S ALVTl

Library qe
fYORKBOTMICA

ffct QjAI . U AO bu

Digitized by the Internet Archive
in 2009

https://archive.org/details/monthlymicroscop14roya

THE MONTHLY

MICKOSCOPICAL JOURNAL

TRANSACTIONS

OF THE

ROYAL MICROSCOPICAL SOCIETY,

ANT)

RECORD OF HISTOLOGICAL RESEARCH

AT HOME AND ABROAD.

EDITED BY

r

HENRY LAWSON, M.D., M.R.C.P., F.R.M.S.,

Assistant Physician to, and Lecturer on Physiology in, St. Mary's Hospital.

VOLUME XIV.

LONDON:

ROBERT HARDWICKE, 192, PICCADILLY, W.

MDCCCLXXV.

DEC 1 ] 1901

THE

I — Notes on Bucephalus polymorphus.

By Chas. Stewart, F.L.S., Hon. Sec. R.M.S., &c.

( Rend before the Royal Microscopical Society, . Tune 2, 1875.)

Plate CVIT.

Through the kindness of Mr. Badcock I have had an opportunity
of examining that curious animal Bucephalus polymorphus, which
has lately been exhibited at this and other Societies. I regret that
I have only some slight notes to offer on its structure, and can add
nothing to our knowledge of its life history.

The Bucephalus consists of three parts, viz. two spheres, two
appendages borne on these, and a central main body. The spheres
are hollow and contain granules which freely move from one to the
other. In shape each resembles a peach, with the part corresponding
with the cleft of the fruit and point of insertion of the stem, .repre-
sented by a smooth area facing the central body of the animal, and
extending to their outer sides where the appendages are attached';
the remaining part of the spheres presenting a rough warty aspect.

The appendages are densely filled with minute granules, most
abundant near their surface, hut in their interior mixed with
numerous transparent spherules. The appendages are in a constant
state of contraction and expansion, their extremities often suddenly
curling round and forming a spiral of from two to three turns. The
contraction of the appendage in length is accompanied by a synchro-
nous contraction of the sphere at its base, which forces its contents
for a short distance into the appendage, although a thin membrane,
which prolapses, appears to separate their cavities. As might be
expected, when the appendage elongates the sphere dilates and the
contents of the appendage prolapse into it.

The. movements of the central body are not so energetic as those
of other parts, and resemble those of a leech when it is fixed by its

EXPLANATION OF PLATE CVIL
Fig. 1. — Bucephalus polymorphus.

„ 2. — Three layers of central body.
„ 3. — Optical section of ditto.

,, 4. — Front of body.

„ 5. — Side view of ditto.

VOL. XIV.

B

2

Transactions of the Royal Microscopical Society.

posterior sucker. For its examination a power of five or six
hundred is desirable, although its general features may be studied
with a Yoths objective. Its surface is studded with considerable
regularity by minute, upstanding, firm elevations resembling cells,
but apparently quite structureless. Beneath this layer and looking
like a changed condition of its deepest part, are granules of uniform
size and symmetrical arrangement, in rows corresponding with and
transverse to the longitudinal axis of the body ; the latter being
most marked, gave a striated appearance, reminding one of striped
muscle ; at other times by a slight alteration the resemblance to the
markings of a Pleurosigma was most striking. Beneath this layer
is a thin structureless membrane, by a reflexion of which a space
near the mouth is cut off' from the main body ; this space, together
with the general interior of the creature, is occupied by a granular
protoplasmic substance mixed with clear droplets. The mouth has
three lips, and leads into a slight depression or pharynx, often
deepened by retraction into the space above mentioned. On the
middle of the ventral surface is an oval sucker, in size about a third
the diameter of the body: transverse striation is very distinct in its
central depressed part. Behind the sucker a clear, elongated,
curved space was frequently seen in the interior of the body, which
space, after remaining some time, appeared suddenly to collapse.
On the dorsal surface a little in front of the sucker was situated a
somewhat stellate space, over which the surface of the body was
depressed. These spaces perhaps represent a rudimentary water-
vascular system. Near the sucker, in all specimens examined, were
three minute spherical concretions of unequal size, moving freely in
the general substance ; they were the only parts that showed double
refraction under polarized light, under which they were very con-
spicuous. On the under surface near the mouth was an elevation
with a notch at its posterior margin ; at the attached end close to
the spheres were two diffused masses of greater opacity and
granularity.

eMoathly Microscopical Journal, July 1. 1875 PI CVIU

( 3 )

II. — Measurement of Angular Aperture.

By J. W. Stephenson, F.B.A.S., Treasurer K.M S.

( Head before the Royal Microscopical Society, June 2, 1875.)

Plate CVIII.

The necessity of an easy method of determining the angles of
aperture of object-glasses has long been apparent, and the want
has recently been more than usually felt, when the relative angles
of different constructions have been more prominently brought
before the Society.

The object of the scale for the measurement of angular aperture
which I have placed on the table (with some lithographic copies)
is to supply this want, and its merits, if any, are the simplicity of
its construction and its strict adherence to the piinciple of esti-
mating angles which has hitherto been usually adopted.

Being merely a scale of the cotangents of half the angles indi-
cated, it may be laid down from any ordinary trigonometrical
tables.

It is hardly necessary to point out that the distance A B being
constant, the line A cl is always the cotan. of the angle Ad B ; but
as the angle to be measured is twice the angle AcZB, it is so
marked on the scale.

The method of using the scale is this : some small and narrow
body, readily visible, such as a flame or a strip of white paper on a
black ground, is accurately placed at each of the points A and C, and
viewed through the back of the object-glass to be measured, which
is placed above, with its axis parallel to the line A D. By gradually
advancing the objective from D towards B, the images of the flames
(or any other objects employed) separate, until at a certain point
each is seen on the opposite margins of the posterior lens of the
combination. At this point the angle of the glass is seen imme-
diately beneath the front lens.

It will be observed that for the lower angles a side scale has
been introduced. This is necessary in consequence of the very
rapid increase in the length of the cotangents of small angles. In
using this reduced scale, which is only half that of the principal
scale, the objects to be viewed are placed on the points A and B,
instead of the points A and C.

With high powers it is desirable to view the images with an
ordinary hand magnifier, but with low powers this is quite unne-
cessary.

A convenient, but by no means necessary, form of object-glass
holder is shown in Fig. 1, in which the Society’s screw is fixed at
right angles to a brass plate, cut out to facilitate the reading off
with objectives of different lengths.

e 2

4 Transactions of the Royal Microscopical Society.

In the examination of two objectives of equal power without
some means of determining their relative apertures, it is quite pos-
sible that an erroneous judgment may be formed. It may he that
one glass will resolve a given diatom with ease which the other will
not touch, and a hasty conclusion may be arrived at that the former
is the better instrument ; but let each be examined for aperture,
and the cause of the supposed superiority may at once be disclosed.
The greater resolving power may be merely excess of aperture, and
it may turn out that the better glass, both in its manufacture and
for all practical purposes, may really he that which has failed on
surface striation or dotted tests.

It may he said generally that if two objectives differ widely in
aperture they are incapable of comparison ; each may be excellent
in its way, one in resolving power on surface markings, the other in
what is now called “ penetration,” or depth of focus. But they
cannot be compared. In emphasizing the word “ penetration,”
attention is drawn to the change which has been made in the
meaning attached to the word, which by some writers is used as
the equivaleut of angular aperture.

In absolute observations of every kind the element of “ personal
equation ” exists, but it will be evident to all that in determining the
difference of aperture of two objectives that element is necessarily
eliminated.

( 5 )

III. — Notes on the Use of Mr. Wenhcinis llejiex Illuminator.

By Henry J. Slack, F.G.S., Sec. RM.S.

{Read before the Royal Microscopical Society, June 2, 1875.)

If Mr. Wenham’s Reflex Illuminator for High Powers is used
under the circumstances for which he especially contrived it, little
difficulty will be found with , suitable objects. The light, as he
explained, penetrates only where the object makes a new surface on
the slide, and “ acts,” to use one of his familiar phrases, “ like a hole
in a dark lantern.”

The effect is so admirable upon many objects, such as scales of
insects, certain micro-fungi, minute algas, desmids, diatoms, &c.,
that everyone who has successfully tried it must wish to add to its
range of utility, and this may be easily done.

It will be found that most balsamed objects, and many in which
the covering glass lies very close to the slide, give with it so much
false light when ordinary objectives are employed, that the result is
very unsatisfactory. This false light will be found in many cases so
oblique that it can be got rid of by using an objective with a small
angle, or temporarily reducing the angle of an ordinary high power
by a movable stop.

For example, a slide of Surirella gemma and this illuminator
exhibited no false light with a glass of about 7 0° ; some, but not
much,' with a fine fill made on Mr. Wenham’s new formula, and
having an angle of 150°, too much to be endurable with Powell
and Lealand’s immersion f th full aperture ; and none with the
same glass and with a stop limiting the rays admitted to about 90°.

Many slides of butterfly and other scales taken at random from a
cabinet become manageable with reduced apertuies, and the effects,
when the plan succeeds, are very curious, beautiful and instructive.
Mr. Wenham has alluded to the changed aspects obtained by
rotating the apparatus when employed upon the so-called Podura
scale, Lepidocyrtus curvicollis, and similar observations may be
made with regard to Lepisma scales, and those of various insects
allied to Podura. Indeed it is not prudent to pronounce an opinion
upon any scale of difficulty until this method has been tried, and
all the aspects it produces considered in their mutual relations.

It is by no means intended to advise microscopists against the use
of this apparatus with large-angled glasses upon objects mounted
so as to be fit for it ; but when slides fail, the observer is recom-
mended not to abandon the plan, but to reduce the angle of the
glass and try again, and with good chances of success. The appa-
ratus has a remarkable power of increasing both the penetration
and the resolution of good objectives.

( )

IV. — On Dr. Schumanns Formula for Diatom-lines.

By W. J. Hickie, M.A., S. John’s College, Cambridge.

Plate CIX.

In compliance with a general and strongly expressed wish to that
effect, we have here attempted to give the readers of the ‘ I. M. J.’
some sort of an idea of Dr. Schumann’s famous work, though we
fear that, for so doing, some may liken us to the simple-minded
man in Hierocles, who exhibited a brick as a specimen of the house

EXPLANATION OF PLATE CIX.

Fig. 1. — Amphipleura pellucida. ‘ One specimen gave 45 transverse lines, and
45 longitudinal lines, and 61 inclined lines in Another specimen exhi-

bited 38 transverse lines and 55 inclined lines. If we add these, we get
a = 6 = 41 J, c = 58. As 41 J. V‘2 = 58§, there is no doubt that we have here
corresponding series of the simplest sort.”

By inclined lines Dr. Schumann means imaginary lines drawn at a certain
angle from a top row of transverse dots to a lower row of transverse dots. See
his own explanation on pp. 8 and 13 of this number.

Fig. 2. — Navicula lata (= Pinnularia pachyptera Ehrenb.). “Four specimens
from the Siebenseethal exhibited 7 canals, and one from the Kohlbachthal gave
12 canals in . The closeness of the series of puncta traversing the whole
frustule is defined by the formula a. = 4a.”

Fig. 3. — Navicula borealis. “ The c loseness of its series of puncta is defined by
the well-founded formula a = 4 a.”

Fig. 4. — Mastogloia antiqna Sclium. “Whilst specimens found in Prussia gave
27 transverse lines in those from the High Tatra exhibited 44, 45, and 48 ;

to which estimates the formula

a = 19 4-

600

11

T

corresponds.”

Fig. 5.— Navicula crassinervis var. Compare the figure of this in Smith’s
Sjnopsis. Dr. Schumann’s figure gives the transverse lines alone. Pritchard
(Infusoria) says, “ Striie wanting or indistinct.”

Fig. 6. — Navicula rhomboides ? (Ehrenb. Amer. III. 1, 15). “Three frustnles
from the Mengsdorfthal with 78 transverse lines in T)r5"' appear to belong to
Ehrenberg’s form, though their length is only 8-9 T.” His drawing gives n>
longitudinal lines. He seems therefore either to have overlooked them, or not to
have known of their existence.

Fig. 7. — Nav. rhynchocephala. “In one part of the High Tatra with 34, in
another with 36 punctated transverse lines in y^'". ”

Fig. 8. — Nav. angustata. “ This diatom has in Prussia 40, and in my highest
station on the Tatra 68 transverse lines in yiy”'. ”

Fig. 9. — Campyludiscus nanus m. “ On the margin appears a scries of fine
puncta, which, at an elevation of 5500 feet, numbered 53 in

Fig. 10. — Nitzschia minutissima. “On combining my estimates of ten speci-
mens found in Prussia with my estimates of the sixteen found on the Tatra,
1 obtained the following formula for the number of marginal puncta :

5

9 ’

If this formula were well established, we should have an excellent means ot
determining the height of a place by the help of microscopical observations, as
this diatom is probably frequent on other mountain ranges also. ’

Tl.CJL

Dr. Schumann s Formulae for Diatom-lines. By W. J. Ilickie. 7

he had to let. Light reading we certainly cannot promise them ;
but, such as it is, we commend it to the perusal of those “ qui volunt
et possunt.’’

The learned author begins by observing that, though several
microscopists have published valuable remarks on the diatom -
frustule aud its striae, yet one essential property has been left
uninvestigated, namely, the dependence of the different striae-
systems on one another — in other words, the relation in which the
diatom-lines stand to one another.

He proposes therefore at the outset to investigate certain
principles which regulate the position and closeness of the diatom-
lines, without dwelling on the form of the material puncta or the
dots. He then adds, “ I shall first discuss two simple cases of
frequent occurrence, and then subjoin some data, which apply to
every position of rectilinear diatom-lines.

If we examine a Navicula, we observe on each side of the
median line striae running to the marginal edge in a direction
perpendicular to the median line ; these transverse lines, in some
species, it would seem, consist of canals, in others of material
puncta, more or less distinct, whose centres are mostly equidistant
from one another.

But the canals also constantly form equidistant spaces ; perhaps
in consequence of constrictions or intrusive ridges. Frequently
they look like strings of pearls communicating with one another by
wide ojienings. If we examine one of the two adjacent series, we
find in most species of Navicula that this series is a repetition of
the fundamental series ; that therefore the connecting line of
adjacent puncta of both series runs parallel to the longitudinal axis
of the Navicula. Thus the transverse and longitudinal lines
present the appearance of a chess-board.

Yet the longitudinal lines generally have a width apart different

Fig. 11. — Nitischia thermalis. “One specimen exhibited 16 eye-like puncta
and 80 transverse lines in -j-jjo"', anti another 18 such puncta in j^'". ”

Fig. 12. — N itzscina n.edia. “Three frustules from the Mengsdorfthal showed
26 puncta and 74 transverse lines in ”

Fig. 13. — Mitzsciia communis (= Syne dr a notata Ktz.). “ Sevi n specimens
gave 28 puncta and 80 transverse lines in T^'". ”

Fig. 14. — Nitzscliiella cluster ionics (Grunow, Wien, 1862, p. 582, XII. 19). “ Two
fiustules exhibited 31 puncta and 90 transveise lines in whilst another

from the Kohlbnchthal, though only half the length, showed 29 puncta and about
100 transverse lines in ”

Fig. 15. — Achnanthes clliptica m. “ The number of the coarse lines in the lower,
middle, aud upper stations of the Tatra amounts to 35, 38, aud 41 respectively
in ”

Fig. 16. — Gomphonema montanum. “The transverse markings of the shell arc
canal-formed. In two specimens with 25 canals the shell exhibited 62 tine trans-
verse lines in ”

The author adds that the entire number of species found on the Tatra amounts
to 235 at least.

8 Dr. Schumanns Formula} for Diatom-lines. By W. J. Dickie.

from that of the transverse lines. Consequently the entire structure
consists of numerous rectangles, standing upon and near one
another.

On the contrary, in other species of Navicula the puncta of the
next succeeding series are, as it were, put out of place, and not till
the third series do we find a repetition of the first.

In this case the structure is divided into oblique-angled paral-
lelograms.

The former case I call the corresponding, the latter the alter-
nating series.

In Figure 1 let G A be the longitudinal axis of the frustule (or
a line parallel to it), and the horizontal lines G H, C J, A K, the
so-called transverse striae, and the lines standing perpendicular to
them, the longitudinal striae.

The structure then consists of rectangles, one of which is
A C B F. This I divide by a diagonal into two right-angled tri-
angles, and take the triangle A B C as the basis of the structure.

Let a. denote the width apart of the horizontal striae, and /3 the
width* apart of the vertical striae, and 7 the shortest distance apart
of the inclined striae ED, AH, &c.

Ehrenberg more than thirty years ago drew attention to the
value of the magnitude a, as he found it, in the same species,
pretty nearly a constant. He ranked it therefore as a characteristic

Dr. Schumann's Formulae for Diatom-lines. Bij W. J. Hichie. 9

mark of the species, and determined the number of such strife there
should he in a Paris line.

For example, if there be 30 such transverse strife in rJV", then
30 « = i^o'" ; therefore « = ^W".

If we let a denote the number of these transverse strife in
a certain length, taking either too of a Paris line, or XTjVo °f an
Fnglish inch, or any other standard of measurement, and denote
the standard itself by E, then

E 1 a

(( . « = E , a — — > — = rr •

a U. E

If we call the corresponding numbers of the vertical and
oblique striae b and c respectively, then

1 - 6 and I - £
h ~ E ’ dn 7 — E

It follows now simply from Figure 1 that

7 . A B ~ a. . ji , y = — ^ ’

\f a2 + /S’"

We see now that the line-number, c, is more directly dependent
on the line-numbers, a and b, than 7 on a and /3. And herein lies
the value of the above given definition of the line-number, inde-
pendently of the fact that the magnitudes a, b and c are to be
directly considered, whilst a, /3, 7 have to be deduced from them
afterwards.

We may remark also that the numbers of the lines stand in the
same relation to one another as the corresponding sides of the
triangle, inasmuch as both are inversely proportional to the heights
of the triangles.

Yet (setting aside the three primary series) others also appear,
which I call secondary, namely, the series A D, BE, C F.

Now, if we call the numbers of the lines corresponding to them
d, e. f, we easily find

d = \/ a2 -j- 4 62, c = \t i d 1 + 62, / = c.

In Figure 2 the direction of the above-mentioned series is
denoted by the lines U A, U B, . . . . U F.

To these, as the figure shows, two others are added, namely,
U D' and U E'.

10 Dr. Schumann s For mul-ee for Diatom- lines. By \\ . J. Htckie.

The two latter we get from the triangle B C (t. Moreover the
number of the secondary series is not limited to these ; for we may
divide the structure in many other directions by straight lines drawn
through fixed points. Their common line-number is f p1 a2 -f <f L2,
where p and <j are any whole numbers.

'/

But it is of no practical utility to concern oneself with these,
since it is difficulty enough to find out the lines U D, U E, and
those corresponding to them, even in coarsely marked shells.

The form also of the dots in this case plays an important part.

Lastly, if the inquiry is after the smallest angles which the
lines U C, U I), UE make with the longitudinal axis, the question
is one of easy answer. The trigonometrical tangents of these
angles are, respectively,

a a 2 a

V 2 V T '

The following genera and species, so far as my observation goes,
exhibit corresponding series:

Epithemici, Eunotia , Himaniidium, Meridion. Podosphenia,
Bhipidopliora, Odontidium, Diatoma vidgare, Fragilaria virescens
and elliptic a, Synedra , Tabellaria. G omphogr amnia, all species of
Surirella known to me, in their fine systems of puncta, Amplii-

Dr. Schumann s Formidve for Diatom-lines. Bij W. J. Rickie. 11

pleura pellucida, Denticula, Nitzschia amphioxys (with less distinct
longitudinal lines), almost all species of Cocconeis, perhaps all
species of Achnanthidium and Achnanthes; Rhoieosphenia curvata,
marina, fracta and baltica; Cymbella, Goceonema, Encyonema,
Amphora, all species of Ceratoneis known to me, Gomphonema,
almost all species of Navicula (and amongst them perhaps N.jirma),
Amphigomphus dilatata, Scoliopleura Jennerii (with irregular
longitudinal lines), Scol. convexa, almost all species of Stauroneis, as
Staur. punctata, truncata, Eichhornii, Plioenicenteron and amplii-
cepliala ; Pleurostaurum acutum, Frustulia Saxonica, Doryphora
BdcJcii, those species of Pleurosigma treated of by Smith and
Rabenhorst as Section 2, several cylindrical forms, on their front
sides, as Melosira distans, nivalis, salina.

The formula c = a1 -f- b2 is excellently well adapted for deter-
mining the amount of error of estimate.

For example, I found in one specimen of Pleurosigma
attenuatum,

a = 30, b = 22, c = 36.

If the proportionally easy estimates of a and b he assumed to
•be exactly correct, then must c = V 900 + 484 = 37 ' 2 ; conse-
quently the relative error of the last estimate would be

12 _ _1
37-2 ~ 31 '

Again, three specimens of Pleurosigma strigilis on an English
slide gave me,

(1) a = 25, b = 35, c = 44, instead of 43.

(2) a = 26, 6 = 36J, c = 46, „ 45.

(3) a = 26£, b - 38, c = 47J, „ 46f

Smith’s estimate is, if we turn his figures into our measurement,
a = 32, b = 35 J,

and therefore the number of the transverse striae perceptibly
greater. To be sure, I measured the width of the lines in all three
instances close to the central knot, and this may possibly have given
rise to the divergence.

In Pleurosigma fasciola I found a = 54, b = 50. The oblique
strife in this case I was unable to see.*

* And no wonder ; for there are no oblique striae on it. In resolution, to know
beforehand what to look for is half the battle; therefore drawings of the Dia-
toraaceao without the striae are almost worthless.

1 2 Dr. Schumann’s Formulas for Diatom-lines. By W. J. Hicltie.

Special Case.

Not unfrequently the width apart of the vertical series, or lines,
is about equal to that of the horizontal lines, d.h.b = a.

In this case (for which see Fig. 3),

c=/=«V 2, about a.

d — e = a ,,

Fig . 5

B D C E

G -Q © — — — 0

The two most distinct of the oblique systems of lines U C and
U I form with the axis angles of 45°, and consequently stand
perpendicular to each other.

Of the secondary systems, UD and U E', as also U E and
h D , stand perpendicular to each other, as they form with the
axis angles of about 2G4 and 634 degrees.

To this class belong Epitkemia probosciclea, Westermanni,
granulata ; Himantidium pectinate, Fragilaria virescens, Denti-
cula elegans, Ampkipleura pellucida, Stauroneis Eichhornii and
amphicephala, Fleur ostaurum. acutum, Pleurosigma lacustre,
Melusira distans and salina.

Yet this special case is seldom sharply marked.

I found, for example, in one specimen of Fragilaria virescens .
a ~ 38, b — 36, c — 54.

In both cases the relative error of the third not easy estimate,
il we assume a and b to he exactly correct, or a = b = 37 is
suppose, E.

Dr. Schumann’s Formula? for Diatom-lines. Bij W. J. Dickie. 13

I find the average values to be

For Tabellaria fenestratata, a = 33, b = 32,

„ Gomphogrammi rupestre, a = 33, b — 29.

The triangle ABC, which I take as the basis of the structure,
is in this case isosceles.*

The directions of the three primary systems of lines are deter-
mined by the sides of the triangle, and the transverse lines by C B,
and the inclined lines by C D (or A B) and C A.

The three secondary systems of lines have the directions A D,
B E and C F. The longitudinal lines D A, P Q, H F, &c., conse-
quently appear here as secondary.

For this structure the following formulae hold good :

d = V 4 b2 — a2, e = / = s/ 2 «2 + 62, b = c = | *J a- + d •,

where a denotes the number of the transverse lines, and el the
number of the longitudinal lines which appear in a given space, —
say T^jr of a Paris line.

In Case 1 we found the following rules : If we square the
numbers of the transverse lines and of the longitudinal lines, and
add these squares, and then extract the square root, we get the
line-number for the primary oblique system. Here in Case 2 we
must further divide the number so found by 2. This is the
essential difference between the corresponding and alternating
series and their structures.

If we be in doubt to which class the species of diatom belongs,
we may employ this means to decide the matter, when the single
puncta are indistinct.

For example, if, in any species, we have found 30 as the number
of the transverse lines, and 40 as the number of the longitudinal
lines, and lastly, 50 as the number of the most distinctly appearing
oblique lines, then we are certain that the series of puncta are
corresponding series.

If, in another species, we find 30, 40, and 25 as the correspond-
ing line-numbers, the structure consists of alternating series of
puncta.

If we take 0, , </>2, . . . </>,, to denote the smallest angles which
the six systems treated of form with the axis, then we get

„ A J . CL „

<f>, = 90°, <p2 = <*>3 = — , sin. <p2 - sin. <p3 = — , =0 ,

3 a , A

sm. <f>5 - sm. <pt . = ' , tan. <£. = tan. (b, = 3 tan. — i

2 s/2 «2 + 62 2

* The diagrams pertaining to this part have been unavoidably omitted for
typographical reasons.

14 Dr. Schumann s Formulae for Diatom-lines. By W. J. Hickie.

where A denotes the angle B A C, which one may easily get from

A a

the estimated line-numbers, since sin. "2 = 2 h ‘

Whilst diatoms of an extended form mostly exhibit corresponds
series of puncta, those whose obverse sides are developed about
point not unfrequently exhibit alternating series.

First Special Case.

When A = 60°, then the triangle A B C is equilateral (see
Fig. 5).*

In this case,

a = 6 = c, e=f = g — a\l 3, about \ a,

<pl = 90°, <p„ = cp3 = 30°,

= 0°, <ps = <p6 = 60°.

The three primary systems cut one another at an angle of 60° ;
the secondary likewise. The latter stand perpendicular to the
former, and may be easily found in consequence.

To this class belong most of those species of Pleurosigma which
Smith and Babenhorst treat of as Section 1 .

