Full text of "The Journal of microscopy and natural science"

THE

OURNAL OF MICROSCOPY

AND

NATURAL SCIENC

THE JOURNAL OF

THE POSTAL MICROSCOPICAL SOCIETY,

KSitor :

ALFRED ALLEN.

Hon. Sec. P.M.S. ;

WITH SEVERAL ASSOCIATE EDITORS.

VOL VII. THIRD SERIES.
VOL XVI. OLD SERIES.

XonC)on :

BAILLIERE, TINDALL, & COX, 20 & 21 KING WILLIAM St., STRAND.

Batb:

I CAMBRIDGE PLACE.
1897.

BATH :
C. SEERS AND SON, PRINTERS, 2 ARGYLE STREET.

lp)teface.

VALEDICTORY.

Dear Friends, —

.^T^T is with the deepest regret that I write the word which
5J|«i appears above. The present part completes the
Sixteenth Annual Volume of the International
Journal of Microscopy and Natural Science, and during
the whole of those sixteen years I can honestly say that I
have spared no labour to make it worthy of the name it
bears. That I have succeeded in winning the approbation of
a great number of subscribers I have many letters to prove.
But for several years the result of the sales has not been
sufficient to pay the printer's bills, and this year I feel myself
so far in arrears that I dare go on no further.

I cannot close without tendering my best thanks to those
subscribers who have helped me by their kind support, and
especially those — and they are many — who have been sub-
scribers from the first ; also to those who have contributed
valuable papers, and have promised others for next year,
which I shall be obliged to "decline with thanks."

My thanks are also due to my publishers, Messrs. Bail-
Here, Tindall, and Cox, from whom I have always received
the greatest courtesy and kindness.

iv. PREFACE.

I trust the discontinuance of the Journal will not in any
way interfere with the steady and efficient working of the
Postal Microscopical Society, which will hold its Annual
Meeting at the Holborn Restaurant on Thursday evening,
the 2ist inst. All friends of the Society and of the Journal
will be welcome to attend. For particulars and Tickets
apply to me.

Yours very faithfully,

ALFRED ALLEN,

Editor.

I Cambridge Place^ Bath;
October, iSgy.

THE INTERNATIONAL

JOURNAL OF MICROSCOPY & NATURAL SCIENCE^^^^^^i^

THE JOURNAL OF THE POSTAL MICROSCOPICAL soCir^ ^^^^^^"^

^''Knowledge is not given us to keep, but to impart ; its
is lost in concealment y

[The Editor does not hold himself responsible for the views of
the authors of the papers published.]

preai&ential Hbbresa: '' Mbat i6 a Spiber ? ''

By Dr. J. S. Walker. Plate I.

HE scientific characteristics of an insect is a crea-
ture whose body is divided into three parts, has
two antennas, six legs, and passes through four
stages of metamorphosis ; but a spider is not an
insect. The spider belongs to the Araneidea, an
order of the Arachnida which, in common with
insects, is a sub-class of the Arthropoda. The
body of a spider is made up of two parts : the
cephalothorax and the abdomen.
There are nine orders of Arachnida : —
I. — Scorpions ( Scorpio dea), in which the respiration is by air-
chambers, and there is a post-abdomen ending in a claw.

2. — Cheliferidea, in which the respiration is by tracheae; the
abdomen is not distinctly separated, and the maxillary palpi have
two claws.

3. — Acaridea, with unsegmented abdomen, which is united to
the cephalothorax.

4. — Spiders {Araneidea\ in which the unsegmented abdomen
is distinct from the cephalothorax.

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. b

2 PRESIDENTIAL ADDRESS :

* 5 -Harvest Spiders ( Phalangidea), in which the respiration is
by trachea; the abdomen is not distinctly separated from the
cephalothorax, and the maxillary palpi have only one claw.

e.^Fhrynidea, in which respiration is by air-chambers, and
there is no post-abdomen.

^.—Solpugidea, in which the respiration is by trachea, and the
abdomen is separated from the cephalothorax.

8._Water bears (Ardisca), which have a vermiform body,
with four pairs of rudimentary limbs.

^,^Fentastomidea, which have a vermiform body, the embryo
only with two pairs of rudimentary hmbs.

Spiders {Aranetdea), an order of the class Arachnida.

The body of a spider is divided into an unsegmented cephalo-
thorax and a swollen abdomen, also unsegmented and attached
to the former by a narrow stalk. The cephalothorax is covered
above by a plate or carapace, more or less horny, while the abdo-
men is generally soft. The whole body is covered with hairs,

bristles, or tubercles. .

Attached to the cephalothorax there are four pairs of seven-
jointed walking limbs, which are usually long and slender, ending
in two claws, and to which one or more claws are sometimes added.
Above these are another pair of appendages, the pedipalpi, answer-
ing to the maxilla of insects ; their bases act as jaws ; and their
palpi are five-jointed, and in the female resemble simple legs, but
in the male their terminal joint is pecuUarly modified as a copu-

latory organ.

Above the mouth are the first pair of appendages, the falces or
chelicerae which consist of two joints and a powerful basal joint
grooved on its inner surface, also a claw-shaped terminal joint or
fang at the point of which the duct of a poison-gland opens.
These fangs, whose office is to catch and kill the prey, are, when
not in use, folded back into the groove of the basal joint.

The basal joint has generally a row of teeth on one or both
edges of the groove, and assists in eating, moving usually from
side to side. On the first margin of the cephalothorax are usually
eight, sometimes six or less simple eyes. The abdomen is always
larger or more swollen in the female. On its ventral surface in

WHAT IS A SPIDER ? 3

front are one or two pairs of respiratory apertures, and between
them the unpaired genital aperture.

The anus is placed at the extremity of the abdomen on the
ventral surface, and is surrounded by two or three pairs of spin-
nerets.

The mouth opens into a short oesophagus with horny walls,
whichg terminate in a dilated radiating, suctorial stomach, from
which are given off four or five pairs of caeca running into the
legs. The intestine is narrow, and opens into a short dilated
rectum, which receives a pair of much branched urinary or Mal-
pighian^canals. Salivary glands open into the anterior portion of
the oesophagus. The liver is very large and much branched,
opening into the intestines.

The vascular system is well developed. The blood is colour-
less. The heart is a chambered dorsal vessel, situated in the
abdomen, from which an aorta runs forward into the cephalothorax
giving off lateral arteries to the legs, jaws, brain, and eyes. In
the fore part of the cephalothorax, these arteries reunite, surround-
ing the brain, and forming the abdominal aorta, which runs back-
wards into the abdomen. The blood, after making its way
through the tissues and bathing the lung-sacs, re-enters the heart
by three pairs of lateral valves.

Respiration is effected partly by lung-sacs, composed of a
number of delicate lamellae and partly by tracheae or air-tubes,
There are one or two pairs of lung-sacs situated in the anterior
portion of the abdomen, and opening by slit-like stigmata. The
tracheae open by a pair of stigmata, further down, sometimes
quite at the extremity of the abdomen.

The nervous system is concentrated in a cerebral ganglion, or
brain, and a large ganglionic mass, situated in the thorax and sup-
plying nerves to the legs and abdomen.

Spiders possess an apparatus for the production of a viscid
fluid, which has the property of hardening into silk on exposure to
the air. This apparatus consists of numerous glands pouring
their secretions through fine pores on to the surface of the spin-
nerets, which are from two to four pairs of conical papillae placed
behind the anus. The apex of these spinnerets is surrounded by
stiff bristles and hairs, and is dotted with numerous horny tubes,

4 PRESIDENTIAL ADDRESS :

through the pores at the end of which the secretion escapes in
threads of extreme fineness, thousands of which are united to
form a single strong thread, as used in the web.

The spiders are all oviparous, and a single impregnation is
sufficient for several successive generations. The eggs are numer-
ous, and are usually enclosed by the female in a silken bag which
she carries about with her, or hides in her nest, or in some cases
attaches to stones, plants, etc. The young, when hatched,
resemble their parents in form, but they cannot spin nor capture
prey till after the first moult.

Spiders are found in every habitable portion of the globe, but
are larger and more abundant in warm climates. The males and
females live separately, and the latter are more frequently seen and
are considerably the larger. All are carnivorous, devouring living
prey, chiefly insects and other arthropods, sucking the juices and
sometimes swallowing the fragments. The, females are generally
ready to attack and feed on the males, even in the reproductive
season, and both sexes are fond of fighting, the vanquished being
devoured. They can support long fasts and remain torpid during
the winter. In making their webs, they accommodate themselves
remarkably to circumstances, displaying great perseverance, inge-
nuity, and intelligence. They carefully guard their eggs and are
affectionate to their young, which in some cases devour their
mother.

The webs sometimes form nets for the capture of prey, and
sometimes they are used partially or wholly as dwelling-places.
They descend by their silken threads head downwards, but climb
upon them head upwards, rolling the threads into a bundle during
the ascent. The thread cannot be used for the same purpose a
second time. When they wish to go from tree to tree, some let
go a thread in the direction of the wind, and when it has reached
the object they strengthen it, and pass over occasionally in this
way, travelling long distances without descending to the ground.
Young spiders of several families frequently float in the air, sup-
ported by a few threads of silk.

They are capable of some domestication. Pelisson, a prisoner
in the Bastille, had a pet spider, which came regularly at the
sound of a musical instrument to get its meal of flies. In former

WHAT IS A SPIDER ? 5

days both spiders and their webs were thought to be efficacious in
intermittent fevers, etc. The web is still used as a styptic.
Attempts have been made to render the silk surrounding the eggs
available for manufacturing purposes, but with little success, as
the silk is inferior in strength and lustre to that of the silkworm,
and cannot be wound. The poison of some of the foreign species
is very virulent and is dangerous to human beings. Spiders are
eaten by some tribes in various parts of the world, and are preyed
upon largely by birds and reptiles.

The order Areneidea is divided into two sub-orders : Tetrap-
neumones, with two pairs of lung-discs and two pairs of spinnerets;
and Dipneumones, with one pair of lung-discs and usually six or
eight spinnerets. The first sub-order contains only the family
Mygalidce,^ chiefly from the warmer parts of the world.

There are twelve varieties of spiders found in England : —

The British trap-door spider - Atypus Sulzeri.

The Bush „ „ - Anglena Nava.

The Bramble „ „ - Nereine rubella.

The Crab ; ,,. „ - Thomisus eristatus.

The Garden „ „ - Epeira diadema.

,, ,, „ - Dolimedes mirabilis.

The Ground „ „ - Lycosa Agretyca,

The Field ,, „ - Lyniphia minuta.

The Long-legged Grass „ - Tetragnatha extensa.

The Cellar „ „ - Tegenaria domes tica.

The House „ ,, - Aranea labyrinthica.

The Harvest „ „ - Phalangiuni cornutum.

The gigantic tropical species of Mygale live in trees and under
stones, etc., in a tubular silken dwelling, from which they issue
forth at night in pursuit of prey ; one species from South America
{Mygale avicularia, Fig. i) kills and devours small birds. The
trap-door spider ( Cteniza^ etc.) also belong to this family, living in
burrows in the ground, which are Hned with silk and closed with
an accurately fitting lid ; the only British species of the family
{Atypus Sulzeri) lives also in burrows, but does not construct a
trap-door.

The family Salticidce, or jumping spider, are small or of
moderate size, and abundant all over the world. They prepare

b PRESIDENTIAL ADDRESS:

no snare for the capture of their prey, but crawl up to it stealthily,
and capture it by a sudden spring.

Salticus scenicus is common everywhere in Britain on walls,
trees, palings, etc. ; another British species, Salticus formicarius
closely resembles an ant. The Lycosidce (see Fig. 2), or wolf
spiders, are also wandering spiders, catching their prey by running
It down. Some of the American species are very large, and all
are remarkable for ferocity ; some, as our common Lycosa ptraiica,
run on the surface of water and catch insects. The Tarantula
{Lycosa tara?itula), of Southern Europe, has acquired an evil repu-
tation, its bite being supposed to induce delirium and madness,
The Thofnisidce, or crab spiders, are so called from their short
body and long crab-like fore-legs, as well as from their habit of
running sideways; they are small spiders, numerous and widely
distributed, concealing themselves usually in herbage and flowers
(see Figs. 3 and 4).

The British species are numerous. The Tegenariidce, or
TubitelcB, form a very large family, the members of which weave a
large web with a tubular portion, which serves as a hiding-place.

The common house spider {Tege?iaria domestica) belongs to
this group, and also the water spider {Argyroneta aquatica), which
constructs its nest beneath the surface of the water. The family
Theridiidce is most numerous in the temperate parts of the Old
World. The species construct irregular webs in which to catch
their prey. The bite of one of the species, the Malmignatie
( Latrodedus Malmignattus ), common in the south of Europe,
especially in Corsica, produces serious and even fatal effects in
human beings.

The JipeirtdcB, or geometric spiders, construct beautiful, regu-
lar circular webs, with threads radiating from the centre and con-
nected by cross-threads. The typical genus Epeira contains the
common garden spider {Epeira diadefna) (see Fig. 5). In tropi-
cal America are several curious spiders of allied genera, which
have the abdomen more or less horny, and produced into spines
or long processes.

The harvest spiders, or harvest men, belong to a distinct order,
Phalangid(e.

In conclusion, it may be stated, this is solely natural history.

WHAT tS A SPIDER? 7

quite true ; but a good microscopist likes to know what to look
for, and what is most interesting, Some have made a study of
the web alone, and it is astonishing what a difference there is in
each family. Then, again, there has been some discussion how
the young of a spider is sustained. Mr. Samborn states that they
are suckled, and has seen milk oozing out of the spinnerets. Then
there are the spinnerets, the feet, which have two claws, and a
serrated appendage, so as to enable them to slide down on the
web. The head is exceedingly interesting ; the eyes are simple
ocelli and are a fascination to the embryologist ; also observe the
mandibles, a basal thick one, and a terminal one, curved and
sharply pointed, which is connected with the poison-gland.
Some authors consider these modified antennae. Then comes the
maxillary palpi, which terminates in the female in a small hook.
The tracheae and stigmata of the latter, and also the ovipositor.
There are four spinnerets on each side, thus showing that their
habits and structure offer a very wide scope for industrious work
to the microscopist.

I ought not to conclude my address without speaking of the
microscopical technique, which requires some practice and atten-
tion. Even to mount the feet of a spider, one difficulty is to get
them free from dirt and hair.

First, as to the bleaching. This may be done in several ways,
either with hydrochloric acid and chlorate of potash, or by a
simple solution of potash {Liquor Potasses of the British Pharma-
copoeia), or a solution of chlorate of soda or lime ; but any of these
chitinous arachnidse or acari must be watched, as if left too long
in solution they break up entirely. It is better to take the speci-
men out of the solution before it gets quite clear than leave it too
long, as whilst it is being washed it continues bleaching ; it
should now be washed in distilled water to free it from the drug,
then in a little spirit, then in some turpentine, and again in xylol
or spirit, and lastly in clove oil. For mounting I prefer the
balsam dissolved in turpentine, but great care must be taken to
touch the specimen with a small piece of filter paper whilst on
the section-lifter, so as to absorb and free it entirely from the clove
oil, or it will be cloudy when examined under the microscope.

SUPERNUMERARY APPENDAGES IN INSECTS.
EXPLANATION OF PLATE I.

Fig. 1. — Mygale avicula/ria, natural size.

,, 2. — Lycosa itquUina, the Wolf Spider.

,, 3. — Thomasis ahhreviatus, slightly magnified.

,, 4. — Thomasis lamio.

,, 5. — Epeira diadema, Common Garden Spider.

,, 6. — Tegenaria guyonii^ somewhat enlarged.

,, 7. — Dolomedes Jimhriatus, slightly magnified.

Qn tbe IFlature of Supernumerary Bppen^aoe0

in insects*

THE following evidence relates to about 220 recorded cases of
extra legs, antennae, palpi or wings, and speaking of cases
in which the nature of the extra parts could be correctly
determined, it is found that the following principles are followed
(amongst others) : —

I. — Extra appendages arising from a normal appendage usually
contain all parts found in the normal appendage peripherally to the
point from which they arise, and never contain parts central to
this point.

II. A. — Extra appendages of double structure are the common-
est. I. — Whether separate or in part compound, they consist of
a pair of coinplei7ie7itary parts^ ojie being right and the other left.
2. — Of the two extra appendages, that which is adjacent to the
limb from which they arise, is a limb of the other side of the body.
3. — If the pair of extra appendages arise from the a?iterior surface-
of the normal appendage, the surfaces which they present to each
other are structurally posterior ; if they arise posteriorly^ the adja-
cent surfaces are anterior ; if they arise vefitrally, the adjacent
surfaces are dorsal, etc.

II. B. — A single extra appendage is rarely perfect, i. — If it
arises from the body, it is formed as an appendage of the side on
which it is placed.- 2. — If it arises by peripheral division of an
appendage, the parts central to the point of division are commonly
right or left as the case may be, while the peripheral part may be
a symmetrical and complementary pair.

These phenomena are important as an indication of the phy-
sical nature of bodily symmetry, and in their bearing upon current
views of i-he character of germinal processes. — W. Bateson.

Journal of Microscopy,, 3^.^ Ser.Vol, 7, Plate 1

F. P/7//hps,Sc.

Joupnal o| MicPo;gcop^, 3p3. Se:p. , Vol. 7, PL 2.

'.-"^ «A^, »•«. J. "^O" ^J^c/-^.

■¥'F

Norman Collie, Ph.D., F.R.S.

(Kindly lent by the Editor of " The British and Colonial Druggist. '' )

^be Diecoveri? of Hrgon anb Ibelium/ f| V^

By J. Norman Collie, Ph.D., F.R.S.,
Professor of Chemistry to the Pharmaceutical Society.

IN the early days air was looked upon as an elementary sub-
stance, and for many hundreds of years it was considered one
of the four elements — earth, air, fire, and water being the
four. These elements were not looked upon quite in the same
light as we look upon elements nowadays. They had more to do
with the properties of substances in general, and not with actual
elementary substances, and it was not till about two hundred years
ago that definite ideas began to be collected on the subject of air,
and it was due to an English chemist — I think many of the great
discoveries in chemistry have been due to English chemists — that
our ideas on the subject of air first began to take a definite form.
It was towards the end of the seventeenth century — over two hun-
dred years ago — that Robert Boyle, an Englishman, first of all
published a work on the air, and the various subjects which related
to the air. I have a slide here which I should like to show you of
a portrait of Robert Boyle himself. I should like to show you
the portraits of several of those chemists who worked on air, and
who brought the knowledge that we possess of air up to the
beginning of this century. Robert Boyle, the first I will mention,
was a chemist who investigated not only air, but a great many
other substances besides, but he was particularly interested in air
and its various properties. He had rather vague notions, how-
ever, on the subject of air, but he was one of the first chemists
who combated the old idea of earth, air, fire, and water being ele-
ments, and he specially points out that there is no reason why we
should in any way limit the number of elementary substances to
four, and no reason why air should be an elementary substance ;
in fact, he seemed to think there were a great many different kinds
of air, as they were called in those days — " gas " being a much
later term, and that the different kinds of "gases" he investigated

* Lecture delivered before the Pharmaceutical Society. F'rom the Phar-
maceutical Journal.

10 THE DISCOVERY OF ARGON AND HELIUM.

depended upon the various properties of the substances from
which they were produced.

The next portrait of a chemist who had to deal with air is also
that of an Englishman named John Mayow. He was a doctor
who lived about the same time as Robert Boyle, and he also
published some work on the subject of air. He proved that
there was no doubt one particular substance present which he
called fiery air, and that it was due to this fiery air, which was
present in ordinary air, that enabled substances to burn. This
was of very great importance, but was lost sight of for more than a
hundred years. Mayow also pointed out that this particular air,
which he called fiery air, was present also in nitre or saltpetre,
and in this way he discovered facts which were re-discovered very
much later by a French chemist named Lavoisier at the end of
last century.

The next EngHsh chemist who had to do with air, and also
made a very large number of experiments, was a clergyman of the
name of Stephen Hales. He was more interested in the rise of
sap in plants and similar substances, and investigations of that
description, but he also made a very large number of experiments
on heating substances in closed vessels, collecting various airs or
gases, as we call them now, above water. He also proved that
probably air contained more than one particular kind of air, and
he examined the different airs which were produced by the decom-
position of all sorts of substances by heat and otherwise, collected
them above water, and made investigations on them, but, again,
his investigations seem rather to have been lost sight of, and not
to further science in any very great way. Air was still looked upon
by the chemist as an elementary substance, and not a substance
which was composed of different kinds of matter.

About a century later than these three chemists came some
more English chemists, who still further advanced our knowledge
on the subject of air. This is a portrait of Dr. Black. Dr. Black
lived in Edinburgh, and he was the first to point out that there
was present in the air what he called fixed air, because he was able
to absorb this air from the atmosphere by means of such substances
as caustic potash, and also quickhme. He thought by this process
the air became fixed or absorbed by these solid substances — the

THE DISCOVERY OF ARGON AND HELIUM. 13

potash and the lime — and proved that after it had been fixed or
absorbed in that manner it could be produced again either by the
addition of acids or by heating. He was the first to prove con-
clusively that a substance named carbonic acid, or, as he called it,
fixed air, was present in the atmosphere, and this was really one of
the first noticeable facts in our knowledge of the air.

This is a portrait of another Scotch chemist, of the name of
Rutherford. He did not, however, study chemistry very com-
pletely, and he did not study it all his life, but he is the discoverer
of one of the constituents of air, which he called mephitic air,
and we now know it by the name of nitrogen. It is that gas
which is present in the largest proportion in air ; about 80 per cent.
of air, or four-fifths, being composed of this gas nitrogen, and
Rutherford was the first to point out that this mephitic air was
different from the fixed air that Black obtained ; also, that it would
not support combustion, that substances would not burn in it, and
also the more important fact that it would not support life — that
animals died in it. Rutherford, therefore, was the discoverer of
nitrogen. After having absorbed the other gases in the air by
means of various heated substances which absorbed them — such
as oxygen and so on — he obtained this gas nitrogen.

The next portrait is of another English chemist of the name of
Dr. Priestley. He was the discoverer of the other chief consti-
tuent of air. About 120 years ago he obtained oxygen in the
pure state for the first time, and proved that this gas, which he
called dephlogisticated air, was present in ordinary air, and that it
was due to this gas that animals could live in ordinary air, and also
that substances burnt very much more brilliantly in pure oxygen
or pure dephlogistic air than in ordinary air. That brings us to
the end of the last century, and these are the people who had, in
fact, most to do with the discovery of the various gases in the air.
Black discovered the carbonic acid, Rutherford the nitrogen, and
Dr. Priestley the oxygen, the oxygen and nitrogen being the two
most important constituents in the atmosphere.

This portrait is a portrait of the French chemist Lavoisier, and
perhaps in a way he was greater than all of them. It was Lavoi-
sier who gathered up all these scattered details ; it was Lavoisier
who put them together ; and from the absolute — one might almost

14 THE DISCOVERY OF ARGON AND HELIUM.

call it — ruin of the old theory (the phlogistic theory) he built up a
new edifice on which the modern system of chemistry stands. He
explained, first of all, the way we now accept the true theory of
combustion. He showed us how it was that substances were
burnt in air, and what happened when they did burn in the air —
that they absorbed the gas oxygen which was present there, and
in doing so gave out light and heat, and he built up the whole
theory of combustion such as we understand it at the present day.
He took up all the facts the other chemists had discovered, and
turned them to his own use and that of chemists in general.

The last portrait I have to show you is that of another English-
man. This was Henry Cavendish, who was by far the most accu-
rate worker of them all. Cavendish without doubt obtained this
gas that 1 am going to tell you about, named argon, and later on
I will tell you how he did it. At present I will only mention that
he was the discoverer of the composition of water as well. His
analyses of air are almost as accurate as the most accurate analy-
ses ever made, and they were made by the most incomplete and
most inaccurate pieces of apparatus.

All this brings us to the beginning of the century, and clears
the way for what I have now to tell you about the discovery of the
gas, argon. At the beginning of the century people thought that
they knew all about the air, and that there was no more to know ;
that all the gases had been discovered, and that there were no more
to discover ; but it was only two years ago that there suddenly
burst on the world this wonderful discovery of the gas, argon. Of
all the places to find it, in the air was the most unlikely, for, as I
have said, every chemist thought the very last had been said on
the subject of ordinary air. The reason that argon had not been
discovered before was that all analyses of air had been conducted
in the following way : —

First of all, impurities such as water vapour and carbonic acid
had been got rid of by absorption ; there was then left merely
pure oxygen and nitrogen, then the oxygen was absorbed, and the
nitrogen was left, no easy method of absorbing nitrogen being then
known. The residue was supposed to be pure nitrogen, but, as it
so turned out, the residue was by no means pure nitrogen — it con-
tained over I per cent, of this gas, argon, which had never been

THE DISCOVERY OF ARGON AND HELIUM. 15

separated out from the nitrogen before. This discovery, like a
great many discoveries, although it burst upon the world and
people heard nothing about it until they suddenly heard that the
gas had been discovered, was a discovery which had been built up
step by step. Few discoveries are made suddenly ; they usually
come by hard, persistent scientific work, and argon is no excep-
tion to that rule, whilst helium is no exception either.

The work which led up to this was due to some excessively
accurate work that Lord Rayleigh had been carrying out on the
actual densities or weights of given volumes of various gases.
About ten years ago he started weighing oxygen and hydrogen,
trying to get them as pure as possible, and to find out exactly to
the third and fourth place of decimals what a given volume of
these gases weighed. After he had done this, in the year 1892 he
prepared nitrogen from a great number of different sources, and
he found that so long as he prepared nitrogen by chemical pro-
cess, by the decomposition of ordinary nitrogen compounds, the
nitrogen always weighed exactly the same. When, however, he
prepared his nitrogen from air by purifying the air and absorbing
everything in it except the nitrogen, this nitrogen present in the
air did not weigh quite the same, but very nearly the same, as the
nitrogen obtained from other sources. These results would, in
the hands of most people, have meant nothing ; but Lord Ray-
leigh had spent many years at the work, and he was quite certain
that this was due to something he could not explain. First of all,
he thought it was the chemical impurities that were present, and
he tried his best to get rid of every impurity, still he found that
this nitrogen which was obtained from the air was too heavy by a
very little, but still it was too heavy, and he was extremely puzzled
and could not find out what the reason of it was ; so he put the
matter in the hands of Professor Ramsay ; he and Professor
Ramsay joined forces, and then came the discovery of argon. It
was perfectly simple. It was the nitrogen which now had to be
absorbed. A residue was left, and that residue was argon. The
difficulty, however, was to absorb nitrogen, because no substance
easily absorbs nitrogen, and the way in which it was done was by
means of magnesium. Magnesium absorbs nitrogen very readily
at a red heat, and after it has been heated for a long time, and the

16 THE DISCOVERY OF ARGON AND HELIUM.

nitrogen gas passed round and round over the magnesium, then
finally there is a residue left, and that residue is argon. I have a
slide here showing the various densities of these gases that Lord
Rayleigh obtained.

. The way in which nitrogen was absorbed afterwards, when it
got down to a small bulk, is shown on the next slide. The water
in the vessel contains caustic soda. There are two platinum
points connected by wires to an apparatus for making sparks. If
gas containing the last traces of nitrogen, which is difficult to be
got rid of by means of magnesium, is introduced into such an
apparatus with oxygen, and the electric spark be allowed to pass
between the two points b and d^ the nitrogen will combine with
the oxygen and form a substance which can be absorbed in the
soda solution. That is the way of getting rid of the last traces of
nitrogen ; and there are then left only argon and oxygen ; the
oxygen can be absorbed by any ordinary re-agent, such as phos-
phorus.

The next sHde shows a rather more elaborate apparatus for
dealing with a larger quantity. The electrodes here dip down so
as to touch the surface of the liquid soda. That gives a larger
space, and combination takes place more readily. To keep it cool
Lord Rayleigh had occasionally a spray of soda running up to
cool the top of the vessel. It is an improved apparatus for work-
ing on larger quantities.

The next slide shows a still further improvement in the appa-
ratus. This is one in which the electric spark is allowed to play
between the two tubes. The section shows the bath, which is
cooled by means of water.

Next comes a diagram which shows the apparatus that Profes-
sor Ramsay used first of all for the absorption of nitrogen. It
contains various absorbents for absorbing nitrogen and other
gases present in ordinary atmospheric nitrogen. Starting at A by
letting water run in, the gas is sent through the whole apparatus
into B^ and when it gets there it can be sent back again into A^
and so it may be passed backwards and forwards. In the various
parts of the apparatus are phosphorus pentoxide to dry the gas,
copper to get rid of the oxygen, copper oxide to get rid of the
hydrogen, soda and lime to get rid of the acid vapours, and

THE DISCOVERY OF ARGON AXD HELIUM. 17

metallic magnesium ; thus, all the various impurities in the gas
are absorbed, and finally only argon is left.

The next diagram represents apparatus for conducting opera-
tions on a larger scale. It is an automatic arrangement for making
the gas circulate round and round, and is a very effective appara-
tus for the manufacture of argon on a large scale.

After argon had been obtained in this way, the difficulty was to
find out how it differed from other substances, and unless chemists
had been able to make use of the electric discharge through a gas
they never would have been able to find out that this argon was
different from ordinary nitrogen or any other element. A great
many substances are able to give out light when they are sub-
jected to the electric discharge, and I will now show you three
extremely beautiful experiments, by means of apparatus lent me
by Mr. Jackson, of King's College. The first will show you how
a solid emits light when submitted to an electric discharge, the
second a liquid, and the third a gas, and in each case you will find
that we get a very beautiful light given out. In this vessel I have
some ordinary lime, made by igniting bits of calc spar. I will
connect it with a battery producing sparks, and when I turn on the
current we shall find this solid produces a most beautiful light.

The next experiment deals with a liquid, a solution of sulphate
of quinine, which you will see gives out a beautiful blue light.

Finally, I will take a gas and show you how we can, by passing
an electric discharge through it, get it to light up just in the same
way as the soHd and the liquid. It is a long tube filled with air ;
in its normal condition it gives no light, but it is connected with
an air-pump, and as I gradually exhaust the air you will see how
the light begins to appear, and increases as the vacuum becomes
more perfect. When I turn the stopcock and allow air to enter it
diminishes, and finally disappears. If it had not been for the
power of lighting up gases in that way by electricity, it would have
been extremely difficult to detect argon in small quantities.

All gases can be lit up by means of the electric currer^t, if
they are exhausted to a sufficient degree of rarity. I have several
tubes here containing different gases, which I should like to show
you. Some contain air, one contains hydrogen, and one carbonic
acid, and each gas gives a different kind of light.

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. c

18 THE DISCOVERY OF ARGON AND HELIUM.

Now I will show you a tube of the gas argon. Argon can be
made to give out two different kinds of light when excited by-
means of the electric current — one a purple and the other a beau-
tiful blue. I will first show you the purple. That tube is the
historic argon tube. It was lent me by Professor Ramsay, and is
the one which was used for the measurement of the argon lines
by Mr. Crookes, and is the one which has been shown at all the.
different exhibitions of argon. It owes its beautiful colour to its
long life. There are very few argon tubes which give anything
like the brilliancy of this ; in fact, I believe there are none, because
there are none so pure. By this incessant violent knocking of the
atoms of the gas against the sides of the tube and against each
other, it becomes purer and purer, as the other gases get absorbed
by the electrodes, which are made of magnesium, so that this is a
perfectly pure sample of argon inside the tube. Now, I want you
to see the wonderful change that takes place in the argon light the
moment I put a Leyden jar with a spark-gap into the circuit. It
now becomes a beautiful blue colour.

This light was examined by the spectrum and found to give
out various lines, which showed that it was different to any other
gas. It was also found on weighing the gas that it was heavier
than ordinary nitrogen, being twenty times heavier than hydrogen,
whilst ordinary nitrogen is only fourteen and a half times heavier,
and therefore the discovery was put on a firm basis at once.

Now, we come to the other new gas, helium, which was the
direct outcome of this piece of work on argon. The gas which is
given off when certain minerals are dissolved in acids is usually
carbonic acid, and there was a curious mineral which Professor
Ramsay's attention was called to, which is found in America and
also in Sweden, called cleveite. An American chemist named
Hildebrand had worked at it and got a large quantity of gas from
it, and on examining it carefully he came to the conclusion that it
was nitrogen. Professor Ramsay's attention was called to it in
order that possibly he might be able to prove that it was argon,
for it was a very curious thing for a mineral to give off nitrogen.
Professor Ramsay, immediately he heard of it, obtained some of
the mineral, dissolved it in acid, heated it, and got the gas off.
It was on a Friday afternoon that a tube was filled and looked at

THE DISCOVERY OF ARGON AND HELIUM. 19

through the spectroscope. The first thing we noticed was a mag-
nificent briUiant yellow line. The next week Professor Ramsay
was going over to France to give an address to the Academie des
Sciences in Paris on argon. When on the Friday afternoon we
examined this gas from the cleveite, the brilliant yellow line at
first suggested the element sodium, for it looked exactly like the
sodium line, which is a yellow line, or rather a double one. I at
once said the tube must be very dirty. Professor Ramsay said,
however, "it is perfectly clean, but it is perfectly easy to test it.
Produce the yellow sodium line and compare it, and if the two
lines coincide then it is sodium ; if not, it is something else."
This was done, and at once we saw that it was not the sodium
line, for it was on one side of it, and at once helium was sugges-
ted. The reason for that was, that about thirty years ago, during
an eclipse of the sun, Professors Frankland and Norman Lockyer
made a large number of photographic and spectroscopic examina-
tions of the corona — i.e.^ the extreme outside of the sun, the part
which is seen only during ecUpses, where great volumes of incan-
descent gases are shot out hundreds of thousands of miles in
great tornadoes. These examinations of the sun's corona revealed
a brilliant yellow line. This yellow line was unknown at the time
and corresponded to no known element on the earth, so Norman
Lockyer suggested calling it helium. It had been seen at this
particular part of the sun. It was of interest, because only the
very lightest gases such as hydrogen existed there, and here was
another gas, which, presumably, was as hght as hydrogen — existing
in the corona of the sun together with hydrogen.

Nothing more was known of it until, in this gas prepared from
cleveite, this yellow line appeared, and we could not be certain
that it was helium until we had actually measured the wave-length
of that particular line. Professor Ramsay took it up to Mr
Crookes that night, and on the Saturday morning Mr. Crookes
measured it, and found it was almost, if not quite, identical with
the line of helium, D^ ; so that Professor Ramsay was able to
telegraph over to the French chemist (Berthellet), saying he was
coming over to give the lecture on argon, and that he had dis-
covered another new element, helium, which he would bring over
with him.

20 THE DISCOVERY OF ARGON AND HELIUM.

This element, helium, has a most magnificent, brilliant yellow
spectrum ; in fact, the spectrum of helium, and the colour it gives
out when subjected to the electric discharge are by far the most
beautiful of any gas that I know; far more briUiant than hydrogen;
far more brilliant than any ordinary gas ; and if we examine it by
means of the spectroscope it almost seems as if the whole of the
most striking spectra had got mixed up together and put into one
tube. There is a beautiful red line, which is as brilliant as the
best red line in the hydrogen ; there is a magnificent, intensely
bright yellow line; and, moreover, there are green, blue, and
purple ones. All these lines exist in the helium in the most won-
derful manner. If you look at it through a spectroscope you see
a most magnificent spectrum.

There is but little more time to tell you about these gases —
that is, about their general properties, and I have also not told
you about the preparation of argon by Cavendish, but that will
not take very long. What he did was this :— He actually absorbed
all the nitrogen by means of sparking, and I have here a diagram
of the apparatus he used. It is perfectly marvellous that he was
able to carry out the experiment with a couple of wine-glasses, a
bent tube, and some potash lees, and an ordinary electric machine,
and that was all Cavendish had when he produced argon. He
took the nitrogen and put it into the bent tube above mercury ;
he then introduced, by means of a pipette, certain quantities of
oxygen, and sparked them with a wire introduced here from an
ordinary electrical machine. In that way he was able to get the
very feeble electric spark which could be obtained from the elec-
trical machine of those days to pass from the level in one tube of
gas down to the liquor in the other tube. Then he added more
oxygen and more nitrogen, and went on thus keeping the machine
going for about two months, probably for twelve hours a day, and
was able to get the gas absorbed slowly ; and, lastly, by a little
liver of sulphur in this tube he absorbed the last traces of oxygen,
and there was a minute bubble of gas left, and so accurate had he
been with his measurements that he said : " After I had done this
there was left a small bubble, but whether that was due to another
constituent of the atmospheric air or not I was not able to say.
At any rate," he said, " if this is a new constituent of the atmo-

THE DISCOVERY OF ARGON AND HELIUM. 21

sphere, it is only present in the proportion of the i/T2oth part of
the original atmosphere that I took." He was very nearly correct.
It is a little over i/iooth. About i per cent, of the atmosphere
is argon, and Cavendish said it could not be more than i/i20th.
If Cavendish had been able to use such electric apparatus as we
have nowadays, and such tubes as we have, that gas would have
given all the spectra we now get from argon. But spectroscopy
was not invented until about eighty years later, by Bunsen and
Kirchoff.

This diagram shows the apparatus used for the liquefaction of
argon. Some argon was sent to a Polish Professor, Olszewski, who
has worked on the Hquefaction of gases. He, by surrounding a
tube filled with argon with liquid oxygen made to boil in a vacuum,
succeeded not only in liquefying, but in soUdifying argon. Argon
boils at - i87°'o C, and becomes solid at - i89"^"6 C.

This table shows the boiling points of different gases. - 246^0.
is the temperature at which hydrogen boils; nitrogen - 194^0.
HeHum is not given here because it was not discovered when this
table was prepared, and helium is the only gas which up to the
present has not been liquefied. The absolute zero temperature,
below which theoretically nothing can be cooled — that is to say,
the temperature at which we suppose any substance ceases to
possess any heat at all, and, therefore, cannot lose any more heat
— is - 273° C. Professor Olszewski has cooled helium by boiUng
liquid hydrogen down to - 266^ or - 267S, within a few degrees
of absolute zero, and yet has not liquefied it, even under pressure,
and therefore it probably will not be liquefied.

Just one word in conclusion about the discovery of these gases.
I mentioned at the beginning that no discovery is made except by
hard work, and that no discovery is made suddenly. The whole
of our knowledge about argon and helium came from hard work,
and it came step by step ; one thing led to another. No one
would ever have thought of looking at cleveite as a mineral from
which helium might be discovered, unless first of all argon had
been discovered, and no one would have thought of argon unless
Lord Rayleigh, by accurate work, had found that the nitrogen that
came from air was a little too heavy. He would not have done
that unless he had been instigated to perform some rather more

22 THE DISCOVERY OF ARGON AND HELIUM.

accurate scientific work than had been done by others ; he merely
repeated other people's work on the density of gases, because he
wished to get more accurate determinations, in order that from
those data other data might be obtained.

I think that probably the discovery of argon and helium,
although at present they are of no commercial use — and I may say
that people often ask me what is the use of argon and helium, but
as it is difficult to answer such questions, I do not try — from a
scientific point of view, helium probably will be of the very
greatest use. It is a gas which has the most peculiar properties.
It is a gas which we call monatomic — that is to say, its atoms are
the same as its molecules ; the molecule and the atom are identi-
cal. Again, the electric conductivity of helium is very much
greater at ordinary pressure than that of any other gas that is
known. (Several experiments were here shown to prove this, the
electric spark traversing a helium tube in preference to one of air
or hydrogen, or passing through a longer distance.) Helium is
ten times as good a conductor of electricity as ordinary air.
Hydrogen up to the discovery of helium was the best conductor,
but it is inferior to helium. Another curious point about it is that
it is extremely light, and diffuses through a porous septum much
more rapidly than it has any business to do. It diffuses in a per-
fectly abnormal way. Therefore I think this gas ought to be very
useful to the physicists. They often talk about a perfect gas, and
now I think they have it, and I hope they will be able to make
something out of it. Chemists have done much with it, and now
it is the turn of the physicists.

I have now taken up enough of your time, and hope I have
been able to make myself sufficiently plain, and that you now
know a little about the discovery of these two gases, argon and
helium.

To Catch Earthworms. — According to Nature^ earthworms
may be obtained in any quantity without the labour of digging by
watering the ground with a solution of sulphate of copper of a
strength of i per cent. This will bring the worms to the surface
almost immediately. Soap-suds are said to produce the same effect.

[ 23 ]

Bnti6b 1bi?5racbnit)a^*

By Charles D. Soar. Part VII. Plate III.

IN the present paper we purpose considering two somewhat
similar genera of Hydrachnidce, the first to which we shall
direct attention being the Genus Limnesia (Koch).
1842. — C. L. Koch, Ubersicht des Arachnidensy stems, p. 3, p. 27.

Mites belonging to this genus are characterised as having the
body soft-skinned ; legs well-supplied with swimming hairs ; fourth
pair of feet without claws ; three genital suckers on each side of
the genital fissure ; epimera in four groups ; palpus not chelate ;
mandibles in two portions ; eyes wide apart.

The members of this genus differ from any others which have
been previously considered in being without ungues to the tarsus
of the fourth pair of legs ; it is a genus easily recognised when
once seen. There is only one other genus that is likely to be
mistaken for it, viz., Teutonia (Koenike) ; but the difference is
very observable when once it has been pointed out. We shall
describe the genus Teutonia later on in this paper. All the species
of Limnesia with which I am acquainted show very little difference
in structure, the male and female being very much alike, the only
remarkable feature being the shape of the genital plates, as shown
in Plate III., Figs. 3 — 5. In size the males are a Httle smaller than
the females, but they do not possess that peculiar spur on the
fourth pair of legs, so commonly met with in Arrenurus, AxoJia,
and others, to which attention has been drawn in previous papers.

There are several British species ; some are very common, and
exhibit a great variety of colours, ranging from deep red to pale
yellow ; they can be found almost anywhere in ponds, lakes, or
rivers. They will live a long time in confinement ; I have fre-
quently kept them, both in summer and winter, for several months
at the time, but I have not been so fortunate as to have any ova
deposited either in the tanks or in the tubes in which I have
kept them.

They are very much like the spider family in the way they prey
on the other life in the same tank, and when that is exhausted

24 BRITISH HYDRACHNIDiE.

they prey on one another. It is not safe to put other soft-bodied
Hydrachnids into the same tank, unless they are intended as food,
for the Lifftnesia make very short work of them, and extract their
life's blood in a very short time ; Eylais extendens appears to be a
particularly dainty morsel, and specially adapted to their taste.

Not having been successful in breeding, although I have kept
the adults so long at the time, I am unable to give a figure of the
larva. Dr. George tells me he also has had no better fortune than
myself, although he has kept them in confinement for a consider-
able length of time ; it may be they do not deposit ova at all.
Anyhow, it is a question which yet remains to be answered. Per-
haps accident will at some future time solve the problem for us.

The next stage, the " nymph," I have taken a great many times
in this form. They are much like the adults, but have only four
genital suckers instead of six, as shown in Fig. 5.

Linmesia longipalpis (Koch).
1835 — 4^- — C- L* Koch, Deutschla7ids Crust. ^ etc., p. 7, Fig. 8.

There can, I think, be no mistake about this species being
correctly named longipalpis., for the palpi is certainly very long ; in
more than one specimen I have found the palpi longer than the
first pair of legs. Koch gives a beautiful little figure of this mite,
but it is coloured yellow, whereas all those specimens which I have
found have always been bright red, with pale blue legs. But colour
only gives us a variety ; it does not constitute a species. So we
must not consider the colour, but look only to the structure for
the identification of species.

The length of body is aboui 7/i5oths of an inch. The only
district in which, to my knowledge, it has been found in Britain is
N. Wales. Mr. Scourfield sent me several specimens from Llyn-
Guetnar, Dolgelly, N. Wales, in June, 1895, and I took about a
dozen more specimens in Llyn-Padarn, and in a small lake near
Newborough, Anglesey, when collecting with Mr. Scourfield in
September, 1896. It may be very common in all lake districts,
but up to the time of writing, the above are the only localities in
which I have known them to be met with.

Journal of Microscopy, 3^- Ser. Vol. 7, Plate 3.

BRITISH HYDRACHNID^. 25

Genus VIII. — Teutonia (Koenike).
1890. — F. Koenike, Archiv.f. Naturgesch., p. 75.

The characteristics of this genus are : — Body soft skinned ;
legs well supplied with swimming hairs ; fourth pairs of feet without
claws. Three genital suckers on the inner edge of the genital
plates on either side of the genital fissure ; epimera in four groups;
palpi not chelate ; mandibles in two portions ; eyes wide apart.

This genus, as has been already remarked, is very closely
allied to the Limfiesia—io much so, indeed, that it can easily be
mistaken for it; but it will be noticed in Figs. 7 — 8 that the
genital suckers are on the inner side of the plate, and not on the
plate itself, as is the case in Figs. 3 — 4 of Linmesia. The poste-
rior pair of epimera are also more square, as shown in Fig. 6.
The rostrum is also projected a little more forward, and the palpi
are attached to that part, much in the same manner as we shall
find in Sperchon (Kramer). In Limnesia will be noticed on the
fourth pair of feet, or rather the tarsi, a long spine projecting
outwards, which I have never seen in Teutonia.

Teutonia prii?iaria (Koenike).
1890, — F. Koenike, Archiv.f. Naturgesch.^ pp. 76 — 80, PI. V.
This is, I believe, the only species known of this genus up to
the present time. It is pale yellow in colour, with brown mark-
ings. I first took it in 1893 at Bealings, Suffolk; but not having
at that time seen Koenike's paper, referred to above, I believed it
to be a strange species of Lim?iesia. In June, 1895, I took two
more specimens at the same place, and this year in North Wales
I took several more, so in all probabiUty it is fairly common ; but
I have never taken it in any of the usual collecting grounds round
London. It measures about i/25th of an inch in length. The
palpus has the same peg-like process which is always found on
Limnesia (see Fig. 9).

EXPLANATION OF PLATE III.

Limnesia longipalpis (Koch).
Fig. 1. — Dorsal surface.
,, 2. — Ventral surface.

26 MORPHOLOGY OF SPECIES

Fig. 3. — Genital area of female.
,, 4. — Genital area of male.
,, 5. — Genital area of nymph.

Teutonia primaria (Koenike).
,, 6. — Ventral surface.
,, 7- — Genital area of male.
,, 8. — Genital area of female.
,, 9. — Palpus of female.

©baeivations on tbe flDorpbolog^ of Specice
of tbe (5enu6 TTlIey.

By Harold Wager, F.L.S. Plates IV. and V.

THERE are two species of C//ex to be found in England,
U. EuropcEUs and U. nanus, and a variety of the latter
known as Gallii, both common in most parts of the
country, and familiar plants to all who are acquainted with our
heaths and commons. Although apparently so distinct in the
structure and general appearance of its vegetative organs, we may
compare the genus Ulex with the genus Cytisus, which it resem-
bles in many respects in regard to its morphological characters.
In Ulex we have what may be regarded as an extreme modifica-
tion of vegetative structure in response to the environment, \vhich
in Cytisiis is not so far advanced, and in the following pages we
shall endeavour to describe this modification, how it has probably
been brought about, and under what conditions.

The commonest species, U. Europceus, is distributed very
widely, being found in the w-estern parts of the old world from
north-west Africa to Shetland Islands, and ascending to a height
of 2,ioo feet in Wales. It is a shrubby bush, about three to five
feet high, with a very compact habit when grown in the open, but
a rather straggling habit when grown in the shade. This compact
habit is due, in large part, to the regular mode of branching which
it possesses and to the development of short spiny branches in the
axils of the leaves. The plant likes deep and somewhat loamy

OF THE GENUS ULEX. 27

soil, and is sensitive to cold. This can be readily seen by the
number of plants killed during our cold winters. After the severe
winter of 1894 — 5 so large a number of dead bushes could be
seen in all the more exposed situations that it was a matter of
considerable astonishment to those who imagined that such stiff,
tough plants must be very hardy.

The general structure of the vegetative organs presents many
features of interest ; the leaves are reduced practically to spines,
and their function of assimilation is to a large extent replaced by
that of the stem. The internal structure of the spiny leaf remains
similar, however, to that of ordinary foliage leaves, except that it
has a tendency to develop palisade tissue all round. The leaf is
leathery, the epidermis is very thick, and the stomata are slightly
sunk in it. In the axils of nearly all the leaves short branches
occur, of varying length, each terminated by a strong spine.
These may be termed the prwiary spiny branches ; they grow for
one year only, and produce in most cases a small number of leaves
which may have secondary spiny branches in their axils. In
addition to these branches, others are produced, with a similar
structure, but longer and having a different origin. They are
always developed between the foliage leaf and the primary spiny
branch. They generally terminate in spines, but in some cases
continue to grow at the apex by means of an apical bud. They
are called accessory branches. When these branches are fully
formed, the primary spiny branch and the leaf at its base turn
brown and die, as can be easily observed by anyone who cares to
take the trouble to examine a furze bush of more than two years'
growth.

If we examine a branch of Furze two years old, we shall see
that it is covered with accessory branches from the base to the
apex, but they are longer and more numerous near the apex, where
they form a tufted group radiating in all directions, than lower
down. In a favourable specimen all the upper leaves bear such
accessory branches in their axils. Nearly all the primary spines
and leaves at the bases of the accessory branches on such a stem
will be found to be withered, with the exception of those which
are fairly well exposed to light. Very few of the accessory
branches continue to grow for more than one year. They nearly

28 MORPHOLOGY OF SPECIES

all terminate in spines. In one specimen taken at random, out
of fourteen well-developed branches, only one terminated in an
apical bud. Even when present, however, the terminal buds do
not often pass through the winter, beirig generally so sensitive to
cold that they are killed by a fairly sharp frost. Some few occa-
sionally are seen to survive the winter, and these continue to grow
during the next year. Where accessory branches are not visible
or apparently not devc'loped, rudimentary branches will be found
in the form of buds placed in the same position, between the
foliage leaf and the primary spine, ready to grow should an oppor-
tunity be given them, and protected against injury by being care-
fully packed between the two and surrounded by scale leaves
covered with hairs.

The accessory branches have the same structure as the mam
axis. They bear in their turn primary spines and accessory
branches, and these latter again branch in the same manner. As
they never grow very long and generally only for one year, we get
the compact habit of the plant, which has been already mentioned.

The flowers are generally borne on the primary spines, but at
the apex of the accessory branches they are produced directly in
the axils of the leaves in place of the primary spines ; and on the
primary spines themselves the flowers replace secondary spines.
They are only formed on those parts of the plant which are more
exposed to light than the others. This may be illustrated by
observations on a short branch taken at random from a furze
plant. In this case there were no flowers at all at the base, as
this part of the branch was completely surrounded by other
branches. J'he first flowers were produced at a distance of 12 cm.
from the apex on the primary spines. Starting, therefore, just
below this, and taking branches here and there as we pass upwards
to the apex, we find a regular progression in the number of flowers
produced, as the primary spines become more fully exposed to light :

Branch i. — Seven leaves, all with secondary spines in their
axils. No flowers.

Branch 2, — Eight leaves ; the lower six with spines, the two
upper ones with flowers in their axils.

Branch 3. — Seven leaves ; first five with spines, the sixth and
seventh with flowers.

OF THE GENUS ULEX. 29

Branch 4. — Seven leaves ; one to three with spines, four to
seven with flowers.

Branch 5. — Ten leaves ; one to three with spines, four to ten
with flowers (Fig. 14),

Branch 6. — The nearest branch to the apex with five leaves,
all with flowers in their axils.

The secondary spiny branches also bear leaves with flowers or
tertiary spiny branches in their axils, and these appear to follow
the same rule. In Branch 2, for example, I found the secondary
spiny branches in the axils of leaves one to three, with two foliage
leaves, right and left at the base, and in the axils of each a spine.
On the secondary spines, four to eight, I found two foliage leaves
on each, in the same position as above, and in the axils of all
were flowers. On Branch 5 I found that, of the secondary spiny
branches, one to three, each produced two foliage leaves at the
base, and the third branch a third foliage leaf in addition. One
leaf on each of the spines numbered one and two had a tertiary
spine in its axis ; the other leaf a flower. On spine No. 3 the
two lower leaves had flowers, the upper leaf none, being only
very small.

The primary spines vary considerably in length according to
their position, being longest on those parts of the plant which are
well exposed to the light and shortest on those parts which are
hidden by the surrounding branches. If a Furze bush be examined
carefully, it will be seen that the length of both primary spines and
secondary branches varies regularly according to the amount of
exposure to light, and, further, the arrangement of the various
primary, secondary, and tertiary spines and leaves is such that the
largest surface of assimilative tissue is exposed to light with the
smallest amount of overlapping, so that the light can filter down
from the higher to the lower portions of a branch without any
serious interruption.

