ELEMENTARY BIOLOGY. {vir

with regular transverse thickenings on their
walls and spiral vessels, less numerous than the
last form: with a continuous spiral thickening
on their walls.

y. The bast-cells: seven or eight times as long as
they are broad, and terminating obliquely at
each end.

6. The elongated larger cells (4. d. 6.): they have
very slightly thickened walls and no scalariform
markings.

[Cut off half an inch of the growing end of the stem, imbed
it in paraffin upside down, and cut a series of transverse
sections: examine them with the microscope, beginning with
those farthest from the growing point. At first the various
tissues described in 3 and 4 will be readily recognisable ; as
the sections nearer the growing point are examined they
will be less distinct, and close to the growing point the
whole section will be found to be composed entirely of
parenchymatous closely fitting cells.]

[c. The leaf. Imbed a leaf in paraffin and cut a thin
vertical section: examine with 1 inch obj. It will be
found to be constructed essentially on the same plan as
the leaf of the bean. (VIIT.)]

d. The reproductive organs.

Examine a sorus with 1 inch obj. without a cover-glass.
It is composed of a great number of minute oval bodies,
the sporangia.

Scrape off some sporangia and mount in water: ex-
amine with 1 inch obj.

a. Their form: they are oval biconvex bodies borne
on a short stalk.

I1.] THE BRACKEN FERN. 65

b. Their structure: composed of brownish cells, one
row of which has very thick walls, and forms a
marked ring (annulus) round the edge of the
sporange.

c. Their mode of dehiscence (look out for one that
has opened): by a cleft running towards the
centre of the sporange from a point where the
annulus has torn across,

8. Burst open some sporangia by pressing on the cover-
glass: examine with } obj. the spores which are set free.
a. Thetr size: measure.
b. Their form: somewhat triangular.
[c. Lhetr structure ; a thick outer coat, a thin inner coat,
protoplasm, and a nucleus: crush some by pressure
on the cover-glass. |

3. THE PROTHALLUS; SEXUAL GENERATION.

Prothalli may be obtained by sowing some spores on a
lass slide, and keeping them warm and very moist for about
hree months. They are small deep green leaf-like bodies.

a. The Prothallus.

1. Transfer a prothallus to a slide, and mount it in water
with its under surface uppermost. Examine with
1 inch obj.
a. Its form: a thin kidney-shaped expansion from
which, especially towards its convex border, a
number of slender filaments (rootlets) arise.

b. Its structure.

a. The leafy expansion: it consists throughout
most of its extent of a single layer of. polyhe-
5

66

i;

ELEMENTARY BIOLOGY. [vir

dral chlorophyll-containing cells, but at parts
it is more than one cell thick.

B. The rootlets: composed of a series of cells

which contain no chlorophyll.
The antheridia and archegonia: these can just be
seen with an inch objective as minute eminences
on the under surface of those parts of the
prothallus which consist of several layers of
cells.

b. The reproductive organs.
These are to be found by examining the under surface of
the prothallus with $ obj.

The antheridia. Most numerous near and among the

rootlets.

a.

b.

Their form: small hemispherical eminences.

Their structure: made wp of an outer layer
of cells containing a few chlorophyll-granules
and through which can be seen a number of
smaller cells which occupy the centre of the organ:
in the latter cells, in ripe antheridia, spirally
coiled bodies (antherozooids) can be indistinctly
seen.

The antherozooids.

Some of these are sure to be found swimming about in
the water if a number of ripe prothalli are examined.

a.

Small bodies, coiled like a corkscrew, thick at
one end, and tapering towards the other, which
has a number of cilia attached to it. To the —
thicker end of the antherozooid is often attached
a rounded mass containing colourless granules.

Treat with iodine; this stains them and stops

ft

THE BRACKEN FERN. 67

their movements so that their form can be more
distinctly seen.

3. The archegonia. Most numerous towards the concave
border of the prothallus.

a.

Their form: chimney-shaped eminences with a
small aperture at the apex.

Their structure: composed of a layer of trans-
parent cells, containing no chlorophyll, arranged
in four rows, and surrounding a central cavity
which extends into the cushion formed by the
thickened part of the prothallus (a. 1. 6. a). In
this cavity lies, in young specimens, a large
nucleated granular basal cell, with two or three
smaller granular cells above it in the narrow
upper part of the cavity; in older specimens this
upper part is empty, forming a canal leading
down to the basal cell.

4, Examine young Fern in connexion with its prothallus.

VITI.

THE BEAN-PLANT. (Vicia faba.)

In this, which is selected as a convenient example of a
Flowering Plant, the same parts are to be distinguished as in
the Fern; but the axis is erect and consists of a root imbedded
in the earth and a stem which rises into the air. The
appendages of the stem are leaves, developed from the op-
posite sides of successive nodes; and the internodes become
shorter and shorter towards the summit of the stem, which
ends in a terminal bud. Buds are also developed in the axils
of the leaves, and some of them grow into branches, which
repeat the characters of the stem; but others, when the
plant attains its full development, grow into stalks which
support the flowers; each of which consists of a calyx, a
corolla, a staminal tube and a central pistil; the latter
is terminated by a style, the free end of which is the stigma.

The staminal tube ends in ten filaments, four of which
are rather shorter than the rest; and the filaments bear oval
bodies, the anthers, which, when ripe, give exit to a fine
powder, made up of minute pollen grains. The pistil is
hollow ; and, attached by short stalks along the ventral side
of it, or that turned towards the axis, is a longitudinal series
of minute bodies, the ovules. Each ovule consists of a central
conical nucleus, invested by two coats, an outer and an inner.
Opposite the summit of the nucleus, these coats are per-
forated by a canal, the micropyle, which leads down to the

1] THE BEAN-PLANT, 69

icleus. The nucleus contains a sac, the embryo sac, in
hich certain cells, one of which is the embryo cell, and
ie rest endosperm cells, are developed. A pollen grain
»posited on the stigma, sends out a hypha-like prolongation,
ie pollen tube, which elongates, passes down the style, and
ventually reaches the micropyle of an ovule. Traversing
1e micropyle, the end of the pollen tube penetrates the
ucleus, and comes into close contact with the embryo sac.
‘his is the process of impregnation, and the result of it
; that the embryo cell divides and gives rise to a cellular
mbryo. This becomes a minute Bean-plant, consisting of a
adicle or primary root; of two, relatively large, primary
saves, the cotyledons; and of a short stem, the plumule, on
‘hich rudimentary leaves soon appear. The cotyledons now
aerease in size, out of all proportion to the rest of the em-
ryonic plant; and the cells of which they are composed be-
ome filled with starch and other nutritious matter. The
cleus and coats of the ovule grow to accommodate the en-
arging embryo, but, at the same time, become merged into an
nvelope which constitutes the coat of the seed. The pistil
nlarges and becomes the pod; this, when it has attained its
ull size, dries and readily bursts along its edges, or decays,
etting the seeds free. Each seed, when placed in proper con-
litions of warmth and moisture, then germinates. The cotyle-
lons of the contained embryo swell, burst the seed coat, and,
yecoming green, emerge as the fleshy seed leaves. The nutri-
jous matters which they contain are absorbed by the plumule
ind radicle, the latter of which descends into the earth and
yecomes the root, while the former ascends and becomes the
stem of the young bean-plant. The apex of the stem retains,
chroughout life, the simply cellular structure which is, at
Grst, characteristic of the whole embryo; and the growth
n length of the stem, so far as it depends on the addition of
iew cells, takes place chiefly, if not exclusively, in this part.

70 ELEMENTARY BIOLOGY. [vin

The apex of the root, on the other hand, gives rise to
a root-sheath, as in the Fern.

The leaves cease to grow by cell multiplication at their
apices, when these are once formed, the addition of new cells
taking place at their bases.

The tissues which compose the body of the Bean-plant
are similar, in their general characters, to those found in the
Fern, but they differ in the manner of their arrangement.
The surface is bounded by a layer of epidermic cells, within
which, rounded or polygonal cells make up the ground-
substance, or parenchyma, of the plant, extending to its
very centre in the younger parts of the stem and in the root;
while, in the older parts of the stem, the centre is occupied
by a more or less considerable cavity, full of air. This cavity
results from the central parenchyma becoming torn asunder,
after it has ceased to grow, by the enlargement of the
peripheral parts of the stem. Nearer to the circumference
than to the centre, lies a ring of woody and vascular tissue,
which, in transverse sections, is seen to be broken up into
wedge-shaped bundles, by narrow bands of parenchymatous
tissue, which extend from the parenchyma within the circle
of woody and vascular tissue (medulla or pith) to that which
lies outside it. Moreover each bundle of woody and vascular
tissue is divided into two parts, an outer and an inner,
by a thin layer of small and very thin-walled cells, termed
the cambium layer. What lies outside this layer belongs
to the bark and epidermis ; what lies inside it, to the wood
and pith.

The great morphological distinction between the axis
of the Bean and that of the Fern lies in the presence of
this cambium layer. ~The cells composing it, in fact, retain
their power of multiplication, and divide by septa parallel
with the length of the stem, or root, as well as transverse to it.
Thus new cells are continually being added, on the inner side

71t1.] THE BEAN-PLANT. aL

f the cambium layer, to the thickness of the wood, and on
the outer side of it, to the thickness of the bark; and the
wxis of the plant continually increases in diameter, so long as ,
ihis process goes on. Plants in which this constant addition
io the outer face of the wood and the inner face of the bark
iakes place, are termed exogens.

At the apex of the stem, and at that of the root, the
rambium layer is continuous with the cells which retain
ihe capacity of dividing in these localities. As the plant is
chickest at the junction of the stem and root, and diminishes
ihence to the free ends, or apices, of these two structures,
ihe cambium layer may be said to have the form of a double
sone. And it is the special peculiarity of an exogen to possess
his doubly conical layer of constantly dividing cells, the upper
md of which is free, at the growing point of the terminal
yud of the stem, while its lower end is covered by the root-
‘ap of the ultimate termination of the principal root.

The most characteristic tissues of the wood are dotted
lucts and spiral vessels, the spiral vessels being particularly
vbundant close to the pith. The bark contains elongated
tber or bast cells; but there are no scalariform vessels such
is are found in the Fern.

Stomates are absent in the epidermis of the root: they
we to be found, here and there, in the epidermis of all the
rreen parts of the stem and its appendages, but, as in the
Tern, they are most abundant in the epidermis of the under
ide of the leaves. As in the Fern, they communicate with
ntercellular passages, which are widest in the leaves, but
‘xtend thence throughout the whole plant.

The difference between a flowering plant, such as the
3ean, and a flowerless plant, such as the Fern, at first sight
\ppears very striking, but it has been proved that the two are
yut the extreme terms of one series of modifications. The

72 ELEMENTARY BIOLOGY. [Vio

anther, for example, is strictly comparable to a sporangium.
The pollen grains answer to the male spores of those flower-
less plants in which the spores are of distinct sexes—some
spores giving rise to prothallia which develope only anthe-
ridia, and others to prothallia which develope only arche-
gonia; instead of the same prothallia producing the organs
of both sexes, as in Pteris. And the pollen tube corresponds
with the first hypha-léke process of the spore. But, in the
flowering plants, the protoplasm of the pollen tube does not
undergo division and conversion into a prothallus, from which
antheridia are developed, giving rise to detached fertilizing
bodies or antherozooids, but exerts its fertilizing influence
without any such previous differentiation. The connecting
links between these two extreme modifications are furnished,
on the one hand, by the Conifers, in which the protoplasm
of the pollen tube becomes divided into cells, from which,
however, no antherozooids are developed; and the Club-
mosses, in which the protoplasm of the male spores (= pollen
grains) divides into cells which form no prothallus, but give
rise directly to antherozooids.

On the other hand, the embryo sac is the equivalent of a
female spore: the endosperm cells, which are produced from
part of its protoplasm, answer to the cells of a prothallus;
while the embryo cell of the flowering plant corresponds
with the embryo cell contained in the archegonium of the
prothallus. In the development of the female spore of the
flowering plant, therefore, the free prothallus and the arche-
gonia are suppressed. Here again, the intermediate stages
are presented by, the Conifers and the Club-mosses. For,
in the Conifers, the protoplasm of the embryo sac gives
rise to a solid prothallus-like endosperm, in which bodies
called corpuscula, which answer to the archegonia, are formed;
and in these the embryo cells arise; while, in some of the
Club-mosses, there are female spores distinct from the male

VIII] THE BEAN-PLANT. 73

spores, and the prothallus which they develope does not
leave the cavity of the spore, but remains in it like an
endosperm.

The physiological processes which go on in the higher
green plants, such as the Fern and the Bean, resemble, in the
gross, those which take place in Protococcus and Chara.
For such plants grow and flourish if their roots are im-
mersed in water containing a due proportion of certain
saline matters, while their stem and leaves are exposed
to the air, and receive the influence of the sun’s rays.

A Bean-plant, for instance, may be grown, if supplied
through its roots with a dilute watery solution of potassium
and calcium nitrate, potassium and iron sulphate, and mag-
nesium sulphate. While growing, it absorbs the solution, the
greater part of the water of which evaporates from the ex-
tensive surface of the plant. In sunshine, it rapidly decom-
poses carbonic anhydride, fixing the carbon, and setting free
the oxygen; at night, it slowly absorbs oxygen, and gives off
carbonic acid; and it manufactures a large quantity of pro-
tein compounds, cellulose, starch, sugar and the like, from
the raw materials supplied to it.

It is further clear that, as the decomposition of carbonic
anhydride can take place only under the combined influences
of chlorophyll and sunlight, that operation must be con-
fined, in all ordinary plants, to the tissue immediately be-
neath the epidermis in the stem, and to the leaves. And
it can be proved, experimentally, that fresh green leaves
possess this power to a remarkable extent.

On the other hand, it is clear that, when a plant is grown
under the conditions described, the nitrogenous and mineral
sonstituents of its food can reach the leaves only by passing
from the roots, where they are absorbed, through the stem
to the leaves. And, at whatever parts of the plant the nitro-

74 ELEMENTARY BIOLOGY. [VIII

genous and mineral constituents derived from the roots are
combined with the carbon fixed in the leaves, the resulting
compound must be diffused thence, in order to reach the
deep-seated cells, such for instance as those of the cambium
layer and those of the roots, which are growing and multi-
plying, and yet have no power of extracting carbon directly
from carbonic anhydride. In fact, those cells which contain
no chlorophyll, and are out of the reach of light, must live
after the fashion of Toruda; and manufacture their protein
out of a material which contains nitrogen and hydrogen,
with oxygen and carbon, in some other shape than that of
carbonic anhydride. The analogy of Torula suggests a fluid
which contains in solution, either some ammoniacal salt com-
parable to ammonium tartrate, or a more complex compound
analogous to pepsin. Thus, the higher plant combines within
itself the two, physiologically distinct, lower types of the
Fungus and the Alga.

That some sort of circulation of fluids must take place
in the body of a plant, therefore, appears to be certain, but
the details of the process are by no means clear. There is
evidence to shew that the ascent of fluid from the root to
the leaves takes place, to a great extent, through the elon-
gated ducts of the wood, which not unfrequently open into
one another by their applied ends, and, in that way, form
very fine capillary tubes of considerable length.

The mechanism by which this ascent is effected is of two
kinds; there is a pull from above, and there is a push from
below. The pull from above is the evaporation which takes
place at the surface of the plant, and especially in the air
passages of the leaves, where the thin-walled cells of the
parenchyma are surrounded, on almost all sides, with air,
which communicates directly with the atmosphere through
the stomates. The push from below is the absorptive action
which takes place at the extremities of the rootlets, and

vilt.] THE BEAN-PLANT, 75

which, for example, in a vine, before its leaves have grown
in the spring, causes a rapid ascent of fluid (sap) absorbed
from the soil. A certain portion of the fluid thus pumped |
up from the roots to the surface of the plant doubtless
exudes, laterally, through the walls of the vessels (the thin
places which give rise to the dots on the walls of these
structures, especially favouring this process), and, passing
from cell to cell, eventually reaches those which contain
chlorophyll. The distribution of the compound containing
nitrogen and carbon, whatever it may be, which is formed
in the chlorophyll-bearing cells, probably takes place by
slow diffusion from cell to cell.

The supply of air, containing carbonic anhydride, to the
leaves and bark is effected by the abundant and large air
passages which exist between the cells in those regions.
But it can hardly be doubted that all the living protoplasm
of the plant undergoes slow oxidation, with evolution of
carbonic anhydride; and that this process, alone, takes place
in the deeper seated cells. The supply of oxygen needful
for this purpose is sufficiently provided for, on the one hand,
by the minute air passages which are to be found between
the cells in all parenchymatous tissues; and on the other, by
the spiral vessels, which appear always to contain air under
normal circumstances, in the woody bundles. The replace-
ment of the oxygen of the air thus absorbed, and the removal
of the carbonic anhydride formed, will be sufficiently provided
for by gaseous diffusion.

From what has been said, it results that, in an ordinary
plant, growing in damp earth and exposed to the sunshine,
a current of fluid is setting from the root towards the surface
exposed to the air, where its watery part is for the most
part evaporated; while gaseous diffusion takes place, in the
contrary direction, from the surface exposed to the air,
through the air passages and spiral vessels which extend

76 ELEMENTARY BIOLOGY. [vir

from the stomates to the radicles; the balance of exchange
being in favour of oxygen, in all the chlorophyll-bearing
parts of the plant which are reached by the sunlight, and in
favour of carbonic anhydride, in its colourless and hidden
regions, At night, the evaporation diminishing with the
lowering of the temperature, the ascent of liquid becomes
. very slow, or stops, and the balance of exchange in the air
passages is entirely in favour of carbonic anhydride; even
the chlorophyll-bearing parts oxydizing, while no carbonic
anhydride is decomposed.

LABORATORY WORK.

a. General characters.

a. The erect central main axis (root and stem).

The branches : some, mere repetitions of the main
axis; others, modified and bearing flowers.

The nodes and internodes.
d. The appendages.
a. Rootlets.
8. Foliage leaves.

y. Floral leaves.

b. The root.

a. Its main central portion (axis).

b. The irregularly arranged rootlets attached to the
axis.

c. The absence of chlorophyll in the root.

voit]

Cc.

THE BEAN-PLANT. 77

The root-sheath, covering the tip of each rootlet:
this is difficult to get whole out of the ground in
the bean, but is readily seen by examining the
roots of duckweed (Lemna) with 1 inch obj. In
the latter plant it consists of several layers of
cells forming a cap on the end of the root, and

ending abruptly with a prominent rim some way
up it.

The stem.

Erect, green, four-cornered with a ridge at each angle ;

not woody; the gradual shortening of the internodes
towards its apex.

Cut a thin transverse section of the stem, through an
internode ; note its central cavity, and the whitish ring
of fibro-vascular bundles in it, which is harder to

cut than the rest: mount in water and examine with
1 inch obj.: note—

a.

The medullary or pith-cavity in the centre of the
section.

The pith-cells, around the central cavity: large
and more or less rounded (parenchyma) : some-
times with dotted walls from spots of local thin-
ness on them.

The epidermis: composed of a single layer of
somewhat squarish-looking cells, containing no
chlorophyll.

Beneath the epidermis several layers of large

rounded cells containing chlorophyll (parenchyma
of the bark).

The medullary rays: radiating rows of paren-
chymatous cells uniting 6 and d: not quite con-

78

ELEMENTARY BIOLOGY. [ VIII,

tinuous, being interrupted by the cambium zone
(Ff ¥)-
The fibro-vascular bundles, lying between the
medullary rays; commencing at the side nearest
the pith, note—
The large openings formed by the transverse
sections of the spiral vessels and ducts.
The small thick-walled wood-cells, wedged in
between the vessels.

The cambium zone; granular-looking, and
composed of small angular thin-walled cells.

The kber-layer: in cross section it seems
composed of rounded cells with much thickened
walls. Draw the section.

Cut a transverse section through a node, and compare
it with that through the internode.

Cut a thin longitudinal section through part of an
internode (if necessary the bit of stem may be im-
bedded in paraffin first), and mount it in water;
working from the medullary cavity outwards, note the
following layers, using at first a low power.

a

The pith-cells: much as in the transverse sec-
tion.

The spiral vessels: elongated tubes with a spiral
thickening on their walls.

The wood-cells: elongated and with much thick-
ened walls.

The dotted ducts: much like b, but the thickening
not deposited in the form of a spiral.

7III.] THE BEAN-PLANT. 79

e. Thecambium zone: made up of cloudy-looking,
small, angular, thin-walled cells.

fj. Laber-cells; fusiform and thick-walled.
g. More parenchymatous cells: containing chloro-
phyll.

h. Epidermis: composed apparently of cubical
colourless cells: here and there the opening of a
stomate (d. 4. 8.) may be seen,

Draw the section.

5. Compare the transverse and longitudinal sections
together, making out the corresponding parts in each.

6. Put on a high power, and examine each of the above-
mentioned tissues carefully.

7. Stain with iodine: note the cell-walls ; the protoplasm
—its presence or absence, and relative quantity in
the various tissues; the swceler of the cells; starch-
granules in some, stained deep blue by the iodine.

d. The leaves.

1. Their form and composition.

a. Each leaf consists of a number of different parts,
VIZ.—

a. The stalk or petiole.

The four to six oval leaflets attached laterally
to the stalk.

y. The pair of small leaf-like expansions (stipules)
at the base of the petiole,

§. The rudimentary tendril terminating the pe-
tiole,

80

ELEMENTARY BIOLOGY. [ VIII.

2. The histological structure of a leaflet. 6

a.

C.

g,

Imbed a leaflet in paraffin or hold it hetween two
bits of carrot or turnip and cut a thin section
from it, perpendicular to its surfaces. Let the
section lie in water a few minutes to drive the
air out of its intercellular spaces, and then mount
it in water, and examine with 1 inch objective.

Begin at the upper surface (marked out by its
more closely packed cells), and work through to
the lower. Note—

The colourless epidermic layer—consisting of
a single row of cells; the openings here and
there in it (stomata).

Beneath the upper epidermis come elongated
chlorophyll-containing cells, set on perpendicu-
larly to the surface.

Then come irregularly branched (stellate) cells
forming the lower half of the leaf-substance;
these also contain chlorophyll.

The epidermic layer of the lower surface;
like a.

The intercellular spaces, through the whole
thickness of the leaf: the direct communication
of some of them with stomata.

Here and there sections of ribs or veins : make
out in them the same elements as in c. 2. f.

Draw.

Treat with iodine: make out the sac, proto-
plasm (primordial utricle), nucleus and vacuole
of the cells: the starch-granules.

11]

THE BEAN-PLANT. 81

d. Peel off a strip of epidermis from a leaf and ex-

amine with a low power: note—

The large close-fitting cells, with irregularly
wavy margins and no chlorophyll, which chiefly
make up the epidermis.

The openings here and there in it (stomata) ;
the two curved, chlorophyll-containing cells
bounding each stomate.

Gently pull a midrib in two across its long axis;
note the fine threads uniting the two broken
ends; cut them off with a sharp pair of scissors,
mount in water and examine with 4 or 4 ob-
jective: they will be found to consist of partially
unrolled spiral vessels.

e. The flower.

1. Its general structure.

a. Borne on a short stalk (peduncle).

b. Composed of four rows or whorls of organs.

a.

B.

Yy-
é

The external green cup-like calya.

Inside the calyx the corolla: the most con-
spicuous part of the flower.

Inside the corolla the stamens.
Within the stamens the pistil.

2. The calyx.
A cup terminated at its free edge by five prominent
points, two dorsal, and three ventral: the five small
midribs running along it (one to the end of each of
the points) represent the free ends of five sepals,
which are united below,

6

82.

ELEMENTARY BIOLOGY. [Vii

3. The corolla.

a

YY

Composed of five pieces or petals.
On the dorsal side, a single large piece (veail-
lum) expanded at its free end and folded over
the rest.

On the sides, two oval pieces (the alc), each
attached by a distinct narrowed stalk (unguis),

The inferior part of the corolla (carina), com-
posed of two oval pieces united along their
lower edge but readily tearing apart.

4, The stamens.

a.

Ten in number, each consisting of a stalk-like
part, the filament, terminated by a small knob,
the anther.

The union of the filaments for three-fourths of
their length to form the stamen-tube: the. sharp
bend of the filaments towards the upper side at
the point where they separate from one another,

Tease out an anther in water and examine with
4 obj.: there will be found numerous—

Pollen-grains: small oval bodies, with pro-
jections on them in the equatorial region.

The anther of a bean is so small that sections
cannot be made of it without considerable skill:
the structure of an anther can however be easily
made out by imbedding one from a tiger-lily in
paraffin or holding it between two bits of carrot,
cntting transverse sections, mounting in: water
and examining with 1 inch obj.

THE BEAN-PLANT. 83

It contains four chambers, two on each side of
the continuation of the filament, and in each
chamber lie numerous pollen-grains.

5. The pistil.

a.

It is found by tearing open the stamen-tube: it
is a long green tapering body, somewhat flattened
laterally and ending in a point (the style)
which bears a tuft of strong hairs.

Slit it open carefully: in it lies a central cavity,
containing a number of small oval bodies, the
ovules, attached along its ventral side by short
pedicles.

It is difficult to get a section of a bean-ovule, but
its essential structure may be readily made out
by making thin transverse sections of the ovary
of a large lily (where the ovules are closely im-
bedded in a large quantity of parenchyma) and
examining with 1 inch obj.

The central cellular portion of the ovule
(nucleus) made up of a large number of cells,

Its two coats, an inner (primine) and outer
(secundine).

The small passage (micropyle) leading through
the coats down to the nucleus.

In some specimens, a large cavity (the embryo-
sac) will be seen in the nucleus just opposite
the micropyle. In the embryo-sac may be
seen some small granular cells (the embryo-

cell and endosperm cells).
6—2

84

ELEMENTARY BIOLOGY. [viit.

f. The seeds.

Soak some dried beans in water for twenty-four hours ;
they will slightly swell up and be more readily ex-
amined than when dry.

a. Note the black patch on one end of the bean,
' marking where the stalk (funiculus) which fixed
it in the pod was attached to it.

b. Having wiped all moisture off the bean gently
press it while observing that part of the black
patch which is next its broader end: close to
the patch a minute drop of fluid will be observed
to be pressed out through a small opening, the
micropyle.

c. Carefully peel off the outer coat (testa) of the
seed: the two large fleshy cotyledons will be
laid bare.

d. Joining the cotyledons together will be found
the rest of the embryo: it consists of a conical
part (the radicle) lying outside the cotyledons,
with its apex directed towards the point where
the micropyle was; and of the rudiments of
the stem and leaves (plumule) lying between
the cotyledons.

g. The process of fertilization.
This is difficult to follow in the bean; but by using

different plants for the observation of its various stages
it is fairly easy to observe all its more important steps.

1.

A plant well adapted for seeing the penetration of

the pollen-tube into the stigma and style is the
Evening Primrose (Gnothera biennis).

Detach the style from the flower and hold the club-

_ shaped stigma between the finger and thumb of the

THI]

1

THE BEAN-PLANT. 85

left hand. Moisten it with a drop of water and then
make with a wetted razor several successive cuts
through it. This will divide the stigma into several
slices. Spread these out on a glass slide with a
needle in water and examine the thinnest, after put-
ting on a covering-glass.

The triangular grains of pollen will be seen sending
out from one angle a tube into the stigmatic tissue,
which is easily seen from its slight difference in
colour.

The entrance of the pollen-tube into the micropyle
can be readily made out in some species of Veronica.
The common V. Serpyllifolia—often to be found in
shady places on lawns—is well adapted for the pur-
pose. A flower should be taken from which the
corolla has just dropped. Dissect out the minute
ovary and using the dissecting microscope open with
a needle one of its two cells in a drop of water;
remove the mass of ovules and gently tease them
apart. Then put on a covering-glass and examine
with a low power till an ovule is found which shews
the entry of the pollen-tube. The addition of dilute
glycerine will make the ovule more transparent so
that after some time the embryo-sac can be seen and
the progress of the pollen-tube into the ovule followed.

The young fruit of Campanula (especially the com-
mon Canterbury Bells of gardens, Campanula Mediwm)
is convenient for examining the embryo-sac. It is
only necessary to cut thin transverse sections of the
fruit and examine in water. Some of the ovules cut
through will allow the embryo-sac to be seen, and in
fortunate sections the embryo-vesicle and the end of
the pollen-tube in contact with the embryo-sac.

IX.

THE BELL-ANIMALCULE (Vorticella).

THE great majority of those animal organisms which are
more complex than Ameba, begin their existence as simple
nucleated cells, having a general similarity to Ameba; and
the single nucleated cell which constitutes the whole animal
in its primitive condition divides and subdivides until an
aggregation of similar cells is formed. And it is by the.
differentiation and metamorphosis of these primitively similar
histological elements that the organs and tissues of the
body are built up. But in one group, the Jnfusoria, the
protoplasmic mass which constitutes the germ does not
undergo this process of preliminary subdivision, but such
structure as the adult animal possesses is the result of the
direct metamorphosis of parts of its protoplasmic substance.
Hence, morphologically, the bodies of these animals are the
equivalents of a single cell; while, physiologically, they may
attain a considerable amount of complexity.

The Infusoria abound in fresh and salt waters, and make
their appearance in infusions of many animal and vegetable
substances, their germs either being contained in the sub-
stances infused, or being wafted through the air. Their
diffusion is greatly facilitated by the property which many
of them possess of being dried, and thus reduced to the
condition of an excessively light dust, without the destruction

x] THE BELL-ANIMALCULE. 87

f their vitality; while their rapid propagation is, in the
nain, due to their power of multiplying by division, with ex-
raordinary rapidity, when duly supplied with nourishment.
[he majority are free and provided with numerous cilia by
vhich they are incessantly and actively propelled through
‘he medium in which they live; but some attach themselves
0 stones, plants, or even the bodies of other animals. A
ew are parasitic, and the bladder and intestines of the Frog
wre usually inhabited by several species of large size.

The Bell-animalcules are Infusoria which are fixed,
isually by long stalks, to water-plants, or, not unfrequently,
o the limbs of aquatic Crustacea. The body has the shape
f a wine-glass with a very long and slender stem, provided
rith a flattened disc-like cover. What answers to the rim
f the wine-glass is thickened, somewhat everted, and richly
iliated, and the edges of the disc are similarly thickened
nd ciliated. Between the thickened edge of the cover, or
eristome, and the edge of the disc, is a groove, which, at one
oint, deepens and passes into a wide depression, the vesti-
ulum. From this a narrow tube, the esophagus, leads into
ae central substance of the body, and terminates abruptly
nerein; and when fecal matters are discharged, they make
aeir way out by an aperture which is temporarily formed in
ae floor of this vestibule. The outermost layer of the sub-
vance of the body is denser and more transparent than the
ast, forming a cuticula. Immediately beneath the cuticle it
' tolerably firm and slightly granular, and this part is dis-
nguished as the cortical layer; it passes into the central
ibstance, which is still softer and more fluid.

In the undisturbed condition of the Bell-animalcule, the
em is completely straightened out; the peristome is everted,
id the edges of the disc separated from the peristome; the
astibule gaping widely and the cilia working vigorously.
ut the least shock causes the disc to be retracted, and the

88 ELEMENTARY BIOLOGY. [x

edge of the peristome to be curved in and shut against it, so
as to give the body a more globular form. At the same time,
the stem is thrown into a spiral, and the body is thus
drawn back towards the point of attachment. If the dis-
turbing influence be continued, this state of retraction per-
sists; but if it be withdrawn, the spirally coiled stem slowly
straightens, the peristome expands, and the cilia resume
their activity.

In the interior of the body, immediately below the disc,
a space, occupied by a clear watery fluid, is seen to make
its appearance at regular intervals—slowly enlarging until
it attains its full size and then suddenly and rapidly dis-
appearing by the approximation of its walls. This is the
contractile vesicle. Whether it has any communication with
the exterior or not and what is its function, are still open
questions. If the Bell-animalcule is well fed, one or more
watery vesicles of a spheroidal form, each containing a certain
portion of the ingested food, will be seen in the soft central
mass of the body. And by mixing a small quantity of
finely divided carmine or indigo with the water in which
the Vorticelle live, the manner in which these food-vesicles
are formed may be observed. The coloured particles are
driven into the vestibule by the action of the cilia of the
peristome and the adjacent parts and gradually accumulate
at the inner end of the gullet. After a time the mass here
heaped together projects into the central substance of the
body, surrounded by an envelope of the accompanying water;
and then suddenly breaks off, as a spheroidal drop, hence-
forward free in. the soft central substance. In some Bell-
animalcules, the food-vesicles thus formed undergo a move-
ment of circulation, passing up one side of the body, then
crossing over below the disc and descending on the other
side. Sooner or later the contents of these vesicles are
digested, and the refuse is thrown into the vestibule by an

Ix. ] THE BELL-ANIMALCULE. 89

aperture which exists only at the moment of extrusion of the
feeces, and is indistinguishable at any other time.

A portion of the substance of the body, which is slightly
different in transparency and in its reactions to colouring
substances from the rest, is called the nucleus or. endoplast.
It is elongated and bent upon itself into a crescentic or horse-
shoe shape.

The Bell-animalcules multiply in two ways; partly by
longitudinal fission, when a bell becomes cloven down the
middle, each half acquiring the structure previously possessed
by the whole; and partly by gemmation from the endoplast,
in which latter case the endoplast divides and one or more
of the rounded masses thus separated are set free as loco-
motive germs.

Sometimes a rounded body, encircled by a ring of cilia
but having otherwise the characters of a Vorticella bell, is
seen to be attached to the base of the bell of an ordinary
Vorticella. It was formerly supposed that these were buds but
it appears that they are independent individuals, which have
attached themselves to that to which they adhere and are
gradually becoming fused with it, so that the two will form
one indistinguishable whole. It is probable that this “con-
jugation” has relation to a sexual process.

Under certain circumstances a Vorticella may become
encysted. The peristome closes and the bell becomes con-
verted into a spheroidal body, in which only the nucleus
and the contractile vesicle remain distinguishable. This sur-
rounds itself with a structureless envelope or cyst, from
which, after remaining at rest for a longer or shorter time,
the Bell-animalcule may emerge and resume its former state
of existence. In thus passing into a temporary condition
of rest many of the other Infusoria resemble Vorticella.

The two genera of Infusoria which most commonly occur
in the Frog are Nyctotherus and Balantidium. Both are free

90 ELEMENTARY BIOLOGY. [Ix.

and actively locomotive, and the former is particularly re-
markable for its relatively large size and semilunar contour,
and for the length and distinctness of its curved cesophagus.
Balantidium is pyriform, and has a very short cesophageal
depression.

LABORATORY WORK.

A. Examine duckweed roots, conferve, &c, with 1 inch
objective avoiding pressure; having found a group of
Vorticelle note the following pomts with a higher
power.

1. In the extended state of the animal.
a, The body.
a. Its size (measure).

b. Form; broadly speaking, that of an inverted bell:
note—

a, The prominent everted rim (peristome).

8. The flattened central disc projecting above the
peristome.

y. The cilia fringing the disc.

6. The depression between the peristome and disc.

e. The mouth of the chamber (vestibulwm) into

which the cesophagus and anus open, in the
hollow between the peristome and disc.

c. Structure :-—

a. The thin, transparent, homogeneous external
layer (cutzcle).

Ix. ]

THE BELL-ANIMALCULE, 91

The granular layer (cortical layer) inside the
cuticle.

[Its fine transverse striation. ] -

The central more fluid part, not sharply marked
off from £.

The various clear spaces (alimentary vacuoles)
in it, containing foreign (swallowed) bodies
(Diatoms, Protococcus, &c.).

The contractile vesicle; its position, in the
cortical layer just beneath the disc; its systole
and diastole.

The nucleus; an elongated curved body in the
cortical layer; sometimes nearly homogeneous,
sometimes more distinctly granular. The nu-
cleus is usually indistinguishable until after
treatment with iodine (4).

The gullet; sometimes seen in optical trans-
verse section as a clear round space; some-
times seen sidewise as a canal opening above
on the disc, and ending abruptly below in the
body-substance.'

b. The stalk.

Its length and diameter (measure).

Its structure; the external homogeneous layer
(sheath) continuous with the cuticle ; the highly
refractive centre (avis) generally surrounded
with granules, and continuous with the cortical
layer of the bell.

2. In the retracted state.

The body.

Its form; pear-shaped; rounded off above; no
disc or peristome visible.

92

¥:

ELEMENTARY BIOLOGY. [Ix.

The clear transverse space near the top, indica-
ting the interval between the retracted disc
and the rolled-in peristome. In this space the
cilia can frequently be seen moving.

Structure; as in 1. ac.

b. The stalk ; thrown into corkscrew-like folds.

The

movements of Vorticella. Compare especially

the regularity, definiteness and rapidity of some of them

with

the slow and irregular movements of Amoeba.

(IIL)

a.

[B.

The ciliary movement.

Examine the cilia carefully; delicate homoge-
neous processes; their length, diameter and
form ; their position.

The continuity of the cilia with the cortical layer.]
The function of the cilia; their rapid move-
ments, alternately bending and straightening:
the co-ordination of these movements; they
work in a definite order; note the currents
produced in the neighbouring water (if ne-
cessary introduce a few particles of carmine
under the coverslip); the sweeping of small
bodies down the gullet.

The movements of the contractile vesicle (see III.
A. 3.¢). Tolerably regular rhythmic distension
and collapse (diastole and systole).

The currents in the central parts of the body carry-
ing round the swallowed bodies. (Compare VI. C.)

The movements of the animal as a whole. (4 inch
or $ inch obj.)

1x.]

THE BELL-ANIMALCULE. 93

‘Its extreme irritability; it contracts on the
slightest stimulation: often without any ap-
parent cause.

The movements which occur in contraction ;
the coiling up of the stalk ; the rolling in of the
disc. The rapidity of these movements.

The mode of re-expansion ; the stalk straightens
first; then the peristome is everted; finally
the disc and its cilia are protruded.

4. Stain with iodine or magenta; the cuticle uncoloured
—the rest stained; the nucleus especially becomes
deeply coloured.

5. Treat with acetic acid; the contents soon disappear
(except perhaps some swallowed bodies)—the cuticle
later or not at all.

6. Note the following points in various specimens—

a.

ly.

(3.

Multiplication by fission ; a bell partially divided
into two by a vertical fissure starting from the
disc.

Two complete bells on one stalk; the result
of completion of the fission. The development
of a basal circlet of cilia by one or both of these
bells.
Free swimming unstalked bells (detached bells from
B).]
Conjugation ; the attachment of a small free swim-
ming bell to the side of a stalked one. |

Encystation ; the body contracted into a ball and
surrounded by a thickened structureless layer, the
contractile vesicle being persistently dilated. ]

94 ELEMENTARY BIOLOGY. [rx

B. Other forms closely allied to Vorticella which may be
met with, and which will do nearly as well for exami-
nation, are ;—

a. Hpistylis, Bell-shaped animals growing on a
branched non-contractile stalk.

b. Carchesium. A form very like Vorticella but borne
on a branched contractile stalk.

c. Cothurnia. An almost sessile form, provided with
a cup or envelope into which the bell can be re-

tracted.

[The activity of the movements of the free Infusoria interferes
with the complete examination of the living animal. It is well
therefore to add a little osmic acid solution to the drop of water
under examination. This kills such Infusoria as Paramecium,
Nyctotherus and Balantidium instantly, without destroying the
essential features of their organization. ]

Ss

THE FRESHWATER POLYPES (Hydra viridis
and H. fusca).

IF a waterweed, such as duckweed, from a pond, is placed in
a glass and allowed to remain undisturbed for a short time,
minute gelatinous-looking bodies of a brownish or green
colour may frequently be found attached to it, or to the sides
of the glass. They have a length of from 1 to } of an inch,
and are cylindrical or slightly conical in form. From the
tree end numerous delicate filaments, which are often much
longer than the body, proceed and spread out with a more
or less downward curve, in the water. If touched, these
threads, which are the tentacles, rapidly shorten and together
with the body shrink into a rounded mass. After a while,:
the contracted body and the tentacles elongate and resume
their previous form. These are Polypes, the brown ones
belonging to the species termed Hydra fusca, the green
to that called H. viridis. The polypes usually remain at-
tached to one spot for a long time, but they are capable
of crawling about by a motion similar to that of the looping
caterpillar; and, sometimes, they detach themselves and float
passively in the water.