Further :

Biddulphia turgida and radiata (Syn. LXII. 384, 385).

Triceratium favus (Syn. XXX. 44).

Podosira Montagnei (Syn. XLIX. 326).

Melosira subflcxilis , orichalcea.

Yet even here some notable deviations from the uniformity
of the numbers of the lines occur. I found, for instance, in a
specimen of

Pleurosigma angulatum, a = 44, b = 46, c = 46,

and in

Pleurosigma strigosum , a = 46, b = 46, c = 39.

In the latter case, according to my estimate, the angles of
inclination also of the two oblique systems were sensibly different.

Second Special Case.

When A = 90° (for which case see Fig. 6),* then

b = c = °- d2, about T7C «, d = a,

e = f = ^ \l 5, about | a, cf)l = 90°,

<p2 = <Pz = 45°. ^>4 = 0°.

tan. <p3 = tan. <£„ = 3, $5 = <pe, about 71£°.

* See footnote on preceding page.

P 3Q

Dr. Schumann s Formulae for Diatom-lines. By W. J. Hiclcie. 15

If we compare the special case of 1 with this, we find there

e = a J 2, and here c = ^ ^ 2, a ratio which furnishes us with an

excellent means of distinguishing the structure of different diatom
shells.

To this class belong Navicula tumens and Nav. sphserophora,
Wien, 1860, II, 84 ; Gocconeis clecussata, Elirenb. Amer. II. vi,
13 ; Cocc. placentui a and oceanica.

Many species of Pleurosignna at least approximate to this case,
as the inclination of their oblique systems of lines to the middle
line does not amount to 60 J, but sinks towards 45°.

As a case in point, I mention Fleur, elonyatum.

One specimen of Stauroneis nobilis m. gave

a = 30,

b = c = 21 ;

Another gave

« = 27,

b = c = 19;

A third gave

« = 3H,

HC4

CM

II

II

-C>

As 21.V2= 29-7, and 19.^2 = 26-9, and 22£ V2 = 31 8,
the measurements agree right well.

Let this much suffice as a specimen of Schumann’s modus
operandi. Those who are desirous of a further acquaintance are
referred to the original work.

VOL, XIV,

o

( 10 )

PROGRESS OF MICROSCOPICAL SCIENCE.

Minute Structure of the Brain of the Insane. — This is a subject of
considerable importance, the more so as some of our best authorities
deny that the brain of the insane is materially different from that
of the perfectly healthy man. The ‘ Medical Record ’ for April 14
gives an account of a paper on this subject by an American physician,
which is of interest. It is as follows : — Dr. Walter Kempster, of the
Northern Asylum for the Insane, Oshliosh, Wisconsin, presented to
the Chicago Society of Physicians and Surgeons some “ Notes on the
Microscopical Appearances of the Brain of the Insane,” based on the
examination of forty-nine cases. For a number of years Dr. Kempster
has been making systematic microscopical study of the brain, and has
examined the lesions of all forms of insanity, from acute mania to
dementia, including puerperal and epileptic insanity. In each and all
forms he has found a marked lesion — so that certain lesions may be
grouped together as common to certain forms of insanity, to which
lesions any particular type of insanity is palpably due. There is a
wide difference between the lesions of acute and of chronic mania.

1. In certain forms of insanity, and notably in dementia, the finer
capillaries show marked indications of disease. The perivascular
sheath surrounding the vessel is distended ; so much so, that some-
times the vessel itself appears to lie in a tunnel, its calibre being
much less than the sheath, doubtless due to repeated capillary conges-
tions of the vessels — often diseased — irregular in calibre, suggesting
the idea of aneurismal dilatations, hut entirely distinct from the
miliary aneurisms ably described by Charcot.

2. Next there is a degeneration, best studied in cases of dementia
of syphilitic origin, and in the medulla oblongata, in the wall of the
capillary, presenting dark-red patches at various points outside its
walls, which gradually thicken, and appear to be due to a fatty meta-
morphosis or atheroma. The description by Meynert, though accurate,
is by no means so complete as could be desired.

3. In 1871, while examining a section taken from the grey and
white matter of the third left anterior convolution, there was found a
peculiar appearance of the tissue. Situated in the white substance,
but very closely to the grey matter, there were a number of small
white spots, some round, some ovoid, clearly defined, in sharp contrast
with the nerve-tissue, varying in size, from ^ to of an inch in
diameter. These appeared to be of a granular consistence, and much
more dense in structure than the surrounding brain-substance ; each
was disconnected from the others, and normal white matter intervened.
They did not absorb carmine, and were not connected with the
capillaries. On the surface of some of the spots are fibres of connec-
tive tissue and crystals of margarine. To determine the true character
of theso spots and the degeneration, very elaborate and extensive micro-
chemical manipulations were made. On allowing a section to dry,
either with or without tho nitric acid treatment, these spots appear to

PROGRESS OF MICROSCOPICAL SCIENCE.

17

project above the surface of the section. By teasing, they may with
difficulty be removed. None of these spots have been observed in the
grey matter. They are most numerous in the medulla oblongata, and
may be found in the white matter of the spinal cord.

4. There is another form of degeneracy, one which was found in
the cases of acute mania. The spots are less in size ; are far more
numerous than in the other variety (3) ; resist carmine staining; do
not possess the granular characteristic ; there are no spindle-shaped
fibres of connective tissue about them ; they behave very differently
under the micro-cliemical tests applied to the other variety of spots.
The points of resemblance are mainly in colour and apparent density.
Neither of them have any investing membrane.

5. A fifth variety, as large in size as the third, possesses a dense
investing membrane, which resists carmine staining and is less
granular than the third and fourth. It exists in the same brain with
the fourth variety. These spots or masses of the fifth variety are
called “ colloid,” because of their resemblance to such growth, and are
found in the medulla oblongata and pons Varolii. The last three
varieties of degenerated masses, or spots, have one feature in common,
a well-defined edge, a clean-cut margin, easily made out.

6. A sixth variety, common in cases of dementia, and where the
atheromatous capillary is found, is one in which the mass passes
insensibly into the surrounding normal tissue. This form is larger
and less distinct than the others. It more nearly resembles normal
brain-tissue. Sometimes these masses are lobulated. They are granular
and dense, less numerous than in the other varieties, and do not appear
in clusters. They appear to destroy or transform the tissues, and if
surrounding a capillary, destroy its walls. A point of resemblance in
common with the third variety is, that connective-tissue fibre appears
in both.

The condition of the cellular structures of the brain, of the nerve-
fibres and so-called lymph-spaces, are all fields rich in results not
here spoken of.

The Bloocl-globules of a Nemertian Worm. — The ‘Academy ’ (May 8)
says that M. Marion, in a communication to the French Academy,
describes a nemertian worm, Drepanophorus spedabilis, as possessing
“ a vascular apparatus which exhibits the surprising peculiarity of
containing elliptical, slightly flattened red globules, like those of
human blood. Their largest diameter is O' 01 mm. . . . When a
portion of the body of the worm is pressed, these corpuscles accumu-
late in certain parts of the circulatory system, and form a mass of an
intense red colour. The movements of the globules can be followed
by viewing the animal as a transparent object. They are put in
motion by a colourless liquid, in which they float in a constant direc-
tion. The animal possesses a median dorsal vessel, and two lateral
ones, situated on the ventral side. Below the nervous ganglions the
dorsal vessel bifurcates, and anastomoses with the two lateral trunks,
which follow the posterior margin of the superior ganglions, and aro
prolonged into a cephalic ansa. The dorsal canal gives rise to trans-
verse ansa?, regularly spaced. Each of these branches continues to

c 2

18

PROGRESS OF MICROSCOPICxiL SCIENCE.

the flank of the creature, then curves back towards the ventral surface
and opens into the lateral vessel. There are, consequently, numerous
capillary ramifications, exceptional amongst the nemertians, hut recall-
ing the arrangement described by M. Blanchard in Cerehratulus
Liguricus ” “ The structure of the highly developed proboscis neces-

sitates the establishment of a special genus for these nemertians;”
and M. Marion adopts the name “ Drephanophorus ” proposed by Mr.
Hubrecht.

The Character of the Starch-granule . — Professor Harrington, in a
paper in the ‘ American Naturalist ” for April, says that if we take a
little of the starch from the potato and dry it, without the addition of
water, at a temperature of perhaps l"jO°, we shall see a dark point
appearing at one end — usually the smaller. This is the nucleus, and
around it are arranged concentric rings. It has been described as a
little pedicle or stem by which the starch-grain is attached to the cell-
wall. This was when it was still thought that the grains budded out
from the wall, a theory completely disproven now, by what is known of
the development and functions of the wall, as well as by specific obser-
vations on the formation of the grains themselves. The nuclei have
been described too as holes, passing into the interior from the outside,
and admitting the materials from which the successive layers were
formed from without inwards. If the development of the starch-
grain were endogenous, there might be some ground for this hole-
theory of the nucleus, but it is now well proven that their formation
is from within out, or exogenous. There is no easily accessible
specimen at this season of the year to illustrate this, but writers
generally refer to ripening corn, wrhere all the stages can sometimes
be seen in a single grain. However, we can easily prove with the
specimens under examination that the nucleus is neither a little stem
nor a canal. If it were either, it would appear, as we roll the grains,
sometimes elongated. As we roll the grains over, by inclination of
the stage, or pressure from one side, as before, we see no difference in
the shapo of the nucleus. It is the same round or angular black spot,
occupying the same position from whatever point it is viewed. If wo
are lucky, we may get a grain up on end, and examine it in the direc-
tion of its long diameter. The position of the nucleus and arrange-
ment of the rings remain the same.

What can we conclude concerning the nature of the nucleus from
this ? It wras indistinctly or not at all visible in the fresh grain ; it
becomes visible on drying, and looks like an air space. It is in the
structural centre of the grain. If the drying is carried far enough,
cracks may be seen extending from the nucleus. They generally
radiate, looking something like a star. Sometimes one long crack
runs the greater part of the length of the grain. The cracks may
and may not reach the surface. Taking all these facts together, we
can draw the fair conclusion : that the layers differ in density ; that
the inner layers are softer than the outer, because they contain succes-
sively more water ; that the water is driven off by the heat and the
consequent vacuity appears, forming the “ nucleus,” where there is
most wrater, that is, in the innermost layers ; that farther drying

PROGRESS OF MICROSCOPICAL SCIENCE.

19

causes cracks to appear in the harder layers, the longer the drying the
more extensive the cracks.

The Minute Structure of the Ovule. — Three or four of the last
numbers of the £ Botanische Zeitung ’ have been almost wholly occu-
pied with an article of Celakovsky’s, entitled “ Vergriinungsgeschichte
der Eichen von Alliaria officinalis,” or history of the development of
phyllody in the ovules of the plant named. The morphological
dignity or nature of the ovule is still a moot point with physiologists,
who are by no means agreed as to the significance of the monstrous
conditions and transformations of this organ observed occasionally in
different plants. The most logical view seems to be that it is of the
same nature in all plants, though the explanations offered for different
teratological phenomena exhibited by the ovule would point to a
diversity of origin and dignity. Celakovsky seeks to throw some
light on this subject by a careful and minute study of the different
phases of transformation or malformation observed in the ovules of a
proliferous inflorescence of Alliaria officinalis. He objects to the
assumption that because the ovule sometimes develops as a shoot, the
nucleus is a bud. Through this long paper he describes and figures
the various modifications he has found of the leafy transformations of
the ovular coats and a “ funicular appendage ” and the presence of a
bud. He endeavours to show that the ovular shoot is not a metamor-
phosed state of the nucleus, and says here we have an indisputable
proof that the ovular shoot is not a transformation of the nucleus, and
every explanation that the latter is anything more than an outgrowth
or metablast must fail. In his investigations he believes he has found
the nucleus present in the same ovule in which the bud is developed,
and quite independent of it. — The Academy.

The Microscopic Appearances in Inflammation of Connective Tissue.
— Dr. G. Thin has communicated a valuable paper on this subject to the
Royal Society. The following abstract of his views is taken from the
‘ Proceedings of the Royal Society ’ (No. 160). The author, referring to
observations recorded in his previous papers, distinguishes in the
cornea primary bundles of fibrillary tissue, which are covered by
elongated flat cells, layers of quadrangular flat cells (which are analo-
gous in appearance and relative position to the layers of cells
described by him as investing the secondary and tertiary bundles of
tendon), and the stellate cells. To these he now adds a description
of parallel chains of spindle-cells, each cell having two processes, one
at each end of the spindle, by which it is joined to its fellows on
either side. These cells are coextensive with the cornea substance,
and are present in every interspace of the primary bundles, and con-
sequently layers in different planes cross each other at an angle.

They can be occasionally seen in thin vertical sections of the fresh
frog’s cornea, treated in osmic acid ; and from such preparations a cell
with its terminal processes can be sometimes isolated.* They are
more easily seen in similar sections which have been 15-30 minutes
in half per cent, solution of chloride of gold, and then sealed up in
concentrated acetic acid and examined 24-48 hours afterwards.

They have no anatomical continuity with the stellate cells.

20

PROGRESS OF MICROSCOPICAL SCIENCE.

In tlie fresh frog’s cornea examined entire in serum, the structure,
looked at through the anterior epithelium, can be seen to he broken
up by clefts, the borders of which have a double contour. These
clefts extend from the epithelium to a varying depth into the fibrillary
tissue. They are arranged sometimes concentrically, and sometimes
in waving lines, which give off branches which are narrower as they
approach the centre of the cornea. The double-contoured borders are
not parallel to the median plane of the cornea, and can be traced only
by changing the focus.

From the existence of these clefts the author infers a division of
the cornea substance into compartments equivalent to the secondary
and tertiary bundles of tendon.

In inflammation the clefts are much widened, and their finer rami-
fications become visible. In preparations of inflamed cornea different
tracts of cornea substance bounded by the clefts are coloured of diffe-
rent shades by chloride of gold, the difference affecting the fibrillary
tissue, and more markedly the spindle-cells.

The serous contents of the interspaces of the inflamed cornea differ
in character from those of the healthy cornea, inasmuch as the former
show, more abundantly, the dark granular substance which results
from the reduction of the chloride of gold.

In a very early stage of inflammation (after a few hours) the dis-
tension of the narrow spaces between the primary bundles and of the
wider and more yielding spaces between the lamellae, corresponding to
the larger bundles, favours the action of chloride of gold ; and pre-
parations can thus bo obtained by this reagent which show that the
two kinds of flat cells which cover the respective surfaces are arranged
after tho manner of an epithelium. The cells thus seen can be iden-
tified by their size, contour, and arrangement, as those which are
isolable from the healthy cornea by warm saturated solution of caustic
potash, and which can be seen in preparations sealed up in aqueous
humour.

A similar distension occasionally permits the demonstration of the
layers covering the secondary bundles of tendon.

That the successful gold reaction in such cases is probably due
solely to tho distension of the interspaces, is inferred from the fact
that in the tendo Achillis of frogs which have died from disease, and
have been some hours in water after death, the author has obtained
gold preparations showing not only the cells of the secondary bundles
(Ranvicr’s cells), bnt also small groups of the long narrow cells which
cover the primary bundles.

In the cauterized frog’s cornea, examined in blood-serum after
twelve hours’ inflammation, portions of the primary bundles are found
lying loose on the surface. These detached portions have a nearly
constant length, a uniform breadth, sharply-defined even borders, are
sometimes puckered transversely, occasionally show a faint appearance
of longitudinal fibrillation, and arc sometimes cut transversely, at one
or more points, by straight hyaline lines. They resemble accurately
the primary bundles of the neurilemma of the sciatic nerve and the
rods of the retina of the healthy frog.

PROGRESS OF MICROSCOPICAL SCIENCE.

21

They stain deeply in gold preparations, and aro then always
puckered transversely.

In gold preparations of the inflamed frog’s tongue, isolated primary
bundles, identical in appearance and breadth with those of the inflamed
cornea, are to be found.

The depth of staining by gold shows that the constituent elements
of the primary bundles undergo a chemical change in inflammation.

The author has studied, by means of chloride of gold, the effects of
inflammation in the quadrangular and in the long flat cells which
cover the bundles in the interior of the cornea, but chiefly in frog
corner sealed up in blood-serum, the latter method being found more
certain to give available preparations.

The only appearance observed, anterior to a complete destruction
of the cell, was a division of the nucleus into two or more parts. In
serum preparations the products of the division assumed the form of
circles of highly refractive particles. Similar particles were sparsely
scattered in the substance of the cell.

The area of any one circular product of this division was always
much smaller than that of the undivided nucleus.

In regard to the stellate cells, the author questions the correctness
of the accepted theory, which implies an identity of the cell and its
processes with the visible protoplasm. He considers that the refractive
particles, which constitute what is visible in the cellular protoplasm,
are suspended in a fluid, similarly to the pigment-granules in the
pigment-cells as described by Mr. Lister. The phenomenon described
by German investigators as “ Zusammenballen” of the cell-processes,
he attributes to a collection of the protoplasmic particles in the centre
of the cell, similar to that which takes place in concentration of pigment.
This opinion is borne out by a comparison of gold and osmic acid
preparations. In conditions in which, by the former process, an
isolated globular body is seen, osmic acid preparations show that the
anastomosis of the thread-like processes remains complete. Reasoning
analogically from the results obtained by gold in other tissues, he
infers that it is what may be described as the contents of the cell and
processes which stain by that method.

Treatment by osmic acid is the only reliable method by which he
has obtained satisfactory preparations showing the stellate cells in the
inflamed cornea. The advantages of this mode of treatment are much
enhanced by subsequent staining with red aniline, which especially
differentiates the protoplasm and processes. Subsequent staining by
hfematoxylin renders the nuclei visible.

The only change, except that of destructive disintegration, observed
by the author as a consequence of inflammation in the stellate cells,
consists in the anastomosing processes being, in gold preparations,
occasionally represented by fine darkly-stained lines, on which are a
series of small globular swellings placed at short regular intervals,
giving any one process an appearance identical with that presented by
an ultimate nerve-fib rilla in a gold preparation. The same appear-
ance is also to be seen in osmic acid preparations, and is suggestive
of points of communication between the lumen of the process and the

22

PROGRESS OF MICROSCOPICAL SCIENCE.

interfibrillary space. (This is the only form in which the author has
seen the processes of the stellate cells in inflamed cornese in gold pre-
parations. They are usually invisible by that process.)

Appearances indicative of a dividing nucleus were rarely seen, and
their interpretation is doubtful. Both in respect to the nucleus and
the processes the stellate cells are the most stable of all the cellular
elements of the cornea.

Between the layers of the superficial corneal epithelium a network
of stellate cells can be seen in serum preparations of inflamed cornea.
Indications of similar cells can be seen in gold and haematoxylin prepa-
rations of the healthy cornea.

In inflammation the cells of this network show a very great increase
in size as compared with their appearance in health.

The changes produced by inflammation in the spindle-cells may
be divided into three stages :

(a) Preparations examined in serum show that the cell-protoplasm
has become increased in amount, and that the cell-processes can be
distinctly traced. This stage can be observed after twelve hours’
inflammation, resulting from slight cauterization in a winter frog.
The swelling of the protoplasm is often confined to one or more tracts
of the cornea, one of the above-mentioned clefts separating the area
of this appearance from that of the normal cornea. The area extends
from the neighbourhood of the cauterized part towards the limbus.

(b) The swelling of the protoplasm extends along the processes
from one cell to the other, a chain of spindle-cells being often repre-
sented by a long column of protoplasm on which there are very slight
constrictions. This description applies to osmic acid preparations.
Deep staining with red aniline and subsequent treatment with acetic
acid renders the nuclei visible in this pi*otoplasmic column. This
stage is well seen in osmic acid preparations of a rabbit’s cornea which
has been twenty-four hours inflamed by the passing of a thread.

(c) With more or less increase in the amount of protoplasm, and
with or without its presence in the processes in a granular form, nuclear
bodies (resulting from a division of the nucleus) are seen in osmic acid
preparations to be contained in, or partly expelled from, the cell, which
are identical in appearance with the red blood-corpuscles seen in the
new vessels in the same preparations. This identity in appearance is
further maintained by staining osmic acid preparations with red
aniline, in which the nuclear products and red blood-corpuscles are
stained a like tint and deeper than the other elements. The author
infers from these appearances that in inflammation the nuclei become
free bodies, which are equivalent to red blood-corpuscles.

The appearances described by Key and Wallis, Cohnheim, and
others as white corpuscles in “ Spindelform,” are seen in osmic acid
preparations to be spindle-cells made more prominent by inflammation.

The “ spiessartige Figuren” seen in gold preparations are produced
by the protoplasm which immediately surrounds the nuclei of the
spindle-cells being visible, whilst from the mode of preparation the
connecting processes are invisible.

White blood-cells in the inflamed cornea can be identified with

PROGRESS OF MICROSCOPICAL SCIENCE.

23

most certainty in osmic acid preparations. They are found in groups
in the wider spaces, in rows in the nerve-channels and between the
primary bundles (corneal tubes of Bowman), and in large numbers in
the tracts between the larger bundles. They are mostly round, some-
times club-shaped, never pointed at two extremities as an elongated
shuttle-shaped mass (that is, never spindelformig, spiessartig). A small
minority consist of a double body formed by two rounded globular
masses joined by a smooth isthmus. When stained by hfematoxylin,
nuclei are found in either end, but not in the isthmus. The author
infers that we have here a corpuscle in process of division.

In rabbit corneas, in which inflammation has lasted about a week,
some white corpuscles are seen with uneven contour ; and bulging
outwards from, or lying close beside, them are bodies evidently nuclear,
and which are affected by osmic acid and subsequent staining with red
aniline, in a manner identical with the red blood-corpuscles seen in
blood-vessels in the same preparation. The identity of the escaped
nuclei with red blood-corpuscles is shown by a comparison of their
respective size, evenness, colour, and contour.

The author infers a production of red blood-corpuscles in inflamma-
tion from the nuclei of the white blood-cells.

In observations on human blood, and that of the mouse, by staining
with hfematoxylin, he has found that while the great majority of the
red corpuscles do not quickly stain in a weak solution, there are some
which at once stain a deep blue, and that there are white corpuscles
in which a narrow protoplasmic margin encloses a deep blue nucleus
similar in contour and size to the stained red corpuscles. Amongst
the red corpuscles of tho frog are a minority which are recognized as
being red corpuscles by their size, smooth contour, and absence of
granulation, but in which there is no hfemoglobin, and the nucleus
quickly stains blue in solution of hfematoxylin, like that of the white
cells.

Transitions occur in which a less and less capacity of staining on
the part of the nucleus takes place, pari passu, with an increase in the
colour characteristic of hfemoglobin in the body of the cell. In the
fully developed red corpuscle, the nucleus stains only after it has been
for some time in contact with a weak solution of hfematoxylin.

The author has observed in the blood of the mouse foetus the nuclei
of the nucleated red blood-cell escape from tho larger cell, and then
become indistinguishable in form and appearance from the small red
corpuscles of the mature animal present in the blood under exami-
nation.

These observations, taken in connection with the bodies that are
formed in the spindle-cells and white corpuscles in inflammation, sup-
port, as the author believes, the doctrine of Wharton Jones, in regard
to the formation of the red blood-corpuscles.

The mode of formation of capillary blood-vessels he believes to be
identical in inflamed and in fa3tal tissue. In studying this subject he
has found special advantages from the use of osmic acid, with or without
subsequent staining in hfematoxylin. The stages in this formation
are as follows.

24

PROGRESS OF MICROSCOPICAL SCIENCE.

(a) The spindle-cells enlarge and contain several nuclei which can
be identified, whilst within the cell, as being of a similar nature to
red blood-corpuscles. A current of blood-plasma from the nearest
vessels passes, at the same time, into the interfibrillary space in which
the spindle-cells lie.

(b) The nuclei escape from the spindle-cells into this space, where
they are indistinguishable in appearance from the ordinary red blood-
corpuscles.

(c) By a process of diapedesis the formed elements of the nearest
blood-vessels pass into this space and the circulation is established.

Various appearances lead the author to suppose that the fibrine of
the plasma solidifies on the outer surface of the current and forms the
substratum of the new vessel, and on this substratum the white blood-
corpuscles fix themselves and spread out as an epithelium.

From interfibrillary spaces in the inflamed cornea, in wdiich forma-
tion of blood-vessels -was actively taking place, the author has isolated
white corpuscles in various transition stages towards the appearance
and shape of epithelium ; and, from rapidly enlarging vessels, cells
which, from their form, he believes to be transitionary to that of smooth
muscular fibre.

As the new capillary forms, the enlarged spindle-cells decrease
to their ordinary size.

In preparations of blood-serum of the frog sealed up, after a few
days, the hfemoglobin may be observed to assume special forms inside
the corpuscle, or to disappear from it, and so produce changes in the
appearance of the corpuscle identical with those described by Arnold
as taking place in the tongue of the living animal after diapedesis.

The above observations were made chiefly on the cornea of the frog
and rabbit ; and the inflammation was mostly produced by solid nitrate
of silver, the passing of a thread, and the application of methylated
alcohol.

In the winter frog ( Bana esculenta), cauterized in the centre of the
cornea, the first entry of white corpuscles attributable to inflammation
was observed, after forty-eight hours, in the wider spaces near the
limbus. After four days they could be observed in considerable
numbers, and 2-6 could be seen in one so-called space (lacuna).

The Heart of the Snail. — Dr. M. Foster and Mr. Dew-Smith, who
have been conducting some interesting physiological experiments on
the snail’s heart, give the following account of its structure.*

While the auricle is a sac, with quite thin and smooth walls, the
bundles of fibres in the ventricular walls bulge out largely into the
cavity, and are so arranged that the ventricle has the same spongy
structure as that of the frog and many other animals. Neither in the
auricular nor ventricular wall can the presence of any nerve-cells, or
collection of nerve-cells in the form of ganglia, be detected, whether
in fresh specimens or in those treated with various reagents. The
interlacing intricately-arranged bundles of fibres are composed of a
granular protoplasmic-looking tissue, quite unlike the ordinary mus-

* Vide ‘Proceedings of the Royal Society,’ No. 1G0.