According to Wydler, two cases of leaf arrangement obtain on
the primary spines. In the first case, there are two leaves at the
base standing opposite one another, and at right angles to the
foliage leaf, in the axil of which the spine is borne (see Fig. 14).
These are followed by a leaf higher up on the branch, and on its
upper surface exactly midway between these two (Fig. 14).

30 MORPHOLOGY OF SPECIES

From this leaf starts a i/3rd cycle of leaves, which may pass into
the ^/S cycle.

In the second case, the median leaf, as above, initiates at once
a 3/8 arrangement without passing through the 1/3 cycle. I find,
however, that this arrangement is not constant. It varies as the
length of the spine and the number of leaves it produces. There
is a tendency to the production of leaves arranged in whorls or
groups of two or three, which modifies considerably any given
cycle.

The arrangement of the leaves on the accessory branches
differs somewhat from this. According to Wydler there are two
cases. In the first case, the four first leaves are produced in pairs
at right angles to one another; then follows a 1/3 cycle, suc-
ceeded by the 3/8 arrangement. In the second case, the 3/8
arrangement follows at once on the two pairs of leaves. My own
observations generally support Wydler's, but in some cases the
number of pairs of leaves at the base is more than two, and in
other cases the leaves are not developed in pairs at all, but start
at once with a spiral arrangement.

The general structure and arrangement of the leaves are the
same in I/, nanus, var. Gallii, as in U. EuropcBus, and calls for no
detailed description here. For comparison, I will shortly describe
a branch, 80 mm. long, taken from among about sixteen others,
growing in a group on the main axis of a fairly strong plant of
several years' growth. Starting at the base were six short spathu-
late leaves, about 3 mm. long, with no branches in their axils.
These were growing in a shady position. Then followed a number
of spathulate leaves, with a slightly developed spine at the apex.
On following these leaves upwards, they were found to vary in
length from 4*5 mm. to 7 mm., at the same time becoming more
distinctly spiny, and were succeeded by leaves gradually decreas-
ing to 2 '5 mm. in length, with a well developed spiny character
and the ordinary structure of a spiny leaf. Of these leaves
twenty-nine had well formed spines in their axils, on the upper
five of which flowers were produced. Above these twenty-nine
leaves were thirteen others close to the apex with rudimentary
spines in their axils, one only possessing a flower. The lowest
spine on the branch was 6 '5 mm. long and had two lateral lea/es.

OF THE GENUS ULEX. 31

in the axil of one of which a short spine was produced. The
uppermost spine on the branch was 12 mm. long, being more
exposed than the lower one, and had four foliage leaves, in the
axils of three of which secondary spines were found and in the
fourth a flower. The arrangement of the leaves, both on the
spines and on the accessory branches, was very similar to that
which has been described as occurring in U. Etiropceus, and
exhibited the same kind of variation.

This variation in the arrangement of the leaves is difficult to
explain, being probably due to many causes, some of which we
can perhaps indicate, and some of which we are ignorant. It is
determined, first of all, by their development at the apex of the
stem, the new leaf appearing just where there is the greatest
amount of space between those previously formed. This explains,
of course, the formation, at the base of a branch, of leaves in
pairs, the two first leaves being developed opposite each other and
the succeeding ones exactly midway between them. It depends,
secondly, upon the size of the leaves, variation being introduced
when the newly developed leaves vary in size from those preceding
them. And variation is also probably caused when flowers are
produced in the axils of the leaves instead of spines.

The size of the leaf mainly depends, of course, upon the con-
ditions which have caused their reduction to spines, but it also
depends to a slight extent upon their situation on the plant, the
spiny character not being so well developed in leaves formed in
the shade as in those exposed directly to light. We shall, however,
consider this question again when dealing with the development
of the seedling.

The anatomical structure of the stem is correlated with the
reduction of the leaves to spines. As the assimilative function of
the leaves is reduced, that of the stem becomes more perfect. In
order to eff*ect this, both the normal stems and the spiny branches
are longitudinally ridged, so that the amount of stem surface
which becomes thus exposed is in extent considerably more than
doubled. If we examine a transverse section of 'a primary spine
under the microscope, we shall notice that the ridges are very pro-
minent, with the hollows between them very pronounced (see
Fig. 12). The ridges are supported by bands of strengthening

32 MORPHOLOGY OF SPECIES

tissue, radiating from the central part of the spine, thickened on
the outer edge (Fig. 12, S). In the hollows between the ridges
we find two or more rows of thin-walled cells, full of chlorophyll
corpuscles. This is the assimilative tissue (Figs. 12 and 13, a).
The epidermis surrounding the stem possesses a very thick cuticle,
and the stomata are slightly sunk below the surface. The stomata
occur almost exclusively in the hollows of the stem and are pro-
tected by hairs (Figs. 12 and 13). Just inside the chlorophyll
layer is a single row of large thin-walled cells, with very little
contents and no chlorophyll corpuscles; next to these are the
endodermis and pericycle, followed by a ring of vascular bundles,
one to each ridge (Figs. 12 and 13). The structure of the normal
stem resembles this, but the chlorophyll tissue is not so well
developed, and secondary thickening takes place at an early stage,
so that a complete ring of vascular tissue is seen instead of sepa-
rate bundles.

The presence of the assimilative tissue in the hollows of the
stem only has been explained as preventing a too-rapid evapora-
tion of water, such as takes place when large leaf-surfaces are
exposed. It has been suggested that this modification is therefore
a safeguard against drought, but Kerner is of opinion that it is
merely a contrivance to prevent the wetting of the stomata. That
this in part explains the modification is probable ; but it seems to
me that, in common with many other contrivances of a similar
nature — such as rolled-up leaves, needle-shaped leaves, etc. — it is
mainly a protection against excessive transpiration. But, so far as
I know, the Furze plant, although it is grown in a rather dry soil,
is never or very rarely exposed to excessive dryness, and therefore
this provision against drought may appear to be of very little use.
But drought is not the only cause of excessive transpiration.
Cold winds promote transpiration, and at the same time tends to
retard the absorption of moisture by the roots. The Furze plant
grows in exposed situations generally, and would thus be very
liable to be affected in this manner were it not for the reduction
of the leaves and the modification of the stem. In fact, even now
the F'urze is unable to stand very severe cold, and nearly all the
young developing buds are killed during the winter. But without
committing ourselves to one explanation or the other, we may, I

OF THE GENUS ULEX. 33

think, say that this modification of the Furze plant is a protection
against excessive evaporation, whether from drought or cold winds.

But what are we to say of the spiny character ? It has been
pointed out that spines are the direct outcome of the environment
of drought. Henslow brings forward many examples to support
this from various writers, who all agree that under extreme condi-
tions of dryness plants tend to produce spines, while when spiny
plants are grown with an abundant supply of water they tend to
lose their spines. A French observer — M. Lothelier — found that
on growing a spiny plant, Berberis vulgaris, in a damp atmosphere,
it bore no spinescent leaves ; but in a perfectly dry atmosphere it
produced spines only. His figures are certainly very striking and
show this clearly.

My own observations on naturally grown seedlings of Ulex, to
some extent, support this view, for I have found that taking a large
number of seedlings from two equally exposed but different soils,
one humus and the other stony loam, that the percentage of
seedlings with trifoliate leaves is not only greater on humus soil
than on the stony loam ; but the spinescent character is more
quickly assumed in the latter case than in the former, and as the
humus soil holds more moisture, as is well known, than the stony
soil, it appears as if this were the direct cause of it. Nevertheless,
it would not be fair to state definitely that this is so, for there may
be many causes at work of which we are ignorant, and one which
would at once occur to any careful observer, is whether nutrition
does not produce some effect upon young seedlings, the difference
between the nutritive values of humus soil and stony loam being
at once apparent.

At the same time, observations which I have made upon seed-
lings kept indoors, well exposed to light, in a sandy soil, and well
supplied with water, although perhaps not very conclusive, owing
to the short time during which I have been able to continue them,
tend to support the view put forward by other observers that the
presence of moisture tends to reduce the spinescent character.

A seedling of Ulex Europceus, which had germinated in the
antumn, and had already produced fourteen trifoliate leaves, was
taken the following spring and planted in a flower pot, in sandy
loam. It was' kept in a warm room well exposed to light for many

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. d

84 MORPHOLOGY OF SPECIES

months, and was well-supplied with water. The seedling to start
with was two centimetres long. The main axis continued growing
and developed first of all eight more trifoliate leaves, then six di-
foliate ones, and then a number of thin, linear, lanceolate leaves,
with only a slight rudiment of a spine at the apex. The stem
remained thin, and the leaves never became stiff or spiny. This
main axis grew to about twenty centimetres long while it was
under my observation. In the axils of the upper leaves, spiny
branches were produced, but the spines never became prominent,
whilst the lateral leaves borne upon them were generally well
developed, and in many cases no spine was formed at all. Three
of the lower trifoliate leaves developed branches which were
respectively 5, 6, and 7J cm. long. Neither of them had termin-
ated their growth by a spine, and on all of them the leaves
remained thin, flexible, and only very feebly spined. In the axils
of only a few of these leaves were any spiny branches produced,
and these were only very rudimentary, and in no case was the
spine developed. The following details of one of these branches
may be interesting : —

Leaves i to 9. — No branches at all in their axils.
„ 10 and II. — The two lateral leaves only of the

spiny branches developed.
„ 12 and 13. — A small bud only in their axils.
„ 14 and 15. —Two lateral leaves only, no spine.
„ 16 to 27. — Two lateral leaves only slightly

spiny, but no main spine.

Under normal conditions, as I was careful to observe, such a
seedling would have developed a very definite spiny structure
during the few months I had it under observation. The seedling
was ultimately killed by an exposure to a couple of months'
drought, but the observations are sufficient to show that a good
supply of water and non-exposure to cold tends to retard the
development of the spiny nature of the plant, not only by
reducing the stiff spiny nature of the leaves, but also by reducing
the stiff spiny nature of the stem, and allowing a much greater
development of length at the expense of sturdiness and the
development of leaves which are capable of fulfilling the leaf

OF THE GENUS ULEX. 35

function to a much greater degree than the ordinary leaves of
a Furze plant. It was interesting to note that the leaves, instead
of standing straight out, as is the case normally, were curved
downwards in such a way as to expose the largest amount of sur-
face to the light.

Another seedling which I took and planted at the same time
was a second year's seedling from the same place. During its
first year this seedling had developed a main axis ten cm. long,
with twelve trifoliate leaves, four difoliate ones, and thirty-one
linear, lanceolate spiny leaves. In the axil of each leaf, except the
trifoliate ones, was a spiny branch with a well-formed spine. On
being kept in a warm room with a plentiful supply of water, there
appeared, in the axils of six of the lower trifoliate leaves, primary
branches, which reached the length of 30, 27, 17, 10, 2*5, and
1*5 cm. respectively, being much longer than they would have
become under normal conditions. These had already commenced
to grow when the seedling was planted, but were then extremely
short. The shortest of the branches, 1*5 cm. long only, had
developed when the seedling was planted two opposite, linear,
lanceolate leaves, followed by seven leaves of the same shape
arranged spirally. On subsequent growth in the house trifoHate
and difoliate leaves only were developed, but the growth of this
branch was soon stopped through being shaded by the others.

On the branch 27 cm. long there were, to start with, two oppo-
site linear leaves at the base, followed by five linear leaves in a
spiral, and then six trifoliate leaves, with very short internodes,
also in a spiral, the branch being only i cm. long. On being
brought into the house it commenced by producing twelve trifoli-
ate leaves, with gradually increasing internodes ; then fifty Hnear,
lanceolate leaves, gradually becoming narrower towards the tip,
but none of them developing any stiffness or any pronounced
spine. In the axils of the three lowest trifoliate leaves no branches
were developed. In the axils of the next three leaves primary
branches were developed which did not terminate in spines, but
in a bud. In the axils of the other trifoliate leaves and the linear
leaves, rudimentary spiny branches were produced, without,
however, any very pronounced spinescent character. The four
remaining primary spiny branches presented the same modifica-

36 MORPHOLOGY OF SPECIES

tions, with only slight differences of detail. It is to be noted
that the branches just described are not accessory branches, but
primary spiny branches, which very rarely, in ordinary cases,
reach such dimensions as 27 or 30 cm. of length. In a seedling
which had obtained a year's start, therefore, the direct effect of the
altered environment was to produce a reduction of stiffness and
spines, and an increase in the number of functional leaves.
The same effect was visible upon the accessory branches developed
on other parts of the seedling.

It will be remembered that primary spiny branches were devel-
oped in the axils of all the linear, lanceolate leaves of the original
seedling, and in each case an accessory bud was formed between
the spiny branch and the leaf in whose axil it was produced. Five
of these accessory branches reached a length of 2, 3, 4, 6, and
7 "5 cm. respectively. The two longest were developed near the
apex of the seedling, the terminal bud of which had apparently
been killed by the previous cold winter, as it did not continue its
growth. These branches bore linear, lanceolate leaves, in the
axils of a few only of which were developed very rudimentary
spiny branches. No trifoliate leaves were developed, but in all
other respects they resembled the branches already described.

This seems conclusive as to the effects of the environment in
reducing the normal character of the Furze bush, reduction of
spiny branches, and larger development of leaf surface in propor-
tion ; but in order to test it still further, I took a seedling which
had already had two years' start, having stood the very hard win-
ter of 1894 — 5, and brought it into the house, where it was
exposed to a uniform temperature, and supplied with plenty of
water. The main axis of this seedling above ground was 3 cm.
long, the terminal bud having been killed probably by the hard
winter of 1894. Seven lateral branches were developed on the
axis, which reached lengths respectively of 7, 3, 6, 3, 6, 7*5, and
5*5 cm. They were developed in the axils of trifoliate leaves.
All these branches developed linear, lanceolate leaves, with well
developed spiny branches in their axils ; and in the 5 larger
branches each axil developed an accessory bud. Of these acces-
sory buds, four to six developed on each branch to lengths of from
I '5 to 16 cm., seven of them being more than 7 cm. in length;

OF THE GENUS ULEX. 37

the other accessory branches were very short, or remained unde-
veloped. Each of these branches repeated the same modifications
as regards reduction of the spiny nature and sturdiness that we
have already considered.

I think we may safely consider therefore that the environment
has a considerable effect upon the spine-producing nature of the
Furze plant and that it is largely reduced by a plentiful supply of
moisture. The production of spines however has been explained
as a protection against animals, and whether drought has caused
this directly or not, there is no doubt that, in the majority of cases,
the spinescent character is of great value to the plant against the
attacks of animals. That there is a necessity for the Furze to be
protected in this way is seen in the fact that, even in its present
condition, if properly prepared so as to destroy the spines, it
serves animals as food, In the article "Agriculture_" in the Ency-
clopcBdia Britannica. for example, we find that the young shoots of
Furze are palatable and nutritious as food for cattle and horses.
It must be chopped and bruised to destroy the spines. This is
done now by a variety of machines ; formerly by beating it upon
a block of wood with a mallet. It yields valuable food in poor
dry soils (it also increases the amount of Nitrogenous matter in
the soil, as do other leguminous plants, by means of the tubercles
on its roots). Cows fed upon it give much rich milk free from
any unpleasant flavour. It may be sown and treated as an ordin-
ary green crop, and a succession of cuttings may be obtained
from the same field for several years. Professor Muir also, in his
work on "Agriculture," states that stock like it very much when
crushed and chopped, and it is particularly useful because it is
ready for consumption in the winter when green food is usually
scarce.

Mr. Henslow, in his book. The Origin of Plant Structures,
seems to take it that the development of the spiny character is
due entirely to drought, and does not admit that selection due to
animals has had any part in it. The two great factors, according
to him, are the tendency to variability and the environment. But,
even could one admit that the reduction in the leaves is due
directly to drought without the mtervention of natural selection,
spines could not be explained in that way. Spines, as such, do

38 MORPHOLOGY OF SPECIES

not protect plants against drought, neither can we regard their
production in their present perfect form as a mere accident due to
the larger development of the woody character of a plant. It
seems to me that, at present at any rate, the only explanation of
spines is that they are a protection against animals ; and this has
been brought about by natural selection, those seedlings which
survived being just those best able to protect themselves from
animals. In other words, the reduction of the succulent tissues,
the hardening of the mechanical elements, and a consequent ten-
dency to spininess, although due primarily to variabihty and
environment, have been gradually perfected and made permanent
by natural selection. It is quite true, nevertheless, that a favour-
able environment tends to reduce the spiny character of a plant ;
but it would probably take many years of very careful artificial
selection before the Furze plant could be brought back again to
the ancestral form possessing only trifoliate and non-spinescent
leaves.

The development of the Furze seedling offers many interest-
ing features. The seed germinates in the normal way by sending
down a primary tap-root, first of all, into the soil, and a plumule
with two fleshy cotyledons upwards into the air. The cotyledons
are forced through the soil by the arching of the hypocotyl (Figs.
I to 7). They are thick and fleshy, white or light green in colour
on the under surface, dark green above, oval in shape, and with
no hairs. In a normal seedUng the cotyledons are succeeded by
one or two pairs of trifoliate leaves, covered with hairs (Figs. 7
and 8). These are generally curved upwards at the margins, and
thus grooved or concave on the upper surface. They are thick
and shiny and of a dark green colour. The trifoliate leaves are
succeeded by several pairs of spathulate leaves, broader at the top
than at the base ; they are both described by Lubbock as petio-
late. The arrangement of these first leaves varies. They may be
alternate and spiral, but are usually opposite to each other and in
pairs. The spathulate leaves are succeeded by leaves which gra-
dually become less and less broad at the apex, until finally we get
a narrow-pointed leaf tapering from tht base upwards (Fig. 10).
At the same time, a spine, which is already present in a rudiment-
ary condition in ihc trifoliate leaf, becomes more and more deve-

OF THE GENUS ULEX. 39

loped until it forms a disagreeable puncturing instrument at the
tip of each leaf.

In some seedlings this normal course of leaf development is
not followed ; in fact, a very great variety in the number and
arrangement of the leaves is found. The following are a few
examples of seedlings, collected on Woodhouse Ridge, Leeds,
which will show how largely they vary : —

No. I. — Seedling germinated in autumn, locm. long; collected
in April after a mild, damp winter. Had grown in stony loam.

I St to 5th — Trifohate leaves.

6th — Bifoliate leaf, with small lateral leaflet.

7th — Trifoliate leaf.

8th — Spathulate leaf.

9th to 13th — Linear leaves with spines.

There were spines in the axils of all these leaves ; and in all,
except three of the trifoliate ones at the base, there were acces-
sory buds between the leaves and the spines.

No. 2. — A seedling grown under the same conditions as No.
I, but 7*5 cm. long.

I St to 4th — Leaves in pairs, opposite, spathulate, and the
other leaves were spirally arranged.

5 th — Bifoliate leaf, with a small lateral leaflet.

6th — Spathulate leaf.

7th — Spathulate, with a very small lateral tooth.

8th — Spathulate leaf.

9th and loth — Spathulate leaves, but narrower; prickle at top
becoming more pronounced.

nth and 12th — Slightly spathulate, with stronger spines.

13th and 14th — Leaves tapering from base upwards and ter-
minating in strong spines.

All these leaves, except one or two lower ones, had spines in
their axils, but no accessory buds could be seen.

No. 3. — A seedling, 2*5 cm. long, germinated in the autumn;
collected in April. Had been growing in humus soil, well exposed
to light.

I St — Two leaves opposite, paired, trifoliate ; subsequent leaves
not in pairs, spirally arranged, but with very short internodes.

3rd — Leaf with one lateral leaflet.

40 MORPHOLOGY OF SPECIES

/^th — Spathulate.

5 th to 9th — Trifoliate.

loth — Bifoliate leaf, with small lateral leaflet.

nth to 17th — Trifoliate leaves.

1 8th to 20th — Bifoliate.

2 1 St — Spathulate.

22nd to 29th — Slightly spathulate.

There were no spiny branches in the axils of any of these
leaves.

No. 4. — Seedling, 4-0 cm. long, grown under same conditions
as No. T, and in same soil.

ist — Two leaves opposite : one difoliate, the other spathulate.

3rd and 4th — Spathulate, nearly opposite, but not quite on
same level.

5th and 6th — Trifoliate, nearly opposite, not quite on same
level. Subsequent leaves arranged spirally.

7th to 9th — Trifoliate.

loth to 30th — Linear, gradually becoming normal, and termi-
nating in spines.

Spiny axils were developed in the axils of all the leaves after
the 7th.

No. 5. — Seedling grown under the same conditions as No. 4,
6*5 cm. long.

ist pair of leaves, opposite, trifoliate.

2nd pair, not quite opposite, trifoliate.

3rd to 9th — Trifoliate.

loth to 1 2th — Spathulate.

13 th — Bifoliate.

14th and 15 th — Trifoliate.

1 6th — Bifoliate.

17th to 32nd — Spathulate, gradually passing into the linear
form, with well developed spines.

In the axils of all the leaves after the 5th were spiny branches.

No. 6. — Seedling, i"5 cm. long, growing in humus soil, germi-
nated in autumn and collected in March of following year. Had
twenty leaves, all trifoliate.

No. 7. — Grown under same conditions as No. 6. Had thirty
leaves, all trifoMate.

OF THE GENUS ULEX. 41

Seedlings were also observed of the second year's growth,
growing under the same conditions, with more than one hundred
trifoliate and difoliate leaves.

These observations are not only interesting as showing the
very considerable variation existing among seedlings of Ulex^ but,
as I have already mentioned, afford some evidence of the effect of
the environment upon the production of the spiny character;
those seedHngs which were grown upon humus soil having begun
to develop the spiny character much later than those grown upon
the stony loam.

The primary axis of a seedling stops growing, according to
Buchenau, at the end of the first year. In all the seedlings which
he examined at this stage, he found that the tips were dead, and
the same thing was repeated on the side-shoots. He supposes
that the young buds at the apex get killed by the frost. My own
observations show that this is not so, however. In many seedlings
I have found that both the main axis and the lateral shoots con-
tinue to grow a second year, but very rarely for a third year. It
is probable, however, that it is only during a fairly mild winter —
such as that of 1895-6 — that any considerable number of apical
buds escape destruction.

The trilobed form of the primary leaves in seedlings of Ulex
is compared by Buchenau to that observed in seedlings of Cytisus ;
and Winkler also has a paper on the comparison of the two seed-
lings. According to these observers — and, generally, my own
observations agree with theirs — the seedlings of Cytisus develop
four- to six-stalked trifoliate leaves, the first few pairs being in pairs
and opposite to each other, and the others arranged spirally. But,
just as in Ulex^ this development varies. Spathulate leaves are
sometimes first developed, then trifoliate ones, and these again
may suddenly or gradually pass over into the spathulate form.
There is no reduction of the leaves to spines. It is interesting,
also, to compare the adult plant of Cytisus with that of Ulex. In
the former the lower leaves on a branch are stalked and trifoliate ;
the upper ones are sessile and often reduced to a single leaflet.
The simple leaves are produced, as in Ulex, by the loss of, first,
one lateral leaflet, then the other. Ulex differs from Cytisus only
in the fact that trifoliate leaves are formed much less frequently,

42 MORPHOLOGY OF SPECIES

and only on the branches of young plants as a rule, but they are
developed in the same position, at the base of the branch. We
have, in fact, the same kind of modification in both plants, the
stems being ridged, and the leaf surface reduced by a gradual
modification of a trifoliate to a simple form, and this has gone
some steps further in Ulex than in Cytisus by the further reduc-
tion of the simple leaves to spines. This all points to a common
ancestry for the two plants, and their development from a form in
which all the leaves were trifoliate, as occurs at the present day
in closely allied species, such as the common Laburnum of
our gardens, in which all the leaves are trifoliate from the
beginning.

The formation of a number of trifoliate leaves on the seed-
lings and young branches of Ulex is probably, then, a survival of
the ancestral structure, and when a large number are produced we
may regard it as a reversion to the ancestral condition brought
about by the favourable conditions of the environment. The
development of trifoliate leaves may, indeed, be favoured by many
circumstances.

Thus, exposure to light favours the production of leaves with a
larger surface, and this in the case of Ulex^ owing to the ancestral
tendency, is brought about more readily by the formation of
trifoliate leaves than by an increase in the size of the simple leaf.
At the same time, the stem is reduced in length and the leaves
appear near together at its apex in the form of a rosette, as occurs
in many plants grown in exposed situations. This increase in the
size of the leaves by exposure to light takes place only to a certain
extent, however ; drought tends to reduce them, so that we should
expect to find trifoliate seedlings more abundant in places exposed
to light, and with sufficient supply of moisture than in those places
where one condition is present without the other. Again, it is
probable that the reduction of the leaf-surface is in part brought
about by cold, which prevents the due absorption of water by the
roots, and consequent necessity for economy of the supply already
obtained. And as humus soils are warmer than loamy soils, we
should expect to find, what is actually the case, that trifoliate
seedlings are more abundant on the former than on the latter.

OF THE GENUS ULEX. 43

We may sum up the various causes which appear to have a ten-
dency to modify the seedlings of the Furze plant as follows : —

The reduction of leaf-surface and production of spines is
favoured by : — Drought ; shade of other plants ; cold winds and
soils ; hereditary tendency to production of spines (due to animal
selection).

Increase in the leaf-surface and production of trifoliate leaves
is favoured by : — Moisture ; exposure to light ; warmth ; ancestral
tendency to produce trifoliate leaves.

In the adult plant the conditions under which they are grown
may tend to modify the earlier leaves developed on the lateral
branches ; but those formed later, whatever may be the conditions,
always develop the spiny character.

It is interesting to note that seedlings intermediate between
those which possess a large number of trifoliate leaves and those
which have linear leaves only, are constantly found in which the
struggle between those conditions which tend to produce trifoliate
leaves, and those which tend to form only linear leaves, is seen in
the fact that they show all sorts of stages in the reduction of tri-
foliate leaves to simple ones, with very few of the former, and
never quite reaching the latter. One such seedling, collected in
the shade, had the long internodes, characteristic of seedlings with
linear leaves ; but the lower thirty leaves were neither trifoliate
nor simple, but were in all stages of transformation of the former
into the latter. Such cases are not uncommon, though it is rare
to find such a striking example.

We have already seen that all the young leaves and leaflets on
a seedling are curved upwards at the margin to form a furrow
extending down the middle of each leaf to the stem, or, in the
case of the lateral leaflets of a trifoliate leaf, to the median furrow
of the leaf. They are also curved downwards in a very decided
manner, becoming in many cases parallel to the stem. It appears
exactly as if this were an arrangement by which water is enabled
to run off the plant and prevent it getting wet. On trying some
experiments, however, to test this, by pouring water on to a seed-
ling from a height, it was found that very little water indeed
escaped this way, and that it was nearly all conducted, by means
of the furrows on the leaves, to the stem, and then delivered in a

44 MORPHOLOGY OF SPECIES

Stream down the roots. Many experiments were tried ', seedlings
of different sizes were taken, but all with the same result. It may
be useful to give a few details of one or two of the experiments.

Experiments with a seedling i inch high, with trifoliate leaves :

I. — Water was poured from a spoon, or allowed to run out of
a pipette, at a height of 4 to 6 inches. None of it dropped from
the tips of the leaves. It was all conducted to the root.

2. — Water poured in same manner on the leaves at one side
of the plant. About ^rd of it fell off in the form of drops, the
remainder was taken down to the root.

3. — Allowed water from watering pot to fall from a height of
about 2 feet on to the plant. Nearly all the water which fell on
the plant went to the root.

The leaves become easily wetted, but when quite dry the first
few drops fall off the leaves quite easily. The same experiments
were tried with a seedling three inches high, having trifoliate leaves
at the base and linear leaves at the top, with the same results. It
was noticed in this case that if, by any chance, a drop of water
fell off any of the upper leaves, it was caught by the lower ones,
and by them conducted to the root. A seedling two inches long,
with linear leaves, allowed very little water to escape any other
way than by the roots. On allowing water to play on a plant with
ten branches from five to eight inches long, from a watering pot,
most of that which fell on the plant was conducted down the stem
and delivered in a large stream at the roots ; very little escaped in
any other way.

The following experiment was tried to show how easily and
rapidly the plant conducts water to the root even when applied
under great pressure : — A seedling two and a half inches long was
taken with linear leaves, the diameter of the seedling about ^ of
an inch in its widest part. A pipette with an indiarubber cap was
taken, filled with water, and brought to the apex of the seedling,
so that the opening was placed near the centre of the young leaves.
The indiarubber cap was then pressed suddenly and strongly, and
the water expelled, but none escaped laterally; it was all delivered
at the roots. On sending water in laterally the same result was
obtained.

The leaves seem to take up the water and conduct it to the

OF THE GENUS ULEX. 45

Stem by means of the capillarity of the furrow on the upper
surface. A drop of water placed on the tip of a leaf, which was
curved downwards, did not fall off, but was immediately taken
away up the furrow to the stem. It was even found that on
dipping the apex of a leaf in water that it was slowly conducted
away and delivered in drops at the root.

These experiments seem to show the seedling — growing, as it
often does, upon stony and sandy soils — is enabled, by means of
the collecting power of its leaves, to ensure that its roots shall
have a chance of absorbing whatever water may fall upon it, and
so to some extent overcome the difficulty of the water supply in a
soil from which water is so quickly drained.

In conclusion, we shall see^ I think, that this study of the
Furze plant, incomplete as it is, affords an insight into the contri-
vances by which Nature is able to overcome the difficulties of
various kinds to which plants are subject during their develop-
ment, and shows how quickly they may respond to changes in the
environment, and so produce variations ready, if necessary, to be
further improved and strengthened by natural selection.

, Literature.
I. — Wydler. Kleinere Beitrage zur Kentniss einheimischer Gew-

achse. Flora, i860, p. 23.
2. — Buchenau. Die Sprossverhaltniss von Ulex. Flora^ i860,

p. 449.
3. — Winkler. Die Keimpflanze des Sarothamnus vulgaris Wimm,,

im Vergleiche mit der des Ulex Europceus^ L. Verhandlung.

Nat. Verein. d. Preuss. Rheinlande und Wertfalens. Bd. 37,

1880, p. 157.
4.— Kerner. Pfianzenleben.
5. — Lothelier. An account of the Formation of Spines. From

a paper by Bonnier in Revue Gmerale de Bofaftique, Tom. 2,

1890, p. 276.
6. — Lubbock. A Contributmi to our Kjiowledge of Seedlt?igs,

Vol. I., p. 409.
7. — Henslow. The Origifi of Plant Structures^ 1895, P* 4°-
8. — Warming. Lehrbuch der Oekologischeji Pflanze?igeo graphic^ 1896
9, — Muir. Agriculture^ Practical and Scientific^ iS95-
10. — The article on Agriculture, in The Encyclopcedia Britannica.

46 MORPHOLOGY OF SPECIES OF THE GENUS ULEX.

EXPLANATION OF PLATES IV. and V.

Fig. 1. — Seed of Ulex Europceus ; n, hilum.

,, 2. — Seed beginning to germinate ; shows where the root will emerge.

,, 3 to 6, — Further stages in the germination of the seed of U.
Europccus. ct. , Cotyledons ; s. , Growing point.

,, 7 and 8. — Young seedlings of U. Eiiropceus, showing trifoliate
leaves.

,, 9. — Seedling of U. nanus, var. Gallii, with two trifoliate leaves
and a number of linear leaves, showing how these are
arranged to expose the largest leaf-surface to light.

,, 10. — Copies of nature-printed figures, showing the process of
modification from the trifoliate to the spiny form of the leaf
of U. EuropcEus.

,, 11. — Small portion of a branch of U. Europceus, showing a pri-
mary spiny branch in the axil of a foliage leaf. Between
the foliage leaf and the thorny branch a minute accessory
bud was found. The three upper foliage leaves on the
thorny branch bear flowers in their axils. Slightly magnified.

,, 12. — Transverse section of a spiny branch, diagrammatic, v.b.,
Vascular bundles ; en., endodermis ; s., strengthening tis-
sue ; a., assimilative tissue; e., epidermis; st., stomata ;
c. , large thin- walled cells, just inside the assimilative tissue.

,, 13. — Portion of transverse section of a primary spiny branch,
highly magnified ; lettering same as in Fig. 12, and in addi-
tion, p., phloem ; ch., cambium ; xy., xylem ; h., hairs ; and
pc, pericycle.

,, 14. — Figure showing the arrangement of the leaves on a primary
spiny branch. /., Foliage leaf of the branch on which the
thorn is borne. The distances between the circles indicate
the length of the internodes between the leaves.

Revival of an Old Histological Method for Rapid
Diagnosis. — Dr. A. A. Kanthack and Mr. T. S. Pigg had found,
of all rapid methods of hardening tissue, that of immersing small
blocks in boiling water for three or four minutes, or in the case of
delicate tissue one minute, the most rapid. The tissue could then
be at once cut on the freezing microtome, and the section stained
well with logwood or other dyes ; or it could be preserved in
alcohol or Miiller's fluid, or treated by the paraflin method. For
rapid diagnosis in the case of surgical operations, it was particu-
larly valuable. — British Medical Jour7ml.

Journal of Microscopy, 3^.^ Sen Vol. 7, Plate 4

//aro/d H^ager /: LS, a.a' rfay:<ye/.

F. Ph/7//ps So.

Journal of Microscopy, 3 - Ser.Vol 7, Plate 5.

/faro/c/lfacferfilS, ou£ nal-. c/el.

f: P/yMjos So.

[ 47 ]

IRotea on (Br^ba^a incurva.

By John French.

T'HESE are the commonest fossils of the Essex Boulder Clay.
They are vulgarly known under the name of " DeviFs Toe-
Nails," and are familiar to almost every ploughboy. Like
very many others of their colleagues, they have been subjected to
extensive abrasion and do not often occur as perfect fossils. The
geological range of these fossils is from the Lias to the Chalk
(both inclusive), but so far as I know Liassic examples do not
occur in Essex. Our derivatives, I believe, are principally from
the Oolitic series (Oxford clay, etc.). The abrasion, for the most
part, must have long anteceded the advent of the Boulder Clay,
for most of the examples, broken from their matrix of hard rock,
show considerable wear. It seems to be the fate of this shell
generally to appear under this aspect, even in Liassic specimens.
The amount of wear and tear and tossing about can also be
inferred by another standard, and that is the general absence of
the right or upper valve. Perhaps I should be within the truth if
I said that not one specimen in a hundred bears this appendage.
I could also safely say that not one specimen in a thousand (from
the Essex Drift, at least) is a perfect fossil. It has been my good
fortune to meet with a few such examples, one of which was
obtained from the Boulder Clay at Felstead, and is the one on
which I shall venture some remarks.

In a much-hardened form, every minute ridge and marking of
the original shell is preserved in this specimen. Moreover, the
original had the advantage of belonging to a healthy animal,
which reached maturity without misadventure and without the
disadvantages attending overcrowding, and so was enabled to
produce a shell as regular as the species would allow of, and as
perfect as any healthy mollusk ever did.

To say that the animal " kept the even tenour of his way "
would be stating a case to which probably no mollusk responds.
There is sufficient evidence here of quite another state. There
are main ridges in the shell corresponding to seasonal growths, and
secondary ridges corresponding to minor growths. Like the

48 NOTES ON gryphj5:a incurva.

Roman builder, mollusks appear to do their masonry by small
layers, allowing one to harden before the other is laid on. The
secretions seem to accumulate and then to be used up in shell-
making all at once. Gryphcea, like the oyster of to-day, was
great in this matter of shell accumulation — perhaps too great, as.
it may appear.

A peculiarity is manifest in Gryphcea incurva^ which, so far as
I know, has no match in other members of the oyster family.
This is the circumstance that the adult animal probably could not
be contained in the shell when the valves were closed. This
would appear, however, only to apply to the adult form, in which
the lower valve, being much thickened on the inside, becomes
very shallow, for in immature form the shell is much deeper in
proportion and allows plenty of room. In my specimen, which
is perfectly adult, the lower valve is slightly recurved at the lip,
which I think clearly proves that the animal at that stage some-
what overhung its shell. This, however, does not entitle us to say
that the upper valve had become rudimentary, although the ten-
dency was certainly in that direction, for, as we have seen, the
upper valve formed a real protection during a great part of the
animal's life. Moreover, the adductor muscle, being well deve-
loped, shews that it w^as in frequent use.

In considering to what part of the line of ostreal development
this organism should be referred, the two valves of the shell
would seem to furnish an answer. The elaboration and tremen-
dous development of the lower valve shows that the shell-bearing
functions were at or about at the maximum, and were nowise in a
nascent condition. The smallness of the upper valve is probably
to be explained by the same circumstance that gave such an
unequal impetus to the growth of part of the lower valve, to be
presently noted, and at the same time gave such an undue pre-
ponderance of shelly matter to that section.

These considerations, coupled with the tendency to abort an
important organ (see above paragraph), seem to stamp the form as
specialized and therefore later, and not ancestral or earlier. This
view will receive further support in considering the development
of the lower valve.

There is no clue given by the study of the immature shell of

NOTES ON GRYPH^A INCURVA. 49

G. incurva, as to how and when the departure from a primitive
form took place, or any hint as to the nature of that form. The
smallest shells procurable, which are probably those of the first
year, show all the characteristics equally of the adult form. We
can, therefore, only say that, although its first appearance is in the
Lias formation, its development took place probably long anterior
to the laying down of that deposit.

The peculiarity in the development of the lower valve is very
interesting. The adductor muscle was always attached to one
side of the shell, technically known as the dorsal side. This leads
us to suppose that side to have been the primitive one, and the
other side, or lobe, which is marked off by a furrow on the exte-
rior, to have been a subsequent development. This subsequent
development is that which gives to the shell its generic character-
istics. It forms the bulk of the lower valve or umbone, and in
the course of its development pushes the apex towards the dorsal
side. Meanwhile, the growth of that side proceeds much more
slowly, and always holds a small relative proportion. It is, per-
haps, due to this great demand that the upper valve appears to be
so much impoverished. This valve is of very variable proportions
as regards thickness. Assuming that it receives its increments in
due course, the quantity of shell deposit must be variable in dif-
ferent individuals, if not at different times in the same individual.
This variability, if it occurs in the lower valve, is not so easily
detected in the sum of its results.

The lateral position of the adductor gives rise to a conjecture
as to whether that position may not have something to do with
checking the growth of that particular side. Being large in pro-
portion to the surface of that lobe, and in its course traversing
about three-fourths of the length of the shell, it must apparently
always be detrimental to its growth. In this case the unsymmetri-
cal development of the shell may be due to the same cause that
shifted the adductor from its central position. This, however, has no
connection with the otherwise excessive development of the lower
valve. This seems to be bound up with the cause which has
given us other large developments in the oyster family in geologi-
cal time, and which at the present time produces in the same

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. e

50 NOTES ON GRYPHiEA INCURVA.

species large-shelled varieties along with those in which the growth
of the shell is much checked.

Gfyphcea, unlike the present oyster, passed its life in an unat-
tached position, stability in that form being procurable in a differ-
ent manner. The tendency of the growth of the great ventral
lobe and umbone was to turn over the shell on to its side. This,
however, was prevented by the growth of the dorsal lobe, so much
so that the shell was kept constantly stable at an angle of about
45"^, and would allow of rather a large angle in which. to rock
should it be required. The advantages of this position, in which
the animal was well removed from the mud or sand, is very
obvious.

Unlike the present oyster, also, in the matter of foreign
growths, Gryphcza incurva was a pattern. Nothing appears to
have been allowed to attach itself to the shell. In upwards of
fifty specimens examined, I could only trace the work of even a
sponge in three cases, and in all of these the marks had been
quickly healed over. This leads us to suppose that the animal
was possessed of an epidermal pellicle, chemically adjusted to
prevent the adhesion of other organisms.

This mollusk, though variable within certain limits, remained
practically unchanged for a very long period of time (Lias to
Chalk at least), and how it became finally extinct we do not know.
Like the oyster of to-day, it probably had many enemies, but
whether it succumbed to any of them we do not know. If, in the
great space of time following the Chalk, which to us is a hiatus in
organic life, the upper valve became really rudimentary, it would
seem by that change to have placed itself to a distinct disadvan-
tage. But when we remember that the close-fitting valves of the
present oyster are but little protection against its most mortal
enemies, we can feel no assurance in pursuing that Hne further.

So far as we are able to judge, the changes which took place
in the evolution of G. incurva are not to be expressed in terms of
usefulness to the animal. The ingenious means by which stability
was attained without resulting to attachment was satisfactory so
long as nothing occurred to violently disturb its equilibrium ; but
in the event of an accident occurring sufficient to throw the shell
upon its other side, the consequences were disastrous. Then the

NOTES ON GRYPH^A INCURVA. 51

weight of the heavy umbone, which before had been its safety,
became its ruin, for it was quite impossible for the animal to right
itself again, and in that prone position sand or mud was a con-
stant occupant and must have caused disease and death. Again,
as we have seen, the protection of the upper valve was removed
in proportion as the specialisation of the shell proceeded. That
course can only be regarded as suicidal, to a degree at any rate.

There is much variation in the comparative breadth of differ-
ent shells of G. incurva, but whether this was correlated to other
shell variations — as that of the thickness of the upper valve — or
whether it was hereditary, we have no means of judging.

The modern oyster has a great faculty for adapting its shell to
surrounding circumstances, but the shell of Gryphcea is rarely, if
ever, deformed. Had the organism been endowed with locomo-
tive powers, this would have been of easy explanation ; but in the
absence of those powers, it seems only open to suppose that it did
not frequent crowded situations, or, in other words, was approxi-
mately or in reality a deep-sea inhabitant. Its duration of life
was probably about the same as the present oyster.

P.S. — It has been objected to the above that I " assume the
atrophy of the upper valve," a position which my critic thinks an
"impossibility . . in bivalves." The objection may, I think, be
allowed to stand without materially affecting the observations
which it was the intention of the paper to put upon record.

I should like, however, to say a few words, based rather upon
observation than upon anatomical knowledge, of this "impossi-
bility."

The operculum of Gasteropods is, I believe, still supposed by
good authorities to be the homologue of the upper valve of
Lamellibranchs, and as many Gasteropods have lost it altogether
it is clear that in the same number of cases it has at some time
commenced to suffer atrophy. If one moUusk can, therefore,
abort a part of its shell, there surely can be nothing impossible in
a similar allied organism performing the same operation. The
like argument may be applied in greater or less degree to very
many species in which the shell has more or less become rudi-
mentary, the naked slugs being the most pronounced examples.

The modern oyster, under a highly cultivated form, seems to

52 THE CUCUMBER AND TOMATO EELWORM.

present an example of incipient atrophy of the upper valve. I
refer to the variety known as " Burnham Natives." An oyster
merchant once told me that the feeding on his "layings " tended
to thin out this appendage at the edge, and in proportion as this
thinning-out or paring-off was apparent the animal was considered
" true."

^be Cucumber anb tomato lEelworm^*

By W. Dyke. Plate VI.

THERE is a division in the animal kingdom known to the
zoologist as vermes (worms). This division comprises a
number of diverse groups, one of which is known by the
name of nematoidea (Gr., nema, thread ; eidos^ form). The nema-
todes are, therefore, threadworms, of which more than a thousand
species are known.

During the last few years many cucumber and tomato growers
in this country have lost a considerable number of their plants
annually owing to the formation of nodular enlargements (root
galls) upon the roots. For some time the cause of these nodular
formations was a mystery to growers, and not until Miss Ormerod
issued a report upon the subject {Report of Observations of Inju-
rious Insects^ etc.y 1892, pp. 127 — 137) did it become generally
known that the formation of galls on the roots of Tomatoes,
Cucumbers, and a few other plants growing under glass was the
work of a nematode worm called by Miiller Heterodera radicicola.

The destructiveness of this pest is so great as to often cause
the grower to lose from 50 to 75 per cent, of the above-named
plants, and, therefore, one cannot wonder that they dread its
introduction into their establishments.

Cucumber plants fall a more easy prey than Tomatoes to an
attack of Root eelworm. This is no doubt owing to the soft
nature of the tissues of the first-named plants, for I have seen in
several instances Tomato plants growing and fruiting fairly well in
houses so infested as to make it impossible to grow Cucumbers.

* From The fournal of Horticulture.

THE CUCUMBER AND TOMATO EELWORM. 53

The roots of plants when infested with Root eelworm present
an irregular, knotty, or warty appearance, and are often from two
to ten times larger in diameter than ordinary roots. These nodu-
lar enlargements or root galls when first formed are smooth and
light in colour, but at a later date the surface roughens and cracks,
and is then dark brown, owing to the root gall having commenced
to decay.

If we take one of these brown decaying galls and pull it care-
fully apart, we may probably see with the naked eye small white
oval bodies lying in the darkened decaying tissues. These more
or less oval bodies are the matured female cysts (PI. VI., Fig. i),
being from one-fiftieth to one-hundredth of an inch in diameter.
They are pointed at the head end, and under the microscope the
cyst or chamber looks like an inflated bladder, or what Professor
x^tkinson calls "a crooked-necked squash.'^

In the head end we find a mouth (Fig. i, «), provided with a
hollow exsertile spear (Fig. 2). This spear is found in both sexes,
and can be extended with considerable force, its use being (i) to
batter in the cell-walls of the plant, either to enter or exit ; and (2)
to form a passage by which the food may be drawn into the
stomach of the worm. The food passage looks, when viewed
under the microscope, like a dark fine running down the centre of
the spear, which terminates in an egg-shaped muscular gizzard or
stomach (Fig. i, ^), the latter being attached to the alimentary
canal.

If we look carefully at one of these female cysts under the
microscope, we may be able to see lying in its interior two long
coiled cylindrical objects having free ends (Fig. i). These are the
genital tubes, and in a fully developed cyst will be found to be
packed with eggs in all stages of development. The eggs are
developed in immense numbers in the ovaries (Fig. 1, c), and as
they increase in size they pass along the oviduct (Fig. i, d), and
are finally expelled from the vulva (Fig. i, e). When the eggs are
expelled they are cylindrical in shape, but they soon change in
form, ultimately becoming bean-shaped (Fig. 3). The eggs are
from three to four-thousandth part of an inch in diameter.

The eggs are filled with protoplasm, in which may be found a
nucleus (Fig. 3, n). The early process of development of the egg

54 THE CUCUMBER AND TOMATO EELWORM.

into an embryonic worm is similar to that of a living cell in the
growing part of a plant — />., the nucleus and protoplasmic con-
tents divide, a cell-wall is formed in the division, so that the
mother cell or egg (Fig. 3, a) now contains two daughter cells
(Fig. 3, d). By similar divisions these daughter cells again divide
(Fig. 3, c, d)^ until a mass of cellular tissue is formed (Fig. 4, a),
from which the young embryonic eelworm is ultimately developed
(Fig. 4, b, r, d). The embryo remains for about two days in the
egg and then comes out (Fig. 5).

The young wormlet is about the twelve-thousandth part of an
inch in diameter, and is thread-like in shape, tapering gradually to
a blunt head-end, and gently into a slender needle-like tail. This
is known as the larval stage. During the larval stage males and
females are both alike in appearance — i.e.., eel-shaped, and are
easily mistaken for Tyle?ichus devastatrix (the stem eelworm).

When the eelworm leaves the egg, it generally finds itself
imprisoned within one of the cells of the plant. As soon as the
supply of food in the cell is exhausted, the worm has either to pass
out of the cell or die of starvation. It can, however, pass from
cell to cell by battering in the cell-wall, which it does by means of
the spear.

Sometimes hundreds of worms are liberated by the decay of
the root gall ; these find a fresh portion of root, and enter it by
piercing through the cell-walls. The plant is not able to expel the
intruder, but it tries to repair the injury by the development of
fresh cells ; hence the formation of the nodules or galls on the
roots. After a time the young worms come to rest, and their
bodies begin to enlarge, the posterior end becoming larger than
the anterior portion (Fig. 6). The male, which up till now has
been similar in appearance to the female, undergoes various
changes and modifications, ultimately assuming the eelshape again
(Fig. 7), while the female undergoes a transformation which differs
in every respect from the male. The female, instead of returning
to the eel shape, continues to enlarge (Fig. 8), its tail is cast off,
and its reproductive organs are developed. The male, after wan-
dering about for a time in the tissues of the plant or in the soil,
finds its mate and pairs, then dies.

The eggfc begin to be develoi>ed while the female cyst is com-

Joupnal of Miepogcojp^, 3p3. Sep,, Vol, 7, P

Heterodbba Radicicola (highly magnified).

Fig. 1, Female cyst -.—(a) mouth, (b) stomach, (c) ovaries, (d) oviducts, (e) vulva. Fig. 2, Exserti
spear. Fig. 3, Eggs in various stages of development ; (n) nucleus. Fig. 4, Development of embry(
Fig. 5, Worm (larval stage) emerging from egg: Fig. 6, Commencement of change from larval to cyst
stage. Fig. 7, More advanced development of male. Fig. 8, Female from larval to cystic stage.

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THE CUCUMBEK AND TOMATO EELWORM. 55

paratively small, but it has not yet been determined when fertilisa-
tion takes place. However, it must occur long before the female
cysts are fully grown. On an average each female cyst produces
something like two hundred eggs. It takes about one month for
the eggs to develop into full-grown males or pregnant females.
The following will, therefore, give us some idea to what extent
this pest can multiply, for let us suppose that one female cyst pro-
duces 200 eggs, allowing one half of these to be males, in one
month there would be 10,000 female worms, in two months
1,000,000, in three months 100,000,000, and so on. These
figures must not be taken as what does occur, but are only for the
purpose of illustration. A great deal more might be written on
the life-history of this pest, but I think the above is sufficient to
give those who are troubled with it some idea of what they have
to deal with.

For remedies I would refer the reader to a discussion now
going on in the Journal of Horticulture, but from the brief des-
cription I have given it is easy to see that we can only hope to
eradicate the pest by taking radical measures as soon as it makes
its appearance. When once established, it is, as far as my expe-
rience goes, impossible to get rid of it. In conclusion, I have to
thank Mr. F. S. Hutchason, Wormley, Herts, for the use of the
diagrams, which, I may say, were taken from living specimens we
examined under the microscope.

[Miss Ormerod has done splendid work in many other ways
than in giving the first account in this country of the life-history
of Heterodcra radicicola, from information largely supplied by Dr.
J. Ritzema Bos, Prof Atkinson, and Dr. J. C. Neal ; but so far as
we know the world is indebted to the late Rev. M. J. Berkeley for
its discovery. Cucumber root galls, also a cyst female with eggs
and young larvae, were figured by him in the Gardeners^ Chronicle
in April, 1855. Mr. W. G. Smith gave an excellent illustration of
eelworms in Cucumber roots in ihc Journal 0/ Horticulture, Jan.
14th, 1875, taken from the most gigantic example of Cucumber
root clubbing we have ever seen. Mr. Smith was well acquainted
with Mr. Berkeley's female Heterodera. which was at first taken
for a large vegetable cell in which the eggs were encysted. Pro-
fessor Percival has closely investigated the subject, and is as

56 ENERGY OF LIVING PROTOPLASM.

familiar with eelworms as gardeners are with slugs, Mr. G. Abbey
has also been a diligent investigator, knows the pest well, and has
meritoriously striven to conquer it. Mr. Hutchason and Mr. W.
Dyke have done good service in making clear to our readers the
life-history of the scourge, by delineations from original specimens
as represented in the accompanying plate, for the loan of which
we thank the publishers of Journal of Horticulture?^

Enerai^ of %\vmOi protoplasm.

In the Bulletin of the Imperial University of Tokyo, Herr O.
Loew gives a detailed synopsis with regard to the present state of
our knowledge of the mode of formation, the structure, and the
functions of the protoplasm of living cells, both in non-chloro-
phyllous and in chlorophyllous plants. He calculates that some
microbes may give birth to a trillion of cells from a single one in
the course of twenty-four hours. A great number of details are
given with regard to the nutritive properties for bacteria of dif-
ferent organic substances. These are classified under four heads,
viz. : those which are good, moderate, and bad sources of carbon.
In chlorophyllus plants neither the nitrogen nor the sulphur is
combined with oxygen in the albumen ; a reduction of the
nitrates and sulphates must, therefore, have taken place, as in the
lower fungi. Asparagin was found to be one of the most widely
distributed of the intermediate substances in the production of
protoplasm. As a rule, its increase in the seedling runs parallel
with the decrease of carbo-hydrates. The access of air is indis-
pensable for the formation of asparagin and of protoplasm, but
not for the action of peptonising ferments. — Pharm. Journ.