When any small animal, such as a water-flea, swim-
ming through the water comes in contact with the tentacles,
it is grasped, and conveyed by their contraction to the

96 ELEMENTARY BIOLOGY. [x.

aperture of the wide mouth, which is situated in the
middle of the circle formed by the bases of the tentacles,
It is then taken into a cavity which occupies the whole
interior of the body; the nutritive matters which it contains
are dissolved out and absorbed by the substance of the:
Hydra; andthe innutritious residuum is eventually cast
out by the way it entered. Small pieces of meat, brought
within reach of the tentacles, are seized, swallowed and
digested in the same manner.

If a Hydra is well fed, bud-like projections make their
appearance upon the outer surface of the body. Thesé
gradually elongate and become pear-shaped. At the free
end a mouth is formed; and around it minute processes are
developed and grow into tentacles; and thus a young Hydra
is formed by gemmation from the parent. This young Hydra
becomes detached sooner or later and leads an independent
existence; but, not unfrequently, new buds are developed
from other parts of the parent before the first is detached,
and the progeny may themselves begin to bud before they
attain independence. In this manner, temporarily compound
organisms may be formed. Experiments have shewn that
* these animals may be cut into halves or quarters and that
each portion will repair its losses, and grow up into a perfect
Hydra; and there is reason to believe that this process
of fission sometimes occurs naturally.

The Hydra multiplies by budding through the greater
part of the year; but in the summer projections of the surface
appear at the bases of the tentacles’6 er nearer the attached
end of the body. Within the former (testes) great numbers
of minute particles, each moved by a vibratile cilium, are
developed and are eventually set free. Functionally, these
answer to the antherozooids of plants and they are termed
spermatozoa.

The enlargement formed near the attached end of the

Al THE FRESH-WATER POLYPES, 97

olype may be single, as in Hydra viridis, or as many as eight
ray be found in other species. It becomes much larger
han the testis and is the ovary. Within it is developed
single large egg, or ovum. This ovum, which is a huge

ucleated cell, is impregnated by the spermatozoa and |)

undergoes division into two parts. Each of these again di-
ides into two; and so on, until the ovum is broken up into
number of small embryo-cells. The mass of embryo-cells
hus formed becomes surrounded with a thick, usually tuber-
ulated or spinous, case; and, detaching itself from the body,
orms the ‘egg,’ from which a new Hydra is developed.

Microscopic examination shews that the body of the
Tydra is a sac, the wall of which is composed of two
nembranes, an outer (ectoderm), and an inner (endoderm).
Che tentacles are tubular processes of the sac, and therefore
re formed externally by the ectoderm and lined internally
ny the endoderm. Both the endoderm and the ectoderm
ire made up of nucleated cells; the inner ends of those
f the ectoderm being prolonged into delicate fibres, which
‘un parallel with the long axis of the body on the inner
ace of the ectoderm. The green colour of the Hydra viridis
‘esults from the presence of chlorophyll grains imbedded
n the protoplasm of the cells.

In both the ectoderm and the endoderm the protoplasm
of the cells contains very singular bodies,—the so-called
irticating capsules, threed-cells, or nematocysts—which are
nval bags, with thick and elastic walls, containing a spirally
oiled-up filament which is unrolled suddenly on the
lightest pressure and then presents the appearance of a long
jlament attached to the capsule, and often provided with
chree recurved spines near its base. As similar capsules of a
arger size are the agents by which many of the jelly fishes
sting severely, just as nettles do when they are handled, there
s every reason to believe that the thread-cells of the Hydra

a

M, ‘

me

org

A
i

98 ELEMENTARY BIOLOGY. [X,

exert a like noxious influence upon the small animals which
serve as their prey.

Thus, Hydra is essentially a cellular organism like one
of the lower plants, but differs from them morphologically
in the fact that its cells are not inclosed within cellulose
walls; and physiologically, in the dependence of these cells
for their nutrition upon ready formed protein matter. The
function of the chlorophyll granules contained in the endoderm
of the green Hydra, and of the brown or orange-coloured
particles in the endoderm of the other species, is wholly
unknown.

The Hydra, again, may be compared to an aggregate of
Amobe, which are arranged in the form of a double-walled
sac and have undergone a certain amount of metamorphosis,

It is possible that the longitudinal fibres connected with
the cells of the ectoderm may be specially contractile, and re-
present muscles; but, however this may be, each cell has its
own independent contractility. No trace of a special nervous
system has yet been discovered, and the manner in which
the actions of the different parts of the Hydra are combined
to a common end, as in locomotion and the seizing of prey, -
is not understood.

The Hydra has none of the special apparatuses which are
termed sense-organs, or glands. The cavity of thé body.
alone represents a stomach and intestine; there are no
organs of circulation, respiration or urinary secretion; the
products of digestion being doubtless transmitted, by im-
bibition, from cell to cell, and those of the waste of the cells
exuded directly into the surrounding water.

a.

THE FRESH-WATER POLYPES. 99

LABORATORY WORK.

Put in a beaker some water containing bodies to
which Hydre are attached and place the beaker in a
window not exposed to direct sunlight: in the course
of some hours many Hydre will be found attached to
that side of the glass which is turned towards the
light. Note their size, form, colour, mode of attach-
ment and movements,

Transfer a Hydra, by means of a pipette, on to a
slide; cover in plenty of water with a large coverslip,
and examine with linch obj. Note—

Form.

a. The base (so called foot): a flattened disc; nar-
rower or wider than the body according to the
state of extension of the latter.

8. The body proper: cylindrical, varying much
in length and diameter with the state of exten-
sion of the animal; its conical free end, with
an opening (mouth) in it. It is often difficult
to see the mouth in this way, especially in the
green species. It is readily seen however if a
Hydra be placed in a drop of water, without a
coverslip, and be watched with an inch objec-
tive until it turns its anterior end up towards
the observer.

y. The tentacles: ranged round the mouth their
number and shape; their varying length and
diameter ; the knob-like eminences on them.

7—2

100

ELEMENTARY BIOLOGY. [x.

The testes: small conical colourless eminences
below the point of attachment of the tentacles,
The ovary: a larger rounded colourless promi-
nence near the base: there may be more than
one.

The buds: young Hydre, of various sizes and
stages of development, attached to the sides
of the parent.

Either 6. e. or € or all of seis may be absent
in some specimens.

b. Structure.

a.

The animal evidently composed of two layers,
an outer, ectoderm, and inner, endoderm, the
latter alone containing chlorophyll in the green
species: the ectoderm is marked out into areas,
and may with care be seen to be composed of
distinct cells, though this is a little difficult
to make out in fresh specimens.

The body-cavity: difficult to make out in the
green species, frequently visible in the brown
ones as a darker central patch with which the
mouth-opening is continuous ; the extension of
the body-cavity into the tentacles. “Note cor-
puscles floating along inside them when they
are extended.

c. Movements.

a.

The general contractility of the animal; it
is constantly either extending or shortening its
body and tentacles, and so altering its form and
place.

Its irritability ; slight pressure or other stimu: |
lus immediately causes it to. contract.

el THE FRESH-WATER POLYPES. 10L

3. Examine with a high power: try to make out the

different cells of the ectoderm— :

a. Large somewhat conical nucleated cells, with
the broader end turned outwards.

8. Smaller rounded cells packed between the deep
ends of the larger ones.

y. The nematocysts: small oval capsules, with a
filament coiled up inside them, which are
dispersed through the ectoderm in the interior
of its component cells.

4, Treat with magenta: note the staining of the cells,
the emission of the thread-cells, and the protrusion
of their threads: three chief forms of thread-cell—

a, ‘An oval capsule with a filament many times its
own length attached to one end, and three
short processes radiating from the base of the
thread,

8. Smaller thread-cells, without the radiating pro-
cesses and with a short thread.

y. Cells like 8. but with a much longer thread.

Imbed in paraffin a Hydra which has been hardened
in chromic or osmic acid‘ and cut sections from it;
or lay a prepared Hydra on a glass slide and with a
razor cut off transverse slices; having obtained by
either method a number of thin sections mount them
in glycerine and make out—

Or

1 When a Hydra is placed in the above hardening fluids it nearly
always contracts so much as to make it difficult to cut sections. If it be
first killed, by placing it in a small quantity of water and when it has ex-
panded adding some boiling water, fairly extended specimens for hardening
san usually be obtained,

ELEMENTARY BIOLOGY. [x.

a. The large and small cells of the ectoderm and
its thread-cells, their arrangement and rela-
tions. (3.)

B. The cells of the endoderm: large, nucleated,
with a flattened base and a rounded free end:
their arrangement in a single layer.

y. The thin intermediate layer (muscular stratum)
between ectoderm and endoderm.

6.. The body cavity.

Tease out in water a specimen which has been treated
with weak chromic acid (0. 12) or with osmic acid:
make out the various cells already described: notice
branched tails proceeding from the narrower ends of
the larger ectoderm cells.

Tease out a fresh Hydra in water and observe the various
cells. Note the amcboid movements exhibited by some,
and the single cilium attached to other (endoderm) cells. ]

Gently flatten out a testis in water by pressure on the
coverslip, and examine with a high power. According
to its state of maturity the following contents will be
found in it—

a. A collection of the smaller ectoderm cells.

8. The same but having lost their nucleus and
become hyaline.

y. Cells otherwise like @. but with a long filament
proceeding from them.

8. Ripe spermatozoa: bodies consisting of a very
small oval head to which a very delicate fila-
ment is attached, and which should they get
free swim about in the water by the movements
of this filament. They may frequently be seen
in motion within the unruptured testis.

x]

THE FRESH-WATER POLYPES. 103

9. Press out an ovary: according to its stage of develop-
ment there will be found in it—

a

B.

Simply ectoderm cells with an unusual prepon-
derance of the smaller form.

Imbedded among cells like a, one which has
become larger and clearer than the rest, and
possesses a distinct central clear spot in it.

Considerable aggregation of granular proto-
plasm round this cell, so as to form a body
consisting of a granular protoplasmic mass, in
which is imbedded a clear round vesicle which
again contains a distinct rounded dot.

The ripe ovum. Consisting of a great irregu-
larly branched mass of protoplasm (vitellus), in
which is a clear space (germinal vesicle) con-
taining another body (the germinal spot).

The segmented ovum: composed of a large
number of small cells. Its thick capsule,
rough on its external surface.

XI.

THE FRESH-WATER MUSSEL
(Anodonta Cygnea).

UNDER the name of ‘ Fresh-water Mussel’ two distinct kinds
of animals, which are not unfrequently abundant in our ponds
and rivers, are included; namely, the Anodonta and two or
three kinds of Unio. The Anodonta is chosen for special
study here, but what is said about it applies very well to all
parts of Unio except the shell.

The animal is inclosed in a shell composed of two pieces
or valves, which are lateral, or right and left, in relation to the
median plane of the body. The more rounded and broader
end is anterior, the more tapering, posterior. If placed in a
vessel of water, at the bottom of which there is a tolerably
thick layer of soft mud or sand, and left quite. undisturbed,
the Anodonta will partially bury itself with its anterior end
directed obliquely downwards; and the valves will separate at
their ventral edges for a short distance. At the edges of this
‘gape’ of the shell the thickened margins of a part of the
contained body which is called the mantle, become visible,
and between them a large, whitish, fleshy, tongue-shaped
structure—the foot—not unfrequently protrudes, and is used
to perform the sluggish movements of which the Anodon is,
capable. If some finely divided colouring matter, such as
indigo, is dropped into the water, so as to fall towards the

. xr] THE FRESH-WATER MUSSEL. 105

gape, it will be seen to be sucked in; while, after a short time,
a current of the same substance will flow out from an opening
between the two edges of the mantle on the dorsal side of
the posterior end of the body; and these ‘inhalent’ and
‘exhalent’ currents go on, so long as the animal is alive and
the valves are open. Any disturbance, however, causes the
foot, if it was previously protruded, to be retracted, while the
edges of the mantle are drawn in and the two valves shut with
great force. On the other hand, in a dead Anodonta the valves
always gape, and if they are forcibly shut spring open again.
The reason of this is the presence of an elastic band, which
unites the dorsal margins of the two valves, for some dis-
tance, and is put on the stretch when the valves are forcibly
brought together. During life they are thus adducted by
the contraction of two thick bundles of muscular fibres, which
pass from the inner face of one valve to that of the other,
one at the anterior and the other at the posterior end of the
body, and are called the anterior and posterior adductors.
The animal can be extracted from the shell without
damage, only by cutting through these muscles close to their
attachments. It is bilaterally symmetrical, the foot proceed-
ing from the middle of its ventral surface; the mouth is
median and situated between a projection, which answers to
the under surface of the anterior adductor muscle, and the
superior attachment of the foot. On each side of the mouth
are two triangular flaps with free pointed ends—the labial
palpi—and behind these, on each side, two broad, plate-
like organs, with vertically striated outer surfaces, are
visible. These are the gills or branchice. In the dorsal
region, the integument is soft and smooth; on each side,
it is produced into two large folds, the lobes of the mantle
or palliwm, which closely adhere to the inner surface of the
valves of the shell, and end, ventrally, in the thickened
margins already mentioned. They pass into one another in

106 ELEMENTARY BIOLOGY. [XI

front of the mouth; at the sides, they are united with the
dorsal edges of the outer gill-plates; and, behind, they extend
upwards and on to the dorsal face of the body, before finally
passing into one another above, and in front of, the anus,
which is small, tubular, prominent and median. Thus the
anus is inclosed in a part of the cavity bounded by the two
mantle lobes, which is relatively small and shallow, and is
termed the cloacal chamber ; while the gills, the foot, and the
palps, hang down into the relatively large branchial chamber,
which occupies the space between the mantle-lobes for the
rest of their extent. It is the prolongation of the margins
of the former cavity which gives rise to the tubular anal
siphon seen in so many Lamellibranchs; while the ventral
or branchial siphon is a similar prolongation of the margins
of the branchial chamber. The dorsal siphon is the channel
through which the exhalent currents pass; the ventral, that
for the inhalent currents.

The currents are produced and kept up by the action of
the cilia which abound upon the gills. The latter are per-
forated by innumerable small apertures, and the chambers
contained between the two lamelle of which each gill is
formed, are in communication, above, with the cloacal
chamber. The cilia work in such a way as to drive the
water in which the animal lives from the outer surface of
each gill towards its interior. Hence the current which sets
from the branchial to the cloacal chamber.

The current of water which is thus continually drawn
into the branchial chamber carries with it minute organisms,
Infusoria, Diatoms and the like, and many of these are swept
to the fore part of the branchial chamber, where they enter
the mouth, and are propelled by the cilia which line its cavity
into the alimentary canal. The latter presents a short and
wide gullet, a stomach surrounded by hepatic follicles, a long
intestine coiled upon itself, im» a somewhat complicated

x1] THE FRESH-WATER MUSSEL. 107

manner, and, finally, a rectum, which lies in the middle line
of the dorsal aspect of the body, traverses the pericardium
and the heart which lies therein, and finally ends in the anus.

As the mouth is below and behind the anterior adductor and
the rectum passes in front of and above the posterior adductor,
it is clear that the alimentary canal, as a whole, lies between
the two adductor muscles.

Digestion, that is solution of the proteinaceous and other
nutritive matters contained in food, is effected in the stomach
and intestine; and the nutritious fluid, thus formed, transudes
through the walls of the alimentary cavity and passes into
the blood contained in the blood-vessels which surround it.
This blood is thence carried into a large sinus, which occupies
the middle line of the body under the pericardium and
between the organs of Bojanus (see Laboratory work 5),
and receives the greater part of the blood returning from
all parts of the body. From this median vena cava, branches
are given off to the gills and open into the extensive vascular
network which those organs contain. From this, again,
trunks lead towards the pericardium and open into one or
other of the two auricles of the heart, which communicate
by valvular apertures with the ventricle. The ventricle gives
off two aortic trunks, one of which, the anterior, runs forwards
in the middle line, above the rectum, while the other runs
backwards, below the rectum. From these two aorte branches
are given off which divide into smaller ramifications for the
different regions of the body, and for the viscera, and finally
terminate in channels which answer to the capillaries of the
higher animals.

The pericardial cavity, in which the heart is lodged, is
situated in the posterior half of the dorsal region of the body.
Through its thin dorsal wall, and, still better, when it is care-
fully laid open, the heart can be seen beating. The auricles
contract and, after them, the ventricle ; the wave-like contrac-

108 ELEMENTARY BIOLOGY. [xr

tion of the latter being much the more easily visible. The lips
of the auriculo-ventricular apertures are so disposed that the
blood is impeded from flowing back into the auricles, when
the ventricles contract, and is forced out, either forwards
or backwards, through the two aorte. From these it finds
its way to the capillaries, and returns from them to the
vena cava; whence it is carried, through the organs of Bo-
janus, to the branchie. Here it becomes purified of carbonic
anhydride, and receives oxygen from the water in which
the branchiz are plunged; and it is finally brought back in
an arterialized condition to the heart.

The heart is therefore systemic and propels aerated blood.

The majority of the vessels which convey the blood from
the vena cava to the branchiaz, traverse the walls of the dark-
coloured organ—the organ of Bojanus—which has already
been mentioned ; and it is probable that they here part with
their nitrogenous waste matters—the organ of Bojanus, in all
probability, playing the part of a kidney. The cavity of
the organ of Bojanus communicates, on the one hand, with
the pericardium, and, on the other, with the exterior, by an
aperture which is situated close to the attachment of the
inner gill to the walls of the body. Thus the cavity of the
pericardium communicates directly with the exterior, though
by a roundabout way. But it also communicates directly
with the venous system, by sundry small apertures placed in
the anterior part of its floor, Hence it must contain a
mixture of blood and water.

The blood of the Anodonta is colourless, and contains
colourless corpuscles, which resemble those of Man in struc-
ture and present the same Amcebiform movements.

The nervous system of the Anodonta consists of three
pairs of yellow ganglia; the cephalic, situated at the sides of
the mouth; the pedal, placed in the foot; and the parieto-
splanchnic, on the under face of the posterior adductor muscle.

XU] THE FRESH-WATER MUSSEL. 109

They are united by commissural cords which connect the
cephalic ganglia with one another, and with the pedal
and parieto-splanchnic ganglia, respectively. The only
sense organs which have been discovered, are a pair of
auditory vesicles, connected by nervous cords with the pedal
ganglia. F

The sexes are distinct. The testes and ovaria are similar
in character, being racemose glands, which, in the breeding
season, occupy a great part of the interior of the body.
There is one gland on each side, opening by a minute
aperture close to that of the organ of Bojanus.

The spermatozoa have minute, short, rod-like bodies,
to which a long, filamentous, active ctliwm is attached, and,
thrown off in enormous numbers, make their way out with
the exhalent currents.

The ova are spherical, and the vitelline membrane is
produced at one point into a short open spout-like tube,
with a terminal aperture, the micropyle, through which, in
all probability, the spermatozoon makes its entrance. When
fully formed, multitudes of these ova pass out of the oviducal
aperture and become lodged in the chambers of the gills,
particularly the external gill, which is frequently completely
distended by them. Here they are hatched, and give rise
to embryos, which are so wholly unlike the parent Anodonta,
that they were formerly thought to be parasites, and received
the name of Glochidium. The embryo Anodonta is provided
with a bivalve shell. Each valve has the form of an equi-
lateral triangle united by its base with its fellow, by means
of an elastic hinge, which tends to keep the two wide open.
The apex of the triangle is sharply incurved, and is produced
into a strong serrated tooth, so that when the valves ap-
proach, these teeth are directed towards one another. The
mantle is very thin, and the inner surface of each of its
lobes presents three papille, terminated by fine pencils of

110 ELEMENTARY BIOLOGY. [x1

hair-like filaments. What appears to be the oral aperture
is wide, and its margins are richly ciliated. There is a single
adductor muscle and a rudimentary foot, from which one
or two long structureless filaments, representing the byssus
of the sea-mussel, proceed. These byssal filaments become
entangled with one another and tend to keep the ‘Glochidia’
in their places.

After a time the larval Anodonte leave the body of the
parent, and attach themselves to floating bodies—very com.
monly to the tails of fishes—by digging the incurved points
of their valves into the integument in the latter case, and
holding on by them as if they were pincers. In this situa-
tion they undergo a metamorphosis; the gills are developed,
the foot grows, the auditory vesicles become conspicuous
in it, and the young Anodon at length drops off and falls
into its ordinary habitation in the mud.

LABORATORY WORK.

1. In the natural state of the animal only the shell or
exoskeleton is visible, or this may be slightly open,
and then the edge of the membrane lining it (the
mantle) may be visible. Raise one valve of the shell,
by separating the mantle from it with the handle of a
scalpel, and then cutting through two strong bodies (the
adductor muscles), one at each end of the animal,
which run from one valve of the shell to the other
and prevent their separation. The two valves will
now be united only by their ligament.

2. General form and structure.

a. Inthe animal nowlaid bare maybe distinguished—

a. A dorsal border turned towards the hinge of
the shell, and nearly straight.

x1]

THE FRESH-WATER MUSSEL. 111
A curved ventral border, opposite’ the dorsal. ,
A wider anterior end.

A narrower posterior end.

A right and left side.

b. The mantle or pallium.

a.

B.

A bilobed semitransparent membrane, one lobe
lining each valve of the shell.

The continuity of the two lobes on the dorsal
side of the animal; their separation along
most of its ventral side, where each forms a
thick yellowish free border. ;

The union of the two pallial lobes, for a short
distance, towards the posterior part of their
ventral border,

The rudimentary dorsal and ventral siphons,
separated from one another at the point of
union y. and each marked out by a part of
the mantle-edge covered by short hair-like
processes: the dorsal siphon completely closed
below and forming a narrow oval slit; the
ventral siphon open below and continuous with
the cleft between the ventral edges of the
mantle-lobes.

The branchial or pallial chamber: turn back
the ventral edge of that mantle-lobe from which
the shell has been removed: a chamber is thus
exposed into which the ventral siphon and
the cleft continuous with it, lead.

C.

a.

ELEMENTARY BIOLOGY, [XL

The cloacal chamber: pass a probe through the
dorsal siphon; it will enter a small chamber,
separated from the pallial chamber by a par-
tition which unites the hinder part of the two
inner gills (¢, £.).

The contents of the pallial chamber.

The foot: a large, yellowish, somewhat plough-
share-shaped mass, in the middle line; its apex
directed forwards and ventrally, towards the
front of the cleft between the mantle-lobes,

The gills or branchie: two lamellar bodies on
each side of the foot, but reaching farther back
than it does: the outer gill on each side, at-
tached to the mantle-lobe; the inner, attached
to the foot in front, but farther back separated
by a cleft from it; and behind the foot, united
across the middle line with its fellow so as
to form a partition separating the cloacal from
the pallial chamber.

The labial palps: a pair of small triangular
processes on each side, in front of the gills and
on the dorsal end of the anterior edge of the

foot.

The mouth: each labial palp is continuous with
its fellow across the middle line, and between
the lip-like ridges thus formed, lies the wide
mouth-opening,

The anterior and posterior adductor muscles: if
the reflected mantle-lobe be turned down again,
the oval divided ends of the adductor muscles can

be seen. They appear to perforate the mantle.

@

2 a

aL.

THE FRESH-WATER MUSSEL. 118

Now remove the animal completely from its shell, by
detaching the other mantle-lobe from the valve to
which it is fixed, and cutting through the attachments
of the adductor muscles to that valve. The thick
dorsal border of the animal and the continuity of
the mantle-lobes will now be more readily made out
than they could be previously (2. b. 8.).

The heart.

a.

On the dorsal border of the animal is a clear
space, where the mantle is very thin and covers
in a cavity filled with fluid. This cavity is the
pericardium, and through its walls the heart can
be seen beating.

Pin the Anodon out in water between two pieces
of loaded cork, or paraffin, so that its dorsal border
is upwards, a mantle-lobe spread over each bit of”
cork, and its foot and gills hanging down between
the two pieces: then carefully cut away the dor-
sal side of the pericardium without injuring the
heart.

The heart will now be exposed; it is a yellow-
ish transparent sac, exhibiting regular contrac-
tions and composed of a median and two lateral’
chambers.

The ventricle, or median chamber ; an oval sac,
from each end of which a large vessel (antervor
and posterior aorta) is continued; running
through the middle of the ventricle is seen
part of the alimentary canal. All parts of
the wall of the ventricle do not contract to-
gether; but a sort of wave of contraction
’ 8.

.

114

ELEMENTARY BIOLOGY. [XI.

passes, from one end of it to the other, like the
peristaltic contraction of the intestine in one
of the higher animals.

The auricles ; one of these will be seen on each
side if the ventricle be gently pushed out of the
way: each is a somewhat pyramidal sac, con-
tinuous with the ventricle at the apex of the
pyramid.

5. The organs of Bojanus.

a.

b.

Divide the alimentary canal at the posterior part
of the pericardiac chamber and turn it and the
heart forwards, so as to lay bare the floor of the
pericardium. Running along the middle line
of this floor will be seen a large blood-sinus,
the great vena cava; on each side of this, the
floor is formed by the roof of a transparent sac
(the non-glandular part of the organ of Bojanus),
through which is seen a dark brown mass (the
glandular part of the organ of Bojanus).

At the extreme front end of the pericardiac floor,
immediately under the point at which the in-
teste enters the cavity, will be found a pair of
oval openings; pass into each a bristle, tipped
with a small knob of sealing-wax to prevent it
from perforating a passage for itself: the opening
will be found to lead to a channel which runs
along the glandular part of the organ of Bojanus.

Remove carefully the thin transparent roof of the
non-glandular part of the organ of Bojanus, on one
side, so as to lay bare the portion of the glandular

THE FRESH-WATER MUSSEL. 115

part which lies within the non-glandular: the
bristle will be found to leave the passage in the
glandular portion by an aperture, which puts it
in communication with the non-glandular part,
and is situated on the upper side of the glan-
dular part, opposite the posterior end of the peri-
cardium. The glandular part extends back some
way beyond this point ; but it is imbedded closely
in the neighbouring tissues, and is not contained
in the loose non-glandular sac, which reaches back
no farther than the posterior end of the pericar-
dium.

Examine the floor of the non-glandular part, at its
anterior end: in it will be found a small aperture ;
gently push a guarded bristle through this: then
turn the animal over, and detach the front end of
the inner gill on the same side, from the foot.
The bristle will be found to have passed out by

an aperture (external opening of the organ of’

Bojanus) which lies just above the attachment of
the gill to the body.

6. The gills or branchiz.

a.

Cut out one of the gills and examine it; it will be
found to consist of two lamelle united by their
ventral edges and enclosing a central cavity, which
opens into the cloacal chamber. The cavity be-
tween the lamelle is subdivided by transverse
partitions, which pass from one lamella to the

other.

Carefully cut out a bit of the wall of the gill-sac

on one side; mount in water and examine with

1 inch obj. The outer surface will be seen to be
8—2

116

7%

ELEMENTARY BIOLOGY. [XI

formed by parallel vertical bars, containing pairs
of short rods; the inner face being formed by a
meshwork of large vessels, perforated by wide
apertures,

Examine with a higher power : the margins of each
cleft will be found covered with large active cilia,

The nervous system.

The cerebral ganglia.

These will be found by carefully dissecting
away the bases of the labial palps and the
integument on the dorsal side of the mouth.
They are two in number and each about the
size of a pin’s head, but somewhat angular in
form.

The commissures connected with the cerebral
ganglia are—

A short cord uniting the two ganglia across
the middle line over the mouth.

A cord, the cerebro-pedal commissure, which
runs downwards and backwards from each
and becomes continuous with that which runs
forwards from the pedal ganglion of the same
side (7. b. 8.).

A long slender cord which passes directly
backwards from each beneath the organ of
Bojanus and joins the parieto-splanchnic gan-
glia of the same side (7. ¢.).

The pedal ganglia.
Lay the animal on one side and proceed gently

to scrape away the tissues of the foot at about
the junction of its anterior with its middle

x1.] THE FRESH-WATER MUSSEL. 117

third. The pedal ganglia will thus be brought
into view. They are a pair of deep-orange-
coloured oval bodies, each rather larger than a
big pin’s head ; they are applied to one another
in the middle line.

8. From each ganglion one commissural cord
(a. 8.) passes forwards and upwards to the
cerebral ganglion of its side, and branches are
given off to the muscles of the foot and to the
auditory organ,

c. The parieto-splanchnic ganglia.

a This pair are readily found by turning the
animal on its dorsal side, and dissecting away
the integument from the ventral surface of the
posterior adductor muscle.

8. ‘Trace forwards from each the cord (a. 8.) which
runs to the cerebral ganglion of the same side.
It is easy to follow the commissure so long as
it lies in the region of the organ of Bojanus—
difficult further on.

Wea The auditory organ.

a. This is rather difficult to dissect out in Anodon:
it is a small sac which may be found by tracing
back the posterior cord given off from the pedal
ganglion, to a branch of which it is attached.
There is usually an auditory vesicle connected
with each pedal ganglion.

b. Ifa fresh Cyclas* be obtained, and its foot re-
moved, mounted in water, and examined with

1 Cyclas cornea—a small fresh-water lamellibranchiate mollusk.

118

ELEMENTARY BIOLOGY. [XI.

1 inch obj. the auditory sac can readily be seen
with a constantly trembling particle, the otolith,
in it.

9. The alimentary canal.

a,

This must be dissected out in another Anodon, as
it has been partially removed with the ventricle
of the heart. Pass a guarded bristle into the
mouth as far as it will readily go, and then lay
open the alimentary canal along it, with a pair of
scissors. Then push the bristle gently a little
farther on, and follow it with the scissors, and so
on, until the whole canal is opened.

The alimentary canal first runs towards the dorsal
side for a short way (awsophagus), lying on the
ventral side of the anterior adductor muscle: it
then dilates into a small squarish sac (the stomach);
behind the stomach it continues asa long narrow
tube, the intestine; this turns abruptly down, be-
hind the stomach, into the foot; then curves up
in the foot to near its dorsal border; then bends
abruptly down again, towards the ventral part of
the foot, where it makes another turn and runs
up to the anterior end of the pericardium ; thence
it runs back as a straight tube (the rectum), first
through the ventricle of the heart, and then
(passing on the dorsal side of the posterior ad-
ductor muscle) along the dorsal side of the cloacal
chamber, in which it ends in an opening, the
anus, placed on a prominent papilla.

On the sides of the stomach lies a brownish glan-
dular mass, the liver.

x1] THE FRESH-WATER MUSSEL. 119

a, Tease out a bit of the liver in water, and ex-
amine with } obj. It is composed of branched
cecal tubes lined by a layer of brownish epi-
thelial cells,

10. Reproductive organs.

a The animals are dicecious, but the reproductive
organs are similarly constructed in both sexes:
they vary much in size with the season, being
large in winter and spring, but small at other
times.

b. Close to the external opening of the organ of
Bojanus will be found another small opening on
each side, this is the generative opening.

c. From the generative opening can be traced back
a duct, which divides into many cecal branches
which lie in the upper part of the foot.

11. Muscular system.

a. This is most readily dissected out in a specimen
which has been hardened in spirit. The chief
muscles are:

a. The anterior and posterior adductor muscles
which pass directly from one valve of the shell
to the other. These have already been seen.

8. The posterior retractor of the foot: this can
readily be found, on each side, running into
the foot from its attachment to the shell in
front of the posterior adductor muscle.

y. The anterior retractor of the foot: this runs
from its attachment to the shell- behind the
anterior adductor muscle, into the front of the
foot.

b.
12.

a.

b.

C.

ELEMENTARY BIOLOGY. .; [x I

The intrinsic foot-muscles: forming the greater
part of the ventral portion of that organ.

Small muscles attached to each mantle-lobe,
at some little distance from its swollen free
edge and fixed to the shell along a linear
impression, which runs from one adductor to
the other and is termed the pallial line.

Tease out in glycerine a bit of one of.the mus-
cles which has been treated with 0°58 chromic
acid solution. Examine with 4 inch obj. It is
composed of spindle-shaped flattened cells, in
each of which lies an elongated nucleus: the
substance surrounding the nucleus is clear, but
the rest of the cell is granular and contains a
great number of small particles arranged pretty
definitely in transverse rows. While these mus-
cular fibres agree in form with those of smooth
muscles, in minute structure they approach striped
muscles,

The shell or exoskeleton.

Its two hardened lateral pieces or valves; each
with a straight dorsal and a curved ventral edge,
and an anterior larger and posterior smaller end:
note the soft uncalcified ventral edge of each
valve.

The umbo ; asmall blunt eminence on the dorsal
border of each valve near its anterior end.

The ligament: an elastic uncalcified part of the
exoskeleton behind the umbones, uniting the two
valves and tending to keep their ventral edges
slightly separated.

XI]
d.

a,

THE FRESH-WATER MUSSEL. 121

The markings on the shell.

External markings. The outside of the shell
is greenish brown, and on it are seen a number
of concentric lines generally parallel to the
margin of the shell, and more numerous to-
wards the ventral edge.

Internal markings. The interior of the valve
is white and iridescent: on it are seen, near the
dorsal border, two oval marks, the anterior and
posterior adductor impressions.

Joining the two adductor impressions is a
curved line, the pallial impression, which marks
where the muscles of the edge of the mantle
were fixed to the shell.

In front of the posterior adductor impression
is seen a small mark, indicating where the
posterior retractor muscle was fixed.

Extending from each adductor impression
towards the umbo is a fainter, gradually taper-
ing impression, which may be followed into
the cavity of the umbo, and indicates the
successive attachments of the adductor muscles,
as the animal has increased in size.

13. In the breeding season, examine the contents of the
testis for spermatozoa, and those of the ovary for

ova,

Note the micropyle of the latter. If the outer

gill appear to be thick and distended, it will be
found full of the larve of the Anodon,— Glochidium.
Note the characters of their shells and the entangled
filaments, or byssus, with which they are provided.

XII.

THE FRESH-WATER CRAYFISH (Astacus flu-
viatilis) AND THE LOBSTER (Homarus vul-
gars).

THE Crayfish and the Lobster are inhabitants of the
water, the former occurring in many of our rivers and the
latter abounding on the rocky parts of the coasts of the
European seas. They are bilaterally symmetrical animals,
provided with many pairs of limbs, among which the
large prehensile ‘claws’ are conspicuous. They are very
active, walking and swimming with equal ease and sometimes
propelling themselves backwards or forwards, with great
swiftness, by strokes of the broad fin which terminates the
body. They have conspicuous eyes, mounted upon moveable
stalks, at the anterior end of the head; and two pairs of
feelers, one pair of which are as long as the body, while the
other pair are much shorter.

The body and limbs are invested by a strong jointed
shell, or exoskeleton, which is a product of the subjacent
epidermis, and consists of layers of membrane which remain
soft and flexible in the interspaces between the segments
of the body and limbs, but are rendered hard and dense
elsewhere by the deposit of calcareous salts; the exoskeleton
is deeply tinged with a colouring matter Switch turns red
when exposed to the action of boiling water. The body pre-

o

X11] THE FRESH-WATER CRAYFISH. 123

sents an anterior division—the cephalothoraz—covered by a
large continuous shield, or carapace ; and a posterior division—
the abdomen—divided into a series of segments which are
moveable upon-oge another in the direction of the vertical
median plane, so that the abdomen can be straightened out,
in extension ; or bent into a sharp curve, in flexion. Of these
segments there are seven. The anterior six are the somites
of the abdomen, and each of them has a pair of appendages
attached to its ventral wall. The seventh bears no appen-
dages and is termed the telson. The anus is situated on the
ventral aspect, beneath the telson and behind the last somite.

A groove on the surface of the carapace, which is termed
the cervical suture, separates an anterior division, which
belongs to the head or cephalon, from a posterior division
which covers the thorax; and the thoracic division of the
carapace further presents a central region, which covers
the head, and wide lateral prolongations, which pass down-
wards and: cover the sides of the thorax, their free ven-
tral edges being applied against the bases of the thoracic
limbs. These are the branchiostegites. Each roofs over a
wide chamber in which the gills are contained and which
communicates with the exterior, below and behind, by the
narrow interval between the edge of the branchiostegite and
the limbs. Anteriorly and inferiorly, the branchial chamber
is prolonged into a canal, which opens in front and below
at the junction of the head with the thorax. In this canal ~
there lies a flat oval plate—the scaphognathite—which is
attached to the second pair of maxille and which plays a
very important part in the performance of the function of
respiration. Of the thoracic limbs themselves there are eight
pairs, and, on the ventral face of the body, the lines of
demarcation between the eight somites to which these limbs
belong may be observed. There is no trace of any correspond-
ing divisions in the carapace of the Lobster ; but, in the Cray-

124 ELEMENTARY BIOLOGY. [xin

fish, the last thoracic somite is incompletely united with those
which precede it. The four posterior pairs of thoracic limbs are
those by which the animal walks and are termed the ambu-
latory legs. The next pair is formed by the great claws or
chelw. The anterior three pairs are bent up alongside the
mouth and are moved to and from the median line so as to
play the part of jaws, whence they are termed foot-jaws or
masillipedes. The external or third pair of these mazxilli-
pedes are much stouter and more like the ambulatory limbs
than the rest, and the inner edges of their principal joints
are toothed. The innermost or first pair of maxillipedes are
broad, foliaceous and soft. When these foot-jaws are taken
away, two pairs of soft foliaceous appendages come into
view. They are attached to the hinder part of the cephalon
and are the jaws or mazille. The second, or outermost, is
produced, externally, into the scaphognathite, which will
be seen to lie in a groove which separates the head from
the thorax laterally and is the cervical groove.

Anterior to these maxille lie the two very stout mandibles.
Between their inner toothed ends is the wide aperture of
the mouth, bounded, in front, by a soft shield-shaped plate,
the labrum; and behind, by another soft plate, divided by
a deep median fissure into two lobes, which is the metastoma.
Thus far, the surfaces of the somites to which the appendages
are attached look downwards, when the body is straightened
out and the carapace is directed upwards. But, in front
of the mouth, the wall of the body to which the appendages
are attached is bent up, at right angles to its former direc-
tion, and consequently looks forwards. This bend of the
ventral wall of the body is the cephalic flexure. In corre-
spondence with this change of position of the surface to
which they are attached, the three pairs of appendages of
the somites which lie in front of the mouth are directed
either forwards, or forwards and upwards. The posterior

XII. | THE FRESH-WATER CRAYFISH. 125

pair consists of the long feelers or antennw: the next, of the
short feelers or antennules; and the most anterior is formed
by the short subcylindrical stalks (ophthalmites), on the ends
of which the eyes are situated.

This enumeration shews that the Lobster and Crayfish
have six pairs of abdominal appendages—the swimmerets ;
eight pairs of thoracic appendages (four pairs of ambulatory
limbs, one pair of chele, three pairs of maxillipeds), and six
pairs of cephalic appendages (two pairs of maxille, one pair
of mandibles, one pair of antenne, one pair of antennules,
one pair of eyestalks), making in all twenty pairs of append-
ages. In correspondence with the number of appendages
the body consists of twenty somites; of which six remain
moveable upon one another to form the abdomen, while the
other fourteen are united to form the cephalothorax.

The branchiostegite is an outgrowth of the dorsolateral
region of the confluent thoracic somites. The serrated rostrtm
which ends the carapace is a fixed median prolongation of
the dorsal wall of the anterior cephalic somites; while the
telson is a moveable median prolongation of the dorsal wall
of the sixth abdominal somite. The labrum and the meta-
stoma are median growths of the sterna of the przoral and
post-oral somites.