PROGRESS OF MICROSCOPICAL SCIENCE.

25

cular tissue of the body, and in many ways resembling the cardiac
tissue of vertebrates. The walls are thickly studded with nuclei, some
of which possibly belong to an external tesselated epithelium. Other
nuclei are undoubtedly the proper nuclei of the contractile elements,
and the remainder seem to be of the nature of connective tissue.
Of none of them can it safely be said that they are the nuclei of
nerve-cells. Molluscan nerve-fibres might undoubtedly, unlike ver-
tebrate medullated nerve-fibres, easily escape detection ; but Mr. A.
S. Lea, of Trinity College, carefully examined for us the whole of
both the auricle and ventricle without discovering any distinct
nervous structures. He also went systematically over the margins of
both the aortic and pulmonary orifices, but could find no nerves
running into or out of the heart. In no other way could nerves be-
come connected with the heart. And, opposed as it may seem to
general experience, and still more to recognized opinions, we are led
to the conclusion that the heart of the snail has no nervous connection
with the rest of the body ; nay, more, that it has within itself no
distinctly specialized nervous mechanism, but that its contractile ele-
ments are composed of protoplasm, arranged, it is true, more or less
in fibres, yet otherwise but slightly advanced in differentiation.

Structure and Motion of the Spermatozoa. — These have been tho-
roughly investigated by Dr. T. H. Einer, who has published an im-
portant paper on the subject. He says : — The spermatozoa of dwarf
flying-mice show peculiarities which have also been observed in other
mammalia. The head and centre of these spermatozoa are unusually
broad, and are not continuous, but are interrupted by a very fine
thread, which is sometimes quite long, so that this thread can for
convenience bo called the throat. In the night-flying mouse this
thread is *0007 of a millimeter in length. In those cases where there
is no throat to be seen, there is at least a division in the body, and
we can easily suppose ono to exist, but our lenses are not powerful
enough to reveal it. A small line is seen in the middle of the centro,
continuing through the throat into the head and anterior extremity.
Sometimes this fine line can be seen as a separate line as it passes
through the throat-piece.

On the spermatozoa of Vesperugo pepestrellus, cross-lines are often
seen upon the tliroat-piece, dividing it into three or four square pieces,
held together by the line central thread. On others of the same indi-
vidual, this appearance is not seen. The addition of improper fluids
arrests the motion of the spermatozoa, and then these peculiar mark-
ings are no longer seen. In other species of mammalia, something of
the above structure could be found, viz. in horses, mice, and guinea-
pigs, oftener in cattle and Erminea mustela ; also sometimes in the
dog and cat.

In man he has often failed to find the line in the middle piece,
but the fine joints were frequently made out in the throat-piece.

The author has not seen the central thread in the head or centre-
piece of the spermatozoa of any mammalian in perfectly natural semen.

But some observations on not quite fresh semen seemed to show
that the central thread in these parts was masked in the fresh state

26

PROGRESS OF MICROSCOPICAL SCIENCE.

by something opaque ; and in every case of dog’s spermatozoa and in
a single case of man’s, where no central thread was seen, it could be
rendered visible. On the spermatozoa of the cat and hare there is a
bound-up appearance at the situation of the middle piece.

These general observations, together with the conduct of the sper-
matic elements of the flying mouse, show that the central thread must
be a peculiar element of the spermatozoa of mammalia ; and that the
middle piece consists of a central thread and of a protoplasma cloak
covering the same, which cloak is very often divided into little cubes.
This cloak is a remnant of the original formative cell of the sper-
matozoa. This appearance is common also on normal spermatozoa,
and is often crowded in rumples on different parts of the middle piece,
especially on the anterior end.

The tail also of mammalian spermatozoa consists of a fine thread
and protoplasma covering which is wanting in the extreme end of the
tail. We can follow the centre thread in some flying mice quite to
the end of the tail.

In the night-flying mouse, cat, and hare, the extreme end of the
tail is thicker than the central thread, and is always, in all mammals,
thicker than the very thin throat.

Secondly, the author speaks at length of the motion of these bodies,
their kind and cause.

In the triton and salamander the spermatozoa have a finny edge
running along the whole length on both sides. These edges move in
screw-like windings commencing at the back of the head and extend-
ing to the tail in quick succession, and a steady and uniform motion is
imparted to the body.

In spermatozoa which have no finny edge the forward motion
is produced by rapid turning upon the long axis. The extreme end of
the tail goes round in circles, and in this way turns the whole body.
The rate of propulsion is in proportion to the rapidity of tail-rotation.
The tail does not always turn in the same direction. When turning
very slow the rotations can be counted.

The author finally says : — The motion of the spermatozoa of mam-
mals and other vertebrates is on the principle of a screw. The
streams in the protoplasma rush to the end and cause the end to
rotate, whence the whole body is turned and the forward motion pro-
duced.— Virch. £ PhysiJc. Med. Ges.' in Wurtzburg, vi., 3, p. 93.

Observations on some Marine Tlhizopods. — At the meeting of the
Academy of Natural Sciences of Philadelphia, on March 16, Professor
Leidy remarked that he had spent a short time last August at Noank,
on the coast of Connecticut, where Professor Baird was then engaged
in pursuing his inquiries and investigations as United States Com-
missioner of Fisheries. Through the kindness of Professor Baird
he had been enabled to make a few observations on some marine
Bhizopods.

Some years ago, on the beach at Newport, K.T., he had noticed that
the ripple marks of the sand were crested with white particles, which
could be scraped up by the handful, and which he at first viewed as
the pulverized debris of various calcareous shells. On closer exami-

PROGRESS OF MICROSCOPICAL SCIENCE.

27

nation the material was found in large proportion to consist of the
dead shells of Foraminifera. The immense quantities of these remains,
extending in innumerable ridges over the broad expanse of the beach,
had led him to suspect that he would find them living in the greatest
jirofusion in the dredgings off the coast of Noank. In this view he
had been disappointed, though many living individuals were obtained
in dredging, adhering to liydroids, sponges, and the roots of fuci. The
number of species observed was small, though the individuals of several
of them were numerous. In the best condition, and especially abun-
dant, were two Foraminifers, a Miliola, and a Rotalia, exhibiting some
variety of form.

The Miliola resembles the Quinqueoculina mcredionnlis of Dorbigny,
and is probably the same species. The shell, from A to ^ of a line
in breadth, is white and more or less translucent, or is colourless and
transparent. It exhibits five compartments or cells, in the mouth of
the last and largest of which there is a blunt, conical tooth. The
interior soft structure was yellowish brown, or pinkish brown, darkest
in the smallest cell, successively lighter in the others, and sometimes
nearly colourless in the last or largest cell. In the last cell, and less
frequently in the second cell, the soft matter exhibited many globules
of transparent, colourless liquid. In the active condition the animal
protruded a multitude of exceedingly delicate pseudopods, which, radi-
ating from the mouth, ramified and frequently anastomosed in the most
intricate manner, as usual among Foraminifers.

The Rotalia is a beautiful, spiral, many-chambered shell, from the

to the { of a line in breadth, and strongly resembles the Rosa-
lind varians, as represented in fig. 8, plato iii., of Schultze’s Poly-
thalamien. The shell is white and more or less translucent, and is
composed of from twelve to eighteen cells. The soft structure within
is dark reddish or yellowish brown in the smallest cells, light brown
or yellowish in the larger cells, and faintly yellowish or colourless in
the largest cells. Pseudopods radiated everywhere from the minute
pores of the shell.

A few Polythalamous shells were observed, which appeared to be
composed of particles of sand cemented in the same manner as in the
fresh-water Difflugians. One of them was a spiral shell, like a Rotalia,
composed of eighteen cells, and measuring about \ of a line in
breadth. The soft structure within the smallest cells appeared to be
amber-brown.

Another of these arenaceous shells resembled in its shape and the
alternation of the cells the Textilaria agglutinans of Dorbigny, of the
West Indies. A specimen of thirteen cells was about the T\j of a
line long by TTff of a line at the broad end. The soft structure was
reddish brown within the smallest cells, becoming successively lighter
in the larger cells, until in the last or largest it was colourless, or
nearly so.

A third form consisted of a straight or slightly bent series of cells,
for the most part oblate spheroidal, and successively increasing in
size. The first cell is globular and larger than the few succeeding
ones. The last or largest cell is more of a conical form. The interior

28

PROGRESS OF MICROSCOPICAL SCIENCE.

structure was faintly yellowish or nearly colourless. A specimen of
eighteen cells was \ of a lino long, with the last cell about 2V °f a
line in diameter.

An interesting Rhizopod, not pertaining to the Polythalamous
foraminifers, to which my attention was directed by Professor
Verrill, frequently occurred in the mud dredged off the Connecticut
coast.

The same creature is referred to by Professor Yerrill in the Report
of the Commissioner of Pish and Fisheries for 1871 and 1872, page
503, as being extremely abundant in the clear silicious sand dredged
from Vineyard Sound.

The creature was discovered by Dr. Sandahl in the Bohnslaiis
Archipelago, and is described in the Ofvers. K. Vetensk. Ak. Fork.,
Stockholm, 1857, 301, under the name of Astrorliiza limicola. It is
also referred to in Thomson’s £ Depths of the Sea,’ p. 75, as occurring
in the Atlantic ooze off the Faroe Isles.

The case of this Rhizopod is constructed of angular particles of
quartz sand, cemented by tenacious matter mingled with the finest
dark-coloured mud. The body of the case is discoid or lenticular,
with a number of short cylindroid processes radiant from the margin,
giving the case altogether an irregular stellate form.

Sandahl describes the shell as exhibiting scattered yellowisli-
hrown spots, unequal, irregular, and somewhat shining. These spots,
in the specimens examined by me, are due to the translucent quartz
particles through which the yellowish colour of the interior soft
structure of tho animal is seen. Sandahl gives the number of radii
from 10 to 15, and the size of the case from 3 to 4 lines. Our
specimens measured from 2£ to 4 lines, and exhibited radii from G to
13 in number.

The interior soft substance of the little mud stars is a viscid,
mucoid matter. The ectosarc is colourless. The entosarc was
granular and yellowish, sometimes containing ova-like bodies, with
darker yellow or orange-coloured contents. Besides these the
entosarc contained clear globules and a multitude of diatoms, princi-
pally a species of Coscinodiscus.

He failed to see the Astrorliiza in a very active condition, pro-
bably from the hot summer weather too quickly giving rise to
decomposition in the material collected. Only in two instances did he
discover the animal with a number of delicate filamentous pseudopods
projected from the processes of the disk. The pseudopods as seen,
and as represented by Sandahl, are like those of the Foraminifera.

In the single-chambered character and structure of the case,
Astrorliiza resembles the fresh-water Difflugia, but differs in having
many orifices, to protrude the pseudopods, instead of a single one.

American Observations on Stephanoceros. — This animal, which has
been so well worked out by Mr. Cubitt in these pages, has recently
had American attention devoted to it. In the ‘ Proceedings of the
Philadelphia Academy of Sciences ’ for April, 1875, Mr. C. Newlin
Peirce exhibited drawings of a specimen of an aquatic animal,
belonging to the genus Stephanoceros, which had been recently

PROGRESS OF MICROSCOPICAL SCIENCE.

29

observed by him. In doing so, lie said be was induced to bring it
before the Academy because it was, he believed, rarely met with in
this country, and had not been previously here described.

In its main characteristics, such as spiral carapace or case, five
tentacle-like lobes armed with cilia, or, more properly, sette, eye-spots,
jaws, stomach, &c., it corresponds with the description given by Mr.
C. Cubitt in his paper entitled “ Observations on the Economy of
Stephanoceros,” in the ‘Monthly Microscopical Journal,’ vol. iii.,
1870, p. 242 ; but in addition to that very full sketch of this
interesting object, there were some points of interest not there
recorded. First was the great length of setie or bristles projecting
from the ends of the tentacles (only to be seen by esjiecial care in
focalizing with the lens), these overlapping each other formed a net-
work in which were entrapped Paramcecia of various sizes, as many as
forty having been observed there at one time. And by virtue of these
long sette the animal’s facility for procuring prey was greatly
enhanced.

These minute objects which served as food were by a spasmodic
effort of the bristles gradually brought within the arms, and from
there, with this continued spasmodic movement which has been
described by Mr. Cubitt, were brought within the vortex induced by
an arrangement of cilia around the mouth, which, unlike the sette on
the tentacles, were, while the animal was feeding, kept in a whorl.

The action of the sette on the lobes of the Stephanoceros is spas-
modic ; it creates no vortex, and it is only by actual contact with these
sette that floating particles are whipped within the area enclosed by
the lobes, where, by the same whipping action, they are twitched from
point to point, irregularly downwards, until they come within the
range of a vortex, which is due not to any action of the sette, but to a
range of minute cilia in the funnel, distinct from the foraging
appliances.

For two weeks the animal under observation fed voraciously.
The last few days of this time granular layers were rapidly
deposited on each side of the body just within the case, until the
upper part of the carapace was distended with this accumulation.
For twenty-four hours following this condition but little or no food
passed into the digestive cavity ; any infusoria or other foreign sub-
stance accidentally coming within the tentacles being immediately
expelled by a sudden constriction of these organs at their base.

It was evident from appearances that some change was about to
take place. The animal, at first very sensitive, withdrawing into its
cell on the slightest jar of the table on which the instrument was
placed, now but seldom contracted its retractile muscle even though
the zoophyte trough, in which it was examined, was quite violently
tapped.

On the sixteenth day of observation it was unavoidably left for a
few hours ; on returning to it the tentacles, with the above-described
accumulated dark mass, were found to have left the original case and
were attached to a portion of the plant beneath the branch to which it
(the original case) adhered. It now presented somewhat the appear-

30

NOTES AND MEMORANDA.

ance of an animal figured and described by Pritchard as a young
Stephanoceros, a dark globular mass with five spreading or divergent
tentacles, and at the distal extremity a very slight prolongation by
which it was attached to a plant-stem by an almost invisible thread,
devoid entirely of any cell or carapace. Not long, however, was it
destined to remain in this nude condition, for in twenty-four hours
appearances of a cell were visible, and within three days it was
domiciled in as beautiful a spiral case as the one it had left. Its
contractile muscle developing rapidly with the length of the cell, in a
few days it presented to the observer all the peculiarities of the
parent, and within two weeks was again ready for another change such
as is above described, and which was accomplished with a similar
result. The Stephanoceros being too high in the scale of animal life
to propagate by gemmation or division, the process above portrayed
can have but a remote influence upon reproduction, as there was no
multiplication by this change.

The original cell with its retracted body within, though remaining
for weeks in an apparently perfect condition, was not seen to increase
or in the least to change — the growth-force seemingly being confined
to the detached head and its accompanying organs.

Dr. Leidy stated that he had never seen specimens of Stephano-
ceros until they were shown to him by Mr. Peirce.

NOTES AND MEMORANDA.

r Wenham’s Reflex Illuminator. — Mr. Samuel Wells writes as
follows to the ‘Boston Journal of Chemistry’ (June, 1875): — Last
September I received this ingenious illuminator from London, and
examined several slides with its aid. The beautiful effect of a bright
and clear illumination of the object, shown on a dark background, as
described by the inventor and by Mr. Slack, was very interesting and
instructive. I had then but few slides on which I could use it, and
laid it aside for further investigation at a future time.

Mr. Wenham describes it in the ‘Monthly Microscopical Journal,’
vol. vii., p. 236. It was designed for the illumination of such objects,
mounted dry, as adhere to the surface of the slide, by rays of light of
such obliquity that they cannot be transmitted beyond that point.
The illuminator being connected with the slide by a film of water,
the light passes through to the upper surface of the slide, and, if there
is no object in contact with the slide at that point, is totally reflected ;
if, however, a diatom or other object rests on the slide at the point
where the light strikes, the rays enter the object and are diffused by
it so that it becomes in effect self-luminous.

This appears to be the only use for the illuminator described by
the inventor. I have, however, lately used it for a different purpose,

NOTES AND MEMORANDA.

31

and with results quite surprising. While studying high-power objec-
tives of large angular aperture, I experimented with various methods
of illumination, and among others applied the reflex illuminator. I
find that j^tfme immersion objectives are capable of transmitting the
extremely oblique rays that pass through the illuminator, so as to
give a bright field when used on balsam slides. In dry mounts the
light cannot be transmitted beyond the upper surface of the slide, but
in balsam-mounted slides the light passes to the upper surface of the
cover and is there totally reflected. If an immersion objective is
adjusted and connected with the cover by a film of water, the total
reflexion will be destroyed, and the light pass through the cover and
water into the front of the objective. The ultimate direction of the
ray of light after passing through the illuminator is not changed by
the introduction of the different media (balsam, glass, and water), and
the angle at which it enters the objective must therefore be greater
than 41°. In examining Moller’s Probe-Platte, a balsam mount, under
these conditions, with light from a kerosene hand-lamp, I easily
resolved the Amphipleura pellucida ; so clear and decided were the
lines that with a power of 8000 they were still visible. I first obtained
this unexpected result with my Powell and Lealand ^tli, and the light
was sufficiently bright to render it possible to use a ^-inch eye-piece
and concave amplifier. As the yg-th lias the power of a ^th, I
obtained, by estimation, a power of 8000 diameters.

The resolution of this difficult diatom, as well as the Frustulia
Saxonica and Nitzschia curvula (Nos. 18 and 19 on the Probe-Platte),
far surpasses any that I have ever seen by artificial light, and rivals
the beautiful resolution obtained by monochromatic sunlight. With
this illuminator it is much easier to resolve the Amphipleura in balsam
than to resolve it dry with any other artificial illumination.

I find, however, as yet but few objectives capable of transmitting
light of such extreme obliquity through the back systems. The
Powell and Lealand y^th, as I have above stated, succeeds admirably.
My Tolies’ y^tli immersion gave only a dark field.

Of several others I have succeeded with only three : a T\yth made
several years ago, a four-system £th, and a four-system y^th, the last two
of recent construction, and all three made by Tolies, and all of course
immersion. I have not had access to Continental objectives of wide
angle. The three objectives of Tolies last named resolve the whole
of the frustule of the Amphipleura at once, while the Powell and
Lealand ygdh resolves only a part at one view, even when the whole
frustule is in the field. The advantages of the reflex illuminator in
thus furnishing light of greater obliquity than has been obtained by
other methods, seem to me worth considering by those interested in
testing the resolving power of objectives.

I find it advantageous to connect the illuminator with the slide by
glycerine, instead of water, as it does not evaporate. The higher
refractive power of glycerine makes no difference in the ultimate
direction of the light.

With high amplification the lines of the Amphipleura become
decidedly beaded, but do not separate into dots.

VOL. XIV.

D

32

CORRESPONDENCE.

Powell and Lealand’s ^th new Immersion Objective. — The

‘ Academy ’ (May 8) says of this glass : “ We have had an opportunity
of trying one made for Mr. Lettsom, and it is certainly a very
remarkable production, able to show very minute structures for which
much higher objectives have hitherto been employed. It has a con-
siderable working distance in proportion to the magnification it
affords with deep eye-pieces, and gives a wonderful view of diatoms
flat enough for its angle of aperture and contiguity to the object. It
has also sufficient penetration for small live objects, and has plenty of
light with D and E eye-pieces, which cause no noticeable deterioration
of its performance when, as should always be the case with high
powers, an achromatic condenser is employed.”

CORRESPONDENCE.

What are the Characteristics of Frustulia Saxonica?

To the Editor of the ‘ Monthly Microscopical Journal

Denstone, May 18, 1875.

Sir, — I am afraid the ‘ Monthly Microscopical Journal ’ (vol. ix.,
p. 86) must have made some mistake, and have misrepresented Dr.
Woodward in that paragraph headed “ Frustulia Saxonica as a
Definition Test.” What is there said is by no means very clear ;
but it certainly does make him assert one of two things : either (1) that
Frustulia Saxonica is a one-lined object (i. e. has transverse, but no
longitudinal lines) ; or (2) that, though it undoubtedly has transverse,
and may possibly have longitudinal lines as well, no one as yet has
succeeded in seeing the latter, but that those who fancied they saw
them, as Dippel and others, have been deceived by “ diffraction
phenomena.”

If either of these interpretations represents his real views, I would
request Dr. Woodward of his patience and courtesy to permit me to
make a few remarks.

In the summer of 1872 I called upon Herr Seibert at Charlotten-
burg for the purpose of procuring one of his high-power immersion
lenses. On this occasion, after letting me see what his manipulative
skill could accomplish in resolving the tests I had brought with me —
and amongst the first was an extremely fine-lined specimen of Frustulia
Saxonica— he next showed me a couple of very beautiful photographs
of that diatom, one of which exhibited the transverse, and the other
the longitudinal lines, with far more clearness, sharpness, and dis-
tinctness than the printer will be able to reproduce the words I have
here written.

Some ten days later I called upon him again between eight and
nine in the evening, and before he would let me go he insisted on
showing me what the glass I had selected could do on his own private

CORRESPONDENCE.

33

slide of Frustulia Saxonica. This time, instead of bright sunlight, his
means of illumination were about as bad as bad could be — in fact,
nothing but his wife’s drawing-room lamp, with a ground-glass top.*
Nevertheless he succeeded in showing me with my newly purchased
objective the longitudinal lines as plainly and visibly as any of us are
ever likely to see our own faces in our looking-glasses.

Again, in the summer of 1873, when a resident of Dresden, I
had a visit from Dr. L. Rabenhorst, the well-known author of the
‘ Siisswasser-Diatomaceen,’ and showed him, at his own request, a
variety of test-diatoms, such as Navicula crassinervis, Surirella gemma,
&c., &c., and amongst these one special slide of Frustulia Saxonica,
which exhibited both lines so clearly and beautifully as to draw from
him the usual German exclamation of delight and admiration,
“ Wunderschbn ! ” With Navicula crassinervis he was less satisfied.

Now, bearing in mind that Dr. Rabenhorst is both the discoverer
and namer of the diatom in question, I will put it to Dr. Woodward,
even supposing that Herr Seibert could twice impose upon me for
Frustulia Saxonica something that was not, whether I could have any
chance of imposing upon Dr. Rabenhorst after the like manner, or
upon Herr Alex. Lindig, late Optician to the Court of Saxony, to
whom I showed it three nights later, who may be credited with the
ability to recognize the markings of a well-known Saxon diatom when
he saw them on a slide bearing his own label.

On turning to my own MS. note-book on test-diatoms, no portion
of which was written later than the year 1872, I find the longitudinal
lines of Frustulia Saxonica there described as “ slightly wavy, but
considerably less wavy and less apparent than in Bhomboides.” The
plain truth is, I never knew there was any special difficulty about
these longitudinal lines till I saw it so stated in the (supposed) extract
from Dr. Woodward’s paper. I will add further, that on the evening
of the 14th of this month, when it first occurred to me to write on
this subject, I put upon the stage of the microscope the same slide I
had shown to Dr. Rabenhorst and Herr Lindig ; and it so happened
that the very first shell that came in front of the objective exhibited
precisely the longitudinal lines, and as plainly as I could ever wish to
see them. Of course I used no condenser. I have always regarded
that article, when employed on high-power delicate tests, as a mere
optician’s booby-trap. Its only use there is to disguise the optician’s
faulty workmanship and to make a bad glass pass muster for a good
one.

The reader would do well to see what Dr. Schumann f has to say
on this point, when about to attack that intricate customer Navicula
lata. Advanced microscopy under such circumstances is open to the
gravest suspicions.

I had also no difficulty in bringing into view those wide-spaced,

* I intend to forward a copy of this number to Herr Seibert, at his present
address, so that my statements may come before him for correction, if I have said
the thing that is not. I am sure he will be not a little surprised to learn that
Frustulia Saxonica has no visible longitudinal lines.

t ‘ Die Diatomeen der hohen Tatra,’ p. 73.

D 2

34

CORRESPONDENCE.

spurious lines alluded to by Dr. Woodward, which some persons have
nicknamed “ ghost lines.” As the frustule was already lying vertical,

I had merely to move it about an inch and a half to the (apparently)
left side of the objective.

Fortunately, the dispute — if there be any dispute — is one that can
be easily settled. Either Dr. Woodward may forward a letter to
Herr Seibert, “ Optisches Institut, Wetzlar,” — and from my know-
ledge of Herr Seibert’s obliging disposition I am sure he will readily
send him a copy of the photographs shown to me, — or, if Dr. Wood-
ward prefer it, I will forward to Mr. Lealand (of the firm of “ Powell
and Lealand ”) the slide I showed to Dr. Rabenhorst ; and then, if
Mr. Lealand cannot see the longitudinal lines, the case is ended.

I may as well mention at once that my collection of Frustulia
Saxonicas, which is a pretty extensive one, ranges from specimens
having lines closer and finer than those in Amphipleura pellucida to
such as exhibit lines as coarse and strongly marked as those in
Mr. Norman’s Nitzschia sigmoidea. Thanks to Dr. Schumann’s admi-
rable pamphlet, we now know that this great diversity in the same
species depends on differences of elevation of the diatom’s habitat,
that is, on differences of temperature, inasmuch as there is a fall
of one degree of Reaumur for every 600 feet of elevation above the sea
level. He further tells us (pp. 7, 17) that he found Frustulia
Saxoniea at various elevations, from 4000 to 6454 feet above the sea
level. See also pp. 85, 93.

One word more about slides. Many a man fancies he has got a
bad glass when he has really got a bad slide. There are slides and
slides ; and, unfortunately, the bad ones are in a terrible majority,
as bad things usually are. Something of this sort has been at the
bottom of Dr. Woodward’s (reported) failure. If he is rightly reported
as having failed, my explanation is, that he failed where everyone
else would have failed, and has merely been wasting his time on a
bad slide.