Lll?KAK T

Iflatwoime an& flDceosoa. IRcmcrtmce.

S:brea&*'W0im6 ant) Saoitta. IRotifcrs,

Ipol^cbact Moima. Earthworme & OLcccbcs.

(Bepb^rea ant) Ipborome. pol^soa/'

IT is with no small degree of pleasure that we direct the
attention of our readers to Vol. II., according to the classi-
fied arrangement of subjects, of this very important work.
We have on former occasions had the privilege of writing notices
with short extracts from Vol. III. on " Mollusca and Brachio-
PODS, and from Vol. V. on " Peripatus," and the first section of
an exhaustive account of " Insects." In reviewing the volume
before us, we shall, with the publisher's permission, make a few
extracts, descriptive of some of the lowlier forms of Animal Life,
for the twofold purpose of inducing our readers to take a more
than general interest in these little-known forms, and to show how
very thoroughly the various subjects have been treated by their
authors, and how admirably the publishers have undertaken their
share in illustrating the volume.

" The Platyhelminihes, or Flat Worms, form a natural assem-
blage of animals, the members of which, however widely they may
differ in appearance, habits, or life-history, exhibit a fundamental
similarity of organisation which justifies their separation from other
worms, and their union into a distinct philum. Excluding the
leeches {Hirudtnea) and the long sea- worms (Nemertinea) — which,
though formerly included, are now treated independently — the
Flatyhehninthes u\2iy be divided into three branches:—!. — Tur-
bellaria (including the Planarians) ; 2.— Trcmadoda (including the
liver-flukes); and 3. — Cestoda (tape-worms).

The Turbellaria were so called by Ehrenberg (1831) on
account of the cilia or vibratile processes with which these aquatic
animals are covered, causing, by their incessant action, tiny
currents ("turbellae," disturbances) in the surrounding water.

*"The Cambkidcje Natural History." Edited by S. F. Ilarmer,
M.A., Fellow of King's Coll., Cambridge, Superintendent of the University
Museum of Zoology; and A. E. Shipley, M.A., Fellow of Christ's Coll.,
Cambridge, University Lecturer on the Morphology of Invertebrates. Vol. II.,
pp. xii.— 560. (London : Macniillan and Co. 1896.) Price 17/- nett.

58 FLATWORMS AND MESOZOA, ETC.

Turbellaria are carnivorous, overpowering their prey by pecu-
liar cutaneous, offensive weapons, and sucking oul the contents of
their victims by the " pharynx." Land Planarians feed on earth-
worms, molluscs, and woodlice ; fresh-water Planarians on Oligo-
chaet worms, water-snails, and water-beetles ; marine forms devour
Polychaet worms and molluscs,

"An account of the Polyclad Turbellaria may be fitly pre-
faced by a description of a very common representative, Lepto-
plana tremellaris^ so called on account of the thin, flat body which
executes, when disturbed, quivering or tremulous swimming move-
ments. . . . Like all Polyclads, Leptoplana is marine. It is
probably found on all European shores, northwards to Greenland
and southwards to the Red Sea ; while vertically it ranges from

the littoral zone down to fifty fathoms At low water,

Leptoplana may be found buried in mud or on the under surface
of stones, in pools where darkness and dampness may be ensured
till the return of the tide."

The anatomy of this worm is given at great length ; we shall
make only sufficient extracts from the author's voluminous des-
cription to enable Plate VIL, which has been kindly placed at
our disposal by the publishers, to be understood.

Leptoplana may be divided into corresponding halves only by
a median, vertical, longitudinal plane. The body and all the
systems of organs are strictly bilaterally symmetrical. Excepting
the cavities of the organs themselves, the body is solid. .
The epidermis is composed of a single layer of ciliated cells, con-
taining small, highly refractive, pointed rods, or " rhabdites," and
gives rise to deeply-placed mucous cells, which are glandular, and
pour out on the surface of the body a fluid in which the cilia
vibrate.

The general arrangement of the Digestive system may be seen
in Plate VIL, and may be compared, especially when the pharynx
is protruded, with the gastral system of a Medusa. The " mouth "
(there is no anus) is placed almost in the centre of the ventral
surface. It leads into a chamber (the peripharyngeal space),
divided into an upper and lower division by the insertion of a
muscular collar-fold (the pharynx,//^.), which may be protruded,
its free lips advancing through the mouth, and is then capable of

FLATWORMS AND MESOZOA, ETC. 59

enclosing, by its mobile fringed margin, prey as large as Lepto-
plana itself. The upper division of the chamber communicates
by a hole in the roof* (the true mouth, g.m.) with the cavity of
the main-gut or stomach {m.g.), which runs almost the length of
the body in the middle line forwards over the brain {up). Seven
pairs of lateral gut-branches convey the digested food to the
various organs, not directly, however, but only after the food
mixed with sea-water has been repeatedly driven by peristalsis,
first towards the blind end of the gut-branches and then back
towards the stomach. Respiration is largely effected by these
means.

The brain, which is enclosed in a tough capsule {pr.\ is placed
in front of the pharynx, but some distance behind the anterior
margin of the body. It is of an oval shape, subdivided super-
ficially into right and left halves by a shallow depression, and is
provided in front with a pair of granular-looking appendages, com-
posed of ganglion-cells, from which numerous sensory nerves
arise, supplying the eyes and anterior region. Posteriorly, the
brain gives rise to a chiefly motor, nervous sheath {n.n.), which
invests the body just within the musculature. This sheath is
thickened along two ventral lines {In.) and two lateral lines {n.s),
but is very slightly developed on the dorsal surface.

Leptoplana possesses eyes, stiff tactile, marginal cilia, and pos-
sibly a sense organ in the " marginal groove." The eyes, which
are easily seen as collections of black dots lying at the sides of
the brain, may be divided into two paired groups : — i, Cerebral
eyes (^.), and 2, tentacle eyes (e.t.), which indicate the position of
a pair of tentacles in allied forms. Each ocellus consists of a
capsule placed at right angles to the surface of the body in the
parenchyma, below the dorsal muscles, and with its convex face
outwards. It is a single cell, in which pigment granules have
accumulated. The light, however, can only reach the refractive
rods, which lie within it obliquely at their outer ends. These
rods are in connection with the retinal cells, and thus communi-
cate by the optic nerve with the brain. The cerebral eyes are
really paired, and are directed, some upwards, some sideways,
some downwards.
*Thc roof of the peripharyngeal chamber is hence known as the "cliaphragm."

60 FLATWORMS AND MESOZOA, ETC.

Passing now to the Termatoda, we have only space for a very
short extract from the Life-history of the Liver Fluke, Distoi7iuin
hepaticum^ which produces the disastrous disease, liver rot; it has
a distribution as wide as that of a water-snail, LimncBa truficatula^
the connexion between the two being, as Thomas and Leukart
discovered, that this snail is the intermediate host in which the
larval, sporcyst, and redia stages are passed through, and a vast
number of immature flukes (Cercarice) are developed. These
leave the snail and encyst upon grass, where they are eaten by the
sheep. . . . Meadows of a clayey soil, liable to be flooded
(as in certain parts of Oxfordshire), are the places where this
LimncBa occurs most abundantly, and these are, consequently, the
most dangerous feeding-grounds for sheep.

Although we find every page of the book exceedingly inte-
resting, we are compelled to pass on to the last section, Polyzoa, a
section which we are sure will delight every microscopist, as it
deals with animals which are scarcely known except to those who
are professed naturalists.

" There are but few Polyzoa which have earned the dis-
tinction of possessing a popular name, and most of such names as
do exist cannot be found outside of Treatises on Natural History.
It is true that many of the members of this group have been
vaguely called "Zoophytes"; but this term implies no more than

EXPLANATION OF PLATE VII. (see opposite page).

Diagrammatic view of the structure of Leptoplana tremellaris
as a type of the Polycladida. The body is cut across the middle to
show the relative position of the organs in transverse section. In the
posterior half the alimentary canal has been bi-sected and removed
from the left side to exhibit the deeply-placed nervous sheath (n.n.),
and the male reproductive organs.

67-., Brain; dp., Diaphragm; e., cerebral group of eyes; e.t.,
Tentacular eye-group; gr., marinal groove; gm., True mouth; l.g.,
Lateral gut-branch; l.n., Longitudinal nerve stem; m. , External
mouth; m.g., m.g.', Main gut, whole and bi-sected; n., Sensory
nerve supplying the eyes ; n.n., Nervous network lying on the ventral
musculature; ns., Lateral nerve; od. , Oviduct; ov., Ovary; |)e.,
Penis (in section) ; ph., Pharynx ; pr., prostrate, or " granule gland" ;
sc, Sucker; s.g., Shell-gland; te., Testes; up>., Anterior unpaired
gut-branch ; ut., Uterus ; va.. Vagina (in section) ; v.d., Vas
deferens ; v.e., Vasa efferentia ; c? Male genital pore ; $ Female
pore.

<7ir<t

1^*0 d

~-d^

FLATWORMS AND MESOZOA, ETC. 63

that they possess a superficial resemblance to certain plants, and
it must be remembered that this habit of growth is assumed by
many animals that have nothing to do with the Polyzoa. The
term "Coralline" is sometimes applied to those calcareous
Polyzoa which grow into coral-like forms ; and the Tertiary
deposit known as " Coralline Crag " is so called from the large
number of fossil Polyzoa which it contains.

"The Polyzoa are none the less a most attractive group.
Let anyone examine a dry piece of brown, paper-like substance
(Flustra foliacea) which may be found thrown up on the beach
on many parts of our coast. Of this species, the so-called " sea-
mat," an old writer says : " For curiosity and beauty, I have not,
among all the plants and vegetables I have yet observed, seen
any one comparable to this sea-weed."* Viewed with a
microscope the frond is seen to consist of two layers, placed back
to back, of oblong chambers, each of which is the dried body-wall
of a single individual. The whole is obviously a colony, and to
this fact the term Polyzoa refers

There is hardly a more surprising spectacle in the whole
animal kingdom than a living fragment of the genus Bugula.
The colony grows in the shape of a small tree, whose height may
amount to several inches ; and is characterised in many species
by a spiral arrangement of the branches, which makes the genus
easy to recognise at first sight (Fig. i, A). The stem and
branches are composed of a single layer of Zooecia, arranged two
or more abreast. Each zooecium bears on its outer side a most
singular body, termed an avicularium, from its resemblance to a
bird's head. Imagine a minute eagle's head attached by a short
but flexible neck to the zooecium. Suppose, further, that the
structure moves backwards and forwards in a deliberate fashion,
its lower jaw usually open so as to be nearly i8o^ distant
from its position when closed. Suppose that its lower jaw is
moved by powerful muscles, which can be distinctly seen inside
the transparent head of the avicularium, and that every now and
then it closes with a snap, seizing any unfortunate worm which
may happen to be within reach with a grasp of iron. The above
gives a faint idea of the appearance of a living Bugula colony,

*Hooper, quoted by Landsborough, Hist, Brit. Zoophytes, 1852, p. 346.

FLATWORMS AND MESOZOA, ETC.

with its hundreds of swaying avicularia, and with its tentacular
funnels protruding from their zooecia, and withdrawing capriciously
from time to time.

The Polyzoa, with respect to external form, may be roughly
divided into— (i) Encrusting forms, usually calcareous, but some-
times soft ; and (2) erect forms, which are either rigid or flexible.
This flexibility can co-exist with a highly calcified ectocyst, as in

Fig. 1. — Bugula terminata, Alder, Plymouth.

A, A small colony (natural size). B, Portion of a branch (x 50).
a. a'., Avicularia in different positions; ap., "Aperture" ; b, Poly-
pide-bud, attached by its stomach tob b., Brown body ; m., Mouth,
surrounded by the body of tentacles (two individuals to the right show
the tentacles partially expanded); 0., ovicell ; s., marginal spine.
The avicularia of some of the zooecia have been omitted in B.

FLATWORMS AND MESOZOA, ETC.

Crista (Fig. 2), Cellaria, and others,
in which the branches are inter-
rupted at intervals by chitinous
joints. The coral-hke forms may
assume the most exquisite shapes,
pre-eminent among which are the
lovely net-like colonies of Retepora.
Polyzoa of this type are seldom
found between tide-marks, where
their brittle branches would be
liable to be snapped off by the
waves. The erect species, which
occur in such positions, are flexible,
although flexible species are by no
means restricted to the zone between
tide-marks.

So far as we have up to the pre-
sent been able to read this book, it
has afforded us much pleasure, and
we trust that the extracts w^hich,
with the publishers' permission, we
have been enabled to make, will
convey to our readers some idea of
the exceedingly interesting nature of
the work.

Our best thanks are due to Messrs.
Macmillan for the use of the very
beautiful electro blocks so kindly
lent to us.

Fig. 2. — CVism ramosay Harmer, Ply-
mouth. — A, End of branch (nat. size).
B, Another branch, x 20, showing the
chitinous joints, the tubular zooecia
characteristic of Cyclodomata, and the
pear - shaped ovicell with a funnel-
shaped orifice at the upper end.

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII.

[ ^Q ]

H IReeume of tbe Itlae^ of 3formaHn/

By George C. Freeborn, M.D.

THIS reagent is also known in commerce under the names of
formol and formalose. It is a forty per cent, solution of
the gaseous body, formic aldehyde (HCOH), in water. It
is prepared by oxidising methylic alcohol and bringing the result-
ing gas into solution in water. It is non-inflammable. It mixes in
all proportions with alcohol and water. Its power of penetration
is good. Its keeping properties are good. A series of experiments
were instituted to determine this point, with the following results :
A forty per cent, solution was kept in open and closed vessels,
daily tests being made. The results of these experiments showed
that the solutions did not decompose. There was a loss of i*6
per cent, of formalin, and an increase of o"i per cent, of formic
acid. Polymerisation took place with the formation of a butter-
like mass containing sixty per cent, of formic aldehyde ; this dried
up into a hard mass which contained eighty-five per cent, of formic
aldehyde. Fish and others advise that it be kept in darkened
bottles, as the light may decompose it. In an experience of two
years I have not noted any appreciable change in the solutions.

Attention was first called to the antiseptic properties of formalin
by F. Blum, in 1893. In 1894 Pottevin found that, when formalin
was added to cultures of bacteria, their growth was arrested.
Cohn also found that solutions and the vapour of formalin killed
bacteria both in the vegetative and in the spore stage, but that it
had but little action on moulds, unless used in strong solutions.
This want of action on moulds has also been noted by many other
observers. Miquel, in experimenting with gaseous formic aldehyde,
found that it acted as a disinfectant for small and loose objects
confined in small spaces, but was not reliable for disinfecting large
rooms. Cambier and Brochet also experimented with the gaseous
form, with results similar to those of Miquel. Their laboratory

* Read before the New York Pathological Society, March 23, 1896. From
the New York Medical Journal.

A RESUME OF THE USES OF FORMALIN. 67

experiments were satisfactory, but their attempt to disinfect a large
room did not give perfect results. They, however, demonstrated
the fact that layers of dust a centimetre thick were rendered sterile.
They also devised a portable apparatus for producing the gas.

Alleger made quite an extensive series of experiments in order
to determine the germicidal action of formalin on bacteria. He
made use of cultures of the bacillus of diphtheria in Petri dishes.
The surfaces of these dishes were sprayed with solutions of forma-
lin varying in strength from i to 1 0,000 to 1 to 100. He found
that a solution of i to 2,000 prevented the growth of the bacillus,
but not that of moulds. Another series of experiments were made
with stick cultures in test tubes. Five drops of solutions of forma-
lin, varying in strength from i to 20,000 to i to 100, were placed
on the surface of the culture media in each tube. At the end of
forty-eight hours none of the tubes which had been treated with a
I to 100 or stronger solution showed any growth. A third series
of experiments were made with smear cultures, which were allowed
to grow for from twenty-four to forty-eight hours, and then they
were treated with the above-mentioned solutions of formalin for a
few minutes. Cultures were then made from these, with the result
that no growth took place from those treated with the stronger
solutions.

Formalin has also been used in surgery, obstetrics, and gynae-
cology, as an antiseptic, but has had to be abandoned on account
of its irritating properties. As a preserving agent formalin was
first used by the botanists. Cohn experimented with it extensively,
and found that the green and red colours of plants were not ex-
tracted. At the end of five months his specimens still retained
their natural colours, and were not shrivelled. The botanists
Sadebeck and Holfert recommend it highly.

It was first introduced into the zoological technique by F. Blum,
who obtained excellent results with it as a preservative agent, and
it has now come into general use. The excellent results obtained
by the botanists and zoologists with formalin as a preservative soon
resulted in its introduction into the anatomical and histological
technique, and at the present time it is quite generally used. As
a preservative agent for gross specimens, it is used in the strength

68 A RESUME OF THE USES OF FORMALIN.

of two per cent.,* though weaker solutions, from three-quarters
to one per cent., have been used. These weaker solutions are
objectionable on account of the likelihood of the growth of moulds,
and because they cause more or less swelling of the tissues. As
the result of the experience of numerous observers, it appears that
five per cent, solutions give better results.

The quantity of the solution should be large — a hundred times
the volume of the specimen — and the fluid should be renewed at
the end of twenty-four hours. In some cases it is well to renew
the fluid a second or even a third time. Formalin used in this
manner preserves the natural form, the transparency, and, to a
certain extent, the natural colour of the specimens. In some
specimens the blood-colour appears to be bleached out, but if the
preparation is placed in strong alcohol this is nearly, if not entirely,
restored. For preserving the blood-colour of specimens, Johres
makes use of the following procedure and fluid :

Sodium chloride ... ... ... i part.

Magnesium sulphate ... ... 2 parts.

Sodium sulphate ... ... ... 2 „

Water ... ... ... ... 100 „

To this mixture are added from five to ten parts of a forty per
cent, solution of formalin. After the specimen has become suffi-
ciently hardened, pour off the formalin solution, wash the specimen
in ninety-five per cent, alcohol, then keep it in ninety-five per cent,
alcohol until the blood-colour becomes restored, and finally pre-
serve it in a mixture of equal parts of glycerine and water.

* Bolles Lee {Anat. Arn., xi.,. 1895, P- 253) calls attention to what he
considers an inaccurate use of the terms formol, formalin, and formaldehyde ;
also to the manner of stating the percentages used. He maintains that the
proper way of stating the strength of the solutions is to say "formol or formalin
diluted with so many volumes of water. "

Parker and Floyd {Aiiat. Am., xi., 1896, p. 567) reply to the criticism
made by Bolles Lee in the above-cited article. They contend " that for the
s ake of consistency the same method of expression ought to be used for alcohol
— i.e., ninety-five volumes of alcohol and five volumes of water. These ex-
pressions seem to us unnecessarily cumbersome, and as they are in no way more
precise or less ambiguous to one familiar with the meaning of per cent, than
the expressions we used, we prefer them."

A RESUME OF THE USES OF FORMALIN. 69

Fish makes objection to the use of formahn as a permanent
preservative on account of the large amount of water present,
which might cause freezing, and advises the addition of an equal
volume of alcohol. Hodenpyl,"*' in using formalin for making
sections on the freezing microtome (see below), found that the
least trace of formalin left in the specimen prevents it freezing. It
would therefore seem that Fish's objection is not valid.

Koehler and Lumi^re found that if from fifty to a hundred and
fifty cubic centimetres of a solution of one volume of formalin,
diluted with four volumes of water, were injected into the gastro-
intestinal canal of small animals by the mouth and anus, also into
the carotid artery, and the animal was kept hung up in the air, in
a dry place, for some weeks, it was perfectly preserved without
distortion. They performed an autopsy on an animal — a guinea
pig — treated in this manner four months after, and found the
tissues and organs perfectly preserved. Dr. Henry Power* has
treated the bodies of children in a manner similar to this with
good results. Professor George S. Huntington informs me that
he has used formalin for the preservation of organs. He injects
a solution of from two to twenty-five per cent, into the blood-
vessels, and the result is a perfect preservation of the form and
colour of the organ. He has found that it is of no use for
preserving dissecting material.

For the preservation of brains, formalin has given excellent
results. The fresh brain is placed in a ten per cent, solution, and
at the end of ten days it will have sufficiently hardened to permit
of the making of thick sections for demonstration of the gross
anatomy, the distinction between the white and grey matter being
more sharply defined than when alcohol is used.

Parker and Floyd confirm the observations of Lanzilotti-Buon-
santi, Hoyer, Hoffer, and others, in regard to the swelling of the
brain when formalin alone is used. In a sheep's brain they found
this swelling to be forty per cent, of its original volume. In order
to correct this defect they experimented with various reagents in
combination with formalin. They finally found that a mixture of
six volumes of ninety-five per cent, alcohol and four volumes of a

* Personal communication.

70 A RESUME OF THE USES OF FORMALIN.

two per cent, solution of formalin gave nearly perfect results.
Sheep's brains hardened in this mixture retained their original
colour and form, and were very little increased in volume. " A
brain that before treatment (June 20th) measured one hundred
and one cubic centimetres, when finally prepared (July 15th)
measured one hundred and three cubic centimetres."

Fish states that an excellent hardening of the brain may be
obtained with the following mixture :

Water ... ... ... ... 2,000 c.c.

Formalin ... ... ... 50 „

Sodium chloride ... ... ... 100 grms.

Zinc chloride ... ... ... 15 n

The specific gravity should be about i"05. The brain is left
in this mixture for a week or ten days. The blood-vessels and
cavities should be injected with the fluid if possible. After the
end of the ten days the brain is transferred to formalin, fifty cubic
centimetres, and water, two thousand cubic centimetres, where it
may be kept indefinitely ; or, after being a week in this fluid, it may
first be transferred to fifty per cent., then to ninety per cent., and
finally to ninety-five per cent, alcohol. He has also treated por-
tions of the adult central nervous system by this method, and
afterwards with mercuric chloride, picro-aceto-sublimate, and
chromacetic-acid mixtures, with good results.

For hardening eyes Leber used formalin mixed with water in
the proportion of one to ten. The natural colour and transparency
of the organ were retained. The cornea and lens became but
slightly cloudy. In his opinion, the fine structure was as well
preserved as with Miiller's fluid. If the eyes were placed in alcohol
the cornea and lens became opaque. I have employed formalin
in a five per cent, solution for this purpose with the same results.
As a hardening agent for microscopic work, formalin has been
used very extensively, the strength of the solutions employed
varying from one per cent, to the full strength — forty per cent.
As the results of many observations, it may now be said, with
possibly one or two exceptions, that formalin alone is an unfit
reagent for hardening tissues for microscopic work. It was con-
demned by Hermann in 1893 ; Lachi states that it has an injurious

A RESUME OF THE USES OF FORMALIN. Tl

effect on connective tissues, smooth and striated muscle, and
embryos. Many other observers condemn its use without being
so specific as Lachi.

The exceptions, where it gives satisfactory results, are mucous
membranes and the central nervous system. I have used it in
five per cent, solution for hardening cystic adenoma of the ovary
with good results ; also for the mucous membrane of the uterus.
Lachi, who has condemned its use for all other tissues, speaks
well of its action on the central nervous system. Van Gieson has
employed it in four, six, and ten per cent, solutions for hardening
the central nervous system. The ganglion and nerve fibres were
well fixed. Sections stain well wuth Weigert's haematoxylin method.
He has also used it for hardening the central nervous system for after-
staining with Rehm's modification of Nissl's method. The results
were good, but not quite so sharp as with alcoholic hardening.

The best results for microscopic work are obtained when for-
malin is combined with other fixing reagents. When it is used
in .combination with the chrome salts, more rapid penetration is
obtained, whereby the time required for hardening is shortened.
I have used a solution of formaUn in Miiller's fluid made as
follows :

Potassium dichromate ... ••• 2 grms.

Sodium sulphate ... ... ••• 2*5 „

Two per cent, solution of formalin ... 100 c.c.

With this'fluid I have obtained excellent preservation of the ovary,
the uterus, etc. At the end of forty-eight hours the specimen is
cut into slices an eighth of an inch thick ; these are washed in
water for two hours ; they are then placed in alcohol for twelve
hours, and then carried through the usual processes of embedding
in celloidin. Specimens hardened in this manner show no shrink-
age, and the tissue elements are well preserved.

Landowsky recommends the following fixing fluids for mitotic
figures in cells :

I. Water ... ... •.• 20 c.c.

Alcohol (ninety-five percent.) ... 10 „
Formalin ... ••• ••• 3 »'

Hydric acetate ... ... ••• o"5 »

72 A RESUME OF THE USES OF FORMALIN.

2. Water .. ... ... 30 c.c.

Alcohol (ninety-five per cent.) ... 15 „

Formalin ... ... ... 5 „

Hydric acetate ... ... ... i „

Probably the most successful use of formalin in histological
technique is its substitution for osmic acid in the osmium-dichro-
mate fluid used in Golgi's silver method for the central nervous
system. This substitution was probably first made by Dr. O. S.
Strong, though it has been recommended by Lachi and others.
Strong employs the following mixture :

Potassium dichromate (3 "5 to five

per cent, solution) ... ... 100 vols.

Formahn ... ... ... 2-5 to 5 vols.

After the specimen has been in the solution for several days it is
transferred to a one per cent, silver nitrate solution ; or, at the
end of two days, it is transferred from the formaUn dichromate
mixture to the following :

Potassium dichromate (five per cent, sol.) 2 vols.

Formahn ... ... ... i »

After remaining in this fluid for from twelve to twenty-four hours,
it is placed in the silver solution. The advantages of this method
are, that the stage of hardening is prolonged, the stage favourable
to impregnation lasts longer, and the results are more certain.
For embryonic tissue he does not consider it as good as the osmic
dichromate mixture. Fish has used the above-described method,
but thinks he has obtained better results with the following :

Miiller's fluid ... ... ... 100 c.c.

Formalin (ten per cent.) ... ... 2 „

Osmic acid (one per cent.) ... ... 2 „

Strong has also used formalin as an injection medium for
hardening brains in situ. He uses formalin diluted with an equal
volume of water. This he injects into the cerebral vessels until
it runs out of the cut jugulars. After a few minutes he makes a
second injection, then a third, and even a fourth, at intervals of
fifteen minutes. The brain is then removed from the cavity of the
skull. The swelling which usually occurs when formalin is used
does not take place. Sections from brains hardened in this man

A RESUME OF THE USES OF FORMALIN. 73

ner may be stained by either the Weigert or the Golgi method.
When the Golgi method of staining only is to be used, an equal
volume of a ten per cent, solution of potassium dichromate is
added to the formalin in place of the water.

Dr. T. S. Cullen has devised two methods for using formalin
in connection with frozen sections. They are as follows :

Method I.

1. Keep sections made with the freezing microtome in a five
per cent, aqueous solution of formalin for three to five minutes.

2. Keep them in fifty per cent, alcohol for one minute.

3. Keep them in absolute alcohol for one minute.

4. Wash them in water.

5. Stain them in haematoxylin for two minutes.

6. Decolourise them in acid alcohol (i'5 per cent. HCl).

7. Wash them in water.

8. Stain them with eosin for twenty seconds.

9. Place them in ninety-five per cent, alcohol.

10. Pass them through absolute alcohol, clear them in creosote,
or oil of cloves, and mount them in Canada balsam.

The blood being lost in the frozen sections, the defect was

overcome by fixing the tissue in formalin, and then making frozen

sections as in

Method II.

1. A piece of tissue 1x2x5 centimetres is kept in a twenty
per cent, aqueous solution of formalin for two hours.

2. Frozen sections are made.

3. Keep them in fifty per cent, alcohol for three minutes.

4. Keep them in absolute alcohol one minute.

5 Wash them in water and stain them in haematoxylin for
two minutes.

6. Decolourise them in acid alcohol (i'5 per cent. HCl).

7. Wash them in water.

8. Stain them in eosin for twenty seconds.

9. Place them in ninety-five per cent, alcohol.

10. Pass them through absolute alcohol, clear them in creosote

or oil of cloves, and mount them in Canada balsam.

Method I. is used for diagnosticating bits from tumours, and

F insel

74 A RESUME OF THE USES OF FORMALIN.

it is possible to make a report in fifteen minutes. Method II.
is used mostly for the examination of uterine curettings. The
author's practice is to have bottles containing a ten per cent,
solution of formalin in the operating room. The curettings are
immediately placed in one of these, and by the time they reach
the pathologist they are hard enough to make frozen sections of.

Bender has also used formalin for making frozen sections, not
for preliminary hardening, as in Cullen's method, but for complet-
ing the hardening of specimens that have already been in alcohol.
He places pieces of tissues, two millimetres thick, that have been
in alcohol, in a one per cent, solution of formalin, and keeps them
there until the alcohol is completely removed. This requires from
half an hour to an hour. He then washes them well in water and
makes frozen sections. The tissue, he states, is rendered soap-like
in consistence by the action of the formalin.

Ohlmacher states that formalin, when used in from two to four
per cent, solutions, acts as a powerful mordant for aniline dyes.
Cover-glass preparations are treated for one minute with the solu-
tion, washed well in water, and then stained in the cold. Or it
may be used instead of aniline oil or carbolic acid as a menstruum
for dissolving the dyes. One gramme of fuchsine or other aniline
dye is dissolved in ten cubic centimetres of alcohol, and this is
added to one hundred cubic centimetres of a four per cent, solu-
tion of formalin. Formalin methylene blue, made by dissolving
one gramme of methylene blue in one hundred cubic centimetres
of a four per cent, solution of formalin, makes an effective stain.
A saturated solution of safranin in a four per cent, solution of
formaUn gives a beautiful double stain when used after the formalin
methylene blue. Nuclei stain blue, plasma stains reddish.

S. H. Gage has used the following solution as a dissociating
agent with good results :

Normal salt solution ... ... i,ooo c.c.

Formalin (forty per cent.) ... ... 2 ,,

Formalin has been used by Hauser for preserving plate and
tube cultures of bacteria. His method is as follows: Plate cultures
in Peri's dishes have a piece of filter paper placed under the cover,
which has been moistened with ten to fifteen drops of formalin.

A RESUME OF THE USES OF FORMALIN. 75

The plates are then placed in a closed vessel, in the bottom of
which is laid paper or cotton saturated with formalin. After
twenty-four hours the cultures are fixed. Test-tube cultures are
closed with a plug of cotton that has been wet with formalin, and
then placed in a closed chamber as above. After twenty-four hours
they are removed and sealed with sealing wax, when a permanent
preparation is obtained. Colonies from plate cultures may be
permanently mounted by the following procedure : The selected
colony is cut out of the plate and placed on a slide and covered,
and then a little of the melted medium is run under the cover.
The slide is then exposed to the action of the vapour of formalin
for twelve hours. Formalin renders ordinary culture media, gela-
tin, and that fluidified by bacteria, non-liquefiable by heat. The
above-mentioned method of preserving bacteria has been employed
successfully by Alleger, Cheesman, and many others. I am
informed by Dr. Cheesman that cultures treated in this manner by
him a year ago are still well preserved, but some of the chromo-
genic forms have lost their colour to some extent.

Displacement of Spines. — T, Kirk shows that the effects of
introduced animals and plants upon the old fauna and flora of
New Zealand go to prove the truth of Darwin's theory of the
" survival of the fittest." Native plants have been unable to sur-
vive the changed conditions accompanying the advent of civilisa-
tion, and their places have been occupied by an army of encroach-
ing weeds. Further, the invading army of plants has brought in
its train a still more dangerous host of animals, those whose
agency is most dreaded being members of the Invertebrata : the
mussel scale, the black scale, and many others, together with
numerous species of plant-lice belonging to lowly-developed forms
of Insects. Higher in the scale are the Hessian fly, wire-worm,
turnip fly, and others, while numerous species of earthworms,
mollusca, birds, and even mammals, affect alike both fauna and
flora. More than five hundred plants have become naturalised in
the colony, but it seems probable that the limit of encroachment
is nearly reached, so far as introductions from Europe are con-
cerned. There are numbers of " repeats " also, for out of one
hundred and three species of plants recently introduced with bal-
last from Buenos Ayres, eighty-six were already naturalised in the
colony. — -Journal of Botany.

[ 76 ]

a IRevlcw of tbe 6olQi flDetbob.*

By Oliver S. Strong.

THE advent of the Golgi method in nerve histology has so
greatly enlarged our knowledge and altered our conceptions
of the structure of the nervous system in many respects,
and the method, or methods, itself has such well defined peculiar-
ities, that it has been thought that a general review of it from the
technical side would be of interest and perhaps of use, especially
in view of the very considerable number of investigators now
employing it.

The review does not aim at any originality of treatment, but is
simply a compilation from available literature of its various modi-
fications and applications. It may be stated that it does not
include Golgi's arsenic-gold chloride method, nor even the applica-
tion of the bichromate-silver methods to the structure of medul-
lated nerve-fibres.

It has seemed most appropriate to begin the review with a
translation of the technique of Golgi's methods as given by Golgi
himself, principally in his work, Studi sulla Jina aiiatoinia degli
organi centrali del sistetna nervoso^ pp. 181-208. The translation
is made, however, from the German edition of Golgi's works
(^" Untersuchu?tgen ilber dein feineren Bau des centrale7i und peri-
pherischeii Nervensy stents,^'' pp. 169 — 182, translated by R. Teus-
cher). Golgi's own account of the technique is still the most
complete, nor does it seem to be by any means universally under-
stood how completely Golgi worked it out, and how largely we owe
not only the discovery, but also the development of the method to
him. It is for these reasons as well as for the many valuable hints
contained therein that the translation of this rather extensive
account of Golgi's is here given.

" The particular methods to which I owe my most noteworthy
success are the following : — (i) The method of black staining by
successively treating the pieces (of brain tissue) with bichromate
of potassium or ammonium and silver nitrate. (2) The method
of the successive action of a mixture of osmic acid and bichro-

* From the Journal of Cojuparative Neurology.

REVIEW OF THE GOLGI METHOD. 77

mate and of silver nitrate. (3) The method of the combined
action of bichromate of potassium or ammonium and bichloride
of mercury. (The stain appears black by transmitted, metallic
white by reflected light.)

"(i) The 77iethod of the combined action of bichromate of pot as -
siu?n atid of silver nitrate. In the series of methods which I have
specially employed this is, in a manner, the fundamental one
The others are only variations of this, devised to shorten the time
of the preliminary treatment, to make the preparations more
stable, to vary the results in various ways, especially to obtain a
greater extension of the reaction and to cause the reaction to
affect one or another species of the elements or a part of them.

" I consider it to the point to call attention to the fact that the
procedure of the microscopical technique which I will describe,
although it rests essentially upon the action of silver nitrate, has
nothing in common with the usual method of staining the inter-
cellular substance of endothelium, epithelium, and connective
tissue, brown or black. In the latter method dilute solutions of
silver nitrate are applied immediately to the fresh tissue, exclu-
sively to the surface of membranes or membranous tissues of
slight thickness (aponeurotic plates, substance of the cornea, intima
of vessels), and light exerts an important influence upon the reac-
tion whereby the blackening of the combination which the silver
salt forms with the ground substance is brought about. With my
method the light has nothing to do, and the reaction takes place
through the gradual penetration of the silver salt into more or less
voluminous pieces which have been previously treated with
bichromate. The black-staining of the various elements compos-
ing the nervous tissue results from a reducing action which the
elements themselves exert, under the influence of the bichromate,
upon the silver salt.

" The procedure necessary to bring about the black-staining of
the elements of the central nervous system consists essentially of
two parts : —

" (a) Hardening of pieces in a solution of potassium bichromate.

" (b) Immersion of the hardened pieces in a solution oj silver
nitrate.

" (a) Hardening in bichromate. Although there are no e-spccial

78 REVIEW OF THE GOLGI METHOD.

rules for the hardening other than those which must usually be
followed to obtain a good uniform hardening, yet it is this part of
the process which requires the most care. This is the more so
because the time necessary to harden the pieces to the degree
required for the action of the second reagent varies very consider-
ably according to different circumstances and especially according
to the temperature.

" For the first immersion of the pieces, I use either a simple
two per cent, solution of potassium bichromate or the usual for-
mula of Miiller. (The reagents should be pure.) There must be
an abundant quantity of fluid in proportion to the quantity of
pieces to be hardened.

" The part of the brain or spinal cord to be treated is cut into
tolerably small pieces (about i to i|- ccm.). It is important that
the pieces be fresh ; the fresher the pieces, the better the results.
It is well to use, preferably, the brains of animals just killed, yet
satisfactory results can also be obtained twenty-four to forty-eight
hours after death. It is hardly necessary to say that the pieces
must be cut regularly and in definite directions (according to the
part to be studied) so as to permit orientation as to the part and
the location of the elements in the future study.

" T'hat the hardening may proceed with some rapidity and be
uniform, it is well to successively increase the concentration of the
fluid, raising the quantity of bichromate from 2 per cent, to 2^, 3,
4, and 5 per cent.

" Whether the fluid is increased in strength in hardening the
pieces, or remains the same strength, it is always necessary to
change it from time to time to avoid the formation of moulds,
which, as is well known, develop abundantly in bichromate solu-
tion when the pieces are to some extent neglected. For the same
reason it is advantageous to place in the vessels with the pieces a
small quantity of some substance which will prevent the growth of
hyphomycetes, as camphor, salicylic acid, etc. The most import-
ant point, and at the same time the most difiicult to determine in
order to obtain good results with this method, is the length of
time during which the pieces must be kept in the bichromate solu-
tion before one passes on to the second part of the process — the
reaction with the silver nitrate.

REVIEW OF THE GOLGI METHOD. 79

" The proper duration of immersion for the pieces to obtain
that degree or particular kind of hardening which is best fitted to
secure, when they are laid in the silver solution, a fine and dif-
fused action upon the various elements of the nervous system
varies according to various conditions. These are the strength of
the fluid, the condition of the pieces, the quantity of fluid, tem-
perature, and, consequently, the time of the year.

" The difl'erences arising from the strength and quantity of the
fluid may be eliminated by paying strict attention to the strength
of the fluid, by using covered vessels, and preserving the same
ratio between the number of pieces and quantity of fluid.

" The influence of temperature upon the results of the reaction
is more important ; indeed, practically, all the uncertainties of the
method depend upon this. For example, to mention extremes,
good results (which, with the progressive changes, of which I shall
speak later; continue to appear and extend) can be obtained in
the warm season after an immersion of fifteen to twenty days and
seldom after thirty to forty or fifty days ; on the other hand, in
the cold season, good results are scarcely obtainable after an
immersion in bichromate of less than one to one and a-half
months. The reaction (with the progressive accompanying
changes) may then continue to manifest itself for two, three, or
four months, provided, of course, the pieces are preserved accord-
ing to the rules given above. It is almost superfluous to say that
during the gradual change from the warm to the cold season and
vice versa corresponding changes in the appearance of the reaction
take place. It is not easy to remedy these temperature changes,
especially because these changes of environment are united with
the other causes of uncertainty mentioned, and so act that obser-
vations made upon one series of pieces never agree closely with
those made upon another series. A warm chamber, of which I
shall speak later, cannot bring about the accuracy sought for.

" The surest means of remedying these inconveniences is the
persevering repetition of the process — i.e.^ one must have a good
number of pieces available, bring several from time to time into
the silver solution, and then ascertain whether they are in the
desired condition. If a good reaction has taken place, one con-
tinues the trials at regular intervals in order to obtain all the stages

80 REVIEW OF THE GOLGI METHOD.

of the reaction, which constitute an advantage of this method. It
is self-evident that the different trials must follow each other at
intervals differing according to the time of the year. In the warm
season, when the requisite hardening is reached much earlier, the
trials must follow each other more quickly ; in the cold season, on
the other hand, when the desired hardening is first reached after a
month, the trials can be made at intervals of eight to ten days,
beginning with the time when one, according to my direction, has
ground to assume that the tissue has begun to enter the desired
condition.

" (b) Transference of the hardened pieces t?ito the solution of
silver nitrate. Although the various conditions of which I have
spoken make it impossible to state with complete accuracy for how
many weeks or days the pieces must be brought from the bichro-
mate into the solution of silver, this is no ground for concluding
that the method is subject to excessive uncertainty." All diffi-
culties are overcome, and one can be absolutely sure of always
obtaining excellent results by the simple procedure of steadily
extending the trials with every series of pieces. The difficulties
are thus very like those which one encounters in the employment
of all other impregnation and imbibition processes, not excepting
the simple carmine staining, in which, as is well known, one only
reaches quick and certain results after repeated trials when he has
learned to know the nature of the staining fluid and of the pieces
to be stained.

" I usually employ a ^ per cent, silver solution ; yet I will
remark that it is not necessary to adhere closely to this formula to
obtain the reaction. A slightly stronger or weaker solution does
not affect the result. , I will also add that a slightly weaker solu-
tion (J per cent.) appears to be somewhat more suitable (giving
finer results though confined to fewer elements) so long as the
pieces have not yet reached the complete hardening, while a
slightly stronger solution (to i per cent.) appears better adapted
for pieces whose hardening has progressed a little too far.

" The quantity of the silver solution to be used must vary with
the number and size of the pieces to be laid therein, but must be
relatively abundant. For two or three pieces of about i ccm., I
use about half a beaker (bicchiere) of the fluid.

REVIEW OF THE GOLGI METHOD. 81

"The moment the pieces are brought from the bichromate
into the silver solution, a copious yellowish precipitate of silver
chromate results. The formation of this precipitate takes place,
of course, at the expense of the strength of the fluid, inasmuch
as, through the formation in loco of the insoluble precipitate, a
more or less considerable portion of the silver salt is deposited.
This changes, naturally, the relation (osmotic as well) between the
fluid which should penetrate into the piece and the inner portions
of the piece. It might happen that the whole or the greatest part
of the silver would be precipitated from the solution, which would
result in the more or less complete absence of the reaction. To
avoid this mishap, it is expedient to first wash the pieces in which
the reaction is sought in a w^eaker solution of silver. I use for
this purpose, from motives of economy, silver solutions which have
already been used on other pieces without the silver having been
fully neutralised. When this washing has been continued until
the pieces cause no more precipitate when brought into a clear
solution, =*' they are finally placed in the fluid of the proper strength.
From there on, the preparation usually requires no especial atten-
tion, for if the solution is present in copious quantity it is sufficient
to let the fluid penetrate into the interior of the piece. Yet it is
well to consider that it is sometimes expedient, with pieces
thoroughly saturated with bichromate through a long sojourn
therein, to change the solution for a fresh one after the pieces have
been in the first solution six to eight hours. This must be done
whenever the fluid assumes a yellow colour, which shows that the
silver nitrate is neutralised. In this case the reagent can no
longer possess the necessary strength to penetrate to the interior
of the pieces.

" I have already said that this reaction, through which the
black staining of the elements is brought about, has nothing in
common with that which stains the intercellular substance under
the influence of light. I now need to add that it is entirely the
same whether the pieces in our method are kept in the light or in
the dark ; the reaction which is brought about through the gradual

* Several minutes should be elapsed to test this, inasmuch as the discoloura-
tion of the silver solution by the reddish precipitate sometimes takes place
rather slowly, both in this and in the rapid method. — Author.

82 REVIEW OF THE GOLGI METHOD.

penetration of the silver into the interior of the tissue takes place
equally well in both cases. The only rule relating to keeping the
pieces in the silver, which experience has shown to be in some
manner useful, is that they should be kept in water in a well-
heated room. I place the vessel on a table which is not far from
the stove of the laboratory.

" The pieces must remain, as a rule, in the silver solution for
twenty-four to thirty hours ; in exceptional cases forty-eight hours.
The period of twenty-four to thirty hours must form the rule,
although, when the time of hardening has been correcdy hit upon,
the reaction may be well advanced in two to three hours. In
such cases one may say that the reaction begins immediately, at
least in the superficial layers, to extend gradually deeper with the
deeper penetration of the fluid. In the exceptional cases, when it
is best to leave the pieces forty-eight hours and longer in the
nitrate solution, and where it is well to change the solution a
second time, one must regulate his procedure by the results of a
microscopical examination of some superficial sections from which
the condition of the reaction may be inferred. Moreover, one
can perceive, from the yellowing of the fluid, whether the reagent
is nearly neutralised.

" As for the rest, it is to be remarked that an indefinite sojourn
of the pieces in the silver solution lasting days, weeks, or even
months is in no way injurious to them; on the contrary, this is a
suitable means of preservation for pieces destined for a particular
investigation of long duration.

" One of the most interesting peculiarities of the process
which I here describe consists in the fact that, while the brownish
black stain acts quite similarly upon all elements of the nervous
tissue (various kinds of ganglion cells, nerve-fibres, elements of
neuroglia, and walls of vessels), yet in reality the staining of all
these at one time forms an exception — />., when the elements are
in a certain state of hardening which one only happens upon
accidentally in a great number of trials. As a rule, the reaction
appears only partially — i.e.^ it affects only one or another layer
with gradations and combinations which one may term endless.

"This peculiarity does not detract from the method, but is
rather among its advantages, for if the reaction affected all kinds

REVIEW OF THE GOLGI METHOD. 83

of elements at the same time, there would evidently arise such an
inextricable confusion that it would be impossible to orient oneself
in respect to the locations and relations of the individual parts.
When, for example, in one preparation the cells especially are
stained black, in another principally the neuroglia, together with
the vessels and some groups of nerve cells, it is evident that one
can, by the comparison of many preparations, obtain a general
view of the various peculiarities of the arrangement and relations
to each other of the individual species of elements and of the
connection of the structures of various regions,

" This is so much the more the case since these combinations
and gradations also appear in certain layers and different zones,
into which one is accustomed to divide different regions of the
nervous system. In the cortex, for example, the reaction appears,
with the various combinations above mentioned, sometimes in the
superficial or middle, sometimes in the deep layers.

"A law undoubtedly exists governing the manner of develop-
ment of the black stain and the succession of the reaction among
the various kinds of elements, and it would be interesting to learn
to know this so as to be able to bring about one or another result
at will ; but it is extremely difficult, if not impossible, to attain
this. This difficulty will be readily comprehended when one
reflects that the diversity of results is brought about not only by
the conditions given already, but also by the unequal hardening
action of the bichromate, so that the individual layers of the
pieces are in different conditions. In the individual pieces the
degree of hardening may increase from centre to periphery, so
that a number of the above combinations and gradations may
appear in one piece.

"The following approximate rule, however, may be accepted
for the way the reaction enters the various elements of the nervous
tissue when a number of similar pieces are successively subjected
to the action of the silver nitrate. Then stain in the following
order : —

" I. — The bundles of nerve fibres. At the same time with the
staining of these fibres some scattered ganglion cells which lie
dispersed in the gray matter appear.

" The staining of the nerve-fibres at the beginning shows little

84 REVIEW OF THE GOLGI METHOD.

delicacy, the reaction being, so to speak, tumultuous, but gradually
gains in fineness with progressive hardening (always, however,
after a more or less brief period of time). Tlien the individual
fibres (axis cylinders) composing the bundles can be vvell seen,
and also individual fibrillae streaming from the bundles, the finest
details of whose course and branching can be seen at a glance.

" 2. — The ganglion cells. The ganglion cells of the superficial
layers always stain first {e.g.^ in the cortex the small cells of the
peripheral zone), but at the same time with t"hem also some cells
irregularly scattered in the inner layers. As the reaction pro-
gresses, it afiects the cells rather than the fibres, and the tendency
is for the stain of the cells to become more general and to 9xtend
from the periphery inwards. Then, too, while the reaction is
becoming more complete among the cells of the deeper layers, it
becomes always more limited among those of the superficial layers.

" With the cells as with the fibres, the reaction is at first coarse
and little fitted to bring to view certain interesting details. For
example, the nervous process is not stained at first to any great
extent, and usually only a short piece of it is to be seen, so that
neither its course, direction, nor its few or numerous branches can
be perceived. With the gradual progress of the reaction the
nerve-cells are displayed more clearly, and the finest subdivisions
of their protoplasmic as well as their nervous processes appear.

" 3. — Cells of the netcroglia. — An interesting reaction occurs in
the cells of the neuroglia ; it may be said that it takes place in
pieces suitably hardened in bichromate from the beginning of the
phase to the end. In fact, at both the time when the fibres pre-
dominate and when the cells predominate, individual neuroglia
cells or groups of them are to be seen showing the characteristic
reaction of the silver nitrate (coffee-brown or yellowish). Besides,
with this species of element the reaction only becomes fine and
diffused in a somewhat advanced period of hardening, so that
their typical form and relations are plain. The reaction in neu-
roglia cells takes place for a long time beyond the time favourable
for staining nerve-cells.

" The finest reaction for the nerve-cells, especially for the nerv-
ous processes, occurs at a somewhat advanced stage of hardening,
namely, when, with the advance of the reaction among neuroglia

REVIEW OF THE GOLCI METHOD. 85

cells, it is limited among the ganglion cells, it is precisely among
isolated blackened cells that the stain of the individual functional
(axis-cylinder) processes is finest ; one can observe the smallest
details of their course and branching. I must again recall that
the reaction must be produced in a series of pieces which have
consecutively received suitable treatment in order to learn to know
all its phases.

" After we have so circumstantially laid down the fundamental
rules of procedure, it would be superfluous to go into particulars
about the differences obtaining between the different provinces of
the central nervous system (the cortex cerebri^ the so-called ganglia
of the base, the cerebellum, the spinal cord). I only remark here
that, under similar conditions, pieces from the cortex reach in
bichromate the suitable state of hardening somewhat sooner than
those from the cerebellar laminae, that the latter reach it a little
later than pieces of the spinal cord, and that finally the so-called
ganglia of the stem reach the proper hardening still somewhat
later than the parts named.

"A last remark. When the above-described peculiarities of
the process are considered, it is intelligible how it often happens
that the reaction appears only in one part of the piece. For
example, it is absent in the superficial layers, where there is, as a
matter of fact, more often than otherwise only an irregular precipi-
tate, and is at present in the interior or vice versa. One must
remember this, and when, very likely, the first sections made near
the surface show nothing of interest, one must not thereupon con-
clude that the reaction has failed, for it often happens that such
preparations, in which only single, isolated cells are stained, are
among the most instructive for details of the individual elements.

[to be continued.]

We are glad to be able to state that Mr. Vine will continue
his very interesting series of papers on "The Predacious and
Parasitic Enemies of the Aphides " in an early part of the Journal.

International Journal of Microscopy and Natural Science
Third Series. Vol. VII.

[ 86 ]

fIDicro6copical C^ecbnique,

Preservation of Structures by Formalin*— Hauser refers to
his former experiments, in which it was shown that cultures could
be preserved by means of formalin vapour. Gegner proved that
gelatin exposed for a long time to formalin vapour does not
become fluid at the body heat. The author further shows that at
no temperature can it be liquefied. At the same time, the gelatin
is in this way permanently sterilised and remains unchanged.
Thus, formalin is a most useful means of preserving cultures, the
only condition being that they should not be allowed to dry up.
It is also specially adapted for microscopic culture preparations.
After thus fixing the gelatin in not too thick a layer, the part which
it is desired to keep should be detached with a sharp spatula.
This is put on a slide with gelatin of similar composition, and a
cover-glass applied. The preparation is then put into the formalin
vapour chamber for twenty-four hours. Lac is applied round the
cover-glass to prevent drying. Cultures can also be made on
slides in the first instance. The author has tried these methods
with success in the case of many micro-organisms. The culture
can also be stained by a weak, watery fuchsin solution. Another
method is to let the coloured gelatin culture dry upon the slide,
and then mount in Canada balsam. The colony should in all
cases lie in the centre of the gelatin.

Bleaching Vegetable Sections.t— Coles' method of preparing
sections for staining is to bleach by means of a solution of chlorin-
ated soda, the length of time varying according to the condition
and nature of the tissues. Wash several times in fresh water, and
finally with water containing eight or ten drops of nitric acid to
each half-pint. Transfer sections to alcohol for an hour before
staining.

Oil of Cassia as a Medium.— Oil of cassia has a higher refrac-
tive index than cedar oil, and Dr. H. G. Piffard finds it brings

* Munch. Med. Woch.^ Aug. 29, 1893, i^ Brit. Med. Journal, Nov. 4, 1893.
t Methods of Microscopical Research.

MICROSCOPICAL TECHNIQUE. 87

objects examined in it into sliarper contrast. In a paper read
before the New York Academy of Medicine, he stated that he
had worked with a sample having a refractive index of i'593.
Bacilli examined in this oil exhibited an unrivalled brilliance and
sharpness of contour. The minuter details, also — such as spores,
flagella, etc. — are shown with a distinctness impossible in cedar oil.
The oil of cassia, like the oil of cloves, tends to abstract the
colour from the bacilli stained with some of the aniline dyes, a
disadvantage not shared by cedar oil ; but it is stated that this
does not take place with sufficient rapidity to interfere with the
diagnostic examination. — Pharmaceutical Journal.