Thus the whole skeleton in these animals may be con-
sidered as a twentyfold repetition of the ring-like somite
with its pair of appendages, which is seen in its simplest form
in one of the abdominal somites. Moreover, notwithstanding
the great variety of functions allotted to the various ap-
pendages, the study of the details of their structure (see
Laboratory work) will shew that they are all reducible to
modifications of a fundamental form, consisting of a basal
joint (protopodite) with three terminal divisions (endopodite,
exopodite, epipodite).

As has been already said, the Lobster and Crayfish are

126 ELEMENTARY BIOLOGY. [X11

bilaterally symmetrical; that is to say, a median vertical
plane passing through the mouth and anus divides them into
two similar halves. This symmetry is exhibited not merely
by the exterior of the body and the correspondence of the
paired limbs, but extends to the internal organs; the alimen-
tary canal and its appendages, the heart, the nervous sys-
tem, the muscles and the reproductive organs, being disposed
so as to be symmetrical in relation to the median vertical
plane of the body.

The wide gullet leads almost vertically into the spacious
stomach, and both are lined by a chitinous continuation of the
exoskeleton. The stomach is divided by a transverse con-
striction into a spacious cardiac, and a much smaller pyloric
division, from which latter the intestine passes. The walls of
the anterior half of the cardiac sac are thin and membranous,
but, in the posterior half, they become calcified so as to give
rise to a gastric skeleton of considerable complexity. The
chief part of this skeleton consists of a median dorsal
T-shaped ossicle, the cross-piece of which forms a transverse
arch, while its Jong median process extends backwards in the
middle line, and is connected with a very strong tooth, which
projects into the gastric cavity in front of the aperture of
communication between the cardiac and pyloric divisions of
the stomach. The ends of the transverse arch are articulated
with two lateral pieces, each of which bears a similar tooth.
The extremities of these antero-lateral pieces again are arti-
culated with postero-lateral pieces, which unite with a cross-
piece which arches over the roof of the pyloric division of
the stomach. In this manner a sort of hexagonal frame with
moveable joints is formed, and the median dentigerous piece
projects backwards so far, as to end below the posterior cross-
piece. It is connected with this, however, by a short ossicle
which ascends obliquely forwards and is articulated with the

x11] THE FRESH-WATER CRAYFISH. 131

of the limbs and the consequently increased formation of
carbonic anhydride.

The mode and place of the excretion of nitrogenous
waste is not yet clearly made out, but it seems probable
that two large green glands which lie in the cephalon close
to the bases of the antennz are renal organs. Each gland
encircles the neck of a large thin-walled sac which opens
by a short canal upon the ventral face of the basal joint’
of the antenna.

The nervous system consists of a chain of thirteen
ganglia—united by longitudinal commissures—lodged in the
median line of the ventral aspect of the body, from which
nerves are given to the organs of sense, to the muscles
of the trunk and limbs, and to the integuments; and of a
visceral nervous system, developed chiefly upon the stomach.

Of the thirteen ganglia, the most anterior lies in the
cephalon, close to the attachments of the three anterior pair
of appendages, and gives branches to them and to the visceral
nervous system. Itisusually termed the brain or the suprawso-
phageal ganglion. It is connected by two commissural cords,
which pass on each side of the gullet, with a larger ganglionic
mass, which is called the subwesophageal ganglion. This occu-
pies the region of the hinder part of the cephalon and the an-
terior part of the thorax, and gives off nerves to the maxille
and the three pair of maxillipeds. Five other ganglia lie in
the five somites which bear the chele and the ambulatory
limbs, and there is one for each abdominal somite, the last
of these being the largest of the six.

The longitudinal commissures between the abdominal
ganglia are single; but, in the thorax, the commissures are
double, and the ganglia themselves show more or less evident
indications of being double. And there is reason to believe
that these thirteen apparent ganglia really represent twenty
pairs of primitive ganglia, one pair for each somite; the:

9-2

132 _ ELEMENTARY BIOLOGY. [err

three pair of prxoral ganglia having coalesced into the brain ;
and the five which follow the mouth having united into the
subcesophageal mass.

The only organs of special sense which are recognizable
in the Lobster and Crayfish are eyes and auditory organs.

The eyes are situated at the extremities of the eyestalks,
or ophthalmites, which represent the first pair of appendages
of the head. The rounded end of the eyestalk presents a,
clear, smooth area of somewhat crescentic form, divided into
a great number of small four-sided facets. This area cor-.
responds with the cornea, which is simply the ordinary
chitinous layer of the integument become transparent.
The inner face of each facet of the cornea corresponds with:
the outer end of an elongated transparent slightly conical,
hody—the crystalline cone—the inner end of which passes into
a relatively long and slender connective rod, by which it is.
united with a spindle-shaped transversely striated body—
the striated spindle. The inner extremity of this again is
connected with the convex surface of the dilated cushion-
shaped ganglionic termination of the optic nerve. The respec-
tive striated spindles, connective rods and crystalline cones,
thus radiate from the outer surface of the terminal ganglion
to the inner surface of the cornea, and each is separated from
its neighbour by a nucleated sheath, parts of which are deeply.
pigmented. Nothing is accurately known as to the manner
in which the function of vision is performed by the so-called
compound eye which has just been described. The inner and,
outer faces of the corneal facets are flat and parallel. They
therefore cannot play the part of lenses; and, if they could,
there is no trace of nerve endings so disposed as to be.
affected by the points of light gathered together in the foci.
of such lenses. Morphologically, the cones, connective rods.
and striated spindles, are in many ways analogous to those_

be

X11] THE FRESH-WATER CRAYFISH. T33

elements of the retina of the Vertebrata which make. up
the layers of rods and cones and the granular layers. These
structures are properly modifications of the epidermis;
‘inasmuch as the cerebral vesicle, of which the retinal vesicles
are outgrowths, are involutions of the epidermis of the
embryo, and, morphologically speaking, the free ends of the
rods and cones of the vertebrate eye are, as in the crustacean,
turned outwards. It seems probable, therefore, that the
crustacean eye is to be compared to the retina alone of
the vertebrate eye, and that vision is performed as it would
-be by the retina deprived of its refractive adjuncts.

The auditory organ of the Lobster and Crayfish is
situated in the basal joint of the antennule, on the dorsal
surface of which a small slit-like opening, protected by
numerous hairs, is to be seen. The chitinous layer of the
integument is invaginated at this opening, and’ thus gives
rise to a small ‘flattened sac lodged in the interior of the
antennule. One side of this sac is in-folded so as to pro-
duce a ridge, which projects into the cavity of the ‘sac,
‘and is beset with very fine and delicate hairs. The auditory
nerve enters the fold, and its ultimate filaments reach the
bases of these hairs. The sac contains water in which
minute particles of sand are suspended.

The sexes are distinct in the Lobster and Crayfish. The
external characters of the males and females and the form
of the reproductive organs are described in the Laboratory
work.

The impregnated ova are attached in great numbers, by
a viscid secretion of the oviduct, to the hairs of the swim-
-merets, where they undergo their development. A Lobster
-with eggs thus attached, is said by the fishermen to be ‘in
berry. In the Crayfish, the embryo passes through all
the stages which are needed to bring it very near to the
form of the adult before it leaves the egg: but, in the Lobster,

‘1384 ELEMENTARY BIOLOGY. [Xt

the young, when hatched, are larvee extremely unlike the
‘parent, which undergo a series of metamorphoses in order
‘to attain their adult condition. The larve may frequently
be obtained by opening the eggs of a ‘hen-lobster’ in ‘berry.’
They have a rounded carapace, two large eyes, a jointed
‘abdomen devoid of appendages; and the thoracic limbs are
‘provided with long exopodites.

The ordinary growth, no less than the metamorphoses
of the Lobster and Crayfish, are accompanied by periodical
castings of the outer, chitinous, layer of the integument.
After each such ecdysis, the body is soft and the animal re-
tires into shelter until the ‘shell’ is reproduced.

LABORATORY WORK.

1. General external characters,

The animal is covered by a dense exoskeleton: in it
are readily recognised the following parts :—

a. The body proper:

a, Its anterior unsegmented portion (cephalotho-
raz): the great shield-like plate (carapace)
covering the back and sides of the cephalotho-
rax; the groove across the carapace (cervical
suture) marking out the line of junction of
head proper and thorax: the anterior prolonga-
tion of the carapace to form the frontal spine.

8. The posterior segmented portion (abdomen):
its seven divisions; the anterior six much like.
one another; the most posterior (telson) different
from the rest.

X11] THE FRESH-WATER CRAYFISH. 135

@ 5. The great number of jointed limbs (appendages)
attached to the ventral aspect of the body: their
varying characters in different regions.

c. The external apertures of the body.

a. The mouth; seen by separating the append-
ages beneath the head.

The anus; a longitudinal slit beneath the telson.

y. The paired genital openings: in the male, on
the first joints of the last pair of appendages
of the thorax: in the female, on the first joints
of the last thoracic appendages but two.

[8. The openings of the auditory organs.[ <<. 8° ~ 4]
«. The openings of the green glands, ~~ 35"’7~':
These will be more readily found when the ap-

pendages on which they are situated have been
separated. See 21. fand g.]

ie)

Examine carefully the third abdominal segment or
somite and its appendages.

a. The segment proper: arched above; flattened
below. .

a. Its dorsal part (tergum), with an anterior smooth
portion overlapped by the preceding segment
in extension of the abdomen, and a posterior
rougher part overlapping part of the succeed-
ing segment.

B. ‘The ventral surface of the segment: united
with the corresponding portions of the preced-
ing and succeeding segments by a flexible
membrane.

1

6

ELEMENTARY BIOLOGY. [sit

y. The point of union of the appendages with
the somite.

5. The sternum: that portion of the ventral sur-
face of the somite which lies between the
points of attachment of the appendages.

e. The epimeron: the portion of the ventral surface
which lies on each side external to the attach-
ment of the appendage.

This region is very short and passes almost
directly into the inner walls of the pleuron.

¢ The downward extension (plewron) of the
lateral walls of the somite formed by the pro-
longation of the tergum and epimeron:. the
smooth facet on the anterior half of the
pleuron where it is overlapped by the one in
front.

b. The appendages or swimmerets: one on each side:
the structure of each—

a. The short eesinica basal portion Copii:
dite), consisting of a. shorter proximal and a
longer distal piece.

‘8. The antero-posteriorly flattened elongated la-
melle attached to the distal joint of the
protopodite, an inner (endopodite) and outer
(exopodite).

The fourth and fifth abdominal segments: closely
resembling the third.

The sixth abdgminal segment: its modified append-
ages.

xIr.]

THE FRESH-WATER CRAYFISH. 137

a The protopodite: represented by a single short
strong joint. (In the lobster there is an in-
complete basal joint.)

B. The exopodite and endopodite: wide plates
fringed with sete: the exopodite divided into
two portions by a transverse joint.

The telson.

A flattened plate bearing no appendages: sub-
divided by a transverse joint (it is undivided in
the lobster) : the membranous character of the greater
part of the ventral surface of its anterior division.

The tazl-fin ; formed by the telson and the append-
ages of the sixth abdominal segment.

The second abdominal segment.

Closely resembling the third in the female: in the
male its appendages are modified: the protopodite
and basal joint of endopodite much elongated, and the
latter produced into a plate rolled upon itself so as
to form a demicanal, concave inwards. (In the lobster
the endopodite is produced inwardly, into an oval
process.)

The first abdominal segment: its appendages; rudi-
mentary in the female (it has only one instead of
two terminal divisions in the lobster): in the male
consisting of a single plate rolled in upon itself. (In
the lobster the single terminal division has the form
of a flat scoop or a narrow spoon with its concave side
turned inwards.)

The structure of the cephalothoraz.

a, Note again the carapace, with its avontal spine
and cervical suture.

138

10.

ELEMENTARY BIOLOGY. [ XII.

Turn the animal over and note the very
narrow sterna between the points of attach-
ment of the thoracic appendages.

The last thoracic somite is not ankylosed

with the rest in the crayfish. In the lobster
it is.
Raise with a pair of forceps the free edge of
the lateral part of the carapace which lies just
over the bases of the thoracic appendages, and
is termed the branchiostegite: note that it is
formed by the large united pleura of the
thoracic segments, and overlaps a chamber in
which the gills lie.

Note the plane in which the sterna of the anterior
three somites of the animal (marked out by their
appendages) lie—it is nearly at right angles to the
plane of the remaining sterna of the cephalothorax—
so that their appendages are directed forwards in-
stead of downwards.

Cut a vertical section of a piece of the exoskeleton
which has been decalcified by lying in 12 chromic
acid solution for a few days.

a.

It will be seen to be composed of a large number
of parallel laminz which are thicker towards
the outer part. The lamine are marked by ill-
defined parallel lines which run perpendicular to
the surface, and which give their edges a striated
appearance. The outermost layer is more trans-
parent than the rest and wants this striation.

The epidermis lying beneath the innermost of the
above laminz is composed of ill-defined branched

‘nucleated granular cells: the outermost giving off

a large number of short processes which end in

XII.]

THE FRESH-WATER CRAYFISH. 139

clubbed ends and penetrate a short way into the
exoskeleton. fee eae

Peas pam

11. The respiratory organs. Remove now the branchio-

12.

_ stegite on one side and examine the gills: they are

18 in number, arranged in two sets.

a

[3

Six are attached to the epipodites of some of
the appendages (2nd and 3rd mazxillipedes,
chelz, Ist, 2nd, and 3rd pair of ambulatory
limbs).

The remaining 12 are fixed to the sides of
the body, and each consists of a central stem
giving off a number of delicate filaments,

Cut away the gills, noting the two large chan-
nels in the stem of each, and observe the
cervical groove at the front of the gill-chamber
with the scaphognathite (21. d. a.) lying in it.
In the lobster there are 20 gills on each side,

arranged as in the crayfish, except that there are
14 on the side of the body.]

Circulatory organs. Immerse the animal in water
with its ventral surface downwards: cut away care-
fully with a pair of scissors the dorsal part of the
carapace which lies behind the cervical suture and
that part of the wall of the thorax from which the
gills have been removed.

A chamber (the pericardial sinus) is thus laid bare
in which lies a polygonal sac, the heart.

a

\

The six openings from the sinus into the heart ;
two superior, two inferior, and two lateral: pass
bristles into them. The arteries arising from the
heart; five anterior, one (ophthalmic) single’ in
the middle line, the others (antennary and hepatic)

140

ELEMENTARY BIOLOGY. [xit.

in pairs; one, the sternal, the largest of all, given
off from the posterior end.

Cut away the terga of the abdominal somites and
follow back the superior abdominal branch of the
sternal artery, removing carefully the muscles

‘ which lie over it in the abdominal region. It

will be seen as a transparent tube lying in the

middle line on the intestine (14. b.), or in the

female lobster separated from it anteriorly by

-the. posterior ends of-the two ovaries. It gives

off branches from its upper side to the muscles
over it, and also a pair of branches which run out
laterally in the intervals between each pair of so-
mites. In the sixth abdominal somite it termi-
nates by splitting up into three or four large
branches which pass in a radiating manner into
the telson. On account of the small size of the
crayfish this artery is difficult to dissect in it.

The sternal artery presents an enlargement at its
commencement just where the above branch arises
from it. It then passes vertically downwards to-
wards the ventral surface, passing on one side of
the intestine. Its subsequent course must be fol-
lowed later (15).

13. Reproductive organs..

These differ considerably in the crayfish and the lob-

They lie partly beneath the heart, which must

therefore be removed or pushed on one side in order
_tosee them. Both animals are unisexual.

»

Of the crayfish.

The testis. A trilobed yellowish mass: two of
its lobes are larger than the third and pass for-

XIL.]

b.

a

THE .FRESH-WATER CRAYFISH.. 141

wards side by side in the middle line: the
third lobe is directed backwards.

The two vasa deferentia arise just where the
posterior lobe of the testis meets the two ante-
rior. Each is narrow near the gland, but widens
as it proceeds back from it, and becoming ex-
tremely convoluted, finally ends at the genital
opening on its own side (l.c.y.). Trace the
course of the vas deferens on that side from
which the thoracic wall has been removed (12).

Tease out a bit of the testis in ‘water, and ex-
amine with $ obj: it will be seen to be com-
posed of sacculated tubes. In it or in the vas
deferens some of the spermatozoa may. be found:
they are motionless and have the form of nucle-

_ ated cells provided with radiating processes.

The ovary is a gland in shape and. colour
very similar to the testis of the male. From it
two short oviducts arise and pass almost directly
downwards to the genital openings (1. ¢.¥.).

Of the Lobster.

The testes are two long tubes which lie partly
in the thorax and partly in the abdomen. Their
posterior portions meet in the middle line, but
in front they diverge, and about one fourth the
length of each from its anterior end a short

transverse branch unites the two.

The vas deferens arises a little in front of the
middle of each testis and passes without convo-
lutions towards the genital opening., Its distal
half is dilated.

ELEMENTARY BIOLOGY. [XL

Tease out a bit of the testis in water and ex-
amine with } obj. for spermatozoa. They are
motionless, and consist of an elongated cell from
one end of which three rigid pointed processes
radiate.

The ovaries of the lobster are also elongated
and lie partly in the thorax and partly in the
abdomen, above the alimentary canal (14).
Each is a black mass, on the exterior of which
minute rounded eminences (indications of the
contained ova) can be seen. Near their ante-
rior ends they lie in contact in the middle line,
and for a short distance their substance is ‘con-
tinuous.

An oviduct arises from each ovary a little in
front of its middle, and passes directly to the
genital opening of its own side (1. c. 7.).

14. Alimentary organs.

a.

a

Remove the dorsal part of the carapace in front
of the cervical suture, and there will then be
laid bare, in front of the position of the heart, a
large sac—the stomach ; pass a probe into it along
the gullet, through the mouth-opening which lies
between the mandibles.

Trace back the tubular intestine from the stomach
to. the anus. It dilates near the latter in the
lobster. In the crayfish it presents a small cecal
diverticulum close to the,stomach, and in the
lobster one near the anus. —

Examine the liver.

It is an elongated soft pale-yellow mass lying
in each side of the cephalo-thorax, and opening

Br,
¥

XIL.]

15.

THE FRESH-WATER CRAYFISH. 143°

by a duct on each side at the point where the
intestine joins the stomach.

8. Tease out a bit of the liver in water; it is
made up of branched cxcal tubes, which when
examined microscopically are seen to be lined
by a layer of cells (epithelium).

d. Carefully remove the alimentary canal, cutting
the gullet through close to the stomach.

a, Open the latter under water and make out in
it the constriction which divides it into an
anterior (cardiac) portion and a_ posterior
(pyloric).

8. The supporting bars and the hairs in the
stomach, and the calcifications of its lining
membrane.

Now trace the sternal artery (removing the ali-
mentary canal and the genital organs), until it enters
a passage (sternal canal) formed by ingrowths of the
exoskeleton near the ventral surface oe the animal.
Just before entering this the sternal artery gives
off the inferior abdominal branch, which runs back
along the middle line of the abdomen immediately
inside the sterna of the somites. Trace this branch
back removing the muscles which cover it. By this
proceeding the abdominafpart of the nervous chain
will be exposed. It lies immediately above the blood-
vessel and is not to be injured.

16. The nervous system. aha

a. Find the supracsophageal ganglion in front of
the gullet.

B. The circumesophageal commissures passing
back from it.

144

ELEMENTARY BIOLOGY. (Xan.

y. Follow back these commissures, cutting away
the hard parts (forming the roof of the sternal
canal) which come in the way; they lead to
a chain of six ganglia, lying along the floor of
the cephalothorax, and united by double cords
(commissures). Lying in the sternal canal be-
neath the ganglia may be seen une _ sternal
artery (15).

5. Follow back the single cord proceeding from
the last thoracic ganglion to the* abdomen,
removing any muscles which come in the way:
it will lead toa chain of six ganglia, one for
each abdominal ‘segmént, united by single
cords. ° i

17. The green gland. A soft greenish mass lying on

18.

19.

- 20.

each side in the extreme front part of the cephalo-
thoracic cavity: pass a fine bristle into it from the
opening of its duct on the basal joint of the endo-
podite of the antenna (21. f). :

Tease out a bit of muscle in water and examine
it microscopically: note-its structure ;-it is made up
of fibres, marked by regularly alternating transverse
lighter and darker bands.

Tease out a bit of perfectly fresh nerve-cord in water
and stain with magenta or hematoxylin. ,

a. Composed of slender fibres of varying size,
each consisting of a structureless outer wall,
on which are nuclei at intervals, surrounding a
clear or, sometimes, finely g granular or obscurely
fibrillated central axis,

Tease out in water a ganglion which has been treated
with osmic acid.

a.

THE FRESH-WATER CRAYFISH. 145

&
Composed of large oval branched cells, each con-
sisting of a granular mass in which lies a clear
round nucleus, containing a nucleolus,

The appendages, Beginning with the sixth abdomi-
nal segment, remove with forceps the appendages of
the body and arrange them in order on a piece of
cardboard. ‘The abdominal appendages have been
already described; note the following points in the
remainder, working from behind forwards.

a

vy -

The four posterior thoracic appendages (ambu-
latory appendages).

The most posterior: elongated and _ seven-
jointed, the joints working in different planes
so that the limb as a whole can move in any
direction : the joints have the following names;
the proximal, short and thick, coxopodite ; the
next, small and conical, basipodite ; next, cylin-
drical and marked by an annular constriction,

. ischtopodite; the next, longer, meropodite ; then

successively, the carpopodite, propodite, and
dactylopodite.

The next ambulatory leg: generally similar
to the preceding, but possessing, attached to
the coxopodite, a long membranous flattened
appendage (epzpodite) which ascends into the
gill-chamber : it bears a gill

The next anterior ambulatory leg: differing
from the Jast only in having its propodite
prolonged so as to be opposable to the dac-
tylopodite and form a pair of forceps (chelce).

The most anterior ambulatory leg: resembling
y. closely and, like it, bearing a gill.
10

b.

C.

d.

y.

ELEMENTARY BIOLOGY. [Xu1.

The great chele: closely resembling .the last
appendage in structure, but much larger and

more powerful ; it carries a gill.

The three maxillipedes.

The most posterior: its short thick basal
joint (protopodite): the three prolongations
articulated to it; the external (epipodite) a
curved elongated lamina lying in the branchial
chamber and bearing a gill; the middle one
(exopodite) long, slender and many-jointed;
the internal one (endopodite) several-jointed
and much resembling one of the ‘ambulatory
limbs.

The middle maxillipede: much like a. but
with a less stout endopodite.

The anterior maxillipede ; protopodite, exopo-
dite and epipodite much like those of @. but
smaller and the epipodite bearing no gill; the
endopodite flattened and foliaceous.

The ambulatory limbs, great chela, and max-
illipedes together constitute the appendages of
the thorax; we now come to those of the head

proper.
The two mactlle.

The posterior: its basipodite and endopodite
essentially like those of the anterior maxilli-
pede; the epipodite and exopodite united and
forming a wide oval plate (scaphognathite)
which lies at the anterior end of the gill-
chamber (11. ¥.).

"SIL |

h,

THE FRESH-WATER CRAYFISH. 147

8. Anterior maxilla: epipodite and exopodite

undeveloped: the endopodite foliaceous.

The mandible. Its strong toothed basal joint
(protopodite) bearing a small appendage (the palp)
which represents the endopodite; the epipodite
and exopodite unrepresented.

The antenna. Its two-jointed basal portion (proto-
podite) bearing a flattened plate (the rudimentary
exopodite) and a long multiarticulate filament (the
endopodite): the opening of the green gland (17)
on the oral side of the basal joint of the proto-
podite.

The antennula. Its large trigonal basal joint
( protopodite), bearing a pair of jointed filaments
(endopodite and exopodite): the opening of the
auditory organ (24) in the midst of a minute
hairy tuft on the basal joint.

The ophthalmites or eye-stalks. Short two-jointed
appendages representing only the basipodite.

. Now work back over the 20 pairs of appendages

and compare each with the second maxillipede: all
may be supposed to be derived from it by suppression,
coalescence or special change of form; it is what is

called a typical ‘appendage. a a es:
Structure of the Hye.
a. Take the eye of a lobster which has lain four or

five days in 0°5 per cent. solution of chromic acid
and then twenty-four hours or more inalcohcl. Ex-
amine its surface with one inch obj. with reflected
light. It will be seen to be marked out into a
10—2

148

i

ELEMENTARY BIOLOGY. [XII

great number of minute square areas or facets,
each of which shews faint signs of furrows crossing .
it diagonally from corner to corner.

Imbed the eye and cut a number of sections from
it perpendicular to its surface: mount in glycerine
and examine with one inch objective.

If the section has passed through the middle of
the eye it will be seen to present a central mass
(optic ganglion) from which a number of lines
appear to radiate to the facets on the surface.
These radiating lines (which are obscured here
and there by pigmented layers) are indications
of the striated spindles, connective rods and
crystalline cones.

Examine your thinnest section with a high power,
or tease out one of your thicker ones in gly-
cerine. Beginning at the exterior make out suc-
cessively—'

The cornea, answering to one of the superficial
facets. Its flat outer and slightly convex inner
surface. Immediately beneath the cornea there
will be seen (in good specimens) a slightly
granular layer.

The crystalline cone, an angular transparent
body which is usually obscured by pigment. If
this is the case, another section must be mounted
in dilut -austic potash, which removes the
pigment.

Behind the crystalline cone comes the con-
nective rod. It is widest in front where
it joins the cone but narrows posteriorly
where it is continuous with the striated. .

X11]

THE FRESH-WATER CRAYFISH. 149°

spindle. If fresh eyes be treated with osmic
acid and then teased out, each of these rods
can be split up into four fibres.

The striated body is fusiform and presents
well-marked transverse striations. Besides
these coarse striations, however, much finer
ones can be seen by careful examination witha
high power. The outer ends of these spindles
correspond in position to the second of the pig-
mented layers seen with the low power (8. a.):
they are best seen in specimens treated with
dilute caustic potash.

Beneath the striated spindles is a perforated
membrane through which the spindles pass to
become continuous with the optic ganglion.
From their ends pass nerve-fibres which run
inwards in a converging manner and among
which nerve-cells are here and there scattered.
Within: the ganglion ‘are several concentric
pigmented bands.

If the section has passed back along the
optic nerve two obliquely placed lenticular
masses will be seen among its fibres.

Passing back from the cornea to the optic
ganglion is a membrane investing each cone,
rod, and spindle. It is on this that most of the
pigment lies which causes the two outer dark
bands. Over the rodsethe pigment is wanting
and there the membrane is seen to possess oval
nuclei.

24, The Auditory organ.

This lies in the basal joint of the antennule and is
best examined in the lobster. The upper surface of

150

ELEMENTARY BIOLOGY. ~- [XIL

this basal joint is flat posteriorly and joins in front
at an angle a rounded anterior portion. It bears
several tufts of hairs: one of these is very small and
lies at the inner side: of the flattened surface, just at
the angle where it meets the rounded part; among
these hairs is the opening into the auditory sac, through
which a bristle can easily be passed.

a.

¢C.

Take a fresh antennule from a lobster and cut
away the under surface of its basal joint. A chi-
tinous transparent sac will readily be found in it,
among the muscles &c.; this is the auditory sac
and is about 4 of an inch long. Carefully dissect
itout.

If this sac be held up to the light a little patch
of gritty matter will be seen on its under surface
near the aperture to the exterior. Behind this
can be seen a curved opaque line; behind this,
and concentric with it, a shorter brownish streak,
Cut out carefully the part of the sac which bears
these streaks: mount in sea-water or sodic chloride
solution and examine with one inch objective.

The white line will be seen to answer to a
ridge on the apex of which is a row of large
hairs, and both on the brown patch and on the
opposite side of the main row will be seen
scattered groups of smaller hairs.

Examine with 4 obj.

Each of the hairs seen with the lower power is
now seen to be covered over its whole surface
with innumerable very fine secondary hairs;
these are shortest near the base of the primary
hair. Towards its base each of the primary

XI

“THE FRESH-WATER CRAYFISH. 151

hairs is constricted and then dilates into a
. bulbous enlargement which is fixed to the
wall of the sac.
The brown patch is seen to owe its colour to a
single layer of polygonal epithelial cells con-
taining pigment granules.
By focussing through this epithelial layer a
number of parallel slightly granular bands is
seen passing up, one to the base of each hair in
the main rew on the top of the ridge. At the
base of the hair to which it runs, each band is
constricted and, entering the bulbous enlarge-
ment of the hair, joims a small hemispherical
swelling within it.
If a fresh auditory sac be put in 1 per cent.
solution of osmic acid for half an hour, and
then laid for twenty-four hours in distilled
water and examined, each of the granular
bands mentioned above is seen to consist of
a bundle of fine fibres which swell out into
fusiform enlargements at intervals.
A great part of the whole interior of the audi-
tory sac of the lobster is covered with very fine
hairs which can only be seen with a high
power. Epithelium is absent except the pig-
mented patch above mentioned.

The auditory sac in the crayfish is very similar to
that in the lobster, and may be examined in a
similar way. It is however not so good, both oa
account of its smaller size and because the audi-
tory hairs, although longer, are collected in a close
tuft, which makes it more difficult to see the
manner of their insertion.

XIII.

THE FROG (Rana temporaria and Rana esculenta).

THE only species of Frog indigenous in Britain is that termed
the ‘common’ or ‘Grass Frog’ (Rana temporaria), while, on
the Continent, there is, in addition to this, another no less
abundant species, the hind-limbs of which are considered a
delicacy, whence it has received the name of the ‘Edible
Frog’ (Rana esculenta). Unless the contrary be expressly
stated, the description here given applies to both species.
The Edible Frog is usually larger than the other, and is
therefore more convenient for most anatomical and physiolo-
gical purposes.

In the body of the Frog the head and trunk are readily
distinguishable ; but there is no tail and no neck, the con-
tours of the head passing gradually into those of the body,
and the fore-limbs being situated immediately behind the
head. There are two pairs of limbs, one anterior and one
posterior. The whole body is invested by a smooth moist
integument, on which neither hairs, scales, nor other forms of
exoskeleton are visible; but hard parts, which constitute the
endoskeleton, may readily be felt through the integument
in the head, trunk and limbs.

The yellowish ground-colour of the skin is diversified by
patches of a more or less intense black, brown, greenish, or
reddish-yellow colour, and, in the Grass Frog, ‘there is a
large, deep brown or black patch on each side of the head,

XII] THE FROG. 153

behind the eyes, which is very characteristic of the species.
The coloration of different frogs of the same species differs
widely; and the same frog will be found to change its colour,
becoming dark in a dark place, and light if exposed to the
light.

The body of the Frog presents only two median aper-
tures, the wide mouth and the small cloacal aperture. The
latter is situated at the posterior end of the body, but rather
on its upper side than at its actual termination. It is
commonly termed the anus, but it must be recollected that
it does not exactly correspond with the aperture so termed
in the Mammalia.

The two nostrils, or external nares, are seen at some dis-
tance from one another upon the dorsal aspect of the head,
between the eyes and its anterior contour. The eyes are
large and projecting, with well-developed lids, which shut
over them when they are retracted; and, behind the eye,
on each side of the head, there is a broad circular area
of integument, somewhat different in colour and texture
from that which surrounds it; this is the outer layer of the
membrane of the tympanum, or drum of the ear.

The fore-legs are very much shorter than the hind-legs.
Each fore-limb is divided into a brachium, antebrachium and
manus, which correspond with the arm, fore-arm and hand in
Man. The manus possesses four visible digits which answer
to the second, third, fourth, and fifth fingers in Man. There
is no web between the digits of the manus.

The hind-legs are similarly marked out into three divi-
sions, femur, crus, and pes, of which the femur answers to
the thigh, the crus to the leg, and the pes to the foot, in
Man. The pes is remarkable not only for its great relative
size as a whole, but for the elongation of the region which
answers to the tarsus in Man. It will be observed, however,
that there is no projecting heel. There are five long and

154 ELEMENTARY BIOLOGY. [ XII.

slender digits, which correspond with the five toes in Man,
and: are united together by thin extensions of the integu-
ment constituting the web. The innermost and shortest
auswers to the hallua, or great toe, in Man.

At the base of the hallux, the integument of the sole
presents a small horny prominence, and sometimes there
is a similar but smaller: elevation on the outer side of the
foot: but there are no nails upon the ends of any of the digits
of either the pes or the manus. Thickenings, or callosities,
of the integument, however, occur beneath the joints of the
digits, both in the pes and the manus.

During the breeding season, the integument on the
palmar surface of the innermost digit of the manus, in the
male, becomes converted into a rough and swollen cushion,
which, in the Grass Frog, acquires a dark-brown or black
colour.

The Frog, when at rest, habitually assumes a sitting pos-
ture much like that of a dog or cat. Under these circum-
stances the back appears humped, the posterior half being
inclined at a sharp angle with the anterior half. The ver-
tebral column, however, will be found to be straight, and the
apparent hump-back arises, not from any bend in the
vertebral column, but from the manner in which the long
iliac bones are set on to the sacrum.

The walk of the Frog is slow and awkward, but it leaps
with great force, by the sudden extension of the hind-limbs,
and it is an admirable swimmer.

In a living Frog, the nostrils will be seen to be alter-
nately opened and shut, while the integument covering the
under side of the throat is swollen out and flattened. The
alternate pumping in and expulsion of the air needed for
the Frog’s respiration is connected with these movements.

The upper eyelid of the Frog is large and covered with
ordinary pigmented integument, and it has very little mobility.

XIU] . THE FROG. ; 15!

What performs the function of the lower eyelid in Man, is <
fold of the integument of which very little is pigmented anc
which is, for the most part, semi-transparent, so as to re
semble the nictitating membrane of a bird rather than ar
ordinary lower lid. If the surface of the cornea be touched
the eyeball is drawn inwards under the upper lid, whicl
descends a little, at the same time as the lower lic
ascends over the ball, to meet the upper lid and close the eye.

As is well known, Frogs emit a peculiar croaking sound
their vocal powers being more especially manifested in the
breeding season, when they collect together at the surface o
ponds, pools and sluggish streams, in great numbers. At thi:
season, which commences in the early spring for the Gras:
Frog, but much later on in the year for the Edible Frog, the
male seeks the female and, clasping her body tightly witk
his fore-limbs, remains in this position for days or ever
weeks, until her ova are discharged, when he fecundates ther
by a simultaneous out-pouring of the seminal fluid. Shortly
after the eggs pass into the water, the thin layer of viscid
albumen, secreted by the oviduct, with which each egg is
surrounded, swells up by imbibition and, with that which
surrounds the others, it gives rise to a gelatinous mass in
which the eggs remain imbedded during the early stages of
their development.

The development of the eggs is closely dependent upon
temperature, being greatly accelerated by warmth and re-
tarded by cold. The process of yelk-division, which com-
mences within a few hours of impregnation; is readily
observed when the eggs are examined as opaque objects
under a low power of the microscope.

While still within the egg the embryo assumes the form
of a minute fish, devoid of limbs and with only rudiments of
gills, but provided with two adhesive discs on the ventral
side of the head behind the mouth,

156 ELEMENTARY BIOLOGY. [XuI.

After leaving the egg, the young acquires three pairs of
external branchie having the form of branched filaments, at-
tached to the sides of the hinder part of the head. Narrow
clefts in the skin at the roots of the branchize lead into the
back of the throat. Water taken in at the mouth passes out
by these branchial clefts. The animal crops the aquatic
plants on which it lives, by means of the horny plates with
which its jaws are provided.

In the Tadpole, as the larval Frog is called, the intestine,
which is relatively longer than in the adult, is coiled up like
a watch-spring in the abdominal cavity. A membranous lip,
the surface of which is beset with numerous horny papille,.
surrounds the mouth, and the muscular tail acquires a large
relative size. The eyes, the nasal and auditory organs
become distinct, but no limbs are at first visible.

A fold of the integument in the hyoidean region, called
the opercular membrane, now grows back over the external
gills and unites with the integument covering the abdomen,
leaving only a small aperture on the left side, through which
the ends of the external gills of that side may, for some time,
be seen to protrude. The external gills atrophy and are suc-
ceeded functionally by short processes developed from the
opposing faces of the branchial clefts—the internal branchie.
The rudiments of the limbs appear, rapidly elongate and take
on their characteristic shape, the hind pair only being at first
visible on account of the anterior pair being hidden under the
opercular membrane. The lungs are developed and, for a time,
the tadpole breathes both by them and by its internal gills.

As the legs grow the tail shortens and, at last, is re-
presented merely by the pointed end of the body; the gape
elongates until the angle of the mouth lies behind the eye,
instead of a long way in front of it, as in the tadpole; the
labial membrane and. the horny armature of the mouth
disappear, while teeth are developed in the upper jaw and.on

X11] THE FROG. 15%

the vomers; the intestine becomes less and less coiled as, no:
growing at the same rate as the body, it becomes relatively
shorter; and the animal gradually changes its diet from
vegetable to animal matters—the perfect Frog being insecti:
vorous.

The two species, Rana temporaria and Rana esculenta, ar
distinguishable by the following external characters. Ih
Rana temporaria, the interspace between the eyes is flat o:
slightly convex, and its breadth is usually greater than, o:
at least equal to, that of one of the upper eyelids. Th
diameter of the tympanic membrane is less than that of th
eye, often much less. The horny elevation on the outer sid
of the pes is small or absent, and that on the inner i
flattened and has a rounded margin. A patch of dart
colour extends from the eye backwards over the tympani:
membrane. The males have the cushion on the radial sid
of the manus black, and they are devoid of vocal sacs.

In Rana esculenta, on the other hand, the interspace be:
tween the eyes is usually concave and narrower than thc
breadth of one of the eyelids, The diameter of the tym
panic membrang’is as great as that of the eye. The horn}
elevation on the inner side of the pes is elongated, com.
pressed and brought to a blunt edge, so as almost to resembk
a spur, and a small outer elevation is constantly present
-There is no patch of colour atthe sides of the head, suck
as exists in Rana temporaria, and the cushion of the inne
digit in the male is not black. The males have a large
pouch on each side of the head, behind the angle of the jaw
communicating with the cavity of the mouth, and, wher
.they croak, these pouches becoming dilated assume the form
of spherical sacs.

Having thus become acquainted with the general characte
and life-history of the Frog, and with those features of its

158 ‘ELEMENTARY BIOLOGY. [ XIII.

organization which are visible to the naked eye and without
dissection, its structure may next be studied in detail.

If the abdomen be laid open, it will be found to enclose a
cavity in which some of the most important viscera,—the
stomach and intestine, the liver, the pancreas, the spleen,
the lungs, the kidneys and urinary bladder, and the repro-
ductive organs—are contained. As this cavity answers to
those of the pleurze and of the peritoneum in the higher
animals, it is termed the pleuroperitoneal cavity; and the soft
smooth membrane which lines it and covers the contained
viscera is the pleuroperitoneal membrane.

The vertebral column traverses the middle of the roof of
this cavity, and the layer of pleuroperitoneal membrane which
lines each lateral wall of the cavity, passes downwards on
each side of the vertebral column and joins its fellow in the
middle line to form a thin sheet, the mesentery, which sus-
pends the intestine. In the triangular interval left between
these two layers before they unite, a wide canal—the subverte-
bral lymph sinus—the dorsal aorta, and the chain of sympa-
thetic ganglia, are situated.

The dorsal moiety of the anterior end of the pléuroperi-
toneal cavity is occupied by the gullet, which places the
mouth in communication with the stomach. Beneath the
gullet the peritoneal cavity is separated only by a thin partition
from a chamber, the pericardium, which contains the heart.
The posterior face of the partition is constituted by the peri-
toneum, its anterior face by a membrane of similar character,
the pericardial membrane, which lines the pericardium and
is reflected on to the heart, in the same way as the peritoneum
lines the peritoneal cavity and is reflected on to the intestine.

A layer of the muscular fibres which enter into the walls
of the abdomen, is continued inwards at the anterior boundary
of the pleuroperitoneal cavity and is attached to the sides of
the cesophagus and to those of the pericardium, thus consti-

XL] THE FROG. 159

tuting a rudimentary diaphragm ; which, it will be observed,
is situated in front of the lungs, and not behind them, as in
the higher animals.