I am the more inclined to adopt this view from Dr. Woodward’s
mention of Moller; for I hardly need say that Moller, in the matter
of test-diatoms, is the very worst guide anyone could possibly take.
He seems indeed not to have the slightest idea that any test-diatom
can require for its resolution any position other than horizontal
or vertical. It is also notorious that, if a customer applies to him for
Navicula crassinervis, he sends Frustulia Saxoniea labelled “ Navicula
crassinervis ” ; and if the customer wants Frustulia Saxoniea he sends
it labelled “ Frustulia Saxoniea.” Wrong naming seems to be his
speciality.

It is quite true that Dr. Schumann * says (in which point I do not
agree with him) : “ Frustulia Saxoniea Rabcnh. Alg. p. 227. It
appears in the following forms : —

“1. Nav. crassinervis Breb. Syn. I. p. 47. xxi. 271. Beitr. p. 10,
II, 13 c.

“2. Nav. empidata Ktz. Syn. xvi. 131. Beitr. II, 16 a.”

But to say that Frustulia Saxoniea has as its sub-species Nav. crassi-
* ‘ Die Diatomeen der holien Tatra,’ p. 79.

CORRESPONDENCE.

35

ner vis and Nav. cuspidata is something very different from saying
that the two things are identical , as Moller says in his printed expla-
nation accompanying his Diatomeen-Probe-P latte : —

“ 18. Navicula crassinervis Breb. = Frustulia Saxonica Rabh.”

Let the reader compare Dr. Rabenhorst’s drawing of Frustulia
Saxonica* with the drawing of Nav. crassinervis in Smith’s Synopsis.
I may here remark that Dr. Schumann’s own drawing of Nav. cras-
sinervis (plate iv. fig. 57) is markedly diffei'ent from Fr. Saxonica.
It is also very strange that Dr. Rabenhorst himself, when he saw
them both in quick succession at my rooms in Dresden, had no sus-
picion that they were identical. Surely he ought to know. And now
to revert to what I have said about position.

So far as my experience goes Navicula crassinervis is not readily
resolved unless it lies perfectly horizontal.

Nav. rhomboides is perfectly resolved only when the (apparently)
right-hand apex has an elevation of about 9°.

With Frustulia Saxonica it is exactly the reverse. It is fully
resolved only when the (apparently) left-hand apex is elevated about
15°. And this will serve to distinguish them. In Rhomboides also the
transverse lines are much closer than the longitudinal, whereas in
Frustulia Saxonica it is just the reverse. Their general contour,
again, is different. In Rhomboides the marginal edge runs pretty
straight from the apex to the centre, where the frustule exhibits an
obtuse angle. In Frustulia Saxonica the marginal edge forms a fairly
continuous curve, and the ends are considerably sharper. There are
also some characteristic differences in their central knot, which, how-
ever, are less apparent.

I have entered into these minute particulars lest anyone should
suspect that Messrs. Seibert, Rabenhorst, Lindig, and myself have
been confounding Frustulia Saxonica with Rhomboides.

In conclusion, I will beg Dr. Woodward not to interpret any word
or sentence I have here used as intended to detract from his well-
earned reputation as one of our greatest living microscopists, or as
provocative of controversy, which I cordially detest. If he finds any
expression that can bear such an interpretation I shall wish it unsaid.
For my own part, I see no reason wThy matters microscopical may not
be talked over as amicably as the state of the weather or the prospects
of a good harvest.

Yours faithfully,

W. J. Hickie.

Zeiss’s and English small-angled Objectives.

To the Editor of the ‘ Monthly Microscopical J ournaV

May 18, 1875.

Sir, — At the last meeting of the Royal Microscopical Society, one
of the Secretaries, Mr. Slack, read a very interesting paper on the
above subject, and I have no doubt that all microscopists will be
thankful for such a subject having been brought forward afresh.

* 1 Die Siisawasser-Diatomaceen,’ plate vii. fig. 1. M

36

CORRESPONDENCE.

Dr. Carpenter lias advocated, for many years, small-angled objec-
tives “ for tbe ordinary purposes of scientific investigation,” and
“ .... for almost every purpose except tbe resolution of diatom-
tests, objectives of moderate angular aperture are to be decidedly pre-
ferred.” In bis fifth edition of ‘ The Microscope ’ (published with
the assistance of Mr. Slack), he says, page 208, “several opticians
now make objectives of these limited apertures (4- inches of 40° and
iths of 75°), of excellent quality, and very moderate price,” and page
819 — “the excellent small-angled 4th and ^th made by Mr. Swift
expressly with this view.” *

Messrs. E. and J. Beck supply their T%ths and iths with both
small and large angular apertures, besides the objectives of their
“Popular” and “ Universal ” series, in both of which the angular
apertures are small.

Messrs. Powell and Lealand supply ^ inches with angular aper-
tures of 40° or 70° ; £ths of 95°, 130°, or 145° ; |ths of 140° ; but I
am informed they will supply ^ths with an angular aperture of 100°
if desired.

Messrs. Eoss and Co. supply their patent J inches, -/^ths, and -I-ths,
and will supply most likely, “ later on,” their ^tlis, with both large
and small angular apertures.

This clearly proves what Mr. Crisp said at this month’s meeting
of the Eoyal Microscopical Society: “ Opticians are not to be blamed
for making their objectives with large angles. The blame entirely
rests with microscopists, who want to be educated. . . . Objectives
are made with large angles to meet the demand.”

If the above facts are taken into consideration, and also that the
leading English opticians will, no doubt, produce objectives of any
focal length and angular aperture desired, I do not see the reason
why foreign objectives should be brought forward in such a prominent
manner to the detriment of English ones. The cheapness of some of
the foreign objectives weighs, certainly, very much in their favour ;
but to balance this there is the great uncertainty as to what quality
of objectives one may get when ordering them, if the opportunity of
selection is not afforded. The best foreign objectives are only obtain-
able under the most favourable circumstances.

I have received some very good objectives from one Continental
optician, but have also been very glad to dispose of objectives received
from two other Continental opticians as soon as I had examined their
performances, which were certainly much less than “ moderately bad ” ! !

I do not believe that the most strenuous advocate of foreign
objectives is prepared to maintain their superiority, or even their
equality, to the objectives produced by the three leading firms of
London opticians.

I am, Sir, your obedient servant,

A. de Souza Guimaraens.

* "Vide also Mr. Slack’s letter, ‘M. M. J.,’ vol. xi., p. 2G4, June, 1874, &c.

PROCEEDINGS OF SOCIETIES.

37

The Mode of Recording Absorption Spectra.

To the Editor of the 1 Monthly Microscopical Journal.’

New York, May 26, 1875.

Sir, — I write in advocacy of Mr. Sorby’s proposal that the absorp-
tion spectra should be recorded in wave-lengths, having employed
this plan for nearly two years. I have, however, abandoned the prism,
and observe all spectra with the diffraction grating, and obtain the
wave-length directly by the well-known formula A = 8 x sin. 6. I
have tried a number of gratings both transmission and reflecting, and
find that a transmission grating containing between four and five
thousand lines to the inch, is best adapted to absorption work. The
one I now use contains 4320 lines and was ruled upon Mr. L. M.
Rutherford’s machine. With this grating the value of 0 is 5° 45" for
the D line.

I enclose a diagram which I use in recording spectra. Will you
have the kindness to forward it to Mr. Sorby ? and oblige

Your obedient servant,

Henry G. Piffard, M.D.

[On this letter being forwarded to Mr. Sorby, the following reply
was transmitted.]

2, Cambridge Villas, Buxton, June 10, 1S75.

Dear Sir, — I am much obliged by your having sent to me Dr.
Piffard’s letter. I have long known the special advantages of a
diffraction grating, but of course prisms have other very important
advantages, and are in many respects made more convenient to use
with a microscope. What led me to propose the method described in
my late paper was the belief that by observing with a prism and then
so easily reducing the observations to wave-lengths, we should to a
great extent unite the merits of both systems, and avoid their dis-
advantages.

Yours very truly,

H. C. Sorby.

PROCEEDINGS OF SOCIETIES.

Royal Microscopical Society.

King’s College, June 2, 1875.

Charles Brooke, Esq., F.R.S., Vice-President, in the chair.

The minutes of the preceding meeting were read and confirmed.

A list of donations to the Society was read, and the thanks of the
Society were voted to the donors.

Mr. J. W. Stephenson said he had placed upon the table a number
of copies of a scale to be used for the measurement of the angular aperture
of objectives. He had caused them to be printed, thinking that they

38

PROCEEDINGS OF SOCIETIES.

might be useful to many persons who were interested in the subject,
and he had therefore much pleasure in offering them for distribution
amongst the gentlemen present. The scale (which was enlarged upon
the board by Mr. Stephenson for the purpose of explanation) was
printed upon a sheet of paper about 144 in. X 10 in., across which, at
about 1 inch from one end, a straight line was drawn ; and this line
was bisected by another straight line, which was extended to the
opposite end of the paper, and along which a scale of cotangents was
marked from 175° to 35°. (See p. 3.)

Mr. Slack suggested that if the paper was mounted upon a smooth
board, and two knife edges of ivory were substituted for the night-lights
used by Mr. Stephenson, the scale could be used in daylight, and he
thought with advantage over the lights.

Mr. Crisp was quite sure that by the time they met again in
October, Mr. Stephenson would have invented something much better
for the purpose than night-lights.

Mr. Wenham thought this had supplied a want : in principle it in
no way differed from the ordinary way, but was carried out rather
in a different manner. He was inclined to doubt whether this plan
would give perfectly accurate results, but he thought it would be
correct within a degree.

The President thought as there was a little difficulty in seeing the
very small images of the lights, it might be better to convert the
object-glass into a telescope by placing a lens behind it.

Mr. Wenham said that in using the ordinary sector for the purpose,
when a glass was properly stopped the angle could be determined very
accurately ; but with one not properly stopped there was no such sharp
demarcation, but the light would vanish away gradually almost up to
180°.

The thanks of the meeting were voted to Mr. Stephenson for his
communication.

Mr. Charles Stewart said that through the kindness of Mr. Badcock
he had lately been enabled to make an examination of that curious
creature known to them as Bucephalus polymorphus. (Drawings of
the above, together with his remarks, will be found at p. 1.)

Mr. Badcock thought there was one little point which Mr.
Stewart had omitted to mention, and this was a dark spot which he
had observed midway between the central tip of the creature and the
ventral orifice.

Mr. Stewart said he was under the impression that this dark spot
might be the three little concretions beftrre alluded to. The only
other thing which had not been mentioned was a problematical thing,
which he wanted to examine further before pronouncing an opinion
upon. Immediately in front, and dorsal to the sucker, there was a
considerable sized depression, having underneath it a space apparently
identical with the elongated space representing the water-vascular
system. As the creature was dying, he hardly liked to speak with
certainty about it, but thought it might be the anterior extremity of
this curved space.

Mr. Badcock said that another point of interest was the periodical

PKOCEEDINGS OF SOCIETIES.

39

times at which these creatures came forth ; he got a batch of them now
about once in every ten days : this was from the same mussel as he had
last summer.

Mr. Loy asked if Mr. Badcock had ever dissected a fresh-water
mussel and found any of these creatures in it, or whether he knew of
anybody who had ever done so. He had himself dissected a great
many, but had never yet been able to find any of them.

Mr. Badcock said he had never found any in a mussel, and never
found any near a mussel except once.

Mr. Slack asked if Mr. Loy had looked for any sporocysts ; he
thought all one could expect to find would be some minute white
threads in the liver and genital organs. From the translations and
drawings given in the ‘ M. M. J.’ for April, it would seem that previous
observers had left much to be elucidated, and Voir Baer had used too
low a power to enable him to make out the anatomical details which
Mr. Stewart had described.

Mr. Loy said he had got mussels of various kinds, and had obtained
them from different sources, but could neither find the creature nor any-
thing like it — not even the threads mentioned by Mr. Slack.

Mr. Badcock suggested that perhaps Mr. Loy had looked for the
creatures at the wrong time of year ; he found they disappeared
altogether during the winter months.

Mr. Loy said he looked for them in January, February, and March :
he had tried all sorts of mussels from all sources, and had never been
able to find a trace of anything resembling them.

The President thought it would be of much interest to determine
if possible the alimentary system.

Mr. Slack thought the sporocysts seemed the most interesting
things connected with these creatures ; it appeared that they branched
out and germinated, and cast off germs which resembled the early
stages of the parent creatures.

Mr. Badcock was afraid it would be premature to say that he had
traced them to a second stage ; but he might say that he had kept some
of them for some time in a bottle, and had found in place of them a
creature somewhat resembling the other, with the central body
surrounded by cilia, and having a rudimentary central tail. He had
on a former occasion attempted to bring one in this condition to the
Society for exhibition, but unfortunately it got crushed in coming.

Mr. Slack read a paper “ On the Use of Mr. Wenliam’s Beflex
Illuminator.” (See p. 5.)

Mr. Mclntire said he could speak to the difficulties attending the
use of the apparatus when used with an objective of more than 100°.
The suggestion about stopping down the angles was a good one ; some
very beautiful effects might then be produced.

Mr. Crisp thought the most convenient apparatus for stopping
down was the iris diaphragm.

Mr. Wenham inquired whether Mr. Crisp had done this in the
case of very high powers, because he thought in those cases it would
be apt to cut off the field in consequence of the diaphragm being so
much behind the conjugate focus.

40

PROCEEDINGS OF SOCIETIES.

Mr. Crisp said lie had tried it with a ~tli inch having the back cut
down very flat so tliat it could come very close to the hack lens.

Mr. Wenham hoped some ingenious member would invent some
form of diaphragm to suit it.

The President thought it might be possible to construct an iris
diaphragm of a number of thin strips of metal in such a way that it
could he expanded or contracted.

Mr. Wenham had thought of this plan, and also of making an
aluminium tube with a collar to run up and down the case, hut the
difficulty then was to get at it to work it when in position.

Mr. Slack asked if it would he difficult to make a kind of rotating
diaphragm for the purpose.

Mr. Wenham said that if it became a question of cutting through
the object-glass, he would rather use a slide than anything to rotate.

Mr. Slack said that in the case of Eupodiscus Argus the surface
was too much curved for any high-angled glass to show the object
properly, hut writh a low angle the piece that came into focus was
shown perfectly. Without penetration it was not possible to get a
projier idea of the structure.

Dr. Matthews said that he had very little to report concerning the
diatomaceous earth committed to him at the last meeting except a
series of failures. He had boiled some down in nitric acid, but still it
retained its shape, and when be crushed it the diatoms were also
broken. He gave some to Mr. Topping, and he seemed to he able to
do it perfectly, and had mounted a specimen. However, he was unable
himself to make out its species, and had therefore handed it to Mr.
Hailes, who in turn being also puzzled had sent it to Mr. Kitton, who
was himself uncertain as to what species of Orthosira or Melosira was
present. The specimen was exhibited under a microscope in the room.

Mr. Slack had also looked through the collection sent by Mr.
Hanks, and found amongst it many interesting additions to their slides
of minerals. There was also a very fine polychroic object — sesqui-
oxide of chromium.

Mr. Wenham asked Dr. Matthews if his difficulty arose from the
silicious character of the earth, as in that case he thought if it were
boiled in a weak solution of soda the silicious material would give
way.

Dr. Matthews said he had tried soda and potash three times, and
also repeated boilings in nitric acid, and had boiled it to dryness, hut
still unable to succeed.

The proceedings were then adjourned until October.

Donations to the Library since May 5, 1875 :

From

Nature. Weekly The Editor.

Atkenreum. Weekly Ditto.

Society of Arts Journal. Weekly Society.

Journal of tlie Linnean Society. No. 59 Ditto.

Journal of the Geological Society. No. 122 Ditto.

Monthly Notices, &c., of the Royal Society of Tasmania Ditto.

Walter W. Reeves,

Assist. -Secretary.

PROCEEDINGS OF SOCIETIES.

41

Medical Microscopical Society.

Friday, May 21, 1875. — Dr. F. Payne, President, in the chair.

Fatty Degeneration of Muscle. — Notes on this subject were read by
Dr. Kesteven. He observed that the expression “fatty degeneration,”
as usually employed, was a misnomer ; that the change is one in
which, as a matter of fact, fat plays no part at all. Instead of fatty
matter, the degenerated muscles exhibit a disintegration of the con-
tents of the muscle fibrils, obliterating their striation. Along the
centre of these are to be seen dark-brown or black granules of a pig-
mentary character, not removable by aether or alkalies. The change
begins and ends in the fibrils, and is very distinct from the fatty
condition, in which the fibrils retaining their striation are separated
by deposition of adipose tissue. The latter form of disease is more or
less associated with changes in the nervous centres, while in the
former it is not so. Preparations and illustrative drawings were
exhibited by the author, of muscular atrophy, pseudo-muscular hyper-
trophy, rupture of the left ventricle, infantile paralysis, and the so-
called fatty degeneration.

The President and several of the members took part in the dis-
cussion that followed.

Myelitis. — A paper on this subject, by Mr. D. J. Hamilton, was
read by the President. The author pointed out that much uncertainty
existed as to the real character of the various lesions of the spinal
cord, known as hardening, softening, sclerosis, disintegration, &c., and
more especially as to their connection with the secondary changes
depending on loss of the trophic influence by nerve-cells on the fibres
to which they are attached ; and as to their connection with inflam-
mation.

In order to elucidate the latter point, it was necessary to know
definitely in the first place what changes inflammation does produce
in the spinal cord ; and with this end the author made the experiments
recorded in his paper. His method consisted in first producing a
lesion known to be inflammatory, and then examining the morbid
appearances, all preconceived ideas on the subject being purposely
laid aside. All appearances were verified by abundant repetition, and
only those which were found to be invariable were recorded. The
experiments were conducted in Professor Strieker’s laboratory at
Vienna. The method of experimenting was : A small animal, as a
cat, having been narcotized, the spinal cord was cut down upon at the
junction of the dorsal and lumbar portions, and a thread passed
through for about an inch in a longitudinal direction. The wound
was now closed, and the animal killed after forty-eight hours, by
which time inflammation was abundantly set up. The cord was then
cut up into pieces an inch long, hardened in chromic acid and spirit,
and kept at a low temperature. Sections were made in a microtome,
stained with carmine and mounted in dammar.

When examined, the tissue at the seat of lesion was found broken
down, and showed numerous extravasations of blood ; but the true
inflammatory area was seen at a little distance from this, being gene-

42

PROCEEDINGS OF SOCIETIES.

rally most marked in the deepest portions of the anterior columns
and in the commissure. Changes were seen in the nerve-tubes, the
nerve-cells, and the neuroglia.

In the nerve-tubes the most remarkable changes were seen in the
axis cylinder, this being dilated at irregular intervals into large oval
swellings, from five to ten times its normal diameter, still contained
in the distended and attenuated nerve-sheath, and composed of a
transparent substance, deeply stained by carmine. These oval swell-
ings were sometimes connected together by the unaltered axis cylinder,
sometimes detached. In many of them evidence was seen of fissiparous
division, groups of smaller though similar transparent bodies being
produced, which appeared to spread beyond the original but now
empty nerve-sheath, and to invade the surrounding tissues, being then
identical with the so-called “ colloid bodies ” abundantly met with in
chronic affections of the spinal cord.

In the seat of most intense inflammation the bodies underwent a
further and more remarkable development, becoming granular, and
several nuclei being formed in their interior. The corpuscles then
presented the appearance of mother cells, and in some cases these
mother cells were broken down, and the young cells in their interior
were set free as pus-corpuscles.

The changes in the nerve-cells were less important, consisting
chiefly of swelling and molecular transformation, a condition often
described as an oedematous affection. In no case was division of the
nerve-cells observed.

The neuroglia was less altered than might have been expected, but
in many instances abundant nuclei were seen, the origin of which was
obscure.

Abundant evidence was seen of the emigration of leucocytes from
the blood-vessels, the adventitious sheaths being filled with them, as
in inflammation of other parts. Similar appearances were seen in a
case of syphilitic disease of the nerve centres.

After a brief discussion on the paper, Mr. Groves described and
exhibited Crouch’s improved fine adjustment for microscope stands,
made on the Continental model, in which great stability was combined
with easy and regular motion, the points of friction being reduced to
a minimum. He also described a centering sub-stage arrangement for
the same stand.

Quekett Microscopical Club.

Ordinary Meeting, April 23. — Dr. Matthews, F.R.M.S., President,
in the chair.

The President announced the death of Mr. Robert Hardwicke,
which had occurred since the last ordinary meeting, and passed a
high eulogium upon him. Mr. Hardwicke was one of the founders of
the club, and its Treasurer from the commencement, and allowed his
house of business to be used as its office. He also published the
Journal, was an active and useful member of committee, and greatly
advanced the interests of the club. A resolution expressive of the

PROCEEDINGS OF SOCIETIES.

43

loss sustained by the club was moved by Dr. Braitbwaite, and duly
carried.

Mr. W. W. Jones described an instrument for cleaning very tbin
covering glass without danger of fracture.

Mr. T. C. White made a further communication respecting the
salivary glands of the cockroach, and described an instance in which
the sac when dissected out was found filled with fluid containing
salivary corpuscles. He exhibited one of these sacs still attached to
the thorax, the whole being immersed in alcohol.

Dr. D. Moore read a paper, giving “ The results of some observa-
tions on the Bucephalus Haimeanus of M. Lacaze-Duthiers, and another
allied organism not yet named.” Soon after reading his last paper,
he found that the organism he had figured as the young of the cockle
had been fully described by M. Lacaze-Duthiers, in the ‘ French
Annals of Natural History,’ under the name of Bucephalus Haimeanus,
the other allied organism obtained from the mussel not having been,
so far as he knew, either described or named. The admirable resume
of the subject by one of the Hon. Secretaries of the Royal Microscopical
Society, which appeared in the ‘ Monthly Microscopical Journal ’ for
April, rendered the history which he had intended to give of previous
observations and conclusions unnecessary. He then gave a short
sketch of the life history of a Cercarian, Cercaria ephemera, described
by Siebold, which went through all its changes in certain water-snails,
whose skin it penetrated, in which it became encysted, and developed
into a perfect sexual Bistoma, whose eggs in the course of time pro-
duced the sporocysts or nurses, which were found to contain Cercarice
in various stages of development, which being ultimately set free from
the sporocysts and snail in a way not clearly traced, might then be
found as freely-moving Cercarice in the water, ready to start on the
same round again, thus forming a complete illustration of alternation
of generations. This life history, with modifications, was supposed to
apply to B. Haimeanus, the ramified tubular structure in which it
was found being considered a sporocyst. After comparing his own
observations with those of M. Lacaze-Duthiers, showing that the facts
observed were much the same, although the interpretation he had
been led to put on them was different, he pointed out that the
branched character and apparent connection with egg-sacs observed in
this structure might be accounted for, supposing it an anomalous form
of sporocyst, by such sporocyst being contained in the genital ducts.
The presence of blind extremities, and an appearance of budding, he
had thought indicated the points where egg-sacs had emptied their
contents into the tubular structure. If it were a sporocyst, the blind
extremities were doubtless the ends which M. Duthiers had found it
almost impossible to examine. Other appearances described by M.
Duthiers he briefly alluded to, the interpretation he had put upon
them being influenced by his different experience. He had never
found B. Haimeanus in oysters, but only in cockles containing fully
formed eggs, although he had examined large numbers procured from
Hayling, where from their juxtaposition it would appear probable
that this organism might be found in both if parasitic. He thought

44

PROCEEDINGS OF SOCIETIES.

M. Duthiers’ figure was drawn from, a somewhat immature specimen,
and mentioned that a difference in structure visible at the lamellar
extremity under polarized light, both in B. Haimeanus and the other
allied organism, had induced him to think that here might he the
beginning of rudimentary shells. If the structure containing B.
Haimeanus could be found in oysters, it would disprove his conjecture
as to the nature of these organisms. He briefly alluded to the
recorded encystment of B. Haimeanus, which, if confirmed, would
introduce us to a life history of remarkable character and great
interest. How the ova of the supposed sexual fluke entered the
cocldes so abundantly on our coasts had not as yet been indicated;
and if the structure in which B. Haimeanus was found ivas a sporocyst,
it was an anomalous one, and furnished a subject for good work in
tracing its parentage and development.

Mr. W. Fell Woods read a paper “ On the relation of Bucephalus
to the Cockle.” Having stated that his investigations began as far
back as June, 1872, he traced, as the result, verified by his notes up
to May, 1873, the growth of his impression that Bucephalus, instead
of being parasitic, was the larval form of the cockle. Having detailed
the reasons, he pointed to the independent examinations of Dr. Moore,
commenced in May, 1873, as issuing in the like conclusion. These
facts were his warrant for still advancing the theory at the meeting
of the Royal Microscopical Society on the 4th of November last. He
then adduced more recent observations, furnishing new confirmatory
facts, -which he considered of great interest ; and after indicating some
points of difference between Dr. Moore and himself, and referring to
the memoir by M. Lacaze-Duthiers on Bucephalus Haimeanus — to
whose description of the earliest stage he took exception, he pointed
to his own discovery of the same eggs contemporarily in the ovisacs
of the cockle and in the supposed sporocysts ; and whilst admitting
the parasitic character of Bucephalus, if its observation in the oyster
were reliable ("liis own large experience had never afforded an instance),
he argued that either, 1st, Bucephalus is the larva of the cockle (and
if not, it remains an interesting question for solution, what is?), or,
2nd, Bucephalus is a parasite, but if so it does not render the cockle
sterile, as asserted by M. Lacaze-Duthiers ; and, 3rd, the connection
of the tube with the ovisacs, as established by the presence of the eggs
in both, proves it is not an independent sporocyst, as asserted, but an
organ of the cockle ; whilst, 4th, if this connection be denied, though
the case quoted seemed to render it certain, Bucephalus must still be
developed from eggs seen in the tube, in contradiction of a third
statement of M. Lacaze-Duthiers.