Structure of Yeast"**"— P. Dangeard claims to have proved that
the Saccharomyces cerevisice possesses a well-characterised nucleus.
His material was fixed with absolute alcohol and stained with
haematoxylin, and the details were rendered evident by the aid of
a Zeiss' apochromatic objective of 2 mm. focus. The yeast cell
under these conditions, is said to show, under the limiting mem-
brane, a thick bed of dense homogeneous protoplasm coloured by
the reagent. This protoplasm encloses a large vacuole, and the
nucleus is found lodged in the thickness of the protoplasmic bed,
being described as spherical, limited by a very clear nucleus mem-
brane, and containing in the centre a large nucleolus strongly
coloured. The mass of hyaloplasm between the nucleolus and the
membrane is said to remain free from colour, and one or more
threads of chromatin may frequently be seen in immediate contact
with the nuclear membrane. When the operation of budding
takes place, the bud about to separate and form a new cell makes
its appearance at a spot diametrically opposite to that where the
nucleus is situated. It is almost spherical, and, like the mother
cell, contains a mass of protoplasm enclosing a vacuole. It is
attached to the mother-cell by a very fine pedicel, which subse-
quently disappears. Up to this stage the nucleus shows no
change, but now it moves towards the point of attachment of the
pedicel and splits into two parts, each of which consists of half
the nucleolus surrounded by a clear hyaloplasmic zone. One of

* Comptes Rend.f cxvii., 68.

88 MICROSCOPICAL TECHNIQUE.

these new nuclei then becomes united to the pedicel as at the
mouth of a funnel, and a slender thread of chromatin presently
extends from the point of union to the daughter cell. There it
becomes swollen, and gradually attracts to itself all the chromatic
granules. During the passage through the pedicel, the nucleus
shows no trace of nuclear membrane, but subsequently this
appears as usual. The nucleus remaining in the mother cell is
carried to another point where a fresh bud has formed. When
growth is rapid, several buds may be observed in a cell at the
same time, but they are of different ages, having been formed
successivel} in the manner described, each new budding corres-
ponding to a fresh division of the nucleus. — Pharm. Journ.

Detection of Cholera Bacillus."^— Koch's former method of
examination, though certain in its results, was somewhat tedious,
and a more speedy method has been tried at the Institute for
Infectious Diseases, Berlin. A little mucus from the liquid part
of the object to be examined is fixed on a cover-glass and stained
with Ziehl's fuchsine solution. Cholera bacteria, in such a prepa-
ration, would either occur alone or mixed with ordinary intestinal
bacteria, especially B. coli. They are said to lie as a rule where
the mucus is drawn into threads, and in the characteristically
formed groups the individual bacilli lie in one direction. But even
when the bacteria are scattered, and perhaps mixed with the B.
coli, it is stated that Asiatic cholera may be diagnosed with cer-
tainty. Only when the specimen is a very mixed one is there any
uncertainty in the matter. As regards the method of culture
adopted, a peptone process is now employed by Koch in which the
lumps of mucus are placed in a one per cent, sterilised peptone
solution in a reagent glass, and kept at a temperature of 37° C.
When the preparation begins to grow turbid, the bacteria may be
discovered on the surface (in about six hours) if they are numer-
ous in the test specimen, but when only few they are discovered
later mixed with other bacteria. These peptone cultivations are
said to have given positive results when gelatin plates failed, but
the most satisfactory procedure is to combine the two processes. —
Pharmaceutical Journal.

* Zeit. f. Hygiene, through Med. Press, Vol. CVI., p. 643.

MICROSCOPICAL TECHNIQUE. 89

Stains for Vegetable Tissues.*— Dr. E. Vinassa has investi-
gated the value of aniHne colours for staining v;egetable tissues,
and divides them into three groups only : safranin, congo-red,
benzopurpurins, etc. ; those affecting lignified tissues, collenchyma
vessels, and nuclear sheaths — vesuvin, Victoria green, chrysoidin,
violet, methyl green, fuchsin, etc. ; and stains that merely differ-
entiate, such as Victoria blues B, RRRR, and BB, which colour
the thickened cells darker than the surrounding tissue, and thus
render them more conspicuous. To ensure sections being well
stained, all protoplasm, etc., must be got rid of. This is effected
with soda lye, washing with much water (acidified with acetic acid
if necessary), and then allowing to drain. Afterw^ards immerse in
a J to I per cent lukewarm stain solution for two or three minutes,
and again wash until the water runs clear.

For double staining, first put sections in the stain affecting the
lignified tissue, thickened cell-walls, etc., wash well and transfer to
stain for parenchyma. This should be heated to loo C , and
rendered slightly alkaline. Colours which are fast on cotton were
found to stain parenchyma, whilst those that dye wool or silk
directly stain the thickened cell-walls, etc. Suitable mordants
(tannin, acetate of lead, etc.) for fixing the colours must be found
by experiment.

Staining Tubercle Bacilli.t— A modification of Frankel's
method consists in dissolving r part of fuchsin in loo parts of a
5 per cent, solution of carbolic acid, adding lo per cent, of abso-
lute alcohol and heating the fluid in a watch-glass to near the
boiling point. Float the cover-glasses in the stain for two minutes,
remove, and vnmediately immerse for one minute in a solution of
one to two parts methylene blue in loo parts of 25 per cent, sul-
phuric acid. Then flood with water, dry, mount in balsam.

Cements for Slides.— The "Gram-Rutzou " composition recom-
mended by Poulsem ( Bota7iical Micro-Che?nisiry) appears to grow
in favour. It consists of Canada balsam 50 gm., shellac 50 gm.,
absolute alcohol 50 gm., and ether 100 gm. When mixed, dis-

* From abstract in Microscopical Bulletin, VIII., 6, p. 41.
"^Merck's Bulletin, Vol. V., 3, p. 168.

90 MICROSCOPICAL TECHNIQUE.

solved, and filtered, evaporate over a water-bath to the consistency
of thick syrup. Dallinger, in his new book, makes the useful sug-
gestion that cement-rings should be so finished that, when the
objects are examined by means of immersion objectives, the rings
will be unaffected by the cedar-oil used as immersion fluid.
Hollis's liquid glue, or a varnish made by dissolving shellac or
good sealing-wax in strong alcohol, will effect the desired purpose
when thinly brushed over the edges of the mounts, however closed
and finished. The Scientific Americayi gives a recipe for a trans-
parent cement composed of dammar 5 drs., mastic 3 drs., hard-
ened Canada balsam 3 drs., chloroform and rectified turpentine
each I fluid oz. Dissolve and filter.

Biological Water Analysis.*— An instructive note by Geo. W
Rafter deals with the microscopical as distinct from the bacterial
analysis of water. The former deals with all forms of life that are
easily studied in all their phases by use of the microscope, includ-
ing algae, larger fungi, sponges, infusoria, rotifers, etc. The
various forms of apparatus used are figured and described and the
technique clearly explained. Special attention is devoted to
refinements in enumeration and measurement, and the work is
placed on a thoroughly scientific basis.

Identification of Pectic Substances.f— The method recom-
mended by L. Mangin for determining the presence of these sub-
stances in plant-tissues is to wash sections with acetic acid (t"5
per cent.) ; then neutralise and treat with a mixture of naphthaline
blue R and acid green. The pectic compounds are stained violet
by the former, whilst lignin and suberin fix the green stain. By
acting on small pieces of tissue with dilute hydrochloric acid, or a
mixture of acid, i part, and alcohol, 3 parts, pectic acid, if present,
will be separated from the base (usually lime, with which it is
combined). It is quite insoluble in water, but may be dissolved
by the action of a weak alkali, and then precipitated in gelatinous
flakes by a weak acid. Pectose is found associated with the
calcium pectate, but is not readily isolated, remaining behind after
the action of the alkali.

* Amer. Mon. Micro. Journ., March, 1892.
i /ourn. de Bot.^ Vol. VI., p. 363, in Phai m. Journ.

MICROSCOPICAL TECHNIQUE

To Stain Wood Black.— A process that is much employed for
the above purpose consists in painting the wood consecutively
with copper sulphate solution (i per cent.) and alcoholic aniline
acetate (equal parts of alcohol and acetate). A very durable
black, and the nearest approach to real ebony, is readily obtained
by moistening the surface of the wood with dilute sulphuric acid
(i : 20), and subsequently applying heat. A temperature of 60°
to 90^ C. suffices in a very few minutes to produce the desired
result. An excellent black was obtained in this way on beech,
bass, and boxwood ; while a second treatment was necessary in
the case of cherry, walnut, and birch. With oak and ash the
results were not so good ; and apple and different varieties of pine
were still less amenable to the process, pine especially being
unevenly stained. In order to afterwards remove the acid from
the wood, it might be well to thoroughly wash the latter with dilute
soda solution, followed by clean water. It is unlikely that this
method can be applied to any but small articles, because of the
risk of possible fractures during the necessary heating of the wood.
— Boston Jour7ial of ChetJiistry.

Preservation of Microscopic Specimens.— Tores (Cent./, allg.
Path u. Path. Atiat) (1896, p. 134) describes a method which he
has tested for a year and a-half, of preserving organs and tissues
so that they retain the colour they had when fresh. He finds
that 5 to 10 parts of a 40 per cent, solution of formalin alone,
causes the organs after a time to assume a tint which differs very
considerably from the natural colour ; but that if instead of water
for diluting the commercial formalin solution, a solution of i part
common salt, 2 parts of magnesium sulphate, 2 parts sodium
sulphate, in 100 parts of water be used, the colour of the blood
is well preserved. Further, material preserved in such a solution
is better adapted for subsequent microscopic examination, since
the protoplasm of the cell is less altered, and the nucleus stains
better and more deeply.

The method he adopted is as follows : The material must not
be too long washed in water, and should be left in the lornialin
solution for a period depending on their size and thickness. A
kidney or spleen requires two days' immersion, and the solution

92 MICROSCOPICAL TECHNIQUE.

should be changed once or twice, or until the formalin solution
no longer gives a dirty, brownish-red colour. Care must be taken
to bring all portions of the object into contact with the solution,
and the object must be given the shape which it is to retain per-
manently, since the formalin solution causes it to assume a
consistency such that its shape cannot afterwards be modified.
In the formalin solution the organs change colour and become of
a dirty, bluish-grey. On now placing them in 95 per cent, alcohol
the normal colour returns. Before permanently placing the organ
in alcohol it must be washed with alcohol until the latter no
longer becomes cloudy. The material must not be washed with
water. The material is left in alcohol for a varying time until
the normal colour has again fully returned ; if left longer the
alcohol removes the colour. For a kidney or spleen twenty-four
hours is sufficient. The permanent preserving fluid is equal
parts of glycerine and water; the material floats at first, but
sinks later ; the colour is now at its best ; after a little time the
fluid becomes yellowish and requires renewal. Tissues so pre-
served have not undergone the slightest alterations in colour
during nine months. The method is not applicable to the
preservation of any other colour than that of blood — thus,
icteric liver is not well shown. — British Medical Journal^ June
20th, 1896 ; Epit., p. 100.

Glycerine Jelly, made by Gage's formula, is said to be clear
and bright : — Let gelatine, 25 gm., stand in enough distilled water
to cover it until softened, then pour off" excess of water, and heat
gelatine till dissolved. {Mem., As the quantity of water taken up
varies with the time, it is usually better to add four times the
weight of the gelatine taken.) Next add white of egg, 5 c.c, to
the melted gelatine, stir thoroughly, and heat till the albumin
coagulates. Filter while hot ; then add chloral hydrate, 5 gm.,
and as much glycerine as the gelatine solution measures. Again
heat gently and filter. The jelly is then ready for use. — Phar-
maceutical Journal.

[ 93]

1RCVICW)6-

A Text-Book of Bacteriology, including the Etiology and
Prevention of Infectious Diseases, and a short account of Yeasts and
Moulds, Hiematozoa, and Psorospernis. By Edgar M. Crookshank, M.B.,etc.
Fourth edition, reconstructed, revised, and greatly enlarged. 8vo, pp. xxx. —
715. (London: H. K. Lewis. 1896.) Price 21/- nett.

This, though nominally a fourth edition, is practically a new work. The
progress of Bacteriology has been very rapid, and many new investigations
having been made in connection with the etiology, prevention, and treatment of
communicable diseases, the author has found it necessary to reconstruct, enlarge,
and thoroughly revise the text and to add twenty-six new chapters.

The book is divided into three parts. Part L is mainly technical, and
includes the most recent methods employed in studying bacteria and in investi-
gating the etiology of disease. Part IL deals with infectious diseases and the
bacteria associated with them ; in this part the most effectual measures for
stamping out these diseases are referred to. Part IIL contains descriptions of
about five hundred bacteria. There are 273 illustrations in the text, many of
which are printed in colours, and 22 beautifully-coloured plates. The student
of bacteriology will find it a most valuable book.

Section Cutting and Staining : A Practical Introduction to
Histological Methods for Students and Practitioners. By W. S. Colman,
M.D., M.R.C.P. Second edition. Cr. 8vo, pp. viii. — 160. (London: W.
K. Lewis. 1896.) Price 3/6.

Histologists and microscopists generally will find a large amount of useful
information here. The nine chapters treat of Apparatus, Hardening Processes,
Section Cutting and Mounting, General and Special Methods of Staining,
Injection of Blood Vessels, and Directions for Preparing Individual Tissues.

An Introduction to Structural Botany. Part II., Flower-
less Plants. By Dukinfield Henry Scott M.A., Ph.D., F.R.S., F.L.S.,
F.G.S., etc. Cr. 8vo, pp. xv.— 312. (London : A. & C. Black. 1896.) 3/6.

Whilst it was possible to give an idea of the main outlines of structure in
Flowering Plants in Vol. I. by a full description of three representatives, it has
been found necessary to select no less than twenty-three types for illustration of
the Cryptogams.

The essential morphological points have been well brought out. There
are 114 illustrations and a good index.

A Vest-Pocket Medical Dictionary, embracing those Terms

and Abbreviations which are commonly found in the Medical Literature of the
day, but excluding the names of Drugs and Anatomical Terms. By Albert H.
Bush, M.D. Size, 2^ by 3^ by ^ in. ; pp. 529. (London : Bailliere, Tindall,
and Cox. 1897.) Price 3/-

Owing to the large number of new words which have been introduced into
medical terminology during the last ten years, and the changes in signification
which have taken place in a few of the older terms, it has been fountl necessary
that such a lx)ok as the one now before us should be published. Although the
paper on which it is printed is exceedingly thin, as will be infcrretl from 530
pages only occupying the space of half an inch, the type is thorDUghly distinct.
The book is nicely bound in morocco, and is sure to prove a most useful
pocket companion.

94 REVIEWS.

Handbook of Physiology. By W. D. Halliburton, M.D.,

F.R.S. 14th edit. 8vo, pp. xviii. — 851. (London : J. Murray. 1896.) 14/-
This (fourteenth) edition is practically a new work, for the subject matter
has been re-arranged and almost entirely re-written. It is a work intended for
the use of medical students, and one of its special features is that it treats of
Histology as well as Physiology proper.

The book contains 57 chapters of closely printed matter, every subject
being handled in a thorough and masterly manner. There are upwards of 660
illustrations in the text, several of them coloured, besides some plain and
coloured plates.

Elements of Psychology. By George Croom Robertson.

Edited from Notes of Lectures delivered at the College 1870 — 1892, by C. A.
Foley Rhys Davids, M.A. Crown 8vo, pp. xvi. — 268. (London : J. Murray,
1896.) Price 3/6.

This work consists of a series of 36 Lectures, most of which were delivered
orally by the late Grote Professor Robertson at University College, London.
The editor says, in her introduction : — -"I have tried to make students of a
succeeding generation acquainted with the methods of a great methodologist,
and with the philosophic standpoints of a teacher who for many years worthily
represented and further developed the best traditions of a great school."

Economic Science and Practice; or, Essays on Various
Aspects of the Relations of Economic Science to Practical Affairs. By L. L.
Price. Cr. 8vo, pp. viii. — 325. (London: Methuen and Co. 1896.) 6/-

This book consists of thirteen papers, which have been written at various
times and for different occasions ; they deal generally with the relations of
economic theory to proposals of practical economic reform. In the first,
entitled " Some Typical Fallacies of Social Reformers," an attempt is made to
set forth the moral, if it may be so called, of the present position. In the six
following essays different aspects of various methods of industrial reform, which
have lately engaged a large measure of popular attention, are brought under
review.

The Tutorial Chemistry. Part L, Non-Metals. By G. H.
Bailey, D.Sc.Lond., Ph. D.Heidelberg. Edited by William Briggs, M.A.,
F.C.S., F.R.A.S. Cr. 8vo, pp. viii. -226. (London: W. B. Clive.) 3/6.

Here we have a systematic outline of Chemistry so far as it relates to the
non-metals. Details of experimental methods are given, which, under the
guidance of the teacher, will be found sufficient to admit of the book being
used as a companion in the laboratory. Each chapter is followed by questions,
the more difficult of which are answered at the end of the book. There are a
number of illustrations.

A New Course of Experimental Chemistry, including the

Principles of Qualitative and Quantitative Analysis, being a Systematic Series
of Experiments and Problems for the Laboratory and Class-room. By John
Castell-Evans, F. I.C. , etc. Cr. 8vo, pp. xii. — 244. (London: Thomas
Murby.) Price 2/6.

In the present revised edition of this work, the author's aim is to help
students to attain a real knowledge of scientific chemistry, and not to prepare
for mere examination, for, as he justly says in his preface, " Examinations are
only accidents of a scientific career, and accidents that are rarely beneficial ;
but knowledge is essential."

We feel that we can confidently recommend the book.

REVIEWS. 95

The Survival of the Unlike : A Collection of Evolution

Essays suggested by ihe Study of Domestic Plants. Hy L. II. Bailey. Cr.
8vo, pp. 515. (London: Macmillan and Co. 1896.) Price 8/6.

The author, a botanist of some considerable repute at the Cornell Univer-
sity (U.S.A.), has in these essays desired to answer many of the common ques-
tions which puzzle horticulturists by appealing to the evidence of evoluti(in.
He desires to spread a knowledge of the evolution speculations, and the
methods of research which they suggest, amongst those who deal with plants
and animals and w^ho lead a rural life.

The book contains 30 essays, divided into three sections : — I., Essays
teaching the General Fact and Philosophy of Evolution ; II., Essays expound-
ing the Fact and Causes of Variation ; and III., Essays tracing the Evolution
of Particular Types of Plants. The essays are very ably written.

Charles Darwin, and the Theory of Natural Selection.
By Edward B. Poulton, M.A., F.R.S., F.G.S., F.L.S., etc. Cr. 8vo, pp.
224. (London : Cassell and Co. 1896.)

In this interesting little volume the author gives us what he believes to be
the most important statements of this great scientist, while he has grouped
them in such a manner as to present a connected account of Darwin's life,
when considered in relation to his marvellous work, and especially to the great
central discovery of Natural Selection, and its exposition in the " Origin of
Species."

Science Progress : A Quarterly Review of Current Scientific
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tion price 10/6 per annum post free. (London : The Scientific Press, Ltd.)

The part before us commences a new series of this thoroughly up-to-date
journal. This part contains papers on the following subjects : — Scientific
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Igneous Rocks, by Alfred Harker, M.A. ; Recent Work upon Visceral and
Allied Nerves, by T. Gregor Brodie, M.D. ; Notes on Parasites, Part I., by
A. E. wShipley, M.A. ; Teratology in Modern Botany, by K. Goebel, Ph.D. ;
The Nervous System of Coelentera, by S. J. Hickson, F. R.S. ; Pala^ontolog}'
and Evolution, by A. C. Seward, M.A. ; and Appendixes, Notices of Books.

A New English Dictionary on Historical Principles. Edited
by Dr. James A. H. ^Murray. Disburdened — Disobservant, Vol. HI. ;
and Fish — Flexuose, Vol. IV. Price 2/6 each part.

We notice that the first of these sections contains 1396 main words, 27
combinations explained under these, and 127 subordinate words, or 1550 in all.
Of these 1450 words are illustrated by 6990 quotations. Perhaps the most interest-
ing word to be found in these pages is Dismal, the full history of which is here
for the first time exhibited. Contemporary evidence shows this to have been ori-
ginally the Anglo-French dis mal ; Latin, dies malt, evil or ill-omened days,
the "Egyptian days" of the mediivval calentlar ; and it was so applied for
more than three centuries. It is only as we come down to 1600 that we find
other things than days characterised as "dismal."

The Vol. IV. section contains 956 main words, 314 combinations explained
under these, and 170 subordinate entries, making 1440 in all. The obvious
combinations, recorded and illustrated by quotations, without individual defini-
tion, number 372 more.

Of the 1812 words contained in this section, not more than 35 existed in
Old English. The most striking characteristic of this portion of the English

96 REVIEWS.

vocabulary is the abundance of words which have been influenced in their
sense-development by their apparently imitative or expressive sound, as Jizz.
fizzle, fiabhergast, flack, etc. etc. The etymological notes on most of these
words will be found to contain facts not given in other English dictionaries.

The editors are to be congratulated on the very efficient manner in which
they are performing their very arduous work.

The Pocket Atlas of the World. By J. G. Bartholomew,
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The tenth edition of this useful little atlas has been greatly amplified and
extended. Without increasing the bulk, 72 new plates have been added, the
text has been re-written, and the maps thoroughly revised to date. The Index
to the maps occupy 72 double-column pages.

Knowledge in a Nutshell. Size, 2\ by 3^ by t| in. Glas-
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Undoubtedly the book before us is all that its name implies. First, we
have Bryce's Pearl English Dictionary, comprising, besides the ordinary
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Bryce's Pearl Atlas of the World, containing 72 maps. Bryce's
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the places named, also the last census, occupying 43S pages ; and lastly. The
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covering 120 pages. This is altogether a very useful book.

Economic Entomology for the Farmer and Fruit-grower and
for use as a Text-book in Agricultural Schools and Colleges. By John B.
Smith, vSc.D. 8vo, pp. 481. (Philadelphia, U.S.A.: J. B. Lippincott Co.
1896.) Price $2.50 (10/6).

Insect injury to agricultural products amounts each year to a very consider-
able sum, and as a whole shows a tendency to increase rather than otherwise.
Progressive farmers have long been aware of this, and the science of economic
entomolog)' has grown up in response to their demands for information con-
cerning insect depredation and for means of protection against it. In this book
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tion upon which further information may be added.

The book — which, we trust, will be the means of saving a large amount of
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but in this country also — is divided into three parts. The first is devoted to the
Structure and Classification of Insects ; the second treats of the Insect World ;
and the third of Insecticides, Preventives, and Machmery. There are 483
very good illustrations.

Ages Ago : The Ancestry of Animals. By Edith Carrington.
Post 8vo, pp. 179. (London : G. Pell and Sons. 1896.) Price i/-

This is one of the very interesting series of Animal Life Readers, its object
being to give to young people a first idea of the great antiquity of animal life
on the earth, and to show the essential part tljctt animals have played in the
history of the world in its various stages of development. It is nicely illus-
trated by Harrison Weir and others.

REVIEWS. 97

Half-Hours in the Tiny World : Wonders of Insect Life.
Cr, 8vo, pp. xii. — 308. (London : Jas. Nisbet and Co. 1896.) Price 2/6.

A very interesting and nicely illustrated little book, containing a series of
chapters describing Insect Life, Caterpillars, The Spider and its Web, Bees and
Beehives, Wasps and Paper-making, Silk and Silkworms, Flies, Ants and Ant-
hills, Life in a drop of Water, Coral and Coral-builders, Nature and her tools,
etc. There are 80 or more good illustrations.

Gleanings from the Natural History of the Ancients.

By Rev. W. G. Watkins, M.A. Cr. 8vo, pp. xv.— 258. (London : Elliot
Stock. 1896.)

In this exceedingly interesting book we have a number of chapterson a few
of the curiosities connected with the natural history of the ancients ; they have
been put together with much trouble and not a little honest, diligent research ;
the object of the author being to collect some of the more interesting facts
bearing upon ten or a dozen different subjects rather than to write a complete
natural history of the ancients. These chapters treat of Greek and Roman
Dogs ; Antiquarian Notes on British Dogs ; the Cat ; Owls ; Pygmies ; Ele-
phants ; the Horse ; Gardens ; Hunting among the Ancients ; the Romans as
Acclimatisers in Britain ; Virgil as an Ornithologist ; Roses ; Wolves ; Ancient
Fish-lore ; Mythical Animals ; and Oysters and Pearls.

Natural History Pictures for Object Lessons. Size of

Plates, 24 by 28 inches. (Edinburgh : W. and A. K. Johnston.) Price, 3/6
each.

A series of beautiful plates printed in colours. Those sent to us illustrate
and thoroughly describe The Flamingo, Anemones, and Corals ; the Tiger,
Serpents, and the Whale — e.g., The Anemones and Corals are thus
described : — Anemones, sub. Kingdom Ccelenterata, Class Actinozoa, Order
Zoantharia, Anemones (French;; Anemones (Spanish); Windroschen
(German), Then follows a full description. Those represented on this sheet are :
I, The Aciinoloba Dianthus ; 2. Bolocera Eques ; 3, Sagartia Veduata ; 4,
Cereus Coriaceus ; 5, Anemonia Cereus Alcyonaria. Corals : Sub-Kingdom,
Ca'lenterata ; Class, Anthozoa ; Order, Alcyornana ; Corails (French)
Corales (Spanish) ; Koralle (German). Those represented being Corallium
Rubrum or Red Coral, and of the Madrepore Dance.

The other sheets are equally well described. These sheets are splendidly
suitable for schoolroom walls.

Wonderland ; or, Curiosities of Nature and Art. By Wood

Smith. Cr. 4to, pp. 288. (London: Thomas Nelson and Son. 1897.) 3/6.
A charming book for young people. Wonderhind consists of two great
regions, one called Nature, the other Art, in each of which there are many
marvellous things, all of which are described in a most interesting manner, and
very beautifully and profusely illustrated, there being no fewer than 170 illus-
trations. Many of them are full-page plates.

Simple Lessons from Nature. By M. Cordelia E. Leigh.

Post 8vo, pp. xii. — 131, (London : J. Nisbet.) Price i/-

We have here a series of very simple lessons drawn from Nature for young
children, the aim of the author having been to make them as simple as possible.
The facts to which they refer when carefully explained can hardly fail to increase
the love and reverence of scholars for their Maker, while the interest excited
may develop their power of observation and research, and afford useful employ-
ment for their time and thought.

98 REVIEWS.

Entomological Notes for the Young Collector. By W. A.

Morley. i2mo, pp. x. — 129. (London: E. Stock. 1896,) Price 2/-

Young collectors will find this just the book they require. Its twelve

chapters tell what butterflies and moths may be caught each month, with hints

as to apparatus, setting, etc. etc.

We are sorry to note that, in common with many other entomologists, the

author apparently ignores generic names, and gives only their initials.

Out-of-the-Way Pets and other Papers. By Rev. Theodore
Wood, F.E.S., etc. Cr. 4to, pp. 263. (London: F. Sherlock.) Price 5/-

This very nice little book consists, first, of a series of twenty-four papers,
originally published in the Church Monthly, describing a variety of animals,
birds, insects, etc., followed by a series of twelve monthly rambles. In most of
these the author has endeavoured to emphasise the great lesson that what men
mostly call Nature is a second Bible. There are upwards of 70 good illustra-
tions.

Across Greenland's Ice-Fields : The Adventures of Nansen
and Peary on the Great Ice-Cap. By M. Douglas. Crown 8vo, pp. 218.
(London: Thos. Nelson and Son. 1897.) Price 2/-

The author of this interesting and nicely illustrated little book has selected
those heart-stirring narratives for her theme which relate to the perils and diffi-
culties attendant on the exploration of the Inland Ice of Greenland. Miss
Douglas conducts her readers over those trackless wastes of snow and ice in
the footsteps of Nordenskiold, of Nansen, and of Peary ; and certainly those
who begin the journey with her will, in continuing it to the end, derive no
small amount of pleasure and instruction. A portrait of Nansen forms the
frontispiece to the book.

On the Broads. By Anna Bowman Dodd. Fscap. 4to, pp.
xii. — 331. (London: Macmillan and Co. 1896.) Price 10/6.

A most interesting and pleasantly written book describing a fortnight's
cruise on the P)roads, the district which lies between the sea-beaches of Yar-
mouth and Lowestoft. " For more than a decade," says the author, "cruising
on the Broads has taken a foremost place in the long list of summer sports and
pastimes yielded by that amazing little island, where, by utilising every rill and
rivulet, every hill and upland, man has doubled the size and tripled the plea-
sure-giving capacity of the stretch of land he calls England." There are 30
fine full-page illustrations.

The Story of Extinct Civilisations of the East. By
Robert E. Anderson, M.A., F.A.S., etc. Fscap. 8vo, pp. 229. (London:
George Newnes, Ltd. 1896.) Price i/- •

This is one of the Interesting Story Series, and tells us in very readable
language of — i, The Origin and Races of Mankind; 2, Chaldea and Baby-
lonia ; 3, Ancient Egypt ; 4, Hittites, Phoenicians, and Hebrews ; 5, The
Arab ; and 6, Iran, or Ancient Persia. There is an illustration of the Moabite
Stone ; Hieroglyph ; Cuneiform Inscription ; and maps of Egypt, Khita, and
Spain.

Bromide Paper : Instructions for Contact Printing and
Enlarging. By Dr. A. E. Just. 4th edition. 8vo, pp. 144. (London and
Bradford: Percy Lund. 1896.) Price 1/6.

Very full instructions are here given for every detail of the work from the
Preservation and Cutting and Handling of the Paper, Exposing, Lighting, to
Enlarging. A number ul !■ crmulae are given.

REVIEWS. 99

Everyone's Guide to Photography, containing Instructions

for making your own Appliances and Simple Practical Directions for every
branch of Photographic Work. By E. J. Wall, F.R.P.S., etc. i6mo, pp.
246. (London: Henry J. Drane.) Price 6d.

A capital and most useful little book, quite answering to its title. Besides
going thoroughly into the subject of Photography generally, it has chapters on
Pinhole and Stereoscopic Photography, Hand and Detective Cameras, Photo-
graphy in Natural Colours, Iron and Uranium Printing, The New Photo-
graphy, Ghosts, Freaks, and other Photographic Effects, etc. etc. The size,
5i by 4 in., makes it convenient for carrying in the pocket.

Everyone's Housekeeping Companion. i6mo, pp. 250.

Everyone His Own Doctor ; or, The Household Medical
Guide. Edited by Alexander Ambrose, B.A., LL.D., M.D., etc., etc.
i6mo, pp. 254.

How TO Speak Well in Public or in Private. By Charles
Hartley; i6mo, pp. 176. (London: Henry J. Drane.) Price, cloth, 6d.
each ; leather, i/-

The Housekeeping Companion contains a large number of hints for all
kinds of Cooking, Preserving, and Pickling. The Making and Keeping of
Home-made Wines and Temperance Drinks. A large number of useful and
valuable Household Recipes, and full directions for Carving, tKe latter being
well illustrated.

The second of these little books presents in a popular form some of the
latest knowledge of those subjects which are of every-day medical interest ; it
is arranged in Dictionary or Cyclopaedic form, so that everything is easily found.

In How to Speak Well some very good hints are given on Elocution and
Oratory; which may be profitably read by many.

The whole form a useful set of little books.

The Dark-Room and its Equipment. By H. J. L. J. Masse.
Lantern Slides : Their Production and Use. By J. Pike.
Developers : Their Use and xA-buse. By Richard Penlake.
The Camera and its Appurtenances. By H. J. L. J. Masse.
The ABC of Re-touching. By Andrew Young.
Photography and Architecture : How each lends interest

to the other. By E. MacDowel Cosgrave.

Indoor Photography and Flash-Light Studies of Child
Subjects. By Bertha M, Lothrop.

The X Rays. By Arthur Thornton, M.A.

(Bradford and London : Percy Lund and Co. 1896.) Price 6d. each.

The above little books— together with the two we noticed in our October
issue (Drop-Shutter Photography and the Elements of Stereoscopic Photogra-
phy) — form, we believe, the entire series, so far as pul)lishe<l, of Mr. Percy
Lund's Popular Photographic Series. They form a valuable and very compact
library of photographic works. The size of the books, lieing 7.^ by 4 in.,
makes them very convenient for carrying in the breast-pocket.

These little books are carefully written, the instructions i^iven being concise
and clear. They are printed on good paper and well illustrated ; indeed, illus-
tration appears to be one of Mr. Lund's strong points.

100 REVIEWS.

Cassell's Dictionary of Cookery. Roy. 8vo, pp. xcvi. —

1178. (London: Cassell and Co. 1896.)

We are told in the Preface that " Life is made all the brighter by
satisfactory fe<ding, and he is a dull philosopher who despises a good dinner.
But [hti strong point of good cookery is not the gratification of the
palate, but its influence on health. . . . Our household would enjoy
better health, and be better able to withstand sickness when it came, if pains
were only taken to have food well chosen and properly made ready. A desire
to aid in the diffusion of knowledge on such an important topic induced the
publishers to project a Work on Cookery, which would be at once the largest
and most complete collection of recipes ever produced in this country."
Arranged in Dictionary form we find here about nine thousand recipes, which
have been put in the simplest form, and the plainest language. The first 90
odd pages treat of the Principles of Cookery and Table Management ; there is
also an appendix dealing with Kitchen Utensils, Seasonable Food, and
Glossary of Terms used in Cookery. We need only add that the book is now in
its one hundred and thirty-fifth thousand to show how well it has been received.

The British and Colonial Druggist's Diary, 1896.

As usual, this diary contains a large amount of information of much use to
the druggist, amongst which we particularly notice "Notes on Food Analysis "
and X Rays for Chemists. The diary, interleaved with blotting paper^ will be
found particularly serviceable.

The Standard Priced Catalogue of the Postage and Tele-
graph Stamps and Postmarks of the United Kingdom, No. 5. Compiled and
published by H. L'Estrange Ewen. Post 8vo, pp. 218. (Norwood : 32 Palace
Square. 1896.) Price 2/6, post free.

Stamp collectors, and particularly those who make a speciality of British
stamps, will do well to secure a copy of this catalogue. Mr. L'Estrange Ewen
is a specialist, and gives such information in this catalogue as is not to be
found, so far as our experience goes (and it is somewhat considerable), in any
other work on the subject.

The scope of the book is so well explained in the title that we think it
unnecessary further to describe the book.

The Lincoln Stamp Album, with Catalogue and Maps.
Eleventh thousand. Crown 4to. (London: W. S. Lincoln, 2 Holies St.,
Oxford St.) Price 5/-

Spaces are provided in this catalogue for 6,500 stamps, special spaces being
provided for stamps of unusual shape and size. The ruled pages are headed
with the names of countries arranged in geographical order, and in the cata-
logue at end many interesting particulars are given ; there are also 16 maps.
The album is very suitable for a beginner.

Moring's Quarterly for October (Thos. Moring, 52 High
Holborn, W.C. ) contains an interesting article on Methods of Reproduction
for Book Illustrations.

[ 101 ]

a Cbaptcr on Xigbt anb Colour;^

By G. H. Bryan, Sc.D.

^^\J*i^^ 1. -Elementary Phenomena of Light.

o3Vfe

IHE agent which affects the sense of sight is spoken
of as Light. It has been conceived of as small
particles emitted from visible bodies and striking
the eye, or as a wave motion propagated through a
medium (called the B^'her) and exciting the nerves
of the retina by this motion. The latter view has
now come to be accepted to the complete exclusion
of the former, though such eminent names as those
of Newton, Laplace, and Biot are connected with
the development of the Corpuscular Theory of Light.

The most striking of simple light phenomena, the production
of shadows, and the sharpness of the shadows when the source of
light is nearly a point, was for a long time a great difficulty in the
way of the acceptance of the Undulatory Theory, but this diffi-
culty has been overcome, and the simplicity of the explanation,
afforded by this theory, of many somewhat complex phenomena,
has placed it in complete command of the field. The vibrations
which produce light are transverse to the direction of propagation.
2. — The explanation of many facts can be obtained by an
application of four simple laws of light propagation,
(i.) Light is transmitted in straight lines,
(ii.) When a ray of light is reflected, the reflected ray makes
with the reflecting surface an angle equal to that made by the
incident ray, and the two rays are in a plane perpendicular to the
surface.

(iii.) When a ray of light is refracted at the surface of two dif-
ferent media, the angles of incidence and refraction have a deter-
minate relation to one another depending on the media, and the
plane of the two rays is perpendicular to the refracting surface.
The relation referred to is that the sines of the angles of incidence
and refraction are in a constant ratio.

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. h

102 A CHAPTER ON LIGHT AND COLOUR.

(iv.) If a ray be reversed at any point of its path, it will return
over exactly the same path as that which it has already traversed.
A Ray is here conceived of as the smallest portion of light which
can be separately transmitted, reflected and refracted. A group
or bundle of rays constitutes a Pencil.

3. — The first of the above laws is sufficiently obvious, but we
shall see that Hght, like sound, can bend round a corner, though
not sufficiently, in general, to produce effects readily recognisable.

The production of Images by Reflection in plane, and even
in curved, mirrors is familiar to us also. The image is as far
behind a plane mirror as the object is in front of it. Curved
mirrors produce images not, in general, equal in size to the object,
and may produce curiously contorted images.

The Refraction or bending of rays of light as they pass from
air to water or glass causes a change in the appearance of an object
seen through such bodies, unless a second bending takes place at
a parallel surface to recompense for the first. The production of
images by lenses is a practical application of this bending of light
by glass, and in telescopes, microscopes, opera-glasses, and spec-
tacles is made of great service to mankind. The position, size,
and degree of distortion (if any) of the image, can be determined
by repeated calculations from the laws given above.

Refraction is closely connected with Total Reflection.
Contrary to what is usually the case, at angles of incidence beyond
a certain limit, light traversing a denser medium and meeting a
surface of separation from a less dense, is no longer divided into
both reflected and refracted waves, but gives only the former,
being, for all angles of incidence exceeding this limit, totally
reflected into the medium which it is traversing.

If light be propagated through a medium which is not homo-
geneous, its path will not be a straight line. The light from the
stars suffers a continuous bending in passing through the earth's
atmosphere. In some tropical regions the sun's heat causes a state
of the atmosphere to be set up in which layers of differently-heated^
and therefore differently-refracting, air are superposed in such a way
as to totally reflect rays of light which were originally travelling at
a small upward inclination. In this way the phenomenon of
Mirage is produced.

A CHAPTER ON LIGHT AND COLOUR. 103

4. — If a source of light, such as a candle flame, be placed
behind a pinhole in a card, an image of the light giving body may
be obtained by interposing a screen in the path of the light which
passes through the hole. The image is found to be inverted, and
if a sensitised plate be substituted for the screen, a fairly well
developed photograph may be obtained of any object placed in
front of the pinhole. Other holes will give other images, and by
the continued multiplication of holes the individuality of the
images may be destroyed and a tolerably uniform illumination of
the screen, within the shadow of what remains of the card, results,
due to the overlapping of eacli image by its immediate neighbours
on all sides. Unless the source of light be quite small, the shadow
of an opaque object or the light transmitted through a hole will
not be terminated by a sharp edge.

The light gradually becomes fainter as we approach those
regions which are so placed as to receive light from a part only of
a luminous body. This partially bright border is called the
Penumbra, and its consideration is of great importance in the
calculation of the circumstances of eclipses.

5. — The fact that light is not instantaneously transmitted from
point to point was proved by Roemer in 1676 from a consideration
of the eclipses of Jupiter's moons, which appear to take place
earlier or later than predicted, according as the earth is at the
part of its orbit nearest to, or furthest from, Jupiter. The range
of eight minutes on either side of the average in the time at which
these eclipses are seen is due to the extra distance, equal to the
diameter of the earth's orbit, which the light has to traverse in the
one case compared with the other.

In 1725 Bradley showed that a small displacement of the appa-
rent positions of stars was due to the fact that the velocity of light
is only about 10,000 times that of the earth in its orbit. The
Aberration is a phenomenon exactly analogous to the apparent
slope of rain drops, really falling vertically, as seen from a swiftly
moving train. From Bradley's observations, and a knowledge of the
sun's distance otherwise gained, the velocity of propagation of
light could be determined.

6. — This determination, however, was made directly by Fizeau
in 1849 t>y the use of a rapidly revolving toothed wheel. It was

104 A CHAPTER ON LIGHT AND COLOUR.

found to be possible to rotate the wheel so fast that light which,
emerging between two of its teeth, passed on to be reflected back
from a mirror five miles distant, returned to the wheel to find its
path blocked by a tooth. A more rapid rotation permitted it to
pass through the next gap. Knowledge of the distance traversed
by the light and the speed of rotation of the wheel enabled the
speed of light to be calculated. Another method^ due to Foucault,
was devised about the same time, which involved the use of a
rapidly revolving mirror. The distances used were in this case
shorter by far than in Fizeau's method.

By the application and perfection of these methods, the Velo-
city OF Light has been found to be about 186,400 miles per sec.
The length of an undulation is extremely small, however, being only
about i/4o,oooth of an inch, so that about 500,000,000^000,000
of waves are received into the eye in each second.

7. — Colours. — When light is refracted through a wedge-shaped
piece of glass, known as a Prism, it is found that, instead of a
single image of the luminous object, a coloured band of greater or
less length is obtained. The various colours may be recombined
in various ways, and are found to give, as a result, simple white
light. The spreading out of light in this way is called Dispersion,
and the power of producing it varies in different transparent sub-
stances. It affords evidence that white light is not simple, but
complex, and that the variously coloured beams which go to make
up a beam of white light are refracted by slightly different amounts
in the same refracting medium.

The coloured band, if the dispersion be great enough, is found
to contain the colours in the order, red, orange, yellow, green, blue,
indigo, violet. The red end is the least refracted, the violet end
the most. The coloured band is called a Spectrum.

8. — The mixing of various colours produces on the eye the effect
of some other simple colour tint, but the Spectroscope at once
shews that the colour seen is a mixture, not a pure colour. It has
been maintained that suitable combinations of vermilion, emerald
green, and ultramarine properly chosen can be made to give any
desired colour sensation. Others maintain the necessity for five
primary colours. The mixture of colours and the mixture of the

A CHAPTER ON LIGHT AND COLOUR. 105

pigments of certain colours are, however, entirely different means
of producing colour.

In the former case a compound sensation is produced indistin-
guishable from some other simple sensation. The latter effect is
due to absorption. Certain substances possess the property, either
when in solution, or when used to tint glass, of stopping a part of
the light which falls on them, while leaving the greater part of it
unaffected. Their colour, as seen by transmitted light, is the
effect of the light not absorbed by them.

If two such absorbent bodies act successively on white light,
they may abstract nearly all the colours from that light — in fact,
they may even abstract all, in certain cases. If a yellow and a blue
be used, the one colour not absorbed largely by either is green,
and hence the combination of yellow and blue pigments produces
a green pigment, while the combination of a pure yellow and a
pure blue light may produce a pinkish colour.

9. — The colours of the spectrum are, both as to their nature
and as to order, those shewn by the Rainbow. When sunlight
falls on the drops of water forming a cloud, it is partly refracted
into those drops. If it emerge after reflection at the back of the
drop, there is one particular direction in which the light is greatly
condensed. This direction varies slightly for different colours, and
hence the drops which send light to the eye in this direction give
the appearance of a coloured band, red on the upper side, violet
on the lower. Outside the bow there is complete absence of light
reflected from the drops.

After two or more internal reflections the light may emerge m
sufficient strength to produce other bows. The secondary bow is
frequently seen. It is larger than the primary, and the colours
are in the reverse order. The tertiary and quaternary bows are on
the same side of the observer as the sun and are drowned in his
light. The bows of higher orders are too faint to be visible.
• Curious eff*ects of Halos, Parhelia, etc., are produced when
ice-crystals take the place of raindrops in the cloud.

ic— The perfecting of the means of obtaining a sj^cctrum, by
using a slit as source of light, as Wollaston did in 1802, revealed
the fact that the spectrum was not continuous, but crossed by dark
bands, indicating a deficiency of certain kinds of light. Fraun-

106 A CHAPTER ON LIGHT AND COLOUR.

hofer in 1817 rediscovered these bands independently, and, using
a narrower slit, was able to map their positions. The chief of them
are still known by the letters A^ B, C, etc. ; a, b, c, etc., by which
Fraunhofer referred to them. It was found that if the light of the
sun were made to pass through the light of the electric arc
coloured yellow by sodium, the dark line (or pair of lines) D was
marked much more plainly than in the simple solar spectrum.

The arc tinged with sodium alone gave a bright pair of D
lines. These discoveries were made in 1849 t>y Foucault.

II. — The origin of these Dark Lines in the sun's spectrum
was not discovered till much later. About 1850, Stokes explained
the phenomenon by an analogy from sound.

We know that a tuning fork will, when sounded, excite another
fork of the same pitch, without touching it, and such a fork will
select from a composite sound the vibrations which it can itself
give out when sounded, thereby weakening that particular tone of
the composite sound. Similarly, bodies capable of vibrating at
such a rate as to emit light of a particular refrangibility will absorb
just that same kind of light from the radiations of a composite
character which fall on them. The absorbing body emits more
than it absorbs if its temperature is above that of the source of
light which falls on it ; but if below that temperature it absorbs
more than it emits, and causes a deficiency in light of that parti-
cular kind.

1 2. — The spectra of different bodies are found to be charac-
teristic of those bodies, and are one of the most delicate tests of
their presence. The researches of Kirchhoff and Bunsen in i860
led to the establishment of the law mentioned above referring to
the modification of light when passed through an absorbing
medium, and also to the laying down of the principles that

(i.) Incandescent solids and liquids (and, it has since been
found, highly compressed gases) give rise to a continuous spectrum.

(ii.) Gases under moderate pressure give spectra of bright
lines and bands separated by dark spaces.

The principles thus enunciated enable observers to detect the
presence of many well-known bodies, such as iron, magnesium,
sodium, and hydrogen in the sun and many stars and nebulae.
The element helium, not discovered on the earth till a couple of

A CHAPTER ON LIGHT AND COLOUR. 107

years ago, manifested its presence in celestial bodies in a similar
manner, and its existence in the sun has long been known.

13. — Bodies which are not self-luminous owe their visibility to
the Scattering of the light which falls on them, due to the
extreme irregularity of their surfaces. If they consist of material
so disposed as to reflect the incident light without considerable
selective absorption in the surface layers, as do snow, powdered
glass, etc., they appear of a more or less pure white. If the sur-
face layers are strongly absorptive, the scattered light is deficient
in particular colours, and the apparent colour of the body is
complementary to the colours absorbed. The light of the moon
and planets was believed for various reasons to be simply reflected
sunlight, and this conclusion is strongly confirmed by spectro-
scopic examination of these bodies.

14-— Diffraction and Interference.— The light from a lumin-
ous point spreads uniformly in all directions in an isotropic medium,
and hence its brightness falls off in the same proportion as the
intensity of a sound, i.e., in the ratio in which the square of the
distance traversed increases. If we consider the form of the
wave-front at any time, it will be the surface of a sphere. At any
subsequent time the disturbance at any point of space may be
calculated, either by reference to the original source, or to the
wave-front referred to. Each point of this wave-front may be
considered as the origin of a disturbance, and, by adding the
effects of these disturbances, the total effect at any desired point
may be determined. It is found that the eflect due to any small
portion of the wave-front is evanescent, except in the neighbour-
hood of the direction perpendicular to the front of the wave, and
thus the existence of rays is accounted for. This practical anni-
hilation of one effect by another may best be studied by beginning
with a simple case.

In all interference phenomena, the length of the wave of the
particular kind of light considered is most important. It is the
difference of wave-length of different colours which is the cause
of their different refraction, and consequently of the dispersion
produced by a prism, and the phenomena of interference are to a
large extent masked by the overlapping of the effects due to
differently coloured rays, resulting in a practical uniformity of

108 A CHAPTER ON LIGHT AND COLOUR.

illumination where homogeneous light would produce contrasts
of light and shade.

15. — To study the effect of the mixture of light from two
exactly similar sources, the light from a single source, as nearly as
possible a point, may be either reflected from two mirrors incHned
very slightly to one another, or refracted through a double prism
(called a biprism) of very small angle. The two images in either
case serve as the two similar sources of light.

If the Hght so reflected or refracted be received on a suitable
screen, the illumination is found not to be uniform. The centre
of the screen is brightly illuminated from each source .of light, but
in passing to one side, we reach a point where the light from one
source is half a wave-length behind that from the other, and con-
sequently in a condition to extinguish the effect of the first.
Hence a dark line is found at this place. Further on the differ-
ence of path is a whole wave-length, and a bright band results,
followed by other dark and bright bands alternately.

If the source of light be monochromatic, the alternations of
light and darkness can be well observed for some distance. By
measuring the breadth of the intervals between the bands, and
the distance of the screen from the source of light, the wave-length
of the light employed can be calculated. The scale of the effect
is larger for red than for blue or violet light, the breadth of the
bands gradually diminishing with the wave-length of the light
as we pass from red to violet. If white light be used, these
differences soon cause the contrasts to lose their sharpness, as the
bright bands of some colours fall on the dark bands of other
colours at a very slight distance from the centre of the screen.

16. — We see thus that the addition of Hght to light may pro-
duce darkness, and we may hence expect that the subtraction of
some part of the illumination due to a point of light may increase
the intensity of the brightness at some points in space. This
expectation can be proved to be well-founded.

By interposing an obstacle with a straight edge in the path of
the light falling on a screen from a luminous point, the effects
within the boundary of the geometrical shadow shew this strange
effect. The brightness outside the shadow does not abruptly cease
at its edge, but is succeeded by a series of alternations of bright-

A CHAPTER ON LIGHT AND COLOUR. 109

ness and darkness, some of the former exceeding in intensity the
uniform illumination outside the shadow. There are also bands
outside the geometrical shadow. As before, these are more con-
spicuous in monochromatic than in white light, and the scale being
different for different colours, the overlapping of the colours rapidly
destroys the clearness of the bands as seen by white Hght.

17. — Similar Bands of Colour may be observed within the
shadow of a narrow object such as a hair, or around the border of
the light falling through a small hole on a screen. A very strange
effect noticeable in the case of the shadow of a small circular
object is that, at determinate distances from the source of light,
the centre of the shadow is a bright spot, the colour of which
varies as the screen is moved towards or from the obstacle which
obstructs the light.

Even more strange is the effect produced when light falls
through a small circular aperture. At one particular distance of
the aperture from the source of light and the screen, the illumina-
tion at the centre of the bright spot is four times as great as if the
screen which contains the aperture were altogether removed, and
by doubling the size of the aperture, instead of increasing the
illumination, we obtain a black spot at the centre of the illumina-
ted space. These effects of interference are due to exactly the
same causes as in the case of sound, but the extreme smallness
of the wave-length of light, which may be taken to be about
i/5o,oooth of an inch for light of mean refrangibility, compared
with ordinary objects which produce shadows, and with ordinary
apertures, render them inconspicuous in general.

18. — The bands of colour obtained in Diffraction Phenom-
ena, when white light is employed, and before the mixing of
colours has masked all variation of intensity of light, may be made
to afford a spectrum of great purity, and the dark lines and bands
of the refraction spectrum are very readily studied in the diffrac-
tion spectrum when^ by due precautions, it has been made to
extend sufficiently in length. The measurements of wave-length
are more readily made in the spectrum as produced by this
method. For these purposes, the light is generally reflected from
a surface on which a series of equidistant parallel lines are ruled
very close together. Formerly, 3,000 lines to the inch was con-

110 A CHAPTER ON LIGHT AND COLOUR.

sidered sufficient for the purpose, but Prof. Rowland of Baltimore
has devised means for ruling gratings which contain nearly 30,000
lines to the inch. Spectra of great purity are thus obtained, and
the results are highly satisfactory.

19. — The colours of Mother-of-pearl and of Barton's
BUTTONS are due to the fine striation of the surface in either
case. Impressions of mother-of-pearl on black sealing wax shew
the brilliant tints almost as well as the original surface. Fine
powders, such as that of Lycopodium (the spores of Lycopodium
clavatum), when scattered on glass and viewed by transmitted
light, shew well-marked coloured rings, owing to diffraction, and
the rings seen round some stars, especially in small telescopes, are
due to the same cause. It is estimated that it would be impossible
to conceive of any microscope which would render visible objects
less than i/i 20,000th of an inch in diameter, owing to the inevit-
able diffraction effects connected with viewing them.