Thus, in the trunk, on the ventral side of the vertebral
column, the body presents two cavities, one large posterior
pleuroperitoneal cavity, and one small, anterior to the fore-
going, the pericardial cavity, and neither of these communi-
cates directly with the exterior, though in the female there
is an indirect communication by the oviducts.

On the ventral side of the head, the very wide mouth
opens into a spacious buccal cavity, the roof of which is hard
and firm, while the floor is soft and flexible, except so far as
the middle of it is occupied by a broad, flat, for the most part
‘gristly plate, the body of the hyoid bone. Within the lips
-the upper jaw is beset with numerous sharp small teeth, and
two clusters of similar teeth are to be seen in the fore part of
the roof of the mouth; the latter, being attached to the bones
termed the vomers, are the vomerine teeth, while the former,
attached to the premazille and mazille, are maxillary teeth.
The lower jaw or mandible bears no teeth.

At the sides of the clusters of vomerine teeth are the
apertures termed posterior nares, by which the nasal chambers
communicate with the mouth. At the sides of the back part
of the throat two wide passages, the Mustachian recesses, lead
into the tympanic cavities, which are closed externally by the
tympanic membranes. In the male Rana esculenta the small
apertures of the vocal sacs are seen on the inner side of each
ramus of the javv, close to the angle of the gape and nearly
opposite the Eustachian recesses. In the middle of the back
of the throat is the opening of the cesophagus, closed by the
approximation of its sides except during deglutition, while in
the median line of the hinder part of its floor lies a longitu-
dinal slit, the glottis, A fleshy tongue, bifurcated and free
at its posterior end, is attached anteriorly to the middle part

160 ELEMENTARY BIOLOGY. [XIII

of the lower jaw. In a state of rest, therefore, it lies on
the floor of the mouth with its free end turned backwards,
and one point on each side of the glottis.

The gullet, after traversing the diaphragm, passes into
the elongated stomach. At its posterior end this narrows
and joins the slender small intestine. Though short, this is
too long relatively to the length of the abdominal cavity to lie
straight in it. It is, therefore, thrown into sundry folds
which are suspended to the dorsal wall of that cavity in the
manner before described. Finally, the small intestine enters
the suddenly dilated short large intestine, and this opens into
a chamber with muscular walls, the cloaca, the external
aperture of which has been already mentioned.

Thus the alimentary canal is a tube which traverses the
body from the oral to the anal apertures; and the heart, en-
closed in the pericardium, is situated in the middle line on
‘the ventral side of the alimentary canal.

Separated from the pleuroperitoneal and oral cavities by
the bodies of the vertebrae and the hard roof of the oral
chamber which continues the direction of these forwards, is
an elongated cavity, widest in the head but becoming very
narrow posteriorly, which is closed on all sides by the bony
and other elements of the head and spinal column. This is
the neural cavity and contains the brain and spinal cord,
which together constitute the cerebro-spinal nervous axis.
The neural cavity is lined by a serous membrane resembling
the peritoneum and the pericardium, and this arachnoid
membrane is reflected on to and covers the contained
cerebro-spinal axis, so that the latter is related to it as the
heart is to the pericardial membrane.

The cerebro-spinal nerves which are given off from the
brain and spinal cord pass to their destination through the
boundary walls of the neural cavity.

A transverse section of the head in the region of the eyes

XII.] THE FROG. 161

will shew, in the middle line, a dorsal cavity in which the
anterior part of the cerebro-spinal axis, the brain, is contained,
separated by the solid floor of the skull from a ventral cavity,
the mouth.

A transverse section of the abdomen will shew a dorsal
cavity containing the posterior part of the cerebro-spinal |
axis, the spinal cord, separated by the solid floor of the ver-
tebral column from a ventral cavity containing the ali-
mentary canal and continuous with that of the mouth.
But the backward continuation of the alimentary canal is
embraced by the large pleuroperitoneal chamber, of which
there is no indication in the head.

On comparing the transverse section of the abdomen of
the Frog with a transverse section of the middle of the body
of the Lobster, it will be seen that while the chief nervous
centre is on one side of the alimentary canal and the heart
on the opposite side in both cases, there is no solid and com-
plete partition between the nervous centre of the Lobster
and the alimentary canal. Moreover, the face of the body
on which the nervous centre lies, is that on which the Lobster
naturally rests, while in the Frog it is the reverse. The limbs
are turned towards the neural side in the Lobster and away
from it in the Frog, and the like difference obtains between
all Vertebrata and all Arthropoda.

Using the term skeleton, in its broadest sense, for the
framework which protects, supports and connects the various
parts of the organism, it consists in the Frog of four kinds of
tissue; the Horny, the Osseous, the Cartilaginous and the Con-
nective, Moreover, the hard parts are either developed in the
integument, constituting an exoskeleton, or they are deeper
seated and belong to the endoskeleton.

Leaving aside a question that may arise as to the nature
of some of the cranial bones, the exoskeleton in the Frog is

M. ll

162 ELEMENTARY BIOLOGY. [X1II.

almost absent, being represented only by the horny coating of
the calcar.

The endoskeleton, on the contrary, is well developed and,
as in all the higher Vertebrata, may be distinguished into an
axial and an appendicular portion.

The axial endoskeleton consists of the notochord, the spinal
column and the skull.

The appendicular endoskeleton occurs in the limbs and in
the pectoral and pelvic arches to which they are attached.

Tn the order of development, the endoskeleton is at first
represented by the notochord alone; secondly, nascent con-
nective tissue and cartilage are superadded to the notochord ;
thirdly, these acquire their special characters ; fourthly, they
become replaced by bone.

The process of conversion or replacement indicated under
the last head is very incomplete, even in the adult Frog,
in which remains of the notochord are to be found in the
centres of the vertebre; and the cartilage, of which the
greater part of the skeleton at one period of larval ex-
istence was composed, to a great extent persists.

Such cartilage is found forming the free surfaces of the
bodies of the vertebra, the extremities of the caudal style
(urostyle) and the ends of the transverse processes; and
it enters largely into the sternum. In the skull, the para-
sphenoid’, vomers, parieto-frontals, nasals, premaxille, max-
ille, jugals, squamosals, and the bony elements of the man-
dible may be .removed by maceration, leaving behind the
primitive cartilaginous skull, or Chondro-craniwm, altered only
so far as parts of it have been replaced by bone.

It furnishes a floor, side walls and roof to the brain-case,
interrupted only by a large space (called a fontanelle) covered

1 See Laboratory work, D.C, for the structure of the bony skull (osteo-
cranium), which should be thoroughly understood before any attempt is made
to study the cartilaginous skull or chondro-cranium.

XIII] THE FROG. 163

in by membrane, which lies in the inter-orbital region under
the parieto-frontals, and by the foramina for the exit of the
cranial nerves. It consists entirely of cartilage, except where
the exoccipitals, the pro-otics, and the sphenethmoid invade
its substance. In front of the septum of the anterior cavity
of the sphenethmoid, it is continued forward between the two
nasal sacs, as the cartilaginous partition between the nasal
cavities (septum narium), from which are given off, dorsally
and ventrally, transverse ale of cartilage which furnish a
roof and a floor, respectively, to the nasal chambers, Of
these, the floor is the wider. The dorsal and ventral ale
pass into one another where the chondro-cranium ends
anteriorly and give rise to a truncated terminal face, which
is wide from side to side, narrow from above downwards,
and convex in the latter direction. The lateral angles of
this truncated face are produced outwards and forwards
into two flattened pree-nasal processes; these widen externally
and end by free edges which support the adjacent portions
of the premaxille and maxille. From the ventral face,
just behind the truncated anterior end of the chondro-
cranium, spring two slender cartilages, the rhinal processes.
Each of these inclines towards the middle line and ends
against the middle of the posterior face of the ascending pro-
cess of the premaxilla by a vertically elongated extremity.
An oval nodule of cartilage is attached to the posterior face
of the dorsal end of the ascending process of the premaxilla,
and serves to connect it with the rhinal process. On the
dorsal face of the chondro-cranium, just above the point of
attachment of the rhinal processes, the external nasal aper-
tures are situated, and the outer and posterior margins of
each of these apertures are surrounded and supported by a
curious curved process of the cartilaginous ala—the alinasal
process. Where the sphenoidal and the ethmoidal portions
of the sphenethmoid meet, a stout, transverse, partly osseous
11—2

164 ELEMENTARY BIOLOGY. [ XIII.

and partly cartilaginous bar is given off, which is perforated
at its origin by the canal for the orbito-nasal nerve. It then
narrows, but becoming flattened from above downwards,
rapidly widens again, and its. axe-head-like extremity abuts
against the inner face of the maxilla. The anterior angle of
the axe-head is free ; the posterior angle is continued back
into a slender cartilaginous pterygoid rod which bifurcates
posteriorly. The outer division passes into the ventral crus of
the suspensorium. The inner division is the pedicle of the sus-
pensorium; it articulates by a joint with the anterior face of
the broad lateral process of the hinder part of the chondro-
cranium, which contains the auditory labyrinth and is termed
the periotic capsule. The Suspensorium is a rod of cartilage,
which lies between the squamosal and the pterygoid bones
and, at its distal end, articulates with Meckel’s cartilage which
forms the core of the ramus of the mandible. At its dorsal
end it divides into two divergent processes or crura, of which
the ventral crus has already been said to be continuous with
the pterygoid. The dorsal crus, on the other hand, passes up-
wards and, curving backwards, becomes attached to the dorsal
part of the outer face of the periotic capsule.

Meckel’s cartilage, articulated to the free end of the sus-
pensorium, is unossified throughout the greater part of its
extent, no osseous articulare being developed; but, at its
symphysial end, each cartilage becomes ossified, and forms
the mento-Meckelian element of the mandible.

The slender, cartilaginous band (cornu of the hyoid) by
which the body of the hyoid is attached to the skull, is con-
nected with the periotic cartilage immediately in front of
and below the fenestra ovalis.

The pectoral and pelvicarches (see Laboratory work D.e.g.)
are, in the young state, undivided cartilages on each side, and
the development of bone in and upon them does not really
destroy this continuity, the cartilage persisting at the ends of

XIII] THE FROG. 165

the bones and between them, in the glenoidal and acetabular
cavities.

In like manner, the bones of the limbs consist originally
of merely cartilaginous models of the perfect bone; but, as
development proceeds, the middle of the cartilaginous model
commonly becomes invested by a sheath of true bone, while
a calcareous deposit takes place in the cartilage close to its
growing extremities. As the bone grows, the superadded
sheath invades the middle of the cartilage and more or less
replaces it; while the terminal portions of cartilage continue
to grow and enlarge and the calcareous deposit within them
increases, without however reaching their surfaces. Thus
one of the larger adult limb-bones, the femur, consists of
a median shaft of perfect bone, and of two terminal cones of
cartilage, containing calcified epiphyses, inclosed within and
more or less overlapping the hollow ends of the shaft.

The general disposition of the parts which are seen in the
mouth has already been described.

Teeth are found attached only to the premaxille, maxill
and vomers. They are small, with recurved and pointed
crowns. New teeth are constantly being developed in the
gum to replace those which are worn out or broken away.
And as they attain their full size these teeth become anky-
losed to processes of the subjacent bone.

The gullet passes without change of diameter into the
stomach, which lies on the left side of the abdominal cavity
and is nearly as long as it. The stomach narrows posteriorly
and the almost tubular pyloric portion bends round sharply
and passes into the duodenum. A slight constriction marks
the pylorus. The duodenum runs forwards parallel with the
stomach, so that with the latter it forms a sort of loop. At
its anterior end it passes into the rest of the small intestine
(ileum), which is coiled up into a sort of packet and lies

166 ELEMENTARY BIOLOGY. [ xl.

on the right side of the abdominal cavity, being held in its
place by a mesenteric fold of the peritoneum. From the
comparatively narrow neck of the packet, the small intestine
proceeds backwards in the middle line and opens into the
anterior end of the dilated large intestine or colon and rectwm.
The inner wall of the stomach is raised up into a number
of strong longitudinal folds which project into its cavity and
give it a stellate appearance in transverse section. Much
more delicate continuations of these folds are continued into
the small intestine and are there joined by transverse folds.
The opening of the ileum into the colon is valvular, its
edges projecting backwards into the cavity of the colon.
On the dorsal aspect, this presents a slight forward dila-
tation, which may be regarded as a rudiment of a caecum.
The liver is very large, and is divided into two lobes
united by a mere bridge, dorsally and anteriorly. The
left lobe is further subdivided into two. The gall bladder
is attached to the posterior and dorsal face of the right lobe.
The biliary duct opens into the duodenum, at some distance
behind the pylorus, and its termination is embraced by the
base of the slender pancreas.
The rounded spleen lies in the mesentery, projecting
more to the left than to the right side, just above the point
at which the duodenum passes into the ileum.

The apparatus of circulation in the Frog consists of the
blood and lymph vessels and their contents.

The lymph is a colourless fluid containing colourless
nucleated corpuscles which exhibit amceboid movements:
it is contained partly in large spaces immediately beneath
the integument; in the pleuroperitoneal cavity and pro-
bably in the other serous cavities; and, partly, in capillaries
and larger trunks which are interlaced with and accompany
the blood-vessels. The largest of the trunks is the great

XII1.] THE FROG. 167

sub-vertebral lymph-sinus, which lies between the layers of the
root of the mesentery and communicates by small pores with
the pleuroperitoneal cavity. There are four lymph-hearts.

The blood consists of a colourless plasma which contains
colourless corpuscles, similar to those of the lymph, and in
addition a great number of oval nucleated red corpuscles.
It is contained in the blood-vessels, which consist of capilla-
ries, arteries and veins, the two latter being connected on
the one side by the capillaries and, on the other, by the heart
into which they open. The lymphatics and the blood-vessels
are brought into connexion with one another by communica-
tions between the anterior lymph-hearts and the innominate
veins, and between the posterior lymph-hearts and the iliac
veins.

The heart is connected with the walls of the pericardium,
on which spots of pigment may be observed, by the vessels
which enter and leave it and by a slender band which
passes from the dorsal face of the base of the ventricle to the
posterior and dorsal wall of the pericardial chamber.

The heart consists of four readily distinguishable seg-
ments, (1) the sinus venosus, (2) the atriwm, (3) the ventricle,
and (4) the truncus arteriosus, disposed in such a manner
that the sinus venosus, which is the hindermost division, lies
in the middle line on the dorsal aspect of the heart: the
atrium is also median and on the dorsal side, but is in front
of the sinus venosus; the ventricle is median, ventral and
posterior; and the truncus passes obliquely forwards from the
right side of the ventricle and is ventral and anterior. The
heart therefore may be compared to a tube divided by con-
striction into four portions and bent somewhat into the
shape of an S.

The sinus venosus receives on each side, in front, a large
vein, the vena cava superior; while behind the, usually single,
vena cava inferior opens into it, It opens by a valvular

168 ELEMENTARY BIOLOGY. [x11

aperture into the atrium. The latter shews no signs of
division externally, but, internally, it is divided by a delicate
partition, the septum of the auricles, into a smaller left
auricle and a larger right auricle. The sinus venosus opens
into the atrium, to the right of the septum and therefore
into the right auricle. Into the left auricle, the common
pulmonary vein, a small trunk formed by the junction of the
veins from the right and left lungs, opens.

At its posterior end the atrium opens by the auriculo-
ventricular aperture into the ventricle.

A small valve, prevented from flapping back by fine ten-
dinous cords, exists on each side of this aperture, and the
septum of the auricles is continued back upon the faces of
these valves and ends by a free edge between them, thus
dividing the auriculo-ventricular aperture itself into two
openings.

The walls of the sinus and of the atrium are very thin.
Those of the ventricle, on the other hand, are thick and
spongy, only a comparatively small, transversely elongated,
clear cavity being left at the anterior end or base of the
ventricle. At the right extremity of this is the aperture
which leads into the truncus arteriosus. Three semilunar
valves, which open from the ventricle into the truncus, sur-
round this opening.’

The walls of the truncus arteriosus are thick and mus-
cular, though not nearly so thick as those of the ventricle.
At its anterior end it appears to divide into two trunks,
which diverge and immediately leave the pericardium to
pass on to the sides of the gullet. The elongated undivided
part is the pylangium, the terminal part common to the
divergent trunks is the synangiwm. The former is divided
throughout its length by a sort of fold which is attached to
the dorsal wall while its opposite edge is free. Three semi-
lunar valves separate the pylangium from the synangium, in

XII] THE FROG. 169

which are the openings, posteriorly, of the pulmonary ar-
teries, anteriorly of the carotid trunks; while, at the sides,
the cavity of the synangium opens into those of the right and
left aortic arches. The apparently simple branches into
which the truncus arteriosus divides, are, in fact, each made
up of three separate trunks, the pulmo-cutaneous trunk behind,
the aortic arch in the middle and the carotid trunk in front.

When the heart is in action, the sinus venosus, the
atrium, the ventricle and the truncus arteriosus contract in
the order in which they have just been named. Each
contracts as a whole, so that the two auricles are emptied
simultaneously. The blood from each is forced into the
corresponding half of the spongy cavity of the ventricle so
that the right half of the ventricle contains venous blood
_ and the left arterial blood. When the systole of the ventricle
takes place, the blood which is first driven into the truncus
arteriosus (the opening of which is, as has been seen, at the
right end of the cavity) is therefore venous. It fills the
conus arteriosus and, finding least resistance in the short
and wide pulmonary vessels, passes along the left side of the
median valve into them. But as they become distended
and less resistance is offered elsewhere, the next portion of
blood, consisting of the venous and arterial blood which have
mixed in the middle of the ventricle, passes on the right
side of the longitudinal valve into the aortic arches. And,
as the truncus becomes more and more distended, the longi-
tudinal valve, flapping over, tends more and more completely
to shut off the openings of the pulmonary arteries and to
prevent any blood from flowing into them.

Finally, the last portion of blood from the ventricle,
representing the completely arterialized blood of the left
auricle which is the last to arrive at the opening of the
truncus, passes into the carotid trunks and is distributed to

the head.

170

ELEMENTARY BIOLOGY. [ XIII.

The principal vessels of the Frog are disposed as fol-
lows :—

A. Arteries.

1,

The system of the anterior aortic arch (carotid
trunk).

a. Lingual artery—to the tongue.

b. Carotid artery—to the interior of the skull and
the brain.

The system of the middle aortic arch (aortic trunks).

a. Vertebral and subclavian—to the vertebral co-
lumn, and to the fore-limb. Msophageal to the
gullet.

b. Cceliaco-mesenteric (given off from the left arch,
or from the dorsal aorta, at, or beyond, the junc-
-tion of the two arches).

a. Coeliac to stomach and liver.
8. Mesenteric to intestine and spleen.

c. Branches of the dorsal aorta to the adrenal and
renal organs, to the genital organs and to the
muscles of the back.

d. The terminal branches of the dorsal aorta (com-
mon tac); each of these gives off hypogastric
arteries to the bladder and walls of the abdomen

and is continued as the femoral artery into the
leg.

The system of the posterior aortic arch (pulmo-
cutaneous trunk).
a, Pulmonary artery to the lungs.

b. Cutaneous artery to the dorsal integument.

XII]

B. Veins.

THE FROG. 171

1, The system of the swperior cava formed on each
side by the union of the vena innominata, the sud-
clavian and the eaternal jugular.

a.

Internal jugular vein: leaves the skull by the
jugular foramen, and brings back blood from
the brain, spinal cord and anterior vertebral
region.

Subscapular: returns the blood from the brachium
and shoulder. These two veins (a and 6) unite to
form the vena tnnominata.

The musculo-cutaneous vein, receiving the blood of
the surface of the head (except the mandibular
and hyoidean regions) and that of the back of
the trunk—passes forwards between the internal
and external oblique muscles of the abdomen.

The brachial vein receives blood from the ante-
brachium and manus.

These (c and d) unite to form the subclavian vein.

The veins of the mandibular region and those
of the tongue unite into the eaternal jugular
vein. ;

2. The system of the inferior cava, formed by the union
of the renal, genital and hepatic veins.

a.

The femoral vein from the front of the leg,
and—

The scvatic vein from the back of the leg, pour
their blood into a trunk which lies in the lateral
wall of the pelvis and may be termed the pelvic
vein ; the dorsal end of this becomes—

Or

ELEMENTARY BIOLOGY. [ XUI.

c. The common iliac vein, which passes to the outer
edge of the kidney and is distributed to that
organ, whence the blood is carried to the vena
cava inferior by the renal veins.

d. The dorso-lumbar vein, which lies along the
transverse processes of the vertebra and receives
blood from the walls of the abdomen and from
the interior of the spinal canal, opens into the
common iliac. ;

. The system of the anterior abdominal vein, formed by

the union of the ventral ends of the pelvic veins (2. b).
It receives blood from the urinary bladder and the
walls of the abdominal cavity, and at its anterior
end divides into two branches—a right and a left.
These branches go to the corresponding lobes of the
liver, the left receiving a large communicating branch
from the gastric division of the vena porte.

The system of the vena porte formed by the union of
two veins; one, gastric, which brings back the blood
from the stomach, the other, Keno-intestinal, which
returns that from the spleen and intestines.

[Hence the right lobe of the liver and part of the left
lobe are supplied with systemic venous blood, more or less
mixed with gastric venous blood, while only part of the
left lobe is supplied with intestinal venous blood. Besides
this venous blood, it must be recollected that the liver
receives arterial blood by the hepatic artery. |

The system of the pulmonary vein, formed by the
union of the veins of the right and left lungs.

In addition to the apparatus of the circulation of the
blood, the Frog possesses two pairs of lymph-hearts. These

XI1.] THE FROG. 173

are contractile muscular sacs, which are connected on the one
hand with the lymphatic vessels and on the other with large
veins in their neighbourhood; and which pump the lymph
contained in the wide lymphatic vessels and in the pleuro-
peritoneal cavity of the Frog, into these veins.

The anterior lymph-hearts are situated close to the trans-
verse processes of the third vertebra, below the edge of the
scapula; the posterior pair lie one on each side of the uro-
style, and their pulsations may be observed by carefully watch-
ing the integument in this region in a living Frog.

The Zhymus gland is a small rounded body situated
immediately behind the suspensorium, in a position corre-
sponding to the dorsal ends of the obliterated branchial
arches.

The Thyroid gland appears to be represented by two or
more oval bodies, which are found attached to the lingual
vessels and between the aortic and pulmo-cutaneous trunks.

The Adrenal glands are yellow bodies imbedded in the
ventral face of the kidney.

The slit-like glottis of the Frog is formed by the apposi-
tion of two longitudinal folds of the mucous membrane of the
mouth, each of which contains a cartilage of similar form.
These cartilages are the arytenoid cartilages. They are
articulated with an annular cartilage (laryngo-tracheal) which
supports the wall of the very short chamber which represents
the larynx and trachea. When the two folds of the glottis
are divaricated, there are seen between them two mem-
branous pouches, the free edges of which meet in the middle
line, while anteriorly and posteriorly they pass into the
mucous membrane which lines the faces of the longitudinal
folds. These are the vocal ligaments, and the slit between

174 ELEMENTARY BIOLOGY. [ XIII.

them is what answers to the glottis in Man. It is by their
vibration that the croak of the Frog is produced.

Laterally the laryngo-tracheal chamber opens into the
lung of each side. The lung is a transparent oval sac, some-
what pointed posteriorly, which lies at the side of the
cesophagus in the dorsal region of the abdominal cavity.
It is covered by a layer of the pleuroperitoneal membrane
which represents the visceral layer of the pleura in the
higher animals. The wall of the pulmonary sac is produced
inwards so as to give rise to septa, which are much more
prominent and more numerous in the anterior than in the
posterior part of the lung and divide the periphery of the
cavity into numerous air-cells, on the walls of which the
ramifications of the pulmonary artery are distributed.

The lungs are elastic, the distended lung collapsing sud-
denly when it is pricked, and they contain abundant muscu-
lar fibres.

Inspiration is effected in the Frog by a buccal force-pump.
The mouth being shut and the external nostrils open, the
floor of the mouth is depressed, and the buccal cavity fills
with air. The nostrils being then shut, the hyoid, and with
it the floor of the mouth, is raised, the aperture of the gullet
being at the same time closed. Thus the air is forced
through the glottis and distends the lungs.

In ordinary expiration, the elasticity of the lungs and the
pressure of the surrounding viscera probably suftice to expel
the air; but this operation may be powerfully aided, firstly
by the contraction of the intrinsic muscular fibres of the
lungs; secondly, by the contraction of the muscles of the
lateral and ventral regions of the abdominal wall; and thirdly,
by the contraction of those muscular fibres which enter into
the diaphragm; as all these actions tend, either directly or
indirectly, to diminish the capacity of the lungs.

It is essential to inspiration that the mouth should be

Xu] THE FROG. 175

shut, and it is said that frogs may be asphyxiated by keeping
their mouths open.

In addition to its principal pulmonary apparatus of re-
spiration, the Frog has a secondary respiratory apparatus in
its moist and delicate skin. A considerable amount of venous
blood is, in fact, constantly supplied to this organ by the large
cutaneous branch of the pulmo-cutaneous artery. It has been
experimentally ascertained that frogs in which the lungs
have been extirpated will continue to live and respire for a
considerable time, especially at a low temperature, by means
of the skin.

The kidneys are elongated and flattened from side to side,
and are kept in their places by the continuation of the peri-
toneum over their ventral faces. The ducts of the kidneys
pass from about the junction of the middle and posterior thirds
of the outer edge of each kidney and, approaching as they pass
backwards, open by two small closely approximated slit-like
apertures in the posterior wall of the cloaca.

The urinary bladder is a large bilobed sac, opening poste-
riorly, by a wide median aperture, into the anterior end of the
cloaca, on the ventral side of the rectum.

The testes are spheroidal yellowish bodies situated in
front of the kidneys and enveloped in peritoneum, a fold of
which, forming a sort of testicular mesentery or mesorchium,
passes into that which covers the ventral face of the kidney.
The delicate vasa efferentia of the testes may be seen travers-
ing this fold to enter the substance of the kidney. They
communicate with the urinary tubules, and thus the duct of
the kidney serves not only as the duct of the urinary excretion
but as the vas deferens.

The spermatozoa of Rana esculenta have thick and cylin-
drical heads, while those of Rana temporaria are linear.

The ovaria are broad lamellar organs, very large and

176 ELEMENTARY BIOLOGY. [ XIII.

much folded and plaited in the breeding season. The in-
terior of each is hollow, and is divided into several chambers.
‘Innumerable ovisacs, containing dark-coloured ova, are scat-
tered through the substance of the ovary and give rise to
projections upon the inner surface of the ovarian chamber |
as they become fully developed. .

The oviducts are long convoluted tubes situated on each
side of the dorsal wall of the abdominal cavity to which they
are connected by peritoneal folds ; each curves over the outer
face of the root of the lung. Their anterior ends are very
slender, and terminate by open mouths at the sides of the
pericardium, between the attachment of the diaphragm and
the lobe of the liver. The fold of peritoneum which serves
as a ligament, holding the lobe of the liver to the dia-
phragm, cesophagus and posterior wall of the pericardium,
in fact constitutes the outer lip of the oviducal aperture.
For the greater part of their length their walls are thick and
glandular, and swell up when placed in water. Posteriorly,
the oviduets dilate into capacious thin-walled chambers and
end, close together, by openings which are situated in the
dorsal wall of the cloaca immediately in front of the aper-
tures of the ureters.

Each ovum, when ripe, consists of a structureless vitelline
membrane, inclosing a vitellus, within which is a germinal
vesicle, containing several ‘germinal spots.’ One half of the
vitellus is deeply coloured, the other pale.

The actions of the different parts of the organism of the
Frog are coordinated with one another and brought into
relation with the external world by means of the muscular
and nervous systems and the organs of sense.

The muscles consist partly of striped and partly of un-
striped fibres, the former being confined to the muscles of
the head, trunk and limbs and the heart, while the latter

XIII] THE FROG. Vi

are found in the viscera and vessels. An account of the di
position of the muscles in the hind-limb will be found in #]
Laboratory work.

The nervous system is conveniently divisible into ty
parts, the cerebro-spinal and the sympathetic. The cerebr
spinal nervous system again consists of the brain, or encephi
lon, with its nerves, and the spinal cord, or myelon, with i
nerves.

The encephalon lies in the cranial cavity, which it near
fills, and is divisible into the hind-brain, the mid-brain ax
the fore-brain, which last again comprises three division;
the thalamencephalon, the cerebral hemispheres, and tl
olfactory lobes.

The greater part of the hind-brain is formed by tl
medulla oblongata, which is the continuation of the myel
forwards and presents, on its dorsal aspect, a triangular cavit
the apex of which is directed backwards. It is roofed ov
by a thick and very vascular membrane (choroid plexus), #1
inner surface of which presents transverse folds on either sic
of a median longitudinal ridge. The cavity is the four
ventricle ; it communicates behind with the central canal
the myelon, while, in front, it narrows into a passage whic
connects the fourth ventricle with the cavities anterior to :
The thick lateral ridges of nervous substance at the sid
of the fourth ventricle, which represent the restiform bod
pass, in front, into the outer extremities of a short bro
tongue-shaped plate, convex ventrally and concave dorsall
which overhangs the anterior part of the fourth ventricl
and is the cerebellum.

In front of this, the dorsal moiety of the mid-brain
formed by two oval bodies, the long axes of which a
directed inwards and backwards. These are the optic lobe
When laid open, each is seen to contain a cavity or ventric
with an opening on its inner face. These openings lead in

M. 12

178 ELEMENTARY BIOLOGY. [SxrIr::

a short passage, which communicates with the iter a tertio ad-
quartum ventriculum, as the canal which leads, through the
mesencephalon, from the fourth to the third ventricle is
termed. The floor of this canal is formed by the thick prin-
cipal mass of the cerebro-spinal axis. It exhibits a median
longitudinal depression or raphe, and in this region represents
the crura cerebri.

In front of the mid-brain comes the hinder division of the
fore-brain, or thalamencephalon, which is very distinct in the
Frog and contains a median cavity, the third ventricle. On
each side, the cavity of the third ventricle is bounded by a
thick mass of nervous matter into which the crura cerebri
pass. These are the optic thalami. Dorsally, the walls of
the third ventricle are very thin and easily torn through,
except behind, where there is a thick transverse band of
nervous substance, the posterior commissure.

From the fore part of the roof of the third ventricle, a
delicate process proceeds to the pineal gland—an ovate body
lodged between the posterior parts of the cerebral hemispheres.
The front part of the floor of the ventricle, on the other hand,
is produced into a bilobed process directed backwards, which
is the infundibulum, This is connected below with the pitwi-
tary body. In front of this is seen the commissure of the
optic nerves.

Anteriorly, the third ventricle is bounded by the thick
lamina terminalis which contains the anterior commissure.
On each side, between this and the peduncle of the pineal
gland, is a small aperture, the foramen of Munro, which leads
into a cavity in the interior of the cerebral hemisphere—the
lateral ventricle.

The hemispheres are elongated bodies, broader behind
than in front, where they are marked off only by a slight
constriction from the olfactory lobes. The outer wall of the
ventricle, though relatively thick, presents nothing which can

XII] THE FROG. 17

be called a distinct corpus striatum. The inner wall forr
one or two convex projections into the ventricle.

In the bases of the olfactory lobes the forward continu<
tion of the ventricular cavity is very narrow and the lobe
become nerve-like, cords, which leave the skull and sprea
out on the posterior faces of the olfactory sacs.

The inner faces of the hemispheres are quite free an
separated by a cleft, the great fissure, but the inner facc
of the commencements of the olfactory lobes are closel
united together, giving rise to a kind of corpus callosum.

There are ten pairs of cranial nerves ordinarily so calle
though it is to be recollected that the first and second pai
are proved, by their development, to be lobes of the brain,

1. Olfactoria.

The olfactory lobes are what answer to the so-calle
olfactory nerves of the higher Vertebrata. They a
distributed exclusively to the olfactory sacs.

2. Optict.
These diverge from the base of the brain in front
the infundibulum. They are originally outgrowths

the thalamencephalon which secondarily become co
nected with the optic lobes.

Of the remaining cranial nerves five pairs leave the ski
in front of the auditory capsules, while one pair enters thc
capsules and two pairs pass out behind the capsules,

The preauditory nerves are the following.

3. Motores oculorum
arise from the front part of the floor of the mid-brz
and are distributed to all the muscles of the e
except the external rectus, the superior oblique a

the retractor bulbi.
12—

180

ELEMENTARY BIOLOGY. [XIIt.

4. Pathetici

arise from the floor of the mid-brain and pass out, on
the dorsal aspect of the brain, between the cerebellum
and the optic lobes. They are distributed to the
supericr oblique muscles of the eye.

Trigemint

take their origin in the front part of the floor of the
hind-brain and, passing out at its sides, each dilates
into a yellow enlargement—the Gasserian ganglion—
which lies, in front of the auditory capsule, in the

foramen of the pro-otic bone by which the nerve, after
leaving the ganglion, passes out of the skull.

This ganglion is connected with the trunk of the sixth
and seventh nerves and with the anterior end of the
sympathetic, and some of the branches which appear to be
given off from it really belong to the sixth and the seventh

nerves.

Beyond the ganglion, the nerve divides into three

main branches, the orbito-nasal, the palatine and the masillo-
mandibular.

The orbito-nasal (usually termed the first division of
the fifth nerve) is distributed :

a. To the external rectus.

b. To the retractor of the bulb,

(These branches (a and 6) belong to the sixth nerve.)

c. <A branch which anastomoses with the fourth
nerve.

d. A branch to the Harderian gland.

e. The principal trunk of the nerve passes through
the ant-orbital process of the skull into the nasal

XIU]

i.

ill.

THE FROG. 181

chamber and is finally distributed to the nasal
mucous membrane and to the integunient of the
nose,

The palatine is distributed :
a. To the roof of the oral cavity.

b. Its main trunk runs forward between the mucous
membrane of the roof of the mouth and the skull,
pierces the vomer and ends in the mucous mem-
brane of the anterior part of the palate.

(This nerve is chiefly, if not wholly, derived from the
seventh nerve.)

The mazillo-mandibula? divides into two trunks,
usually termed the second and third divisions of the
fifth nerve.

a. Mazillary, passes outside the eye and is distri-
buted to the integument of the upper jaw; an
anastomotic branch unités this nerve with the
palatine.

b. Mandibular, passes between the temporal and
pterygoid muscles, below the jugal, over the
articulation of the mandible and along the inner
face of the latter, to the symphysis, giving off
branches to the integument, muscles, teeth and
tongue.

Abducentes

arise from the floor of the hind-brain and leave the
ventral surface of the medulla oblongata close to the
middle line. Each then unites so closely with the
Gasserian ganglion and with the orbito-nasal division
of the fifth as to appear to be only a subdivision of
the latter (see 5. i. a and b).

182

ELEMENTARY BIOLOGY. [ XIII.

7. The Faciales

take their origin from the floor of the hind-brain,
behind the fifth and in common with the eighth; and,
leaving the hind-brain, enter into close connexion with
the Gasserian ganglion. Each then divides into two
branches, an anterior and a posterior. The anterior
passes into the palatine division of the fifth; the
posterior passes between the dorsal and ventral crura
of the suspensorium, enters the tympanic cavity,
runs over the columella auris and then, as it leaves
the tympanum, receives a very large branch from the
glossopharyngeal, Finally it divides into two branches,.
anterior and posterior.

a. The former, which answers to the chorda tympani
of the higher Vertebrata, runs along the inner
face of the ramus of the mandible parallel with
the mandibular branch of the fifth.

b. The posterior passes alongside the cornu of the

hyoid and supplies its muscles.

The Auditori

arise In common with the foregoing. Each divides
into two branches which enter the auditory capsule.

The Post-auditory nerves are:

9, The Glossopharynget.

These nerves arise, in common with the next, from
the medulla oblongata; and the roots of both leave
the skull by an aperture behind the auditory capsule
on each side, and form a common ganglion. From
this the trunk of the glossopharyngeal is given off.
It passes downwards and forwards to the root of the

X111.] THE FROG. 1

tongue, which it enters and then supplies that orge
Moreover, it gives off muscular branches and a lar
anastomotic branch to the seventh.

10. The Pneumogastrict or Vagi.

Immediately after leaving the ganglia these nerv
separate from the glossopharyngeal and each gives «
a cutaneous branch to the dorsal integument of t.
head and trunk: it then divides into two branch:
one of which (a) runs on the inner side of and above t:
cutaneous branch of the pulmo-cutaneous artery, tl
other (0d) lies below and diverges from the first.

a. is the laryngeal nerve. It passes beneath the fir
cervical nerve, then crosses over the third aort
arch and, about its middle, turns sharply round
‘to. be distributed to the larynx. This ner
corresponds with the recurrent laryngeal of tl
higher animals.

b. is the splanchnic branch. It gives off (gastri
branches to the gullet and stomach, and a fi
nerve (cardiac) which passes beneath the pr
monary artery and along the root of the lung
the heart, and ends in ganglia situated in tl
septum of the auricles. The splanchnic bran
finally enlarges and is distributed to the lun;
and stomach.

The myelon or spinal cord is continued back from tl]
hind-brain as a subcylindrical cord, which lessens somewh
rapidly towards its apparent end at the level of the seven’
vertebra. It does not really end here, however, but is co:
tinued back as a slender filament, the filum terminale, to t]
commencement of the canal of the urostyle. The diamet
of the cord ig somewhat enlarged opposite the origin of tl

184, ELEMENTARY BIOLOGY. [ XIII.

nerves for the limbs. In transverse sections, the cord is seen
to be not truly cylindrical and to be indented by two
longitudinal grooves, one dorsal and one ventral, which leave
but a small connecting bridge between its two halves. In
the centre of this is a canal, the canalis centralis, the cavity
of which is continued forwards into the fourth ventricle.

Ten symmetrically disposed pairs of nerves come off from
the sides of the cord, each nerve having two roots, one from
the dorsal surface of the lateral half of the cord and one
from the ventral half. The dorsal root presents a small
ganglionic enlargement, beyond which it joins the ventral root
t2 forra the common trunk of the spinal nerve. The roots of
the hinder spinal nerves are very long and lie, side by side,
for some distance, in the spinal canal.

The first spinal nerve leaves the neural canal by the
interspace between the arches of the first and second
vertebra, so that there is no suboccipital nerve in the Frog.
It gives a branch to the muscles which move the head upon
the atlas, but the main trunk of it descends behind the
mandible, along with the glossopharyngeal nerve, and is
distributed to the muscles of the tongue. It therefore
answers to the hypoglossal nerve in the higher Vertebrata.

The second and third spinal nerves, of which the second
is the larger, unite to form a ‘brachial plexus, and are dis-
tributed chiefly to the fore-limb.

The fourth, fifth and sixth spinal nerves go to the middle
parietes of the body.

The seventh, eighth and ninth, are large nerves which
unite to form the lumbosacral pleaus, whence nerves are
given off to the posterior parietes of the body, and to the
hind-limb. The nerves of the latter are the crural to the
front part of the thigh, and the sciatic, which passes to the
back of the thigh and ultimately divides into the peroneal
and tibial nerves which supply the leg and foot.

XIII] THE FROG. 1

The tenth spinal nerve leaves the neural canal by t
coccygeal foramen, and is distributed to the adjacent parts

Sympathetic.

The sympathetic system consists of ten ganglia, connect
by longitudinal commissures, and situated on each side
the ventral face of the vertebral column; in the region
the dorsal aorta they come into close relation with it. Ea
sympathetic ganglion is joined by a communicating fi
ment with one of the spinal nerves, and the most anter
ganglia are united, in the same way, with the ganglion of t
ninth and tenth cerebral nerves. From this a delicate co
which must be regarded as the most anterior part of t
sympathetic, passes into the cranial cavity, on the inr
side of the periotic capsule, and unites with the Gasseri
ganglion.