Some illustrative drawings were exhibited.

THE

MONTHLY MICROSCOPICAL JOURNAL.

AUGUST 1, 1875.

I. — Number of Striae on the Diatoms on Mollers Probe-Platte.

By F. Kitton, Norwich.

{Taken as read before the Royal Microscopical Society.)

In the table of measurements of the striae of the various diatoms
on Moller’s Probe-Platte appended to Mr. J. E. Smith’s paper
published in the last number of this Journal, Nitzschia curvula is
stated to have 84 '1 in '001''. As I am well acquainted with this
form, not only from specimens of Professor Smith’s own gathering,
but also from many other sources, I felt certain that some error
had been made. I have therefore examined one of Moller’s prepara-
tions of the form he calls by this name, and, as I suspected, it is not
Nitzschia curvula Sm. but his Nitzschia sigma.* The figure in the
Synopsis is very characteristic so far as the outline of the valve is
concerned, but the striation (very imperfectly shown) represents the
striae far too distant. The Synopsis states the striae to be 56 in -001".
I have never seen any British specimen of this species with striae
so close as this, and in a gathering from Felixstow they are about
as easily resolved as those on Pleurosigma quadratum : about
40 in ’001" I consider to be a nearer approach to accuracy. The
species sold by Moller certainly has them very fine, and not easily
resolved with 4th objective and B ocular, but in no respect is there
any difference of specific value to distinguish it from the British
form.

N. curvula of Smith ( = N. sigmatella Gregory, ‘ Quar. Jour,
of Mic. Sci.,’ vol. iii.). The specific characters in the Synopsis are
not only obscure but misleading. The description is as follows :

“ F. Y. linear, tapering towards the truncated extremities.
Y. linear acute, striae obscure. Almost identical with N. sigma , but
distinguished from that species by its more delicate striae and fresh-
water habitat.” It will be seen from the above description that no
definite idea of this species is obtainable ; no allusion is made to
the sigmoid form of the valve nor to the pseudo-punctate appearance
of the margins of the valves ; the remark that it is almost identical
with N. sigma is also misleading, it really bears no resemblance to
that form, and the striae are at least as distinct, and perhaps more

* I have forwarded specimens of both forms, which can be seen at the
Society’s rooms.

VOL. XIV.

E

46

Transactions of the Royal Microscopical Society.

so. It is only from the examination of authentic specimens that it
is possible to ascertain the form to which Smith gave the specific
name of curvula. Gregory gives a good figure, but no description.

“ Dr. Lewis, U.S.A., in his paper on ‘ Some new and singular
intermediate forms of Diatomaceae,’ has properly removed this form
from the genus Nitzschia and placed it with the Surirellae. He
gives the following specific characters :

“ Surirella intermedia, n. sp. Frustules free. Yalve linear,
strongly sigmoid, with attenuated rounded apices. F. Y. straight
or slightly sigmoid, expanding at the sub-truncate extremities.
Alas usually distinct, twisted near the ends of the valves, giving rise
to a spathulate appearance. Canaliculi numerous, inconspicuous,
reaching the narrow central blank line. Striae distinct, variable as
to number and fineness.”

The value of the distance of the striae on the Diatomaceae either
as a test for the resolving powers of objectives or as specific distinc-
tions is but little ; in the latter they may he said to be valueless, and
in the former case they are only of value when the actual distance
of the striae is known. Moller’s slide of N. curvula (= N. sigma)
is mounted from a brackish water gathering from Schleswig and con-
tains the same forms as my own Felixstow gathering, viz. N. sigma
very plentiful, Pleurosigma fasciola common, P. angulatum,
N. minutula, &c. ; hut in my gathering, the striae on the two first-
named forms are resolvable with a £th objective of 75° angular
aperture made twenty-two years ago by A. Eoss. On P. fasciola I
can resolve both sets of striae, and with Beneche’s No. 7 and

0 ocular I can see both sets at once (that is to say, the dots are
shown in squares). The striae on the same forms on Moller’s slide

1 can only resolve with my |th, N. sigma with difficulty, and only
one set of striae at a time on P. fasciola.

In Moller’s beautiful preparation of P. angulatum the striae on
that form are easily resolved with my Eoss Jth, whilst those from
many British localities are quite invisible under the same conditions.
Nitzschia sigmoidea (type) is not an easy test for a good |th, hut
its var. A is easily resolved by a good 4 inch.

This variation in the distance of the striae on the same species of
diatom probably arises from a more vigorous growth in the frustule,
and it will be generally found that the more robust the frustule is, the
more distinct are the striae. An unscrupulous dealer in objectives
has only to take advantage of this fact, and he can palm off inferior
objectives by guaranteeing their being able to resolve certain so-
called tests ; for example, a very inferior £th would show the striae
on N. sigmoidea /3, or an |th of moderate quality would probably
show the markings on the coarsely striated P. fasciola, which would
be perfectly incapable of resolving those on Moller’s slide.

v T\1 TU
<• Vi tv ii

IV.We^t Sc- Co .

Spli . P ortoric ense .

( 47 )

II. — On Bog Mosses. By R. Bratthwaite, M.D., F.L.S.

Plates CX. and CXI.

21. Sphagnum Portoricense Hampe.

Linnoea 1852, p. 359.

Plate CX.

Syn. — Sullivant Icon. Muse. p. 3, Tab. 2 (1864). — Austin Muse. Appalach.
No. 1 (1870).

Sph. Sullivantianum Austin iu Amer. Journ. Sci. 1863, p. 252.

Dioicous ? in large soft tufts, pale fuscous below, pale glaucous
green above. Stems 8—14 in. high, stout, simple or bipartite,
firm, pale brown ; cortical cells in 2-3 layers, containing spiral
fibres but few pores. Stem leaves auricled, erect or deflexed,
subquadrate-ovate, fringed round the entire margin, upper cells
rhomboidal, lower elongated, all without fibres or pores.

Bamuli 4-5 in a fascicle, 2—3 divergent, arcuate-patent,
subclavate- fusiform, attenuated at base, the leaves julaceously
imbricated ; pendent branches more slender, lax. Cuticular cells
spirally fibrillose with few pores, the transverse walls geniculate
downward into the adjacent cell, usually having a pore at the apex
of the bend.

Leaves of the divergent branches small below and widely
cordate or semicircular, becoming larger above, narrowed at base,
the median orbiculate-ovate, squamoso-scabrous at bach of the
strongly cucullate apex, very narrowly margined, all minutely
fimbriate throughout, the fibrils of the fringe formed of the
commissural walls of destroyed hyaline cells ; lower hyaline cells
elongato-rhomboidal, upper rhombic, with numerous strong papillae
internally on the wall combined with the chlorophyll cells, all
fibrillose, with several large pores at the margin ; chlorophyll cells
triangular in section, interposed between the hyaline on the concave
surface of leaf. Fruit unknown.

Hab. — Swamps in mountain districts. First found in Porto
Rico by Schwanecke. Manchester ponds, Ocean County, New
Jersey (Austin).

[ EXPLANATION OF PLATE CX.

Sphagnum Portoricense.

a. — Plant from Austin’s collection.

1. — Part of stem and branch-fascicle.

5. — Stem leaves. 5 a a. — Areolation of apex of same.

> 6. — Leaf from middle of a divergent branch. 6 x. — Section of same. 6 c. — Cell
from middle x 200. 6 b. — Leaves from base of the same branch. 8. — Leaf

from a pendent branch.

9 x. — Part of section of stem.

10. — Part of a branch denuded of leaves. 10 a. — Cuticular cells of same.
10 b. — The same seen laterally. 10 x. — Transverse section of a branch.

E 2

48

On Bog Mosses. By R. Braithwaite.

This fine and rare species stands at the head of the Cymbifolia
group, and naturally arranges itself with Sph. Austini and papil-
losum. It may at once be distinguished by the beautifully fringed
margin of the branch leaves, and by the curious downward pro-
longation of the transverse wall of the cortical cells of the branches,
which may he readily observed in the series of cells at each lateral
margin.

Subgenus Isocladus. Lindb.

Plants lurid-whitish-green, glossy. Ptamuli 2—4 in a fascicle,
all uniform and divergent, with very large, narrow, loosely spreading
leaves, their cells very narrow, without fibres and with a central
longitudinal row of pores

22. Sphagnum macrophyllum Bernhardi.

Bridel, Bryol. Univ. I. p. 10 (1826).

Plate CXI.

Syn. — Drummond Muse. Amer. Coll. 2, No. 18 (1841). Sulliv. Muse. Alleghan.
No. 207 (1845). Mosses of Un. St. p. 12 (185G). Ic. Muse. p. 1 t. 1 (1864).
C. Mull. Synops. I. p. 91 (1S49). Sull. Lesq. Muse. bor. Amer. No. 1 (1856).
Austin Muse. Appal. No. 41 (1870). Isocladus macrophyllus Lindb. Ofv. af K.
Vet. Ak. Forh. XIX, p. 183 (1862).

Dioicous, pale olive-green, fuscescent below, when clry glossy
and shining. Steins 6—10 in. high, rather rigid, very fragile,
fuscous, simple or dichotomous by innovation, with 2—3 layers of
cortical cells.

Branches crowded in a spinose capitulum 3—4 in a fascicle ,
uniform and similar, divergent, dependent, straight, subflabellate,
lax-leaved, the cortical cells short, uniform, with few pores. Stem
leaves minute, very broad at base, ovate-oblong, obtuse, entire, the
hyaline cells rhomboid, without fibres, but with 1—3 central pores.

Branch leaves rather rigid, subdistichous, small at base of
branch, soon becoming elongated, narrowly lanceolate, and lanceo-
late-subulate, involute-concave, bordered by 1—2 rows of extremely
narrow cells, apex somewhat truncate with 7—8 teeth. Hyaline
celts elongate fexixoso- fusiform, with 6—10 pores in a longitudinal
median line ; free from fibres. Chlorophyll cells circular in section,
separating the hyaline both in front and back.

Fruit in the upper fascicles or in the coma, divergent ; peri-
clivetial bracts 6—9, lax, oblong-ovate, uppermost convolute, truncate,
and toothed at apex, the areolation resembling that of the branch
leaves. Capsule small on a shortish slender peduncle ; spores
sulphur coloured.

Male plant and prothallium unknown.

Hab. — North America. Near Philadelphia (Bernhardi).
Swamps in Louisiana (Drummond). Raccoon Mountains, Alabama

jR, _£} rcU&JWoiAj& d&L. ocds run^ .

H' Vn'ist-ScCc.-'jvf)

Sp ii . m a,c v o p hyll um .

On the Unit of Linear Measurement. By Rev. D. Edwardes. 49

(Lesquereux). Green County, Mississippi (Tice). New Jersey
(Austin).

Quite peculiar among the Sphagna, by the uniform branches in
the fascicles, the slender pendent branches found in most of the
species being wanting, and also by the central position of the pores
and total absence of fibrils. The convolute leaves and pointed
branches give it somewhat the aspect of Hypnum cuspidatum,
while if we overlook the pores, the areolation is not unlike that of
II. riparium or fluitans, and with this approximation to the true
mosses we conclude our series of Sphagna.

EXPLANATION OF PLATE CXI.

Sphagnum macrophyllum.

а. — Fertile plant from Drummond’s collection.

4. — Perichcetial bract. 4 p. — Point of same.

/>. — Stem leaves. 5 a a. — Areolation of same.

б. — Leaves from middle of a branch. 6 p. — Point of same. 6 x. — Section.

G c. — Cell from middle x 200. 6 b. — Leaves from base of the same

branch.

9 x. — Part of section of stem.

10. — Part of a branch denuded of leaves.

III. — On the Unit of Linear Measurement.

By Bev. D. Edwardes, M.A., St. Chad’s College, Denstone.

Beading Schumann’s ‘ Diatomeen der Hohen Tatra ’ a short time
ago, I came across the following passage : “ Auch die Englander
werden auf dem Felde der Diatomeen den englischen Zoll, wenn-
gleich er durch die experimentalen Arbeiten Newton’s eine beson-
dere W eihe erhalten hat, aufgeben und mit dem Maase Ehrenberg’s
messen.” This was written in 1867. I immediately set to examine
a few of the last volumes of the Microscopical Journal, as being
the best test I could think of as to what extent the event of things
has proved Schumann’s prophecy true. I founJ, as I expected,
scarcely an instance of an English microscopist making use of the
Paris line, which was Ehrenberg’s standard unit.

Although English microscopists are thus still sturdy English-
men, yet there is a large number of English men of science who
seem to think that wisdom is found only on the other side of the
Channel, and are endeavouring to further in this country the
arbitrary introduction of the French system of measurement.

I have no wish to predict what will be the system of measure-
ment fifty years hence, but it does seem to me that both parties —
the English and the French — are content to put up with a more im-

50 On the Unit of Linear Measurement. By Rev. D. Edwardes.

perfect and unsatisfactory state of things in this respect than the
occasion requires. I am probably right in conjecturing that there
are not many thinking men who are absolutely satisfied with our
own system, in spite of its many excellent points. Those who have
to measure minute quantities find the factors of 12 to be of very
little use, and almost all scientific men are obliged to adopt a
decimal system between certain limits. It is also difficult to under-
stand how scientific refinement, if I may be allowed the expression,
is content to put up with a system of measurement whose unit is
the length of a “ barleycorn from the middle of the ear.” This is
theoretically still the case, although in practice a rod equal in length
to 108 of these primitive barleycorns placed in juxtaposition, has
been substituted and put by in the Exchequer Chamber for refer-
ence in case some of Her Majesty’s subjects should find all their
mid-ear barleycorns not precisely the same length.

On the other hand, it requires an excess of Fran comania to
adopt the French metre for our unit. It is true it originated
with scientific men and not with the agriculturist, but it might
indeed be contended that the English unit is the more philo-
sophical of the two. Doubtless there was once upon a time such a
barleycorn three lengths of which went to make up exactly an inch,
the thirty-sixth part of the standard yard. But there never was
and never will be, subject to the present laws of nature, such
a quadrant of meridian that can be subdivided into 10,000,000
French metres. The metre again, should it be readjusted, is only in
a degree better than the barleycorn. For it must vary as the place
of measurement. The equator is slightly elliptical, and conse-
quently there can be at most in the same hemisphere but four
quadrants of meridian which are exactly the same length. Do
what we may, the metre will only be a local and consequently a
national unit. It stands to reason that the metre as well as the
yard must go if we are to have a universal unit.

The length of a pendulum vibrating seconds is liable to the
same objection. The experiment must be made at some particular
spot, and will hold good for that spot alone. Should anything
occur which would make that spot discoverable only by its longi-
tude and latitude, complicated elements would have to be introduced
into the calculations.

Sir J. Herschel suggested that the diameter of a sphere of the
same volume as the earth should be taken as unit. The mean dis-
tance of the earth from the sun might also be suggested for a
terrestrial as well as a celestial unit ; but the infinite subdivisions
of these enormously large units would appear at first sight, saying
the least, somewhat clumsy. Should scientific men meet to discuss
the matter, there is probably no doubt as to the unit they would
adopt, namely, the wave-length in vacuum of a particular kind of

On the Unit of Linear Measuremen t. By Rev. D. Eclwarcles. 51

light emitted by some widely diffused substance, such as sodium,
which has well-defined lines in its spectrum.

Assuming the wave-length as unit, there would scarcely be a
doubt as to the adoption of the decimal system in proceeding with
its multiples. The best unit for common use would be a matter for
deliberation, and would take years to be adopted anything like
universally.

If instead of taking the wave-length of yellow light, as has been
suggested, we take that of the orange, which is slightly longer, our
present measurements could be converted with peculiar facility.
A million wave-lengths are equal to the mechanic’s two-feet rule.
The convenience of adopting this instead of the yard for a common
unit would more than compensate for the ease with which the latter
is extemporized by the matron’s arm or the ploughman’s pace.
This rule, as it is generally folded up into two, can be carried about,
without any inconvenience, by anybody to whom it ever becomes a
matter of any importance to satisfy himself or others as to the
dimensions of surrounding objects.

With the wave-length of orange light we should have

Wave-lengths. Inches. Feet. Yard.

1,500,000 = 36 = 3 = 1

1,000,000 = 24 = 2

500,000 = 12 = 1

41,666! = 1

In round numbers 1,000 = ^

or 1 = toioo

I confess my object is more to beat about the bush, to use
a familiar expression, than to propose a modulus or to cut out
a perfect system of measurement. This must be done by repre-
sentatives of the different scientific societies meeting to discuss the
matter. When they meet and deliberate upon the subject we shall,
undoubtedly, have the best system of measurement possible. But
then a sufficient number of them must meet, so that English spirit
may have as much fair play in their deliberation as it has in that
♦of the House of Commons. The Committee of the British Associa-
tion have signally failed in this respect. From time to time they
have recommended the French metre for our unit; but Englishmen
will not become Frenchmen, much as they love their neighbours.
They will not adopt a unit of measurement which practically is
the exclusive property of the French nation, and theoretically holds
good only when it is measured across the territory of the French
liepublic.

( 52 )

IY. — The Microscope and its Misinterpretations.

By John Michels.

The old adage that “ seeing is believing ” has long been exploded,
and folks nowadays receive with caution the impressions conveyed
by their eyesight.

There is still, however, a fixed idea with many people that, when
the human sight is aided by powerful and correctly-constructed
optical instruments, full reliance can be placed upon such united
powers, and that the investigator may record that which he believes
he sees as veritable and established facts.

In contradiction of such belief I shall place before the reader
some curious results, which will show that the utmost caution is
required by those using optical instruments for the elucidation of
scientific problems or ordinary research.

Quite an interesting paper could be written upon the optical
delusions with which astronomers have to contend in the use of the
telescope, hut I propose to confine my remarks to the difficulties
which beset the path of the microscopist, in obtaining truthful and
accurate results, while using the microscope, leading to the most
contradictory statements from men wdiose powers of observation
and skill in the use of the instrument are admitted.

Those who make use of a microscope for the first time are
usually fascinated by the wonderful and beautiful appearances pre-
sented, and, having illuminated the object under examination with
a flood of light, and focussed it to their satisfaction, congratulate
themselves upon the ease with which they have handled the instru-
ment, and fondly believe they have attained to a knowledge of its
use. More extended study, however, and the use of high powers
with the more complicated pieces of apparatus, soon convince the
student that the instrument requires the most delicate manipulation,
and that much practice is necessary before its true powers are
developed.

Until full command over a microscope has been acquired, thq
most contradictory and perplexing results are obtained by those who
use high powers in the examination of difficult objects, especially if
the subject is very transparent. Things examined yesterday appear
quite different to-day, both in form and colour ; and even while the
eye is still fixed upon the object, a slight change in the position
of the mirror will alter its appearance, or present entirely new
features.

Again, an object mounted in different mediums, or without any,
will present the most varied appearances, and the honest investigator
is thus embarrassed to decide which is the true form.

These complications follow the use of the instrument through

The Microscope and its Misinterpretations. By J. Michels. 53

all its stages ; but when the causes are well understood, the diffi-
culties are reduced to a minimum, and even turned to account in
the examination of difficult objects.

Great success in the use of the microscope can only be obtained
by the skilful manipulation of the light, and he that is not ac-
quainted with the numerous schemes, devices, and contrivances in
its management, might as well be in the dark ; no directions here
avail, and nothing but diligent and constant practice will render the
student efficient in this respect.

I once stood an hour watching a leading London optician
struggling to show me the true markings of a diatom with a new
object-glass he had recently constructed, with which he had had no
previous difficulty. He at last gave up the attempt in despair. Of
course an objective that has once performed a specific test will do so
again. In this case the only thing in fault was the management of
the light. This had disgraced the object-glass, and enraged its
maker.

In contrast with the above case I may mention the real pleasure
I experienced in witnessing the skill of a professional microscopist
of this country. In his hands all difficulties appeared to vanish,
and he showed me one of the most difficult objects known, with
marvellous promptitude.

But to return to my subject. To enable the student to familiarize
himself with the true power of the microscope, and to train his eyes
to detect errors of vision, certain well-known test-objects are in
general use, which are also convenient to test the quality and
power of objectives. A favourite object of this class is the scale of
the Podura, a minute insect, which dwells in remote nooks of dark
and damp cellars, and similar localities.

This scale is usually mounted dry, and when viewed under the
compound microscope with suitable objectives, presents a surface
studded with marks similar to the well-known note of excla-
mation (!).

This test-object has been for years the delight of microscopists
possessing high powers, and a sharp definition of its peculiar
markings, as above mentioned, was accepted as its true appearance
and form.

For twenty-five years this scale was under constant examination
by every grade of microscopists, from the grandees of the Boyal
Microscopical Society to the humble tyro, without any new or
special feature being noticed, when on November 10, 1809, Dr.
G. W. Royston-Pigott, F.R.M.S., read a paper “ On High-Power
Definition,” before the Boyal Microscopical Society, and surprised
the members by stating that all these years they had been gazing
at the Podura scale, but had never yet seen its true markings.
Dr. Pigott’s paper described very fully what he had discovered as

54 The Microscope and its Misinterpretations. By J. Michels.

the true markings, and illustrated it with drawings which repre-
sented them to be distinctly of a beaded character ; in fact, as
dissimilar from the old accepted idea of their form as contrast could
depict them.

Every microscopist was now hunting Podurae, and cellars damp
and dismal were ransacked for the little scale-bearers, doubtless to
the astonishment of numerous colonies of spiders, who must have
been much provoked by this invasion, and thus commenced a con-
troversy which is not yet concluded. Men equally eminent have
taken opposite sides, and expressed the most contrary opinions ; and
I now propose to give a brief resume of what has been said and
done in regard to this subject, because the matter is full of instruc-
tion to those interested in microscopical research. Not that the
markings of the Podura are of the slightest importance, or have any
scientific significance, hut the gravity of the conclusions which are
sought hinges upon the fact that, if the views of Dr. Pigott are
correct, our most eminent microscopists have been promulgating
false and erroneous statements respecting the form of a well-known
and common object ; and in whatever light the controversy is
viewed, the humiliating confession must be made that they are still
unable to determine the correct focus or the proper method of illu-
minating it.

Dr. Pigott commences by calling resolving the Podura scale
“ a difficult enterprise,” and then describes the beaded appearance
in the following manner : “ Under a low power, as 80 or 100, the
Podura scale is remarkable for its wavy markings, compared to
watered silk ; raising the power to 200 or 250, and using a side
light, the waviness disappears, and in its place longitudinal ribbing
appears ; with 1200 they divide themselves into a string of longi-
tudinal beads ; but with 2300 they appear to lie in the same plane
and terminate abruptly on the basic membrane ; in focussing for the
beads attached to the lower side, the headings appear in the inter-
costal spaces.”

Piespecting the old received views of the Podura scale, Dr. Pigott
says : “ With 300 to 500, the celebrated 1 spines ’ appear, according
to the size of the scale, as very dark tapering marks (like ‘ notes of
admiration ’ without the dots 1 ' >). To see these clearly with 2500
has been considered the ne plus ultra of microscopical triumphs,
and it is consequently with no small diffidence that the writer
ventures to traverse the belief of twenty-five years.”

Dr. Pigott further states that he reckons these beads to be
'5‘tro'ir o'fh to TsoWoth of an inch in diameter, and that the “ spines,”
which he calls spurious, really embrace in general three or four
beads, while the intervening space abounds with beads seen through
the basic membrane, and very difficult of observation without special
management ; and concludes with the remark that he expects in a

The Microscope and its Misinterpretations. Bxj J. Michels. 55

few months the Podura headings, such as he described them, will be
fully established.

Thus was the gauntlet thrown down, and the challenge was at
once accepted by various members of the Society, who, on the con-
clusion of the reading of the paper, at once disputed the doctrine.
Mr. J. Beck was the first to express an opinion, and rather increased
the confusion of the subject by stating that both the spines and the
beads were illusory, and that the true structure of the Podura scale
was a series of corrugations on one side, and that the reverse side
was slightly undulating or nearly smooth, and that the notes of
exclamation were due to refraction of light.

Mr. Hogg, the Hon. Secretary of the Society, thought Dr.
Pigott in error ; he had never seen such appearances as beads ;
thought probably Dr. Pigott had seen them by using too deep an
eye-piece, bad illumination, and drawing out the tube of the micro-
scope to too great an extent ; or, perhaps, to a disturbed vision
caused by advanced age and presbyopia.

The President, the Rev. J. B. Reade, followed by stating that he
agreed with the observations made by Mr. Hogg ; and such was his
faith in the skill of the opticians of the day, that he could not but
feel that what he saw with their instruments really existed.

On the same date and occasion on which Dr. Pigott expounded
his views, Mr. S. J. Mclntire, a member of the same Society, read a
paper “ On the Scales of Certain Insects of the Order Thysanura.”
Now, Mr. Mclntire, although a recent member, and young in mi-
croscopical research, is always listened to on this subject with
respect by the Society, having devoted his attention specially to
these insects, and shown a patient and intelligent power of observ-
ing not only their structure but their habits ; he, in his commu-
nication, opposed Dr. Pigott’s views, and calls the beads “ optical
illusions,” and concurred with Mr. Beck’s statement that the surface
of the scale is corrugated, but flatly contradicts him by stating that
both sides are alike.

December 8, 1869. — The President, the Rev. J. B. Reade, stated
that he, with Dr. Miller and others, had interviewed Dr. Pigott,
and was bound to say he had seen the beaded appearances, and it
was clear to liini now that in the best object-glasses small residuary
aberration existed.

This slur upon the best object-glasses brought out Mr. Wen bam
with a paper in the Microscopical Journal of June, 1870, in which
he repudiated such error, and described the beaded appearance as
an illusion, obtained by a trick of illumination, and by examining
the scale with the microscope out of focus.