20. — Colours of Thick and Thin Plates.— If the front surface
of a mirror be covered with a finely divided substance, such as is
obtained by brushing it with diluted milk, the light which is scat-
tered at the first surface, interfering with that which has undergone
regular refraction into and out of the glass and reflection at the
back of it, produces a very beautiful system of coloured bands
surrounding the image of the source of light. If the mirror be
concave, the source of light being at its centre, the rings appear
to have a very remarkable fixity of position, independent of the
position of the observer.

21. — When a lens of small curvature is pressed against a plane
piece of glass, and viewed by transmitted or reflected light, there
is seen a system of brightly coloured rings surrounding the point
of contact. These are known as Newton's Rings. They are
produced by the interference of the light which emerges after
reflection, within the space between the lens and plate, with that
which is directly transmitted, or is reflected, at the first surface of
this space respectively in the two cases. The transmitted system
has a bright centre, the reflected system a dark centre.

In the arrangement of lens and plate, the variations of thick-
ness of the interposed layer of air follows a known law, and hence
the wave-length of light of different colours may be calculated

A CHAPTER ON LIGHT AND COLOUR. Ill

from the size of the rings of those colours. It is necessary to add
a retardation of half a wave-length at each reflection taking place
in glass at a surface separating glass and air, an addition which is
in perfect accordance with what would be anticipated by theory^
and is, in fact, necessary for the continuity of the motion. But
for this the centre of the reflected system would be bright, not, as
is the case in fact, dark. The above conclusion as to the position
of a given colour in the series is modified by this fact.

The iridescent colours given by a drop of oil or turpentine on
the surface of water, by the thin scales of the wings of some
insects, by thin films of mica and other readily laminated bodies,
and by soap-bubbles, are all due to the same cause. Two streams
of light, which in their passage to and from the thin film have
traversed paths of slightly different lengths, are brought to the
same point. At one place they strengthen each other; at a neigh-
bouring place the displacements due to them are opposed, and
they extinguish each other. For one thickness of the film the
difference of path may be an exact multiple of half a wave-length
for a particular colour, which will therefore be wanting at that
place, and the film will in consequence appear coloured. For
different thicknesses the colours will be different.

2 2.— Though the sensation of light is not produced by radia-
tions whose wave-lengths are greater than that of red hght or less
than that of violet, the nature of such radiation is not different
from that of the intermediate wave-lengths. Beyond the extreme
red end of the spectrum we find radiation which possesses the
power to heat bodies exposed to its influence, and m this part, as
well as in the visible part of the spectrum, there are evidences of
lines of absorption in the sun's radiation.

Beyond the violet end of the spectrum also, there are radia-
tions possessed of very strong actinic power, and capable of being
rendered obvious by their action on sensitive photographic plates.
Probably one reason why photographs of celestial objects some-
times shew details not visible to the eye is that they are due to
radiations of shorter wave-length than the extreme visible part of
the spectrum.

23.— Fluorescence.— Celestial photographs reveal faint stars
owing to a different reason. The eftect of a light sensation on

112 A CHAPTER ON LIGHT AND COLOUR.

the eye endures for no more than 1/7 th of a second. If an object
be so faint that the hght which it transmits to the eye in this brief
period is not capable of exciting the optic nerve, nothing is seen,
but the photographic plate may be exposed continuously for many
hours, and so, by the continued action of a feeble excitant, effects
may be produced which become visible. Besides affecting sensi-
tive plates, these ultra-violet rays possess the power of causing
certain changes in a large class of bodies known as Fluorescent
bodies. These bodies possess the strange characteristic of absorb-
ing radiations of short wave-length, and, by so doing, being excited
so as to emit radiations of wave-lengths sufficiently long to affect
the eye. Such substances are Sulphate of Quinine, Aesculin,
Petroleum Oil, Eosin, etc.

A somewhat similar phenomenon is manifested by the sul-
phides of Barium, Calcium, and Strontium, and some other bodies,
which, , when exposed to light for some time, are afterwards able
to emit light which can be seen in a dark room. The phenom-
enon is known as Phosphorescence, and has a practical applica-
tion in the manufacture of luminous paints.

24. — Besides actual changes of colour such as these, there is an
apparent change produced by the motion of the source of light in
the line of sight. The cause and the extent of the change are
determinable by exactly the same principles as in the analogous
case of the change of pitch of sound emitted by a moving body.
The phenomenon enables us to extend our knowledge of the
motions of the stars, and to measure their motion towards or from
the solar system with great accuracy. By this means, too, the
violent eruptions connected with the formation of solar spots are
rendered capable of measurement, and certain double stars which
are too distant to be separated by the telescope are known to be
double, from the fact that the spectroscope proves their light to
emanate from two bodies moving with different velocities.

25. — Though not directly connected with the subjects of this
article, the above phenomenon, and a further application of the
spectroscope to the study of solar physics are too important to
leave unmentioned. The sun was observed in 1842, when totally
eclipsed, to be possessed of appendages which created much
surprise, and a good deal of debate as to their nature and origin.

A CHAPTER ON LIGHT AND COLOUR. 113

Red flames were seen on the border of the ecHpsed sun, some of
which changed their form, while others remained apparently sta-
tionary. The study of these forms progressed but slowly, owing
to the rarity of the opportunity afforded by a total solar ecHpse.

In 1868, however, it was found possible to observe them in
full daylight, owing to the fact that their light does not give a con-
tinuous spectrum, but only a few bright lines. These lines are
not weakened by great dispersion, while the bright background of
sunlight can be rendered more and more faint by employing larger
and larger dispersive powers, and by the use of a suitable absorb-
ing medium. If, now, instead of allowing the light to pass
through a slit, the margin of the Sun's disc is* viewed directly
through the spectroscope, the bright lines produced by the slit will
be replaced by a succession of images of these jets of flame. By
this means the Prominences are now the subject of continuous
study. They consist very largely of hydrogen, and some of them
extend to 100,000 miles from the sun's surface, being, on occa-
sion, shot forth with velocities reaching to 100 miles per second,
or even beyond.

26. — The General Structure of the Eye is, briefly, as follows :

The eyeball is approximately spherical, fitting into a bony
socket, in which it is free to turn in all directions with but little
friction. It has a tough covering called the Sclerotic Membrane,
mostly white and opaque, but in front it is transparent, forming
the Cornea, This part is shghtly more protuberant than the rest
of the eyeball. The body of the eye is divided into two parts,
the anterior of whicli is filled with the so-called Aqueous Humour,
the posterior with the Vitreous Humour. These are separated
by the Crystalline Lens. The incident light is partially stopped
by an opaque screen, the Iris, in the centre of which is the Pupil,
which is circular in man, though of difi'erent forms in some other
animals. This part of the eye serves simply to bring the light
from external objects to a focus on the retina. At the back of the
eye, within the sclerotic membrane, is another coating called the
Choroid, and between it and the vitreous humour is the Retina.
Over the retina spreads a fine network of nerve fibres, uniting in
the Optic Nerve, which runs into the brain.

This layer of nerve fibres is followed by several other layers,

114 A CHAPTER ON LIGHT AND COLOUR.

containing granules, and finally we find the Bacillary T.ayer,
which consists of a set of elongated bodies, arranged radially, and
closely set together. These are of two kinds, known as Rods and
Cones. It is believed that the distance between two neighbouring
rods or cones determines the smallest angle between two bodies
which are just seen as two. The perception of light is due in
some way to the presence of the bacillary layer, for it is tolerably
certain that the nerve fibres overspreading the retina are incapable
of being directly excited by light vibrations. The general surface
of the outer ends of the rods and cones of this layer is in contact
with a layer of cells containing a black pigment, which is supposed
to serve the purpose of absorbing stray rays of light.

Californian Trap-door Spider.— At a meeting of the Academy
of Natural Sciences of Philadelphia, held June 23rd, 1896, the
Rev. H. C. Cooke reported a series of observations on the Califor-
nian Trap-door Spider, Cteniza Californica, made by Dr. Davidson,
who had been able to determine the time required for the construc-
tion of the burrow in confinement, and other matters connected
with the life-history of the animal. It had taken ten hours to
construct the nest with the hinged door, another spider having
made a hole large enough to conceal itself in two hours. The
method of digging was the same, in the main, as that described
by the speaker for the tarantula. The young, when they emerge,
at once build their own miniature nests, which are renewed every
spring, until they reach the full size. Based on his study of a
Lycosid, the speaker had predicted that the enemy of the Trap-
door Spider would be found to be a diurnal wasp. Dr. Davidson
has established the fact that such is the case, and that the attack-
ing species is Parapoviphilio planatus, Fox. — Science.

[ 115 ]

H IRapib fIDetbot) of (preparing Ipermanent
Sections for flDicroecoptcal Diagnoeie/'

By Dr. Ludwig Pick.

^T^HE technique used in our laboratory for the microscopical
A diagnosis of curetted or excised material allows the prepa-
ration of sections cut, hardened, stained, and preserved
within ten to fifteen minutes — often, even, in less time. The
rapidity of the method offers, among pther ''advantages, the possi-
bility of deciding important questions bearing on the pathology of
the case during the anaesthesia, or even after the operation has
begun, as we have often successfully proved.

We employ the Jung-Heidelberg Hobel (carpenter's plane), ether
spray freezing microtome, and, in fact, regard it as an integral part
of the method. It yields, with ease and rapidity, a large number
of fine, thin, and complete sections with very little waste of ether.

The curetted or excised material is freed from blood and
coagula by dipping in water and then brought directly on to the
freezing plate of the microtome and frozen. In order that the
freezing should be rapid and not too severe, it is important that
the mass be laid flat, and not be thicker than 2 or 3 mm. The
breadth is immaterial up to i cm. square, or even greater. The
ice-block so obtained in a few seconds must be merely firm, not
stone hard; the knife must cut through lightly and without grating.
Particles from curettage may be laid on the plate, a half-dozen or
more at once, and sections obtained from all at the same time.

The sections as they are cut are wiped from the knife-blade by
the finger-tip, floated into a 4 per cent, aqueous formalin solution,
and left there four minutes to harden and fix the cell plasma and
intercellular substance. The use of the finger instead of a brush is
to allow the warmth of the former to thaw the section before it
reaches the solution, avoiding in this way the formation of air-
bubbles in the tissue, which are often very annoying. As the for-
malin hardens at once, the disadvantages so often urged against
the freezing method — that is, fragility, loss of epithelial elements,

*From the British Medical Journal ^ Jan. i6th, 1897.

116 PREPARING PERMANENT SECTIONS, ETC.

and, above all, the poor staining quality of the sections — are done
away with.

From the formalin solution the section is carried directly into
a 4 per cent, alum-carmine solution, and left three to five minutes,
staining a deep red (4 g. carmine boiled three-quarters of an hour
in 100 g. 5 per cent, aqueous alum solution, cooled, filtered). For
transporting the sections from one liquid to another up to abso-
lute alcohol, a glass rod is used, about which the section is rolled,
obtaining a flat and even specimen much more quickly and con-
veniently than with a spatula.

The formalin section hardening and immediate carmine stain-
ing are emphasised as being the essential points of the method,
distinguishing it from others more or less similar.*

The section taken from the carmine solution is rinsed in pure
water to remove the superfluous stain, using the glass rod as before,
and then dehydrated by bringing it for fifteen seconds each into
80 per cent, alcohol and absolute alcohol. Finally, it is placed in
xylol carbol to clarify, and mounted and conserved in Canada
balsam. The unused sections and uncut material may be preserved
indefinitely in 80 per cent, alcohol, and subsequently stained or
embedded by any method, exactly as with primary alcohol
hardening.

With us the questions most frequently to be decided by micro-
scopical diagnosis are : — Malignancy or benignancy of tumours,
ulcers, etc. These are answered as efficiently and positively by
preparations obtained by this rapid method as could possibly be
obtained in any other way. Every one using the method will be
convinced of the exactness and distinctness with which the
preparations show the proliferation and change of form of epithe-
lium, abnormalities in number and development of glands, typical
and atypical gland forms, decidual cells, placental residua, etc.
Naturally, this procedure, which has been tested by us only in
gynaecological practice, would seem equally suitable for use in
other fields where a quick anatomico-pathological diagnosis is
required, and we hope that its wider use will confirm this view.

*T. D. Calluis, Centralb. f. allgem. path. u. Path. Anat., 1895.

[ 117 ] '^V ^.^.^K^

rv-

^be planet fIDare : 30 it 3nbabft

By W. D. Barbour,
Of the Leeds Astronomical Society.

AMONGST the myriads of Suns and Planets which throng
the vast abysses of celestial space on every side, is it
possible to conceive that this little Earth of ours, in pro-
portion like a grain of sand or a floating sunbeam mote, is the
only spot upon which life has evolved and human-like intelligence
dwells ? So extravagant a supposition is not only incongruous to
reason and opposed to analogy and continuity, but is also incon-
sistent with our conceptions of an all-wise, omnipotent Creator.
Thus encouraged by many sanctions, the astronomer could scarcely
aspire to a nobler discovery than demonstration, by objective
proof, of the existence in yonder skies of intelligent life consti-
tuted mentally, if not physically, like ourselves.

Hitherto, it has been supposed that the main essentials to
discovery lay in the size and excellence of the investigating tele-
scope. Experience has now shown that, all-important as quality
of telescope may be, the condition of the atmosphere through
which the light from the planet or star reaches the eye of the
observer, is the main factor which determines success. In har-
mony with this fact, the careful scrutiny to which Mars has been
subjected in recent years, has yielded the best results, not to the
largest telescopes, but to those of less aperture when erected in
lofty positions away from large populations and atmospheric
impurities. But even here, another difficulty confronts the obser-
ver which he cannot control. The diverse temperatures and cross
currents of the different air strata, extending to many miles above
our heads, interfere more or less with direct passage of the light-
rays downwards to the telescope. Thus, instead of clearly defined
surfaces of planets and round discs of stars, we have blurring in
the first instance and distortion in the second. These difficulties
the astronomer meets with endless patience and watchfulness,
waiting for those brief intervals, often one to three seconds only,
when the'-overhead atmosphere is steady and without cross-currents.

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. i

118 THE PLANET MARS: IS IT INHABITED?

These precious moments are the astronomer's opportunity and
reward. The finer details of the planetary surfaces come out with
startling distinctness, and he sees in a moment that which hours
of the intensest gazing had failed to reveal. Thus, it came to
pass that Schiaparelli's " Canals in Mars," partially discovered
nineteen years ago, were largely treated, even by astronomerSj as
myths of the imagination. But just as truth can always afford to
wait, so vindication came at last from the pellucid air of Arizona,
where three astronomers at the Observatory at Flagstaff, East of
California, watched the planet Mars from May 24th, 1894, to
April 3rd, 1895. During that time, to mention nothing else, nine
hundred and seventeen drawings and sketches were made. And
since the date named, it may be added, confirmation and new
discovery have served but to endorse the general accuracy of the
observations of the astronomers referred to.

As a rough approximation to the visibility of Mars, when
telescopically examined, we may here say that an opera-glass,
magnifying three or three and a half times, shows our Moon about
as plainly, and with detail similarly pronounced, as a colossal
telescope, eighteen or twenty inches aperture, under the highest
favourable conditions and in exceptional moments, would, with a
power of say four hundred, reveal to us the markings on the
planet Mars. Young amateur telescopists may be interested in
knowing that the writer, with his four-inch aperture, achromatic,
in Leeds outskirts, while observing Mars in December, 1896,
between one and two a.m., during one of those brief precious
intervals of atmospheric steadiness, saw distinctly (using diagonal,
Mars being in Taurus, and near zenith) what he recognised as
Syrtis Major skirting the Eastern limb, also shimmering darkish
bars upwards to the right which he identified as Oceanus, Mare
Icarium, and long arm of Margaritifer Sinus, the whole covering
an equatorial width of three or four thousand miles. Mars at this
observation was more than fifty-three millions of miles away, a
distance which an express train, travelling fifty miles per hour
continuously, would require more than a hundred years to traverse.
One of our Members (Mr. Townshend), with his nine and a half
inch reflector, it need scarcely be added, has seen much more on
the planet than what is described above The polar snows, when

THE PLANET MARS: IS IT INHABITED? 119

of considerable size, are easily visible in a good telescope, five or
six feet in length.

The first recorded drawing of Mars is one by Huyghens,
November 28th, 1659, and is faithful enough to be now recognised
as the Syrtis Major. In recent years, many drawings of the planet
have been made (some of which appeared in the Transactions of
the Leeds Astronomical Society for 1894, one showing the dark line
bordering the snow-cap, which Mr. Lowell comments upon at
length, named the " South Polar Sea"), but not until the astrono-
mers named, with whom we must associate the Italian, Secchi,
concentrated their unwearied energies upon the question, Did
Mars divulge, what appears to many, the life secret of its end
and destiny?

The three principal features upon Mars, its snowy caps and
light and dark areas, had long been observed, studied, and
commented upon. Many strange discrepancies, however, were
noted. Light and dark areas were seen at one time, and not at
another. The colours assigned to them also varied. To Hum-
boldt they were a puzzle ; Secchi says, " bluish, owing to absorp-
tion ; and orange, sometimes dotted with red, brown, and greenish
points " ; Beer and Madler, " dull grey green " ; Proctor and
Parkes, "ruddy and greenish"; Lockyer, "reddish and greenish";
Guillemin, " reddish and dark bluish." These observations we
now know to have been just and accurate ; but the cause of these
differences, partly one of personal equation, has now, as will
appear hereafter, received an explanation which harmonises well
with other recorded facts and theories.

To the three prominent features above named, the Italian and
American astronomers, undoubtedly favoured by the purity and
transparency of their local atmospheres, have added two more of
absorbing interest. Scores of fine delicate lines have been seen
and located. Out of one hundred and eighty three so-called
" canals," nine have been seen once, seventy-nine two to nine
times each, and ninety-four from ten to one hundred and twenty-
seven times each. Sixty-four spots, some circular and some oval,
have also been located. Very significantly, the lines seem, with
scarcely an exception, to be prolonged from spot to spot, each
spot being the junction or centre whence radiate from two to nine
of the " canals."

120 THE PLANET MARS: IS IT INHABITED?

Mr. Lowell draws attention to three remarkable characteristics
of these lines : i. — Their unnatural straightness, so diiferent from
anything of the kind observable upon Earth. Almost invariably
they are arcs of great circles. 2. — Each line appears the same
uniform width throughout. 3. — No line is absolutely isolated,
which means that, starting from any point on any line, the whole
network of lines might be successively traversed. In regard to
these characteristics, it may be observed that angularity or devia-
tions from straightness, also intervals or interruptions in the canal
system, even to the extent of fifteen miles or more in each case,
would not be perceptible from Earth in the best of telescopes.
Such deviations, rendered necessary to round hills here and there,
are indeed to be expected j but nothing conceivable in the canal
system would necessitate absolute discontinuations. Stretches of
sandy desert might indeed occur here and there, useless for irriga-
tion purposes, but through which the water could easily be
conducted without loss.

Perhaps the most inexplicable phenomenon upon Mars is the
gradual widening, then doubling, or splitting in two, of what at
first appeared as a single ordinary canal. Mr. Lowell's map shows
seven of these double canals, the distance between the lines in
each case measuring from one hundred and twenty to one hun-
dred and seventy-five miles, the intermediate country being of an
orange-ochre tint. From the fact that other lines appeared on
the point of doubling, and others, again, very broad, it may turn
out that doubling is rather the rule than the exception. Mr. Lowell
believed the doubling (one or two cases of tripling have been
recorded) to be seasonal and vegetal. The theory is plausible,
though unsatisfactory, he thinks, which sees in the slow divergence
of the lines a progressive growth and decay, as the lines of vege-
tation recede from each other. In every case, he says, the lines
appear straight and exactly parallel ; and the better they are seen
the straighter they appear. The solution of this strange doubling
cannot fail to be significant and intensely interesting when it comes.

One of the most telling points in Mr. Lowell's contention that
the dark areas are not water, is the discovery that dark lines
and dark spots are not confined to the light reddish or sandy-
coloured regions, but prevail also in the dark regions ; in fact, the

THE PLANET MARS : IS IT INHABITED ? 121

lines in the light regions converge to a remarkable extent to the
obtruding peninsular points in the dark regions, from whence,
after repeated crossings, they are continued in new dark lines,
each measuring from about one thousand to two thousand two
hundred miles, up towards the South Pole. Owing to the bending
of the South Pole towards our Earth at the last opposition (Octo-
ber, 1894, a position which will not again occur for fifteen years),
and the consequent bending away of the North Pole, it could not
be ascertained whether similar lines converged towards the latter.
The width of the lines Mr. Lowell estimates at fifteen miles for
the finest, up to forty-five or more for the broadest. In length
they vary from two hundred and fifty miles to one thousand five
hundred miles ; and in one instance, involving ten oases in a
straight line, to three thousand five hundred and forty miles ; that
is, longer by one thousand miles than a straight line from Leeds
to our North Pole. The spots, or oases, in the deserts of Mars
vary in diameter from seventy to one hundred and fifty miles, the
larger* forming the majority. The largest of all, Solis Lacus (Lake
of the Sun), is five hundred and forty miles long and three hun-
dred broad. Remembering the width of these lines (fifteen to
forty-five miles), it is obvious that a city like London, say fifteen
miles in diameter, upon Mars, would be quite invisible to us in our
largest telescopes. Why these marvellous spots and intricate lines
should have remained undiscovered from Herschel's forty feet
Reflector in 1789, and Rosse's gigantic fifty-four feet in 1845, till
Schiaparelli, in the Italian sky, with an eight and a half inch
aperture, detected them in 1877, we have already explained.
That they may have been seen, and yet not recorded, is of course
possible, remembering their seasonal character and fitful appear-
ances, and to that extent their difficult identification.

To a correct understanding of the enormous areas covered by
the supposed deserts, ancient sea-bottoms, spots, and lines visible
on Mars, let us make a comparison. Our Earth is seven thousand
nine hundred and eighteen miles in diameter, twenty-four thousand
eight hundred and seventy-five miles in circumference, and in
superficial area one hundred and ninety-seven millions of square
miles, of which one hundred and forty-six millions are water,
leaving fifty-one millions land, including North and South Polar

122 THE PLANET MARS: IS IT INHABITED?

regions. Mars, a much smaller planet, is four thousand two hun-
dred and fifteen miles in diameter, which, multiplied by its circum-
ference, thirteen thousand two hundred and forty-one miles, shows
its area to be nearly fifty-six millions of square miles, from which,
deducting an average of six and a half millions for North and
South snow-caps, we have forty-nine and a quarter millions of land
only, which is more than the entire land area of Europe, Asia,
Africa, and America combined. It will surprise many to know
that out of the entire land area of our Earth, viz., fifty-one milHons
of square miles, about twenty millions have not been explored at
all, estimated thus : — Africa, six and a half millions ; Arctic and
Antarctic regions, nine millions ; other parts, four and a half mil-
lions. As would appear from the extent of country covered by
lines, our Martian cousins may be far ahead of us in the work of
exploration.

An important correction to our former beliefs lies in the dis-
covery that the large dark areas on Mars are not seas, but in all
probability the bottoms of ancient seas, which are flushed at
certain seasons by extensive freshets from the melting snows at
the North and South Poles. These waters, never apparently very
deep, disappear during summer and autumn, being either absorbed
by vegetation and the subsoil, or vapourised into the atmosphere.
We thus arrive at the pregnant inference, if Mr. Lowell's observa-
tions be confirmed, that a great scarcity of water exists upon Mars,
at least upon the surface, and as scarce there as it is plentiful with
us. Referring again to the strange periodical disappearance of
the dark areas, also the various changes in colour, recent observa-
tions not only confirm these variations, but add similar changes in
colour and visibility of the spots. Some hidden unknown cause
was here at work. That large markings should come and go in
this way, showed changes to exist on a scale involving a large
portion of the planetary surface. In a correct interpretation of
these changes evidently lay the key to the unlocking of the mystery
of Mars. The exhaustive scrutiny of astronomers during the past
forty years, culminating in those of Schiaparelli and the Arizona
observers, may turn out to have brought us within measurable
distance of the true solution.

Geology tells us that our oceans are gradually filling up with

THE PLANET MARS: IS IT INHABITED? 123

the soil and detritus ever being carried down from mountains and
lowlands by means of streams and rivers. The same story of
denudation and wearing down, we now have reason to believe,
was long ago enacted upon Mars, with the ultimate result, as
seemingly proved by Mr. Lowell (discussed and allowed^ also, from
a geological point of view, by Mr. P. F. Kendal, F.G.S., in an
illustrated lecture before the members of the Leeds Astronomical
Society last year), that the surface of Mars is now nearly level,
its oceans having retired into the interior ; and yet not alto-
gether so, for the saturated, though now extremely attenuated,
atmosphere of the planet still continues its circuit, depositing
its watery treasure in the form of snow or hoar frost, during the
long polar nights. With returning spring, these snows are observed
to melt ; and the water, which appears in the telescope of a deep
blue colour, to collect as a ringed sea, three hundred and fifty
miles wide, surrounding each pole.

That Mars is not exactly level, however, but has hills, at any
rate, near the South Pole, more or less perpendicular, is shown by
Mr. Lowell's observation on June 7th, 1894, about one hundred
and thirty-five days before opposition. Suddenly, two points like
stars flashed out in the midst of the polar cap. Dazzlingly white
on the snowy background, they shone for a few moments and then
slowly disappeared. These afterwards proved to be gleams of
Sunlight, reflected from steep ice slopes, flashed earthward, just as
in a railway train we sometimes see the light of the Sun reflected
towards us for some moments from a distant glass conservatory.
As this ice slope was near the pole, answering to Victoria Land
near our South Pole, the Sun must have appeared near the horizon,
from those shining points on Mars. The same eminences were
afterwards observed as ice or snow patches amid dark surround-
ings, suggesting a colder elevation, like the snow on our hills,
which remains days, sometimes weeks, after the snow in the sur-
rounding valleys has melted. It turned out that these ice flash-
lights had been seen in 1846 and 1877 ; also two others in addition.
In connection with these, many will recall the supposed light-
signals from Mars, which gave rise to so much speculation at the
time. Martian astronomers may possibly be familiar with similar
Sunlight reflections from our lofty regions of eternal snow and ice.

124 THE PLANET MAES: IS IT INHABITED?

Three great dark rifts were also seen during the last opposition of
Mars, one increasing in nine days from one hundred miles to
three hundred and fifty miles. This again points to the existence
of hilly portions near the South Pole, the dark rifts doubtless
showing where the ground was low, and from which consequently
the snow had disappeared most quickly.

During the opposition named, 1894-5, it was remarked that the
South Polar Cap did not extend symmetrically round the pole. In
long. 206, the snow extended only to lat. 71, or 19 degrees (six hun-
dred and ninety-eight miles) from the Pole, answering to our North
Cape ; whereas in longitude 26 it extended to 54^, or 35^ degrees
(one thousand three hundred and four miles) from the Pole, answer-
ing to our British Columbia. Comparing these with our terrestrial
snows, we note that here in Yorkshire, 36 degrees (two thousand
five hundred miles) from North Pole, we have frequently rigorous
winters of snow and ice; and even in New York, 50 degrees
(three thousand four hundred and seventy-five miles) from the Pole,
the snowstorms are now and then appalling in their severity. It
should be remembered that a degree on Mars measures thirty-six
and three-quarter miles, against sixty-nine and a-half miles upon
Earth. Why the Martian snow-caps should thus extensively
diminish in area during summer (actually disappearing in 1894,
for the first time known to astronomers), as proportionately con-
trasted with the perennial ice-caps of Earth, has not yet been
satisfactorily explained. According to accepted theory, the cold at
the Martian poles, owing to much greater distance from the Sun
than Earth, also to the thinness of its atmosphere, should be con-
tinuously much more severe — that is, far below freezing point. A
partial explanation has been found in the thinness of the ice-coat-
ing, due to the limited quantity of water-vapour which its atmo-
sphere can carry and deposit as snow ; also, in the absence of a
deep Arctic ocean, in which more ice would, almost certainly, be
formed in winter than could be melted during each succeeding
summer.

Some years ago, as many of our readers will remember, there
was much talk amongst a section of the public about signalling to
Mars, by arranging upon some vast plain certain geometrical
figures, which, when seen by Martians, would testify to the exist-

THE PLANET MARS: IS IT INHABITED? 125

ence upon Earth of an intelligent and cultivated people, and
should amount to a prehminary invitation to further correspond-
ence. Such people were unaware that, even if the idea were good
and promising, such lines would require to be four hundred or five
hundred miles long and some fifty miles broad. But oh, the irony
of the matter ! Here, Terrestrials, in their simplicity, have been
discussing how to open communication with Mars, and all the
while, these supposed cousins of ours, in their intricate and scien-
tifically arranged network of vast engineering schemes, extending
over thirteen thousand two hundred miles by at least three thou-
sand six hundred and seventy-five miles, thus setting absolutely at
naught our most gigantic achievements, have been practically sig-
nalling to us for, not only hundreds, but quite possibly thousands
of years ; and if their astronomical at all equal their mechanical
and engineering skill, they have doubtless been watching and
waiting for some responsive sign that beings, of intellectual cafibre
equal to themselves, existed upon Earth.

We gather from Mr. Lowell's observations that this polar sea
water not only flows out on all sides towards the Equator, thus
irrigating the large dark areas, but by means of gigantic canals is
tapped, conveyed, and distributed to the numerous oases or junc-
tions in the reddish ochre desert regions, which seem to serve as
centres for the further distribution of the precious liquid. At the
1894 observation, these canals were first observed on May 31st
(after Mars' Vernal Equinox on April 7th, 1894), in the dark areas
about the Syrtis Major; and soon after this, in June, there
appeared, as the result of the snow melting, " one continuous belt
of blue-green, obliterating the whole intermediate reddish-ochre
regions, and stretching from the Syrtis Major to the Columns of
Hercules." After this, their history was one long fading out, from
various shades of colour, interspersed with glints of orange-yellow,
until finally, with some intermittent changes, the spring and
summer verdure had changed to an orange-ochre. The long dark
fines which in June had joined the Polar Sea to Syrtis Major, had
also by October nearly disappeared, and a month after this what
remained of the more Southern dark areas had faded, so as to be
scarcely perceptible. To the question, What causes these vast
and wholesale changes from blue-green to orange-ochre? Mr. Lowell

126 THE PLANET MARS : IS IT INHABITED ?

replies that no theory about water and its reflection of light can
explain them. Professor Pickering's polarising experiments on the
light from these blue-green areas, made some years ago, and
repeated along with Mr, Lowell, also ended in the same verdict.
The only thinkable alternative, therefore, is that the colour-changes
are caused by the seasonal development of vegetation from green
through bloom to the " sere and yellow leaf" of decay. It need
scarcely be added that the lines which the telescopist sees, are not
the " canals " or water-courses, but the fringes of vegetation bor-
dering the " canal," and extending for some eight to twenty-five
miles on each side. As regards the general order in degree ot
visibility, it is noticed that the first areas, lines, and oases to become
deeper in tint, are those nearest the polar snows ; those near to
the Equator being the last (except those running east and west) to
receive the benefit from the Martian annual freshet.

The question will occur here to many minds : — Like as Earth
contains, in addition to springs, reservoirs of fresh water every-
where near to its surface, and which are available for human con-
sumption, may we not suppose that on Mars, a planet so analogous
in many respects to Earth, a similar provision may exist for the
necessities of its supposed inhabitants ? From the fact that Mars
is a much smaller planet (in volume 15, in mass 11, in density 72,
in diameter 53, and in surface 28, each against Earth's 100), and
therefore having cooled much more rapidly than Earth, we may
reasonably conjecture that near its surface it is more extensively
honeycombed ; and therefore that its reservoirs of rain-water are
proportionately more numerous. Against this theory we have the
fact that Mars, as an inhabitable planet, must be enormously older
than Earth, and therefore that its initial stores of water may have
drained too deeply inwards to be accessible. In the supposition,
also, of an ever-increasing drought during thousands of years in
the past, it is open to us to conceive that the inhabitants may
have been drawing, largely and continuously, upon these internal
stores of the precious fluid.

The entire evidence, including that from analogy and contin-
uity, thus goes to show that we are here dealing with a world
substantially like our own in origin, history, elementary compo-
sition, and structure, but much older than Earth, and therefore

THE PLANET MARS : IS IT INHABITED ? 127

differing in detail, such as density of atmosphere, quantity of
water, cloud formations, and contour of surface. But on the face
of the planet we see something startUngly unlike anything upon
Earth, and having no resemblance to geological or glacial cracks,
volcanic rents, river ways, or the coursing impact of tiny plane-
toids. A strange gigantic network of lines encompasses the entire
globe. Apart from artificiality, they stand utterly opposed to
reason and explanation. They are matched only by the fabulous
deeds of the mythical gods of old.

Thus seemingly compelled to accept the evidence for these
superhuman-like structures, it by no means follows that our
Martian neighbours are necessarily prodigies of mind and body
as compared with ourselves, or rather, with what we might attain
to by lives of righteousness and culture. Rather the contrary,
indeed, if size of habitat and similarity to our own environment
are to count. And another objection must be reckoned with.
The Martian atmosphere is excessively tenuous, much thinner
even thaft that on our Himalaya Mountain tops. No clouds of
consequence ever veil its surface. If, therefore, mental and phy-
sical labour are to be construed in terms of consumption of carbon
and of other chemical elements, as in our own case, we must
conclude that the Martian lung capacity is either much larger or
more active than with us, to produce a like equivalent of work.
How then, with these drawbacks, are we to account for the
Martian ability to execute such colossal designs ? To this we
reply : i. — That the feebler gravitation on the Planetary surface
(38 against Earth's 100), necessarily increasing the ease of mus-
cular exertion, may largely compensate for atmospheric deficiency
in oxygen, the inbreathing of this element in sufficient quantity
conditioning the amount of animal life and activity. 2. — Given
the gradually increasing necessity for such works, during, say, tens
of thousands of years, " time being thus on their side," the
superhuman element to account for them becomes superfluous.
" Strength for their day " would be the lot of each generation.
What is suggested in these stupendous evidences of a civilisation
possibly exceeding our own, is the existence of some constitu-
tional peculiarity in the planet or its inhabitants, or, on the
other hand, some relentless antagonism in the forces of nature.

128 THE PLANET MARS : IS IT INHABITED ?

which are now being successfully combated by the united energies
of an entire world.

And now, in summing up, as to the meaning of all this.
These lines, parallels, and round or oval spots (which exuberant
fancy might easily endow with a martial meaning), cannot mean
the unconscious working out of nature's laws, such as we see on
the rugged surface of our Moon, or in the lonely uninhabited
regions of Earth, for in Mars we see order, not disorder ; method,
not chance ; arrangement, not confusion. What impressed Mr.
Lowell, as he sketched by the side of his telescope, during the
still hours of night, was the obvious unity of design and purpose,
with the high order of intelligence and skill, which are evident
in these enormous works, compared with which our Suez and
Manchester Canals are absolutely insignificant. He describes
them as " uncanny " in their aspect, such being his impression of
their living or life-like origin. Acquiescing then, for the present,
in Mr. Lowell's interpretation and verdict, we inquire further —
For what purpose all this world-wide expenditure of mental,
physical, and mechanical power ? Our answer, whatever it is,
must involve a necessity equivalent in urgency to a fight with
death. And so it is. An ever-threatening famine of water seems
the inevitable lot of our Martian cousins. This is their "struggle
for life ; " world-wide as the air they breathe, involving all classes,
peoples, and tongues ; and written as with a pen of iron on the
face of the planet itself. Like as community of interest tends,
where confidence dwells, to harmony and unity in council, so
these wonderful structures suggest to us mutual faith and co-opera-
tion on a scale of unparallelled grandeur, before which national
jealousies must sooner or later sink and disappear. Unification
and inter-dependence of the entire canal system become the
pledge of universal peace. Thus we see, as of old, " the curse
turned into a blessing." Just as a famine of water, made possible
at any moment by destruction of the waterways, means death
everywhere to vegetation, animal life, and man or his Martian
congener ; and just as one touch of sympathy, suffering, and
self-sacrifice tends to make divided communities, nations, and
even distant worlds, " one kith and kin," so we may hope that
strife and bloodshed, with selfishness the bane of life and root of

BRITISH hydrachnidj:. 129

evil, if ever these have cursed the soil of Mars, have ere now
passed away ; and that " peace and good-will," revealed from
above, now reign in that world of life.

By Charles D. Soar. Part VII. Plate VII.

Genus IX., Atax (Fabricius).
1805. — J. C. Fabricius, Systema antitatorum, p. 364.

THE chief distinguishing features in the genus Atax may be
briefly described as follows : — The epimera are arranged in
four groups ; the eyes widely separated ; the legs are fur-
nished with* swimming hairs; and it will be noticed that there are
claws to all the feet. This hydrachnid is soft-skinned. The
anterior pair of legs is fitted with powerful jointed hairs, the
jointed base of each hair being let into a prominent and specially
projecting socket.

A great number of so-called species of this genus have been
figured and described by various Continental acarologists. Koch
figured a great many, but on careful examination the majority of
them have been found to be the same species under different
names. In 1894 Dr. Piersig made a new genus of certain species
which had always been previously regarded as true species of the
genus Atax, which he named Cochleophorus. But this will be
referred to later on.

I can find very little information about Atax in any Enghsh
works treating on the subject. Murray, in his Economic Entomo-
logy, p. 154, has but very few words to say about it. He mentions
four species, three of v^hich are very doubtful. In the fourth edi-
tion of the Micrographic Dictionary, p. 85, will be found a very
good description of the genus ; it, however, gives but little infor-
mation about the different species. On PI. VI., Fig. 14, it also
gives a figure of a Limnesia under the name of Atax histrionicus.
This is an error that Murray also falls into, but which is not at all
to be wondered at when we consider the scanty information
available at the time those notes were written. The Journal of

130 BRITISH HYDRACHNIDiE.

the Royal Microscopical Society^ 1871, p. 184, and The Annals of
Natural History, Jan., 1871, p. 55, have a few observations on a
species of Atax parasitic upon fresh-water mussels by Emil Bessels
which are worth reading, and are very interesting. Science Gossip,
1883, p. 180, has a short article on Atax by Dr. George, in which
he figures and describes the swimming hairs so peculiar to this
genus. This completes the list of English papers so far as my own
knowledge goes, but on the Continent Atax has received some
considerable amount of notice. Van Beneden, in 1848, published
a paper on the " Development of Atax ypsilophora,^' which has
received a great deal of attention, and justly so, for it is well
written and well illustrated, and was the result of several years'
devotion to the study of these interesting creatures. Koenike also
has a paper on Atax in Abha?idl. d. ?iaturwiss. Verei?i zu Bremen,
1882, without figures. Besides the above, the species we are
about to consider has received a great many notices, and has been
recorded a great number of times, as will be seen by the following
list; but regardless of the frequency with which it has been
recorded, we must add one more paper to the list : —

Atax crassipes (Miill.). Bibliography and synonyms :

1776. — Hydrachfta crassipes, Miiller, Zool. Dan. Prodr., p. 189,

No. 2254.
1 78 1. — Hydrachna crassipes, Miiller, Hydrachfice, p. 4r, PI. IV.,

Figs. I — 2.
1793. — Tro7nbidium crassipes,^. C. Fabricius, Ent. Syst., II., p. 400.
1805. — Atax crassipes, J. C. Fabricius, Sy sterna Antliatorum, p. 366.
1835-41. — Atax crassipes, C. L. Koch, Deutschlands Crust., etc.,

p. 7, Fig. 2 1.

Atax truncatus, as above, p. 7, Fig. 22.

Atax ahbidus, as above, p. 7, Fig. 23.

Atax truncatellus, as above, p. 37, Fig. 17.
1842. — Atax crassipes, C. L Koch, Uebersicht des Arachniden-

sy stems, S. 7, Tab. i. Fig. i.
1854. — Atax crassipes, Bruzelius, Beskr. 6. Hydrachn. som. Farek.,

p. 8, Figs. 1—4.
1868. — Atax crassipes, Claparbde, Zeitschr.f. Wissenschaftl. Zool.

Bd. XVII., p. 471.

BRITISH HYDRACHNIDiE. 131

1875. — Atax crassipes, Kramer, Beitr. zur Naturgesch. des

Hydrachmder, p. 293, Twf. VIII., Fig. 4.
1879. — Atax crassipes, Lebert, Description D. Hydrachnides du

Leman, p. 45, PI. XL, Figs. 10 — 10a.
1880. —Atax crassipes, C. J. Newman, Sveriges Hydrachnider,

PI. XXL, Tab. I, Fig. i.
1882. — Atax crassipes, G. Haller, Die Hydrachniden des Schweiz.,

p. 76.
1885. — Atax crassipes, Krendowsky, Hydrachniden of Russia, p. 55.

Average length of body, about i"2o mm. Average breadth,
about 0*92 mm. Average length of legs: — ist pair, 370 mm.;
2nd pair, 3-50 mm. ; 3rd pair, 2-56 mm. ; 4th pair, 3*30 mm.
Average length of palpus, 0*84 mm.

Colour. — A pale yellow, with brown markings on the dorsal
side, with a yellow X-shaped piece in the centre. The eyes are
sometimes dark red and sometimes they are dark brown in colour.

The legs in some cases are quite transparent and colourless ;
in others they are a deep slate blue. In the autumn of 1896 I
took some specimens in Wales, which were very deep in colour.
It was, no doubt, this difference in the colour which led Koch to
think they must be different species. The form of the upper
or dorsal side of body is a long oval, truncated on the posterior
margin ; at each angle of the truncated margin is a small projec-
tion (see PI. VII., Figs, i and 3). The projection on the legs I
consider a peculiarity of this mite. The legs are long ; the first
pair are thick at the first and second joints. These joints, or
rather internodes, are fitted with the powerful spines or hairs
which we find on no other mites but members of this genus. They
are thick near the body, and gradually taper towards the tarsi.

The second pair of legs are the longest, which is a very
unusual thing in mites. The second pair measure 0*94 mm.
longer than the third pair of legs, and 0*20 mm. longer than the
fourth "pair. The second, third, and fourth pairs of legs are all
slender, and not at all like the first pair, in which the femur and
trochanter are so much enlarged. There are two claws to each
tarsi (see Fig. 6).

Palpi (Fig. 4) are rather long, the second joint being the
thickest. The third is small. The fourth has three pegs — two on

132 BRITISH HYDRACHNID.E.

the inner side and one on the outer. The apex of two, if not
three, of these pegs is furnished with setae.

Texture. — The cuticle of the body is soft and easily distorted.
The legs, palpi, and epimera are hard and chitinous.

The difference in the male and female is very small. The
body of the female is a little more round than that of the male,
and the first pair of legs of the female appear somewhat coarser
than those of the male ; but otherwise the only noticeable differ-
ence is in the genital area. Fig. 4 showing the female, and Fig. 5
the male.

Distribution. — This species may be considered as fairly
common. I have taken it on several excursions round London,
and found it common on the borders of Llyn Padarn, N. Wales.
I found it in the rivers in Suffolk, and have had it sent to me from
many other places by collectors. The specimens the drawings
were made from were taken by me at Snaresbrook on Sept. 19,
1896. They were fine, well grown specimens, but possessed very
little colour, the legs and edge of the body being nearly trans-
parent. I have always taken it from clear water in ponds and
rivers.

I have kept a quantity of these mites at home alive for some
time, but have never yet had any ova deposited in the tubes, so at
present the larva is quite unknown to me. In swimming, they
swim upwards ; they then extend the legs to the fullest, and rest,
as it were, for a few seconds in the water, as if lifeless, then
gradually drop towards the bottom.

EXPLANATION OF PLATE VIH

Fig. 1. — Dorsal surface of , 9 .
2. — Ventral surface of ^ .
3. — Ventral surface of $.
4. — Genital area of 9 .
5. — Genital area of $,
6. — Claws of first foot.
7. — Palpus of 9 .

Journal of Microscopy 3^- SerVol. 6, Plate 8.

-. ¥

Ataa^ crassijp^s /'Mu/ZerJ

O'Aas. /?.S/?ar ac/.>70f. c/s/.

F. P^////ps Sc.

[ 133 ]

Xeavee from m^ IRote^Booft:

Strange Adaptations to the Environment in Water Insects.

By Mrs. Alice Bodington.

I HAVE lately been reading a book* which has much interested
me, and which has set me thinking about the strange and
wonderful adaptations of some of the tiny creatures inhabiting
our streams, ponds, and ditches, to their strange and peculiar
environments. Some of the facts in the following paper are
gleaned from this book, others from my various readings and
personal observation. The illustrations are kindly lent by Messrs.
Macmillan and Co.

There is something so extraordinary in the manner in which
Water Insects are suited to the life which they have to lead, that
one might almost suppose some inteUigent power controlled the
development of each species without regard to the welfare of any
other species ; since the adaptation of murderous weapons for
seizing and destroying prey are amongst the most salient charac-
teristics of most of these organisms. The film on the surface of
water plays an important part in the lives of many water insects.
The film, which to our tactile sense is impalpable, is for some
creatures a dense medium on which they can execute the maddest
gyrations ; to others it is a solid crust, under which they can run
upside down ; some insects have organs adapted for piercing this,
to them, solid film, so that they can breathe atmospheric air
through the hinder part of their bodies, whilst their heads are
engaged under water in an active search for prey.

A curious vital process is seen in the manner in which the
tracheal tubes of aquatic insects become filled with a gas^ probably
rich in oxygen ; an apparatus which, without rise of temperature,
or diminution of pressure, will remove dissolved oxygen from
water, and store it up in a gaseous form within a closed chamber.
Other aquatic animals have a similar faculty ; and that this pro-
cess of obtaining a gaseous mixture is a vital and not a purely

* " The Natural History of Aquatic Insects," by Professor L.
C. Miall, F.R.S., with illustrations by A. R. Hammond, F.L.S. Cr. 8vo,
pp. ix. — 395, (London: Macmillan & Co. , 1895.) P"<^^ ^/'

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. k

134 LEAVES FROM MY NOTE-BOOK.

mechanical one, is shown by the fact that the air-bladder of a fish,
when punctured, will refill with a gas containing as much as eighty
per cent, of oxygen ; but if the branches of the vagus nerve
which supply the air-bladder are cut, no more gas is formed. Nor
could oxygen be made to diffuse into the air-bladder of a Pike
which was filled with atmospheric air and surrounded by pure
oxygen, //// the epitheHu7ti had been killed by maceration in distilled
water.

The fierce larva of the Dytiscus beetle is a kind of sabre-
toothed tiger among insects ; its sharp curved mandibles are
grooved like the poison-fangs of a serpent, and are formed into a
tube by the closure of the maxillae. Whilst the blood of the living
prey is being sucked by pharyngeal action through the tube so
formed, the maxillae at the same time act as a mouth-lock.
When the Dytiscus wishes to swallow a solid morsel, the maxillae
are relaxed and leave the orifice of the mouth open ; but the
ordinary mode of feeding of this ferocious creature is through its
blood-pump. Snails, worms, insects, tadpoles, and fishes, are
victims in turn.

The larva of Hydrophilus piceus, another water beetle, has an
extraordinary provision for keeping itself from undue pressure in
its pupa stage, which it passes in damp earth (Fig. 3). On each
side of the head (on the forepart of the pro-thorax) it has three
strong brown hooks, and two similar hooks are found at the hinder
end of the body. These hooks, being solid, could contain no
part of the future insect , and the problem was " of what use
could these hooks be to a pupa buried in the earth, and left
behind when the beetle emerges ? " But investigation showed
these organs to be essential to the proper development of the
insect. The skin of the pupa is very delicate. Buried in damp
earth it could hardly escape injury, and the weight pressing on
the pupa might distort its frame ; but the pupa protects itself from
these dangers by assuming an unusual attitude. It extends itself
back downwards in a horizontal position, and supports thet&eight of
its body by the three sets of hooks, as up07i a tripod. In this attitude,
though surrounded on all sides by moist earth, it keeps its body
from actual contact with any object until it has assumed its final
shape. The pupa of Hydrobius supports itself upon the floor of

LEAVES FROM MY NOTE-BOOK.

135

its cell in a similar way, though here the spines cover the whole
of the back.

With the exception of the stag beetle, Hydrophilus is the
largest British beetle ; it is not uncommon in stagnant water near
London, and in the southern counties. Both in Dytiscus and
Hydrophilus a large part of the surface of the body is adapted to
receive and retain a pellicle or flattish bubble of air. Close-set

Fig. 3. — Pupa of Hydrophilus piceus, x 2.

hairs are the means employed to prevent the wetting of these
particular tracts. [Wrap a strip of velvet round a stick and dip it
into water, or sprinkle a few drops of water on a scrap of velvet.
You will see with what difficulty the water penetrates the narrow
spaces between the threads which form the pile of the velvet.
Close, upstanding hairs play the same part in many aquatic
insects.] The spiracles open into the spaces which the protecting

136

LEAVES FROM MY NOTE-BOOK.

hairs keep free from water ; these spaces are filled with atmos-
pheric air, which the beetle drinks in energetically, remaining for
that purpose at the surface of the water.

The female of Hydrophilus constructs a neat cocoon, shaped
somewhat like a coracle, containing about a hundred eggs,
and to her cocoon she adds a mast, which appears to serve the
purpose of steadying the small structure. If the mast be cut off,
the cocoon sinks ; if it be partially submerged, the cocoon turns
bottom upwards. The cocoon is always moored to some floating
weed, and the naturalist, Miger, had the good fortune to watch
the whole process of the construction of one (Fig. 4). The larva
of the small yellow fly, Dixa^ employs the surface film to buoy up
its head and tail ; its body being bent into a V* the apex of which

Fig. 4. — Cocoon of Hydrophilus.
A shows the mast. B is opened to expose the eggs. From Miger.

travels foremost, each half of the V alternately shoving the body
forwards. At the tail end is a respiratory cup, furnished with
valves, flaps, and outstanding processes, all fringed with long hairs,
which serve to exclude the water from a shallow, sunk space, upon
which the longitudinal tracheal trunks open. If the larva should
slip into deep water, the respiratory cup remains free from water,
and buoys up the tail. If the whole body is sunk below the sur-
face, a bubble of air is carried down enclosed in the fringes of
the respiratory cup. The larva, when thus submerged, swims
energetically, and can readily regain the surface of the water.

The larva of the aquatic fly, Dicranota, has elaborate con-
trivances for hunting its favourite prey, Tiibifex^ a small red worm,
to be found at the bottom of muddy pools and slow streams.

LEAVES FROM MY NOTE-BOOK. 137

Tubifex buries its head in the mud, leaving its tail-end waving to
and fro in the water, and draws itself in or out of its burrow by
means of four rows of hooks projecting from its body. In order
that the Dicranota larva may successfully follow the worms into
the depths of their burrows, it is necessary that they should be
able to travel at tolerable speed through mud and gravel. Five
segments near the hinder end of the body are provided with
paired feet, each furnished at the top with three circlets of hooks.
Almost the whole surface of the body is covered by a dense
growth of minute pointed hairs, directed backwards. But the
strangest provision of all is that for the safety of the head,
which can be completely retracted into the body ! The mouth
parts of the head bear a pair of mandibles with long curved
teeth, and the top of the head is defended with a strong shield.
Towards the tail are three pairs of tapering prominences, the
hindmost pair being very long and forming the extremity of the
body. These appendages are supplied with relatively large air-
tubes ; moreover, Dicra?iota has also a pair of spiracles, each con-
nected with a large tracheal tube, which runs along the body to
the head, giving off many branches to the various organs. The
larva seems absolutely indifferent as to whether it breathes atmo-
spheric or dissolved air ; but after its tail has been exposed to the
air, a bubble can often be seen attached to each spiracle.

The " leaf-eating Beetles " ( Chrysomelidce) include a number of
species, which pass their early stages upon submerged plants and
feed upon the roots. The White Water-lily {Nymphcea), Pota-
mogeton, the i\rrowhead, the Sedges, the Marsh Marigold, the
Bulrush, the Horsetail, and other moisture-loving plants, yield
shelter to the various species of Donacia and its close ally,
Hcemo?iia. The female of D. crassipes (often found abundantly
on Nymph(2a or Sparga?iium) bites small round or oval holes in
the leaves, and through these apparently passes the eggs to the
under side, where she arranges them round each hole. The larvae,
when hatched, descend to the bottom, and begin to feed on the
roots. They exhibit no obvious adaptation to an aquatic life, no
swimming organs, no gills, no peculiar shape, but only the dirty
white colour, the small hard head, and the three pairs of pointed
legs, found in an ordinary larva which buries itself in earth. Yet

138 LEAVES FROM MY NOTE-BOOK.

close observation shows a contrivance of an astonishing nature for
obtaining air for respiration. Under a magnifying glass, two
slender curved spines may be seen projecting from the hinder end
of the dorsal surface, and to the bases of these pass the longitu-
dinal air-tubes, which traverse the whole length of the body. At
the roots of the spines are a pair of small openings which look
likejspiracles. Roots of Nymphcea examined by Schmidt-Schwedt
were observed to exhibit peculiar scars ; these were discovered
with difficulty, owing to the dark colour and uneven surface of the
roots. There was in each case a rough hole, made apparently by
the jaws of the larva when feeding, and at a distance corresponding
with the le?igth of the body, a pair of small slits. These slits were
found to penetrate the epidermis of the roots, and to lead to the
small irregular air-spaces, which occupy a considerable part of the
interior of the roots. Schmidt-Schwedt believes that these slits
are made by the spines, and that the air is drawn in by internal
channels running along them. Perhaps no contrivance of aquatic
insects for procuring air is so remarkable as this tapping of the
reservoirs of air of submerged roots.