The branches of the sympathetic accompany the vesse
and large branches are given to the viscera of t
abdomen.

The Olfactory organs are two wide sacs which occupy
the space between the mesethmoid cartilage, the antorbi
processes, and the premaxillz and maxille, and open in fro
and dorsally by the external nares, behind and ventra
by the posterior nares. The inner faces of these sacs 2
lined by a very peculiar epithelium, and the olfactory nerv
with some branches of the trigeminal, are distributed

them.

The Eyeball is lodged in the orbit and protected by t
eyelids described above. It has four recti muscles whi
proceed from the inner wall of the orbit, and are attach
to the circumference of the globe; within these is a retract

186 ELEMENTARY BIOLOGY. [ XII.

muscle with similar attachments, ensheathing the optic
nerve, while two oblique muscles proceed from the anterior
and inner wall of the orbit and are attached to the dorsal
and ventral faces of the bulb. In addition, a fine tendon
passes from the outer end of the lower eyelid, or nictitating
membrane, and is attached to the fibres of the retractor
bulbi—the effect of which is that when the bulb is retracted
the nictitating membrane is raised over the eye. The upper
lid has no muscles. A secretory organ, termed the Harderian
gland, is situated in the anterior part of the orbit beneath
the superior oblique muscle.

The sclerotic is cartilaginous but contains no ossifications,
and the lens is nearly spherical. There is no pecten.

The Zar consists of an essential part—the membranous
labyrinth—lodged in the periotic capsule, and accessory parts,
the columella auris, the tympanic membrane and the tym-
panum.

The former consists of the three ordinary semicircular
canals, with their vestibular dilatations, which open into a
vestibule divided into wtriculus and sacculus. The latter,
especially, contains a great quantity of white crystalline
calcareous otoliths.

On the outer side of the vestibule is a small dilatation
which is possibly a rudimentary cochlea.

The membranous labyrinth is contained in the partly
cartilaginous, partly osseous, periotic capsule into which it
fits but loosely; the interval is filled with a fluid, the perz-
lymph. In the outer face of the periotic capsule is an oval
opening, the fenestra ovalis, into which the end of the
columella auris fits. This columella is shaped like a pestle,
the end of the handle of which is fitted with’ a cross-piece.
The rounded inner end of the pestle, which is fixed by fibrous
tissue into the fenestra ovalis, is cartilaginous. The middle

XU] . THE FROG. li

of the handle is ensheathed in bone, while the outer part
cartilaginous. The cross-piece is fixed into the inner face
the membrana tympani, which is lined externally by t!
integument, internally by mucous membrane, continuo
with that of the mouth through the Eustachian recess. T'
mucous membrane of the tympanic cavity covers only t.
ventral face of the columella, over the dorsal face of whi
the posterior division of the facial nerve passes.

The Tongue. This organ, as has been seen, is fixed on
in front to the mandible, and by the anterior half of its ve
tral aspect to the floor of the mouth; the posterior half bei
free and bifid at the extremity. Narrow-ended and broa
ended papillae (papille filiformes and fungiformes) are sca
tered over the whole dorsal aspect of the tongue and a
largest in front; small glands lie between these papille.

The fungiform papille contain the ultimate ramificatio:
of the glossopharyngeal nerve, and the epithelium coverir
their summits is peculiarly modified.

The Integument.

No special organs of touch have been observed, but tl
integument is remarkable for the immense number of clos:
set simple glandular c#ca which open upon its surface. |
the swollen integument which covers the base of the inn
digit in the males, large papille with interposed glands ai
developed.

A singular body of unknown function, the browspot «
inter-ocular gland, consisting of a spheroidal sac with minut
cells, occurs in the integument of the frontal region of th
head.

Cells containing pigment abound in the integument an
undergo remarkable changes of form, the pigment bein
sometimes drawn together into a spheroidal mass—at othe
times distributed in a radiating fashion.

188 ELEMENTARY BIOLOGY. [X10

LABORATORY WORK.
A. GENERAL STRUCTURE,
1. Go over the specific characters given above (p. 157).

2. The divisions of the body: head, trunk, two pairs
of limbs (see p. 152).

a. The head.

Somewhat triangular, with the blunted apex
turned forwards and passing broadly, without any
neck-constriction, into the trunk; notice the pro-
minent eyes with their lids; the membrana
tympam, a part of the integument stretched
over a hard ring, placed on each side, behind and
somewhat below the eyes; the two apertures of
the nostrils (anterior nares) between the eyes and
the end of the snout; the mouth-opening; the
hard parts felt through the skin on the upper
side of the head; the'soft flexible throat.

Pass a bristle into one of the anterior nares.
Make a small opening in one of the tympanic
membranes and pass another bristle into it. Now
open the mouth widely; and, if the bristles have
been thrust far enough, the end of the former
will be seen traversing the posterior nasal open-
ing in the roof of the mouth: while the end of
the other will appear in the Eustachian recess
which lies at the sides of the back of the oral
cavity. The fleshy tongue will be seen, with its
bifurcated free end turned backwards. Turn it
forwards to see the attachment of its base to the

XII]

THE FROG. 18£

floor of the mouth and to the front part of the lowe:
jaw. Notice the slit of the glottis in the hinde
part of the floor of the month, and above this th«
opening of the cesophagus. Pass a bristle into th:
former, and a probe into the latter. Notice th:
fine teeth in the upper jaw and on the palate.

b. The trunk.

Tapering towards the hinder end; and allowin;
the hard parts of the skeleton to be felt beneat]
the soft integument on the dorsal side, and in th:
anterior half of the ventral aspect; rounded ani
soft on the greater part of the sides and belly
the cloacal aperture near the dorsal surface of th
posterior end of the trunk.

c- The limbs.

a. The anterior pair; their three subdivisions
brachium, antebrachium, and manus; the fou
digits.

8. The posterior pair; their length as compare
with that of the anterior ; their subdivision int
femur, crus, and pes: the five long digits
the well-developed wed; the horny prominenc
(see p. 154).

Raise the integument of the abdomen with forcer
and slit it open with scissors from the lower jaw t
the origin of the hind limbs, a little on one side ¢
the middle line. Observe the spacious lymph cavitie
between the skin and the subjacent muscular wall ¢
the abdomen; also a vein which occupies the midd]
line of the inner face of this wall and is usuall
visible through it.

190

ELEMENTARY BIOLOGY. [XIII

Raise the muscular wall of the abdomen and cut it in
the same way, slightly on one side of the middle line,
sufficiently to lay open the abdominal cavity, taking
great care to avoid the bladder which lies at the
posterior end of the cavity. Note the conspicuous
vein (anterior abdominal) which lies beneath the
muscles in the middle line of the belly. The liver,
stomach and intestines will be seen; at the sides, in
the female, the ovaries and oviducts will be very con-
spicuous in the breeding season. Insert a small blow-
pipe into the cloacal opening: air blown in will
distend the large bilobed urinary bladder. If the
lungs are distended with air, one will be visible on
each side of the anterior end of the abdominal cavity,
and the extremity of the bristle passed into one of
them, through the glottis, will be seen. Lay open
the stomach to see the end of the probe meee into
the cesophagus.

By turning the intestines on one side, the kidney, the
corpus adiposum and the testis (in the male) will be
exposed. Notice a number of small white patches on
each side of the vertebral column. They are accumu-
lations of calcareous crystals.

In front of the liver, the apex of the heart will be seen
through the pericardium. Lay the latter open and
observe the position of the heart.

Cut away the left fore-limb and the left hind-limb,
with so much of the left half of the vertebral column
and skull as is needful to lay open the cavity which
contains the cerebro-spinal nervous centres. Pin the
frog in a dissecting dish on its right side, with suf-
ficient water to cover it, and ‘study the position of the

x11]

THE FROG, 19

various organs in relation to a median longitudine
plane, making a careful diagram of the parts dis
played,

In a frog which. has lain in bone-softening solution (sa
1 per cent. chromic acid) sufficiently long to soften tk
bones, make transverse sections (1) through the eye
(2) through the centres of the tympanic membrane
(3) through the shoulder-girdle, (4) through the hind
half of the abdomen. Compare them with the for
going dissection,

B. DISSECTION OF THE VISCERA IN THE VENTRAL CAVITY.

1.

Lay a frog, which has been killed with chloroform, c
its back and pin it out on a layer of paraffin «
beeswax, under water; divide the skin along the a
dominal median line from the pelvis to the front of tI
lower jaw; next make a transverse incision at eac
end of the longitudinal one, and then throw outwar
the two flaps of skin thus marked out. The followir
points may now be noted.

a, Agreat vein (musculo-cutaneous) on the under su
face of each flap of skin, about the level of tl
shoulder.

b. Some of the muscles of the abdominal wa
covered by’ a thin aponevrosis: through tk
latter can be seen—

g The rectus abdominis running from pelvis
sternum close to the middle line, and divid
into a number of bellies by transverse tenc
nous intersections.

@. Other muscles outside the rectus on each sid

192

ELEMENTARY BIOLOGY. [XIII .

¢. The pectoral region; part of its hard parts in the
middle line, only covered by tendinous tissue:
external to this, muscles running towards the
shoulder-joint.

d. The muscles of the throat; small and with a
general direction from the lower jaw towards the
sternum and shoulder-girdle.

Raise the tissues of the body-wall with a pair of
forceps and carefully divide them, a little to the right.
of the median line, so as to open the body-cavity
without injuring its contents; prolong the incision
from the pelvis to the posterior end of the breast-
bone; make a transverse incision close to the pelvis
and throw back the flap on each side: on the deep
side of the left flap will be seen a large vein (anterior
abdonunal).

Seize the posterior border of the sternum with
a pair of forceps and raise it up: on looking beneath
it several fibrous bands will be seen running from it
and the hard parts in front of it to subjacent parts ;
carefully divide these: then, with a strong pair of
scissors, cut through the hard parts in the median
line, being very careful not to injure the organs
beneath them ; turn each half outwards and pin it in
that position; stretch out each fore-limb to its fullest
extent and fasten it with pins.

Note the smooth moist membrane ( pleuroperitonewm)
lining the inside of the body-cavity and covering the
outside of the contained viscera,

The liver will be readily recognized as a great
brownish mass covering a great part of the other
abdominal viscera: lying in a cleft in its anterior border

.

XIIL]

5

THE FROG. 193

and partly concealed by it, will be seen a delicate
sac in which pulsations are going on; this sac is the
pericardium: if it be opened and removed very care-
fully, the heart and some of the great blood-vessels
will be laid bare ; clean carefully the two great trunks
{aortic arches) which diverge from the anterior end
of the heart, following each to the point of its division
into three vessels.

The heart.

a.

Note the general form of the organ.

Its posterior conical thick-walled portion (ven-
tricle) with the apex turned backwards.

The truncus arteriosus: a sub-cylindrical part,
arising from the right side of the base of the
ventricle and dividing anteriorly into the two aortic
arches.

The atrium: thin-walled, rounded, lies on the
dorsal aspect of the truncus and ventricle. The
separation between the two auricles is not visible
externally.

Carefully raise the ventricle: lying beneath it
(that is, on its dorsal side) will be seen another
division of the heart, the sinus venosus; it lies
between the atrium and the great systemic veins,
which enter it through the dorsal and posterior
walls of the pericardium.

The further examination of the structure of the
Frog’s heart requires a good deal of care and
the use of a lens of low magnifying power. Ina
Bead 138

194

i.

a.

ELEMENTARY BIOLOGY. [xXi.

chloroformed Frog the heart is distended with
blood when it ceases to beat. When all signs
of contractility have disappeared, the distended
heart should be removed from the body by cutting
through the adjacent parts in such a manner as
to leave the terminations of the veins and the
origins of the aortic trunks intact. The organ
should next be transferred to a shallow dissecting
dish and covered with weak spirit. The right and
left walls of the atrium being now carefully slit
and the blood which they contain washed away,
the delicate septum of the auricles will become
visible. By cautiously removing the ventral face
of the ventricle, its cavity will be laid open and
the auriculo-ventricular opening will be displayed.
If the ventral wall of truncus arteriosus is laid
open longitudinally with fine scissors, the valves
in its interior will become visible. The pul-
monary vein runs along the dorsal aspect of the
sinus venosus, between the right and left superior
vene cave, to the left auricle, into which it opens
close to the dorsal attachment of the septum.

The natural relations of the different divisions
of the heart should be carefully studied in such
a dissection as is described in A. 6,

The pulsation of the heart. This should be studied

in a Frog rendered insensible by chloroform or by
being pithed; though the latter operation causes such
dilatation of the vessels that little or no blood may
afterwards flow through the heart, yet the organ goes
on beating.

Watch the movement carefully; it is a regularly
alternating series of contractions and dilatations.

XIU.]

THE FROG. 19

It will be seen that the two auricles contrac
together; immediately after them, the ventricle
and then, instantly, the bulbus arteriosus.

Raise the ventricle so as to see the venous sinus
note that it contracts immediately before th
auricles,

6. The parts exposed by the preceding dissection

(B. 1. 2).

“Draw them carefully without disturbing them.

a.

a

The throat-muscles: through the broad thin mus
cle in front (mylo-hyoid) is seen the hypoglossc
nerve.

The larynx: forming a hard prominence in th
middle line, just in front of the aortic arches.

The heart and aortic arches (see B. 5. i): th
three terminal branches of the latter, viz —

The carotid trunk; the anterior division; end
ing in a small reddish body (the carotid gland).

8B. The systemic aortic arch.
y. The pulmo-cutaneous artery: the hindmos

branch.

The liver: a great brown two-lobed mass; it
left lobe the larger and subdivided into two.

The lungs: the posterior ends of these may b
seen as sacculated pouches, one on each side of th
liver, but they are frequently not visible unt:
the latter organ has been removed.

The stomach: a small portion of this is see
projecting beyond the lower left border of th
liver. /

13—2

196

ba |

ELEMENTARY BIOLOGY. [XI A

The intestine: a convoluted tube, continuous with
the stomach, and slung by a delicate membrane,
the mesentery: posteriorly the intestine ends in a
dilated portion (rectwm) which runs into the
pelvis.

The urinary bladder: a thin-walled bilobed sac
(which may or may not be distended) appear-
ing just in front of the pelvis.

The fat masses: long slender yellow processes
appearing on each side of the liver.

In &. temporaria, the urinary bladder is much

more deeply lobed and also much larger propor-
tionately, than in &. esculenta.

The liver.

a. Study its form more closely. (6. d.)

b. Raise its lower border; between its two lobes
will be seen a small greenish sac, the gall-bladder,

c. Carefully cut away the liver, except its deepest
part, close to the venous sinus.

d. Tease out a bit of liver in 0°75 sodic chloride
solution and examine with + obj.

a. Numbers of polygonal granular cells (hepatic

cells), with oil-drops in them, will be seen.

8. Treat with acetic acid: a nucleus, or sometimes

two, will be rendered apparent in each of the
cells.

The stomach, intestine, pancreas and spleen.

a.

Cut away the front of the pelvis with a stout
pair of scissors, taking care not to injure the
urinary bladder: pass a probe from the anus,

XU]

a,

é.

THE FROG. 19%

through the cloaca, into the rectum: uncoil the
intestine and spread out the mesentery, so far as

is possible without cutting the latter,

The spleen: a small red body lying in the
mesentery, near its attachment to the back
of the abdomen.

The stomach: an elongated sac on the lef:
side of the abdominal cavity: the narrower tube
(esophagus) opening into its anterior end.

The intestine: its length and varying diame.
ter; especially the great width of its recta
portion: its posterior termination in the cloaca

The pancreas: a pale-coloured compact mas:
lying in the mesentery near the commencemen’
of the intestine.

The mesentery: its width; mode of attach
ment to the intestine; the blood-vessels running
in it.

Divide the cesophagus close to the stomach anc
the rectum near the cloaca: remove all the portion
of alimentary canal between these two points
cutting through the mesentery.

Pass a probe up the cesophagus into the mouth

Open the upper end of the intestine and snijy
off a bit of its internal layer (mucous membrane
and mount in normal saline solution: examin:
with } obj.; on the fragment will be founc
minute prominences (representing the willy o
the higher animals) covered by a closely-se
layer of cells (epithelium).

198

ELEMENTARY BIOLOGY. [XIII.

9. The kidneys, These organs are now exposed as two
elongated deep red bodies lying in the posterior
part of the perivisceral space close to the verte-
bral column; clear away any bits of mesentery, &c.
which may cover them; note—

a.

7

The duct—ureter (female) or genito-urinary canal
(male)—running from the outer side of the pos-
terior part of each kidney to the cloaca. Open
the cloaca and pass a bristle into the opening of
one of the ureters.

In B. esculenta each duct is somewhat dilated
after leaving the kidney: it then narrows again
and opens on the posterior surface of the cloaca
by an oblique slit with sharply defined edges.
In R. temporaria the duct does not dilate, or
only very slightly; but on its outer side lies, in
the male, a glandular mass (vesicula seminalis),
from the inner side of which a number of minute
ducts open into the genito-urinary canal. The
aperture of the latter in the cloaca is round
and has tumid edges.

The vein (renal portal) entering the kidney at
its posterior outer border.

The great vein (vena cava inferior) lying between
the kidneys and chiefly formed by their efferent
(renal) veins.

Now that the cloaca is open, trace the open-
ing of the urinary bladder (B. 6. h) into it.

10. The generative organs.

a.

In the male.

The testes: a pair of ‘yellowish bodies lying

XIIL]

In

THE FROG. 19!

in front of the anterior ends of the kidneys
their form.
The ducts of each testicle (vasa efferentia) enter
ing the inner border of the kidney of the sam:
side in order to communicate with the genito
urinary canal (9. a).
Remove the testes: open one and press ou
some of its contents upon a slide and mount i)
common water: examine with 1 objective.
The spermatozoa: bodies provided with ;
small oval head and a long vibratile tazl in &
esculenta: in R. temporaria the oval head i
absent: their movements.

the female.

The ovary: an organ varying much in siz
with the season of the year. The numerou
ova in it.

The oviduct: a convoluted tube, not con
tinuous with the ovary, and running back t
open into the cloaca. The greater part of th:
oviduct is opaque and glandular; the part nea
the cloaca however is dilated, thin-walled anc
transparent. The oviducts open on the pos
terior wall of the cloaca a little anterior to th:
openings of the ureters.

11. The mouth, esophagus, and respiratory organs,
Open the mouth: note on its roof near thi
front the two hinder openings of the nasa
cavities (posterior nares); farther back, the tw
larger openings of the Hustachian recesses ; thi
long tongue in the floor of the mouth; fixed br
its front end to the lower jaw; its free, bifid
end turned towards the throat.

a.

ELEMENTARY BIOLOGY. [X1n.

b. Enlarge the mouth-opening by cutting through
the sides of the buccal cavity with a pair of
scissors: pull down the lower jaw so as to see
the chamber (pharynx) behind the mouth.

c. On the floor of the pharynx is a narrow opening
(the glottis): pass a probe down it through the
larynx and very short trachea into the lungs.

d. Remove the lungs; open one; it is a thin-walled
cavity with a sacculated inner surface.

e. Trace the cesophagus up to the pharynx.

C. THE CIRCULATION OF THE BLOOD IN THE FROG’S WEB.

1.

Get a piece of thin board, about 5 inches long and
24 broad; in the middle of one end of it cuta V-shaped
notch about the size of a spread-out frog’s web: place
the frog on the board, belly downwards, and fix it by
passing round it two or three turns of tape: next
tie threads round the toes of one hind-foot, and by
means of them spread out the web over the notch
in the board, taking great care that it is only very
lightly stretched. The animal should be kept moist
by a bit of wet blotting-paper spread over its back.

Examine the web with 1 inch obj.: Note—

a. The black pigment-cells in the skin; sometimes
irregularly branched; sometimes more compact.

b. The close network of blood-vessels lying deeper
than the pigment-cell layer.

a, The arteries, running mainly towards the free
~ edge of the web, and constantly diminishing
in size as they give off branches; the blood-
flow in them from larger to smaller branches.

XIII]

THE FROG. 201

. B. The capillaries, in which the arterial branches

end: small vessels forming a close network
and frequently branching or anastomosing with-
out much altering their size.

y. The veins, formed by the ultimate union of the
capillaries, and increasing in size by union
with one another; the blood-flow in them from
smaller to larger trunks.

c. The blood-flow: the current being marked by the
solid bodies (corpuscles) carried along in the fluid:
it is most rapid in the arteries; slowest, and most
constant, in the capillaries.

Place a small drop of water on a bit of a thin cover-
glass, and place the bit, with the water downwards,
gently on the web: then examine the following points
with 4 or 4 obj.; note—

a. The walls of arteries, capillaries, and veins.

a, The arterial walls, tolerably thick, seen as a
clear well-defined band on each side of the
blood-stream.

8. The capillary walls; difficult to see; merely a
thin somewhat more transparent boundary line.

y. The venous walls: much like the arterial.

b. “The blood-flow in the small arteries of the web.

a. The rapid stream in the middle, containing
most of the red corpuscles.

B. The slower stream along the edge (inert layer),
containing many colourless corpuscles.

c. The flow in the capillaries: much slower than in
the arteries; the frequent distortion of the red

202

ELEMENTARY BIOLOGY. [XII1.

corpuscles in the capillaries from pressure, &c.;
their elasticity as indicated by the readiness with
which they recover their shape when the cause
of distortion is removed; the way the white cor-
puscles creep along, with a tendency to stick
to the capillary wall.

4, Examine a drop of frog’s blood with the microscope
({ or 4 obj.). Sufficient blood to supply a whole
class for this purpose can be obtained by killing
one frog and opening its heart.

It consists of solid bodies (corpuscles) floating

in fluid (plasma).

a. The red corpuscles,

a.

Their form: oval when seen in front face;
almost linear in profile but slightly swollen at
the centre.

Their size: their length, breadth, and thick-
ness; measure.

Thetr colour: pale yellow, when seen individu-
ally ; redder if a thick mass of them is looked
at.

Their structure: they are homogeneous for the
most part, but possess a round granular central
nucleus.

Treat with water; they swell up and’ become
more spherical; their colouring matter is gra-
dually discharged ; the nucleus is rendered very
evident, and ultimately all the rest of the
corpuscle disappears.

Treat with dilute acetic acid; results same as
with water, but produced more rapidly.

XIl1.] THE FROG. 203

b. The white corpuscles.
Less numerous than the red: their colour, size,
granular character, nucleus, and changes of form
(amaeboid movements) : see III. B, P< 7 * Paros

D. THE EXAMINATION OF A PREPARED SKELETON.

The skeleton of a Frog may be prepared for ex-
amination by removing the viscera from the body,
and roughly dissecting away the muscles, &c. Then
place the remainder in water and let it macerate
for about a week; afterwards carefully pick away
the soft parts, with forceps, from the bones and carti-
lages.

a. Its general arrangement.

1. The central axis, consisting of the vertebral or spinal
column and of the central parts of the skull which
lie, in front of the spinal column, in the same antero-
posterior line.

2. Lateral parts, supported, directly or indirectly, by
the axis.
a. The appendages proper. (Limbs and limb-arches.)
a The fore-limbs: their supporting shoulder-
girdle or pectoral arch, not directly attached
to the axial column; the limb proper; its main
divisions; humerus, radius and ulna (the two
latter ankylosed), carpus and digits.
8B. The hind-limbs: their supporting arch (pelvic
girdte), carried directly by bony processes pro-
ceeding from the vertebral column; the limb
proper; its main divisions, os femoris, tibia
and fibula (ankylosed), tarsus, digits.
b. The facial and lateral cranial bones.

204 ELEMENTARY BIOLOGY. [XTIL

b. The vertebral column.

It consists of an anterior segmented portion (each
segment being a vertebra) and of a posterior
unsegmented portion (the urostyle).

1, Examine carefully and draw various aspects of a de-
tached vertebra, say the third.

a. Its solid flattened ventral part (centrum); with
an anterior concave and a posterior convex surface.

b. The neural arch: an arch of bone springing from
the sides of the dorsal aspect of the centrum of
the vertebra and not quite so wide as the cen-
trum in its antero-posterior diameter.

a. The transverse process: a bony bar on each
side, arising from the arch and passing outwards
and a little downwards.

8. The articular processes (zygapophyses); an an-
terior and posterior pair, springing from the
sides of the arch; the anterior, having their
smooth articular surfaces directed upwards;
the posterior with similar surfaces directed
downwards.

y. The short spinous process, springing from the
dorsal aspect of the arch and directed back-
wards,

c. The newral canal inclosed between the arch and
the body.

2. Examine the remaining vertebra.

a. The first vertebra (atlas): its body produced
forwards into a wedge-shaped process which lies

XII.]

THE FROG. 205

between the occipital condyles: its arch, some-
times incompletely ossified in the region of the
spinous process, which is rudimentary; posterior
zygapophyses only present: the large concave
anterior facets, partly on the arch and partly on
the centrum, with which the skull articulates.

The 2nd, 4th, 5th, 6th and 7th vertebre : closely
resembling the third, the chief differences being
found in the varying size and direction of the
transverse processes, all of which are smaller than
those of the third vertebra.

The 8th vertebra: the concave facet at each end
of its centrum.

The 9th vertebra (sacrum): its centrum; convex
in front and with two convex tubercles behind:
its large strong transverse processes (sacral ribs)
directed somewhat backwards and expanded at
their ends.

The posterior unsegmented portion of the vertebral
column (wrostyle).

a

An elongated rod-like bone, rather thicker towards
its anterior end, which bears two concavities.

Its posterior end; tubular in the dried skeleton,
but in the fresh state filled with a cartilage
which projects beyond it posteriorly.

The prominent ridge along its dorsal surface ;
wider and higher in front; getting thinner and
gradually disappearing towards the posterior end.

The small canal contained in the forepart of the
ridge,

206 ELEMENTARY BIOLOGY. pene

e. The two minute passages leading from the canal
to the outside of the ridge on each side.

4. The vertebral column as a whole.

a. Its composition.

a. Its anterior segmented part formed of the nine
vertebrae.

8. Its posterior unsegmented part formed by the
urostyle and nearly as long as the segmented
part.

b. Its ventral surface.

a. The solid bony axis formed by the bodies of
the vertebree in front and continued posteriorly
by the ventral rounded part of the urostyle.

8. The transverse processes: their size and direc-
tion: those of the second vertebra, slender
and directed nearly straight outwards; those
of the third and fourth, largest of all and with
a distinct inclination backwards: those of the
fifth, sixth, seventh and eighth vertebre
smaller than the rest and directed nearly out-
wards ; those of the ninth, very stout, directed
outwards upwards and backwards, and having
the iliac bones attached to their distal ends,

’ The transverse processes arise from their arches
closer to the centrum in the second, third and
fourth vertebrae than in the others.

y. The inter-vertebral foramina: the interspaces
left between each pair of neural arches, below
the level of the zygapophyses,

XU]

Cc.

C.

d.

THE FROG. 207

The dorsal surface of the spinal column.

a. The ridge down its middle formed by the row

of spinous processes, and continued behind
by the dorsal ridge of the urostyle.

8. The lateral prominences caused by the articular

processes : the articulations between the anterior
articular processes of one vertebra, and the
corresponding posterior processes of its pre-
decessor.

y. The spaces left between the dorsal part of each
neural arch and its successor: between the
atlas and the second vertebra and between
the eighth and ninth vertebree ; these are almost
obliterated by the approach of the respective
arches.

The neural canal.

a. Closed by the centra of the vertebree beneath,
and incompletely by the neural arches on the
sides and above: its backward continuation as
the canal in the front part of the ridge of the
urostyle.

8B. The communication with it, of the inter-

vertebral foramina (4 6. y), and the dorsal
intervals between the neural arches (4. c. ¥):
also of the openings in the urostyle (3. e).

The skull. The prepared bony skull of the frog
is difficult to understand, for two reasons; firstly,
on account of the dried-up condition of the carti-
lages of which, in the fresh state, it is in part com-
posed; and, secondly, on account of the tendency of
many of its constituent bones to become ankylosed

ELEMENTARY BIOLOGY. [XII I.

together in the adult: the following points can
however be made out with tolerable ease. Drawings
should be made of each aspect of the skull.

1. Examine the posterior end of the skull.

a.

The large aperture (foramen magnum) in the
middle line, leading into the cramial cavity.

The convex surface (occipital condyle), on each
side of the foramen magnum, which articulates
with the corresponding concave facet on the
front of the atlas.

The bone bearing the condyle on each side and,
with its fellow, enclosing the foramen magnum,
is the ewoccipital.

The thick bone running outwards in front of the
exoccipital, on each side, protects the front part of
the internal ear, and is the pro-otic bone.

Between these two bones, on the outer side of the
chamber which contains the organ of hearing
(periotic capsule,) is a cartilaginous interspace
containing an oval aperture, the fenestra ovalis.
In this is fixed the inner end of a partly carti-
laginous and partly osseous rod, the columella
auris.

Attached to the outer end of the pro-otic bone is
a hammer-shaped bone—the squamosal, which
extends from the pro-otic bone to the articulation
of the lower jaw.

2.- The roof of the skull.

a.

Passing forwards from the exoccipitals are two
long flat bones, the parieto-frontals, one on each

X11, ]

C.

THE FROG. 209

side of a median suture which answers to the
sagittal and frontal sutures in man.

In front of these come two triangular bones—
the nasals.

In front of the nasals are two other bones, which
belong rather to the ventral than to the dorsal
face of the skull. They form the extreme front
of the snout, and each sends a process towards
the nasals; these are the premaaillary bones.

3. The base of the skull.

a.

Running along the greater part of the floor of
the cranial cavity, from the occipital foramen
to the vomers, is a bone shaped like a dagger
with a short handle and a strong guard. The
latter spreads out under the pro-otics. This is the
parasphenoid bone.

Appearing at the base of the skull, at the front
end of the parasphenoid, is the girdle-bone or
sphenethmoid (which represents several bones
joined together); this bone closes in the floor and
sides of the forepart of the cranial cavity and
also its roof, being concealed in the latter place
by the anterior ends of the parieto-frontals. The
sphenethmoid has a single cavity behind, which
enters into the formation of the cephalic chamber,
and two cavities in front, one for each nasal
chamber, separated by a septum.

Running out transversely from. the girdle-bone
and the anterior end of the blade of the para-
sphenoid on each side, is the slender palatine.

14

10

d.

ELEMENTARY BIOLOGY. [XIII

In front of the end of the blade of the para-
sphenoid and of the palatines are two broad
irregularly shaped bones, each bearing an oblique
row of teeth on its posterior part: these are the
vomers.

The middle anterior boundary of the contour of
the skull, in this view, is formed by the denti-
gerous parts of the pre-maxille; and, behind
them, by the maxille and the quadrato-jugal bones
(4. a. b). Running backwards from the outer
end of the palatine, and closely applied to the
maxilla, is a bone, which soon separates from the
maxilla, and becoming broad and stout, bifurcates;
the inner process nearly joins the parasphenoid
and is moveably articulated with the skull; the
outer runs along the inner face of a cartilage (the
suspensoriwm), on the outer face of which the squa-
mosal rests: this is the pterygoid bone.

At the outer edge of each vomer, immediately
in front of the palatine, is an aperture which
leads into the nasal cavity. These two apertures
are the postertor nares.

4. The side of the skull.

a

Running back from that part of the pre-maxilla
which bounds the gape is a long bone, forming
almost the whole of the rest of the upper edge of
the gape; this is the mamilla.

Joined to the posterior end of the maxilla is a
small bone, which at its posterior end is attached
to the distal portion of the squamosal. This is
the quadrato-jugal.

XI1.]

THE FROG. 211

ce. The under jaw or mandible consists of two distinct
portions, or rami, which meet in the middle line
in front, and which, behind, articulate with the
extremities of the suspensorial cartilages. In the
articular end of each suspensorial cartilage there
is an ossification which represents the quadrate
bone in other Vertebrata, and: is united with the
jugal to form the quadrato-jugal.

In each ranws three pieces may be made out—

a,

A central axis formed of cartilage (Meckel’s
cartilage), which enlarges at its posterior end
in order to articulate with the suspensorial
cartilage, while at the opposite or symphysial
end it is ossified to form the mento-Meckelian
bone.

A posterior inferior piece, which runs nearly to
the middle line in front (angulo-splenial) and
partly ensheaths the foregoing.

A small anterior superior piece (dentary).

hyoid bone or cartilage.

Its broad somewhat tetragonal central part
(body), bearing a number of processes, viz.—

The anterior cornua, proceeding from the front
of the body on each side: each is a long
slender curved cartilage running at first for-
wards, then backwards and outwards, and
finally forwards and upwards, to become at-
tached to the periotic capsule beneath the

fenestra ovalis.
14—2

1.

é.

ELEMENTARY BIOLOGY, [X1I1.

The posterior cornua, or thyro-hyals ; bony, and
shorter and thicker than the anterior cornua:
attached to the posterior border of the body
near the middle line and diverging as they run
backwards.

Two pairs of smaller processes formed by the
elongation of the anterior and’ posterior angles
of the body of the hyoid.

The sternum and shoulder-girdle.

Their general arrangement: they form an incomplete
ring round the fore-part of the trunk: this ring is
composed partly of bone, partly of cartilage. Note
the hollow (glenoid fossa) with which the fore-limb
articulates.

a.

B.

b.

The sternum: situate in the ventral median line
and made up of several parts: beginning behind
we find—

The wiphisternum; a thin cartilage, wide behind,
narrow in front, where it passes into—

A median cartilage ensheathed in bone, the
sternum proper. The anterior end of the ster-
num unites with the posterior and internal
angles of the coracoids (6 y), the inner edges
of which meeting in the middle line separate
the sternum from—

The omosternum, consisting of a slender, flat-
tened bone, terminated in front by an expanded
cartilage. The posterior end articulates with
the preecoracoids and the clavicles.

The shoulder-girdle: beginning dorsally, it ex-
hibits on each side—

Xill.]

THE FROG. 213

A thin expanded dorsal portion, partly carti-
laginous, partly ossified: the supra-scapula.

Next a bony segment—the scapula, the pos-
terior inferior edge of which is excavated by
the glenoidal fossa.

The ventral parts of the shoulder-girdle, which
lie between the two scapule, meet in the middle
line; thé part on each side is subdivided into
an anterior and a posterior portion by a large
foramen.

The bony piece running behind the foramen,
from the scapula almost to the middle line,
is the coracotd. Where the coracoid unites
with the scapula it contributes to the forma-
tion of the glenoidal cavity.

The adjacent margins of the two coracoids
are fringed with cartilage (epicoracoid), which
passes in front of the foramen into a bar of
cartilage—the precoracoid—-which, externally,
is continuous with the cartilage which lies be-
tween the scapula and coracoid and helps to
bound the glenoidal cavity.

Closely attached to the fore-part of the pre-
coracoid lies a bone, the clavicle, the outer end
of which articulates with the coracoid and
scapula, the inner with the omosternum.

Draw the whole pectoral arch carefully, shading differ-
ently the bones and cartilages.

f. The bones of the fore-limb.

a.

The arm-bone (humerus).

ELEMENTARY BIOLOGY. [X11

a. A somewhat cylindrical bone, with an articular
expansion at each end and a shaft uniting
them.

B. The great ridge (deléoid crest) on its antero-
internal surface, to which a muscle was at-
tached.

The development of this crest is greater in the
males than in the females,

b. The bone of the forearm.
a. Hollowed out above to fit the lower end of the
humerus.

8. Shewing below a tendency to divide into the
two bones of which it is made up; viz. the
radius and the wna. When the limb is
stretched out at right angles to the body with
the pollex forwards, the radius is on the
anterior, and the ulna on the posterior side of
the axis of the limb.

c. The carpus. Two bones (a, b) articulate with the
ankylosed radius and ulna, A third bone (c), on
the radial side of the carpus, articulates only with
the carpal bones on the proximal and distal sides
of it. A large bone (d) occupies two-thirds of the
ulnar side of the carpus, and articulates with
a, b and ¢ on one side, and with the third, fourth
and fifth metacarpals on the other. Two small
ossicles articulate with the distal face of c and
bear the first and second metacarpals.

d. The digits.

Five in number, the first, (radial one) being, how-
ever, rudimentary: beginning at the ulnar side
we find—

XIII]

THE FROG. 215

The fifth digit (that on the outer or ulnar side
of the limb) : it presents a cylindrical proximal
bone (metacarpal) followed by three others
(phalanges), each shorter than its predecessor.

The fourth digit: a metacarpal bone and three
phalanges.

The third digit: a metacarpal bene with two
phalanges.

The second digit: a metacarpal bone with two.
phalanges.

The first digit (pollea) consists only of a small
metacarpal bone.

g. The pelvic girdle,

a. Its general form: V-shaped, with the apex turned
backwards.

The concavity (acetabulum) on each side with
which the thigh-bone articulates.

The triradiate fissure running through the aceta-
bulum and dividing each half of the pelvis into
three pieces, viz.—

An anterior elongated piece (tliwm); subcylin-
drical in front, where it articulates with the
sacrum ; bearing behind, on its dorsal aspect, a

laterally compressed ridge of bone (crosta ili) ;

it forms almost half of the acetabulum.

A posterior, irregularly rounded piece (¢schiwm) ;
closely united posteriorly with its fellow, in the
middle line.

216

ELEMENTARY BIOLOGY. [ XIII.

A small triangular piece (os pubis), (cartilagin-
ous except in old frogs), wedged in between
ilium and ischium, and meeting its fellow in
the median ventral line, thus forming the sym-
physis pubis.

h. The bones of the lower limb.

The thigh-bone (os femoris); its long cylindrical
shaft and expanded articular extremities.

The leg-bone (os cruris).

A very long cylindrical bone, expanded at each
end.

The grooves on it; one running along the
whole ventral surface, but most marked near
the ends; other grooves on the dorsal surface,
one at the upper, another at the lower extrem-
ity: these indicate that the os cruris is really
made up of two united bones, the fibula and
the tibia. When the limb is stretched out at
right angles to the body, the tibia is anterior,
corresponding with the radius; and the fibula,
posterior, corresponding with the ulna.

The tarsus.

Two elongated bones (separate in the middle
but united by confluence of their cartilaginous
extremities) articulate with the ankylosed tibia
and fibula; the anterior, or tibial, of these is the
astragalus; the posterior, or fibular, the eal-
caneum.

With the distal ends of these, two partially
ossified cartilages, one on the calcaneal and

XIII]

_ ‘THE FROG. 217

the other on the astragalar side, articulate.
The latter is connected by ligamentous fibres,
within which a nodule of cartilage may be
found, with the first and second metatarsals,
and supports the calcar (d. ).

The digits. Five in number; the internal one
the shortest, the fourth the longest. Their com-
position—

The first, or hallua (the most internal); a
metatarsal bone, followed by two phalanges.

The second : same as a, but longer.

The third: a metatarsal bone with three pha-
langes.

The fourth: a metatarsal bone and four
phalanges.

The fifth : like the third, but a little shorter.

On the anterior or tibial edge of the foot there
are two, small, more or less cartilaginous, ossicles,
articulated with the tarsus (¢. 8) in such a
manner as to resemble an extra digit. This
calcar, or spur, supports the horny prominence
referred to above.

E. DISSECTION OF THE FROGS HIND-LIMB TO ILLUSTRATE
ITS MYOLOGY.

(For the following dissection it is desirable to have a frog

which has been lying some time in spirit.) 2

1.

Lay the animal on its back, and make an incision
through the skin on the front of the limb from the
symphysis pubis to the ankle; then reflect the skin

218

ELEMENTARY BIOLOGY. [x III.

to each side so as to lay bare the parts beneath it;
in turning it back note the loose bands and fibres
(subcutaneous areolar tissue) with large lymph-spaces
between them, which unite the skin to subjacent
parts, and which have to be cut through.

A number of muscles will now be exposed on the
front of the thigh and leg.