At the June meeting of the Royal Microscopical Society a
letter was read from Colonel Woodward, of Washington, enclosing-
photographs of the Podura scale, showing what he considered to be

56 The Microscope and its Misinterpretations. By J. Michels.

the true appearance. These photographs showed the spines.
Colonel Woodward, however, reserved his opinion, and asked for a
specimen of the true test-Podura scale.

Dr. Maddox, in August, exhibited various photographs of
Podura scales, which Mr. Wenham commented on in a paper to the
Microscopical Journal of September following, which merely reite-
rated his views that the “ spines ” were the true appearance of
Podura scales.

The Rev. J. B. Reade, in the £ Popular Science Review,’ of April,
1870, appears to accept Dr. Pigott’s views entirely, and writes : “ I
can now see with my own powers what has been before invisible,
viz. the beautiful headed structure of the whole test-scale, as
discovered by Dr. Pigott.”

It would he tedious to continue the subject and give even an
outline of the papers and discussions that have been provoked by
this knotty question ; I shall therefore conclude by stating that
Colonel Woodward has since produced two photographs, showing
the two aspects of the question; they are made from authentic
scales, and are pronounced very perfect.

In further illustration of the difficulty of obtaining a true and
reliable image of an object when viewed under the microscope with
high powers, I offer drawings which have been made by Mr. Ralph
H. Westropp, B.A., T.C.D., of Allyflin Park, England. These
figures all represent the same object, a scale of Podura viewed under
different phases of oblique light ; they are interesting as showing
the effect produced by the play of light upon a refractive object.

The fact that the most skilful microscopists of the age all differ
upon the true appearances of a common and not very minute object,
and the microscope itself presenting to the vision the most opposite
appearances of one and the same object, should act as a caution to
those who accept too readily theories based upon microscopical
research ; and suggests that, in the cause of justice, when life is at
stake, single-handed evidence relating to the microscopical examina-
tion of apparent blood-stains should be verified at least by a second
person before being accepted.

Thus we see that the so-called revelations of the microscope are
but hieroglyphics, needing the interpretation of a mind of the
highest culture, and that while the microscope is a good servant it
is a bad master — mighty in the hands of a Huxley, but as useless
to a man without the powers of discrimination as the chisel of
Michael Angelo would be in the hands of a Modoc. — The American
Popular Science Monthly, June, 1875.

( 57 )

V. — Doable Staining of Wood and other Vegetable Sections.

By George D. Beatty, M.D., of Baltimore.

In my paper on vegetable staining in the April number of this
Journal,* I said the only aniline colour I had used with success for
staining leaves was the blue. The statement was based on the fact
that this colour did not come out when the leaves were put into
absolute alcohol, or into oil of cloves, provided certain brands of
these chemicals were used.

I have lately discovered that benzole fixes the anilines when
they are used in staining vegetable and animal tissues. It not only
instantly fixes any aniline colour in vegetable tissues, but also
renders them as transparent as oil of cloves.

Finding that benzole possessed this property, led me to try
double staining upon sections of leaves and sections of wood. The
results have proved highly satisfactory. I have found the follow-
ing processes successful : A section, say of wood, being prepared for
dyeing, is put for five or ten minutes in an alcoholic solution of
“ roseine pure ” (magenta), one-eighth or one-quarter of a grain to
the ounce. From this it is removed to a solution of “ Nicholson’s
Soluble Blue Pure,” one half-grain to the ounce of alcohol, acidu-
lated with one drop of nitric acid. In this it should be kept for
thirty or ninety seconds, rarely longer. It should be frequently
removed with forceps during this period, and held to the light for
examination, so that the moment for final removal and putting into
benzole be not missed. After a little practice the eye will accurately
determine the time for removal.

Before placing the object in benzole it is well to hold it in the
forceps for a few seconds, letting the end touch some clean surface,
that the dye may drip off, and the object may become partially dry.
By doing this, fewer particles of insoluble dye rise to the surface of
the benzole, in which the brushing is done to remove foreign matter.
The object should then be put into clean benzole. In this it may
be examined under the glass. If it is found that it has been kept
in the blue too short a time, it should be thoroughly dried, and,
after dipping in alcohol, be returned to that dye. If a section of
leaf or other soft tissue be under treatment, it should be put in
turpentine or oil of juniper, as they do not contract so much as
benzole.

When hsematoxylon is used instead of magenta, it is followed by
the blue as just described. As neither of these dyes comes out in
alcohol or in oil of cloves, the section may be kept in the former for
a short time before placing in the latter.

The hoematoxylon dye I prefer is prepared by triturating in a

* * Cincinnati Medical News,’ June, 1875.

58 Double Staining of Wood, etc. By G. D. Beatty.

mortar for about ten minutes two drachms of ground campeachy
wood with one ounce of absolute alcohol, setting it aside for twelve
hours, well covered, triturating again and filtering. Ten drops of
this are added to forty drops of' a solution of alum ; twenty grains
to the ounce of water. After one hour the mixture is filtered.

Into this the section, previously soaked in alum-water, is placed
for two or three hours, or until dyed of a moderately dark shade.
When dyed of the depth of shade desired, which is determined by
dipping it in alum-water, the section is successively washed for a
few minutes each, in alum- water, pure water, and 50 per cent,
alcohol. Finally it is put in absolute alcohol until transferred to
the blue.

Carmine and aniline blue produce marked stainings, but they
are rather glaring to the eye under the glass. I use an ammoniacal
solution of the former, double the strength of Beale’s, substituting
water for glycerine. In this a section is kept for several hours.
On removal it should be dipped in water, and then put for a few
minutes in alcohol acidulated with 2 per cent, of nitric acid ; then
in pure alcohol ; then in the half-grain blue solution before spoken
of, from which it should be removed to alcohol; then to oil of
cloves. Much colour will be lost in the acid alcohol. The acid
is to neutralize the ammonia, which is inimical to aniline blue.
Magenta aniline or haematoxylon may be used with green instead
of blue aniline. The brand of green I prefer is the iodine brand,
one grain to the ounce of alcohol.

Double stainings of sections of leaves in which red is first used
have the spiral vessels stained this colour, other parts being purple
or blue. Kadial and tangential sections of wood have the longitu-
dinal woody fibres red, and other parts purple or blue.

This selection of colour is, I think, due to the fact that spiral
vessels and woody fibres take up more red than other parts, and are
slower in parting with it. The blue, therefore, seems first to over-
come the red in parts where there is less of it. It will entirely
overcome the red if sufficient time be given.

If the blue be used before the magenta aniline, the selection of
colour is reversed.

I would here call special attention to the importance of examin-
ing these stainings at night, as the red in them has a trace of blue in it
which does not show at that time, but comes out so decidedly by day-
light, as to change, even spoil, the appearance of the specimen.

I think they should be mounted in Canada balsam, softened
with benzole, as the presence of the latter may be beneficial in pre-
serving its magenta.

I would offer a few words upon section-cutting, and upon pre-
paring sections for dyeing.

To cut a thick leaf, place a bit of it between two pieces of potato

59

On Conjoined Epithelium. By S. Martyn.

or turnip, and tie with a string. Cuts may be made along the mid-
rib, or across it, including a portion of leaf on either side, or through
several veins. Fine shavings of wood may be used, or pieces rubbed
down on hones.

Sections of leaves may be decoloured for staining by placing for
some time in alcohol ; but I would recommend the use of Labar-
raque’s solution of chlorinated soda, for twelve or twenty hours after
the alcohol. Especially do I recommend the Labarraque for all
kinds of wood. In twelve hours wood is generally bleached ; too
long a residence in it will, however, often cause it to fall in pieces.

After removing from the soda, wash through a period of twelve
or eighteen hours in half-a-dozen waters, the third of which may
be acidulated with about ten drops of nitric acid to the ounce, which
acid must be washed out. Next put in alcohol, in which sections
and also leaves may be kept indefinitely, ready for dyeing.

Before closing this I would add a few suggestions concerning
leaves not contained in my January article.

Magenta, when used for them, should be of the strength of one-
eighth or one-quarter of a grain to the ounce of alcohol, and purples
and iodine-green two or three times as strong. These anilines are
inferior to the blue in bringing out all the anatomical parts of a
leaf, including the beautiful crystals so often met with. On re-
moval from the dye, leaves should be thoroughly brushed with
camel-hair pencils.

One week, instead of forty-eight hours, is frequently required to
effect the decolouration of large leaves in chlorinated' soda, even
when they are cut into several pieces, which is advisable.

Mr. L. R. Peet, of Baltimore, whose stainings in aniline are
unsurpassed for beauty, thinks better results are attained by com-
mencing with a weak dye, say from one-twentieth to one-twelfth of
a grain, and slowly increasing the strength of the dye, at intervals
of from one to three hours, until the required hue is obtained.
This process certainly guards against too deep staining, and may
give a finer tone to leaves under the glass.

VI. — On Conjoined Epithelium. By S. Martyn, M.D., F.R.C.P.,
Lecturer on Medicine and Pathological Anatomy, Bristol
Medical School.

Plate CXII.

It does not appear that much attention has been given by English
observers to the so-called “ prickle and ridge ” cells ( Stachel - und
Rijf-zellen). At all events, they have scarcely found their way into
our most recent books on pathology; while the drawing in our
VOL. XIV. f

60 On Conjoined Epithelium. By S. Martyn.

newest text-book on minute anatomy is almost, if not quite,
identical with the earliest sketch in Virchow’s £ Arcliiv.’

It is, nevertheless, twelve years since these cells were first dis-
covered and named by Professor Max Schultze ; and their distribu-
tion in fishes and amphibia has been fully described (1867) by his
brother, Professor Franz Schultze. They have been subsequently
noticed by Kolliker, Frey, Kindfieisch, Strieker, Cornil and lianvier,
Eollett, and others. They have been called “spinous cells/’
“echinate cells,” “cellules dentelees,” “ribbed” and “spiny and
furrowed ” cells ; but no observer seems to have added any careful
researches to the original description of Max Schultze, by whom
the name was given to them of “ prickle and ridge ” cells. And
yet there is a certain beauty and interest attaching to these
structures which seem to entitle them to more detailed notice ;
and while they offer problems in histogenesis of great interest to
the anatomist and physiologist, they cannot but do so also in some
degree to the pathologist. It is a good illustration of the old story
of “ eyes and no eyes,” that a very remarkable structure, and not a
difficult one either, in so thoroughly common a place as the borders
of an epithelial cell, should have been persistently overlooked for
many years, and long after high microscopic object-glasses had been
brought to great perfection. No one need despair of seeing some-
thing new and important by looking with extra carefulness at what
is, so to speak, straight before his face, after this fact, that the mere
form of the simplest of all animal cells actually remained unnoticed
until a dozen years ago.

The discovery of Max Schultze, then, was this : that in the
epithelium of the mouth and conjunctiva firstly, and then in the
epidermis of the skin, and indeed wherever there is true pavement
or scaly epithelium in many layers, the second series upwards of
cells have this peculiar character. Their surface is furnished with
short projections, which are apt to appear as prickles ; while some-
times there are ridges (reefs) marking portions of the cell with
parallel groovings (see drawing). The lowest layer of epidermic
cells consists of elongated vertical palisading-like elements, between
and underneath which lie germinal masses of indeterminate form.
Next above, and completing what was called “ rete mucosum,” is a
succession of layers of spheroidal cells, becoming more and more
flattened until they cohere under the form of mere scales into
cuticle on the skin, or in a less firm manner in transitional situa-
tions like the mouth, conjunctiva, &c. It is these latter layers
which are mostly spinous. There is some difficulty in seeing this
well in thick skin. It was already noticed by Max Schultze, that
the diseases involving the true skin showed the prickle-cells well ;
and other observers, especially Cornil and lianvier, have followed in
the same line (Fig. 1).

On Conjoined Epithelium. By S. Martyn. 61

The anatomical structure, then, has been described thus : the
cells are covered more or less with spines, which, when the cells are
isolated, show as marginal prickles ; and if the covering pressure
chance to be nil, as besetting the surface. The spines are sharp-
pointed, with a broadish base ; and all observers, I believe, describe
them as interlocking with the teeth of the nest cells, thus giving
the characteristic cohesion. Max Schultze compares this to the
intermingled bristles of two brushes put together. Banvier speaks
of the cells as soldered by the interlocking teeth (“ les dentelures
au moyen desquelles elles sont engrenees et soudees”). Strieker
uses the same phrase, and Rindfleisch compares their union to
“ a suture ” ; and I learn that the well - known Edinburgh pre-
par ateur Mr. Stirling, discovering them nine years ago, thought
them like “ watch- wheels ” (see Fig. 1).

At first sight, this all seems satisfactory enough ; but it is just
as to the simple nature and plan of these processes that I venture
to join issue with all observers to whose works I have been able to
obtain access. So long, namely, as I looked at the contact between
any two of these cells as that of toothed wheels, they really seemed
to interlock. I confess, however, to a rooted distrust of real pro-
cesses of definite form as being projected from a cell-wall of formed
material, this having no analogy with the many changes of form in
germinal or bioplastic matter. As far back as I860, when the
language of, I believe, all the books was of processes sent out by
cells, I ventured to dissent from such views, and, in a paper on Con-
nective Tissue published in Beale’s ‘Archives,’ described cell-processes
as being “ spun out ” by a receding body. This view is now
generally accepted. It seemed, therefore, to me worth inquiry,
whether these prickles were really processes which interlock, or
whether they were really continuous delicate bands uniting cell to
cell. In an epithelioma of the lip, and in a section of a hard
preputial chancre, I found instances of a rich development of the
prickle-cell. Probably, just as on a nasal polypus the ciliated
epithelium often becomes monstrous, many fine examples of these
cells may be encountered where there is unusual setting free of
formative force.

In the example (Fig. 2), the cell (a) is incontestably united by
bands to its neighbours, and the decisive experiment has been
made ; for, where these bands have broken across, the remaining
stumps have become prickles ; but where (two cells touching) the
teeth seem to have strongly dark ends (Fig. 2, h), I believe this
effect is universally an optical illusion, and that the dark spot is the
cavern between bands (b). On the other hand, where (two cells
touching) the ordinary light spines seem to be so truncated, a very
careful view will show that the light track may be followed from
one cell to the next, if I may use the illustration, like walking

f 2

62

On Conjoined Epithelium. By 8. Martyn.

across on a plank. In some cases, however, pointed teeth may be
seen at touching cell-margins, as in Max Schultze’s original plate.
But it is an illusion, in my opinion, to see in this appearance a true
second set of interlocking teeth, the outlines of which correspond
precisely with the first. Bather let it be granted that prickles are
broken bands of union in all cases, as we know they are in (e. g. a,
Fig. 2), and then the whole thing becomes intelligible. In a
microscopic preparation thin enough to be seen well with 1000
diameters, most cells are partly isolated, and consequently broken
bands, i. e. prickles, abound, and those near the outer margin of the
cells lie as detached teeth touching from each cell-wall, or even
interlocking in some instances. Meanwhile the cell-margins of
real contact deeper down are united by unbroken bands.

So much for the prickles ; and next as to the “ furrows,”
“ reefs,” “ ribs,” or “ ridges ” (see Fig. 1, a , and Fig. 2, c). I con-
fess that at present the only explanation which occurs to me is
founded on an insufficient number of observations. As a conjecture
supported by some instances, I would suggest that these are
stretched hands often broken off at one end, and lying parallel on
the cell-wall. They are beautifully seen with careful oblique
illumination under high powers.

This peculiar cell-structure which we have been describing may,
then, be supposed to originate in this sort of way. In the lowest
cell-layer of epithelium there are found the newly grown, long,
vertically placed cells, side by side in contact. When these have a
somewhat permanent character, as in many fishes, the next layer of
cells consists of spheroidal cell-forms which have resulted from
division or budding, and consequent “ fissiparous ” multiplication or
budding of a new progeny. In all this there is a tendency of
dividing cells to remain, at points, united by threads of formed
material of hard cell-wall ; e. g. amongst these very layers are
often found large and branched pigment-cells united by long
delicate threads. Thus I imagine the cells of rete mucosum, in
multiplying originally by subdivision, retain numerous points of
incomplete severance, and these points of cohesion are dragged out
and become the uniting bands. These, when severed by any acci-
dent, assume the characteristic form of “ prickles.” In the normal
ascending series, these cells, becoming older and flatter, lose all
surface connection, and in the cuticle are simple polyhedral horny
blocks. The uniting agency of these cells is a firm one ; for in a
scraping from a tumour section, as noticed by Banvier, they almost
always hold together strongly in groups. It is a firmer union than
I should expect from any interlocking teeth, but of course one
which would naturally result from uniting bands.

Lastly, as to the pathological anatomy. The primary meaning
of the presence of these cells is an abnormal formative activity of
the lower cells in the rete mucosum ; and the occurrence of rib and

PLATE CXI I

The Microscopic Germ Theory of Disease. By II. G. Bastian. 65

prickle cells may be taken as indicative of this structure having
become involved. In epithelioma occurring in connection with
flattened epithelium, both lobular and tubular, they mostly occur.
Their development seems to be in direct ratio to the vigour of
growth present, and accordingly they were very large in granula-
tions snipped from a perineal fistula. Papilloma and rodent ulcer
afford fine specimens ; and probably always the best occur in
diseases of the transitional epithelium extending from the lips to
the cardiac orifice, and on the conjunctival, anal, or preputial
epidermis. I have found them unusually fine in a section of
preputial chancre. I believe it to be the opinion of Professor
Lister, who discovered these cells independently, and named them
“ echinate,” that rodent ulcer, when they are present in it, should
be considered as allied to, if not identical with, epithelioma. The
presence of prickle-cells in cylindroma leads me strongly to doubt
the origin of that form of cancer from the sudariparous glands,
according to the received notion. But, as I indicated at first, the
real meaning, for medicine and surgery, of these curious cells,
remains to be investigated ; and it is necessary that some one should
do that for their origin, varied forms, monstrosities, and pathological
distribution which has been so laboriously accomplished for their
anatomy in fishes and amphibia by Professor F. Schultze. My
present attempt has been, so far, merely to see more of the true
character of their intimate structure, and, if possible, to determine
the true mode in which they are united together. — The British
Medical Journal, June 26.

DESCRIPTION OF PLATE CXII.

Fig. 1. — Epidermic “prickle and ridge” cells; or “spinous,” “furrowed,” or
“ ecbinate ”

а. Papillary tumour of tongue.

б. Human epidermis (Max Schultze).

c. Ext. layer, middle cells — Cornea of pig : Strieker and Rollett.

d. Cellules dentele'es of cylindroma; Cornil and Ranvier (1869).

„ 2. — Conjoined epithelium (1000 diameters).

VII. — The Microscopic Germ Theory of Disease ; being a Discus-
sion of the Delation of Bacteria and Allied Organisms to
Virulent Inf animations and Specific Contagious Fevers. By
H. Charlton Bastian, M.D., F.Pi.S., Professor of Patho-
logical Anatomy in University College.

When honoured by a request from the Council of this Society,* a
few weeks since, to open a debate during the current session, com-
pliance with such a wish was regarded by me as a professional
duty. I was compelled, therefore, to do the best I could with the
short time and limited leisure which presented themselves, though
* An address delivered before the Pathological Society of London.

6G The Microscopic Germ Theory of Disease. By H. G. Bastian.

these, I regret to say, have proved insufficient to enable me to
bestow the attention I should have desired upon the vast accumu-
lation of writings directly or indirectly related to the subject
selected for discussion, and quite insufficient also to enable me to
throw light upon it, to the extent I should have wished, by certain
new observations of my own. The subject, however, large as it is
— and consequently difficult to be dealt with satisfactorily in the
space of one hour — seemed to recommend itself for several reasons :
(1) It is a question lying at the root of the pathology of the most
important and most fatal class of diseases to which the human race
is liable — diseases which cause nearly one- fourth of the total number
of deaths in this country. (2) It is a subject important alike to
those engaged in almost every department of our profession. And
(3) it is one which I happen to have very carefully considered for
several years, and for the elucidation of which I was tempted in
1869 to undertake long and laborious investigations, though these
may have seemed to many to have little practical bearing upon the
science of medicine.

The subject of the relation of the lower organisms to disease
has, moreover, a growing importance. The notion that there is a
distinct causal relation between the two — though it has long existed
in one form or another — is one which has been spread enormously
within the last few years, partly owing to our increase of knowledge
concerning these low organisms, and partly because of their ascer-
tained presence in numerous diseased tissues and exudations.
Medical hterature both at home and abroad, now, in fact, teems
with papers and memoirs bearing upon this relation, and such
communications rapidly increase in number year by year.

In the short time allotted to me to open the debate, I shall be
able to make specific allusions to but few of these contributions, as
it would seem better to keep the broad issues well in view in my
opening statement, and reserve questions of detail, as these may be
taken up by other speakers and subsequently commented upon if
necessary.

The one common and distinguishing feature peculiar to all the
diseases whose pathology we are now about to consider is their
“ contagiousness.” An individual affected by either of them throws
off’ particles from the region specially affected, or from many parts
of the body, and these particles, on coming into contact with suit-
able surfaces in other persons, may incite similar local or general
diseases, though such results do not invariably follow. This pecu-
liarity, by means of which such diseases are spread amongst the
members of a community, was, even in the time of Hippocrates,
compared to the property by which one fermenting mass may
communicate its state of change to another mass of fermentable

The Microscopic Germ Theory of Disease. By H. C. Bastian. 67

material. Throughout all intervening periods such an analogy has
never been lost sight of ; it has rather been more and more strongly
dwelt upon. Thus, more than two centuries ago, we find, as has
been recently pointed out, Robert Boyle, one of our great English
philosophers, and himself a pioneer in scientific investigation, giving
strong expression to the then current view : “ He that thoroughly
understands,” he says, “ the nature of ferments and fermentations
shall probably be much better able than he that ignores them to
give a fair account of several diseases (as well fevers as others)
which will perhaps be never thoroughly understood without an
insight into the doctrine of fermentation.” Again, in more recent
times, it was doubtless under the influence of a belief in the same
analogy between fermentations and the class of diseases of which I
am about to speak that the term “ zymotic ” was proposed by Dr.
Wm, Farr, and adopted as a general designation under which nearly
all these diseases might be included. The consequence of the
adoption of this nomenclature has been that views as to the nature
of the infecting something, or contagium , have since been so power-
fully influenced as to be actually led by views at the time enter-
tained concerning the nature of ferments — the relationship supposed
to exist between zymosis and fermentation has indeed been stamped
and ratified by the very general consent of the profession.

Omitting for the present any remarks as to the real strength of
this analogy, I would merely further point out that the foundations
of the “ germ theory of disease,” in its most commonly accepted
form, were laid in 1836 and shortly afterwards. The discovery at
this time of the yeast plant by Schwann and Cagniard-Latour soon
led to the more general recognition of the almost constant associa-
tion of certain low organisms with the different kinds of fermenta-
tions. But it was not till twenty years afterwards that Pasteur
announced, as the result of his apparently conclusive researches,
that low organisms acted as the invariable causes of fermentations
and putrefactions ; that these, in fact, though chemical processes,
were only capable of being initiated by the agency of living units.
If, in accordance with this somewhat narrow and exclusive view,
living units were to he regarded as the sole producers of fermenta-
tion and putrefaction, then they were sole ferments. The extension
of this doctrine by medical men to contagious diseases, in face of
the analogy sanctioned by the use of the term “ zymotic,” became
only too easy. It was obviously nothing but the logical outcome
of the two sets of views to hold that low organisms were the true
contagia, or sole “ germs ” of the so-called zymotic diseases.

It so happens, therefore, that the very exclusive notion just
mentioned as to the nature of contagia is at present almost as
deeply rooted in the minds of the majority of writers on epidemic
diseases and contagious fevers as was the opposite notion, founded

G8 The Microscopic Germ Theory of Disease. By II. C. Bastian.

upon the physico-chemical doctrine of Liebig, some twenty years
ago. Then a ferment was regarded as a portion of organic matter
(not necessarily living) in a state of molecular change (“ motor
decay ”), which, by virtue of its own unstable nature, was capable
of communicating molecular movement (chemical change) to other
unstable or fermentable mixtures. This broader notion was pro-
mulgated by Liebig at a time when less was known than at present
as to the constant association of low organisms with the processes
of fermentation and putrefaction. The nature of this relationship
was, in fact, never adequately grappled with by him. Still, views
of the kind promulgated by Liebig would not give anything like
the same support to the germ theory of disease as that afforded
by the doctrines of Pasteur. Those who have adopted and deve-
loped Liebig’s views now hold that living organisms, though they
may operate as ferments, act in this capacity merely by virtue of
the chemical changes which the carrying on of their growth neces-
sitates ; and that other chemical changes taking place during the
decay of organic matter may make fragments of it (in the dead
state) almost equally capable of initiating fermentative changes in
suitable media ; whilst in either case bacteria or allied organisms
are prone to be engendered as correlative products.

In the present day, therefore, two questions seem to need the
serious consideration of medical men. In the first place, it may be
asked, Are we justified in relying so strongly upon the analogy
between fermentation and zymosis? Secondly, we may inquire
whether the researches by which Pasteur claims to have established
the sole nature of ferments are so conclusive as they have been
commonly regarded ? In reply to the first question, certain quali-
fying considerations will hereafter be stated, though it may be at once
admitted that the analogy is so strong as to make it likely to continue
to exercise a very considerable influence upon medical opinion. It
therefore becomes all the more necessary for medical men to look
to the foundations of Pasteur’s doctrine, if they are not prepared
blindly to follow his dicta on a subject which is of so much impor-
tance for medical science. It was with this view that I undertook,
a few years ago, and shortly after I had been called upon to teach
pathology, a series of investigations bearing upon this subject. In
consequence of this work I was compelled, as others had been, to
refuse assent to the exclusive doctrines of Pasteur concerning the
nature of ferments. I do not enter upon this discussion now. I
maintain, however, that my own investigations and those of others
show that units of living matter are not sole ferments, since fer-
mentation and putrefaction may be initiated in their absence, and
since it can be shown that mere particles or fragments of organic
matter may act in this capacity. For a brief exposition of the
grounds of this belief I would refer those interested in the matter

The Microscopic Germ Theory of Disease. By II. C. Bastian. 69

to my recently published work, ‘ Evolution and the Origin of
Life.’