In the pupal stage a fresh arrangement for respiration has to
be made. The pupal cocoon is a close-woven, oval capsule
attached to the same roots as those on which the larvae feed. On
the attached side the wall of the cocoon is deficient, and a good-
sized hole, previously closed by the root itself, appears when the
cocoon is torn away. A number of small holes, penetrating into
the substance of the root, appear upon the plant when the cocoon
is detached, and it is probably from this source that the pupa
derives its supply of air. Wounds in the living tissue are as a
rule quickly repaired by a corky growth, but this is not the case
with the hole bored by Donacia larvae in the roots of the water-
lily. They remain open so long as the cocoon remains attached,
and only become closed by cork, when the cocoon is torn open
by the emerging beetle, which has remained all the winter in its
pupal cocoon.

The surface film plays an important part in the peculiar feed-
ing and breathing arrangements of the larva of the gnat {Culex).
This larva, when at rest, floats on the surface of the water; but
whilst feeding — as it does voraciously — it hangs head downwards,

liEAVES FROM MY NOTE-BOOK. 139

sweeping minute organisms into its mouth with its vibratile cilia,
whilst at the same time it breathes uninterruptedly through the
respiratory siphon attached to the eighth segment of its abdomen.
If startled, the larva sinks slowly to the bottom by gravity alone,
which shows that the body is denser than water. How then is it
possible for a larva heavier than water to remain floating at the
surface without effort ? The possibility of such a thing turns upon
the existence of the surface film, formed by the same contractile
force which rounds the rain-drop and the air-bubble. The tip of
the gnat larva's respiratory siphon is provided with five flaps, which
can be opened or closed by attached muscles. When open
they form a minute basin, which, though its walls are cleft,
does not allow the surface film to enter. At the time when the
larva puts itself in position to begin its feeding operations, the
pointed tips of the flaps meet the surface film and adhere to it.
The attached muscles separate the flaps, and in a moment the
basin is expanded and filled with air. The surface film is now
pulling at the edges of the basin, and this pull is more than
sufficient to counteract the greater density of the body of the
larva, which accordingly hangs from the surface without effort.
When the larva is alarmed, and wishes to descend, the valves
close, their tips are brought to a point, and the resisting pull of
the surface film is reduced to an unimportant amount. In its
pupal stage the gnat breathes through two respiratory trumpets
placed near the head, in such a position that, when the pupa is at
rest, the margins of the trumpets come flush with the level of the
water. The tail end is now modified as a swimming fan.

The gnat at all stages requires plenty of air, and its egg-raft,
containing from two hundred and fifty to three hundred eggs, is
as ingeniously contrived for aeration, as are the contrivances at all
other stages of the insect's life. If we take two or three of these
tiny egg-rafts, and place them in a jug of water, we may pour the
water into a basin again and again; the rafts float instantly to the
surface, and the moment they come to the top they are seen to be
as dry as at first. The fact is that the surface film cannot penetrate
the fine spaces between the pointed ends of the eggs. The cavity
of the egg-raft is thus over-spread by an air-bubble when accident-
ally submerged. The eggs are kept from contact with water ; the

140

LEAVES FROM MY NOTE-BOOK,

proper upper surface is so buoyant that the raft has great power
of self-righting ; while the instant that it comes to the top, the
excess of water drains off, leaving the eggs perfectly dry on their
upper surface.

The larvae of the minute gauzy-winged fly, Simulium, show a
wonderful adaptation to their environment. These tiny worm-like
creatures, not more than five-eighths of an inch in length, are
perfectly at home in rushing streams and "especially in the rapids
above waterfalls." Their food is altogether microscopic ; their
stomachs are found filled with the flinty valves of Desmids
and Diatoms, with here and there bits of a small crustacean.
Their mouth parts are provided with fan-Hke appendages, each

Fig. 5. — Head of larva of Simulium^ dorsal view, showing eye-spots,
antennae, and fringed appendages.

bearing about fifty long filaments (Fig. 5), which are feathered
along one side, and sweep the food into the gullet. Great pains
are taken to keep these delicate appendages — so necessary to the
Hfe of the larvae — from getting clogged, and, by the help of a
lens, the larvae can often be seen combing them out with their
mandibles.

The life of a submerged insect in a rapid current has, of course,
its own special difficulties, met with, as usual, by special adapta-
tions. The Simulium larva has to creep from leaf to leaf to change
its position as the stream rises and falls, and to avoid enemies.
Of these enemies, Caddis worms are the commonest and most

LEAVES FROM MY NOTE-BOOK. 141

formidable. In moving about there is always the danger of being
accidentally dislodged ; and if a larva should let go or miss its
hold in a rapid stream, what is likely to happen ? It seems inevit-
able that it would be swept away, and who knows where it would
come to rest ? Yet, as it will shortly be seen, the SiniuliutJi is
quite safe.

"The little rivulet," says Mr. Miall, "which I am accustomed
to visit for the purpose of observing this larva is a bright, clear
stream, flowing over watercress and brook-lime, and forget-me-not.
A few feet lower down it ends in the wide and stony Wharfe, a
stream of quite different character, in which I have never been able
to discover a single specimen of this species. Other brooks in
which the larvae are plentiful empty themselves into rivers unsuited
to an insect of habits so peculiar — muddy, sluggish, or brackish.
But this difficulty has been provided against, and I find that the
larva is seldom or never swept away, even when its haunts are
invaded by a groping naturalist. ... If seriously alarmed,
the larva lets go, and immediately disappears from sight. But by
watching the place attentively we should, before long, see the larva
making its way back, and in a minute or two it will be found
attached to the same leaf from which it started, or to some other
leaf equally convenient.

" On close observation a thread, or perhaps a number of
threads, become visible in the white ground. (Mr. Miall, for pur-
poses of observation, had pushed a white plate in amongst the
leaves, when the dark-coloured larva became perfectly evident.)
These threads are, in general, stuck all over with small vegetable
particles, Hke fine dust. The threads extend in all directions from
leaf to leaf, and the larva has access to a perfect labyrinth, along
which it can travel to a fresh place by help of the current, and
with the speed of lightning. I suppose that it grasps the threads
with its pro-thoracic claws, for when it comes to rest it is always
found holding on by them. . . . Although the larva commonly
slides along a thread previously made, and easily seen to be an
old one by the small particles that cling to it, it can, upon a sudden
emergency, spin a new thread, like a Spider or a Geometer larva.
The new threads are perfectly clear and clean ; they are therefore
invisible on a white ground so long as the larva is submergedy^ ^^IC/^ /

142

LEAVES FROM MY NOTE-BOOK.

But by suddenly lifting out of the water a leaf with many larvae
upon it, one may get proof of the spinning of fresh threads. One
or two are pretty sure to let go and drop a foot or more in the air,
and the thread can be seen to glisten in the sun, and to lengthen
itself at the pleasure of the insect. The Simulium larva, gifted
with this power of instantaneously manufacturing a rope, can
hardly be taken at a disadvantage."

The salivary glands which secrete the silk are unusually large
in this larva ; they extend the whole length of the body, and then
bend forwards for a third of its length. But the next question is
as to how the safety of the pupa of Simulium is provided for ; it
seems that such an inactive, defenceless body must immediately
be carried away to destruction by a rushing stream. The pupa is
however as safe as the larva, being protected in a kind of nest,
glued, somewhat like the nests of some swallows, to the stem of a

Fig. 6. — A^ Four pupte of Shnulium in their cocoons attached to aquatic
stem. B, Pupa of Simulium^ removed from its cocoon.

water weed (Fig. 6). When the little nest is first formed it is
completely closed ; but when the insect has cast its larval skin, it
knocks off one end of the cocoon, and thrusts the fore-part of its
body into the current of water, whilst the hinder part is firmly

LEAVES FROM MY NOTE-BOOK. 143

hooked to the silken threads with which the cocoon is lined.
After the pupal stage comes the question as to how a minute
gauzy fly can escape from the rushing water into the air. Through
its elaborate respiratory appendages, the pupa draws in sufficient
air to inflate its pupal skin ; this at the proper time splits along
the back, and a small bubble of air emerges, rises quickly to the
surface of the water, and then bursts. When the bubble bursts,
out comes the fly. It spreads its hairy legs and runs upon the
surface of the water to find some solid support on which it can
climb ; and, as soon as its wings are dry, it flies to the trees or
bushes overhanging the stream.

The ascent of the Simulium fly through rushing waters is
rendered safe by the hairy covering of the body ; the surface-film
clings to the fine hairs, and keeps the air imprisoned and the fly's
body dry. In the same way a covering of velvety hairs prevents
the Diving Spider, as well as many diving insects, from wetting
that part of their bodies which bears the spiracles.

Few objects in natural history are more enticing to the imagi-
nation than the Dragon fly ; its etherial beauty, its gauzy wings,
and jewelled body, make it seem hardly a thing of earth. Yet,
alas ! further knowledge shows this spirit-like creature to be a
merciless carnivore, its mouth filled with the little insects it stores
up for eating at leisure. The ugly, sluggish larva of the Dragon
fly is armed with one of the most murderous weapons it is possible
to conceive. " The policy of the slow Dragon-fly larva is to lie
still, in the shady recesses of water-weeds, till its victim comes
within easy reach ; then, quick as lightning, it stretches out an
arm-like extension of the head, and seizes its prey. The weapon
so employed is a peculiar modification of a pair of limbs attached
to the head, and called the second pair of maxillae. In insects
these appendages form the third pair of jaws, and are formed
more or less completely into a labium or under-lip. The labium
of the Dragon-fly is carried on a jointed arm, usually much
expanded at the end. Side-pieces corresponding to the labial
palpi are attached, and there is commonly a pair of spines or
claws, which secure the struggling victim. When the larva is at
rest the apparatus is folded up, the broad joint being spread over
the front of the mouth, while the arm is bent backwards between

144 LEAVES FROM MY NOTE-BOOK.

the fore-legs. In Libellulid larvae, the side-pieces can be brought
together in the middle line, like the jaws of a rat trap, which
they further resemble in their toothed edges.

A number of aquatic insects, like the terrestrial Ichneumons,
lay their eggs in the bodies of living insects. The larvae hatch out
and devour the bodies of their hosts little by little, delaying fatal
injury till the parasite is full grown. " One such form, Agriotypus^
preys upon caddis worms. . . The history of this parasite has
recently been more fully explored by Klapalek.'^ In Bohemia,
Klapalek finds that Agriotypus commonly attacks the case of a
Caddis worm, known by the name of Silo pallipes. On warm
days in April the Agriotypi may be seen swarming like ants about
the banks of the brooks, and also flying above the water. The
females descend stems and grasses into the water, and creep under
stones in the bed of the stream in search of victims. The larva
of the parasite spends its whole life under water and inside the
case of a Caddis worm. Its host is not mortally injured till it
has prepared for pupation. Like a healthy Caddis worm, it makes
its case fast and closes it up. Then the Agriotypus larva makes a
final end of its victim, devouring it, and cramming the remains
into the hinder part of its case. It then proceeds to move the
case by a long band formed from its own salivary glands, which is
the external indication of an agriotypised Caddis." Within this
extemporised cemetery it spins its cocoon, and winters before
emerging as a winged fly (Fig. 7). A ghastly history, closely
parallelled by that of the Sphex wasp.

The larva of the Alder fly, Sialis, is guided by one of those
extraordinary instincts which suggest that the animal is directed by
some intelligent power, to which one can ascribe wisdom, but not
beneficence. The larva of Sialis, hatched under water, and living
in water all through its early life, comes upon land in May or June
to pass through its pupal stage. For this purpose it will travel far
from its native pool. Mr. Miall says, " I have lately found one
creeping on the surface of the ground six yards from the water,
though the season was dry, and the soil common garden mould.
This larva had climbed up a concrete wall, made its way through
a thicket of cotoneaster, and reached an open flower-bed. When

* Ent. Monthly Mag., 1889, p. 339.

LEAVES FROM MY NOTE-BOOK.

145

the insect has found a place to its mind, it enters the earth, exca-
vates a Httle cell, casts the larval skin, and is transformed into a
pupa, which has the legs and wings free from the body, though

Fig. 7. — Agriotypus armatus.
A, Imago ; B, Pupa ; D, Larva ; E, Agriotypised case of ditto ; G, Section
of ditto, showing— z;', Fore operculum ; wi. Hind ditto of case ; s. Remains
of Silo larva ; a.g.. Pupa of Agriotypus ; e., Remains of cast larva skin of
ditto. From Klapalek.

enclosed in special sheaths. In about three weeks, a heavy awk-
ward fly emerges, with black body and large coarse wings. The
female lays patches of dark brown eggs on leaves, stones, or

146 LEAVES FROM MY NOTE-BOOK.

palings, not far from water. When the larv^ hatch out, they
travel to the water, and Mr. Miall says he has often seen the fresh
hatched larvae wriggling out on leaves many yards from the nearest
stream or pond. " How they find the way," he adds, " I do not
know," and that indeed is just the puzzle !

It would be impossible to condense, with any justice, the
extraordinarily interesting accounts of the life-histories of Ephe-
meridce, taken from the works of Swammerdam, Reaumur, De Geer,
Sir John Lubbock, and other naturalists ; but a few points of
interest may be alluded to. The Ephemeridce have, in their life-
history, characteristics equally interesting and puzzling. Their
lives as larvae are comparatively long, and, in their aquatic stage,
the creatures are provided with most beautiful and complicated
feathery or leaf-like gills ; they have no conspicuous pupal stage,'''
but undergo numerous moults, amounting in Chlocon to as many
as twenty-one ; they burst suddenly into aerial life, their wings
expanding with such suddenness as to baffle the sight ; the flat
smooth eyes of the larval stage are succeeded by many-faceted,
compound eyes, and two long tail filaments enable them to rise
for their giddy flight over the water. All these complicated,
exquisite arrangements lead up to a life of but a few hours —
sometimes of only half-an-hour's duration ; some species emerge
at sunset, others after sundown ; but all alike are destined to a
rapid death, as in their perfect state they can take no food.

Reaumur fully describes his researches as to the emergence of
Poly??iitarcys, the species of Ephemeron most common in the neigh-
bourhood of Paris. He says : " In 1738, I resolved to attend to
the emergence of this fly, and engaged an angler of Charenton to
tell me when the first signs appeared, which were expected between
St. Laurence's Day and Notre Dame d'Aout, that is between the
loth and 15th of August. This year the flies appeared on the
1 8th. On the 19th I received warning from my angler, and the
same day, three hours before sunset, I took his boat to examine
the banks of the Marne and Seine. Where the shore was level
and sheltered from the wind, heaps of dead Ephemerce could be
seen. During this excursion by water I removed some clods of

* See note, Natural History of Aquatic Insects, p. 305.

LEAVES FROM MY NOTE-BOOK. 147

earth which were riddled with holes, and placed them in a large
bucket of water. . . . The sides of the clods exhibited larvae
partly or completely exposed. At length the sun set. At that
time Ephemera were to be seen flying here and there over the
Seine. ... I crossed over to the Marne, where there seemed
still fewer. At about eight o'clock, the coming on of evening and
the flashes of an approaching thunderstorm caused me to return
into an arm of the Marne which washes my own garden. . . .
Soon the man cried out that a prodigious number of Ephemerce
were coming. I seized one of the lanterns with which they had
come to meet me, and ran to see what was going on. ... I
saw a sight beyond all expectation. The Ephemerce filled the air
like the snow-flakes in a dense snow-storm. The steps in my
garden were covered to a depth of two, three, or even four inches.
A tract of water five or six feet across was completely hidden, and
as the floating insects slowly drifted past others took their place.
Several times I was obliged to retreat to the top of the stairs from
the annoyance caused by the Ephemerce, which dashed in my face,
and got into my mouth, eyes, and nose. ... In about half-
an hour, or less, the swarms were less dense, and by ten o'clock
only a few scattered Ephemerce could be seen on the river. Next
day they appeared in undiminished numbers, and in diminishing
quantities for four or five days longer." Reaumur speaks of
changes of weather and of temperature, and says, " It appears
that whatever the weather on the day of emergence — warm or
cold — the Ephemerce quit the water at a fixed hour.

"What becomes of the prodigious swarms of insects when
they no longer fly through the air ? They are for the most part
already dead or dying. The fishes "enjoy a feast, and the French
anglers speak of the Ephetnerce as manna — e.g., they say the manna
has begun to appear ; there was a good fall of manna last night !
Whether devoured by fishes or not, those that fall into the water
soon perish. More lingering, but not less certain, is the fate of
those which descend upon the banks in the neighbouring fields.
Heaped one upon another, and unable to move, they die by
inches." He speaks of the extraordinary rapidity of the act of
emergence. As the wings are not provided with muscles, they
are probably expanded by sudden injection of blood from the

148 LEAVES FROM MY NOTE-BOOK.

heart. If the wings of an emerging larva are cut off and thrown
upon the water, they will still expand ; and the moult will be
completed if the creature is thrown into spirit of wine.

It would be interesting to know the views of a May fly as to
the nature of things. The Ephemeron which had seen the last
departing rays of the sun, would be absolutely sceptical as to such
an unverifiable phenomenon as sunrise ; the Ephemeron emerging
after sunset would certainly not be so unscientific as to believe in
the existence of a sun at all. I imagine that our views as to the
Universe must, to higher intelligence, appear as absurdly limited
as would be the views as to earthly things of a philosophical May
fly. Those scientists who declare that there are no phenomena in
nature, and no natural laws but those which our very limited
senses can comprehend, are, it seems to me, biit as philosophical
EphemercB,

Yet that brief life has in it something which, during its brief
span, pleases us to dwell on. The long dull stage has been passed,
and the insect emerges, with a swiftness that baffles the sight, into
aerial hfe ; then comes the giddy dance over the evening waters
in the most delicious hours of spring and summer ; then marriage
flight, and the quick death ere night has passed. It is the Hellenic
type of existence, all beauty, gaiety, and pleasure, with remorseless
destiny awaiting the happy dancers. Destiny in the shape of swift
skimming swallows and hungry fish.

I have had space in this article for only a tithe of the interest-
ing life-histories to be found in Mr, Miall's fascinating book, and
I envy those who are young and active enough to follow his
example, and spend hours as he has done near some clear rushing
stream, where watercress and forget-me-nots are growing, or by
some quiet pool where little beings lie sucking the air-reservoirs of
water-lily roots.

We are deeply grieved to receive, at the moment of going to
press with this sheet, news of the very sudden death of Mrs.
Alice Bodington, She died on February 15th at New West-
minster, B.C., Canada, of pneumonia, after an illness of scarcely
five days' duration.

[ 149 ]

Staining tbe ZTnbcrcIe Bacillna in Sectioned'

SHERIDAN Delepine {Med. Chron., 1896, v. 17) gives the
following notes from the Pathological Laboratory at Owen's
College : — The tubercle bacillus can easily be stained in
section by the methods recommended originally by Ehrlich and
by Ziehl. Many slight modifications in technical details have been
introduced by a large number of workers, but the essential step by
which the Bacillus tuberculosis can be differentiated from other
bacilli consists in tbe use of mineral acids, such as nitric or sul-
phuric acid. When bacilli have been well stained with methyl-
violet or with fuchsin, it is found that certain dilutions of sulphuric
acid and nitric acid will rapidly remove the stain from all the
known pathogenic bacilli, with the exception of the bacilli of
tuberculosis and" of leprosy, which are discoloured very much
more slowly.

The use of nitric acid is, however, objectionable when one has
to deal with delicate tissues, and even sulphuric acid, diluted with
six parts of water, will cause a certain amount of distortion. For
this reason bacteriologists have long wished to find a method which
would be less brutal than those just alluded to.

Not long before his death. Dr. Kiihne, of Wiesbaden, commu-
nicated to Dr. Borrel, of Montpelier, a method in which the use of
strong acids was done away with. Dr. Borrel, after using this
method in some researches in tuberculous lesion, has strongly
recommended it in the Annales de V Institute Pasteur (Vol. VII.,

P- 593)-

In this method, after the sections have been stained in the
usual way by means of carbolised fuchsin, they are placed for a
short time in a solution of hydrochlorate of aniline, and after this
they are left in alcohol till quite decolourised, when it is found that
though the fuchsin has been removed from all the tissues, the
tubercle bacilli remain deeply stained. This method, therefore,
resembles very closely the Gram's method, with the difference that,
instead of Gram's iodine solution being used to fix the stain in the
bacilli, in this case it is Kiihne's hydrochlorate of aniline which is

used.

*From Pediatrics i July, 1896, p. 38.

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. l

150 STAINING TUBERCLE BACILLUS IN SECTIONS.

Dr. Ratcliffe, being engaged in delicate experiments on the
spread of tuberculosis in the laboratory, was advised to try this
method, which seemed to present many advantages over the older
methods, when a few bacilli only are present in the organ. The
details published not being quite sufficient to obtain very satisfac-
tory results in every case, we worked out the details now given, with
the result that we can strongly recommend the following procedure :

(i) Fix tissues by means of perchloride of mercury, acidulated
or not, and then harden in alcohol as usual.

(2) Embed tissues in paraffin, using toluol as a solvent.

(3) Fix sections on slides by means of glycerine albumen in the
usual way.

So far, there is nothing new in the method.

(4) Stain with haematin solution for ten to twenty seconds to
obtain a pure nuclear stain (not too deep) ; then wash thoroughly
in water.

(5) Stain now with Ziehl's carbonised fuchsin, kept at a tem-
perature of about 47° C. for twenty to thirty minutes. The slides
are during that time to be kept in a moist chamber to prevent the
stain drying on the specimen.

(6) Remove the stain, and treat the section with 2 per cent,
watery solution of hydrochlorate of aniline for a few seconds.

(7) Decolourise in 75 per cent, alcohol till the section is appa-
rently free from stain ; this will take from fifteen to thirty minutes.

(8) Double stain with a solution of orange (i per cent, of
saturated watery solution of orange to 20 to 40 parts of 50 per
cent, alcohol).

(9) Dehydrate with absolute alcohol.

(10) Clear very rapidly with xylol.

(it) Mount in xylol and Canada balsam.

Penicillium Cupricum. — Mr. J. de Seynes states that the
fungus called by this name is but a form of P. glaucum^ the
ordinary appearance of which it assumes when transferred to a
different medium.

[ 151 ]

(Abstract from Canadian Newspaper.)

THE citizens of New Westminster, B.C., Canada, were
shocked this morning (February i6th, 1897) to learn
the sad news of the death of Mrs. Bodington, the wife
of Dr. G. F. Bodington, the Medical Superintendent of the
Provincial Asylum for the Insane, which occurred on the 15th
inst. Even the comparatively few who were aware of Mrs. Boding-
ton's illness, from Pneumonia, had no idea of there being any
immediate danger. In fact, her illness was very brief, scarcely five
days, and no dangerous symptoms were developed until Sunday.
All that loving care and medical skill could do was unavailing, and
on Monday death released a noble soul from its bodily sufferings.

Mrs. Bodington, who was a native of Suffolk, England, and
the daughter of the late Francis Capper Brooke, of Ufford, Suffolk,
came to this province with her husband about ten years ago, and,
after a short residence in Vancouver, B.C., they removed to Hatzic,
where the doctor engaged in farming, in connection with a country
practice. About two years ago, on receiving his appointment to
the asylum. Dr. Bodington removed to this city, with his family.

In a comparatively short time, Mrs. Bodington made many
friends in New Westminster, and helped on many a good cause.
Besides being an energetic worker in Church of England circles,
she was instrumental in forming a local branch of the Botanical
Society of Canada, and was a warm friend of the Public Library
and of the Art and Scientific Society, before which she read able
papers on more than one occasion.

For many years Mrs. Bodington had been well known in the
world of letters. Widely read, and a profound thinker, she wielded
a strong pen, which was always ready to defend those principles of
which she was so able an advocate. Among other works, Mrs.
Bodington was the author of Studies in Evolution and Biologv. She
was also a regular contributor to such standard magazines as The
Afiierican Naturalist^ The Popular Science Review ^ and the Inter-
natiofial Journal of Microscopy and Natural Science^ and we believe

152 THE LATE MRS. ALICE BODINGTON,

that the very latest work of her pen appears in the present part of
this Journal. Mrs. Bodington also frequently contributed vigorous
articles on various subjects to the Provincial and local press.

Socially, Mrs. Bodington will be very greatly missed, while as
wife and mother her death is a sad bereavement, and Dr. Boding-
ton and his family have the kindliest sympathy of the community
in their irreparable loss. Of the many children of Dr. and Mrs.
Bodington, but two, Miss Winnie Bodington and a young son, are
at home. Of the others, all grown up, one son is at Plymouth,
another also being in England, one is a barrister in Paris, France,
another physician on one of the Empress liners, and two daughters.
Miss Bodington and Mrs. Hamilton, reside in Winnipeg.

Mrs. Bodington was buried at St. Mary's Church, Sapperton,
on Feb. 17th. A large number of residents attended the funeral,
amongst them being as many of the Asylum attendants as could
be spared from their duties, six of whom acted as pall-bearers.

The floral tributes were numerous and very beautiful, especially
one presented by the attendants of the asylum, by whom Mrs.
Bodington was most highly esteemed.

a IRevicw of tbe (Bolgi flDetbob

By Oliver S. Strong.
Part II.

" Treatment and Preservation of Preparatio?is.

WHETHER the black stain has turned out so that the piece
is worth keeping for further investigation can be ascer-
tained by means of trial sections examined in glycerine,
or in the reaction fluid itself. Then one must provide for the
preservation of the piece and the microscopical sections. Although
it is certain that a longer sojourn in the silver solution does no
harm whatever, and that such a sojourn may serve as a means of
preservation, yet it is expedient, in order to have the pieces ready
for further treatment, to transfer them to pure commercial alcohol.
This not only serves to harden the tissue farther, but also to free
it from the silver nitrate which, as I shall mention below, is very
* From the Journal of Cotnparative Neurology.

A REVIEW OF THE GOLGI METHOD. 153

injurious to the preservation of the microscopical sections. To
accomplish the latter the alcohol should be changed two or three
times till it remains transparent for a number of days after the
piece is brought into it. In this way the pieces can be kept a long
time. I have kept them for about nine years in this way, and can
obtain from them, when I wish, preparations as clear as those
obtained from them shortly after their preparation.

" The further treatment of the microscopical sections corres-
ponds essentially with the usual procedure in obtaining anhydrous
preparations, except for some peculiarities necessary to overcome
some difficulties in the way of securing stable preparations.

" The sections, before they are permanently brought into gum
damar or Canada balsam, must first be treated successively,
accordmg to the classical method, with absolute alcohol and some
clearing fluid. Each of these steps requires an especial care not
necessary with ordinary preparations.

" {a) Treaimefit with absolute alcohol. The only rule to be
especially noticed here is that the sections must be very carefully
dehydrated by bringing them into three or four changes of pure
absolute alcohol. This is the only principal rule in order to obtain
a long preservation, for the more accurately and carefully the
dehydration is carried out, thereby freeing the tissue from the last
trace of silver nitrate, the more one can rely upon the preparations
remaining clear for a long time.

" {b) Cleari?ig. The sections to be mounted must first be
brought, for clearing, from absolute alcohol into creosote, where
they remain some minutes, and then into turpentine. In the latter
they can remain a long while. The selection of these two sub-
stances, and their consecutive use, is another aid to securing a
long preservation. Among many other substances tried for clear-
ing I have also found oleum origani* for my method very useful,
but I have found no sufficient ground for abandoning the first
mentioned fluids. The sections usually remain in turpentine only
lo to 15 minutes, but may remain there longer..

" {c) Completion of the microscopical preparations. For perma-
nent preservation, the sections are brought from turpentine into

* This oil, followed by washing in xylol instead of turpentine, is preferred
by the writer.

154 A REVIEW OF THE GOLGI METHOD.

damar, which, after many comparative tests, I have found better
adapted for this purpose than Canada balsam. I must here call
attention especially to a peculiar treatment of the sections ; con-
trary to the usual custom, I do not cover the preparations with a
cover glass. When the sections are covered in the usual way with
a cover glass, they begin after a time to turn yellow (owing to a
second impregnation which takes place), then the outline of the
stained cell elements become obliterated, the whole tissue becomes
opaque, and, after a period of from two or three months to two
years, the preparations, with few exceptions, become useless. On
the contrary they may keep a long time, thanks to the repeated
washing, of which I have spoken, and especially to the mode of
mounting without a cover slip in a layer of damar. I can now
state that the earUer lamentable disadvantage that preparations
made by my method soon spoiled is now almost completely reme-
died. I have many preparations, made by me nine years ago,
which have not yet lost their original clearness.

" If the good preservation appears menaced by an incipient
yellowing, another longer bath, on the slide, in turpentine will
restore transparency and freshness to the preparation.

"I have found it convenient to employ for this kind of mount-
ing a special wooden slide with a square opening, in which, by
means of a groove, a glass plate (a cover slip of somewhat greater
diameter than usual) is fitted and stuck fast with a solution of
shellac in alcohol. This serves as a slide, and the section adheres
to it by means of the damar.

" This kind of slide not only enables the section to be exam-
ined from both sides, but also has the advantage of preventing
dust from fouUng the object, to which this kind of mount would
be especially exposed. To accomplish this it is only necessary to
turn the side of the slide with the section downwards, as soon as
the damar is hard enough, or to pile the preparations on top of
each other.

" I further remark that it is wise to shield the objects from the
influence of light ; still this precaution is not entirely necessary
if the repeated washing has been carefully performed. After ful-
filling these conditions, I might expose preparations for days to
the sun's rays without injury to them.

A REVIEW OF THE GOLGI METHOD. 155

" This is not the place to lay stress upon the value of the
results which can be attained by means of this method. The
figures accompanying this work demonstrate it sufficiently. They
display the forms to be observed in the preparations with a fine-
ness not only not exaggerated, but inferior to the natural object.
I will here only bring forward the disadvantages of the method,
in order to give the means by which they are to be avoided. The
long time between the placing of the pieces in bichromate, and
the appearance of the reaction (it not infrequently happens that,
in consequence of this, the pieces are forgotten), the uncertainty
about the extremely variable time required to reach the proper
hardening, the different conditions in which individual layers of
the same piece are found, all these are disadvantages whose
removal would be desirable.

" I have sought by expedients to change my method in one
way or another in order to secure greater certainty and accuracy in
the results. Among the means tried by me I present the following
which have yielded me a certain advantage.

" («) Itijections of bichromate (solution to 2)4 percent.)* It
must be abundantly and constantly appfied so that the whole
parenchyma of the part to be investigated is fully and uniformly
penetrated by the hardening fluid. The fixation of the elements
by the reagent, where possible, before the slightest post-mortem
change can take place is of the highest importance in securing a
very delicate reaction. The action of the injection consists prin-
cipally in giving a uniform hardening, furthermore in preventing,
very likely, a slight post-mortem change in the interior of the
piece, and finally in abbreviating the sojourn in bichromate.

" If I may draw a conclusion from some especially successful
reactions accomplished in this way, I must declare that the injec-
tion is in these various respects actually of considerable advantage.
Some other experiments, not yet very extended, have convinced
me that a favourable influence is exerted in the same way by
injecting, not a simple solution of bichromate, but one with gela-
tine added (2^ percent, bichromate, 100 c.c. ; dry gelatine,
which is dissolved in the usual way, 5 to 6 grams). This proce-

* A stronger solution would probably be better, inasmuch as it undergoes
dilution in the tissue. — Author.

156 A REVIEW OF THE GOLGI METHOD.

dure appears to me especially fitted to give the pieces in less time
that particular hardening most favourable to the best reaction with
silver nitrate. I mention, for example, a case where I have
obtained graduated reactions of surprising fineness on pieces fifteen
to thirty days after they were placed in bichromate at a tempera-
ture of 15^ to 20^ C. (in autumn), the pieces having been subjected
to the above treatment.

" The injection is performed in the usual way (with a simple
syringe or with a siphon in which the pressure is regulated by the
height of the vessel containing the injection fluid) either through
the carotid, when one wishes to limit the hardening to the cere-
brum and cerebellum, or through the aorta when the fluid should
also extend to the spinal cord.

" It is superfluous to state that when the bichromate and gela-
tine is injected it must be warmed so that it will remain fluid. In
this case it is especially important to perform the operation imme-
diately after the death of the animal, before the tissues are cold.
Only in this way does one secure the finest and most widespread
injection.

"After the injection the nervous parts are removed from their
cavities, cut into pieces, and brought as usual into bichromate,
where they are carefully treated as dealt with above.

" (b) Hardening in bichromate at a constafit temperature. The
circumstance, pointed out several times, that the uncertainty about
the time at which the pieces must be brought from the bichromate
into the silver solution depends for the greater part upon the tem-
perature of the medium, leads to the idea that the best means of
avoiding this inconvenience would be the employment of a con-
stant temperature for the bichromate in which the pieces lie. For
this purpose the warm chambers used in investigations upon
micro-organisms seem best adapted.

" I have used the chamber of Wiesnegg, in which I maintained
a temperature of 20^ to 25°. This had good success, but only in
the direction of considerably abbreviating the period of hardening
in bichromate, so that the reaction could be obtained much sooner
than formerly and in a tolerably constant period of time. Thus,
the reaction in a warm chamber appeared after eight to ten days
and proceeded to completion up to fifteen to twenty days. This

A REVIEW OF THE GOLGI METHOD. 157

is, perhaps, an advantage in so far as one can with sureness obtain
certain preparations for demonstrations in a tolerably brief time.
But the advantage is not extended to the fineness of the result,
since in all such preparations the reaction turns out rather coarse.
I was not thereby encouraged to extend experiments in this direc-
tion, especially as the abbreviation of the time can be attained in
other simpler ways, and as the pieces in the chamber quickly pass
by the period favourable to the success of the reaction without
attaining the kind of hardening sought — which is a not insignifi-
cant disadvantage.

" {c) Hardening in ErlickVs fluid (bichromate of potassium,
2^^ g. ; copper sulphate, >^ g.; distilled water, loog.)- Regarding
this I confine myself to stating that the copper salt added to the
bichromate did not prevent the reaction, and that the Erlicki's
fluid possessed the same advantages and disadvantages as the
preceding method (warm chamber). It accelerates the hardening
so that in a few days (6 to 8 to lo) the black stain of various
elements of the nervous system can be obtained by transferring to
silver, but the result cannot be commended for fineness. More-
over the period advantageous for the reaction is very quickly
passed over.

" As it appeared to me that the limited and not very fine form
of the reaction might be due in part to the rapid action of the
hardening fluid, I weakened the same by mixing it in gradually
increasing quantities with Miiller's fluid (Erlicki 20 to 50 per cent ,
Miiller 30 to 50 per cent.). The results obtained by means of
this variation were decidedly good. After only 5 to 6 to 8 days'
immersion in such a fluid I obtained preparations which, in regard
to fineness of result, had a certain worth. It thus appears to me
that this variation can be recommended for the purpose of quick
demonstrations of cell-forms. For the finest details, especially
the relation of the functional processes of the ganglion cells and
the nerve fibres, I find that the first procedure is always to be
preferred, or also the following :

" 2. — Method of the successive actions of a mixture of osmic acid
with bichromate and of the silver nitrate. This procedure also is
only a modification of the original, but deserves a place in the
exposition as a method by itself, partly because the not unimportant

158 A REVIEW OF THE GOLGI METHOD.

changes of the results which it yields and the treatment which it
requires are to be ascribed to the newly-added reagent, partly
because the process so modified can remedy some inconveniences
of the original method.

" It can be applied in two ways, namely : —

" (a) By laying small pieces of nervous tissue directly in a
mixture of bichromate and osmic acid (2 per cent, to 2J per cent,
solution of bichromate, 8 parts ; i per cent, solution of osmic
acid, 2 parts).

" The black stain is obtained the most quickly with this pro-
cedure. The black staining of a great number of nervous elements
can be obtained by transferring into silver at the second or third
day (see the directions for procedure in the description of the
original method). The reaction extends itself on the immediately
following days, then, as usual, diminishes, and at the tenth or
twelfth day entirely ceases.

" The treatment of the macro- and micro-scopical preparations
which are obtained in this way must be considerably modified.
Pieces prepared by this method differ from those prepared by the
first method inasmuch as when they are kept a long time, for
future use, they become diffusely blackened, and thereby useless.
They must be kept in the same silver solution which has served for
the reaction. Then they are brought into pure alcohol, which must
be changed, where they remain not longer than two days, sectioned
and subjected to the above described treatment (absolute alcohol
with repeated washing, creosote^ turpentine, damar) necessary for
their permanent preservation as microscopical preparations.

" Although this application of the osmium-bichromate solution
is certain, and, as far as fineness is concerned, yields satisfactory
results, yet I find that, for a systematic study of any definite portion
of the nervous system, the following method is far preferable :

" (^) Bringing of fresh pieces into the bichromate solution ; first
transference into an osmium-bichromate solution ; second transference
into the silver solution. It is different with this second procedure
than with the preceding, in which the series of pieces of tissue to
be examined are useless after a few days. Here the fresh pieces
(with or without injection) are laid in the bichromate solution, and
remain, so to speak, in the hand of the investigator. They can

A REVIEW OF THE GOLGI METHOD. 159

either immediately or later be tried, /.t?., during a period of from
3 or 4 to 25 or 30 days after the immersion. If one during this
whole period transfers, at intervals of 2 to 3 or 4 days, some pieces
into the osmium-bichromate solution, he thus possesses many
secondary series of pieces which are brought singly (one or two at
a time) into the nitrate solution. These, from the third or fourth
to the eighth or tenth day of their sojourn in the mixture, yield
with certainty, when brought into the silver, preparations with all
the consecutive gradations and combinations described in the
original method, and also possessing surprising fineness.

'■''After-treatment. Preservation of the pieces in the silver
solution ; pure alcohol for 2 or 3 days, till one has time to under-
take the examination ; repeated washing out of the sections with
absolute alcohol ; creosote, turpentine, damar, mounting without
cover glass.

" This is the method which I at present prefer for the demon-
stration of the finest details in the structure of the central nervous
system. The particular grounds for this preference are the follow-
ing : (i) Certainty of obtaining the reaction in many gradations,
if one makes use of a certain number of pieces. (2) The con-
siderable length of time during which one can obtain the reaction
— while one can also attain it in a few days. This renders an
accurate investigation much easier. (3) The pieces are much
more conveniently treated. (4) Finally, one obtains at the same
time with the gentle gradation of the results also a greater fineness
of the same, especially regarding the behaviour of the functional
processes of the ganglion cells.

"3. — Method of the consecutive actions of the bichromate of
potassium a?id of bichloride of mercury. This can likewise yield
valuable results whose value is not diminished because they, in
many respects, conform to those obtained by the silver nitrate.
Indeed, the particular purposes it can fulfil, and its peculiar
advantages, are in and for themselves so important that it must be
given a place of its own alongside the silver nitrate method. The
clearness with which the various elements of the nervous system
emerge in this reaction is not less than that brought about by the
silver nitrate. The elements appear, when viewed under the
microscope by transmitted light, completely black after the action

160 A REVIEW OF THE GOLGI METHOD.

of the sublimate, and for microscopical investigation the action is
the same as when there is an actual black stain. But this stain is
only an appearance due to the opacity of the elements upon which,
probably owing to a reducing action, the mercury has precipitated.
In reflected light one notices that the elements appear entirely
white; indeed, under stronger magnification they show plainly a
metallic lustre.

" 1 will remark that the particular advantages of this method
consist first in the fact that the reaction can take place in large
pieces, further that its success is absolutely certain without being
necessarily bound by strict rules as to the time of sojourn in the
hardening fluid, and finally in the fact that the preparations which
it yields requires no especial precautions for their preparation, but
can be treated in the usual way, like sections stained with carmine.

" The mode of application of the sublimate method is only
distinguished from the silver method by some unessential things.
It likewise consists of two essential processes :

" {a) Hardening of the pieces in bichromate.

" {b) Transference of the same into a solution of bichloride
of mercury and sojourn in the latter.

" {a) The hardening in bichromate is done entirely in the usual
way. (See the original method.) I only add that the reaction
does not proceed in an essentially different manner if consecutively
stronger solutions of i, 2, 3 per cent, are employed, or if the
pieces are immediately laid in Miiller's fluid. In general it is
expedient for the pieces to be small, but this is not absolutely
necessary. Good results are also obtained with large pieces,
indeed with whole brains. In the latter case the preserving fluids
require a long time to penetrate by osmosis from the periphery into
the interior, and the central portions could spoil before they expe-
rienced the action of the fluid. It is necessary therefore to make
a careful preliminary injection of bichromate solution, so that the
reagent is well distributed throughout the organ.

" A few days' (6 to 8 or less) sojourn in the bichromate solution
is sufficient to obtain, by putting the pieces into sublimate solution,
an extended fine black stain of a greater or less number of cells
(indeed one can obtain an indication of the reaction on the fresh
brain which is placed immediately in the sublimate solution). A

A REVIEW OF THE GOLGI METHOD. 161

more suitable period to obtain fine and extended results is from
20 to 30 days. A much longer hardening (from 2, 3, 4 months,
or more) is by no means unfavourable for the reaction. I remem-
ber, among other cases, to have obtained reactions of wonderful
fineness in some whole brains which were in bichromate solution
nearly a whole year.

" It will be perceived that this indefiniteness of the time con-
stitutes a very advantageous circumstance, since thereby pieces
can be employed which would otherwise be useless.

"(z^) Transference of the pieces into the sublimate solution.
The solution used by me contains ^ per cent, of bichloride of
mercury. [ have satisfied myself that the method is equally suc-
cessful when the solution is weaker (}( per cent.), or stronger
(i per cent.). The pieces are brought immediately from the
bichromate into this solution.

" The reaction throughout the thickness of the piece results
much more slowly than with the silver nitrate. If the pieces are
suitably hardened, 24 to 48 hours suffices with the latter. With
the sublimite. on the other hand, not less than 8 to 10 days are
necessary, in order that the reagent may penetrate throughout the
piece when the pieces are small, and much more (2 months and
upwards) when the pieces are large (whole brains). The period
of action of the bichromate must also be considered ; the longer
this has been, the longer must be the sojourn in the sublimate, but
the more complete and delicate is the reaction,

" During the sojourn of the pieces in the subUmate solution,
the bichromate with which the tissue is saturated diffuses out and
impairs the purity of the fluid, which assumes a yellow colour,
while the pieces become paler. For this reason the sublimate
solution must be changed daily, especially at the beginning of the
immersion. Later, the changes are made only when the solution
becomes yellow.

" It may be assumed that the reaction begins when the pieces
are entirely decolourised, i.e., when the tissue is completely freed
from bichromate. If, beginning about this time, sections are made
and examined under the microscope daily, it will be noticed that
the first traces of the reaction begins 3 or 4 days after the immer-
sion, and that they can be known by a number of small black

162 A REVIEW OF THE GOLGI METHOD.

spots scattered here and there. After 4 or 5 days more one sees
the cell-forms gradually become more complete and numerous,
and the reaction thenceforward continues to extend and complete
itself. It even appears that further advantages are gained when
the sojourn in the sublimate solution is extended indefinitely, the
sublimate being changed as often as it becomes yellow through
the presence of bichromate. With brains which have been long
exposed to the action of the bichromate, — and such often yield
the most beautiful results, — the sublimate solution must be changed
during several months before this yellowing ceases.

" The above constitutes a further difference from the manner
of action of the silver nitrate, inasmuch as in the latter the whole
action is completed in 24 to 48 hours, after which no further action
is exerted, although the pieces can be kept in it longer.

" When the reaction has reached its maximum, the pieces
remain colourless, and have the appearance of fresh brain tissue
which has been slightly washed in water.

" The pieces may remain in the sublimate solution as long as
one pleases, not only on account of the possibility of a further
extension of the reaction, but also because they thereby receive a
hardening better adapted for making fine sections.

" As to the manner in which the reaction extends to the differ-
ent elements, I will merely remark that the reaction affects the
ganglion cells in pieces which have reached that degree of harden-
ing attained in the first month's immersion in bichromate, and the
reduction only extends itself gradually to the nerve fibres also.
The reaction displays itself to the fullest extent in the nerve fibres
almost exclusively in pieces which have lain a long time in bichro-
mate, and are very strongly hardened. I recall in this connection
the brains which have been kept very nearly a year in bichromate ;
they showed an almost universal very fine stain of the bundles of
nerve fibres, and of their finest subdivision.

" Treatment and preservation of microscopical preparations.
The only special precaution required by preparations made by
means of the sublimate reaction before they are mounted in
glycerine or balsam is a careful washing in water. Without this
precaution a precipitate in the form of a black powder or needle-
shaped crystals is formed in the sections some days after mountmg,

A REVIEW OF THE GOLGI METHOD. 163

and if it does not entirely spoil, yet seriously mars them. As to
the rest, the usual mode of preparation is employed : mounting in
glycerine, damar, or Canada balsam, after the necessary dehydra-
tion in absolute alcohol, and clearing in creosote or clove oil. No
further precaution is necessary.

"When I described this method the first time*' I expressed the
conviction that it could be still further perfected so as to yield
finer results than those hitherto attained by me. Practice has
later led me to some modifications which have improved it. But
it has experienced another important development owing to the
persevering experiments of Dr. Mondino, who succeeded in apply-
ing the process with remarkable success to nothing less than a
whole human brain. I will here add the words themselves in
which this observer summarises the advantages which one can
gain from the use of the bichloride of mercury for the study of
the central nervous system.

" The following is Dr. Mondino's Summary t :

" ' A. The sublimate method is the first by means of which
we can obtain the black stain of the nerve cells and their func-
tional processes in the entire brain, and enables us to follow these
latter directly in their course through the brain.

" ' There is no doubt but that this technique fulfils the require-
ments of scientific accuracy better, and puts us in a better position
to obtain precise knowledge of the so-much debated course of
the fibres in the brain than all the methods hitherto tried. At
the most one could only, with the aid of the latter, see whether
numerous functional processes, collected into bundles, proceed in
certain directions, but with our technique one can examine them
fibre by fibre and follow their anastomoses.

" ' B. In all other methods we must, in order to obtain con-
secutive series of brain sections, bring the individual sections into
vessels with the staining fluid. As one cannot provide so many
vessels with fluid unless he possesses unusual means, several

* Camillo Golgi, " Di una nuova reazione apparentemente nera delle
cellule nervose cerebral! ottenuta col bichluro di mercurio." — Archivio per
le Sc. Med., Vol. III.

t Mondino, ' ' Sull'uso del bichloruro di mercurio nello studio degli
organi centrali del sistema nervoso." Communic. fatta alia R. Acad, di
Medi di Torino nella Seduta del 2 Genn., 1885.

164 A REVIEW OF THE GOLGI METHOD.

sections must be brought into one vessel, and can therefore only
be enumerated by groups, and not singly. By the method here
described this result can be attained with great ease.

" ' C. In the other methods the sections must be very thin,
and are liable to be torn in the various manipulations (from the
microtome into the staining fluid, then to the slide, etc.). As the
sections are very thin, they must be also much more numerous
when a whole brain is sectioned ; hence greater expense, loss of
time, and more labour in making the preparations. In our method
the sections need not be thin, they are therefore less numerous and
exposed to fewer risks ; whence little danger of losing sections,
slight expense in the preparation, and greater rapidity in the
preparation of a whole brain.

" * D, Finally, one must use in all other methods, dyes, com-
mercial and absolute alcohol, and clove oil or turpentine, while
we employ a little sublimate and creosote, which are very cheap
and inexpensive. In the other methods we must use cover slips,
because the high magnification which they require — and then one
does not see much — would not be applicable with the thick layers
of damar. We do not require this, and thereby escape not only
expense, but also the difficulty of avoiding bubbles of air under
large coverslips, whereby the preparation is often endangered.'

" It appears to me, apart from all economy of material, time,
and labour, as well as the convenience of cutting pieces in the
microtome so to speak at odd moments without injury to them
from the long contact with water, that this method, which enables
us for the first time to follow in sections the course of nerve fibres
through the whole brain, shows an advance in the technique of
the study of the central nervous system, and takes precedence
over all others.

" As I pass over the application for the macroscopical study of
the brain which Dr. Mondino has also made of this method, I
will here in conclusion again assert that the sublimate method
takes a high place among the microscopical methods for the study
of the nerve centres, alongside of the methods in which silver
nitrate plays the chief role."

Additional technical notes in Golgi's method, " Das diffuse
nervose Netz der Centralorgane der Nervensystems. Seine physi-

A REVIEW OF THE GOLGI METHOD. 165

ologische Bedeutung '' (from the Rendiconti des R. Instituto Lofn-
bardo^ Ser. II., Vol. XXIV., Fasc. 8 and 9), pp. 259 and 260 of
the German edition of Golgi's works :

" The Method which was most useful to me in the investiga-
tions described in the first part of this work, was the staining of
the nervous elements with mercury sublimate, but with a modifi-
cation which enhanced its demonstrative value without changing
the fundamental procedure. The latter consists (i) in the hard-
ening of the pieces in bichromate of potassium ; (2) in the
transference from this into a ^ per cent, to i per cent, solution
of bichloride of mercur3^

"Since I have given in another work (' Studi sulla fina ana-
tomia degli organi centrali del sistema nervoso,' p. 202) a detailed
description of what I call the fundamental part of the method, I
consider it fitting to add that the best and finest reactions in the
nerve fibres and the interstitial diffuse network was observed by
me in pieces (from the spinal cord of the new-born kitten) which
had lain a long time (in part over two years) in a i per cent,
solution of sublimate, after a long preceding sojourn in a bichro-
mate solution (first, Miiller's fluid ; then, pure bichromate to 3 per
cent). Since they were pieces which had lain in the laboratory
in this way ready for examination but had not been used, I can,
naturally, not tell what influence the long sojourn in the sublimate
may have exerted.

"The modification introduced by me, to which I must attribute
a certain value for the clear demonstration of fine details, and to
which I call the attention of the observer, consists simply in a
slight addition, viz., the blackening of the glistening white stain
which the nerve elements receive by means of the mercury im-
pregnation.

" As is known, the elements treated with sublimate appear
black in transmitted light, on account of the opacity caused by
the reaction, but in reflected light they appear white. This
difference may be easily observed by turning off the mirror of
the microscope.

" This kind of appearance is satisfactory for observation with

low or medium magnification, where less fine details are concerned,

but it is otherwise with the finer details, where stronger magnifica-

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. m

166 A REVIEW OF THE GOLGI METHOD.

Hon is required. In this case the metallic lustre of the fine parts,
e.g., the finest divisions of the nerve fibres, evidently affects the
observation unfavourably by giving the pictures a certain indis-
tinctness. The black stain which replaces the white-metalHc
brings out better the outlines of the fibres, and so increases the
demonstrative value of the preparation.

" Inasmuch as the impregnation consists of metallic mercury,
the transformation of the metallic white into deep black can be
accomplished, according to the teaching of elementary chemistry,
by means of a number of reagents. There can serve for this
purpose : the sulphite and hyposulphite (particularly sodium sul-
phite and hyposulphite in 5 per cent, solution), the sulphide (of
potassium, sodium, and ammonium, the first two in i per cent, to
2 per cent., the third in ^ per cent, solutions), sulphuretted
hydrogen (one part of the saturated solution and three parts of
distilled water). One can also use with advantage the sulphocya-
nide (of potassium, sodium, ammonium, in 2 per cent, solutions).

" The solutions of sulphite and hyposulphite, especially the
second, render necessary a careful watching of the preparations
that they are not entirely destroyed through a disappearance of
the metallic impregnation.

" The sulphides (of potassium and sodium) are easier to
manage, but the complete preservation of the preparations is not
entirely certain with them.

" The sulphocyanide acts very well in bringing into view the
smallest parts upon which the metallic impregnation has acted,
but it does not give a uniform black, only a brownish stain.
Besides this the cells and fibres under the action of this reagent
assume a punctate, almost pulverulent appearance.