The superficial muscles on the front of the thigh.
Separate these gently from one another, tearing
through the connective tissue which unites them.

a. Each is chiefly made up of a mass, the belly of
the muscle, which is nearly white and readily
tears into bundles in a muscle which has been in
spirit ; but is softer, redder, and does not so easily
split up in a fresh muscle.

b. At both ends, in most cases, the belly is replaced
by dense shiny tissue forming a tendon.

ce. The tendons are fixed directly or indirectly to

some of the neighbouring bones, the less move-

able attachment being the origin of the muscles ;

the point of attachment to the more moveable
bone, its insertion.

d. The names of the muscles laid bare on the front
of the thigh, are—

a. The sartorius: a thin flat riband-like muscle

running down the middle; it arises from the

symphysis pubis and is inserted into a tendi-

nous expansion (aponewrosis) on the inner side
of the knee-joint.

B. The adductor magnus: it becomes superficial
along the upper two-thirds of the inner border
of the sartorius,

XIII]

THE FROG. 219

The adductor brevis: a little bit of it is seen
on the inner side of the adductor magnus,
close to the symphysis pubis.

The rectus internus major: a large muscle
running along the whole inner side of the
thigh; arises from the symphysis pubis below
the sartorius and is inserted into the same
aponeurosis as that muscle,

The rectus internus minor: a thin muscle lying
inside and rather behind the rectus internus
major. It arises from the pelvis close to the
anus and is inserted into the aponeurosis about
the knee-joint.

The adductor longus: it is partly superficial
along the outer edge of the sartorius.

The vastus internus: a very large muscle on
the outer anterior aspect of the thigh; arising
from the pelvis close to the hip-joint, it joins,
below, two muscles on the back of the thigh
(4. a. 8. y), and all end in a tendon which is
inserted into the aponeurosis over the front of
the os cruris.

Cut across the belly of the sartorius, and turn its
ends out-of the way; dissect out the origin and
insertion of the adductor longus and the adductor
magnus (d. ¢ and 8).
The adductor longus arises from the anterior
inferior part of the symphysis of the iliac bones; ‘
by its lower end it joins the adductor magnus.

The adductor magnus, arises from the pelvis,
between the origin of the sartorius and that
of the rectus internus major. Its fibres are

220 ELEMENTARY BIOLOGY. [ XII.

inserted directly (2. e. without the intervention
of a specialised tendon) into the inner side of
the distal half of the femur.

3. The deep muscles on the front of the thigh.

a. Divide and reflect the adductor longus, rectus
jnternus major and rectus internus minor. The
following muscles will be displayed :—

a The pectineus: it lies at the upper part of the
thigh immediately internal to the vastus inter-
nus: it arises from the front of the pelvis, close
to the symphysis, and is inserted into the
anterior surface of the distal half of the femur.

B. The adductor brevis (2. d. ry): it lies along the
inner side of the pectineus and arises and
is inserted close to it.

y. The semitendinosus: this is a long slender
muscle lying beneath the rectus internus major
and bifurcated at its upper end: its two heads,
thus formed, arise, one (anterior head) from
the pelvis between the ischial symphysis and
the acetabulum; the other (posterior head)
from the ischial symphysis: the muscle termi-
nates below in a rounded tendon which is
inserted along with the sartorius.

4. Turn the frog over on to its belly, and remove the
skin from the back of the limb.

The muscles on the back of the thigh, These are :—

a. The triceps femoris: avery large muscle on the
outer side, divided above into three heads, which
are often regarded as separate muscles, viz.

Sti

THE FROG, 221

The vastus internus: the anterior division,
which has been already seen on the front of
the thigh. (2. d. 7.)

The vastus externus: the posterior division ; it
arises from the hinder edge of the iliac bone.

The rectus femoris anticus : the middle division
of the triceps; it arises from the posterior part
of the ventral border of the iliac bone. For the
insertion of the triceps femoris, see 2. d. 7.

The gluéceus: this muscle arises from the hinder
two-thirds of the external surface of the ilium;
it runs down between the vastus externus and
the rectus anticus to be inserted into the back of
the head of the femur.

The pyrtformis. This arises from the posterior
part, of the urostyle and, passing inside the vastus
externus, is inserted into the shaft of the femur.

The biceps femoris: a long thin muscle, lying
along the inner side of the vastus externus; it
arises from the iliac bone above the acetabu-
lum; below it divides into two pieces, one of
which is inserted into the middle of the shaft
of the femur, while the other ends in a rounded
tendon which is inserted into the back of the
distal end of the same bone.

The semimembranosus : a large muscle inside the
biceps; it arises from the upper posterior part
of the iliac symphysis and is inserted into the
aponeurosis round the knee-joint.

Lying deep in the thigh, between the biceps
and semimembranosus muscles, will be seen the
femoral vessels and the scratic nerve.

229
I.
g.
A
5. The
a
a

ELEMENTARY BIOLOGY. [ XIII.

Divide and reflect the vastus externus and the
biceps: beneath them will be laid bare—

The ileo-psoas: it arises from the internal
surface of the posterior part of the ilium and
is inserted into the posterior aspect of the shaft
of the femur.

Remove the pyriformis, cut through the semi-
membranosus close to its origin and throw it
downwards; this brings into view a small tri-
angular muscle—

The quadratus femoris, which arises from
the ilium behind the acetabulum and is inserted
into the middle of the shaft of the ventral surface
of the femur.

The obturatorius: this is a small muscle lying on
the dorsal surface of the hip-joint.

muscles of the leg.

Turn the frog on its back, and remove the skin
from the foot: fix the dorsal surface of the foot
upwards. The os cruris will now be seen running
down the middle of the leg. Lying on its present
inner (proper dorsal) side are two muscles, viz—

The gastrocnemius: a muscle with a great
fleshy belly; it arises above by two tendons;
one (much the larger) is inserted behind the
knee-joint partly into the femur, partly into
the os cruris; the other joins the aponeurosis
on the outer side of the knee-joint. Below,
the muscle ends in a great tendon (éendo
Achillis), which terminates in an aponeurosis
.on the plantar surface of the foot.

XII]

THE FROG. 223

The tibialis posticus: a slender muscle covered
in great part by thé gastrocnemius; it arises
from the greater part of the posterior surface
of the os cruris and, passing along the inner
side of the ankle-joint, is inserted into the
astragalus,

On the opposite side of the bone lie four
muscles : viz.—

The peroneus: the largest and most external ;
it arises from the outer side of the distal
articular end of the femur and, running past
the outer side of the ankle-joint, is inserted
into the calcaneum.

The tibialis anticus: a small muscle inside and
beneath the peroneus; it arises from the front
of the lower end of the femur and from the
capsule of the knee-joint ; below it divides into
two parts, one inserted into the dorsal side of
the astragalus, the other into the calcaneum.

The extensor cruris brevis: this lies internal to
the upper part of the last muscle; it arises
from the front of the distal articular end of
the femur and is inserted into the middle
third of the os cruris.

The flexor tarsi anterior: this arises where
the last muscle ends, and is inserted into the
dorsal side of the astragalus.

6. The nerves of the hind-limb.

These are now to be dissected out in that leg which
has not been used for the muscles.

224

a

b.

%y.

¢.

a

ELEMENTARY BIOLOGY, [XIII

The sciatic nerve.

Find it on the dorsal side of the thigh by sepa-
rating the biceps and semimembranosus mus-
cles ; it appears as a slender white cord.

Dissect it out carefully in the middle of the
thigh, noting the branches it gives off to the
various muscles,

Follow it up to the abdominal cavity, cutting
away the muscles, lying between the ilium and
urostyle, which cover: it in.

Follow it down towards the knee: a little way
above the joint it divides into two branches;
one (posterior tibial) runs inside the large head
of the gastrocnemius muscle, the other (pero-
neal) between its two heads.

The posterior tibial nerue.

Note especially the branch which it gives off
opposite the knee-joint, and which, after run-
ning for some way along the deep surface of the
gastrocnemius, enters that muscle.

Follow the nerve down the leg: it runs along
the tibialis posticus muscle, giving off branches
here and there.

Near the foot it turns to the back of the
ankle-joint and enters the plantar surface of
the foot, where it ends in a number of branches,

The peroneal nerve.

This runs down the leg close to the peroneus
muscle, giving off branches on its way.

XII] THE FROG. 225

8. Towards the bottom of the leg it comes to
the front of the ankle-joint, and divides into
branches which are distributed on the dorsum
of the foot.

[F. DissEcTIoN OF THE VASCULAR SYSTEM.

The dissection of the blood-vessels is much facilitated by
previous injection: this may be done as follows: Dissolve
some gelatine, with the aid of heat, in a coloured fluid .
(solution of carmine or of Berlin blue) ; the gelatine ought to
be added in such quantity that the fluid just sets when cold :
kill a frog with chloroform; lay bare its heart, taking care
not to injure the anterior abdominal vein; prick a small
hole in the venous sinus and sop up any blood that flows
out; pass a ligature round the truncus arteriosus ; make a
small aperture in the ventricle and pass a glass tube, drawn
out to a fine point, through the ventricle into the arterial bulb,
and tie it in; fill this tube with normal salt solution and
connect it, by a bit of gutta percha tubing, with a syringe
filled with the injecting fluid, which should not be warmer
than 35°C. ; inject very slowly and with slight pressure. The
venous system may also be readily injected by dividing the
anterior abdominal vein and passing the syringe into its pos-
terior end. When the injection is finished put the animal in
alcohol for some hours. ]

1. The anterior abdominal vein.

a. Carefully dissect the belly-walls away from the
anterior abdominal vein: at its posterior end
this vessel will be found to get a small branch
from the front of each thigh and then to divide
into two large trunks (pelvic veins) which run, one
on each side, towards the back of the thigh.

M. 15

226

ELEMENTARY BIOLOGY. [ XIII.

Turn the animal over and follow one of these
trunks back: it will be found to be continuous
with the sciatic vein, which ends in the pelvis
by dividing into this and another (renal portal)
vessel,

Trace the anterior abdominal vein forwards: it
divides into two branches, one of which goes to
the right and the other to the left lobe of the
liver.

Raise the liver, and note the vena porte which enters
its lower surface; it is formed by the union of a vein
(gastric) from the stomach with one (lieno-intestinal)
from the spleen and intestines. The gastric divi-
sion of the vena porte communicates by a large branch
with the left division of the anterior abdominal vein.

The veins of the head and neck and fore-limbs.

a.

Remove the liver, being careful not to injure
the inferior vena cava beneath it.

Pass a bit of glass tube down the frog’s gullet
(in order to stretch out the neighbouring parts)
and clean the aortic arches: passing in front
of each aortic arch, near its point of division is—

The external jugular vein, running up the side of
the throat towards the angle of the lower jaw
and receiving the veins of the mandibular and
lingual regions.

Follow this vein down towards the heart: a
little way below the aortic arch it is joined by
another large vein—

XII1.] THE FROG. 227

e. The subclavian: follow this outwards; it will
be found to be formed mainly by the union
of two large branches: one (aaillary or brachial
vein) coming from the antebrachium and manus ;
the other (musculo-cutaneous) from the back and
head.

jf. The innominate vein is formed by the union of
the internal jugular vein, which brings back the
blood from the brain and spinal cord, with the
subscapular vein returning the blood from the
brachium and shoulder.

g. The superior vena cava (right and left): this
is formed by the union of the subclavian, external
jugular and innominate veins on each side: follow
it to the heart, where it ends by entering the
sinus venosus.

4. The inferior vena cava and renal portal veins.

a. Divide the alimentary canal above the stomach
and also close to the cloaca, and remove the
intermediate portion: dissect out the veins con-
nected with the kidneys.

b. The renal portal vein: running from the bifur-
cation of the pelvic vein to enter the lower-
outer border of the kidney.

c. The inferior vena cava: the large vein lying
between the kidneys and chiefly formed of
branches from them, but also getting branches
from the generative organs and the liver.

d. Follow it up to its anterior ending in the

sinus venosus.
15—2

5.

6.

ELEMENTARY BIOLOGY. [xu

The aortic arches and their branches.

a. Dissect out the branches of the aortic arches:
three on each side.

a. The anterior division (carotid trunk): it, after
giving off a branch (lingual artery) which runs
up the throat, ends in a small red body, the
carotid gland, from which other arteries pro-
ceed.

8. The systemic aortic arch: this is the middle
and largest division : it runs round the throat
towards the vertebral column, giving off on
its way the subclavian artery which runs to
the fore-limb.

y. The pulmo-cutaneous artery, or posterior division
of the aortic arch: it runs to the root of the
lung, giving off on its way a cutaneous branch
which runs out to the integument about the
shoulder.

b. Imbed in paraffin an aortic arch which has been
hardened in spirit and cut transverse sections
of it: examine with 1 inch obj. Note the two
partitions subdividing it into three channels.

Take a frog which has been in spirit for a time: open
its pleuroperitoneal cavity, and carefully dissect away
the ventral wall of the aortic bulb. Note in its cavity
the moveable partition or valve, fixed on its dorsal
border but free on the ventral. Also make out the
cavities of the two auricles; the partition separating
them ; the spongy cavity of the ventricle ; the opening
between the ventricle and the bulbus arteriosus,

XIII.]

7. The

a.

8. The

THE FROG. 229

dorsal aorta and its branches.

Remove the kidneys with vena cava inferior and
the generative organs: the dorsal aorta is then
laid bare lying on the bodies of the vertebra.

Follow the systemic aorte (5. a. 8) round the
neck; they will be found to unite beneath the
vertebral column to form the dorsal aorta.

Follow the aorta backwards: it gives off many
branches on its course; note the large one (caliaco-
mesenteric artery) arising from it just below its
point of formation.

Small branches to the renal and generative
organs (only the cut ends of these branches can
now be found) and to the muscles of the back.

Near the pelvis it ends by dividing into two
trunks (the lac arteries) which run behind the
pelvic bones, giving off hypogastric branches to
the bladder and the walls of the abdomen.

Turn the animal over on to its belly and trace
the iliac arteries backwards: they are mainly
continued down the thigh as the femoral arteries.

pulmonary veins.

Trace them from the left auricle to the lungs.
Examine the left auricle carefully and find the
opening of the common pulmonary vein into it.

G. THE NERVOUS SYSTEM OF THE FROG.

1. The method of exposing the brain and spinal cord.—
Take a frog which has been a day or two in spirit ;
divide the skin along the middle of the dorsal sur-
face from the snout to the anus and reflect it to

ELEMENTARY BIOLOGY. [x1.

each side, noting the small nerves running into it
on each side of the middle line; remove the muscles
lying on the arches of the vertebra; open the neural
canal by dividing the membrane between the atlas
and occiput; then introduce one blade of a small, but
strong, pair of scissors into the cranial cavity, and cut
away bit by bit the bones which form the roof of the
skull, taking care that the point of the scissors does
not injure the brain. Next remove the upper part
of the arches of the vertebre in a similar manner. A
delicate pigmented membrane (the pia-mater) is now
laid bare, covering the brain; over the spinal cord
it is usually concealed by a quantity of soft material ;
gently remove this with a pair of forceps or wash it
away with a syringe.

The brain.

On the dorsal aspect of the brain, which is now exposed,
the following parts will be seen;—

a. In front, two elongated masses forming about the
anterior half of the brain: a slight transverse
depression divides each into an anterior smaller
and a posterior larger portion. The inner faces
of the anterior portions are closely united to-
gether; those of the posterior portions are sepa-
rated by a cleft. The posterior portions are the
cerebral hemispheres (prosencephalon) ; the an-
terior, the bases of the olfactory lobes (rhinence-
phalon).

a. The olfactory lobes become narrowed into two
rounded trunks (commonly termed the olfactory
nerves), which leave the skull, and applying them-
selves to the outer face of the lining membrane of

xum1.]

Cc

3. The

a.

a.

THE FROG. 231

the nasal chamber, give off a number of branches
which are distributed on that membrane.

The thalamencephalon: lying between the poste-
rior ends of the cerebral hemispheres: on it are
to be noticed—

The pineal gland: avery small mass in front;
not composed of nervous tissue.

The thalami optic: the nervous masses seen
below the pineal gland: between them lies a
narrow cavity, the third ventricle.

The optic lobes (mesencephalon): a pair of rounded
eminences lying behind the thalamencephalon.

The cerebellum (metencephalon): a narrow trans-
verse band lying behind the optic lobes.

The medulla oblongata (myeloncephalon): the
portion of the brain lying behind the cerebellum.

Lying on the medulla oblongata is a triangular
depression (4th ventricle) with its apex turned
backwards,

spinal cord.

Its form: wide in front, but narrowing rapidly
about the 5th or 6th vertebra, and thence con-
tinued along the neural canal as a slender taper-
ing filament.

The groove (posterior fissure) running along its
middle line.

The spinal nerves arising from it.

Ten on each side.

232

ELEMENTARY BIOLOGY. [ x1.

B. Each arising by two roots (anterior and poste-
rior): these are most easily seen in the 7th,
8th and 9th nerves, where they are much
longer than in the others. Sometimes the an-
terior root is double.

y. The direction of the roots: directly outwards
in anterior nerves; obliquely backwards in the
4th, 5th and 6th; almost directly backwards
for a considerable distance in the neural canal
in the 7th, 8th, 9th and 10th.

6. The point of union of the roots to form a nerve-
trunk, in the intervertebral foramina.

Draw the exposed parts of the brain and spinal cord.

Divide the olfactory lobes, and raise the front end of
the brain; turning it back gradually, divide with a
sharp scalpel any nerves that are seen running from
it to the cranial walls: most of the nerves being small,
they will probably be torn across unobserved, but the
large optic nerves will at any rate be seen: next
divide the nerve-roots of the spinal cord; remove it
and the brain together and place them with the
ventral side upwards.

a, On the under surface (base) of the brain will be
seen—

a. The optic commissure or chiasma opposite the
posterior end of the cerebral hemispheres ;
with the optic nerves diverging from its anterior
end and the optic tracts entering it posteriorly.

8. Lying behind the optic commissure, between
the optic tracts, is a small eminence—the
pituitary body.

XIL]

THE FROG. 233

On each side of the two last-mentioned struc-
tures and arched over in front by the optic
tracts, are the crura cerebri.

Divide the cerebral hemispheres horizontally with
a sharp scalpel: in each will be found a cavity—
the lateral ventricle. Each lateral ventricle com-
municates with the third ventricle. The optic
lobes, divided in the same way, will be seen to
roof over a cavity which communicates with the
third ventricle in front, and with the fourth
ventricle behind.

The spinal cord.

The anterior fissure running along its ventral
surface.

Its form: subcylindrical; wider from side to
side (especially opposite the second pair of
nerves) than dorso-ventrally.

Imbed it in paraffin and cut a transverse sec-
tion: mount in glycerine, and examine with 1
inch obj.; note its peripheral portion (white
matter) different in appearance from the cen-
tral parts (grey matter): the canal (canalis
centralis) running up its centre.

5. Turn the frog over on to its back, lay open its abdomi-
nal cavity and remove all the alimentary canal from
the gullet to the rectum, along with the liver, kidneys

and generative organs,

6. The sciatic plexus,

a.

This is now seen as a number of large nerve-cords
on each side of the dorsal aorta; note the com-
munications between the different cords of the

same side.

234

ELEMENTARY BIOLOGY. [XIII

Follow down the plexus on one side: it ends
below in a large trunk which is continuous with
the sciatic nerve.

Trace the nerve-trunks forming the plexus up to
the spinal column. They are continuous with
the 7th, 8th, and 9th spinal nerves.

7. In front of the sciatic plexus—lying on the muscles
bounding posteriorly the abdominal cavity—are three
nerves running obliquely downwards and outwards on
each side: they are continuous with the 4th, 5th and
6th spinal roots.

8. Some nerves of the neck,

a

Pass a piece of tubing down the gullet so as to
distend it: and then carefully remove the mylo-
hyoid muscle (B. 6. a).

Find the posterior cornu of the hyoid bone on
one side: from it a slip of muscle (petrohyoid)
will be seen passing up towards the occipital
region of the skull. Lying along the posterior
border of this muscle is the pnewmogastric nerve;
follow its branch to the heart.

Lying on the petrohyoid and in front of the
pneumogastric, from which it arises, is the laryn-
geal nerve.

Some way in front of the laryngeal nerve is seen

the glossopharyngeal nerve, turning up towards
the front of the jaw.

Superficial to the glossopharyngeal, but with a

generally similar direction, is the hypoglossal nerve
(B. 6. a).

XII] THE FROG. 235

9. The brachial nerve.

Lay it bare in the arm-pit and follow it back to the
spinal cord: it is formed by the union of the 2nd and
8rd spinal nerves,

10. The sympathetic system.

a. Gently raise the aorta: along each side of it will
be found the main sympathetic trunk.

b. A slender cord, with enlargements (ganglia) on
it at intervals.

c. Note the branches passing between its ganglia
and the nerves of the sciatic plexus.

d. Carefully dissect out the gangliated cord for its
whole length: ten ganglia, each provided with
communicating branches to other (spinal) nerves,
will be found on it.

H. THE ORGANS OF SPECIAL SENSE.

The complete examination of these, especially as re-
gards their histology,'is difficult, and necessitates the em-
ployment of niceties in manipulation which it would be
beyond the scope of this work to describe, so that in the
following account attention is mainly given to those
points which can be made out without the microscope.
A brief account of the microscopic structure of the retina
will however be found below (J. h).

a. The Eye.

1. Take an uninjured frog and examine its eye. It will
normally be found to project considerably above the
top of the head, but if touched it is withdrawn into a
sort of socket. If the animal’s mouth be opened, an
elevation, caused by the eye-ball, will be seen on its

236

ELEMENTARY BIOLOGY. [xin

roof, and this is more prominent when the eye-ball is
retracted.

a.

Gently touch the eye and observe how it is closed,
by the pulling over it of the lower transparent
eye-lid. The upper eye-lid is very small and
hardly moveable.

When the eye is open, observe the parts exposed:

The transparent cornea covering all its exposed
surface.

Through the cornea is seen the iris, a mem-
brane coloured by brown and golden pigment,
the latter forming a very brilliant ring around
the inner margin of the iris. The lower mar-
gin of this ring is interrupted at one point,
the yellow pigment being there absent, and
from the break a faint dark line can be traced
downwards through the rest of the lower part of
the iris.

The elliptical opening or pupil in the middle
of the iris with its long axis directed antero-
posteriorly.

Kill the frog (by chloroform or by pithing), and care-
fully dissect away the parts from around the eye-ball,
cutting away, with the rest, the part of the upper jaw-
bone which forms the lower boundary of the socket of
the eye-ball, or the orbital cavity.

a.

B.

As the surrounding tissues are cleared away
from the eye-ball notice the small muscles
which are inserted into it.

At the back of the eye-ball and passing into it
will be found the optic nerve.

Divide the optic nerve and, having thus detached the

XIIL.}

THE FROG. 237

eye, pin it to a piece of loaded cork, with the corneal
surface upwards.

a.

Notice the more opaque coat (sclerotic), with
which the margin of the cornea is continuous, and
which forms the outer envelope of the eye-ball on
its sides and back. In some parts the sclerotic
is semi-transparent and allows the pigmented
choroid coat (8. g) to be more or less distinctly
seen through it.

Prick the cornea with the point of a sharp scalpel,
taking care not to injure the iris; note the clear
aqueous humour which spirts out, the cornea at the
same time collapsing.

Seize the cut edge of the cornea with a fine pair
of forceps and, with sharp scissors, carefully cut
through it all round at the line of junction with
the sclerotic. The convex anterior surface of the
transparent crystalline lens will now be seen pro-
jecting through the pupil.
Place the cork in a vessel of convenient size and
add enough water to cover the eye. Then, with
sharp scissors, cut away the iris, and so expose all
the anterior surface of the lens. Passing the point
of a scalpel under one edge of the lens, gently tilt
it out and examine it.
The crystalline lens of the frog is nearly sphe-
rical but somewhat thicker from side to side
than antero-posteriorly. Its anterior surface
(that which projects into the pupil) is also less
convex than its posterior surface.

The cavity of the posterior chamber of the eye is
now exposed. It is filled with a gelatinous trans-
parent mass, the vitreous humour, which can be seen

238

1,

ELEMENTARY BIOLOGY. [XIiI.

if the water, in which the eye is being dissected,
be poured away.

Lining the posterior chamber of the eye is the
retina, which, from the action of the water, will
probably now be somewhat cloudy: in the un-
altered state it is perfectly transparent, allow-
ing the choroid (3. g) to be seen through it.
With the point of a microscope needle gently
raise the retina from the black membrane (cho-
roid) beneath it. It will be found that this can
be readily done except at one point (answering to
the blind spot of our own eyes), which, by turning
the eye-ball over will be seen to be opposite the
point of entrance of the optic nerve (2. @).

The choroid coat of the eye-ball is now exposed.
It is a dark pigmented membrane, of loose floccu-
lent texture, which can be readily detached, by
needles, from the sclerotic which lies outside it.

b. The Kar.
The frog has no external ear, its tympanic membrane,
as already mentioned (A. 2. a), being exposed on each
side of the head.

a.

Note the arrangement of the tympanic mem-
brane: it is smoothly stretched over a hard ring.

Dissect away the outer or integumentary layer of
the tympanic membrane. Beneath it will be
found a transparent membrane, formed by the
fibrous and mucous layers, with an opaque white
patch about its middle.

Cut through these layers of the tympanic mem-
brane along their margins: the tympanic cavity
will then be laid open.

X11.]

THE FROG. 239

The tympanum of the frog is a funnel-shaped
cavity with its wider end turned outwards, Its
sides are bounded by a smooth slightly pig-
mented mucous membrane, continuous with

that of the mouth through the Eustachian
recess,

In its roof lies a rod, ossified in the middle,
cartilaginous at each end, which is the columella
auris. The columella is attached, by its inner
end, to the upper and anterior part of the
inner wall of the tympanum and, by its outer
end, to the middle layer of the tympanic
membrane, in the region of the opaque patch
mentioned above (1. b).

Close to the inner attachment of the columella
there is a comparatively large oval opening in
the wall of the tympanic cavity; this is the
outer end of the Eustachian recess, the inner
end of which has been already (B.11.a) seen
on the posterior part of the roof of the mouth.
Pass a probe through the opening now exposed,
and open the frog’s mouth to see its passage
into that cavity.

2. The internal ear.

a

Carefully dissect away the columella auris from
its inner attachment. An aperture into which it
was inserted will thus be exposed: this is the
fenestra ovals.

Take a pair of scissors and cut through the bones
of the side of the skull in a line joining the
fenestra ovalis and the “guard” of the para-

240

ELEMENTARY BIOLOGY. [XIIT.

sphenoid bone (D. c, 3. a); the chamber in the
prootic bone (D. ¢, 1. d) which is thus exposed
contains part of the internal ear.

c. The dissection of the internal ear of the frog
is difficult, on account of its minuteness. But
by carefully removing the bony and cartilagi-
nous walls of the periotic capsule, piecemeal,
the semicircular canals will be exposed and the
whole membranous labyrinth may be extracted.
It should be placed in a watch-glass containing
salt solution or spirit, and its form studied under
the simple microscope.

c. The olfactory organs,

These consist of two chambers which open externally,
near the end of the snout, by the anterior nares, and
posteriorly into the mouth, just behind the vomerine
teeth by the posterior nares. Make out these open-
ings.

a. Take a frog which has been preserved in spirit
and pass the point of a small pair of scissors into
the external nostril of one side and cut away the
roof of the nasal cavity. A chamber is thus ex-
posed which has a somewhat triangular form, the
apex of the triangle being at the external nostril
and the posterior nostril being at another angle
and farther from the middle line.

b. The walls of the cavity are slightly folded, and
there is a well-marked hemispherical eminence on
its floor.

c. Open the other nasal cavity in a similar way:
notice the boundary wall (septum narium) which
lies between the two and completely separates
them.

xut.]

THE FROG, 241

Open the nasal cavity of a frog which has been pre-
served in Miiller’s fluid ; gently scrape away a little of
the epithelium lining the chamber, mount in water:
examine with your highest power.

Among numerous mutilated cells, a certain numbor
of more or less perfect ones will be found: these
are of two kinds, viz. large columnar epithelial cells
(J. 1. 6), each with an oval nucleus, an unbranched
peripheral process and a branched deeper one;
and smaller cells, with less protoplasm around the
nucleus and finer peripheral and central processes.

d. The gustatory organ.

1.

The shape and arrangement of the frog’s tongue have
already been described (B. 11. a).

a,

Snip off a bit of mucous membrane from the
upper surface of the tongue of a recently killed
frog, mount in normal saline solution and cover
in plenty of the fluid with a large coverslip: ex-
amine with one inch obj.

On the surface of the fragment and especially
around its edges numerous minute elevations
of the surface will be seen: these are the pa-
pille: some (filiform papille) are pointed at
the free end and others (fungiform papille)
flattened. Note the loops which the blood ca-
pillaries make in some of the papille.

Examine one of the thinner bits of the speci-

men with a higher power: the papille will be

seen to be covered by epithelium, which is for

the most part ciliated (J. 1.¢); some ‘of the

papille however will be seen to have no cilia

except a narrow belt around the somewhat
16

bo
bo

ELEMENTARY BIOLOGY. [XIIL.

truncated apex; it is on these latter papille
that the gustatory disks are placed, and in for-
tunate specimens nerve-fibres can be seen en-
tering them.

SOME OF THE MORE IMPORTANT POINTS IN THE HISTO-
LOGY OF THE FRoG.

a. Epithelium.

This consists of cells which line free surfaces within
the body: the epidermis covering the skin is a similar
structure, and is continuous with epithelium at the
apertures of the body. There are several main types
of epithelium, viz.—

a.

Scaly epithelium. Open the abdomen of a re-
cently killed frog, carefully remove the viscera
and lay bare the lymph sinus at the back of the
body-cavity. Cut away its thin wall as carefully
as possible, taking great care not to drag or pull
it. Place the fragment in 0°52 solution of silver
nitrate for about three minutes: then remove,
wash well in distilled water, and finally leave the
specimen in distilled water and exposed to the
sunlight. So soon as the bit of pleuroperitoneum
has become of a well-marked brown colour, mount
it in glycerine and examine with a high power.

It will be seen to be covered on both sides with
flat closely fitting cells, the boundary lines of
which are stained black by the silver ; accord-
ing to the amount of staining a nucleus may or
may not be rendered conspicuous in each cell.
Here then, in good specimens, rings of
smaller and more deeply stained cells will be
seen surrounding minute apertures (stomata).

XIII. ] THE FROG. 243

b. Columnar epithelium. Scrape gently the inner
surface of the mucous membrane of the intestine
of a frog which has been preserved in Miiller’s
fluid; mount the detached fragments in water
and examine with a high power.

a. Numerous elongated cells, flat at one end and
somewhat pointed at the other, will be seen.
Each has a well-marked oval nucleus.

8. These cells may be seen zm stfu if a thin section
of the mucous membrane of the intestine or
stomach be examined. They are closely ap-
plied and arranged in a single layer.

c. Ctliated epithehum. Snip off a bit of the mucous
membrane from the tongue of a recently killed
frog with a sharp pair of scissors: mount the
bit in 0°75 sol. of sodic chloride, avoiding pres-
sure, and examine with a high microscopic power.

a. Note the shimmering appearance along its free
edge, produced by the rapidly moving cilia; as
the cilia begin to die and their movement
slackens, individual ones can be seen.

8. Scrape gently, with a scalpel, one of the pro-
minences in the roof of the frog’s mouth beneath
the eye-balls: mount the scrapings in 0°75 salt
solution and examine with 4 objective for in-
dividual ciliated cells; note their roundish form,
granular protoplasm and nucleus, and the group
of cilia borne on one end; stain with iodine.

b. Cartilage.

1. Dissect out carefully the omosternal or xiphisternal
cartilage of a recently killed frog; mount in 0°752
sodic chloride solution and examine with 4 or 4 obj.

16—2

“CC.

ELEMENTARY BIOLOGY. [xut.

Large roundish granular cartilage-cells will be
seen imbedded in a structureless or very finely
granular matrix, which is more refractive next
the cells than elsewhere, and causes the appear-
ance of a sort of halo round each.

In each cell lies a distinct granular round
nucleus or sometimes two nuclei, containing
large highly refractive molecules.

If the preparation be carefully made, each cell
will at first completely fill the cavity of the
matrix in which it lies, but if it be kept some
time or be treated with distilled water the cells
contract and so leave a transparent ring between
their surface and the inside of the cavity in
which each lies,

Examine a transverse section of hard bone (say

a bit of the shaft of the humerus or femur) with

1 inch obj.

The Haversian canals: round or oval spaces,
usually filled with dirt in grinding down the
bone, and therefore black and opaque, but
sometimes cléar and empty.

The lamelle : a series of concentric layers round
each Haversian canal.

The lacune: oval black spots between the
lamelle.

The canaliculi : minute black lines seen radiat-'
ing from the lacune,

XIII |

1.

THE FROG. 245

Besides the lamelle above mentioned others
will be seen which belong to no Haversian
system, but either fit in the angles between the
systems, or run around the outer surface of the
bone.

Examine with 4 obj. Observe the lacune and
canaliculi more accurately.

Examine in water or glycerine a thin transverse
section of a long bone which has been softened by
dilute acid.

The Haversian canals empty or containing a
granular mass.

The lamella: very indistinct.
The lacune seen as transparent oval spaces.
The canaliculi transparent and almost invisible.

Examine sections of softened bone which have
been stained with carmine: in each lacuna will be
found a stained mass of protoplasm.

Examine longitudinal sections of the femur or
humerus: the Haversian canals are seen to be
channels running for the most part in the long
axis of the bone, but communicating with one
another frequently by cross branches. The
lacune, &c. appear much as in the transverse
section.

d. Connective tissue.

Of this there are two main varieties, viz—

White fibrous tissue. This occurs nearly pure in °
tendons, but is widely distributed throughout the

246 ELEMENTARY BIOLOGY. [XIII

body, mixed with other tissues. Tease out a bit
of fresh tendon in water: examine with a high
power.

a. It is chiefly made up of very fine wavy fibres
which run in bundles parallel to one another;

they have an ill-defined outline and do not
branch.

8. Treat with dilute acetic acid. Most of the
fibres disappear, but a few well defined curled
fibres (yellow elastic fibres, see b} remain. Be-
sides these some elongated granular proto-
plasmic masses are brought into view (con-
nective-tissue corpuscles).

b. Yellow elastic tissue. This does not occur in large
collections, in the pure form, in the frog; although
mixed with white fibrous and other tissues, it is
very widely distributed.

a Tease out in acetic acid some of the bands of
tissue beneath the frog’s skin; examine with
a high power. Numerous fine well-defined
. branched fibres, running in bold curves, will be
seen: these are yellow elastic fibres, as the
acetic acid (a. 8) destroys the white fibrous
tissue.

e. Striped muscle.

a. Tease out gently a bit of muscle which has been
kept in alcohol, and examine with 1 inch obj.

a. Composed of elongated fibres, which exhibit
a tendency to split up into finer filaments

( fibrille).

XIII]

b.

C.

Y-

THE FROG. QAT

Examine with high power.

The alternate lighter and darker bands placed
transversely to the long axis of the fibre
(transverse striation).

The fine structureless membrane (sarcolemma)
enveloping the fibre: seen here and there as
a delicate film where the fibre is twisted or
bruised.

The tendency to split up into fibrille.

Tease out a bit of fresh muscle in 0°75 % sodic
chloride solution.

The transverse striation of the fibres: less dis-
tinct than in the muscle from alcohol.

The absence of a tendency to split up into
fibrille.

The sarcolemma, which may be seen at points
where the continuity of its contents has been
interrupted by pressure, twisting, &c.

Treat with acetic acid: the striation rendered
very indistinct; oval nuclei made apparent
here and there in the fibre.

f. Nerve-fibres.

1. Tease out a bit of fresh nerve in 0°752 sodic
chloride. Examine with a high power.

a.

Composed of well-defined fibres (white nerve-
fibres) mixed with white fibrous tissue (d. 1. a).

The appearance of the nerve-fibres: each has
a double contour, marked out by a curdled-
looking highly refractive border on each side.

ELEMENTARY BIOLOGY. [ XU:

c. The structure of the nerve-fibres.

a. The delicate structureless investing mem-
brane (primitive sheath); look for it on bruised
nerve-fibres or at the ends of torn fibres.

B. The highly refractive border (medullary sheath)
within the primitive sheath.

y. The central homogeneous axis (axis cylinder) ;
look for it projecting beyond the medullary
sheath of torn fibres.

d. Treat a fresh bit of teased-out nerve with chloro-
form: the medullary sheath will be dissolved out,
and the axis cylinder plainly seen.

g. Nerve-cells.

Take a sympathetic ganglion from a recently killed
frog: dissect out in normal saline solution and ex-
amine with 4 obj.

a. Among the pigment-cells, which are clustered
around the ganglion, will be seen numerous
large pale granular cells, each possessing a con-
spicuous clear round nucleus with a distinct
nucleolus.

8. Tease out in glycerine a Gasserian ganglion
from a frog’s head which has been preserved in
Miiller’s fluid or chromic acid. Cells like those
described above will be found.

ry. Examine sections of spinal cord which have
been stained with carmine or hematoxylin,
and note the large branched nucleated cells in
the grey matter especially towards the ventral
side of the cord,

XII]

THE FROG. 249

h. The retina.

1. Sufficiently satisfactory specimens of this organ can
be obtained as follows. Take perfectly fresh eyes from
a frog, prick the corneas in two or three places, and
lay the eyes aside for three or four days in 0°252
chromic acid solution: then transfer them to alcohol
and keep them in it until wanted.

a.

Carefully cut open an eye preserved in the
above method and expose the retina: trans-
fer the latter to a glass slide, and with a razor
chop down on it so as to cut off a number of
slices: add glycerine, put on a cover, and examine
with a low power. Some of the bits will be found
thin enough for further examination.

With the low power little can be seen but that
the retina is composed of a number of different
layers, some of which appear less opaque than the
others.

Put on a high power and examine, make out the
following points—

The internal limiting membrane, a thin struc-
tureless layer.

The nerve-fibre layer: thin and granular.

[Both a and f are often difficult to make out in
retinas prepared as above.]

The nerve-cell layer: composed mainly of cells
like those described above (g.1. a), but rather
smaller than those from the sympathetic ganglia.
From some, branches can be traced into the
next layer.

250

ELEMENTARY BIOLOGY. [ XIII.

The molecular layer: this is thicker than any
of the preceding, and has a finely punctated ap-
pearance: running through it the fibres of
Miiller (h, 1. «) are very plainly seen.

The inner granular layer: this is the layer
which usually looks clearest in sections, its ele-
ments being less closely packed than those of
the other layers, It is made up of a number
of nuclei (which in chromic-acid specimens look
granular), around which is collected a very small
amount of protoplasm, and of fine fibres, some
of which can be traced joining the nuclei or
granules.

The inter-granular (fenestrated) layer. A narrow
cloudy layer in which no definite structural
elements are visible.

The outer granular layer. Much thinner than
the inner granular layer and more closely
packed. It is composed of distinct fibres (rod-
and cone-fibres), each of which swells out and
has a nucleus (the granule) developed 1 in the
enlargement.

The external limiting membrane. A thin homo-
geneous layer like a.

The fibres of Miiller. These are highly refract-
ing fibres which can be traced with ease from
the internal limiting membrane to the fenes-
trated layer. They probably rum beyond the
latter and end on the external limiting mem-
brane, but are difficult to trace through the
outer granular layer.

XIIL |

i.

THE FROG. 251

x. The rod- and cone-layer. The main thing
which will be noted here is the huge rods for
the most part distorted by the treatment
to which the retina ‘has been exposed. In
favourable bits it can be seen that each rod is
divided transversely into an inner and an outer
segment. The cones are few and small, and
generally completely concealed by the rods.

d. Take a fresh frog’s eye: prick its cornea and col-
lect the aqueous humour on a slide. Then open
the eye, remove a bit of the retina and tease it
out in the aqueous humour, mount and examine
with a high power.

a. Numerous rods will be seen floating about,
many broken but some intact and shewing the
boundary line between their two segments very
plainly. At first both segments are homoge-
neous, but very soon they begin to alter; the
outer layer frequently then getting a trans-
versely striated appearance and shewing a
tendency to split up into corresponding pieces :
gradually these rods entirely disintegrate, first
curling up, swelling out, &e.