Some time must be allowed to elapse before anything approach-
ing to general agreement can be expected on such a subject ; and
meanwhde, standing as we do in the face of opposite doctrines as to
the nature of ferments, we are free to look into the question of the
relation of the lower organisms to disease on its own merits, apart,
that is, from the overweening influence of any general theory of
fermentation.

Leaving on one side, therefore, the influence of the analogy
deemed to exist between the process of fermentation and that of
zymosis, we may ask what other general evidence is forthcoming
in favour of the notion that contagia are low organisms or living
units, rather than dead organic particles from altered tissue-ele-
ments, or complex chemical compounds of alkaloidal constitution
engendered in the tissues or in some of the fluids of the body. The
consideration of this question may be introduced by a quotation
from Dr. Burdon-Sanderson’s valuable Keport on the “ Intimate
Pathology of Contagion.” * He says : “ There are two obvious
objections which stand in the way of the acceptance of any chemical
explanation of the phenomena of contagion. The first is, that the
multiplication of contagium in the body of the infected individual
is a process which cannot be compared to any which is brought
about by chemical agencies independently of organic development.
The second is, that all contagia possess the power of retaining their
latent virulence for long periods (often resisting the most unfavour-
able chemical and physical conditions), and only show themselves
to be what they are when they are brought into contact with [the]
living organism. Outside of the body the contagious material
withstands all those changes to which, on chemical grounds, we
should expect it to be liable ; while in the body it manifests a
degree of activity, and gives rise to an amount of molecular dis-
turbance, which is quite as unaccountable Neither of these

difficulties stands in our way if we suppose that the contagious
process is connected with the unfolding of organic forms.”

Now, though this is about as strong a statement as can be
made, from an a priori point of view, against the mere chemical
action of contagium, and in favour of a germ theory, I must confess
that neither of the considerations seems to me to carry very much
weight with it. I should be inclined to say, in reply (1) that proof
is altogether wanting of the “ multiplication of contagium ” in the
body in the same sense that a living unit multiplies ; and that
there are physico-chemical processes which may illustrate what
occurs when contagium increases within the system. Instead of
being an increase by continuous organic development and multipli-
* ‘ Twelfth Report of the Medical Officer of the Privy Council, 1S70,’ p. 243.

7 0 The Microscopic Germ Theory of Disease. By E. C. Bastian.

cation, it may be that contagium augments by some such process
as that by which crystals of sulphate of soda increase or “ multiply ”
when a fragment of such a body is thrown into a complex fluid
containing its component elements. This is confessedly a very
imperfect illustration, and one to -which I resort merely to indicate
the possible occurrence of another mode of increase of contagium
within the body ; though in an infected animal such increase may
occur in a much more subtle manner, owing to the fact that fluids
altered, directly or indirectly, by the original contact of contagium
with some part of the body, are either locally or generally brought
into intimate relation with the active, though modifiable, living
units of the various tissues. And (2) in reply to Dr. Sanderson’s
other objection, which stands, as he supposes, in the way of any
chemical explanation of the phenomena of contagion, I should say
that, although our knowdedge is at present extremely vague con-
cerning the power possessed by the various contagia of retaining
their virulence for long periods, and of resisting unfavourable
physical and chemical conditions, we have no reason to believe that
the more complex combinations of which living matter is composed
are capable of resisting influences which would prove destructive to
less highly complex not-living substances, such as snake -poison,
wToorara, or other compounds of this class. The general evidence
is therefore, as I read it, certainly not more favourable to a vital or
germ theory than to a physico-chemical theory as regards the
nature and action of contagia.

I should here point out, however, that under the term “ germ
theory ” two distinct views are included, each having their advocates
amongst distinguished members of this Society. The side to which
Dr. Sanderson leans is sufficiently obvious. Speaking of contagious
particles, he says : * “ With reference to their mode of action, we
have examined into those considerations which seem to render it
probable that they are organized beings, and that their powers of
producing disease are due to their organic development ; and we
have accepted this doctrine as the only one which affords a satis-
factory explanation of the facts of infection.” t

This is the doctrine with which we are at present especially
concerned, though it may be well for me to say a few words con-
cerning the other sense in which a “ germ theory of disease ” is
maintained by a distinguished member of this Society. Dr. Beale
says : + “ We have therefore now to inquire what is the material
substance which passes from the diseased to the healthy organism

* Loc. cit., p. 255.

t These words occur in a summary which, it is only right to add, was im-
mediately prefaced by the following statement : “ The sentences which follow
must therefore be accepted by the reader as nothing more than indications of the
questions we are trying to solve, or as forecasts of what we hope to establish or
disprove by experiment.”

X * Disease Germs, their Real Nature,’ 1870, p. 5.

The Microscopic Germ Theory of Disease. By H. C. Bastian. 71

in small-pox, in measles, in scarlet fever, and other allied contagious
diseases from which man and domestic animals suffer so severely.
The material in question grows and multiplies and produces its
kind, as all living things do, and as nothing that does not live has
been proved to he capable of doing. We may therefore conclude
that it is living matter.” And as to the derivation of such matter,
Dr. Beale says, “ a disease germ is probably a particle of living
matter derived by direct descent from the living matter of man’s
organism,” though he supposes it to be altered and degraded as
regards formative power by previous rapid multiplication of the
tissue-elements or particles from which it has been derived. In
many respects I am disposed to assent to this view, so long as it
is not taken in too exclusive a sense. I will now, however, only
mention what I consider to be its weakness. It seems to me that
proof is wholly wanting as regards the statement which I have had
printed in italics. That there is an enormous increase of germinal
particles in the blood and in many of the tissues in these specific
contagious diseases, Dr. Beale has helped to show us by his valuable
researches upon the pathology of the cattle plague and other allied
affections ; but that such germinal or living particles are in any
direct sense the descendants of the particles which acted as con-
tagia, or, in fact, that the contagious particles really multiply to
any extent in the body ; these are propositions which at present
appear to me to he wholly devoid of all proof. I and other patho-
logists are free to hold that contagious particles, whether composed
of living or of not-living organic materials, may initiate changes in
the tissues and fluids with which they come into contact, which
changes may be exaggerated as they spread, so as at last to
implicate the blood. And as one result of this altered constitution
of the nutritive fluid and of the general febrile condition simul-
taneously excited, we may get that undue proliferation of tissue-
elements and multiplication of their products which appear to go
on in the blood and in the various tissues of persons suffering from
these febrile diseases. Beyond these surmises we seem also to have
to do with mere conjecture rather than with established facts.

Leaving this aspect of the question, therefore, I now turn to
the special subject of this debate, viz. the truth of the germ theory
as it is ordinarily understood, or the relation of the lower organisms
to virulent inflammations and then’ sequel® on the one hand, and
to specific contagious fevers on the other.

Applicability of the germ theory to virulent inflammations and
their sequelae ( gonorrhoea , pundent ophthalmia, erysipelas,
hospital gangrene, puerperal fever, pyaemia, septicaemia, fc.)

A few years ago no one would have thought of connecting the
contagiousness of gonorrhoea or of purulent ophthalmia with the
presence of bacteria. The respective secretions were known to

72 The Microscopic Germ Theory of Disease. By H. C. Bastian.

contain some poisonous element either in the form of a chemical
compound or altered product of tissue multiplication (pus), which,
when it came into contact with a healthy mucous membrane, was
capable of acting as a specific irritant, and there exciting a similar
morbid process. It is by no means certain, however, that some
pathologists w'ould not at the present time connect this process
with the presence of bacteria in the contagious fluids. Such a
point of view has, indeed, been directly fostered by doctrines
recently put forward by an eminent pathologist, Dr. Burdon-
Sanderson. At this Society in 1871, whilst, strangely enough,
professing to be indifferent to the mode of origin of bacteria, Dr.
Sanderson said : “ They afford a characteristic by which we may
distinguish the products of infective inflammation from those which
are not infective.” And in a more recent paper on “ The Infective
Product of Acute Inflammation,” * referring to his previous re-
searches, he says it was inferred from these that, “ if infective
agents are particulate, they are probably comprised in that group of
bodies to which I then applied the term microzymes, recognizing
their identity with the zoocjlsea of Cohn, the micrococci of Hallier,
and the various forms described by other authors under the terms
bacterium and vibrio .” And he then adds, as the result of subse-
quent investigations, the following passage : “ With reference to
these organisms, two entirely new and most important facts have
been demonstrated by the observations to he now recorded. It has
been discovered (1) that in all acute infective inflammations micro-
zymes abound in the exudation liquids ; and (2) that the same
forms are to be found in the blood of the infected animals.” And
when Dr. Sanderson subsequently adds “ that the relation _ of in-
tensity between different cases of septicaemia and pyaemic inlection
is indicated by the number and character of these organisms,” hut
little doubt seems to remain concerning his views as to the causal
relationship of such organisms to the infectiousness of the inflam-
mations referred to. And this view is not essentially modified by his
subsequent concluding explanations, where he says : “ Inasmuch as
these organisms cannot have originated from the normal tissues or
juices, they must have been derived from the external moisture.”
And also, “ it does not at all follow because these organisms come
in from outside that they bring contagium along with them ; for it
may he readily admitted that they may serve as carriers of infection
from diseased to healthy parts, or from diseased to healthy indi-
viduals, and yet he utterly devoid of any power of themselves
originating the contagium they convey.” Such a doctrine still
implies that bacteria are essential to a contagious process, though
it seems to me to introduce certain very striking elements of weak-
ness into the germ theory as thus interpreted. If this theory is
* ‘ Medico-Chirur. Trans.,’ 1873, p. 351.

The Microscopic Germ Theory of Disease. By E.G. Bastian. 73

not tenable without the aid of some supplementary hypothesis, I
cannot conceive that the introduction of the one above mentioned
will be considered to have strengthened its foundations. Yet Dr.
Sanderson apparently saw the difficulty of maintaining the germ
theory in its integrity, and offered us this other view as a com-
promise. He considers it probable that, whereas true contagia,
whether living particles or chemical compounds, may be engendered
within the body in the tissues themselves, such contagia are not
able to spread either within or outside without the aid of bacteria
to act as “carriers.” But why one set of particles should need
others to carry them, or why bacteria alone should be able to bear
about these mysterious contagious poisons which they are devoid of
the power of originating, does not at all appear !

However complicated the doctrine may have been rendered,
this is still practically the germ theory ; and the same thing may
be said with reference to a view which Professor Lister seems to
entertain with some favour. He thinks that the lower fungi and
their relations bacteria may contain within themselves some chemical
compound absolutely peculiar to them, and forming part of their
substance, which may act upon albuminous compounds after the
manuer of a ferment, such as emulsin.* “ In this sense,” he
thinks, “ as intervening between the growth of the organisms and
the resulting decompositions, the theory of chemical ferments might
be welcomed as a valuable hypothesis.” This seems like the lan-
guage of concession, but, practically, it is the germ theory still, and
expressed too much, as all germ theorists who think out their views
would have to formulate them. It would be no great concession
to those who are not believers in an exclusive germ theory if, in
the light of his views as above expressed, Professor Lister were to
say that bacteria were “ carriers of infection ” ; yet the apparent
concession above referred to is no more of a concession to be-
lievers in a physico-chemical theory than the latter admission
would be.

I will, however, now briefly enumerate the evidence which
seems to me quite sufficient to disprove the probability of the
existence of any causal relationship between the lower organisms
and the diseases cited at the head of this section, and to establish,
on the other hand, the position that the bacteria met with in
diseased fluids and tissues are for the most part actual pathological
products — that they are, in fact, engendered within the body, or
are descendants of organisms owning such an origin, rather than
of previously existing organisms introduced from without. It
would take far too long were I to attempt to enter at any length
upon a consideration of this evidence. I must therefore content
* ‘ Nature,’ July 17, 1873.

74 The Microscopic Germ Theory of Disease. By II. C. Bastian.

myself with briefly summarizing the principal facts and arguments
on which a judgment may be founded.

1. The experiments of many investigators prove that the
alleged causes of diseases may be actually introduced into the blood-
vessels of lower animals by thousands without producing any dele-
terious effects in a large proportion of the cases.

2. Bacteria, if not actually to be found within the blood-vessels
of healthy persons, do nevertheless habitually exist in so many
parts of the body in every human being, and in so many of the
lower animals, as to make it almost inconceivable that these
organisms can be causes of disease. In support of this statement I
have only to say, that even in healthy persons they may be found
in myriads in and about the epithelium of the whole alimentary
tract from mouth to anus ; they exist throughout the air-passages,
and may be found in mucus coming from the nasal cavities, as well
as in that from minute bronchi. They exist abundantly amongst
the epithelial debris within the ducts of the skin, not only in the
face, but in other parts of the body. Fresh legions of them are
also being introduced into the alimentary canal with almost every
meal that is taken, whence they may perhaps readily find their way
into the mesenteric glands, if not farther within the system. And
lastly, in persons with open wounds, bacteria are constantly to be
found in contact with such surfaces, especially if the wounds are
not well cared for, though the injured person does not necessarily
suffer at all in general health.

3. It is no answer to these difficulties to say that there are
distinct species amongst these lower organisms, some of which are
harmless, though others are poisonous (or so-called “ germs ” of
disease). In support of such opinion nothing can be alleged save
some of the facts whose cause is doubtful ; whilst against such an
interpretation may be brought the experiments of several investi-
gators, showing that bacteria are the creatures of circumstance,
and modifiable to an extraordinary degree. The last position is
even admitted by Professors Sanderson and Lister. The former
acknowledges that they are “ the lowest organisms,” and that they
are “ much more under the influence of the conditions under which
they originate and are developed, than organisms of any other
class ; ” whilst Professor Lister’s own work has compelled him to
make an admission which, in the face of facts previously stated
concerning the wide distribution of bacteria within the body, seems
fatal to a consistent belief in the germ theory of disease. He says :
“ If the same bacterium may, as a result of varied circumstances,
produce in one and the same medium fermentative changes differing
so widely from each other, as the formation of lactic acid and that
of black pigment in milk, it becomes readily conceivable that the
same organism which, under ordinary circumstances may be com-

The Microscopic Germ Theory of Disease. By II. C. Bastian. 75

paratively harmless, may at other times generate products poisonous
to the human economy.” *

4. The consideration now to he mentioned suffices, in my
opinion, to complete the discomfiture of the germ theory as an
explanation of the mode of causation of the diseases with which we
are at present concerned. It is this. It has been shown, on the
one hand, that the virulence of certain contagious mixtures dimi-
nishes in direct proportion to the increase of bacteria therein ; and
on the other hand, it has been equally proved that fresh and
actively contagious menstrua lose scarcely any of their contagious
or poisonous properties after they have been subjected for a few
minutes, when in the moist state, to a temperature which no living
units can be shown to survive (212° F.), or after they have been
exposed to the influence of boiling alcohol, which is well known to
be equally destructive to all recognized forms of living matter.
Such facts have been substantiated by Messrs. Lewis and Cunning-
ham, Sanderson, and others.

Having said thus much in opposition to the germ theory, let
me as briefly enumerate the facts and arguments which seem to me
to show the real relations of bacteria and their allies to the diseases
in question. I turn therefore to the construction of an opposite
doctrine.

Admitting in part the very frequent presence of bacteria in
diseased fluids and tissues, I consider that their presence and im-
port should be differently explained. I say I admit the association
in part, though I by no means admit it to the extent alleged.
Bacteria are not, for instance, to be found in the blood of persons
suffering from pyaemia, as might be inferred from former statements
of Dr. Sanderson, which I have already quoted. My own ex-
perience in this matter seems to be entirely in accordance with
that of Professors Bilroth and Strieker. Neither do I believe that
the presence of bacteria in inflammatory fluids has the significance
which Dr. Sanderson attaches to it, since it has been ascertained by
myself and others that the exudation fluids of sick persons suffering
from diseases of a totally different type are often similarly crowded
with these lowest organisms, whilst the recent observations of
M. Bergeron t seem to show that they may be found even in
freshly extracted pus from ordinary abscesses occurring in elderly
persons.

Now, it would seem quite obvious that the consistent advocate
of a germ theory of disease can only successfully maintain such a
doctrine if he can show, amongst other things, that bacteria are
more capable of altering the character and chemical constitution of
fluids of the body than they are themselves prone to be altered by

* ‘ Quarterly Journal of Microscopical Science,’ October, 1873.
f ‘ Compt. Rend.,’ February, 1875.

VOL. XIV.

0

G

76 The Microscopic Germ Theory of Disease. By II. C. Bastian.

independently initiated changes taking place in such fluids. It
seems, therefore, like unintentionally cutting himself free from the
theory to which he has hitherto adhered, when we find Professor
Lister, in speaking of the assumed “ special virus of hospital gan-
grene,” going on to say that “ it is not essential to assume the
existence of a special virus at all, but that organisms common to all
the sores in the ward may, for aught we know, assume specific
properties in the discharges long putrefying under the dressings.”
This passage has a similar import to that of a quotation previously
made. In both a first place is assigned to the modifying influence
of altered fluids ; and however much the correctness of such a
supposition would tell in favour of cleanliness, free exposure, or
even of antiseptic dressings, it is none the less inimical to a con-
sistent holding of the theory on which Professor Lister has chosen
to base his system of treatment.

But though such statements are adverse to the holding of a
germ theory in the only form in which it may be at all tenable,
they are entirely in accordance with my own observations and views.
I maintain, in short, that even the very existence of organisms in
the fluids and tissues of diseased persons is for the most part refer-
able to the fact that certain changes have previously taken place
(by deviations from healthy nutrition) in the constitution and
vitality of such fluids and tissues, and that bacteria and allied
organisms have appeared therein as pathological products — either
by heterogenesis, or by what I have termed archebiosis, or birth
direct frorn/a fluid.

The evidence on which my belief is founded is of this nature :

1. Bacteria and their allies are found in greatest abundance
during the life of the individual in connection with dying tissue-
elements, and apparently are as plentiful within the dying epithe-
lium of the cutaneous ducts as in parts like the mouth, which are
most liable to contamination with organisms from without. Again,
they exist abundantly in and about the dying cells of bronchial
mucus, although living bacteria appear to be almost completely
absent from ordinary air.

2. The microscopical examination of such epithelial or mucous
elements also favours the notion that the contained bacteria are
products engendered within such cells rather than mere results of
an external contamination and imbibition. This opinion is based
upon the following considerations. Bacteria only appear within the
cell when it is obviously dying ; and in the case of epithelium, for
instance, they manifest themselves at first as minute motionless
particles scattered through the semi-solid substance of the cell,
where each particle grows into a distinct bacterium, which still
remains motionless, and does not appear to divide for a long time.
This is precisely similar to what I have observed over and over

The Microscopic Germ, Theory of Disease. By H. C. Bastian. 77

again, when amoebae in vegetable infusions get into an unhealthy
condition and become resolved into nests of bacteria. They may
exist for days in a state of activity with bacteria in the fluid around
them, though none are to be seen in their interior. After a time,
however, the chemical constitution of the fluid seems to become no
longer suited to the amoebae ; their activity ceases, they remain as
almost motionless balls of jelly, and soon multitudes of the minutest
particles appear throughout their substance, each of which straight-
way grows into a bacterium. The former amoeba is converted into
a mere bag of bacteria, which after a time ruptures, and thus
liberates its swarming colony of newly-engendered living units.
Multitudes of mucus-corpuscles seem to undergo the same kind of
change, so that bacterial degeneration takes place in the same
manner and is almost as typical amongst them as is fatty degenera-
tion amongst pus-corpuscles. The two kinds of degeneration,
moreover, commonly occur side by side in epithelial debris.
Bacterial degeneration takes place where the vitality of the unit is
lowered, but where it is not sufficiently degraded to permit of the
still lower and more obviously destructive process of fatty degenera-
tion ; and if anyone wishes to see it in perfection let him examine
some central portion of the kidney or other internal organ of a
warm-blooded animal five days or more after its death.

3. Bacteria are admitted by nearly all pathologists to be absent
from the blood of healthy persons during life, and yet in from
eight hours to four or five days after death, according to the
temperature of the air at the time, the previously germless blood of
all individuals may be found to be swarming with these organisms
in every stage of growth.

4. Whereas blister fluid or serum has been shown to be free
from organisms in healthy persons, I have ascertained that, given a
febrile patient with a temperature of 102° F., one can determine
the presence of bacteria, at will, in any blister-hleb which remains
intact for forty-eight hours or more, and this, too, where the patient
does not suffer from any specific fever, but merely from pneumonic
inflammation. I was led to ascertain this fact by finding, about
eighteen months ago, myriads of bacteria in all the blebs of a
patient suffering from acute pemphigus, with a temperature of 103°.

5. Lastly, as Dr. Sanderson has shown, a chemical irritant,
such as liquor ammoniae, may he introduced beneath the skin of
some of the lower animals in such a way as to “preclude the
possibility of external contamination,” and yet here, amidst tissues
which he has shown to be germless, we may thus within twenty-
four hours determine the presence of swarms of germs and
organisms in the pathological fluids effused under the influence
of the local chemical irritant.

This constitutes, as it appears to me, an exceedingly strong

g 2

78 The Microscopic Germ Theory of Disease. By H. C. Bastian.

body of evidence tending to show that bacteria are pathological
products capable of being engendered within the body after death,
or in certain situations during life where tissue-elements are dying
or where the fluids of the body are notably altered by disease.
It is true that the facts and considerations mentioned under 1 and
2 are capable of receiving another interpretation. It may be said,
for instance, and it has actually been said by Dr. Beale, that the
higher forms of life are, as it were, interpenetrated by the lower
forms of life. Speaking of bacteria and their allies, Dr. Beale
says: “I have detected them in the interior of the cells of

animals, and in the very centre of cells, with walls so thick and
strong that it seems almost impossible that such bodies could have
made their way through the surrounding medium.”* And else-
where the same observer says : “ Probably there is not a tissue
in which these germs are not ; nor is the blood of man free from
them.” Noting by the way that this latter statement does not
accord with the experience of others, I may further mention
that some distinguished pathologists, and notably Dr. Sanderson,
are also inclined to dwell strongly upon the fact of the wide
distribution of bacteria throughout the body — not believing them
to be innate or connate (in the mysterious manner imagined by
Dr. Beale), but supposing that they have been introduced from
without through certain definite channels.

Dr. Sanderson’s views on this subject, and the means by which
he supports them, are sufficiently remarkable to detain us a few
moments. If what he says f concerning the assumed easy absorp-
tion of bacteria from the intestine by lymphatics, and their sub-
sequent passage into the blood, were in correspondence with actual
facts, then in face of the habitual prevalence of such organisms
in the intestine, the blood of healthy individuals should scarcely
ever be free from them. But this is surely proving too much,
since Dr. Sanderson himself assures us that healthy blood is
germless.

Again, the other main channel by which, as he says, bacteria
may enter into the body abundantly from without is through
the bronchi and the lungs. Now, as a result of Dr. Sanderson’s
oft-quoted experiments in 1871, he claims to have proved “in
the most striking manner .... that air is entirely free from
living microzymes .” Speaking of a previously boiled Pasteur’s
solution, he says that “ no amount of exposure ” to air “ has any
effect in determining the presence of microzymes therein.” And
yet Dr. Sanderson now talks of the air which is “ entirely free from
living microzymes ” being the channel through which these organ-
isms are introduced into the lungs. It is true that in his recently
published lectures this distinguished investigator makes a tacit
* ‘ Disease Germs,’ p. 72, 1870. f 1 British Medical Journal,’ Feb. 13, 1875.

Dr. Rutherford's Freezing Microtome. By W. J. Fleming. 79

retraction of his previous statement. He says, in fact, in his first
lecture : * “It must not be understood that bacteria do not exist
in the atmosphere. But their existence there in an active form
strictly depends on moisture. They attach themselves without,
doubt to those minute particles which, scarcely visible in ordinary
light, appear as motes in the sunbeam or in the beam of an
electric lamp. It is by the agency of these particles that they
are conveyed from place to place.” Elsewhere in the same lecturet
Dr. Sanderson repeats the statement that “solid materials in
suspension in the air ” play a principal part in the conveyance
of bacteria from place to place, and claims that this was shown
by the very experiments of 1871, which then entitled him to
express the conclusion that “ air is entirely free from living micro-
zymes.” All I can say is, that I have not been able to find in
Dr. Sanderson’s writings any explanation of this marked change of
view, and that I certainly know of no experiments of his which at all
establish the fact (extremely difficult as it would be to establish)
that bacteria or their germs are conveyed from place to place on
the surface of aerial particles, just as his assumed particles of
contagion are supposed to be borne about by bacteria themselves.
If the theory be true, the conditions for aerial locomotion of conta-
gion are, at all events, getting a little complicated. The contagious
particles cannot move about alone : they must engage the services
of bacteria to carry them, and these latter porters are unfortu-
nately so delicately constituted that they cannot exist alone in the
atmosphere ; they can only survive when borne on the backs of
some moisture-containing fragments of atmospheric dust, which,
though so much heavier than the contagious particles themselves,
are freely borne through the air in all directions !

(To be continued.')

VIII. — A Modification of Dr. Rutherford's Freezing Microtome.
By William James Fleming, M.B.,

Assistant to the Professor of Physiology, Glasgow University.

The advantages derived from the examination of tissues in the fresh
state are universally acknowledged by microscopists, but no means
have hitherto been devised by which, in many instances, this can
he effected except the hardening influence of cold. The difficulty
of making frozen sections has prevented this process from being
adopted with the frequency to which its merits seem to entitle it.
A great advance in the mechanical appliances at our disposal for
* Loc. cit., Jan. 16, 1875. f P. 70.