" Sulphuretted hydrogen is very disagreeable on occount of its
offensive smell (a peculiarity which it has in common with ammo-
nium sulphide), and it also has a tendency (as has the ammonium
sulphide) to stain those parts containing no sublimate brownish,
which impairs very greatly the clearness of the preparation.

" From all these grounds, and, particularly on account of its
rapidity and certainty of action, on account of the intensity, uni-
formity, and sharpness of the black stain obtained, and on account
of the certain permanency of the preparations, the mixture used

A REVIEW OF THE GOLGI METHOD. 167

by photographers to stahi and fix their pictures upon aristotype
paper is to be preferred to all other substances given here (natu-
rally for the special purpose of the treatment of the sublimate
preparations).

" From the many formulse of this kind which are found in
books on photographic technique, I have adopted one which I
repeat in a footnote.'''

" The modification which 1 have adopted with my sublimate
method is as follows :

" The pieces which have been proven to be successfully im-
pregnated are embedded in celloidin in the usual way and cut with
the microtome. The sections are then subjected to the following
treatment :

"(i) Washing in distilled water.

" (2) Immersion one or two minutes (they can also remain
several minutes without injury) in the above fixing and staining
fluid. Several cubic centimetres of the fluid suffice for many
sections. The blackening can be observed with the naked eye.

" (3) Careful washing in distilled water.

" (4) If desired, light carmine stain to bring out the cell bodies
and nuclei in the fine interstitial nervous network. Acid carmine
is best adapted for this, according to my experience, and I find
especially suitable a dilution of this staining fluid with acetic acid
and alcohol (equal parts). The fluid into which the sections are
brought must have a deep red colour.

" (5) Repeated washing in water, and then successive trans-
ference into alcohol and clove oil, and finally mounting in Canada
balsam or damar in the usual way.

" Preparations treated in this way possess, besides the above-
mentioned advantages, the additional one that the fine powdery

* For toning the two following solutions are separately prepared :

(a) Water, i litre ; Sodium hyposulphite, 175 g. ; Alum, 20 g. ; Ammo-
nium sulphocyanide, log. ; Sodium chloride, 40 g. This mixture stands quiet
for 8 days, and is then filtered.

{b) Water, 100 g. ; Gold chloride, i g.

To prepare the bath one mixes of solution {a), 60 com. ; of solution {b),
7 ccm. ; old, combined bath, 40 ccm. For economy and convenience I use
fluid which has also served for toning, thus for this purpose almost useless.

168 THE PREPARATION OF BLOOD FOR

precipitate does not after a while appear. This precipitate ahnost
always, if there have not been previous repeated and long-con-
tinued washings, at last spoils the preparations prepared according
to the original method."

Zbc preparation of ffiloob for flDicroacopical

lEyanunatlon**

IN a recent number of the Medical Record^ Dr. Henry G.
Piffard alludes to a branch of blood examination, which, he
says, is exciting at the present time an increased and well-
merited interest. This is the preparation and examination of
blood spread in a thin layer and dried on cover glasses.

Blood films are studied from several standpoints and with
several distinct objects in view. These are chiefly : To determine
the presence or absence of malarial plasmodia ; to ascertain the
presence or absence of the eosinophile, neutrophile, or basophile
granules of Ehrlich ; to observe changes and abnormal appear-
ances in the leucocytes and red corpuscles ; and to determine the
presence and kind, or absence, of micro-organisms. In all these
cases the manipulation is substantially the same, with the excep-
tion of the stains to be employed. It is this technique, he says,
which he desires to describe in the fullest detail, and with special
reference to the slide, the glass cover, the needle, the forceps, the
spreading of the film, the fixing and dehydration of the corpuscles,
the staining, the mounting, and the optical apparatus, and espe-
cially the condenser and objective.

He states that the most satisfactory slides he has been able to
obtain are those furnished by Zeiss, at three and a half marks a
hundred. These are cut true to size (seventy-six millimetres by
twenty-six miUimetres), are of good glass, and are easily cleaned
for use with a drop or two of alcohol and a piece of Canton
flannel. Zeiss also supplies slides of plate glass at double the
price mentioned, but these it is almost impossible to clean with
either alcohol or acid. The slides chosen should be of medium

* From the New York Medical Journal.

MICROSCOPICAL EXAMINATION. 169

thickness. Very thin ones were formerly of service when attempt-
ing difficult resolution with extremely oblique mirror illumination.
With a substage condenser, however, extreme thinness of the slide
is not only unnecessary, but undesirable, especially in high-power
work. The majority of modern microscopes that are pretended to
have any degree of excellence are provided with substage conden-
sers, either N.A. i achromatic or N.A. i*2o, or 1-40 Abbe.

Now, these apertures are possible only when there is a layer of
cedar oil between the condenser and the slide. The principal
microscope makers list their condensers as having the apertures
mentioned, but not one of them, so far as he is aware, has the
honesty to state that these apertures exist only when they are used
with oil immersion, and that when used dry, as is usually the case,
the numerical aperture is very much less. If, now, the observer
desires to employ an immersion objective of high aperture and to
work it at its best, he must put oil on the condenser and focus it
for critical illumination. If the slide is an exceedingly thin one,
in bringing up the condenser to keep the oil in position, he will
project the flame image above the plane of the object under
examination. If the condenser is now depressed so as to make
the flame image coincide with the object, the oil is apt to run out,
especially if the microscope is incUned. The condensers are con-
structed to work with slides of medium thickness, and such slides
are the only ones that should be used.

Cover-glasses should be selected with great care. Square ones
should never be used in the preparation of blood films, because it
is exceedingly difficult to obtain a good smear, and it is almost
impossible to mount them in a satisfactory manner for permanent
preparation.

The most convenient size of round glass will be either three-
quarters of an inch or eighteen millimetres. American dealers
supply the covers in four grades, according to thickness — namely,
Nos. o, I, 2, and 3. The first two are altogether too thin for
general use, and should not be used under any consideration. A
great deal of blood work can be done better with dry lenses, and
the non-adjusting dry lenses in common use are corrected by their
makers for a certain definite thickness of cover-glasses ; and if a
thinner one is used, the image obtained will be imperfect. The

170 THE PREPARATION OF BLOOD FOR

cover-glass thickness will be found, therefore, to play an important
part in blood examinations.

The next step, continues the author, is the proper cleaning of
the covers. A small glass dish should be partly filled with battery
fluid (water, nine ozs. ; bichromate of potassium, one oz. ; sulphu-
ric acid, one oz.), and into this the covers should be dropped, one
by one, so that both sides of the cover may be wet by the fluid.
After remaining in this for twenty-four hours, the acid is poured off
and the covers are flushed en masse two or three times with water.
Then each should be taken separately and dropped into a dish of
distilled water, from which they are to be transferred, singly as
before, to alcohol (preferably pure methylic). A most convenient
receptacle for the alcohol and covers is a one-oz., square, screw-
capped bottle, in which they may be kept until needed for use.

A very convenient instrument for drawing the blood is a small,
straight, surgical needle, several of which should be kept in a
phial of alcohol until needed. For two years or so he has used
needles made from an alloy of one part of iridium and two parts
of platinum. When required for use, the needle is sterilised at a
white heat immediately before and also after use. The blood may
very conveniently be taken from the tip of the finger, though some
writers insist that it is better to draw it from the lobe of the ear.
In either case the part should be thoroughly cleansed.

Two forceps are required. One should be of the self-closing
variety, with flat, broad points, and with a spring sufficiently stiff"
to hold the cover firmly against moderate traction, The other may
be of any sort that will hold the cover nicely.

A sufficient number — say six or eight — of the covers are
removed from the alcohol, thoroughly dried, and laid upon any
suitable support, projecting a little beyond it. One of the covers
is seized with the self-closing forceps and placed ready at hand.
The puncture is then made, and another cover is quickly taken
with the second forceps and applied to the droplet of blood as it
issues from the wound. The second cover is then laid on the
first, and the blood spreads out between them. A common fault
with beginners is taking up too much blood; but this will be cor-
rected after a little practice. As soon as the film is spread, the
projecting edges of the upper cover are taken between the thumb

MICROSCOPICAL EXAMINATION. l7l

and the index finger, and the covers are gently sHd apart, care
being taken to keep them parallel until they are entirely separated.
The two covers, v^^ith films up, are now laid on a piece of paper to
dry, and a second pair are prepared in the same manner. If more
than four covers are desired, a fresh puncture should be made.
As soon as the films are dry, they may be placed in a small enve-
lope and properly labelled. If they are stored in a dry place, they
will remain unchanged for a long period. It is better, however, to
fix them immediately. If water or any staining fluid was to be
applied before fixing, most of the corpuscles would be washed off
the cover, and from those that did remain the haemoglobin would
be removed, leaving only the invisible stroma.

With regard to fixing the corpuscles, says Dr. Piffard, the best
method, and one which his own experience leads him to prefer, is
with heat rather than any of the other methods that have been
employed. For the past year, for this purpose, he has used an
electric heater controlled by a rheostat. The covers are heated
gradually to about 2 2 5°F. and then maintained at this for an hour
or more. When the covers are taken from the oven, they are
allowed to cool gradually and thoroughly before staining.

When ready to stain the covers, they are placed film up on a
plate of glass, and covered each with the eosin solution. This is
left on for two or three minutes, and washed off with distilled
water. When the covers are dry, the methylene-blue solution is
applied in the same manner ; and when this is washed off, and the
covers are thoroughly dry, they are ready for preliminary examina-
tion.

The microscope is arranged vertically, with a clean slide on
the stage, and the cover is placed on it, film down and without
any intervening medium. Alongside of it, if it is desired, another
cover is mounted in balsam and the two are compared. The dif
ference between the two is so striking and absolutely in favour of
the dry cover that Dr. Piffard thinks the balsam would be rejected
for this purpose. This examination must, of course, be made with
a dry lens. A No. 7 Leitz answers very well, but an eighth of an
inch or a tenth of an inch objective, with a numerical aperture
approximating 0*90, is still better.

If the examination with the dry lens does not give all desired

172 PREPARATION OF BLOOD FOR EXAMINATION.

information, and a further examination is desired with a higher-
power immersion, it will be necessary to attach the cover perma-
nently to the slide.

If blood covers are to be mounted to the best advantage, the
first step is to procure a turn-table. The slide is carefully centred
on this, and a thin ring of shellac or other suitable cement spun,
corresponding to the size of the cover ; a second coat may be
applied a few minutes later. A number of slides are prepared in
this way, and left for twenty-four hours or more to dry.

When the slides are ready for use, one is taken and held over
a flame for a moment or two to expel all surface moisture and to
soften the cement a little. The cover in like manner should be
flirted over the flame, to expel all moisture from its surface. It is
then applied to the cement ring, care being taken to have contact
at all points of the circle. When entirely cold, a fresh ring of
cement may be spun around the cover, so as absolutely to seal it
at every point. The slide is now ready for examination in any
manner, and with any dry or immersion lens.

It matters not, says the author, whether we are studying the
changes in the leucocytes, hunting up the various granules of
Ehrlich, or searching for the elusive plasmodia, the optical picture
will be vastly superior and much more instructive than any we
can obtain in balsam mounts.

In regard to the substage condensers, he continues, if circum-
stances restricted him to the use of a single condenser for all pur-
poses, he would choose an achromatic N.A. i, which may be
obtained of excellent quality from Zeiss, Bausch and Lomb,
Watson of London, and other makers, costing perhaps ten or
twelve dollars more than the customary Abbe. With dry lenses,
except those of the very widest aperture, it should be used dry —
that is, without oil between the condenser and the slide. By so
doing the nominal aperture will be impaired about a third and
thrown a little off its corrections ; but even then it will be better
than any of the Abb^ construction. If used in connection with
immersion lenses, oil contact should be used so as to secure the
full aperture. If circumstances permit the expenditure, an addi-
tional achromatic of N.A. 1*30 to 1*40 should be added ; and for
low-power work, an achromatic of low aperture — say^ N.A. o"6o to

SELECTED NOTES. l73

0*75. In regard to the Abbe condensers that are in such general
use, it may safely be said that they are a vast improvement on
simple mirror illumination, that was almost the sole dependence
before Professor Abbe introduced his simple device. The low
cost has undoubtedly been the chief means of its wide introduc-
tion, but as an optical instrument of precision it is decidedly infe-
rior to an achromatic of approximate aperture.

Through force of circumstances, fully nine-tenths of the labo-
ratory workers employ diffuse dayUght as an illuminant, and for
the great mass of work to be done it is amply sufficient and satis-
factory ; but for the most delicate work a well-arranged artificial
light is preferable.

At the present time, says Dr. Piffard, the blood offers one of
the most inviting fields of investigation, as an aid both to diag-
nosis and to therapeutics ; and he strongly urges on those who
design to take it up to pay the strictest attention to what at first
may appear to be unimportant technical details.

Selecteb IWotee from tbe IRotc^BooF^a of the
Ipoetal flDicio0copical Society.

Hnatomy ot Btptera.

By W. Jenkinson. Plate IX.

PERHAPS the slides circulated herewith will interest only a
few members of the Society, but from those few I ask fair
criticism and kind suggestions where difficulties occur.
Except in Classification the English Flies have had but scant
attention. We know comparatively little of the life-history of
these common insects ; certainly the Rev. J. G. Wood has done
something towards making a few species popular, and Mr. B. T.
Lowne has given us his Monograph on the Anatomy and Physio-
logy, yet the subject is far from being exhausted.

Sections of the Tarsus and Pulvilli of Sarcophaga carnaria

(PI. IX., Fig. i), stained with borax-carmine. In this fly the
pulvilli are abnormally large, and for that reason I have chosen it.

174 SELECTED NOTES.

The upper wall of the pulvillus is composed of chitinous semi- or
half-tubes directed lengthwise, and joined together at their edges,
thus forming a very flexible roof. The lower surface is clothed
with fine tapering, unpigmented hairs ; these hairs are commonly
said to be hollow, but I have searched in vain to find a lumen in
them. In some species the hairs are trumpet-shaped — e.g.^ in
those of the Gad-fly and a parasite from an Indian bat.

Common with the pulvilli of other flies, I find they contain
glands, but neither muscle nor nerve. The sections under notice
are very rich in glands, which evidently elaborate the viscid fluid
by which the fly is enabled to walk in an inverted position on the
ceiling or on glass. Here we meet with a difficulty. If the hairs
are not hollow, and there are no openings in the lower wall near
them, how does this viscid fluid get on to them ? I shall be glad
of any suggestions on this matter.

It has occurred to me that, beyond the circumstance men-
tioned above, the viscid fluid may fulfil a much higher purpose to
man and other animals. In flies which deposit their eggs upon
decomposing and often diseased animal matter, but do not feed
upon such matter, the fluid would entomb any disease-germs taken
up by their feet — that is, supposing the fluid hardens on exposure
to the air like the fluid emitted by the spinnerets of spiders and
the larvae of some Lepidoptera. I do not wish to imply that flies
do not disseminate disease-germs. This, I believe, is frequently
done when they feed on fluids containing such germs, by carrying
them on their proboscis to pure fluids, on which they afterwards
regale themselves,

Hilaria pilosa, Longitudinal section of the Tarsus of Male. —
In the male insect the first joints of the anterior tarsi are greatly
enlarged. In this section the most prominent feature is the
numerous large glands with their ducts ; the apodeme, which
moves the joints, the nerve, and tracheae, are also shown, whilst
no muscle is visible. The ducts penetrate the inner wall of the
joint, and the outlet can be seen in one of the sections.

The purpose of the secretion from these glands is, in all pro-
bability, the same as those in Water-Beetles, where the glands
have their outlets in both the large and small discs on the anterior
feet.

SELECTED NOTES. 175

Head of Blow-Fly (three transverse sections). — From the
amount of loose embryonic cells seen in these sections, it is evi-
dent that the fly had biit recently emerged from the pupa case.

On the first of these slides are numerous portions of the brain
and optic tract, and as they are fairly thin (about 1/80 mm.) most
of the recent discoveries may be compared with them. M. N.
Newton states in the Magazine of Natural History^ 1879, P- 397 '-
" In the cerebroid or supra-oesophageal ganglia are situated the
organs of perception, of memory, of intelligence, etc. Hence
they have a more complicated histological structure than the sub-
cesophageal ganglia which principally govern the appendages of
the mouth. These nerve-centres are nevertheless constructed on
the same general plan as the other ganglia. In the middle they
present bundles of nerve-fibres, while the nerve-cells principally
occupy the periphery."

In these sections nerve-fibres may be traced from the centre of
the oesophageal ganglion to well-defined peripheral nerve-cells.
There is here a Hkeness to the Vertebrata, though in almost every
other respect, with the exception of the muscles and nerves, we
find the opposite.

The compound eye and optic nerve has been so well worked
out by Hickson, that I would refer our friends to his paper which
appeared in The Quarterly Journal of Microscopy, No. XCVIII.
In Fig. 2 I give a tracing from this paper, showing one facette of
the eye and with it terminal fibres, etc.

The second slide shows several sections through the frontal sac.
Lowne believed this to be an olfactory organ, adapted to the
appreciation of powerful odours. If we look at the head of the
insect as an almost closed sac, bounded by rigid walls, and with
all otherwise unoccupied spaces filled with a circulating fluid (the
blood), whose communication with the thorax is by a very small
neck, and that small space taken up by the oesophagus, nerve-
cords, and tracheae, it is evident that the blood could not pass so
quickly into or out of the head as would admit of the quick pro-
trusion of the proboscis (see Fig. 3). Hence, in the frontal sac
there is a beautifully simple contrivance well adapted for such a
purpose. It is a simple sac suspended near the upper wall of the
head, with the wider surface hanging in numerous folds. The sac

176 SELECTED NOTES.

is in free communication with the outer air through an opening in
the forehead immediately above the antennae. The outer surface
is covered wi^h numerous papillae. When the folds are brought so
close together that the papillae interlock, they always enclose some
air, thus preventing any adhesion of the surfaces, which might be
the case if the surfaces of the folds were smooth and moist. By
this means an equable pressure is maintained on the brain and
other organs. Some years smce (1887 or 1888) I read a paper
before the Sheffield Microscopical Society on the " Frontal Sac."
This was published in Science Gossip without my consent and con-
sequently without my signature.

The third slide shows sections of the antennae. These sec-
tions are mostly cut through the second and third joints, the first
joint not being in the same plane. Exteriorly the third joint is
covered with two kinds of pigmented hairs. The finer and
smaller appear to be nothing more than clothing ; but the larger
ones are hollow, their lumen continuing through the chitinous wall
of the joint. Epithelium lines the interior of the joint, the ends
of the cell being drawn out, and projects into the lumen of the
hairs. This is distinctly seen in thin sections, in which the epi-
dermis became somewhat detached from the epithelium during the
manipulation of the section. From the nerve numberless fibres
are seen to enter the epithelium lining, but I have been unable to
trace them any further.

By using a more suitable stain, the nerve-fibres may possibly
be traced through the epithelium, or the epithelium may be
endowed with the same conducting power as the nerve-fibre. From
this rich supply of nerve matter, it is pretty clear that the large
hairs must be the seat of some sensation, but what sense they
represent is very difficult to prove by experiment, because another
sense-organ is intermingled with them. It is highly probable that
these are tactile organs, though this term is very vague, for it
implies the sensation of either cold or heat, humidity, or touch,
etc., and for this reason I am of opinion that further proof is still
required.

The most highly developed tactile hairs are those on the lobes
of the proboscis, where they end in a large bulb in immediate
connection with the nerve. By their position they are undoubtedly

SELECTED NOTES. 177

organs of touch, and may be seen very distinctly in a vertical
section of a well-distended proboscis (see Fig. 4).

Another feature well developed in the third joint of the
antennae of the Blow-fly, and many of the other domestic species
of flies, is a somewhat spiral organ covered on the exterior with
fine impregnated hairs; these hairs penetrate the wall of the
organ, which is also lined on the interior surface with epithelium
and receive a rich supply of nerve-fibres. It is computed that
there are about eighty of these organs in the one antenna of the
Blow-fly, and from their position, and the well-known highly deve-
loped sense of smell possessed by this insect, there can scarcely
be a question but that they are olfactory. The extreme paucity
of these organs in other species of different habits strengthen my
convictions on this subject. Among these are the common Dung-
fly, Eristalis tetiax^ Rhingia rostata, and a host of others.

Eristalis tenax, longitudinal section of haltere.— For conven-
ience of examination the haltere of the fly may be divided into
three separate parts — viz., base, pedicel, and globe or head. On
the exterior surface of the base there are three distinct areas or
sets of sense organs, which severally have an anterior, posterior,
and lateral aspect. These have long been considered to be special
sense organs. The lower area is somewhat rounded on the face,
and covered with delicate elevations of the epidermis, which take
the form of circular papillae. They are divided into rows, and
between each row there is a line of curved hairs. Lowne states
that there are two distinct sets of these lower organs, and Theo-
bald, in his new work on British Fiies, has repeated this statement ;
but in no instance have I met with more than one, and it has
invariably a lateral aspect. The two upper organs are placed on
opposite sides of the haltere — one anterior and the other posterior.
They are much longer and larger than the lower one, but are like
it in having rows of ridges beset with papillae^ separated by fine
hairs.

Several sections show the lining epithelium remarkably well.
In this place it is specially modified to form a sensory or nerve
epithelium. The pointed ends of the cells are seen penetrating
the papillae of the lateral organ. The halteres receive their rich
supply of nerves direct from the second thoracic ganglion. This

178 SELECTED NOTES.

pair of nerves is the largest in the thorax and crosses to the oppo-
site sides immediately on entering the ganglia. The pedicel is a
hollow tube connecting the base of haltere with the globe. On
the external surface it is covered with hairs ; the interior is divided
by a septum, which is continued the whole length of the pedicel ;
a large tracheal vessel passes through it to the globe, where it
breaks up into many branches, which ramify in the tissue. I have
not been able to trace any more in it.

Sarcophaga carnaria, longitudinal sections of haltere.—

These show the vascular tissue in the so-called globe of the haltere
(see Fig. 5). In all the halteres I have examined the deep invagi-
nation seen in these sections of the globe is invariably present, and
there is always a mass of connective tissue extending from the
invaginated wall to the opposite wall of the globe. The purpose
of the invagination I do not know, unless by some means it allows
of a certain amount of expansion and contraction of the globe.
The large glands most probably secrete a fluid necessary for organs
at the base of the haltere.

The halteres of diptera doubtless assist in their locomotion,
but the evidence of their elaborate structure proves that they have
another most important function. The position of the papillae is
such as to present a front in every direction, and their structure is
so delicate as to permit vibration when sound-waves or other
movements of the air impinge upon them. The nerve epithelium,
bathed in fluid which is secreted in the globe, together with the
very rich nerve-supply, also point to their being rudimentary audi-
tory organs. Otoliths, so commonly found in the Crustacea and
Mollusca, I have not met with here, but it is no proof that they
do not exist.

The great number of papillae (four hundred to five hundred) in
each haltere, and the small number of olfactory organs (two in
each antennae) found in many flies which feed on the nectar of
flowers, compared with M. vomitoria and M. domesttca, whose hal-
teres carry half the number of papillae, and in whom the olfactory
sense is highly developed, show that the former possess an acute
sense to warn them of danger when their heads are buried in the
blossoms of the plants they frequent, and that the latter have
comparatively little use for such a sense.

SELECTED NOTES. 179

Blow-fly, Anterior thoracic spiracle of. —This spiracle is oval
and narrowest above, and is situated between the pro- and meso-
thorax. From the exterior free edge project hollow, arborescent,
chitinous rods which curve outwards, and interlock for about one-
third of the length of the spiracle. These rods are hollow even to
the minutest twigs, and have free openings at their points ; close
behind is a transparent membrane, the true valve, which is united
to the wall of the large tracheal vessel, which extends across the
thorax to the opposite spiracle. The free edge of the valve is
closely set with a chitinous fringe. A special muscle arises from
the integument at the lower end of the spiracle ; by the contrac-
tion of the muscle the free edges of the valve would be caused to
approach each other. From the integument another set of muscles
arise and are directed towards the valve, but whether they are con-
nected with it I have not been able to determine ; antagonistic
muscles are a necessary consequence for working the valve.

The structure of the posterior thoracic spiracle is very similar
to the anterior one, excepting that the external chitinous rods are
formed into two distinct masses by the addition of a connecting
membrane.

Sericomyia borealis, Posterior thoracic spiracle of.— This spi-
racle differs from the corresponding one of the Blow-fly in having
the chitinous rods free, and also that the walls behind the valve
are lined with walls of membrane, the edges of which are directed
inwards.

Abdominal Spiracle of Blow-fly.— The spiracles of the abdo-
men are very much smaller than those of the thorax, their relative
sizes being as i to 7. The spiracle is round, fringed with fine
hairs, and the valve, which is placed a very short distance behind
it, appears to consist of a thickened membrane on the one side
which gradually thins out towards the free edge. The other half
is thinner and more flexible, and its movement is effected by a
curved rod or bow, hinged at one end, the other being connected
with a set of muscles arising from the edge of the spiracle. No
antagonistic muscles have been found by me, but if air is both
received and expelled by it, such muscles are certainly requisite.

It is the generally accepted theory that all the spiracles are

180 SELECTED NOTES.

both afferent and efferent ; but, judging from the observations of
others, as well as my own, I must confess that I am somewhat
sceptical on the subject, and it is with the hope of having the
matter thoroughly discussed that I have placed the slide in the box.

The minuteness of the opening of the abdominal spiracles and
the almost immediate branching of the large tracheal vessels are
eminently suited for the exclusion of dust particles ; and the quick
distribution of inflowing air, to which may be added the adaptabi-
lity of the abdomen for rhythmical expansion and contraction,
leaves no doubt that the supply is obtained through these spiracles.
To be able only to assert that the tracheae branch and re-branch
until they end in mere blind twigs, and that the air is constantly
being changed in them, without being able to discover the cause,
is, to say the least, unsatisfactory.

By mounting fresh insect muscle in strong glycerine, I have
succeeded for a time in retaining air in the smallest tracheal vessels,
and believe that I have traced a connection through them to and
from the larger tracheae. My difficulty in following them was so
great and perhaps uncertain that I should be glad to have my con-
jectures confirmed by more able observers before it can safely be
stated as a fact.

On the other hand, the thoracic spiracles in the Blow-fly and
in many other insects are large and open outwards, so that there
is little or no protection against the entrance of dust particles ; the
various parts also of the thorax are so firmly soldered together as
to make it almost rigid. These spiracles appear to me to be pur-
posely and peculiarly adapted for carrying off the expired air and
vapour from the body.

There is yet another purpose which these spiracles may pro-
bably serve — namely, the production of sound. The well-known
buzzing of the fly can be varied in tone or may cease altogetfier,
as circumstances require. Is it not conceivable that by varying the
size of the opening of the valve of these spiracles, and thereby
increasing or diminishing the pressure in the large air-tubes con-
nected with them, such variations of sound may be accounted for?
When the wings and halteres of the fly are removed ,the sounds
produced are as loud as before removal, and the muscular exertion
is always great when sounds are produced.

SELECTED NOTES. 181

I desire to express my great pleasure in the examination of
Mr. Jenkinson's beautifully mounted slides, and in the perusal of
his interesting and instructive notes, as well as my satisfaction in
seeing the work of so earnest and careful a worker circulating
among our members.

Hairs on the Pulvilli of Flies.— With regard to the difficulty
respecting the hairs on the pulvilli of flies, is it to be expected that
the hairs should be hollow, and in the nature of ducts for the
viscid fluid secreted by the glands ? Do they — the hairs — not act
rather as a simple mechanical method for enabling the insect
instantaneously to detach its foothold from the object upon which
it has been resting ? and supposing the pulvillus to be hairless, and
the secreting surface to be brought into close connection with the
object, would there not be great difficulty in the creature at once
liberating itself?

Frontal Sac— The function of the frontal sac is a very inter-
esting subject, and I am inclined to agree with Mr. Jenkinson that
it acts largely as a compensatory arrangement in the adjustment of
the pressure upon the organs of the head, in which the protrusion
of the proboscis and its retraction must otherwise occasion con-
siderable variation, but at the same time it doubtless fulfils other
purposes.

I have not yet seen Prof. Lownes' new edition of his work on
the Blow-fly, in which, however, I believe he has in several ways
considerably modified his views on certain points communicated
in his first edition ; and do not know whether the views he held
upon the frontal sac are in any way altered, but I think he there
ascribed several functions thereto. The first of these was that this
sac effected the purpose of a lever to enable the maturing imago
to escape from the pupal case by forcing off" the upper end and so
permitting the insect to escape. At this time the frontal sac,
which forms a cavity in the head of the mature fly, is everted, and
forms a protuberance in front of the head, which, however, imme-
diately after convergence, collapses and is withdrawn into the head,
from which, by a slight pressure, it can be again made for a short
time only to protrude.

The second function is in connection with the humming of the

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. n

182 SELECTED NOTES.

insect, as he says the facial plate is caused to vibrate rapidly during
the emission of sound, which in the apparent absence of sufficient
muscular power it is difficult to conceive.

The last is that it is an olfactory organ, though with a limited
nerve supply, by means of which the creature is enabled to appre-
ciate powerful odours. Mr. Jenkinson's last suggestion — viz., the
function of the laterally opening tracheae in the interior of the
body by means of capillary vessels — or something analogous — it
seems to me, will be very difficult to establish ; and if so, the
advantage of such connection would appear doubtful owing to the
extreme minuteness of such capillaries did they exist, for any
exchange of air in the tracheae which is effected by the respiratory
movements of the abdomen could hardly proceed more rapidly
one way than the other. E. Bostock.

Hairs on the Pulvilli.— I quite agree with Mr. Bostock that
the hairs beneath the pulvilli may act mechanically in helping to
relieve the foot. My difficulty is simply this : — If the glands in
the pulvillus secrete a viscid fluid, how is that fluid conveyed to the
under-surface of the pulvillus ? When I approached the subject,
I expected to find a lumen in each hair, or, failing that, minute
ducts passing through the external wall, but I can find neither.

The Frontal Sac is continuous with, and is simply an invagina-
tion of the epidermis. It is a flexible bag, floating in and sur-
rounded by fluid, and in my opinion is unsuitable for producing
quick vibrations, but would rather tend to subdue them ; hence, I
think, we must look somewhere else for the "humming" organ.
It is equally unsuitable for an olfactory organ, because its only
nerve-supply could be obtained by its outer edges, and these would
be very limited, even if they exist at all, which is extremely
doubtful.

The experiment of placing the thorax of a cricket under
water, while the abdomen had free access to the air, showed
bubbles of air emitted from the thoracic spiracles, without the
insect being in the least exhausted. When the abdomen was
immersed no bubbles were emitted, and the insect suffered from
exhaustion. Such, experiments, coupled with the construction of
the thoracic spiracles, suggest that they are outlets for the expired

SELECTED NOTES. 183

air. Minute air-vessels do exist in very great numbers, both in
the thorax and abdomen. W. Jenkinson.

I think we have never had any box that could beat this, and
very few that could come up to it. If there are any members who
(as Mr. Jenkinson thinks) can feel no interest in these slides — well,
so much the worse for those members ! If members generally
would take half the trouble that Mr. J. has taken to please and
instruct, and if they would (as Mr. J. has done) send out their
best slides, then I think the prospects of the Society would
rapidly improve.

Tarsus and Pulvilli.- I am not quite sure what is meant by
" semi- or half- tubes " ; the tubes seem to me to be separate. I
do not see why the walls of the gland-cases should not be porous
and the viscid fluid ooze through. I consider that the suggestion
that the viscid fluid takes up and retains disease-germs for the
benefit of man wholly ifiadmissible. I believe it to be an axiom in
evolutionary science that no creature developes any organ or habit
for the benefit of any other, unless it is itself benefited by benefit-
ing the other, as in the case of the ants and the thorny acacia of
South America.

The opinion of Mr. Newton as to the Organ of Memory in the
head of the Blow-fly seems very daring' and entirely unverifiable.

Frontal Sac— I confess I do not understand the speculations
on the function of the frontal sac. Is it meant that when the pro-
boscis is protruded it is distended with air ? I should have sup-
posed from analogy it was more likely distended with blood.

With regard to Mr. Jenkinson's postscript, the experiment with
the cricket seems to establish the theory of the efferent functions
of the thoracic spiracles ; but to make the proof complete it would
be necessary to establish a connection between the tracheae of the
abdominal and of the thoracic spiracles ; or might it be possible
that the air introduced by the afferent tracheae should be dis-
charged into the cavity of the body, and taken up thence by the
efferent tracheae to be discharged through the thoracic spiracles ?

R. S. Pattrick.

184 SELECTED NOTES.

Haltere of Sericomyia borealis. — An examination of the haltere
above the spiracle on this slide, with a Zeiss' |-inch apochromatic,
shows its head to be trumpet-shaped, not globular, the trumpet
part being apparently continuous, with a long tube leading to the
special sense-organs below. Of course, the head may have been
globular and have become conical by shrinkage, but I do not
think so. Wm. Gifford.

EXPLANATION OF PLATE IX.

Fig. 1. — Section of Pulvillus of Sarcophaga carnaria. * jj.io., Posterior
wall ; s.t., Semi-tubes ; g., Glands ; /?., Fine hairs.
,, 2. — One facette of Eye. c, Cornea; p., Pseudocone ; p.c. , Pig-
ment cell; n.p., Nuclei of Pseudocone; ?/.r.. Nucleus of
Retmula ; v., Retinula ; ^7;., Rhabdom ; t.v., Tracheal vesicle ;
6.C., Basal pigment cell ; t.f., Terminal fibres.

,, 3. — Vertical Section through Head of Blow-Fly. e., Compound
eyes ; /.s. , Frontal sac ; p.h., Base of Proboscis retracted.

,, 4. — Longitudinal section of third joint of Antennae of Blow-fly.
e.d.. Epidermis ; e})., Epithelium ; n., Nerve ; s.h., Sensitive
hairs ; ol., Olfactory organs.

,, 5. — Section of Globe of Haltere of 8arcop>liaga carnaria. i.,
Invagination ; c.t., Connective Tissue ; </., Glands.

Additional Notes.

Peronospora infestans (PI. XL) {Phytophthira of De Bary)
belongs to Oosporece, a group of Thallophytes distinguished by
their organs of reproduction — peculiar large cells called oogonia or
resting spores. P. infestans is remarkable for possessing two
modes of reproduction — first, a sexual one by oogonia and anthe-
ridia ; second, an a-sexual one by gonidia or buds (compare
Marchantia polyi?iorpha among the Hepaticae). The drawings on
Plate XL are partly copied from Sach's Text-book of Botany^ which
illustrates the life-history of this plant.

In July or August it is first observed forming yellow spots on
the leaves of the potato, which then turn brown and wither. The
underside alone of the leaves is at first affected, as the stomata
there afford an easy mode of entrance to the germinating mycelia
of the fungus. In Fig. 2, Z, this is seen. The mycelia put forth
haustoria. Fig. 2, into the protoplasm of the cells to suck up
the sap, and the withering of the plant is caused by the fungus

Journal of Microscopy 3^-^ SerVol. 6, Plate 9.

SELECTED NOTES. 185

thus exhausting the protoplasm of the cells. After the mycelia
have obtained a lodgment and ramified through the intercellular
spaces of the potato, bi-anches are pushed out through the stomata
on the underside of the potato leaves, and on the ends of these
the gonidia are formed (Fig. i,^). These branches are remark-
able in form, resembling a string of beads. They, as well as the
gonidia at their ends, are white, and give a hoary appearance to
the diseased leaves.

The resting spores of this fungus were discovered by Mr.
Worthington Smith. Those of a similar kind of fungus, Cytopus
candidus, are copied from De Bary's figure in Fig. 6. Those seen
in the slide are represented at Fig. 3. Two kinds of spores seem
to be present — a few large, light-brown ones and a number of
small, dark-coloured ones, I presume the latter are gonidia and
the former oospores. Fig. 5 shows the mode of fecundation
of the oospores in Cytopus.

I have a few leaves of the potato with the disease on them in
my possession ; on these I notice some small, round, rose-coloured
bodies which puzzle me. C. H. Waddell.

As to the restifig spores of the potato disease, they will be seen
best by day-light illumination and a J-inch o.g. There are two
schools : — First, those who believe that the mycelium lives all the
winter in the tuber, grow up in the summer, and thrives as the
plant thrives, and appears through the stomata. The second
school is of those who hold that the harm is in the resting spore.
This is the product of last year's disease, produced in exhausted
seeds and intercellular structures, in decaying potatoes and plants,
among manure, or in fields. It is produced by the union of pro-
toplasms of two cells. An interesting article on this subject will
be found in the English Mechanic of May, 1881. C. P. Coombs.

Larva of Stratiomys chamseleon (Plate X ). — This is a dipter-
ous larva, common enough at Sheerness, and I daresay in other
parts of the country. It is a repulsive-looking object, that floats
inertly on the surface of the water in ditches and ponds. One
might easily think it inanimate, but a touch with a stick causes it
to twist and writhe for a moment ; it then relapses into a quiescent
condition. This creature is roughly portrayed in PI. X., Fig. i.
It is the larva of a handsome fly, Stratiomys Chamceleon. There

186 SELECTED NOTES.

are many points of interest about it, only a few of which I can here
touch upon. It might easily be a subject of wonder how so help-
less a creature, whose habitat renders it so peculiarly liable to
observation and attack, could survive the assaults of its numerous
enemies ; and the answ^er is doubtless to be found in the structure
of its skin, as shown in Figs. 2 and 3. This skin is extremely
tough, and yet flexible to allow the freest motion to every segment
of the body. It is a veritable coatof-mail. Certain cells of the
cuticle are developed into horny studs which beset the surface, and
form a complete protective covering, the substratum upon which
they are placed being soft and flexible.

The tail exhibits a coronet of branching hairs, one of which is
seen in Fig. 6, and these surround a couple of peculiar oval spi-
racles, one of which is shown in Fig. 5. I have not a very good
drawing of the Fly itself, but Fig. 4 will give some idea of it.
The pupa is developed within the skin of the larva, of which it
occupies only the anterior portion. A. Hammond.

Ditto. — Those who possess Donovan's British Insects will find
at p. 65, PL XXXI., a coloured figure of the fly under the name
of Musca Cha??ieleon, and at p. 77, PI. XXXV., a figure of the
larva. Mr. Hammond's further figure, showing the peculiar struc-
ture of the skin, is very welcome and interesting, and well proves
that good objects for the microscope, as well beautiful as interest-
ing, abound everywhere, and only require looking for. The
present creature appears to have had its name changed, at least,
four times. This is rather a difficulty in the way of the beginner.
Donovan says that in a former edition of his fauna, Linnaeus calls
it CEstrns aqucB., Frisch Taba?ius aquaticus; in the last edition of
Fauna Suecia, My sea Chameleon; and now it has become Stratio-
mys Chamceleon^ let us hope it has now acquired its final name, at
least for this century. C. F. George.

• EXPLANATION OF PLATES X. & XL

Plate X.

Fig. 1.— Larva of Stratiomys chamceleon.
,, 2. — Portion of skin of same.
,, 3. — Section of ditto.

Journal of Microscopy 3^ Ser.Vol. S, Plate 10

iffmn

Si!^ra7!^ili:??77yi/s {^/^a^z^li^^ny.

^- //a/n^^ 6>/?a^ /^/. .S. ^zi^ '/jar K/e/.

/^/'/rM/ysSc

Journal of Microscopy 3- Ser Vol 6, Plate 11.

Pg-..

PeroTztPSpora. ^/^^ (^ys^^/?u^s.

C//. IVa^ia^.

F. P/?////ps Sc.

SELECTED NOTES. 187

Fig. 4. — Ventral surface of imago.

,, 5. — Spiracle.

„ 6. — Hair from Coronet.

Plate XI.

Fig. 1. — Peronospora infestans. g., Gonidia in situ on ends of mycelia
projecting from stoma of leaf. (After Cooke.)

,, 2. — z., Zoogonidia penetrating epidermis of Potato stem (after
De Bary).

,, 3. — Spores of Peronospora infestans, as seen on slide.

,, 4. — Cytopus candidns. Branch of Mycelium with haustoria (h.),
penetrating between parenchymatous cells.

,, 5. — o.g., Oogonium ; os., Oosphere ; aii., Antheridium in Cytopus
candidus (after De Bary).

,, 6. — Mycelium (m.) with young oogonium (o.g.).

flDicroecopical ^ecbnique.

Preparation of Frozen Sections by means of Methyl and
Ethyl Chloride.*— In September, 1895, while watching Dr. John
B. Deaver perform a minor surgical operation with ethyl chloride,
the thought occurred to rae that this re-agent might profitably be
employed in preparing frozen sections for histological purposes.
The results thus far obtained have been exceedingly satisfactory,
and, while the method is somewhat expensive, no accessory appa-
ratus is required for the microtome.

Hamilton's method of preparing the tissues for freezing gives
good results ( Text- Book Pathology, by D. J. Hamilton, Vol. I.,
p. 58). Another way of getting the tissue ready is that recently
advised by J. Orth (Berlin klin. Woch., No. 13, 1896). One
hundred parts of Midler's fluid are mixed when wanted with ccn
parts of formol. Small pieces of the tissue under examination are
fixed and hardened in this solution in the incubator for three
hours. At the end of this time they are removed and thoroughly
washed, and alcohol is gradually added until they are placed in 95
per cent, alcohol. This latter re-agent must, of course, be removed
before the tissue is frozen. If desired, after washing, the specimen
may be at once transferred to the solution of acacia and sugar and
*From International Medical Magazine, Dec, 1896, pp. 706 — 7.

188 MICROSCOPICAL TECHNIQUE.

frozen. Or, as suggested by H. Plenge ( Virchoiv^s Archiv., Vol.
cxLiv., p. 409), the piece may be placed in a 4 per cent, formal-
dehyde solution for a quarter-of-an-hour, and then frozen in the
same solution.

When the tissue has been prepared in some such manner, or
even when perfectly fresh, it is placed with some formol and gum
acacia fluid upon the specimen-holder of the microtome, and a
small stream of chloride, methyl chloride, or anestile (a mixture of
these two re-agents) is played from above directly upon the speci-
men. The tube containing the ethyl chloride is held about a foot
from the specimen, and moved from place to place until the spe-
cimen is firmly attached to its base of support, and the upper
portion is coated with a few crystals of ice. These crystals are
extremely small and delicate, and, therefore, do not injure the
tissue so markedly as in some other of the freezing methods. The
specimen is readily frozen in from thirty seconds to a minute.
Sections are then cut and placed in water or fifty per cent, alcohol,
and mounted in the usual way. Excellent stained preparations
may be prepared in fifteen minutes or less from the time that the
tissue is removed from the body.

We hope to give a later and fuller report of this process at an
early date. H. W. Cattell.

Formaldehyde in Pathological Work.— Orth (Berl. klin. Woch.,
March 30th, 1896) draws attention to the value of this agent in
pathological work. Formol, or formalin, contains 40 per cent,
formaldehyde. It is generally known that formol is an excellent
hardening agent for most tissues, and especially for the brain, as
well as for red blood-cells, which it preserves and fixes. Both for
naked-eye and microscopic purposes the author has employed a
10 per cent, formal in Miiller's fluid. After two or three days this
solution becomes dark, and in four days a crystalline deposit
separates out. Thus the fluid requires changing in this time, but
mostly the hardening process is already completed. Small pieces
of tissue, measuring ^ to ^ cm. in thickness, are thoroughly
fixed and hardened in three hours in a warm chamber. Larger
pieces may remain overnight, and this time suffices for small pieces
at room temperature. The Miiller is washed out with water. The

MICROSCOPICAL TECHNIQUE. 189

specimens after washing can be put in 93 per cent, alcohol, and if
the washing has only taken a short time they may be left in it from
twelve to twenty-four hours. Remaining in the fluid for three or
four days at room temperature does not injure the specimens, but
rather facilitates the subsequent staining. Karyokinensis may thus
be more frequently observed. Carmine preparations, also haema-
toxylin and methylene blue, are efficient staining re-agents

The hardening in formol-Miiller is especially suitable for bone
decalcified with phloroglucen and nitric acid. For naked-eye spe-
cimens formol-Miiller is also useful. Besides blood, fat, cartilage,
and bone are thus well differentiated, and pigments, colloid mate-
rial, etc., are also well fixed. Haemorrhagic nephritis, fatty
degeneration of the heart, etc., are well prepared by this method.
The colouring of the grey and white matter of the brain is very
satisfactory. Weaker alcohol (60 per cent.), to which formol (i per
cent.) has been added, is a good preservative fluid after formol-
Miiller ; also a combination of alcohol, glycerine, water, and
formol (i per cent.) may be employed. Embedding in gelatine, to
which I per cent, formol has been added, is successful. For the
preservation of tissues for demonstration i per cent, formol is very
useful. The specimens may be dipped in this solution, and then
wrapped in cloths soaked in it. Formol is very valuable as a dis-
infectant, particularly for washing the hands after a post-mortem
examination. The vapour is irritating, and therefore people should
not remain in a room where it is present for only a short time. —
Brit. Med. Journal.

Growth of Diatoms. —Mr. G. C. Whipple has carried on a
series of experiments on the culture of different kinds of diatoms,
and finds that an abundant food-supply is not the only condition
favourable for their rapid increase ; the temperature, the amount
of light, and other factors influencing their growth. In common
with all other chlorophyllaceous plants, diatoms will not grow in
the dark, while, on the other hand, bright sunlight also kills them.
The intensity of the light below the surface of the water being
affected by the colour of the water, diatoms are found most abun-
dantly in light-coloured water. Different genera, however, exhibit
differences in this respect. Melosira does not require so much
light as Synedra. The weather has a marked influence on the

International Journal of Microscopy and Natural Science.
Third Series. Vol. VII. o

190 MICROSCOPICAL TECHNIQUE,

growth of diatoms. They increase most rapidly during those
seasons of the year when the water is in circulation throughout the
vertical currents. During these periods not only is food most
abundant, but the vertical currents keep the diatoms near the sur-
face, where there is light enough to stimulate their growth, and
where there is abundance of air. Some species display strong
heliotropism, moving towards the source of light. — Pharm. Journ.

A New Method of Staining Nervous Tissue.— Vastarini-Cersi
(Rif. Med., Feb. 14, 1896) describes a new and effectual method
of staining the spinal cord, etc., for macroscopic purposes. The
entire cerebro-spinal axis, with the meninges, is plunged into about
3 litres of an aqueous solution of formaldehyde (16 per 1000).
The tissue is left in the medium for two weeks, the meninges
being removed on the second or third day. Sections from 3 to
5 cm. thick are then cut and kept in distilled water, or, better, in
alcohol at 40°, for twelve or twenty-four hours ; then plunged into
75'' solution of AqN03 i^^ the dark. The white substance soon
becomes stained brown. A prolonged stay in the Aq NO3 sol.
does no harm. The stain may be fixed for an indefinite time if
the preparation is left for two or three days in the dark in distilled
water and then in alcohol at 70"^. Tissue so prepared shows in
the clearest manner the relations between the white and the grey
substance. For example, in the medulla one could distinctly see
with the naked eye the respiratory fascicules of Krause. The
advantages claimed by the author for this method are its simplicity
and rapidity of execution, the constancy of the results, and its
great teaching value. — Brit. Med. Journ.

Differentiation of the B. coli from the B. typhi abdominalis.—

YX^Xi^x (Zeiisch. f. Hyg.^ysXl.) uses plates prepared with Holtz's
potato gelatine, to which, after it has been made slightly acid,
T per cent, of iodide of potash has been added. Even on this
unfavourable medium the B. coli grows freely and quickly, but no
colonies of the B. typhi abd. are visible for forty-eight hours, and
they appear as extremely fine, small, shining patches, like drops of
water. Controlling his experiments by Pfeiffer's immune-serum
process, Eisner always obtained positive results from typhoid stools.
Piorkowski, at the Berlin Medical Society (June 10, 1896), reported

NOTES. 191

experiments in cultivating these bacilli on agar, bouillon, and
gelatine mixed with urine, which had been suggested to him by
the presence of B. colt in the bladder. On these media the
microbe grew luxuriantly, forming greyish colonies ; the B. typhi
abd. less rapidly in fine transparent patches. In the discussion
Eisner said there were plenty of differential signs ; the difficulty
was to cultivate Eberth's bacillus when it was only present in small
number — for instance, in water, or mixed with other bacteria, for
example, in stools. Ewald, Wolf, and Senator, all had found
Eisner's method very useful for the diagnosis of doubtful cases
from the stools. — Brit. Med. Journ.

IRotee.

Helium. — From the results of the experiments recorded in
this paper, it seems that helium exists in the minerals in which it
is found in a condition comparable with that in which hydrogen is
associated with many metals, and carbonic oxide especially with
iron. Whether this condition is rightly distinguished from ordinary
chemical combination is a question which admits of debate. The
stability of all dissociable compounds is infiuenced by pressure and
by temperature in the same kind of way as " occlusion," which,
like ordinary chemical combination again, is a phenomenon in
which the bodies concerned exercise a power of selection.

The presence of hydrogen as well as carbon dioxide in granite,
if already observed, is not known to geologists generally. From
observation on variations in the critical point of carbon dioxide in
minerals (Journ. Chem. Soc.^ 1876, II., 248), Hartley seems to infer
that the incondensable gas present with carbon dioxide is usually
nitrogen. A passage in Geikie's Text-Book of Geologv, 3rd edit.,
p. no, refers to the presence of hydrogen in cavities; but no
information is given as to the evidence upon which this statement
is based. The presence of hydrogen in such a rock as granite
must be attributed to the existence of this gas in large proportion
in the atmosphere in which the rock was crystallised. Whether
this was the primeval atmosphere of the earth before the hydrogen
had escaped or had been oxidised into water, or whether it resulted

192 NOTES.

from the local action of water upon unoxidised metals or other
materials in the interior of the earth, is a question which may be
of some interest to the geologist. If the former hypothesis were
adopted, it would perhaps be difficult to explain the absence of
helium from the gas included in the rock ; and, on the whole, the
latter view appears to afford the more probable explanation.

Experiments show that hydrogen is present in even larger pro-
portion in the granite from the neighbourhood of Dublin, and it is
proposed to examine some other examples of the ancient crystal-
line rocks in order to determine the nature of the gases enclosed
in them. ^ * ^

The Wild Nettle is known to contain a remarkable number
of useful qualities. The leaf is an edible, and the liquid to be
obtained from the stalk makes an excellent beverage. The fibre
of the stalk may, under treatment, produce an excellent silk. For
ages the plant has been used for this purpose in China, where it
grows to a height of seven or eight feet. Only recently, however,
has the machinery necessary to make the manufacture of this silk
a profitable industry been produced. A machine called the
decorticator has been invented, by means of which the fibre is
stripped off in enormous quantities at a terrific speed. Ramie is
the eastern name of the plant. — The Counsellor.

* *
The Orange Groves of Naples are planted with wild trees,
which are grafted in the usual way and grow with bare trunks to
four or five feet from the ground. The branches then run out and
form the fruit-bearing portion of the tree. An ingenious and
beautiful innovation has been introduced in one grove, and is
described by Consul Neville-Rolfe in his latest report. Lemons
are grafted upon the bare and non-productive stems of the orange,
about two feet from the ground, and trained in garlands from tree
to tree, thus not only increasing the productiveness of the grove
very materially, but adding greatly to the picturesqueness of its
appearance. Orange trees being usually planted in rows at a
measured distance apart, a grove has usually a geometrical appear-
ance, which is unsatisfactory, but this appearance is very much
modified by the lemons, which break the lines in all directions.
There is a legend, which most people firmly believe, that the

NOTES. 193

grafting of a second fruit on the parent stem materially alters the

type and quality, not only of the original fruit, but also of the

graft, and it is sometimes gravely asserted that " blood oranges "

are obtained by grafting the pomegranate on to the orange. This,

says the consul^ is a complete fallacy. Both fruits retain their

original quality, and neither borrows anything from the other.

There is thus no difference between the lemons grown in the

orange grove from those grown in the grove where lemons alone

are cultivated. — Pharmaceutical Journal.