The skin.

Cut out a piece of skin from the back of the thigh of

a recently killed frog: spread it out in water, cover,

and examine with a low power: note—

a. The pigment cells; seen as black irregularly
shaped patches; some compact, others more or
less branched.

b. The mouths of the cutaneous glands; seen as
clear round spots, although their openings are
really triradiate : their number.

bo
Lo

ELEMENTARY BIOLOGY. [xu

Take a piece of skin that has lain for a day or two in
solution of ammonia bichromate and then in alcohol:
imbed it, and cut sections perpendicular to its sur-
faces: mount in glycerine. Examine with a low
power; note—

a

The two layers of the skin, dermts and epidermis,
the former being much the thicker: note in the
dermis its deeper connective-tissue layer, and its
more superficial glandular layer immediately
beneath the epidermis.

Examine with a higher power.

The epidermis is seen to be made up of nume-
rous closely packed cells, arranged in several
layers.

The deepest epidermic cells are granular, nu-
cleated, and somewhat oval, with their long
axes at right angles to the surface.

Then come several rows of cells, also granular
and nucleated, but becoming smaller and
rounder as they become more superficial.

The most superficial three or four layers of
cells are flattened parallel to the surface, are
not granular, and possess no apparent nucleus,

Here and there a pigment-cell is seen among
the epidermic cells, and some of the latter con-
tains a few pigment-granules.

The dermis, consisting fundamentally of white
fibrous and elastic tissues: its glandular and
non-glandular layers.

XiIL.]

3.

THE FROG. 253

m. Immediately beneath the epidermis is a thin
stratum of connective tissue in which lie many
large pigment-cells, sometimes forming an
almost continuous layer.

6. Then come a large number of round cavities,
the cutaneous glands, lined by large, pale,
slightly granular, nucleated cells, which are
columnar when seen sidewise, but polygonal
when seen from the base or apex. Sometimes
the duct of the gland can be traced running
from it through the epidermis. Separating the
glands and supporting the epithelium are
bundles of connective tissue, consisting mainly
of fibres running perpendicularly to the sur-
face.

t. The deepest layer of the dermis is made up of
connective-tissue bundles, running for the most
part parallel to the surface.

The kidney.

Take a frog’s kidney which has been for a week in
solution of bichromate of potash, and then for a day
or two in spirit. Imbed it, cut sections parallel to its
flatter surfaces, and mount in glycerine.

a. Examine with a low power.

a. Note the numerous tubules of which the organ
is mainly composed and which twist about in
all directions, and are consequently cut, some
transversely, some obliquely, and others more
or less longitudinally. The absence of any
marked division into cortex and medulla.

254

1.

ELEMENTARY BIOLOGY. [sem

The clear round holes, scattered about; these
are sections of glomeruli from which the con-
tained vessels have fallen out. Some may be
seen in which a granular mass still lies.

Examine with a higher power—

The epitheliwm lining the tubules, composed in
some of granular and ill-defined cells, in other
(usually larger) tubules of clearer and better
defined cells; both varieties are nucleated.

Examine specimens of injected kidney with a
low power. Note the vascular tufts of the
glomeruli.

k. The testis.

Imbed a testis which has been hardened in alcohol:
cut sections and mount in glycerine.

Examine with a low power.

The organ is chiefly made up of tortuous
tubules, which are seen cut in various direc-
tions.

Examine with a high power.

Note the epithelium lining the tubules: it
varies with the season of the year (whether
before or after the breeding time), and is
usually extremely granular and _ ill-defined.
The cells are arranged in two or three rows,
and at the time of breeding the most superfi-
cial layer of cells is transformed into sperma-
tozoa, each cell giving rise to several. These
lie side by side at right angles to the lumen of

NIG |

THE FROG. 255

the tubule, which accordingly appears to be
lined by them.

c. The spermatozoa (B. 10, a. ¥).

1, The ovary.

The structure of this organ is easiest made out shortly
after the breeding time. Remove one of the ovaries,
place it in water, and make an incision into it: it will
be seen to contain a cavity, and projecting upon the
walls of this cavity and also upon the outer surface of
the ovary are numerous round eminences of various
sizes: these are ova in difterent stages of development,
and the large ones will be seen to have become more
or less pigmented.

Tease out a bit of ovary in normal saline solution:
cover, and examine with a low power.

a. Note the ova, many much smaller than those
which were seen (1) with the naked eye: they
appear as granular spherical masses with a clearer
central patch.

b. Examine with a high power a portion of your
specimen containing some of the younger and
more transparent ova. Note—

g. The thin structureless membrane, wtelline mem-
brane, enveloping each.

B. The granular matter (yelk, vitellus) forming
most of the ovum. It sometimes appears to
be composed of an outer granular and an inner

clearer layer.

K.

ELEMENTARY BIOLOGY. [xu

y. The clearer central mass (germinal vesicle)
imbedded in the vitellus. The large number
of highly refracting masses (germinal spots)
within the germinal vesicle.

THE PHYSIOLOGICAL PROPERTIES OF MUSCLE AND NERVE,

Place a frog under a beaker, with a drop or two of
chloroform: take it out immediately it becomes uncon-
scious, which will probably be in a few seconds. Now
feel with a finger-nail for the depression beneath the
skin at the back of the animal’s head, which indicates
the point of articulation of skull and spinal column: it
lies in a line joining the posterior borders of the two
tympanic membranes. Divide the skin and muscles at
this point until the neural canal is laid open, and then
pass a stout wire into the cranium and down the neural
canal of the vertebral column. By this process (known
as pithing) the frog is rendered totally incapable of
further consciousness, though most of its tissues will
retain their vitality for some time.

a. Remove the skin from one leg, so as to lay bare
the muscles: send an interrupted electric current
through any one of them (or tap the muscle
sharply with the back of a scalpel): it will
immediately contract, or alter its form in a
definite way ; it becomes shorter and thicker, and
in so doing moves the bones to which it is
attached.

b. Very carefully lay bare the sciatic nerve, taking
care not to crush or drag it: divide it as high up
as possible and, seizing it with a pair of forceps
close to its cut end, lay it over the electrodes of
an induction-coil, Probably when the nerve is

XIII. |

THE FROG. 257

cut the muscles of the limb will contract: whether
or not, however, they will contract violently while
the interrupted current is going through the
nerve.

[If an induction-coil is not at hand a bit of clean
copper wire twisted round a strip of zinc, with the
points of contact moistened with dilute acetic acid,
may be used to stimulate the nerve; smart tapping
or pinching with a pair of forceps will also excite it,
but by such means the nerve is soon killed.]

The above experiments shew :—

Cc.

That the muscle is irritable and contractile: cer-
tain external agencies (stimulc) excite some
change in it, the result of which is a muscular
contraction.

The nerve is irritable: certain external agencies
excite some change in it, which in this particular
case manifests itself by a contraction of the
muscles connected with the nerve.

The nerve possesses conductivity: although it is
stimulated at some distance from the muscles,
yet the change excited by the stimulus travels
along it to them.

17

APPENDIX.

The various re-agents, mentioned in the “Laboratory work”
in the preceding pages, are prepared as follows :

ul

Acetic acid, Dilute.

Mix 1 cub. centimetre of glacial acetic acid with 99 cub.
cent. of distilled water.

Ammonic bichromate, Solution of.

Dissolve 10 grammes of crystallized ammonic bichromate in
a litre of distilled water.

Carmine, Solution of.

Carmine ssiees aieatosweiidercortods 2 grammes.
Strong solution of ammonia ...... 4 cub. cent.
Distilled water ........... Ja oay aera 48 cub. cent.

Dissolve the carmine in the ammonia and water ; leave in
an unstoppered bottle until nearly all smell of ammonia has
gone. Afterwards keep in a well-closed bottle. Dilute a
snall quantity with fifteen or twenty times its bulk of
water, when required for use.

Chromic acid, Solution of.

Dissolve 10 grammes of crystals of chromic acid in one
litre of water. This gives a 1 per cent. solution, from which
weaker ones can readily be prepared when required.

Or

10.

11.

APPENDIX. 259

Hematoxylin, Solution of. a

a, Prepare a saturated solution of crystallized calcic

chloride in 70 per cent. alcohol; then add alum to
saturation.

b. Prepare a saturated solution of alum in 70 per cent.
alcohol. Add 1 volume of a to 8 of b.

ce, To the mixture of a and b add a few drops of a

saturated solution of pure hematoxylin in absolute
alcohol. Filter.

Iodine, Solution of.

Prepare a saturated solution of potassic iodide in distilled
water ; saturate this solution with iodine. Filter. Dilute
to a brown sherry colour,
Magenta, Solution of.

Dissolve 1 decigr. of crystallized magenta (roseine) in 160
cubic centimetres of distilled water: add 1 cub. cent. of
absolute alcohol. Keep in a well-closed bottle.

Mayer’s Solution.
See note, p. 8.

Muller’s Solution.

Bichromate of potash ............... 25 grammes.
Bodice sulphate vciccencav cos cae ceceee 10 grammes,
Distilled water ...........0.:cccseee ees 1 litre.

Osmic Acid, Solution of.
Best bought ready made in the form of 1 per cent. solution.

Paraffin.

Melt together one part of solid paraffin (paraffin candles
will do), one part of paraffin oil and one part of pig’s lard.
A mixture in the above proportions gives, when it has
cooled, a mass of the most generally useful consistency.

17—2

4

260

13.

14.

16.

APPENDIX,

To imbed an object, scoop a hole in a bit of the paraffin,
place the object (the surface of which must be dry) in this
hole and fill up the latter with some melted paraffin,

Pasteur’s Solution. 7
See note, p. 6.

Potash Solution.

Dissolve 5 grammes of potassic hydrate in 100 cubic cent.
of water.

Schultz’ Solution.

Dissolve some zinc in hydrochloric acid; permit the solution
to evaporate, in contact with metallic zine until it has
attained a syrupy consistence. Saturate the syrup with
potassic iodide, and then add enough iodine to make a dark
sherry-coloured solution. The object to be stained must
be placed in a little water, and then some of the above
solution added,

Silver nitrate, Solution of.

Dissolve 0-5 grammes of silver nitrate in 100 cubic
cent. of distilled water. Keep in an opaque stoppered
bottle.

Sodic Chloride, Solution of. (Normal saline solution.

Salt solution.)

Dissolve 7'5 grammes of sodic chloride in 1 litre of dis-
tilled water.

Per Cen, renders fone [ps Gece

‘y ; L / ee [eran
Hata ¢ Wu CA ne ¢ 64, yj = Clreu/ a 6 eg)

INDEX.

A.

ABDUCENTES, nervi, 181.

Acetabulum, 251.

Acrogenous growth, 46.

Adductor muscles, 105, 112, 119.

Ale, 46.

Alcoholic fermentation, 5, 9, Io.

Algae, 46.

Alimentary canal, of Anodon, 106,
18; of Crayfish, 126, 1423; of
Frog, 160, 165, 195; of Lobster,
126, 1423 of Tadpole, 156.

Alinasal process, 163.

Alternation of generations, 35, 46, 60.

Ambulatory limbs, 124, 145.

Ameba, 17; Laboratory work, 21.

Amceboid movements, 20, 102.

Anacharis, protoplasmic movements
in, 53.

Anguln oplenial, 211.

Annulus, 65.

Anodonta cygnea, 104; Laboratory
work, 110.

Antenne, 125, 147.

Antennules, 125, 147.

Anterior commissure, 178.

Anterior abdominal vein, 172, 192,
225.

Anther, 68, 82.

Antheridium, 42, 44, 51, 59, 66.

Antherozooids, 45, 49, 59, 66.

Aortic arches, 169, 195, 228.

Appendages, of Bean, 68, 76; of
Chara, 41, 47; of Crayfish, 123,
136, 145; of Frog, 153, 189, 203;
of Lobster, 123, 136, 145.

Aqueous humor, 237.

Arachnoid membrane, 160.

Archegonia, 59, 66.

Arterial system, of Anodon, 107; of

“Bell- Animalcule, 86;

Crayfish, 128, 139, 143; of Frog,
170, 228; of, Lobster, 128, 139,
143.

Artery, cceliac, 170, cceliaco-mesen-
teric, 170, 2293 cutaneous, 170;
femoral, £70, 229; hypogastric,
170, 229; iliac, 170, 229; lingual,
170, 228; mesenteric, 170; ceso-
phageal, 170; pulmocutaneous, 169
195, 222; pulmonary, 169, 170;
subclavian, 170; vertebral, 170.

Articular process, 204.

Arytenoid cartilages, 173.

Asci, 34.

Ascospores, 8, 34, 40.

Astacus fluviatdis, 122; Laboratory
work, 134.

Astragalus, 216.

Atlas vertebra, 204.

Atrium, 167, 193.

Auditorii, nervi, 182.

Auditory organs, of Anodon, rog, 117;
of Crayfish, 133, 149; of Frog, 186,
238; of Lobster, 133, 149.

Axillary vein, 227.

Axis cylinder, 248.

B.

Bacillus, 28.

Bacteria, 24; Laboratory work, 26.

Balantidium, 89.

Bark, 70.

Basipodite, 145.

Bast cells, 63, 64, 71.

Bean plant, 68; Laboratory work,
76.

Laboratory
work, go.

Blood, of Anodon, 108; of Frog, 167,
202; of Lobster, 124.

262

Blood corpuscles, coloured, 202; colour-
less, 19, 23, 108, 129, 166, 167, 203.

Body cavity, of Hydra, 96, Ico.

Bojanus, organs of, 107.

Biachial, plexus, 184; vein, 171, 2273
nerve, 235.

Bracken Fern, 54; Laboratory work,
61.

Brain, 177, 230.

Branchio-cardiac veins, 129.

Branchiostegite, 123, 138.

Browspot, 187.

Bud, terminal, of Chara, 42, 48. |

Buds, 68.

Eyssus, 110, 121.
Cc.

CALCANEUM, 216.

Calear, 554, 217.

Calyx, 68, 81.

Cambium, 70, 78, 79.

Campanula medium, 85.

Canalis centralis, 184, 233.

Carapace, 123, 134.

Carchesium, 94.

Carina, 82.

Carotid, artery, 169, 170, 195, 2283
gland, 228.

Capitulum, 44.

Carpopodite, 145.

Carpus, 214.

Cartilage, 162, 243.

Cerebellum, 177, 231.

Cerebral hemispheres, 177, 230.

Cerebro-spinal, axis, 1600 ; nervous sys-
tem, 177.

Cephalic flexure, 124.

Cephalic ganglia, 108, 116.

Cephalo-thorax, 123, 134, 137.

Cervical groove, 124.

Cervical suture, 123, 134.

Chara, 41; Laboratory work, 47.

Chel, 124, 146.

Chiasma, optic, 232.

Chlorophyll, 11, 44, 48, 73, 97, 100.

Chondro-cranium, 162.

Choroid, coat, 238; plexus, 177.

Cilia, of Anodon, 116; of anthero-
zooids, 45, 51, 59, 66; of Bell-
animalcule, 87, 92; of the Frog,
243; of Hydra, 96, 102; of Proto-
coccus, 12-153 of Spirillum volu-
tans, 24.

INDEX,

Circulatory organs, of Anodon, 108,
113; of Crayfish, 127, 139; of Frog,
166, 193, 2253 of Lobster, 127, 139.

Clavicle, 213.

Cloaca, of Anodon, 106, 112; of Frog,
160, 197.

Clubniosses, 72.

Cochlea, 186.

Coeliac artery, 170.

Coeliaco-mesenteric artery, 170, 229.

Colon, 165.

Columella, 33

Columella auris, 186, 208, 239.

Colourless blood-corpuscles, 19, 23,
108, 129, 166, 167, 203.

Cotyledon, 69, 84.

Conidia, 31, 38.

Conidiophores, 38.

Conifers, 72.

Conjugation, 35, 89, 93.

Connective rod, 132, 148.

Connective tissue, 161, 245.

Contractile vesicle, 18, 21, 88, 91,

Coracoid, 213.

Cornea, 132, 236.

Corolla, 68, 81, 82.

Corpus adiposum, 190, 196.

Corpuscula, 72.

Cortical layer, of Chara, 41; of Bell:
animalcule, gr.

Cothurnia, 94.

Coxopodite, 145.

Cranial nerves, 179.

Crura cerebri, 178, 233.

Crural nerve, 184.

Crystalline lens, 132, 148, 237.

Cutaneous glands, 252; artery, 170.

D.

DACTYLOPODITE, 145.

Dentary bone, 211.

Dermis, 252.

Development, of Anodon, 10g; of
Bean, 69; of Chara, 45, 49; of
Crayfish, 133; of Fern, 59; of Frog,
155; of Lobster, 133; of Mucor,
33, 36; of Penicillium, 31, 38, 39.

Diaphragm, 159.

Dorsal avrta, 170, 229.

Dorso-lumbar vein, 172,

Dotted ducts, 78.

Duodenum, 165,

INDEX.

E.

Far, see Auditory organ.

Ectysis, 134.

Ectoderm; 7, 100.

Ectosare, 18, 21.

Embryo, of Anodon, Tog, 121; of
Bean, 69, 84; of Chara, 45; of
Fern, 59; of Frog, 155; of Lob-
ster, 133.

ee cell, 59, 69, 83; sac, 69, 83,

BS

Encephalon, 177, 230.

Encystation, of Amba, 19 ; of Vor-
ticella, 89, 93.

Endoderm, 97, 100.

Endogenous cell division, 4.

Endoplast, 89.

Endopodite, 125, 136.

Endosare, 21.

Endoskeleton, 161, 203.

Endosperm, 69, 83.

Endosporium, 35.

Epicoracoid, 213.

Epidermis, of Bean, 70, 77, 80; of
Fern. 55, 57, 61; of Frog, 252.

Epithelium, 242.

Epistylis, 94.

Eustachian recesses, 139, 188, 239.

Evening Primrose, 84.

Exoccipital, 208.

Exogens, 71.

Exopodite, 125, 136.

Exoskeleton, of Anodon, 110, 1203 of
Crayfish, 122, 134; of Frog, 161;
of Lobster, 132, 134.

Exosporium, 35.

Eye, of Crayfish, 132, 147; of Frog,
185, 235; of Lobster, 132, 147.

Eyestalks, 125, 147.

F,

Facta.is, nervus, 182.

Femoral artery, 170, 229; vein, 171.

Fenestra ovalis, 187, 208, 239.

Fermentation, alcoholic, 1, 5, 9, 10;
putrefactive, 25.

Fertil‘za’ ion, process of,in Anodon, 109;
in Bean, 59; in Chara, 45; in Fern,
59; in Frog, 155; in Hydra, 97.

Fibro-vascular bundles, 56, 62, 70, 78,

Fibula, 216.

263

Filament, 82.

Filum terminale, 183.

Fission, 89, 93, 96.

Flower, of Bean, 68, 81.

Fontanelle, 162.

Foot, of Anodon, 104, 112.

Foramen of Munro, 178.

Foramen magnum, 208.

Fourth ventricle, 177, 231.

Fresh water, Crayfish, 122; Labora-
tory work, 134; Mussel, 104; Labo-
ratory work, tro; Polypes, 95; La-
boratory work, 99.

Frog, 153; Laboratory work, 188.

Fronds, 54, 57, 95.

Fungi, 30.

Funiculus, 84.

G

Gastric skeleton of Crayfish, 126,
143.

Gastric vein, 172, 226.

Gasserian ganglion, 180, 248.

Gemmation, 4, 11, 15, 89, 96.

Generative organs, see Sexual organs,

Genito-urinary canal, 198.

Germinal, spot, 103, 176, 255; vesi-
cle, 103, 176, 255.

Gills, of Crayfish, 130, 139 ; of Lobster,
130, 139; of Tadpole, 156,

Girdle Lone, 209.

Glenoid fossa, 212.

Glochidium, tog.

Glossopharyngeus, nervus, 182, 234,

Glottis, 159, 173, 189, 199.

Green gland, 131, 144.

Gustatory disks, 242; organ, 187, 241.

H.

Harderian gland, 186.

Hay infusion, 27.

Heat stiffening, 19, 22, 23.

Heart, of Anodon, 107, 113; of Cray;
fish, 127, 139; of Frog, 167, 193;
of Lobster, 127, £39.

Histology, of Anodon, 113, 119, 120;
of Bean, 70, 77, 80; of Blood, 23,
202; of Bracken Fern, 55, 61; of
Chara, 42, 47; of Crayfish, 138,
143, 144, 147, 149; of Frog, 196,
197, 241, 242; of Hydra, 97, 101;
of Lobster, 131, 143, 144, 147,

264

149; of Mucor, 32, 39; of Penicil-
lium, 30, 37.

Homarus vulgaris, 112; Laboratory
work, 134.

Humerus, 213.

Humor, aqueous 237; vitreous, 238.

Hydra fusca and H. viridis, 95; La-
boratory work, 99.

Hyoid bone, 159, 211.

Hyphe, 30, 33, 37) 39-

Hypogastric artery, 170, 229.

Hypoglossal nerve, 195, 234+

I.

ILEuM, 165.

Iliac arteries, 170, 229; vein, 172.

Tlium, 215.

Inert layer, 201.

Infundibulum, 178.

Infusoria, 86.

Iunominate vein, 171, 227.

Integument, of Frog, 187, 251.

Inspiration, 174.

Intercellular passages, 58, 80.

Internal ear, 186, 239.

Internodes, 41, 47, 54, 61, 68.

Inter-ocular gland, 187.

Intervertebral foramina, 206.

Intestine, of Anodon, 106, 1183 of
Crayfish, 126, 142; of Frog, 160,
165, 196; of Looster, 126, 1423 of
Tadpole, 156.

Tris, 236.

Irritability, muscular, 257.

Ischiopodite, 145.

Ischium, 215.

J.

JUGULAR vein, external 171, 2263; in-
ternal, 171, 227. :

K.
KIDNEYS, 175, 198, 253.

L.

LaBiat palpi, 105, 112.

Laboratory work, Ameeba, 21 ; Anodon,
110; Bacteria, 26; Bean, 76; Bell-
animaleule, go; Bracken Fern,
61; Chara, 47; Crayfish, 134;
Frog, 188; Hydra, 99; Lobster,

INDEX.

134; Mucor, 39; Penicillium, 37;
Protococcus, 14; Yeast, 6.

Labrum, 124.

Labyrinth, 186, 239.

Lamina terminalis, 178.

Laryngeal nerve, 182, 234.

Laryngo-tracheal cartilages, 173.

Larynx, 173, 195, 200.

Lateral ventricle, 178, 233.

Leaf, of Bean 68, 79; of Chara, 48;
of Fern, 54, 57, 64.

Lens, crystalliue, 237.

Liber, 71, 78, 79.

Lieno-intestinal vein, 172, 226.

Limbs, of Crayfish, 123, 136, 145;
of Frog, 152, 189; of Lobster, 123,
136, 145.

Lingual artery, 170, 228.

Liver, of Anodon, 106, 118; of Cray-
fish, 127, 142; of Frog, 166, 196;
of Lobster, 127, 142.

Lobster, 122; Laboratory work, 134.

Lumbosacral plexus, 184, 233.

Lung, 174, 200.

Lymph, 160.

Lymph hearts, 167, 172.

Lymph sinus, subvertebral, 158, 167.

M.

MANDIBLE, 124, 147, 211.

Mantle, 204, 111. ¥

Manubrium, 44.

Manus, 153, 214.

Maxilla, of Crayfish, 124, 146; of
Frog, 210.

Maxillipede, 124, 146.

Maxillo-mandibular nerve, 180.

Meckel’s cartilage, 164, 211.

Medulla, 70, 77; oblongata, 177,

231.

Medullary, cavity, 77; rays, 78;
sheath, 248.

Membrana tympani, 186, 188, 238.

Mento-Meckelian bone, 211.

Meropodite, 145.

Mesencephalon, 177, 231.

Mesenteric artery, 170.

Mesentery, 158, 196, 197.

Metacarpal bones, 215.

Metamorphosis, 110.

Metastoma, 124.

Metatarsal bones, 217.

INDEX,

Metencephalon, 177, 231.

Micrococcus, 27.

Micropyle, 68, 83, 84, 109,

Midbrain, 177, 231.

Motor oculi, nervus, 179.

Moulds, 29.

Mucor, 29, 32; Laboratory work, 39.

Muscle, histology of, 120, 144, 2463
physiology of, 256.

Muscular system, of Anodon, 1 193
of Hydra, 98,102; of Frog, 217.

Musculo-cutaneous vein, 171, 191,

227.
Mycelium, 30, 33, 37.
Myelon, 183, 231.
Myology, of the Frog, 217.

N.

NaREs, 1=9, 188, 199, 240.

Nasal bones, 209.

Nematocysts, 97, IOI.

gett cells, 145, 248; fibres, 145,
248.

Nerve, physiology of, 256.

Nervous system, of Anodon, 106, 108;
of Crayfish, 131, 143; of Frog,
177, 229; of Lobster, 131, 134.

Nerve, auditory, 232; brachial, 235;
crural, 184; facial, 182; glossopha-
ryngeal, 182, 234; hypoglossal, 195,
234; laryngeal, 182, 234; maxillo-
mandibular, 180; motor oculi, 179;
olfactory, 174,230; orbito-nasal, 180;
palatine, 180; pathetic, 180 ; sciatic,
184, 2243 trigeminal, 180; tibial,
184.

Nettle hair, protopl. movt. in, 53.

Neural, arch, 204; canal, 207; cavity,
160.

Nitella, 41, 51.

Node, 41, 47, 54, 61, 68, 76.

Notochord, 162.

Nucleolus, 18.

Nucleus, of Ameba, 18, 21; of ovule,
68, 83; of Vorticella, 89, gt.

oO.

OBLIQUE muscles, 186.

Occipital condyle, 208.

CEnothera biennis, 84.

(Esophageal artery, 170.
Csophagus, of Bell-animalcule, 87,

265

gt; of Anodon, 106, 118; of Cray-
fish, 126, 142; of Frog, 165, 199.

Olfactory, lobes, 177, 231 ; nerves, 174,
230; organs, 185, 240.

Omosternum, 212.

Opercular membrane, 156.

Ophthalmites, 125, 147.

Optic, commissure, 233; lobes, 177,
231; nerves, 179, 232, 237; thala-
mi, 178, 231; tracts, 232.

Orbito-nasal nerve, 180.

Organ of Bojanus, 107, 114.

Os, cruris, 216; femoris, 216; pubis,

215.

Otolith, 118, 186.

Ovary, of Anodon, tog, 119; of Cray-
fish, 141; of Frog, 176, 254; of
Hydra, 96, 103; of Lobster, 142.

Oviduct, 141, 142, 177, 199.

Ovules, 68, 83.

Ovum, of Anvdon, rog, 119; of Cray-
fish, 133; of Frog, 176, 256; of
Hydra, 97, 103; of Lobster, 133.

P.

PALATINE, bone, 209; nerve, 180.

Pallium, 105, 111.

Pancreas, 166, 196.

Papille, filitormes, 187, 241; fungi-
formes, 187, 241.

Pzrasphenoid bone, 209.

Parenchyma, 56, 62, 63, 70, 77.

Parieto-frontal bone, 208.

Parieto-splanchnic ganglion, 108, 116.

Pasteur’s fluid, 6.

Patheticus, nervus, 180.

Pectoral arch, 164, 212.

Pedal ganglion, 108, 116.

Peduncle, 81.

Pelvic arch, 164, 215.

Pelvic vein, 171, 225.

Penicillium, 29 ; Laboratory work, 37.

Pericardium, of Anodon, 107, 1133
of Crayfish, 127, 139; of Frog, 158,
193; of Lobster, 127, 139.

Perilymph, 186.

Peristome, 87, 90.

Periotic capsule, 164, 208,

Peroneal nerve, 184, 224.

Pes, 153, 217+

Petal, 82.

Petiole, 79.

Phalanges, 215, 217.

266

Pia mater, 203.

Pigment cells, 187, 251.

Pineal gland, 178, 231.

Pinnule, 54.

Pistil, 68, 81, 83.

Pith, 70, 77.

Pituitary body, 178, 232.

Pleuroperitoneal, cavity, 158; mem-
brane, 158, 192.

Plumule, 69, 84.

Pneumogastric nerve, 182, 234.

Pollen, 68, 82.

Posterior commissure, 178.

Posterior tibial nerve, 224.

Precoracoid, 213.

Prxnasal process, 163.

Premaxillary bone, 209.

Primine, 83.

Primitive sheath, 297.

Primordial utricle, 31, 44, 80.

Pro-embryo of Chara, 45.

Prootic, 208.

Propodite, 145.

Prosencephalon, 178, 230.

Proteus Animalcule, 17.

Prothallus, 59, 65.

Protococcus pluvialis, 11 ; Laboratory
work, 14.

Protoplasmic movements in vegetable
cells, 44, 51.

Protopodite, 125, 136.

Pseudopodia, 17, 22.

Pieris aquilina, 54 ; Laboratory work,

49.
Pterygoid bone, 210.
Pterygoid rod, 164.
Pulmocutaneous artery,
228. ;
Pulmonary, artery, 169, 170; vein,
168, 172, 229.
Putrefaction, 25.
Pylangium, 168.

Q

QUADRATE bone, 211.
Quadrato-jugal bone, 210.

R.

169, 1955

RacwHIs, 54.

Radicle, 69, 84.

Radius, 213.

Rana temporaria and R. esculenta,
1523 Laboratory work, 188.

INDEX.

Recti muscles, 185.

Rectum, of Anodon, 107, 1183; of
Crayfish, 127, 142; of Frog, 166,
196; of Lobster, 127, 142.

Renal veins, 172.

Renal portal veins, 226, 227.

Respiratory organs, of Anodon, 333;
of Crayfish, 130, 139; of Lobster,
130, 1393 of Frog, 173.

Restiform bodies, 177.

Retina, 238, 249.

Retractor bulbi, 185.

Rhinal processes, 163.

Rhinencepbalon, 230.

Rhizome, 54, 61.

Roots, of the spinal nerves, 184, 232.

Rootsheath, 69, 77.

8.

Saccharomyces cerevisie, 1; Labora-
tory work, 6.

Sacculus, 186.

Sacrum, 205.

Scalariform ducts, 57, 63.

Scaphognathite, 123, 146.

Scapular vein, 171.

Sciatic, nerve, 184; vein, 171, 226,

Sclerer:chyma, 56, 62, 63.

Sclerotic, 186, 237.

Secondary capitula, 44.

Secundine, 83.

Seed, 69, 84.

Seed-leaves, 69, 84.

Sense organs, of Anodon, 109, 117;
of Crayfish, 132, 147; of Frog, 185,
2353; of Lobster, 132, 147.

Sepals, 81.

Septum narium, 163, 240.

Sexual organs, of Anodon, rog, 119;
of Bean, 68, 82; of Chara, 44, 49;
of Crayfish, 133, 140; of Fern, 59,
66; of Frog, 175, 198; of Hydra,
96, 102; of Lobster, 133, 140.

Shell, of Anodon, 120.

Sinus venosus, 167, 193.

Siphons, of Lamellibranchiata, 106,
icon

Skeleton, of Anodon, 104, 120; of
Crayfish, 122, 134; of Frog, 161,
203; of Lobster, 122, 134.

Skull, 207.

Somite, 123, 134.

INDEX, 26

Sorus, 55, 64.

Spermatozoa, of Anodon, 109; of
Crayfish, 141; of Frog, 17¢, 1993
of Lobster, 142.

Spinal, column, 204; cord, 183, 231,
233% nerves, 104.

Spinous process, 204.

Spiral vessels, 57, 63, 71, 78, 81.

Sperillum volutans, 24, 28.

Spirochete, 28.

Splanchnic nerve, 183.

Spleen, 166, 196.

Sporangium, of Chara, 42, 45; of
Bracken, 55, 64; of Mucor, 32, 40.

meee Moulds, 30, 33; of Fern,
58, 65.

Spore fruit, 42, 45, 49.

Squamosal bone, 208.

Stamens, 68, 81, 82.

Starch, 44, 56, 63, 79.

Stellate cells, 80.

Stem, of Chara, 41, 47, 773 of Bracken
(rhizome), 54, 61.

Sternal artery, 128, 143.

Stigma, 68, 84.

Stipule, 79.

Stomach, of Anodon, 106, 118; of
Crayfish, 126, 142; of Frog, 160,
165, 196; of Lobster, 126, 142.

Stomata, 58, 71, 80, 81.

Stoneworts, 41.

Striated spindle, 132, 149.

Style, 68, 83.

Subclavian, artery, 170; vein, 171,
226.

Subeesophageal ganglion, 131, 193.

Sub-vertebral lymph sinus, 158.

Supracesophageal ganglion, 131, 143.

Suspensorium, 164.

Sympathetic system, 177, 185, 235-

Synangium, 168.

T.

TADPOLE, 156.

Tarsus, 216.

Teeth, of Frog, 159, 165; gastric, of
Crayfish, 127.

Telson, 123, 137.

Tendo Achillis, 222.

Tendril, 79.

Tentacles, 95, 99.

Terminal bud, of Chara, 42,.48; of
Bean, 69, 71.

=I

Terminal cell, 42, 48, 49.

Testa, 89.

Testis, of Anodon, 109; of Cray-
fish, 140; of Frog, 175, 199, 2533
of Hydra, 96, 102; of Lobster,

14t.
Thalamencephalon, 177, 231.
Thalami optici, 178, 231.
Third ventricle, 178, 231.
Thread cells, 97, 101.
Thyimus gland, 173.
Thyrohyal, 212.
Thyroid gland, 173.
Tibia, 216. a
Tibial nerve, 184.
Tongue, 159, 187, 188.
Torula cerevisiae, 1 ; Laboratory work,

Torula, of Mucor, 36.

Tradescantia, protopl. movts. in, 52.
Trausverse process, 204.

Trigeminal nerve, 180.

Trachea, 173, 200.

Truncus arteriosus, 167, 168, 193.
Tympanic membrane, 186, 238.
Tympanum, 186, 238.

Uz

Una, 213.

Umbo, 120.

Unguis, 82.

Unio, 104.

Ureter, 175, 198.

Urinary bladder, 175, 196.
Urostyle, 162, 205.
Urticating capsules, 97.
Utriculus, 186.

Vv.

VACUOLE, alimentary, 91; contractile
18; in vegetable cells, 2, 7, 30, 33,
37, 48.

Varus nerve, 183, 234.

Vallisneria, protopl. movts. in, 52.
Vas deferens, of Crayfish, 141; of
Frog, 175, 199; of Lobster, 141.

Vascular bundles, 57, 62, 70, 77.

Vascular system, see Circulatory or-
gans.

Vein, axillary, 227'; brachial, 171,
227; branchio cardiac, 129; dorso-
lumbar, 172; femoral, 171; gas-

268

tric, 172, 226; iliac, 172; innomi-
nate, 171, 227; jugular, external,
171, 226; jugular, internal, 171, 229;
lieno-intestinal, 172, 226; musculo-
cutaneous, 171, 191, 227; pelvic,
171, 225; pulmonary, 168, 172;
scapular, 171; sciatic, 171, 226;
subclavian, 171, 226; renal, 172;
renal portal, 226, 227; portal, 173,
226,

Vena, cava, of Anodon, 107, 114; of
Frog, infr., 171, 227 ; of Frog, supr.,
171, 227; innominata, 171, 2273
porte, 173, 226.

Venous system of Frog, 171.

Ventricles of the brain, 177.

Vertebra, 204.

Vertebral artery, 170.

Vertebral column, 204.

Veronica serpyllifolia, 85.

Vesicula seminalis, 198.

Vestibulum, 87, go.

Vexillum, 82.

Vibriones, 25, 28.

Vicia faba, 68;
76.

Laboratory work,

INDEX.

Vitelline membrane, 176, 255.

Vitellus, 103, 176, 256.

Vitreous humour, 238.

Visceral nervous system, of Crayfish,
131.

Vocal, sacs, 159; ligaments, 173.

Vomer, 210.

Vorticella, 86; Laboratory work, go,

w.

Waite fibrous tissue, 245.
Wood, 70, 78.

xX:
XIPHISTERNUM, 212.
Y.
Yeast, 1; Laboratory work, 6.
Yelk division, Hydra, 97; Frog, 156.
Z.

ZOOGLOBA, 25, 27.
Zygapophysis, 204.
Zygospore, 35.

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MATHEMATICS. 13

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MATHEMATICS. 15

Todhunter (I.)—continued.

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16 EDUCATIONAL BOOKS.

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PROBLEMS, on Subjects included in the Cambridge Course.
By JosEPH WOLSTENHOLME, Fellow of Christ’s College, some-
time Fellow of St. John’s College, and lately Lecturer in Mathe-
matics at Christ’s College. Crown 8vo. cloth. 8». 6d.

“ Sudicious, symmetrical, and well arranged.” — GUARDIAN.

SCIENCE.

ELEMENTARY CLASS-BOOKS.

Ir is the intention of the Publishers to produce a com-
plete series of Scientific Manuals, affording full and ac-
curate elementary information, conveyed in clear and
lucid English, The authors are well known as among
the foremost men of their several departments ; and their
names form a ready guarantee for the high character of the
books. Subjoined is a list of those Manuals that have
already appeared, with a short account of each. Others
are in active preparation; and the whole will constitute a
standard series specially adapted to the requirements of be-
ginners, whether for private study or for school instruction.
ASTRONOMY, by the Astronomer Royal.
POPULAR ASTRONOMY. With Illustrations. By Sir GB,
Ary, K.C.B., Astronomer Royal. New Edition. 18mo.
cloth. 45. 6d.
Six lectures, intended “ to explain to intelligent persons the principles
on which the instruments of an Observatory are constructed, and the
principles on which the observations made with these instruments are

treated for deduction of the distances and weights of the bodies of the
Solar System.”

ASTRONOMY.
ELEMENTARY LESSONS IN ASTRONOMY. With
Coloured Diagram of the Spectra of the Sun, Stars, and
Nebula, and numerous Illustrations, By J. NorMAN LOCKYER,
F.R.S. New Edition. 18mo. 5s. 6d.

“ Full, clear, sound, and worthy of attention, not only as a popular expo-
sition, but as a scientific ‘Index.””’—ATHENEUM. ‘* The most fasci-
nating of elementary books on the Sciences.”—NONCONFORMIST.

SCIENCE, 17

Elementary Class-Books—continued.

QUESTIONS ON LOCKYER’S ELEMENTARY LESSONS
IN ASTRONOMY. For the Use of Schools. By Joun FoRBEs-
ROBERTSON. 18mo. cloth limp. 1s. 6d.

PHYSIOLOGY.

LESSONS IN ELEMENTARY PHYSIOLOGY. With
numerous Illustrations. By T, H. Huxrey, F.R.S., Professor
of Natural History in the Royal School of Mines, New Edition.
18mo. cloth. 4s. 6d.

“ Pure gold throughout.”—GuUARDIAN. ‘* Unquestionably the clearest
and most complete elementary treatise on this subject that we possess in
any language.” —WESTMINSTER REVIEW.

QUESTIONS ON HUXLEY’S PHYSIOLOGY FOR SCHOOLS.
By T. Atcock, M.D. 18mo, Is. 6d.

BOTANY.
LESSONS IN ELEMENTARY BOTANY. By D, Otiver,
F.R.S., F.L.S., Professor of Botany in University College, London.
With nearly Two Hundred Illustrations. New Edition. 18mo.
cloth. 45. 6d.