* ''' *
Prehistoric Human Teeth. — At a meeting of the Students'

Society of the National Dental Hospital, held October 9th, 1896,
Mr. Loftus H. Canton showed some interesting teeth which were
found in a cave at Seturitz, Basses Pyrenees. These teeth, sup-
posed to be those of the Cave Bear, were found in a bed of
guano, which was in some places thirty feet deep. Along with
them were large quantities of animal remains, and one curious
feature was that five specimens of human teeth were found in the
same place, together with human remains. Whether the human
remains were contemporary with those of the animals, Mr. Canton
could not say. The deep bed of guano was covered by a layer of
stalagmite, varying between one to five inches in thickness, and
above this another layer of guano was found, but not so deep as
the lower layer. Finally, at the top of all was another layer of
stalagmite. The fact of the remains being at such a great depth
seemed to imply that they were of great antiquity. — -Journ. British
Dental Association. * * *

Preservation of Flowers. — The following is a very old
method of keeping flowers without loss of colour : — Dry some
very fine, pure siliceous sand in the sun or oven ; then take a
wooden, tin-plate, or pasteboard box sufficiently large and deep,
and place your flowers inside erect ; then fill the box with sand
until the last is about an inch above the top of the flowers. The
sand must be run in gently so as not to break the flowers. Cover
the box with paper or perforated cardboard and place it in the sun-
light, oven, or stove; continuous heat gives the best results. After
two or three days the flowers will be very dry, but they will have
lost none of their natural brilliancy. — Journal oj Horticulture,

[ 194 ]

1Review6.

A Manual and Dictionary of Flowering Plants and Ferns.
In Two Vols. By J. C. Willis, M. A. Crown 8vo, pp. xiv. — 224 ; xiii. — 429.
(Cambridge: The University Press. 1897.) Price 10/6.

The aim of the author has been to prepare a book to supply, within a
reasonable compass, a summary of useful and scientific information about the
plants met with in a botanic garden, or museum, or in the field. He gives such
information as is required by any but specialists upon all plants usually met
with, and upon all those points — morphology, classification, natural history,
economic botany, etc. — which do not require the use of a microscope.

Vol. I. describes the Outlines of the Morphology, Natural History, Classi-
fication, Geographical Distribution, and Economic Uses of the Phanerogams
and Ferns ; and Vol. H. gives the Classes, Cohorts, Orders, and Chief Genera
of Phanerogams and Ferns alphabetically arranged under their Latin names.

The Botanist's Pocket-Book. By W. R. Hayward. 7th
edition, i2mo, pp. xxxvi. — 226. (London: G. Bell and Son. 1892.)

This very useful little book contains in a tabulated form the Chief Charac-
teristics of British Plants, with the botanical name, common name, soil or
situation, colour, growth, and time of flowering of every plant arranged under
its own order. There is also a good index, in which reference is given to the
volume and page of Sowerby's Botany, in which a much fuller description of
the plant will be found.

The Elements of Botany. By Francis Darwin, M.A., M.B.,
F. R.S., etc. etc. Cr. 8vo, pp. xvi. — 235. (Cambridge and London: The
University Press. 1896.) Price 4/6.

The fourteen chapters constituting this volume of the Cambridge Natural
Science Manuals give the substance of the Botanical Lectures delivered to the
Cambridge medical students ; whilst in an appendix is given the details of the
Practical work which accompanies the lectures. In these lectures the Bean,
Ranunculus, Silene, Chrysanthemum, etc., are used to illustrate floral struc-
ture ; Caltha for the ovule ; Helleborus for the leaf ; and the Pear, Gooseberry,
Sycamore, etc., for the fruit. In the same way Yeast and Spyrogyra are made
use of to illustrate nutrition and the general structure of plant-cells ; and
Mucor, Spyrogyra, and Pteris illustrate reproduction. There are nearly 100
good illustrations.

Practical Physiology of Plants. By Francis Darwin, M.A.,
F.L.S., and the late E. Hamilton Acton, M.A. Second edition. Cr. 8vo,
pp. XX. — 340, (Cambridge and London : The University Press. 1895.) 4/6.

This is another of the Cambridge Natural Science Manuals, and consists of
such a selection of experimental and analytical work as appears suitable for
botanical students. Part I. deals with General Physiology in a somewhat ele-
mentary manner ; Part II. treats a particular department of Physiology in a
more special manner, and pre-supposes a greater amount of knowledge on the
part of the student. There are 45 illustrations.

Maladies des Plantes Agricoles et des Arbres Fruiteres et
Forestiers causees par des Parasites V6getaux. Par Ed. Prillieux. Vol. I.,
8vo, pp. xvi. — 421. (Paris: Libraire de Firmin-Didcot and Co. 1895.)

This work is the outcome of the author's twenty years' study and teaching
of Economic Vegetable Pathology. He considers plant diseases to be due to
changes of normal physiological functions produced either by unfavourable con-
ditions or by the action of parasitic organisms penetrating the tissues. The

REVIEWS. • 195

author first treats of Bacteria and Myxomycetes, then of the various Fungi —
Phycomycetes, Ustilagineae, Urudineae, Basidiomycetes, and Ascomycetes. In
the introduction the author gives directions for using the microscope, and dis-
tributed throughout the text there are 190 good illustrations. We are informed
that the second volume will be published shortly.

Practical Notes on Grasses and Grass-Growing in East
Anglia. By William Spencer Everitt ; edited by Nicholas Everitt. Cr. 8vo,
pp. 154. (London: Jarrold and Sons. 1896.) Price 2/-

This book is written expressly for the Grass-grower, and contains many
valuable hints as to the kinds of grass to sow and what kinds of seeds should
be specially avoided. For those who do not know the various kinds of grasses
by sight, illustrations would have been a great acquisition. As it is, it will
doubtless prove of great assistance to the farmer.

La Photomicrographie, Histologique et Bacteriologique.
Par J. Choquet. Royal Svo, pp. vii.— 149. (Paris: Chas. Mendel, 118 Rue
d'Assas. 1897.)

In this fine work the author gives the results of many years' experience in
the delineation of histological subjects by means of photography, and very
carefully and fully describes the Cameras, Objectives, and Modes of Illumina-
tion suitable for this kind of work. A number of examples of Microphoto-
graphy are given, besides 72 engravings in the text, showing the various appa-
ratus. Without saying anything in disparagement of this work, we would
suggest to the author that he might find a better form of condenser than the
one he recommends on p. 64. The faint zone which he speaks of finding round
the images given even by apochromatic lenses would entirely disappear by using
from an achromatic substage condenser a cone of light of wider angle.

Microscopic Researches on the Formative Property of Gly-
cogen. Part I., Physiological. By Charles Creighton, M.D. Royal Svo, pp.
viii.— 152. (London : Adam and Charles Black. 1896.) Price 7/6 net.

Glycogen is that substance in the anim.al body which corresponds very
closely with the starch of plants and its appearance in the cells of different tissues
during development. The bookisillustrated by five well-executed coloured plates.
Chapter I. is an Historical Introduction ; II. treats of Methods and Material—
viz.. Microscopic Method, method of using iodine, preservation of sections,
colour of the iodide of animal starch, and reaction with methyl violet. The
remaining eleven chapters treat of glycogen as found in various parts of the
animal body.

Microscopic Internal Flaws inducing Fracture in Steel. By
Thomas Andrews, F.R.S., F.C.S., M.Inst.C.E., etc. Svo, pp. 52. (London:
E. and F. N. Spon. 1S96.)

A paper of considerable importance to Civil Engineers (reprinted from
Engineering) on Microscopic Internal Flaws in Steel, Railway Locomotive and
Straight Axles, Tyres, Rails, Steamship Propeller Shafts, and Propeller Crane
Shafts, and other Shafts, Bridge Girder Plates, Ship Plates, and other_ Engin-
eering Constructions of Steel. There are 30 micro, figures showing internal
flaws.

Pioneers of Evolution from Thrales to Huxley, with an
intermediate chapter on the Causes of Arrest of the Movement. By Edward
Clodd. Cr. Svo, pp. xii. — 250. (London: Grant Richards. 1897.)

The author here attempts to tell the story of the origin of the Evolution
idea in Ionia, and, after long arrest, of the revival of that idea in modern times,
when its profound and permanent influence on thought in all directions, and,
therefore, on human relations and conduct is apparent. The book is divided

196 REVIEWS.

into four parts, and treats of — I. . Pioneers of Evolution from Thrales to Lucre-
tius, B.C. 600 — A.D. 50; II., The Arrest of Enquiry, a.d. 50 — 1600 ; III.,
The Renascence of Science, a.d. 1600 onwards ; IV., Modern Evolutionists :
I, Darwin and Wallace ; 2, Herbert Spencer ; 3, Thomas Henry Huxley. A
portrait of C. Darwin forms the frontispiece to the volume.

A Study of the Sky. By Herbert A. Howe, Professor of
Astronomy, University of Denver (U.S.A.). 8vo, pp. 340. (London : Mac-
millan and Co. 1897.) Price 6/-

This is a thoroughly interesting book. The story is told with plainness and
simplicity. The standpoint adopted is that of the astronomer, who observes,
records what he sees, studies his observations, digs out the truths which they
contain, and weaves them into laws and theories which embrace the visible
universe, reaching from unknoM'n depths of past ages up to unmeasured heights
of futurity. An explanation of the apparent daily motion of the heavens is
given and the chief constellations are set forth in detail. The book contains
144 good illustrations, many of them full-page.

The Natural History of Marketable Marine Fishes of the
British Islands. By J. T. Cunningham, M.A.Oxon. ; with a Preface by E.
Ray Lancaster, M.A. , LL.D., F.R.S. Royal 8vo, pp. xvi.— 375. (London:
Macmillan and Co. 1896.) Price 7/6.

Mr. Cunningham has for many years occupied the position of naturalist at
the Plymouth laboratory, being specially charged by the Council with the
investigation of the structure, habits, and breeding of marine food-fishes, and
his book will undoubtedly serve as a help, not only to trained investigators, but
to those who are able to give some portion of their leisure to this important
subject. There are 159 illustrations and 2 coloured maps, one showing the
fishing-grounds of the British Islands ; the other the West Coast of Europe.

The Natural History of the Year for Young People. By

J. Arthur Thomson. Cr. 8vo, pp. 288. (London : A. Melrose.) Price 3/6.

In this interesting little book the author tells us in plain words some of the
great moves in the march of the seasons. The book is divided into four sec-
tions, one for each season of the year, beginning with Spring. Each of these is
subdivided into five chapters. Most of them have appeared in the pages of
You7ig England, but those of our young friends who read them there will do
well to read them again ; they cannot fail to interest and instruct. The book is
nicely illustrated.

Object Lessons in Natural History. By Edward Snel-
grove, B.A. Cr. 8vo, pp. 214. (London: Jarrold and Sons. 1897.) 3/6.

This capital little book is divided into 46 lessons ; and provides a com-
plete course in Elementary Science for the three Junior Standards of Element-
ary Schools, so far as Natural History is concerned. There is undoubtedly a
decided advantage in placing together related subjects, so that threads of con-
nection are clearly seen and firmly grasped, and this, we think, is fully carried
out in the book before us. The illustrations, which are mostly in outline, will
be found to convey their meaning very clearly, and we thoroughly approve of
the style of reasoning adopted as being likely to convey to the mind of the
child all that is required for it to know.

Footprints of the Lion and other Stories of Travel in Dal-
matia, Montenegro, the Mediterranean, India, and Siam. By Major-General
J. Blaksley. Second edition, enlarged. 8vo, pp. 115. (London: W. H.
Allen and Co. 1897.)

This is a most interesting, handsomely got up, and beautifully illustrated

REVIEWS. 197

book. The first story (" Footprints of the Lion ") is a description of a most
deHghtful trip, which will most probably induce other English people to visit
these interesting remains of what formerly was subject to the Queen of the
Adriatic in her splendour. There are 33 full-page illustrations from photographs.

A Handbook of Game-Birds. By W. R. Ogilvie-Grant.
Vol. 11. Cr. 8vo, pp. XV.— 316. (London: W. H. Allen and Co. 1897.) 6/-

In this volume of Allen's Naturalist'' s Library the Pheasants is concluded.
It contains also Megapodes, Curassons, Hoatzins, and Bustard Quails. This
volume and Volume I. contain the names of every species of Game-Bird
known up to the present date, so that they may be considered in the light of a
small Monograph of the Gallincs. There are 18 good coloured plates.

A Handbook to the Order Lepidoptera. By W. F.
Kirby, F.L.S., F.Ent.S., etc. Vol. III. Cr. 8vo, pp. xxvii. — 308. (London:
W. H. Allen and Co. 1897.) Price 6/-

In this volume the Butterfly (Hesperiidas) section is concluded, and is fol-
lowed by twenty-six families of Aloths, particular attention having been paid to
species inhabiting the British Isles ; whilst at the same time exotic species have
been passed in review, illustrations of the principal families and of some of the
most interesting genera of the exotic forms have been given. There are 37
well-executed and beautifully-coloured plates.

A Dictionary of Birds. By Alfred Newton and Hans
Gadon. Part IV. (Sheathbill — Zygodactyli), together with Index and Intro-
duction. (London: A. and C. Black. 1896.) Price 7/6 net.

The part now before us completes this important volume, which was com-
menced in 1893. The entire work has been carried through in a most thorough
and painstaking manner. It contains an exhaustive index of 30 three-column
pages, and an Introduction of 124 pages, with an index. The work is well
illustrated throughout.

The Story of Forest and Stream. By James Rodway,
F.L.S. pp. 202.

The Story of the Chemical Elements. By M. M. Patti-

son Muir, M.A. pp. 189.

The Story of the Weather, Simply told for General
Readers. By George F. Chambers, F.R.A.S. pp. 232.

(London: Geo. Newnes, Ltd. 1897. Price i/- each.)

It will be remembered that in an earlier volume of this series was pub-
lished "The Story of the Plants," by Grant Allen. In the first of the vols,
before us, the author gives some additional sketches on the life of the trees in
wood, in forest ; and as water is so necessary to their well-being, because without
it there would be no forests, he has coupled the trees with the rivers. There
are 26 good illustrations.

In the second of these little books the author gives in orderly sequence a
few of the chief guiding conceptions of chemistry, avoiding as far as possible
technical details, and illustrating these conceptions by describing many
common facts.

"The Story of the Weather" is a subject in which all are more or less
interested. It tells us many things about the weather, and presents in a handy
form, and in unconventional style of language, a certain number of elementary
facts, ideas, and suggestions which ordinary people, laying no claim to scientific
attainments generally, are usually glad to know. It is nicely illustrated.

198 ^ REVIEWS.

Science Progress : A Quarterly Review of Current Scientific
Investigation. New Series. Vol. I., No. 2. January, 1897. (London: The
Scientific Press.) Price 3/-, or 10/6 per annum post free.

The January part of this Journal contains the following articles : — Liquid
Crystals, by H. A. Miers, F.R.S. ; Sugar — The Outlook in the Colonies, by
C. A. Barber, M.A. ; The Cell and some of its Constituent Structures, by J.
Bretland Farmer, M.A. ; Selection in Man, by John Beddoe, F.R.S. ; The
Glossopteris Flora, by A. C. Seward, M.A. ; Condensation and Critical Pheno-
mena, by J. P. Kuenen, Ph.D. ; The Origin of Lakes, by J. E. Marr, F.R.S. ;
The Causes of Variation, by H. M, Vernon, M.A., M.B. ; and in the Appen-
dix, Notices of Books.

The Zoologist : A Monthly Journal of Natural History.
Fourth series. Vol, I., No. i. (London: West, Newman, and Co.) i/-

The fourth series of this well-known Journal commences under a new
editor. It contains an editorial address, and papers on Recent Additions to
the British Avifauna ; On the Occurrence of the Pallas Willow Warbler in
Norfolk ; Man in Zoology ; Notes from Norway ; Notes on the Chacma
Baboon ; and Notes and Queries, etc.

A New English Dictionary on Historical Principles, founded

mainly on the Materials collected by the Philological Society. Edited by
Dr. James A. H. Murray. Disobst — Distrustful. (Oxford and London :
The Clarendon Press. ) Price 2/6.

This section contains 1222 main words, 30 combinations explained under
these, and 94 subordinate entries, making 1346 in all. Of the main words,
845 are current and native or fully naturalised, 365 (or about 30 per cent.) are
marked as obsolete, and only 12 are marked as alien or not fully naturalised. In
this part 1242 words are illustrated by 7316 quotations. It is indeed an
exhaustive and masterly work.

Bryce's Diamond English Dictionary. (Glasgow : David
Bryce and Son. 1896.)

Messrs. Bryce and Son have favoured us with one of their curious little
books. Its size is only i^ by I J by ^ in. , and consists of 860 pages of very
legible type, no magnifying glass being required. This dictionary comprises,
besides the ordinary and newest words in the language, short explanations of a
great number of scientific, philosophical, literary, and technical terms ; it is
nicely bound in leather and has gilt edges.

The Swiftograph Instructor. Price 2/-

The Swiftograph Reader. Price i/- (London : Jarrold
and Sons.)

These two books reached us at the moment of going to press. We shall,
therefore, hold over any remarks on them until we have had more time in
which thoroughly to examine the system. At present we confine ourselves to
quoting the assertion of the author that it is " The Simplest System of Short-
hand-writing in the World. Learned in an hour.''^

Introduction to the Study of Chemistry. By W. H.
Perkins, jun., Ph.D., F.R.S., and Bevan Lean, D.Sc, B.A. Lond. Cr. 8vo,
pp. x. — 339. (London: Macmillan and Co. 1896.)

The authors commence with a reference to alchemy and to some of the
errors which were current until the 17th century, showing the readiness with
which errors arose unless checked by well-devised experiment and careful
measurement. Measurements are made of length, of mass, of the volume

REVIEWS, X99

of liquids, of temperature, of density, of pressure, and of heat. This is
followed by the practice of important chemical operations, as solution, filtra-
tion, evaporation, etc. There are 136 illustrations in the text.

First Stage Inorganic Chemistry. By G. H. Baile},
D.Sc.Lond., Ph. D.Heidelberg; edited byW. Briggs, M.A., F.C.S., F.R. A.S.,
etc. Cr. 8vo, pp. viii. — 210. (London: W. B. Clive.) Price 2/-

This book will be found to be a useful companion in the laboratory. The
figures of apparatus are only given where some aid was thought to be necessary
in their arrangement or fitting. In the earlier chapters instructions are given
with respect to the methods to be employed by the chemist in conducting his
enquiries. The entire work has been arranged to meet the requirements of the
Science and Art Department for the Elementary stage, whilst some of the
subjects have been more fully treated.

The Medical Annual and Practitioner's Index : A Work
of Reference for Medical Practitioners. Cr. 8vo, pp. xxvi. — 722. (Bristol :
John Wright and Co. London: Simpkin, Marshall, and Co. 1897.) 7/6.

This important work, now in its fifteenth year, represents the united efforts
of forty contributors residing on the Continent of Europe, in our Colonies, and
the U.S. of America. Amongst other articles we notice a valuable paper on
Leprosy by Dr. G. Armauer Hansen, of Norway ; one on Oriental Diseases by
Mr. Canthe, who has lately returned from the East. The Dictionary of New
Remedies and Review of Therapeutic Progress for 1896 occupies 90 pages ;
whilst the Dictionary of New Treatment in Medicine and Surgery covers more
than 500. There are 27 plates, many of them coloured, and 113 wood
engravings.

Herbal Simples approved for Modern Uses of Cure. By
W. T, Fernie, M.D. Second edition. Cr. 8vo, pp. xxiii.— 651. (Bristol:
John Wright & Co. London : Simpkin, Marshall, & Co. 1897.) Price 6/-

From primitive times the term "Herbal Simple " has been applied to any
homely curative remedy consisting of one ingredient only, and that of a vege-
table nature. Many such a native medicine found favour and success with our
single-minded forefathers. In this second and greatly enlarged edition much
new matter has been added.

Chemical Recipes. By the Atlas Chemical Co., Sunderland.
Third edition. Cr. 8vo, pp. xviii. — 379. (Sunderland: Hills and Co., 19
Fawcett St. 1896.)

This book contains one thousand modern formulae for producing all kinds
of colours and other chemical compositions, with full explanatory notes and
instructions for manufacture, etc. That the recipes herein given have been
found useful may be judged from the fact that the first and second editions
were entirely sold out within one year.

Advanced Mechanics. Vol. II., Statics. By William
Briggs, M.A., F.C.S., F.R.A.S., and G. H. Bryan, Sc.D., F.R.S., etc. Cr.
8vo, pp. viii.— 288. (London: W. B. Clive.) Price 3/6.

This volume of the " Organised Science Series" is the Tutorial Statics,
together with the Questions of the last eleven years set at the advanced exami-
nation of the Science and Art Department. It includes those portions of
Statics which are contained in the syllabus of the Science and Art Second
(Advanced) Stage Examination in Theoretical Mechanics. The Principle of
Work is freely employed throughout the book, and all the important bookwork
is printed in larger type than the hints, explanations, examples, etc. At the

200 REVIEWS.

end of the book will be found all the Questions, both on Statics and Dynamics,
that have been set in the Science and Art Second Stage Examination during
the past eleven years.

Brush Drawing, Adapted to Meet the Requirements of the
Education Code, and the Alternative Drawing Syllabus of the Science and Art
Department. By J. Vaughan. 410. (London : Moffatt & Paige. 1896.) 3/-

This is one of the series of " Hand and Eye Training " books, which aim
at developing three distinct and important faculties, viz. : — Dexterity of hand ;
appreciation of line, form, colour, and space ; and accurate observation. There
are 24 coloured plates of design, with full instructions and other descriptive
letterpress.

The Tutorial Latin Reader. Second edition. Cr. 8vo,
pp. viii. — 167 -t- 48. (London: W. B. Clive.) Price 2/6.

This contains a Graduated Series of Extracts for Practice in Translation at
sight, with an Appendix of Passages set at the London University Matricula-
tion and Intermediate Arts Examinations. The book is divided into Short
Sentences ; Short Sentences followed by the original passages from which the
sentences have been formed ; Prose Passages, so printed that each clause begins
a new line ; Easy Passages of prose and verse ; and Harder Passages. The
entire scheme of the book appears an admirable one.

An Elementary Text-Book of Hydrostatics. By William
Briggs, M.A., LL.M., F.C.S., F.R.A.S., and G. H. Bryan, Sc.D., M.A.,
F.R.S. Second edition. Cr. 8vo, pp. viii. — 208. (London: W. Clive.) 3/6.

The ground covered by this volume of the " University Tutorial Seiies "
includes those portions of Hydrostatics and Pneumatics which are usually read
by beginners and by candidates for examinations of a standard such as that of
the London Matriculation.

Shakespeare's History of the Life and Death of King

John. Fscap. 4to, pp. 190. (Cambridge : The University Correspondence
College Press. 1895.) Price 2/-

The Introduction to this volume gives the History of the Play, the Sources
of the Plot, and Critical Comments on the Play, and at the end are voluminous
notes.

Selections from Malory's Le Morte d'Arthur. Edited,

with Introduction, Notes, and Glossary, by A. T. Martin, M.A., F.S.A. Cr.
Svo, pp. xxxvi. — 254. (London: Macmillan and Co. 1896.)

Mr. Martin has given us here the Arthurian Legend in a concise and read-
able form. The student will find much to interest him in the Notes on Malory's
Grammar. General Notes, Appendix on the Various Versions of the Legend of
the Holy Grail, etc., are found towards the end of the book.

Is Natural Selection the Creator of Species ? By Duncan
Graham. Cr. 8vo, pp. xviii. — 303. (London: Digby, Long and Co.) 6/-

The author is evidently a man of very strong views and opinions ; he
maintains that the condition of the earth and its inhabitants cannot be explained
by the action of physical forces independent of support and direction from an
intelligent power. . . . Natural selection is a delusion ; being only a result^
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201

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202 REVIEWS.

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204 REVIEWS.

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[ 205 ]

By C. D. Soar. Part IX. Plates XII. and

LL the species of Hydrachnidce which have been
mentioned in my former papers belong to the
sub-faraily Lateroculat^. The two acarids which
will form the subject of this paper belong to the
sub-family MEDiocuLAXiE (Haller), which contains
two genera only : — Limnocharis and Eylais. Mr.
Michael, in his British Oribatidce, page 50, gives a
key to the families of the Acarina, in which he
includes the Halicarince with the Lim7iocaridce^ and
on page 49 he says : — " I have some doubt about my own cor-
rectness in including the Halicaridce among the Limnocaridce ; but
I think on the whole that they are fairly placed together."

Now the Halicaridce are Marine mites, or are generally looked
upon as such, but I believe several species are found in fresh
water. Anyone interested in this family will find a lot of informa-
tion in a small book by Hans Lohmann, Jena, 1888 — Die Unter-
fa77iilieder Halacarides Micrr^ which has at the end a Bibliography of
sixty-one papers on the subject. At present I have nothing to say
about Marine mites, so I will confine the few^ remarks I have to
make to the two genera above mentioned — Linmocharis and Eylais.
Each of these two genera, I believe, are up to the present date
only repres^ted by one species each. The distinguishing features
of these are so great that they cannot, when once known, be mis-
taken one for the other, or for any other species of another genus.
Both have their eyes near the centre line of the body. Both are
red and both attain a large size. In both, also, the mouth organs
are modified into a sucker-like tube, but here the similarity ends,
for one is a swimming mite and the other is a crawler.

Genus X. — Eylais^ Latreille.

1796. — Eylais, Latreille. Precis des Caracthes des Insectes, p. 182.

Body, oval ; eyes, approximated to the median line of the

body ; the fourth pair of legs without swimming-hairs.

iNTERNArioxAL Journal of Microscopy and Natural Science.
Third Series. Vol. VII. p

206 BRITISH HYDRACHNID^.

It will be seen from the above that the genus we are now about
to consider varies very much from those we have previously men-
tioned. All of the previously noticed Hydrachnids have swim-
ming-hairs to the second, third, and fourth pair of legs, and in some
cases to the first ; but in the genus Eylais the fourth pair are des-
titute of swimming-hairs, which to a swimming mite would appear
to be a very desirable and necessary addition. The fourth pair of
legs are strong and very hairy, but are quite without those long
hairs we have before noticed. The eyes are also placed very near
each other, and not wide apart like the eyes in other Hydrachnids.
There is only one other Hydrachnid having the eyes in a central
position, and that is the Linmocharis mentioned above.

Up to the present I believe only one species is known of this

genus, and that is

Eylais extendens (Miill.).

Bibliography : —
1776. — Hydrachna extendens. Miiller, Zool. Dan. Prodr., p. 190,

No. 2272.
1 78 1. — Hydrachna extendens. Miiller, HydrachncB^ p. 62, Tab.

IX., Fig. 4.
1793. — Trombidnwi extendens. J. C. Fabricius, Ent. Syst., Tom.

II., p. 406; p. 24.
1796. — Eylais extendens. Latreille, Precis des Caracthes des

Insectes^ p. 182.
1805. — Atax extendens. J. C. Fabricius, Syst. Antliatorum^ p. 372.
1834. — Eylais exte?idens. Duges, " Remarques sur la famille des

Hydrachnes," in Annates des Sciences Nat., Seconde Serie,

Tom. I, p. 156.
1835-41. — Eylais extetidens. C. L. Koch, Deutschlands Crust. ^

etc., p. 14, Figs. 21 and 22.

Also Eylais alutacea, p. 14, Fig. 20.

Also Eylais longi?na7ia, p. 14, Fig. 23.

Also Eylais atoviaria, p. 14, Fig. 19.

Also Eylais conjinis, p. 14, Fig. 18.
1854. — Eylais extendens. Bruzelius, Beskr. 0. HydracJmides, som,

Forek. inom Skdne, p. 52, Tab. 5, Figs. 5 — 10.
1876. — Eylais extendens. Kramer, Beitr. zur. Naturgesch. der

Hydrach., p. 313, Taf. IX., Fig. 22.

BRITISH HYDRACHNID^.

207

1878. — Rylais e.xte?idens. A. Croneberg, Zool. A?iz., 1878, No. 14,

p. 316,
1878. — Eylais extendens. Krendowsky, Die Metajnorphose Hydrach-

fiiden, p. 8, PI. I., Figs, i and 2.
1879, — Eylais exiendens. Neiiman, Svenska Hand/ingar, p. 105,

Twf. XIII., Fig. 4.
1880. — Eylais exte?ide?is. Murray, Economic Entomology, p. 150,

Fig. 2.
1882. -Eylais extendens. Haller, Die Hydrach. der ScJmeiz,,

p. 37, Taf. II, Figs. 9 — 13.
\%%l.--Eylais extendens. Griffith and Henfrey, Micro. Dictionary,

p. 315, PI- VI., Fig. 28.
1885. — Eylais extendefis. Krendowsky, HydrachnidcE of Russia,

p. 143, Taf. VIII., Fig. 23.
1887. — Eylais extendens. Barrois and Moniez, Cat. des Hydraclr

nids Nord de la France, p. 36.
\^(^}^.— Eylais extendens. Koenike, Dr. F., Stuhlman in Ostafrika,

P- 51-
1894. — Eylais extendens. Piersig., Zool Anz., No. 449, p. 215.
1895. — Eylais exfe7ide?is. Koenike, Die Hydrachniden Ort-

Afrikas, p. 2.
1896. — Eylais extefidejis. Soar, Sci. Goss., Dec, No. 31, p. 170.

The average length of the body is about 4*0 mm. ; width, about
3*12 mm. ; first leg about 2-40 mm. ; second leg about 2*50 mm. ;
third leg, 3*04 mm.; and the fourth leg, 3-60 mm. ; palpi, r2o mm.

Shape of body ovate, the smallest end to the front. The
dorsal side is well rounded (see PI. XII., Fig. i). The epimera
are hard, chitinous plates let into the ventral surface, the two first
pairs being joined together side by side ; the two last pairs touch
only at the small ends, the marginal ends where the legs are
hinged being wide apart (see Fig. 2). The largest ends of the
epimeral plates are also furnished with a quantity of small hairs ; a
few are also present here and there to about half-way down the
epimera plates.

Legs, eight, four on each side, which gradually increase in
length from before backward ; they are strong and chitinous, and
covered with small hairs, the first, second, and third pairs being
supplied with swimming-hairs only. The fourth pair, although

208 BRITISH HYDRACHNIDiE.

without the swimming-hairs, are nevertheless well covered with
short hairs, which on the inner edge of the legs are arranged in a
line and are stiffer in form than the others. The tarsus is thinner
than the other sections of the leg and not quite so long as the
preceding internode. The ungues are very small and nearly
hidden in the bristles which grow on the extreme end of the tarsi
(see Fig. 3). The palpus is five-jointed, the second and third
internodes being short and thick, the fourth is longer and more
slender ; like the legs, the palpi are covered with minute hairs.

Colour, scarlet, some being found deeper in colour than others.
Some appear to be very deep in colour in the central portion of
the dorsal side and the margin to be much paler. The legs are
paler in colour than the body and are inclined to yellow at the
joints.

Texture. — With the exception of the epimeral plates the whole
surface of the body is soft-skinned. The cuticle appears to be
finely striated and not covered with papillae. I cannot find any
external difference to denote the sexes.

Eyes, four, in two pairs, close together. They have the appear-
ance of being connected on the dorsal surface with a small band of
cliitine, like a pair of spectacles ; in colour they are very dark red.

The mouth-organs are very curious. In place of the mandibles,
which project and, as a rule, are so conspicuous in other species of
water-mites, is a round, sucker-like hole or depression (see Fig. 2).

Distribution. — Very common. I have taken specimens at
nearly all the collecting-grounds round London. The greatest
number of specimens I have taken in one day was at the Warren,
Folkestone, in Aug., 1896.

Larva. — Long in shape and hexapod. On Aug. 26, 1896, I
put a few Eylais extende?is in a tube by themselves. On Aug. 28
a quantity of ova was deposited on the side of the tube of a deep
red colour, in a yellow, gelatinous-looking film. On Oct. 2 the
larvae left this gelatinous mass and were free-swimming. They are
a deep red colour, like the adults, and seemed to be quite as much
at home out of the water as in ; but they did not display that
eagerness to get out of it that I found with the larvae of DipIodo7i-
tus despiciens (Miill.). They are very highly cultured, and the
hairs on the legs are quite clear, not pectinated. Eyes wide apart,

13RITISH HYDRACHNIDiE. 209

not close together like the adult. The length of the larva is about
0*48 mm. The form of the nymph is very much that of the adult,
only smaller.

The adults vary very much in size, but I have endeavoured to
give a mean measure. To arrive at this I have measured about
forty specimens. Neuman says the average size is 4 to 5 mm. I
have described their usual shape as egg-shaped or ovoid, but I
have taken two or three specimens which were quite unelliptical in
shape, like Koch's figure of Eylais confinis. It may have been
this shape which led Koch to think he had found another species.
Koch's other figures of Eylais appear to be the common shape.
So are the figures of Miiller, Duge, Neuman, and the little figure
in the Micro. Dictionary.

In 1885, when Science Gossip published those beautifully
coloured plates, afterwards discontinued on account of the cost,
there appeared a plate by E. T. Draper in January over the name
of Eylais extendefis^ which, it will perhaps be as well to point out,
is not an Eylais, but one of the Limncsia. Dr. George, of Kirton-
in-Lindsey, pointed this out at the time to the Quekett Club, but
I do not think the error was ever corrected in Science Gossip. It
is a swift and powerful swimmer and easily kept in confinement.
I have kept a great number alive in tubes for weeks at the time.

The majority of the references given are merely records of this
particular Hydrachnid, having been found at such a place and at
such and such a time ; but others are particularly interesting, and
should be seen and read by the student in this particular branch
of pond life.

Genus XL — Limnocharis (Latreille). 1796.

(Latreille, Precis des Caractlres des hisectes, p. 181.)

All legs without swimming-hairs ; eyes approximated to median

line of body. Body soft and varied in shape.

Limnocharis holosericea (Latreille).

Bibliography : —

1755. — Roesel., Insektenbelustigunge?i, III., p. 25.

1758. — Acariis aqiiaticus. Linne, Fauna Suecica, ed. 2, sp. 1978.

1778. — De Geer, Metnoires poicr Vhistoire des Insectes, VII., p. 149

—152, PI. IX., Figs. 15—18.

210 BRITISH HYDRACHNID^.

1796. — Lwmocharis holosericea, Latreille, Genera Crust, a Insect.^

I., p. 160.
1804. — Trombidium aqiiaticum. Hermann, Memoire Apterolo-

giqiic^ P- 35. PI- 1-5 Fig. II.
1834. — Limuocharis aquaticus, Duges Deux, Mem. sur Vordre
das Acariens Ann. d. %c. Nat., T. 11, p. 159, PL XL,

Figs. 35—39-
1835-41. — Lwmocharis holosericea, C. L. Koch, Deutsch. Crust.

Arachn., etc., H. 14, PL XXIV.
1S42. — Liinnocharis holosericea. Koch, Ubersicht, p. 35, Tab. IV.,

Fig. 19.
\%%o.~—Limnocharis aquaticus. Murray, Economic Ent.^ \). 148.
1 882. — LimnocJiaris holosericea. Haller, Die Hydrach. der Schweiz..,

P- 34-
1883. — Litnnocharis holosericea. Griffith and Henfrey, Micro. Die,

p. 471, PL VI., Fig. 27.
1885. — Limfiocharis aquatica. Krendowsky, Hydrachfiidce of

Russia, p. 138, Twb. VIII., Figs. 24 — 28.
1887. — Limnocharis holosericea. Barrois and Moniez, Catalogue

des Hydra., p. 36.
1896. — Limnocharis holosericea. KoenikC;, Forschungsberichte Bio-

logischen Station zu Plan.
1896. — Linmocharis holosericea. Soar, Science Gossip, Dec, No. 31,

p. 170.

The mean measurements of body are :— Length about 3*0 mm.,
width about 2 mm. ; legs: — First leg, about 1*20 mm. ; second leg,
about 1-40 mm. ; third leg, i-6o mm. ; fourth leg, about 1-76 mm.

Colour.— '^QdixXtt. The legs are inclined to yellow at the
joints, but the same colour as the body at the other parts.

Form. — I can liken the shape of the body to nothing better
than a miniature sack, or bag, of the softest material, and w^hen
the mouth-organs are thrust forward the resemblance to the bag is
much more striking, it having the appearance of being tied round
the to[) with a string. It is also full of folds, which are constantly
changing their position as the little creature moves.

Texture.— ThQ cuticle of the body is very soft, and covered
with small round papillae.

BRITISH HYDRACHNID.E. 211

Legs. — In the adult the usual number, eight. These legs have
six joints. The first joint is small and almost hidden under the
epimera. The other five sections of the same leg are nearly of
one length. They are covered with a great number of simple
hairs. A few of those on the joints are plumose, but are quite
without the long swimming-hairs described before. Each tarsi is
fitted with two strong claws, which can be retracted at will into
the distal end of the tarsus. The first pair of legs are the shortest.

The epimera is chitinous, with a border of a thicker skin round
each epimeral plate, which is fringed with a quantity of fine hairs.

Eyes, four. On the anterior portion of the dorsal surface is an
oblong-shaped piece of chitine, which projects on each side towards
the larger end, and it is on the margin of these two projections the
eyes are situated (see Fig. 8).

The mouth-organs are suctorial. The palpus is short, and
reaches no further than the sucker-like mouth. It has hairs at the
joints (see Fig. lo).

Distribution. — It is not common. I took two specimens in
1893 — one at Woking and one at Sunningdale. In 1894 I took
two specimens at The Warren, Folkestone, and one at Redhill.
In 1895 I did not take a single specimen. In 1896 I took six
specimens at The Warren, Folkestone, and on Sept. the 8th two
in North Wales. These last two I have still alive. Seven months
since they were captured. I believe both to be females, but they
have not deposited any ova.

Larva and nymph I do not know. The adults are very slug-
gish in their movements, and keep well at the bottom of the water,
slowly crawling about amongst the debris,

Linneus had priority in naming this mite, and he gave it the
specific name of Aquaticus, and this name was retained by some of
the writers that came after him, as will be seen in the bibliography.
I also think myself that the name Aquaticus should be kept for
that reason. I do not like the alteration of specific names, for
the practice leads as a rule to much confusion ; but when we get
two such well-known writers on the Hydrachnidce as Koenike and
Piersig — both of whom call it holosericea after Latreille — I must
submit to their ruling and say no more on that question.

212 METHOD OF STxVININO FLAGELLA.

EXPLANATION OF PLATES XIL a^d XIIL

Fig. 1. — Eylais extendens. Dorsal surface.

,,2. ,, ,, Epimera and mouth-organs.

,,3. ,, ,, First leg.

„ 4. ,, ,, Dorsal surface of larva, legs removed.

,, 5. ,, ,, Last joints of the first leg, showing the

peculiar claw.
„ 0. — Limnocharis holosericea Dorsal surface.
,,7. ,, ,, Ventral surface.

,,8. ,, ,, Eyes.

„ 9. ,, ,, First leg.

,, 10. ,, „ Mouth-organs and palpus.

,, 11. — Eylais extendens. Appearance of the ova as deposited on the
side of the tube.

H flDctbo5 of Staining flagclla-

By David McCrorie, L.R.C.P. and S. Edin., F.E.I.S., etc.*

OF the different methods of staining flagella which have at
different times been described, Van Ermengen's, in my
experience, gives excellent results, but takes too long to
accomplish ; while Loeffler's, as well as NicoUe and Morax's modi-
fication of the same, is very uncertain. Pitfield's method gives
good results, and is quickly accomplished, but the flagella are, as
as a rule, very faintly stained. The method which is now com-
monly adopted in this laboratory is somewhat similar to Pitfield's,
but we use a different stain, and invariably we get both bacilli and
flagella more distinctly stained than by Pitfield's method. The
dye we use is an aniline blue, which is known commonly as "Night
Blue," from the fact that it shows as well in artificial as it does in
sunlight. The formula which we find to give the best results is —

lo c.cm. of a concentrated alcoholic solution of " night blue."
-j-io c.cm. of a lo per cent, solution of alum.
-}-io c.cm. of a lo per cent, solution of tannic acid.

* From British Medical Journal.

Journal of Microscopy, 3"^ Ser.Vol. G, Plate 12

as dsp(7si^d^tP77y

s^dc of hi-ie-.

Fig. 4

IJi/la^s e^ii^^ndens.

C'^ lis. £. Scar .^d na/: (^t/.

F. F/?///^p^ So.

Journal of Microscopy 3"^^ Ser.Vol. 6, Plate, 13

Fig. 7.

Fi^. 10.

METHOD OF STAINING FLAGELLA. 213

The addition of o"i to 0*2 g. of gallic acid would seem to add
to the value of this mordant stain, but excellent results can be
obtained without this addition.

The method we adopt is this : — A drop of sterilised water is
placed on an absolutely clean cover-glass, held in a Cornet's clip,
and carefully inoculated with the smallest quantity of a twenty-four-
hours' agar culture. The cover-glass is moved in such a way that
the drop of water is distributed over nearly its whole surface, or a
suspension may be made in a watch-glass and a thin film spread
upon a cover-glass. It is then placed in the incubator until
thoroughly dried (two minutes). A small quantity of the mordant
stain is then poured on, and the cover-glass again placed in the
incubator for two minutes, or held for that time two feet above the
flame of a Bunsen burner. The excess of stam is now washed off
by running water, the cover-glass dried in the incubator, and then
mounted in Canada balsam. The mordant stain can be used
either filtered or unfiltered ; it does not necessarily require to be
made fresh each time, as we find that the stain is quite as efficient
after a fortnight or so as on the first day of use. The whole
process can be accomplished in a few minutes.

Poisoning by Caterpillars. — Girard, a veterinary surgeon, at
Barnewet, has observed numerous fatal cases of poisoning in ducks
after eating caterpillars, notably those of Pieris brassicce, the large
white cabbage butterfly. About six hours after eating these larvae,
poisoning became evident, diarrhoea and staggering grit, followed
by dyspnoea, and ultimately death. x\utopsy showed the essential
lesions to indicate inflammation of the digestive tube. It is pro-
bable that these symptoms are caused by the inflammation pro-
duced in the alimentary canal by the very minute hairs with which
this caterpillar is covered. It has been noticed that chickens
invariably refuse the larva of F. brassicce, although they greedily
devoured the smooth larvae of the various Noctua. — Phar. Jour^

'i^^^

li'lLIBRARY

[ 214 ]

Saturn.

By H. J. TOWNSHEND.

SATURN, during the months of May and June, 1896, pre-
sented the appearance of a dull, yellowish, first magnitude,
starlike object in our southern heavens, in a region barren of
stars to naked-eye vision, about 14 degrees obliquely south of
Spica. This wonderful planet is the sixth in order outwards from
the sun, but is the second in size of the primary planets. In
appearance, to the casual observer, this great globe is reduced to a
mere point of light by his enormous distance from the Earth. It
is almost incredible that such a tiny point of light should contain
within itself a system as vast as it is unique ; but just as the small,
dark speck on a microscope slide may be the centre of a complex
organism, invisible in all its exquisite structure to the naked eye,
but rendered clearly apparent in all its intricate beauty with the
aid of a powerful objective, so is that marvellous ringed system of
Saturn as seen through a good telescope.

On May 5th, 1896, at nine hours, Saturn was in opposition,
and was then distant from the earth some 825,080,000 miles, being
at his nearest approach for the year, and was consequently at his
best to be seen and examined, though, unfortunately, low down
toward the horizon, and often obscured by clouds and smoke. At
the present time, Saturn is practically useless for observational
purposes, for our own Earth, in her annual journey around the
sun, has reached a point in her orbit about opposite to that where
she was on May 5th, 1896, placing Saturn in the position known
as " in superior conjunction " — the actual date and time being the
13th instant,* at two hours — or, in other words, in a line with the
Earth, but beyond the sun ; hence we have increased the distance
between us by the diameter of that section of the Earth's orbit,
less the difference caused by the elevation of Saturn of 2"io'43*8"
above the plane of the Earth's centre. (Here a diagram was
referred to, showing the distance for the 13th instant between
Earth and Saturn, as taken from the logs of the nautical almanac,

* This paper was written in November, 1896, and read before the Leeds
Astronomical Society.

SATURN. 215

working out at 1,014,322,100 miles, whereas if Earth and Saturn
were in a direct line with the sun's centre, there would have been
the greater distance of 61,804 miles). While Saturn is now actually
elevated above the plane of the Earth's orbit, the plane of his rings
is much lower because of their great tilt, and so we are at present
looking upon the northern side of the ring system, which will con-
tinue until 1899, when they will extend beyond the two poles of
the ball, and be at their widest opening, and the planet will then
be 20° in Saggitarius ; at present he is in the sign of Libra.

The diameter of the ball of Saturn, according to Professor E.
E. Barnard's latest micrometrical measurements, is 76,470 miles
equatorial and polar 69,770, so that the polar compression would
seem to be r — 11*42; therefore the volume of Saturn follows at
822 times that of our Earth.

Saturn requires nearly 29^ of our years to complete his annual
journey of almost 5,559f millions of miles around the sun, at an
average speed of 5*95 miles per second; so that while he sways
once around his mighty orbit, our comparatively small globe, that
is flying through space at a rate of over eighteen miles per second,
is completing its thirtieth revolution, or year ; but a day with us
equals 2^ of Saturn's days 1 This latter difference arises from the
rapid axial rotation of the great planet, which turns completely
around once in every loh. 14m. 30s., while we rotate once in
23h. 56m. 4'o9S. The equatorial circumference of Saturn is no
less than 241,040 miles, as he is seen from limb to limb, or over
ten times that of the solid Earth ; so that while matter is carried
around at our equator at the rate of about 1,000 miles per hour,
matter at Saturn's equator will be whirled around 23^ times faster,
or 23,560 miles an hour. This surface velocity at Saturn's equator
is strong proof in favour of his being in a highly heated condition,
as suggested also by his low mean density, the lowest known in
the Solar system. His seasons, for such there must be, judging
from his axial pose of 26° 43' 23" to the plane of his orbit, we
cannot possibly picture what they are like. Their lengths, we can
say, must each cover a period of over seven of our years, and that
from the Saturnian autumnal to vernal equinox there must be an
interval of nearly fifteen of our years.

The disc as seen is not necessarily the ball that forms the solid,

216 SATURN.

or great mass, of Saturn. There may be an atmospheric shell of
extreme tenuous gases, but capable of carrying sparsely strewn
clouds surrounding a heavier nucleus, or how shall we account for
the various markings seen to cross his face, and these not perma-
nent, for they have been followed in their changing aspects, and
so have helped to a determination of the planet's rotation ? The
equatorial bright zone has disclosed the presence of white spots, or
areas, as if it were hot matter that had been flung up from within.
Two of these white areas are shown in the drawing as seen on
May 5th, 1896, at i2h. One appears to have been about 2^" and
the other about ^" in diameter, or about 10,000 and 16,000 miles
each respectively in horizontal diameter. Dark spots, too, were
seen in the N. temperate belt. A bright margin to preceding limb
was also seen and noted as the brightest portion of the planet ;
indeed, it could be described as luminous, almost suggestive of a
highly reflective atmosphere. This bright margin was estimated
at about |" of arc in w^idth, equalling about 2,145 n^iles. Spectro-
scopic examinations by Huggins show an atmosphere to Saturn
similar to that of Jupiter, while Janssen's indicates an aqueous
vapour. Vogel's spectrum analysis shows more atmospheric bands
on the ball than in the rings. Many of the varying features and
fluctuations of light noticeable on Jupiter's disc are to be seen in
Saturn's case ; but, of course, more feeble and difficult to glimpse,
as from the greater distance of Saturn from the Sun the centre of
his disc receives not quite one-third as much sunlight as does the
centre of Jupiter's disc.

The excentric position of the ball of Saturn was next referred
to and shown in the drawing. While the top of the inverted
image could not be seen with certainty above or over the rings, the
bottom, or N, certainly protruded beyond, showing a northerly
displacement, it was thought, of about J" of arc, or equal to 2,145
miles. This excentricity of the ball is thought to be mathemati-
cally possible. The distance of the limb of the planet from both
ansae, it is said, has been seen to differ as much as ^ '^^ ^^^' ^^'
in other words, the space between the ball and the rings on the
eastern side has been found to measure some 2,145 ™iles wider
than on the western side. Galle, in 1684, was the first to observe
that the ball was not placed centrally in the rings, though he

SATURN. 217

claimed that the western side was the widest ; but Schwabe and
the Roman observers considered the excentricity of the ball
rapidly variable in 1842 and 1843.

It is one of the prettiest sights in the heavens to see the circle
of light girdling the ball, as it sweeps silently and swiftly across
the field of view. According to Professor E. R. Barnard's latest
micrometrical measures — the results of two years' observations —
the outer diameter of the outer ring was found to be equal to
172,310 English miles ; while the width of the A, B, and C rings,
Otto Struve's designation of the three principal rings, including
the divisions in them, represent 42,060 miles ; then comes the
space of 5,860 miles on either side of the ball, which, with the
latter measuring 76,470 miles across, equatorially, make up the
grand total as stated above. This unique and stupendous series
of bands of illuminated, and probably solid but separate particles,
baffled the scientific world for a long time. Prof. Clerk Maxwell
solved the problem mathematically by advancing the theory that
the rings were made up of myriads of meteoric bodies, each pur-
suing its own independent orbit around its centre. Professor
Keeler has since announced a variability in the velocity of different
parts of the rings, as disclosed with the aid of his spectroscope ;
and E. M. Antoniadi's recent observations further strengthens Prof.
Clerk Maxwell's deductions, for the latter gentleman claims to have
seen the outer edges of the A ring broken up, and showing whitish
areas, or markings. On the night of May 5th, 1896, with fine
definition, I also saw the outer edges of the A ring, similar to that
shown in my drawing, giving the appearance of being broken up
and fragmentary, and darker than the inner portion.

It is thought quite possible that Mimas, the innermost satellite,
travelling at a distance of only 30,595 miles from the surface of
Saturn, may cause a variability in the velocities of the outer
members, or small bodies that constitute the ring system, and
some of these synchronising with the motion of Mimas, when near
to the place of the satellite, would create gaps, or intervals, of
varying distances, causing the fluctuating features suspected in that
section of the ring. The " B," or central, ring is the broadest and
brightest in the system, and E. M. Antoniadi has announced a new
division in it, with two fainter ones on either side. The " C," or

218 SATURN.

crape, ring was seen by me very clearly during the last opposition,
and it certainly extended from the inner edge of the " B " ring
nearly, if not quite, half-way toward the ball. It is considered that
this ring is tending inwards, and that the small bodies that probably
belong to it are falling down into Saturn's atmosphere, appearing
in it somewhat similar to shooting stars, or meteors, that plunge
into our atmosphere, and that their places are being taken by
members from the nearest parts of the next ring. The present
appearance of this marvellous ring is that of an exquisitely delicate
piece of gauze-like, golden, and dark purple material, so slender
as to baffle a fair description of it.

This mysterious ring was first seen by the astronomers of the
Roman Observatory in 1828, but they did not report it at the time.
Dr. Galle, of Berlin, in 1838, saw it, and measured it for the first
time, but his observations were carelessly shelved in the Berlin
Observatory. It was left to Professor G. P. Bond, in 1850, to
rediscover this curiously interesting structure, and to announce it
to the world ; while ]\Ir. Dawes independently detected it eighteen
days later, in ignorance of Bond's discovery, the announcement of
which had not then reached England. Close observations of this
"C" ring have continued since 1850, and it has been found to
vary in its aspects and inner outline, as well as its changing angu-
lar position.

The thickness, or comparative thinness, of the rings as a whole
is estimated at considerably under one hundred miles, probably
less than one-half that, but the " B " ring is thought to be thicker
than the outer or "A" ring, because of the convexity of the shadow
said to have been seen cast by the ball on the rings. This shadow
is also said to have been seen concave after opposition ! Such a
variation suggests refraction of light as the probable causes of dif-
ference. If Saturn shone by inherent heat, and the rings reflected
his light only, then they would be lit up all around right up to the
ball on either side, and no shadow at all would be seen, as is
always the case now, both before and after opposition ; thus prov-
ing that the whole system shines by reflected sunlight.

Saturn has eight attendant moons that may be compared with
the sun's eight attendant primary planets. It is strange that the
main outline of the solar system should be repeated within itself

SATURN. 219

in miniature. These Saturnian satellites are almost indescribable
as tiny light points, even when seen under a high power telescopi-
cally, nor is this surprising when we remember the vast difference
that separates us from such comparatively small objects ! The
wonder is that we can glimpse them at all in the feebleness of their
reflected lights, and it is by their light-power that their diameters
are estimated.

What a mighty pendulum-like sweep has Japetus, the outermost
sateUite of the mighty Saturnian system, swinging around his
centre from side to side over a distance of 4,471,460 miles — nearly
twice as great as that of the Jovian assemblage. Let us wing our
flight in imagination away to the night side of Japetus, and picture
the great globe of Saturn encircled with that mighty ring of light,
floating befor