CHEMISTRY.
LESSONS IN ELEMENTARY CHEMISTRY, INORGANIC
AND ORGANIC, By Henry E. Roscog, F.R.S., Professor of
Chemistry in Owens College, Manchester. With numerous IIlus-
trations and Chromo-Litho of the Solar Spectrum, and of the Al-
kalies and Alkaline Earths. New Edition. 18mo. cloth. 4s. 6d.
*¢ As a standard general text-book it deserves to take a leading place,”
SpecTaTor. ‘* We unhesitatingly pronounce it the best of all our
elementary treatises on Chemistry.” —MEDICAL TIMES,

POLITICAL ECONOMY.
POLITICAL ECONOMY FOR BEGINNERS. By MILuicentT
G. Fawcett. New Edition. 18mo. 2s. 6d,
“* Clear, compact, and comprehensive.”"—DatLy News. ‘‘ The relations
of capital and labour have never been more simply or move clearly
expounded.”—CONTEMPORARY REVIEW.

LOGIC.

ELEMENTARY LESSONS IN LOGIC ; Deductive and Induc-
tive, with copious Questions and Examples, and a Vocabulary of
Logical Terms. By W. STANLEY JEVoNS, M.A., Professor of Logic
in Owens College, Manchester. New Edition. 18mo. 3s. 6d,

‘© Nothing can be better for a school-book.” —GUARDIAN.

“« 4 manual alike simple, interesting, and scientific,” —ATHEN&UM.

PHYSICS.
LESSONS IN ELEMENTARY PHYSICS. By Batrour
STEWART, F.R.S., Professor of Natural Philosophy in Owens
College, Manchester, With numerous Illustrations and Chromo-
B

18 EDUCATIONAL BOOKS.

Elementary Class-Books—continued.
liths of the Spectra of the Sun, Stars, and Nebule. New Edition,
18mo. 45. 6a.
“_ The beau ideal of a scientific text-book, clear, accurate, and thorough.”
EDUCATIONAL TIMES.
PRACTICAL CHEMISTRY.
THE OWENS COLLEGE JUNIOR COURSE OF PRAC-
TICAL CHEMISTRY. By Francis Jones, Chemical Master
in the Grammar School, Manchester. With Preface by Professor
Roscoxr. With Illustrations. New Edition. 18mo. 2s. 6d.
ANATOMY.
LESSONS IN ELEMENTARY ANATOMY. By St. GrorcE
Mivart, F.R.S., Lecturer in Comparative Anatomy at St. Mary’s
Hospital. With upwards of 4oo Illustrations. 18mo. 6s. 6d.
“Tt may be questioned whether any other work on Anatomy contains
in like compass so proportionately great amass of information.” —LANCET.
“* The work is excellent, and should be in the hands of every student of
human anatomy.” —MEDICAL TIMES,

STEAM.—AN ELEMENTARY TREATISE. By Joun Perry,
Bachelor of Engineering, Whitworth Scholar, etc., late Lecturer in
Physics at Clifton College. With numerous Woodcuts and
Numerical Examples and Exercises. 18mo. 4s. 6d.

MANUALS FOR STUDENTS.

Flower (W. H.)—AN INTRODUCTION TO THE OSTE-
OLOGY OF THE MAMMALIA. Being the substance of
the Course of Lectures delivered at the Royal College of Surgeons
of England in 1870, By W. H. Fiower, F.R.S., F.R.C.S.,
Hunterian Professor of Comparative Anatomy and Physiology,
With numerous Illustrations, Globe 8vo. 7s. 6d.

Hooker (Dr.)}—THE STUDENT’S FLORA OF THE
BRITISH ISLANDS, By J. D. Hooker, C.B., F.R.S.,
M.D., D.C.L., President of the Royal Society. Globe 8vo.
los. 6d.

** Cannot fail to perfectly fulfil the purpose for which it is intended.” —

LAND AND WATER.—‘‘ Containing the fullest and most accurate

manual of the kind that has yet appeared.”—PALL MALL UWAZETTE.

Oliver (Professor).—FIRST BOOK OF INDIAN BOTANY,
By DanreL Otiver, F.R.S., F.L.S., Keeper of the Herbarium
and Library of the Royal Gardens, Kew, and Professor of Botany
in University College, London, With numerous Illustrations,
Extra feap. 8vo. 6s. 6d.

“* Tt contains a well-digested summary of all essential knowledge pertain-
ing to Indian botany, wrought out in accordance with the best principles
of scientific arrangement.” —ALLEN’S INDIAN MAIL.

’ Other volumes of these Manuals will follow.

SCIENCE, 19

NATURE SERIES.

THE SPECTROSCOPE AND ITS APPLICATIONS. By J.
Norman Lockyer, F.R.S. With Coloured Plate and numerous
illustrations. Second Edition... Crown 8vo. 3s. 6d.

THE’ ORIGIN AND METAMORPHOSES OF INSECTS. By

Sir Joun Lussock, M.P., F.R.S. With numerous Illustrations.
Second Edition. Crown 8vo. 35. 6d.
“* We can most cordially recommend it to young naturalists.” —ATHE-

N/EUM.

THE BIRTH OF CHEMISTRY. By G. F. Ropwett, F.R.A.S.,
F.C.S., Science Master in Marlborough College. With numerous
Illustrations. Crown 8vo. 35. 6d.

“We can cordially recommend it to all Students of Chemistry.’?—

CHEMICAL NEws.

THE TRANSIT OF VENUS. By G. Fornss, M.A., Professor of
Natural Philosophy in the Andersonian University, Glasgow.
Illustrated. Crown 8vo. 35. 64.

Other volumes to follow.

Ball (R. S., A.M.)—EXPERIMENTAL MECHANICS,
A Course of Lectures delivered at the Royal College of Science
for Ireland. By R. S. Bari, A.M., Professor of Applied
Mathematics and Mechanics in the Royal College of Science
for Ireland. Royal 8vo. 16s.

Clodd._THE CHILDHOOD OF THE WORLD: a Simple
Account of Man in Early Times. By Epwarp CLopp, F.R.A.S.
Third Edition. Globe 8vo. 3s. Also a Special Edition for
Schools. 18mo, Is.

ProFEssOR Max MULLER, ix a@ letter to the Author, says: ‘‘I read
your book with great pleasure, I have no doubt it will do good, and I
hope you will continue your work. Nothing spoils our temper so much as
having to unlearn in youth, manhood, and even old age, so many things
which we were taught as children. A book like yours will prepare a far
better soil in the child’s mind, and I was delighted to have it to read to
my children.”

Cooke (Josiah P., Jun.)—FIRST PRINCIPLES OF
CHEMICAL PHILOSOPHY. By Jostan P. Cookg, Jun.,
Ervine Professor of Chemistry and Mineralogy in Harvard College.
Third Edition, Revised and Corrected. Crown 8vo, 125.

Thorpe (T. E.)—A SERIES OF CHEMICAL PROBLEMS,
for use in Colleges and Schools, Adapted for the preparation of
Students for the Government, Science, and Society of Arts Ex-
aminations. With a Preface by Professor Roscoz. 18mo.
cloth. 1s. Key. 1s.

B 2

20 EDUCATIONAL BOOKS.

SCIENCE PRIMERS FOR ELEMENTARY
SCHOOLS.

The necessity of commencing the teaching of Science in Schools at an
early stage of the pupil’s course has now become generally recog-
nized, and is enforced in all Schools undér Government inspection.
For the purpose of facilitating the introduction of Science
Teaching into Elementary Schools, Messrs. Macmillan are now
publishing a New Series of Science Primers, under the joint
Editorship of Professors Huxiey, Roscorz, and BALFour
STEWART. The object of these Primers is to convey information
in such a manner as to make it both intelligible and interesting to
pupils in the most elementary classes. They are clearly printed on
good paper, and illustrations are given whenever they are necessary
to the proper understanding of the text. The following are just
published :—

PRIMER OF CHEMISTRY. By H. E. Roscor, Professor of
Chemistry in Owens College, Manchester. 18mo. Is. Third
Edition.

PRIMER OF PHYSICS. By Batrour STEWartT, Professor of
Natural Philosophy in Owens College, Manchester. 18mo. Is.
Third Edition.

PRIMER OF PHYSICAL GEOGRAPHY. By ARCHIBALD
GeIKIE, F.R.S., Murchison-Professor of Geology and Mineralogy
at Edinburgh. Second Edition, 18mo._ Is.

Everyone ought to know something about the air we breathe and the
earth we live upon, and about the relations between them; and in this
little work the author wishes to show what sort of questions may be put
about some of the chief parts of the book of nature, and especially about two
of them—the Air and the Earth. The divisions of the book are as
follows :—The Shape of the Earth—Day and Night—The Air—The
Circulation of Water on the Land—The Sea— The Inside of the Earth,
PRIMER OF GEOLOGY. By PRoressor GEIKIE, F.R.S. With

numerous Illustrations. Second Edition. 18mo. cloth. 1s.

Ln these Primers the authors have aimed, not so much to give informa-
tion, as to endeavour to discipline the mind in u way which has not
hitherto been customary, by bringing it into immediate contact with
Nature herself. For this purpose a series of simple experiments (to be
performed by the teacher) has been devised, leading up to the chief truths
of each Science. Thus the power of observation in the pupils will. be
awakened and strengthened. Each Manual ts copiously illustrated, and
appended are lists of all the necessary apparatus, with prices, and
directions as to how they may be obtained. Professor Huxley's introduc-
tory volume has been delayed through the iliness of the author, but it is
now expected to appear very shortly. ‘* They are wonderfully clear and
lucid in their instruction, simple in style, and admirable in plan.” —
EDUCATIONAL TIMES,

MISCELLANEOUS. ar

Science Primers—continued.

PRIMER OF PHYSIOLOGY. By Micuart Foster, M.D.,
F.R.S. With numerous Tllustrations. 18mo. Is,

In preparation :—

INTRODUCTORY. By Proressor HUXLEY.

PRIMER OF BOTANY. By Dr. Hooker, C.B., F.R.S.

PRIMER OF ASTRONOMY. By J. Norman Lockyer, F.R.S.
Sa &e.

- MISCELLANEOUS.

Abbott.—A SHAKESPEARIAN GRAMMAR. An Attempt to
illustrate some of the Differences between Elizabethan and Modern
English. By the Rev. E. A. Apgort, M.A., Head Master of the
City of London School. For the Use of Schools, New and
Enlarged Edition. Extra fcap. 8vo. 65.

“* 4 critical inquiry, conducted with great skill and knowledge, and
with all the appliances of modern philology... . We venture to believe
that those who consider themselves most proficient as Shakespearians
will find something to learn from its pages.” —PALL MALL GAZETTE.
“ Valuable not only as an aid to the critical study of Shakespeare, but
as tending to familiarize the reader with Elizabethan English in
general,’ —ATHENAUM,

Barker.—FIRST LESSONS IN THE PRINCIPLES OF
COOKING. By Lapy BarKER, 18mo. Is.

“* 4n unpretending but invaluable little work... . The plan ts
admirable in its completeness and simplicity ; it is hardly possible that
anyone who can read at all can fail to understand the practical lessons on
bread and beef, fish and vegetables ; while the explanation of the chemical
composition of our food must be intelligible to all who possess sufficient
education to follow the argument, in which the fewest possible technical
terms are used.” —SPECTATOR.

Berners.— FIRST LESSONS ON HEALTH. By J. BzR-
NERS. 18mo. 1s. Third Edition.

Besant.—STUDIES IN EARLY FRENCH POETRY. By
Water BESANT, M.A. Crown 8vo. 8s. 6d.

“© Tn one moderately sized volume he has contrived to introduce us to the
very best, if not to all of the early French poets.” ~ATHENEUM. ‘‘Jn-
dustry, the insight of a scholar, and a genuine enthusiasm for his subject,
combine to make it of very considerable value.” —SPECTATOR.
Breymann.—A FRENCH GRAMMAR BASED ON PHI-

TOLOGICAL PRINCIPLES. By HERMANN BREYMANN,
Ph.D., Lecturer on French Language and Literature at Owens
College, Manchester. Extra fcap. 8vo. 45. 6d.

‘ We dismiss the work with every expression of satisfaction. It can-

not fail to be taken into use by all schools which endeavour to make the

220 EDUCATIONAL BOOKS.

study of French a means towards the higher culture.”’—EDUCATIONAL
Times. ‘'A good, sound, valuable philological grammar. The author
presents the pupil by ‘his method and by detail, with an enormous amount
of information about French not usually to be found in grammars, and
the information is all of it of real practical value to the student who
really wants to know French well, and to understand tts spirit. . . At
the end a long chapter called ‘ Reasons and Illustrations’ forms an
exceedingly interesting and valuable dissertation upon French philo-
logy.” —SCHOOL BOARD CHRONICLE.

Calderwood.—HANDBOOK OF MORAL PHILOSOPHY.
By the Rev. HENRY CALDERWOOD, LL.D., Professor of Moral
Philosophy, University of Edinburgh. Second Edition, Crown
8yo. 6s.

“A compact and useful work... . will be an assistance to many
students outside the author's own University.””—GUARDIAN.

Delamotte.—A BEGINNER’S DRAWING BOOK. By P. H.
DetamoTTe, F.S.A. Progressively arranged. New Edition,
improved. Crown 8vo. 35. 6d.

“© We have seen and examined a great many drawing-books, but the one
now before us strikes us as being the best of them all,” —ILLUSTRATED
Times. ‘‘A concise, simple, and thoroughly practical work, The
letterpress is throughout intelligible and to the point.” —GUARDIAN.

Goldsmith.—THE TRAVELLER, or a Prospect of Society ;
and THE DESERTED VILLAGE. By OLIvER GoLnsMITH.
With Notes Philological and Explanatory, by J. W. HaLes, M.A.
Crown 8yo, 6d.

Green.—A HISTORY OF THE ENGLISH PEOPLE. By the
Rev. J. R. GREEN, M.A. For the use of Colleges and Schools.
Crown 8vo.

Hales.—LONGER ENGLISH POEMS, with Notes, Philological
and Explanatory, and an Introduction on the Teaching of English,
Chiefly for use in Schools. Edited by J. W. Hates, M.A., late
Fellow and Assistant Tutor of Christ’s College, Cambridge,
Lecturer in English Literature and Classical Composition at King’s
College School, London, &c. &c. Extra feap, 8vo. 4s. 6d.

Helfenstein (James).—A COMPARATIVE GRAMMAR
OF THE TEUTONIC LANGUAGES. Being at the same
time a Historical Grammar of the English Language, and comprising
Gothic, Anglo-Saxon, Early English, Modern English, Icelandic
(Old Norse), Danish, Swedish, Old High German, Middle High
German, Modern German, Old Saxon, Old Frisian, and Dutch.
By JAMES HELFENSTEIN, Ph.D. 8vo. 185,

Hole.—A GENEALOGICAL STEMMA OF THE KINGS OF
ENGLAND AND FRANCE. By the Rev. C. Hotz, On
Sheet, 1s.

MISCELLANEOUS. 23

Jephson.—SHAKESPEARE’S “TEMPEST.” With Glossarial

and Explanatory Notes. By the Rev. J. M. Jepuson. Second
Edition, 18mo. 1s.

Kington-Oliphant.—THE SOURCES OF STANDARD
ENGLISH. By J. KincTon-OLipHant. Extra feap. 8vo. 65.
*“* Mr. Oliphant’s book is, to our mind, one of the ablest and most
scholarly contributions to our standard English we have seen for many
years... . The arrangement of the work and its indices make it in-
valuable as a work of reference, and easy alike to study and to store, when
studied, in the memory.”—SCHOOL BOARD CHRONICLE. ‘“* Comes
nearer to a history of the English language than anything that we have
seen since such a history could be written without confusion and con-
tradictions.”—SATURDAY REVIEW.

Martin.—THE POET’S HOUR: Poetry Selected and Arranged
for aoe By FRANcEsS MarTIN. Second Edition, 18mo.
2s. 6d.

Nearly 200 Poems selected from the best Poets, ancient and modern,
and intended mainly for children between the ages of eight and twelve.

SPRING-TIME WITH THE POETS. Poetry selected by FRANCES
Martin. Second Edition. 18mo. 35. 6d.
Intended mainly jor girls and boys between the ages of twelve and seven-
teen,

Masson (Gustave).—A COMPENDIOUS DICTIONARY
OF THE FRENCH LANGUAGE (French-English and English-
French). Followed by a List of the Principal Diverging Deriva-
tions, and preceded by Chronological and Historical Tables. By
GusTAVE Masson, Assistant-Master and Librarian, Harrow
School. Square half-bound, 6s,

This volume, though cast in the same form as other dictionaries, has
several distinctive features which increase its value for the student. In the
French-English part, etymologies, founded on the researches of Messrs,
Littré, Schéler, and Brachet, ave given. The list of diverging deriva-
tions, at the end of the volume, will be very useful to those who are
interested in tracing the various developments of original Latin words.
But that which makes it almost indispensable to students of the political
and literary history of France, ts to be found at the beginning of the work,
where M.” Masson has drawn up clear and complete tables of historical
events, viewed in connection with the developments of literature and lan-
guage, between the death of Charlemagne, 814 A.D., and that of Louis
Philippe, 1850. These tables are illustrated by remarks on the various
social moods, of which the works produced were the expression. Appended
also is a list of the principal Chronicles and Memoirs on the LHistory of
France which have appeared up to the present time; the French Re-
publican Calendar, compared with the Gregorian ; and a Chronological
list of the principal French Newspapers published during the Revolution
and the First Empire.

24 EDUCATIONAL BOOKS.

Morris.—works by the Rev. R. Morris, LL.D., Lecturer on
English Language and Literature in King’s College School.

HISTORICAL OUTLINES OF ENGLISH ACCIDENCE,
comprising Chapters on the History and Development of the
ney ae and on Word-formation. Third Edition. Extra fcap.

vo. 65.

“It makes an eva in the study of the English tongue.’—SATURDAY
Review. ‘He has done his work with a fulness and completeness
that leave nothing to be desired.”—NONCONFORMIST. ‘A genuine
and sound book,” —ATHENAUM.

ELEMENTARY LESSONS IN HISTORICAL ENGLISH
as sue Containing Accidence and Word-formation. 18mo,
2s. 6d.

Oppen.—FRENCH READER. For the Use of Colleges and
Schools, Containing a graduated Selection from modern Authors
in Prose and Verse; and copious Notes, chiefly Etymological. By
Epwarp A. OpPEN. Feap. 8vo. cloth. 45. 6d.

Pylodet.—NEW GUIDE TO GERMAN CONVERSATION:
containing an Alphabetical List of nearly 800 Familiar Words
similar in Orthography or Sound and the same Meaning in both
Languages, followed by Exercises, Vocabulary of Words in
frequent use, Familiar Phrases and Dialogues; a Sketch of German
Literature, Idiomatic Expressions, &c. ; and a Synopsis of German
Grammar. By L. PyLopET. 18mo. cloth limp. 2s. 6d.

Sonnenschein and Meiklejohn.— THE ENGLISH
METHOD OF TEACHING TO READ. By A. SONNENSCHEIN
and J. M. D. MEIKLEJonN, M.A. Fcap. 8vo.

COMPRISING :

THE Nursery Book, containing all the Two-Letter Words in
the Language. Id. (Also in Large Type on Sheets for
School Walls. 5s.)

Tue First Course, consisting of Short Vowels with Single
Consonants. 3d.

THE SECOND CourRsE, with Combinations and Bridges, con-
sisting of Short Vowels with Double Consonants. 4d.

THE THIRD AND FourTH CouksES, consisting of Long
Vowels, and all the Double Vowels in the Language. 6d.

“© These ave admirable books, because they are constructed on a principle,
and that the'simplest principle on which it is possible to learn to read
English.” —SPECTATOR,

Taylor.—woRDS AND PLACES; or, Etymological Tllus-
trations of History, Ethnology, and Geography. By the Rev.
Isaac Taytor, M.A. Third and cheaper Edition, revised and
compressed. With Maps. Globe 8vo. 6s.

Already been adopted by many teachers, and prescribed as a text-book in
the Cambridge Higher Examinations for Women.

HISTORY. 28

Thring.—Works by Epwarp THRING, M.A., Head Master of
Uppingham. |

THE ELEMENTS OF GRAMMAR TAUGHT IN ENGLISH,
with Questions. Fourth Edition. 1r8mo. 2s,

THE CHILD’S GRAMMAR. Being the Substance of “The
Elements of Grammar taught in English,” adapted for the Use of
Junior Classes. A New Edition. 18mo. 1s.

SCHOOL SONGS. A Collection of Songs for Schools, With the
Music arranged for four Voices. Edited by the Rev. E. THRING
and H. Riccius. Folio. 7s. 6d.

Trench (Archbishop). — HOUSEHOLD BOOK OF ENG-
LISH POETRY. Selected and Arranged, with Notes, by
R. C. Trencu, D.D., Archbishop of Dublin. Extra fcap. 8vo.
5s. 6d. Second Edition.

“The Archbishop has conferred in this delightful volume an impor-
tant gift on the whole English-speaking population of the world,” —PALL
MALL GAZETTE.

ON THE STUDY OF WORDS. Lectures addressed (originally)
to the Pupils at the Diocesan Training School, Winchester.
Fourteenth Edition, revised. Feap. 8vo. 4s. 6d.

ENGLISH, PAST AND PRESENT. Eighth Edition, revised
and improved. Fcap. 8vo. 45. 6d.

A SELECT GLOSSARY OF ENGLISH WORDS, used formerly
in Senses Different from their Present. Fourth Edition, enlarged.
Feap. 8vo. 45. 6d.

Vaughan (C. M.)—A SHILLING BOOK OF WORDS
FROM THE POETS. By C. M. Vaucuan. 18mo, cloth.

Whitney.— Works by Witt1am D. WHITNEY, Professor of San-
skrit and Instructor in Modern Languages in Yale College ; first
President of the American Philological Association, and hon.
member of the Royal Asiatic Society of Great Britain and Ireland ;
and Correspondent of the Berlin Academy of Sciences.

A COMPENDIOUS GERMAN GRAMMAR. Crown 8vo. 6s.

A GERMAN READER IN PROSE AND VERSE, with Notes and
Vocabulary. Crown 8vo. 75. 6.

Yonge (Charlotte M.)—THE ABRIDGED BOOK OF
GOLDEN DEEDS. A Reading Book for Schools and General
Readers. By the Author of “The Heir of Redclyffe.” 18mo.,

cloth. Is.
HISTORY.

Freeman (Edward A.)—OLD-ENGLISH HISTORY.
By Epwarp A. Freeman, D.C.L., late Fellow of Trinity
College, Oxford. With Five Coloured Maps, Third Edition.
Extra fcap. 8vo. half-bound. 6s.

26 EDUCATIONAL BOOKS.

‘I have, I hope,” the author says, ‘‘ shown that it is perfectly easy to
teach children, from the very first, to distinguish true history alike from
legend and from wilful invention, and also to understand the nature of
historical authorities and to weigh one statement against another. I have
throughout striven to connect the history of England with the general
history of civilixd Europe, and I have especially tried to make the
book serve as an incentive to a more accurate study of historical
geography.” In the present edition the whole has been carefully revised,
and such improvements as suggested themselves have been introduced.
“* The book indeed is full of instruction and interest to students of all
ages, and he must be a well-informed man indeed who will not rise from
tts perusal with clearer and more accurate ideas of a too much neglected
bortion of English History.” —SPECTATOR.

Historical Course for Schools.—kdited by Epwarp
A. Freeman, D.C.L., late Fellow of Trinity College, Oxford.
The object of the present series is to put forth clear and correct views
of history in simple language, and in the smallest space and cheapest
form in which it could be done. It is meant in the first place for
Schools ; but it is often found that a book for schools proves useful
for other readers as well, and it is hoped that this may be the case
with the little books the first instalment of which is now given to
the world. The General Sketch will be followed by a series of
special histories of particular countries, which will take for granted
the main principles laid down in the General Sketch. In every case
the results of the latest historical research will be given in as simple
a form as may be, and the several numbers of the series will all be
so far under the supervision of the Editor as to secure general ac-
curacy of statement and a general harmony of plan and sentiment ;
but each book will be the original work of its author, who will
be responsible for his own treatment of smaller details.

The first volume ts meant to be introductory to the whole course. It
is intended to give, as its name implies, a general sketch of the history of
the civilized world, that is, of Europe, and of the lands which have drawn
their civilization from Europe. Its object ts to trace out the general rela-
tions of different periods and different countries to one another, without
going minutely into the affairs of any particular country. This isan
object of the first importance, for without clear notions of general history,
the history of particular countries can never be rightly understood. The
narrative extends from the earliest movements of the Aryan peoples, down
to the latest events both on the Eastern and Western Continents, The
book consists of seventeen moderately sized chapters, each chapter being
divided into a ber of short numbered paragraphs, each with a tlle
prefixed clearly indicative of the subject of the paragraph.

I. GENERAL SKETCH OF EUROPEAN HISTORY. By
Epwarp A, FREEMAN, D.C.L. Third Edition. 18mo. cloth.
35. 6d,

“* Tt supplies the great want of a good foundation for historical teach-

ing. The scheme is an excellent one, and this instalment has been

ALISTORY. 24

Historical Course for Schools—continued.

executed in a way that promises much’ for the volumes that are yet to

appear.” —EDUCATIONAL TIMES.

Il, WISTORY OF ENGLAND. By Epiru Tuomrson. Fourth
Edition. 18mo. 2s. 6d.

‘Freedom from prejudice, simplicity of style, and accuracy of statement,
are the characteristics of this little volume. It is a trustworthy text-book
and likely to be generally serviceable in schools."—Patt. MALL GAZETTE.
“Upon the whole, this manual is the best sketch of English history for the
use of young people we have yet met with.”—ATHENAUM.

III. eee OF SCOTLAND. By MarcareT MACARTHUR.
18mo. 25.

“* An excellent summary, unimpeachable as to facts, and putting them in
the clearest and most impartial light attainable.”—GUARDIAN. “ Miss
Macarthur has performed her task with admtrable care, clearness, and
fulness, and we have now for the first time a really good School History
of Scotland.” —EDUCATIONAL TIMES.

IV. HISTORY OF ITALY. By the Rev. W. Hunt, M.A. 18mo.
35.

** Tt possesses the same solid merit as its predecessors... . the same
scrupulous care about fidelity in details. . . It is distinguished, too, by
information on art, architecture, and social politics, in which the writers
grasp ts seen by the firmness and clearness of his touch.” —EDUCATIONAL
TIMEs.

V. HISTORY OF GERMANY. By J. Simz, M.A. 18mo. 3s.

‘A remarkably clear and impressive History of Germany. Its great
events are wisely kept as central figures, andthe smaller events are carcfully
hept, not only subordinate and subservicnt, but most skilfully woven into
the texture of the historical tapestry presented to the eye.” —STANDARD.

The following will shortly be issued :—

FRANCE, By the Rev. J. R. GREEN, M.A.
GREECE. By J. Annan Bryce, B.A.
AMERICA. By Joun A. DoyLe.

Yonge (Charlotte M.)—a PARALLEL HISTORY OF
FRANCE AND ENGLAND: consisting of Outlines and Dates.
By CHARLOTTE M. YONGE, Author of ‘‘The Heir of Redclyffe,”
*“Cameos of English History,” &c. &c. Oblong 4to. 35. 6d.

‘* We can imagine few more really advantageous courses of historical
study for a young mind than going carefully and steadily through Miss
Yonge’s excellent little book,” —KDUCATIONAL TIMES.

CAMEOS FROM ENGLISH HISTORY. From Rollo to Edward
II. By the Author of “The Heir of Redclyffe.” Extra fcap,
8vo. Second Edition, enlarged. 35. 6d.

A book for young people just beyond the elementary histories of England,
and able to enter in some degree into the real spirit of events, and to be
struck with characters and scenes presented in some relief. “ Instead of

28 EDUCATIONAL BOOKS.

Yonge (Charlotte M.)—continued.

ary details, we have living pictures, faithful, vivid, ‘and striking.” —

NonconFormIstT.

A SEconp SERizs OF CAMEOS FROM ENGLISH HISTORY.
THE WaRS IN FRANCE. Second Edition. Extra fcap. 8vo. 595.

“* Though mainly intended for young readers, they will, if we mistake
not, be found very acceptable to those of more mature years, and the
life and reality imparted to the dry bones of history cannot fail to be
attractive to readers of every age.” —JOHN BULL.

EUROPEAN HISTORY. Narrated ina Series of Historical Selec-
tions from the Best Authorities. Edited and arranged by E, M.
SEWELL and C. M. YoncE. First Series, 1003—1154. Third
Edition. Crown 8vo. 6s. Second Series, 1088—1228. Crown
8vo. 6s. Second Edition.

“ We know of scarcely anything which is so likely to raise to a higher
level the average standard of English education.” —GUARDIAN.

DIVINITY.

*,* For other Works by these Authors, see THEOLOGICAL CATALOGUE,

Abbott (Rev. E. A.)—BIBLE LESSONS. By the Rev.
E, A. Abbott, M.A., Head Master of the City of London School.
Second Edition. Crown 8vo. 45. 6d.

“* Wise, suggestive,and really profound initiation into religious thought.”
—GUARDIAN. ‘‘J think nobody could read them without being both the
better for them himself, and being also able to see how this difficult duty of
imparting a sound religious education may be effected.””—BISHOP OF ST.
DaVIp’s AT ABERGWILLY.

Arnold.— A BIBLE-READING FOR SCHOOLS. The
GREAT PROPHECY OF ISRAEL’S RESTORATION (Isaiah, Chapters
40—66). Arranged and Edited for Young Learners. By Mat-
THEW ARNOLD, D.C.L., formerly Professor of Poetry in the
University of Oxford, and Fellow of Oriel. Third Edition. 18mo.
cloth, Is.

“* There can be no doubt that it will be found excellently calculated to
further instruction in Biblical literature in any school into which it may
be introduced ; and we can safely say that whatever school uses the book,
it will enable its pupils to understand Isaiah, a great advantage compared
with other establishments which do not avail themselves of it.” —TIMES.
“Mr, Arnold has done the greatest possible service to the public. We never
read any translation of Isaiah which interfered so little with the musical
rhythm and associations of our English Bible translation, while doing
so much to display the missing links in the connection of the parts.” —
SPECTATOR.

Golden Treasury Psalter.—sStudents’ Edition. Being an
Edition of “The Psalms Chronologically Arranged, by Four
Friends,” with briefer Notes. 18mo. 35. 6d.

DIVINITY. 29

Hardwick.—a HISTORY OF THE CHRISTIAN CHURCH.
Middle Age. From Gregory the Great to the Excommunication
of Luther. Edited by WiLLiam Stusss, M.A., Regius Professor
of Modern History in the University of Oxford. With Four Maps
constructed for this work by A. KEITH JOHNSTON. Third Edition.
Crown 8vo. Ios. 6d.

For this edition Professor Stubbs has carefully revised both text and
notes, making such corrections of facts, dates, and the like as the results
of recent research warrant. The doctrinal, historical, and generally
speculative views of the late author have been preserved intact. ‘* As a
manual for the student of ecclesiastical history in the Middle Ages, we
know no English work which can be compared to Mr. Hardwick's
book.” —GUARDIAN,

A HISTORY OF THE CHRISTIAN CHURCH DURING THE
REFORMATION. By ARcHDEACON Harpwick. Third
Edition, Edited by Professor Stusss, Crown 8vo. 10s. 6d.

Maclear.—wWorks by the Rev. G. F. MACLEAR, D.D., Head
Master of King’s College School.

A CLASS-BOOK OF OLD TESTAMENT HISTORY. Eighth
Edition, with Four Maps. 18mo. cloth. 45. 6d.

** A careful and elaborate though brief compendium of all that modern
research has done for the tllustration of the Old Testament. We know
of no work which contains so much important information in so small
a compass.’;— BRITISH QUARTERLY REVIEW.

A CLASS-BOOK OF NEW TESTAMENT HISTORY, including
the Connexion of the Old and New Testament. With Four Maps.
Fifth Edition. 18mo. cloth. 55. 6d.

‘4 singularly clear and orderly arrangement of the Sacred Story.
fis work ts solidly and completely done.”’—ATHENAUM,

A SHILLING BOOK OF OLD TESTAMENT HISTORY,
for National and Elementary Schools. With Map. 18mo.
cloth. New Edition.

A SHILLING BOOK OF NEW TESTAMENT HISTORY,
for National and Elementary Schools, With Map. 18mo.
cloth. New Edition.

These works have been carefully abridged from the author's larger
manuals,

CLASS-BOOK OF THE CATECHISM OF THE CHURCH OF
ENGLAND. Third and Cheaper Edition. 18mo. cloth. Is. 6d.

“6 Tt is indeed the work of a scholar and divine, and as such, though
extremely simple, it is also extremely instructive. There are few clergy-
men who would not find it useful in preparing candidates for Confir-
mation ; and there arenot a few who would find it useful to themselves
as well,’ LITERARY CHURCHMAN.

A FIRST CLASS-BOOK OF THE CATECHISM OF THE
CHURCH OF ENGLAND, with Scripture Proofs, for Junior
Classes and Schools. 18mo. 6d. New Edition,

30 EDUCATIONAL BOOKS.

Maclear—continued.

A MANUAL OF INSTRUCTION FOR CONFIRMATION AND
FIRST COMMUNION. With Prayers and Devotions. Royal
32mo. cloth extra, red edges. 25.

‘*7t is earnest, orthodox, and affectionate in tone, The form of self
examination ts particularly good.” —JOHN BULL.

Maurice.—THE LORD’S PRAYER, THE CREED, AND
THE COMMANDMENTS. A Manual for Parents and School-
masters. To which is added the Order of the Scriptures. By the
Rev. F. DENISON Maurice, M.A., Professor of Moral Philosophy
in the University of Cambridge. 18mo. clothlimp. Is.

Procter.—A IIISTORY OF THE BOOK OF COMMON
PRAYER, with a Rationale of its Offices, By FRANCIS PROCTER,
sags Eleventh Edition, revised and enlarged. Crown 8vo,
Ios. 6d.

“* We admire the author’s diligence, and bear willing testimony to the
extent and accuracy of his reading. The origin of every part of the
Prayer Book has been diligently investigated, and there are few questions
of facts connected with it which are not either sufficiently explained, or so
referred to that persons interested may work out the truth for themselves.”
—ATHENAUM.

Procter and Maclear.—AN ELEMENTARY INTRO-
DUCTION TO THE BOOK OF COMMON PRAYER.
Re-arranged and supplemented by an Explanation of the Morning.
and Evening Prayer and the Litany. By the Rev. F. ProcTEer
and the Rev. G. F. MacLear. New Edition, 18mo. 2s. 6:

Psalms of David Chronologically Arranged. By

Four Friends. An Amended Version, with Historical
Introduction and Explanatory Notes. Second and Cheaper
Edition, with Additions and Corrections. Crown 8vo. 8s. 6d.
“* One of the most instructive and valuable books that has been published
Jor many years.’ —SPECTATOR.

Ramsay.—THE CATECHISER’S MANUAL; or, the Church
Catechism Illustrated and Explained, for the use of Clergymen,
Schoolmasters, and Teachers. By the Rev. ARTHUR Ramsay,
M.A. Second Edition. 18mo. Is. 6d.

A clear explanation of the Catechism, by way of Question and Answer.

“6 This ts by far the best Manual on the Catechism we have met with.”

—ENGLISH JOURNAL OF EDUCATION.

Simpson.—AN EPITOME OF THE HISTORY OF THE
CHRISTIAN CHURCH. By Witiiam Simpson, M.A,
Fifth Edition. Feap. 8vo. 35. 6d.

Swainson.—.A HANDBOOK to BUTLER’S ANALOGY. By
¢C. A. Swainson, D.D., Canon of Chichester. Crown 8vo. 15, 6:2,

DIVINITY. 31

Trench.—syNONYMS OF THE NEW TESTAMENT. By
R. CHENEVIX TRENCH, D.D., Archbishop of Dublin. New
Edition, enlarged. 8vo. cloth. 125.

Sezenth Edition, carefully revised, and with a considerable number of
new synonyms added. Appended ts an Index to the Synonyms, and an
Lndex to other words alluded to in the work, ‘‘He is a guide in this de-
partment of knowledge to whom his readers may intrust themselves with
confidence. Fits sober judgment and sound sense are barriers against the
misleading influence of arlitrary hypotheses.’ —ATHEN ZUM.

Westcott.—wWorks by BROOKE FOSS WESTCOTT, B.D.,
Canon of Peterborough.

A GENERAL SURVEY OF THE HISTORY OF THE
CANON OF TIIE NEW TESTAMENT DURING THE
FIRST FOUR CENTURIES. Third Edition, revised. Crown
8vo. 105. 6d.

“ Theological students, and not they only, but the general public, owe a
deep debt of gratitude to Mr. Westcott for bringing this subject fairly
before them in this candid and comprehensive essay..... As a theo-
logicat work it is at once perfectly fair and impartial, and imbued with
a thoroughly religious spirit; and as a manual it exhibits, in a lucid
form and in a narrow compass, the results of extensive research and
accurate thought. We cordially recommend it.’—SATURDAY REVIEW.
INTRODUCTION TO THE STUDY OF THE FOUR GOSPELS,

Fourth Edition. Crown 8vo. 10s. 6d.

“To learning and accuracy which commands respect and confidence,
he unites what are not always to be found in union with these qualities, the
no less valuable faculties of lucid arrangement and graceful and facile ex-
pression.” LONDON QUARTERLY REVIEW.

THE BIBLE IN THE CHURCH. A Popular Account of the
Collection and Reception of the Holy Scriptures in the Christian
Churches. New Edition. 18mo. cloth. 45. 6d.

“We would recommend every onewho loves and studies the Bible to read
and ponder this exquisite little book, Mr. Westcotts accownt of the
‘Canon’ is true history zx its highest sense’ —LITERARY CHURCHMAN,
THE GOSPEL OF THE RESURRECTION. Thoughts on its

Relation to Reason and History. New Edition. Fcap. 8vo.
45. 6d.

Wilson.—THE BIBLE STUDENT’S GUIDE to the more Correct
Understanding of the English translation of the Old Testament,
by reference to the Original Hebrew. By WILLIAM WILSON,
D.D., Canon of Winchester, late Fellow of Queen’s College,
Oxford. Second Edition, carefully Revised. 4to. cloth. 255.

“ For all earnest students of the Old Testament Scriptures it is a
most valuable Manual. Its arrangement is so simple that those who
possess only their mother-tongue, of they will take a little pains, may
employ it with great profit.” —NONCONFORMIST,.

32 EDUCATIONAL BOOKS.

Yonge (Charlotte M.)—scCRIPTURE READINGS FOR
SCHOOLS AND FAMILIES. By CuartotTe M. Yoncr,
Author of ‘‘ The Heir of Redclyffe.”” First Srrigs. Genesis
to Deuteronomy. Globe 8vo. 15. 6¢. With Comments. Second
Edition. 3s. 6d.

SECOND SERIEs,” From JosHua to SoLomon. Extra fcap.
8vo. Is. 6d. With Comments, 35. 6d.

THIRD SERIES. The Kincs and the PropHers. Extra feap.
8vo. 15. 6d. With Comments, 35. 6d.

Actual need has led the author to endeavour to prepare a reading book con-
venient for study with children, containing the very words of the Bible, with
only a few expedient omissions, and arranged in Lessons of such length as by
experience she has found to suit with children’s ordinary power of accurate
attentive interest. The verse form has been retained, because of its con-
venience for children reading in class, and as more resembling their Bibles ;
but the poetical portions have been given in their lines. When Psalms or
portions from the Prophets ilustrate or fall in with the narrative they are
given in their chronological sequence. The Scripture portion, with a very
fiw notes explanatory of mere words, is bound up apart, to be used by
children, while the same ts also supplied with a brief comment, the purpose
of which is either to assist the teacher in explaining the lesson, or to be
used by more advanced young people to whom it may not be possible to give
access to the authorities whence it has been taken. Professor Huxley, at a
meeting of the London School Board, particularly mentioned the selection
made by Miss Yonge as an example of how selections might be made from
the Bible for School Reading. See Times, March 30, 1871.

LONDON: R. CLAY, SONS, AND T.\YLOK, PRINTERS.

See