80 Dr. Rutherford's Freezing Microtome. By W. J. Fleming.

this purpose was the Stirling section-cutter surrounded by a
freezing mixture contrived by Dr. Eutherford, and described in
the ‘Lancet’ in 1873, vol. ii., p. 108. The objection to it is its
cumbrousness and the difficulty which its size adds to the necessary
manipulations. This same fault entails that the whole machine be
firmly fixed — an arrangement which, in my opinion, very much
reduces the value of any section-cutter, as it deprives the operator
of the great assistance to be derived from the movement of the sec-
tion upon the razor. It often occurs in practice that, if an imbedded
object is held in the left hand, valuable assistance in making fine
sections can be derived from slight movements of rotation, elevation,
or depression, given to overcome some hitch which is noticed in the
cutting of the razor edge. If the object to be cut is fixed, this
power is of course lost. These considerations have led me to devise
the instrument figured here.

The principle adopted is to freeze the substance in a Stirling’s
section-cutter by causing fluid, reduced to a low temperature, to
flow round it. The mechanical means by which this is effected
will be easily understood by reference to the accompanying section.

Fig. l.

Scale one-third actual size.

Fig. 1. — A, Cylinder of ordinary Stirling’s section-cutter, a a, Plate of ditto.
°6, Handle of brass and iron covered with vulcanite, c, Brass chamber sur-
rounding A entered at top and bottom by two tubes, cl and e. /, Movable bottom
plate (Fig. 2, plan of this plate), which, when the nuts h h are screwed up, fits
water-tight by the aid of two india-rubber rings sunk in grooves (g g, g g).
k, One of the two legs forming with the handle a tripod stand. I, Beak to
rest upon table or block when in use.

The manner of employing it is as follows : The substance to be
cut is placed in the cylinder, about half an inch from the top, im-
bedded in scraped potato, muscle, brain-substance, or other suitable
material. The tube e is connected by an india-rubber tube with
a worm of block tin immersed in a freezing mixture, and placed a
few inches higher than the section-cutter. The other end of the

On the Origin of Life. By Lionel S. Beale. 81

worm is connected with a large funnel suspended above. An india-
rubber tube is adjusted to d, and led into a suitable receptacle. Into
the funnel is now poured a quantity of weak spirit, just strong
enough not to freeze at 0°F. (one part methylated alcohol and two
parts water is sufficient). This of course runs through the worm,
and is thereby reduced to a low temperature (say 10 J F.). Then
it fills the chamber c, running in as we saw at the lower tube e,
and out at the upper tube d into the vessel placed for its recep-
tion. As soon as most of the spirit has come through, the india-
rubber tube conveying it away is compressed, and the contents of
the vessel are returned to the funnel (this time at a very low tem-
perature). After this has been repeated a few times (in about fifteen
minutes) the sections may be cut with a razor with perfect facility.

The instrument is provided with two legs Ic, which with the
handle form a tripod upon which it stands very conveniently. The
upper plate a, is prolonged into a beak Z, which is rested upon a
table or block, while the instrument, being grasped by the handle, re-
mains completely under the control of the operator. The vulcanite
handle, from its non-conducting properties, prevents the heat of the
hand influencing the result or the cold of the instrument affecting the
hand. The spirit, of course, does over and over again, and is there-
fore no appreciable expense. Two steel guide-rods are introduced
into the cylinder to prevent the piston rotating. In practice I find
that if the screw is kept well oiled, there is no necessity for the
introduction of spirit around the piston-rod, as recommended by
Dr. Rutherford.

The advantages claimed for the instrument are, that it enables
us to make fine sections of the softest tissues at once, and while
they are in the fresh state. It is very handy, and when the subsi-
diary apparatus is once arranged, can be employed at any time with
little trouble. It can be used as an ordinary section-cutter, and
indeed for this purpose seems peculiarly adapted, as the arrange-
ments before referred to enable it to be retained under the control
of the left hand, an advantage not possessed by any other form of
section machine with which I am acquainted. The microtome can
be procured from Mr. Hilliard, Renfield Street, Glasgow. — The
Lancet , June 19, 1875.

IX. — On the Origin of Life. By Lionel S. Beale, M.B., F.R.S.*

The far-fetched conjectures seriously advanced by some physical
speculators concerning the origin of life serve to show what extreme
difficulty has been experienced by those who have attempted to con-
struct a plausible hypothesis by which the conversion of the non-
* Portion of a lecture delivered before the Royal College of Physicians.

82 On the Origin of Life. By Lionel S. Beale.

living into the living might he reasonably accounted for. One great
authority, dissatisfied with every suggestion, and being evidently
convinced that no physical explanation of the origin of life upon
our globe would ever be discovered, despairingly submits to us the
proposition that life did not begin here at all, and that our earth
was first peopled by the offspring of germs brought to us upon a
fragment broken off from some distant orb that teemed vtitli life.
Whether even the simplest living forms would have survived after
such a ride through space unfortunately had not been determined
by experiment, so the idea of our fauna and flora being derived from
those of another world found little favour, and probably all who
have considered the subject would now agree that it is probable
that life-forms originated upon our globe, though there might be
great difference of opinion concerning the precise mode of their
origin.

“Evolution” is now supposed to solve the difficulty of life form-
ation ; but this term has had at least two meanings assigned to it.
By some it has been restricted to the living world, while others have
given to the term “ evolution ” a much wider signification, and have
maintained that it should include not only the evolution of living
forms from pre-existing living forms, but the formation of the living
out of the non-living. There is, it is scarcely necessary to point
out, the widest possible difference between these two doctrines ; for
while the one teaches that all living forms came direct from living
matter without accounting for the origin of life at all, the other is
a tenet of the fiery-cloud philosophy which teaches as a cardinal
point that the evolution of life is but one of the great series of
changes in which the evolution of the cosmos is comprised. But
surely such an idea may, for the present, be regarded as a conjec-
ture so extravagant as to be unworthy of serious consideration.
Facts are wanting, and the arguments advanced in favour of the
hypothesis are such as cannot have much weight, since it has been
deemed necessary to bring forward, in their support, utterances of
a prophetic character.

If, then, evolution is restricted to the living world, the origin
of the first living thing will be still unaccounted for. The presence
of a very simple living form seems to have been assumed ; but
whether that being came of itself from the non-living, or arose in
consequence of some prior changes, or was formed by an act of
creative interference, is not suggested by the terms of the particular
form of the hypothesis under consideration. Neither is the precise
nature of the first living substance indicated, and we are even left
in doubt whether one or two or many forms of living matter came
into existence at the first formation of life.

Now with reference to the origin of the first living matter,
several not improbable suggestions present themselves to the mind,

On the Origin of Life. By Lionel S. Beale. 83

in all of which, however, it is assumed that the change from the
non-living to the living was sudden and abrupt, and not gradual.

First, we may conceive that one form of living matter was pro-
duced direct from the non-living, and that from this all future living
was evolved.

Secondly, we may prefer to imagine that more than one form of
life originated from the non-living at or about the same time.

Thirdly, we might think it more in accordance with facts to
conceive that several different kinds of bioplasm originated in the
beginning of an epoch of life, from which all life of that epoch was
derived. New forms originating anew in the next epoch, the results
of evolution from the first gradually dying out as those of the
second epoch increased and became dominant. As life-epoch suc-
ceeded epoch, new forms of bioplasm may have appeared as old
forms of life died out.

But the above by no means exhaust the list of what I would
term the reasonable hypotheses concerning the origin of life that
may at once be suggested. All of them involve in some form or
other the admission of a remarkable change in capacity or power
not to be accounted for by physics. In all, the communication to
matter of powers or forces which it did not always possess, and
which it is conceivable might never have been communicated at all,
is suggested.

Whether this communication of new powers occurred once only
or was repeated at many successive periods in the remote past, —
whether it he reasonable to consider a recurrence of the process in the
future as probable or improbable, I shall not now venture to discuss.

What I particularly wish we should keep before our minds is
that facts and arguments render it much more probable that the
passage from the non-living to the living is sudden and abrupt,
than that there is a gradual transition or scarcely perceptible grada-
tion from one state to the other. I should, however, clearly state
that this inference is in opposition to the views of many authorities,
and in particular is opposed to the clearly expressed opinion of one
of the greatest discoverers and most acute thinkers of our time, who
maintains that the conversion of physical into vital modes of force
is continually taking place. It is suggested that the change from
non-living matter to living matter is a transition easily effected and
continually occurring. Of the facts in support of so startling a
proposition I confess I am ignorant, nor have l succeeded in my
efforts to discover any facts in the writings of those who appear to
have accepted the conclusion in question, which has never failed to
enlist advocates in its support from the time when it was believed
that highly complex living forms were produced from earth or dew,
to the present day, when the advocates of the doctrine are so
terribly restricted in the discovery of parentless living particles.

84 On the Origin of Life. By Lionel S. Beale.

We have now reached the point where we are brought face to
face with the modern developments of the old doctrine of spontaneous
generation.

I cannot but remark that the more minutely investigation is
carried out — the more thoroughly and intently facts hearing upon
the matter are examined — the more improbable, in my judgment,
does it appear that any living form should be derived direct from
the non-living. Notwithstanding all that has been recently written
upon this subject, I cannot but feel surprised that at this time many
good reasoners should decide in favour of the de novo origin even of
bacteria. Whether we consider the matter from the experimental
side only, or study the evidence obtained in a general survey of
nature, or carefully reflect upon the facts learnt from investigations
concerning the properties of living and non-living matter, with the
aid of the most perfect instruments of minute research now at com-
mand, or from other standpoints, the conclusion seems to me
irresistible that the verdict of a jury of well-educated men would
be against the direct origin of any form of living from any form of
non-living.

Driven from one position to another, the advocates of spon-
taneous generation have entrenched themselves in the unassailable
stronghold of experimental investigation. Here they may hold their
own for any length of time, for no one can say what may not be
demonstrated by new experiments in the time to come. Nay,
although the conflicting results of different skilled experimenters,
whose experiments have been conducted upon the same principles and
professedly in the same way, even to the minutest details, may shake
the confidence of some in the experimental method of inquiry, it is
certain that the teachings of experiment will finally prevail over all
other information.

But the modern advocate of abiogenesis should be skilled not
only in explaining facts, but in explaining facts away. The fact
that bacteria germs exist in all parts of the higher organisms, in
the most internal parts as well as upon the surface of man’s body,
is to be accounted for by their spontaneous origin ! Although
millions are to be found about the mouth and upon the surface, and
it can be shown that it is easy enough for them to get from the
outside amongst the tissues within, we are asked to believe that
those inside originated there direct from the non-living, or, as an
alternative proposition, that they were derived not from parental
bacteria, but by transmutation from some of the constituents of the
tissues, on the principle that a living fungus comes not from a
fungus germ, but from a dying tree. The next suggestion will be
that man, after all, is but an aggregation of lower forms, peculiarly
conditioned for a time, but which assume their ordinary forms when
their environment shall be modified, as it must be at death.

85

On the Origin of Life. By Lionel 8. Beale.

Erroneous conclusions of many kinds have been employed as
facts in support of abiogenesis. When one finds that it is believed
that fungi may be developed from oil-globules and other living
organisms of a much higher type, produced without parents out of
organic matter, one fails to see any limit to the support that may
be gained to the cause. Volumes of facts and arguments hitherto
advanced in favour of abiogenesis may be republished without in
the slightest degree modifying the real state of the case. What is
now required is well-devised experiment, and that is all. No resus-
citation of old arguments and doubtful facts, however ably the task
is performed, will in the slightest degree increase the cogency of
experimental proof, and in the absence of new experiment such facts
and arguments will avail nothing.

I think we may be satisfied that before long the advocates of
spontaneous generation will have to rely upon the production of the
lowest organisms only. The only view in any way tenable at this
time is, that such organisms as bacteria are the only ones that can,
under any arrangement of conditions possible to an experimental
inquirer, be formed anew, and that these alone, at any period of the
world’s history, sprang direct from the non-living. All are of
extreme minuteness, many of the forms being so very small that
they could not be identified with a magnifying power of less than
eight hundred diameters. These are the smallest, simplest, and
probably lowest forms of life known. That multitudes do now spring
from pre-existing forms is absolutely certain, for the process can be
seen. Whether some spring direct from the non-living is the
question. Those that are supposed to be formed anew are very like
those that have had a progenitor, and from those supposed to have
been produced anew, forms exactly like those derived from un-
doubtedly pre-existing forms result. It cannot be pretended that
new forms of existence are produced anew. No matter how the
conditions are varied, the living forms supposed to result resemble
known living forms, and give rise to forms of the same kind.

But, as I have before remarked, the question of the origin of
bacteria can be only determined by experiment. All irrelevant
considerations in favour of abiogenesis ought now to be left in
abeyance. The assumed de novo origin is contrary to what goes
on throughout the whole kingdom of nature, and the only exception
which there is the remotest possibility of establishing is the spon-
taneous origin of some of these lower forms of life. While, there-
fore, it is allowable to permit ourselves to be influenced by general
evidence against a new and exceptional doctrine, which a few
observers seem very anxious to establish, we may fairly insist that
only evidence of the most convincing and demonstrative kind should
be accepted in its support. As regards the validity and reliability
of the most recent experiments for and against the doctrine, I offer

86

On the Origin of Life. By Lionel S. Beale.

no opinion. Time must be allowed for others to repeat the experi-
ments ; and, for my own part, I could express no opinion unless I
had been present and had carefully watched each experiment in
every stage. As far as I can judge, the reports of recent results
are not more convincing than were those that were adduced years
ago, many of which have been discarded and proved to have been
unreliable from want of care, or from defects in the method of pro-
cedure.

If the formation of a bacterium germ, direct from non-living
matter, be possible, three very remarkable series of changes, as it
seems to me, will have to be brought about. Whether any means
will ever be discovered of effecting these changes is surely most
doubtful.

First, the atoms of the non-living substances must be separated
from their combinations.

Secondly, the atoms will have to be rearranged to constitute
groups of which the organic matter is made up.

Thirdly, the groups of atoms must be made to live.

What facts known, I would ask, render it likely that air, rarefied
or condensed, or pressure of any degree or of any special kind, or
any degree of heat, or light, or any conceivable modification of
physical or chemical conditions, would at the same time account for
the pulling asunder and joining together of atoms, and for the con-
ference of new and peculiar powers of growth, of movement, of
division, and the formation of new substances ? In short, it is not
easy to conceive, in the imagination, the several steps which result
in the formation of a living bacterium even from organic matter.
But the first germ must have sprung direct from matter that never
had lived nor manifested phenomena in a way like those of life.
Let us try to imagine a living germ being produced out of non-
living matter. Atoms of many substances must be conceived as
separating from one another, and then recombining. Attractions
and affinities must, in the first place, be overcome, then the forces
that effected the change must cease to operate ; and these must,
somehow, be exerted again. By what means the separation of
atoms is effected cannot be suggested, neither can we conceive how
the atoms are caused to recombine in a definite way. The supposed
phenomena would be really more complicated than I have repre-
sented; for atoms are not related to one another — atom to atom,
but group to group. How the atoms are grouped, and how the
groups are related ; how the groups act and react upon one another,
and new groups are formed ; what makes the atoms combine and
begin a new course which may continue on and on for ever, — cannot
be conceived. Upon the whole, the production from non-living
matter of any living form, however simple, must be regarded as
most improbable.

( 87 )

PROGRESS OF MICROSCOPICAL SCIENCE.

Mr. Archer s Opinion of the American Ouramoeba. — In a paper read
before the Philadelphia Academy, on April 20, Professor Leidy
remarked that his description of the curious rhizopod he had named
Ouramoeba, in the Proceedings of May 12, 1874, having been noticed
by Mr. Archer, of Dublin, this gentleman had directed his attention to
notices of the same animal described in the ‘ Proceedings of the Dublin
Microscopical Club’ for Feb. 1866 and Oct. 1873. In these notices
Mr. Archer regards the animal only as an Amoeba villosa in another con-
dition from that ordinarily observed. Mr. Archer’s description clearly
refers to the same animal as that named Ouramoeba, in which he aptly
compares the bunch of tail-like appendages to “ a bundle of dipt-
candles,” and it is of some interest to know that the singular creature,
like so many other rhizopods, is common to Europe and America.

While Mr. Archer regards the “Amoeba with remarkable posterior
linear processes ” * as exhibiting another condition of existence of an
Amoeba from the one usually observed in the genus, he gives no
evidence that such is the fact. Until this is proved to be the case the
peculiar character of the animal justifies its separation as representing
a distinct genus with the name of Ouramoeba.

Since the latter was first noticed, many additional specimens have
been observed ; and though, as in the case of rhizopods generally, they
exhibit considerable variation, it appears that several species may be
distinguished.

The genus may be thus characterized :

Ouramceba. — Body, as in Amoeba, consisting of an ever-changing
fluctuating mass of jelly, composed of a granular entosarc, including a
contractile vesicle and a discoid nucleus, and defined by a clearer
ectosarc. Pseudopods usually digitiform, projecting anywhere, but
usually in a direction differentiated as forward, and composed of
extensions of the ectosarc closely accompanied by included extensions
of the entosarc. Posterior part of the body furnished with one or
more tufts of non-retractile, rigid, linear appendages, branching
radically from common points in the vicinity of the contractile
vesicle.

Ouramceba vorax. — Body active, usually ramifying forward from a
median stock extending from the posterior blunt extremity. Posterior
appendages numerous, originating in several tufts up to five or six,
from one-third to nearly the length of the body, linear, straight or
curved, uniformly cylindrical, or here and there contracted, com-
mencing in a pointed manner from a common root, and terminating
obtusely. Length of body, from 1 to ^ of a mm. ; length of ap-
pendages from one-third to nearly that of the body.

The creature consumes multitudes of diatoms, desmids, and fila-
mentous algae. Found in springs and ponds, near Darby Creek, Dela-
ware County, Pennsylvania.

Further observations have induced me to believe that the animal
* ‘Pruc. Dublin Micr. Club,’ Oct. 1873, p. 314.

88

PROGRESS OF MICROSCOPICAL SCIENCE.

named 0. lapsa is the same as the preceding. A variety has been
observed in several instances in which the animal had a single pair of
appendages springing from a common root.

Ouramoeba botulicauda. — This species is predicated on the form
alluded to in my previous communication as having a single tuft of
three moniliform rays. I have seen it a number of times since, and its
characters appear to be sufficiently constant to recognize it as a
distinct species. It is much smaller than the preceding. The body
measures about the -j1^ of a millimeter. The appendages are usually
in a tuft of three ; each appendage consisting of from one to three
sausage-like joints. Found with the preceding.

A curious Iihizopod : Biomyxa vagans. — Professor Leidy, who has
recently been directing his attention to this branch of zoological
research, remarked,* that in some water with aquatic plants, from
Absecom Pond, N. J., preserved in an aquarium during the winter, he
had detected a remarkable rhizopod, which he thought might best be
compared to the reticular pseudopods of a Gromia separated from
the body. The creature moved actively and assumed the most varied
forms. At one time it appears as a cylinder or a ball of jelly which
may spread itself into a disk of extreme thinness, from the edge of
which emanate a multitude of delicate pseudopods minutely ramifying,
and with the contiguous branches anastomosing, as in the extension
of the net of a Gromia. At other times the creature divides up into
branches from a trunk in the manner of a tree, but with the con-
tiguous branches anastomosing. At times also the animal assumes
the form of a cord, and the jelly accumulating along some portion of
it will then move along the apparent cord like a drop of water running
down a piece of twine. The branching pseudopods extending into a
net, the large angular meshes gradually contract by the widening of
the cords, so that the meshes become perfectly circular and appear
like vacuoles imbedded in the jelly. A circulation of jelly with
granules is observed along all the pseudopodal filaments exactly as in
Gromia. No trace of a nucleus or investing membrane in any posi-
tion could be detected, but the protoplasmic structure contained a
multitude of minute vacuoles. Most of the specimens contained no
food, and only one of the largest was observed to contain numerous
minute Closteria.

The largest specimen, consisting of a net emanating from three
divisions, occupied a semicircular space of | of a mm. by f- mm.
Another specimen with a central disk ^ mm. by ^ mm. with its net,
occupied a circular space | mm. in diameter. A small cord-like speci-
men was } mm. long with an expanded end irV mm. wide ; and another
irregular cord-like specimen was f of a mm. long with the widest
portion mm.

Amoeba porreda, of Schultze, from the Adriatic Sea, most resembles
the creature described. While it is nearly related with Gromia,
Lieberkuehnia, Vampyrella, Nuclearia, &c., it appears sufficiently
distinct in its characters to represent another genus, and with the
species may be appropriately named Biomyxa vagans.

* ‘ Proceedings of the Philadelphia Academy,’ April 20, 1875.

( 89 )

NOTES AND MEMORANDA.

An American View of the recently expressed opinion, as to
Objectives, of the Academy of Natural Sciences of Philadelphia. —

The following letter was addressed to the editor of the £ Cincinnati
Medical News’ (June, 1875) by Mr. J. E. Smith: — “In your last
(May) number of the News I notice the report ‘ of the committee
appointed to examine optically the -?hth and J-0-th objectives displayed ’
at the late exhibition of the Biological and Microscopical Section of
the Academy of Natural Sciences of Philadelphia.

“ According to this report it seems that of the six objectives
tested (?) a Tolies’ wet T^th of 140°, and a Wales’ ?h-th of 170°, were
the only glasses that displayed the hexagons (?) of P. angulatum by
central light.

“ A few months since, a correspondent of the London Micro-
scopical Journal proposed using P. angulatum with central light from
an ordinary candle, as a test for objectives of medium power. I at
once repeated liis experiment, using a £th and T(jth four-system
immersion glasses, made by II. B. Tolies, and was simply amused at
the result, to wit : the hexagons were instantly displayed with either
objective, using a common tallow candle for illumination — the angle
of obliquity 0 !

“ A friend of mine, a well-known ‘ expert,’ who had just purchased
a Tolies’ four-system T^th, read this article in the London Journal,
advised me that he too repeated the experiments, and with the same
results as I obtained with my ';th and Toth.

“ The ‘ committee appointed to examine optically, &c.,’ having
obtained the above-stated curious results, to wit : that the Tfrth and
the Tgth were the only glasses that would display the Angulatum
hexagons by central light, proceed to ‘ deduce one very important fact ’
(italics mine), viz. that the different appearances of lines, dots,
hexagons, &c., on P. angulatum are not only the varied results of
angle of aperture, of amplification, and of illumination, but that they
may be obtained with less and less obliquity of light as we increase the
power of the objective (italics mine again), thus making it evident that
high powers, with direct central light, show us clearly things which
we rather guessed at than saw (owing to the increased chance of
spherical and chromatic aberration and distortion from the employ-
ment of oblique light) with lower ones. (!)

“ The committee therefore conclude by recommending these higher
power lenses to those engaged in microscopic research, &c.

“ This was too much for Dr. Hunt to stand. TheJDoctor desired it
to be distinctly understood that he had nothing to do with the prepara-
tion of the report, and did not wish to be held responsible as a
member of the committee for the views advanced in it. Dr. Hunt
considered that it embodied the obsolete views of Carpenter and Beale
in regard to penetration, which term, he says, should be dropped from
the vocabulary of microscopists. ‘ He believed that penetration and
resolution can be and have been combined in the best objectives.’

so

NOTES AND MEMORANDA.

“ Dr. Hunt, having thus washed his hands of this most curious
report, makes a novel and startling proposition, ‘ the object being to test
men in regard to the’r technological skill.’ This is a brilliant idea
and to the point — r; ther ominous for the committee however ! ”

Angle of Aperture. — Mr. R. B. Tolies writes thus in the ‘ Cin-
cinnati Medical News ’ (June, 1875): — “ ‘ Mr. Wenham is unquestion-
ably right in stating that if an isosceles triangle be described, the base
of which is ten times the measured diameter of the front lens, and the
altitude ten times the measured distance of the focal point from the
same surface, the vertical angle of that triangle will correctly repre-
sent the maximum available aperture.’ *

“ Taken as stated here by Mr. Brooke, the rule proves contra-
dictory. Thus, Mr. Wenham gives the focus of the objective he
measured f as • 013 of an inch in air. Diameter of front surface
*043 of an inch. From these data he deduces that 118° is the
maximum angle possible in the case from plain measurement , &c. But
Mr. Brooke says, the rule gives ‘ the maximum available aperture.’
Apply this rule, then, to get the aperture in 1 balsam .’

“ Here are the data : Mr. Wenham, in the ‘ Monthly Microscopical
Journal ’ for May, 1875, p. 225, gives the focus in balsam as O’ 018 of
an inch. Thus we have the elements for the triangle in balsam.
Applying the rule we get a ‘ vertical angle ’ of 88°. But 82° in
‘ balsam ’ is equivalent to (infinitely near) 180° of pencil entering or
emerging at a plane surface. Consequently their rule with Mr.
Wenham’s own data , viz. diameter 0*043, median height 0*018,
proves the objective he declared J could not by any possibility have
more than 118° of aperture, has, by the same rule , all the air-angle,
i. e. angle for a dry mount, that any objective possibly can have.”

How to Prepare the Biatomacese. — Herr J. D. Moller proposes
to publish a work on this subject, and has offered the following as the
plan on which it will be issued : “ To the undersigned was repeatedly
expressed the wish : to publish his procedure to prepare Diatomacese.
He declares himself ready to do it for a corresponding indemnifica-
tion, and has the intention to try the following. If a number of sub-
scribers is obtained, he will publish a little work with illustrations,
which will have the title ‘ The Preparation of the Diatomaceae,’ and
which will contain : 1. The collecting ; 2. The cleaning and purify-
ing (a) of the living subjects, (b) of dead subjects in the mud, (c) of
fossils. 3. The separation of the different species. 4. The prepara-
tion and mounting, (a) in the ordinary manner (in quantity), (b) as
selected and arranged, (c) as ‘ Typen- and Probe-Platte,’ &c. Price
for the German edition, 30 marks ; English, 11. 12s. ; French, 40 francs.
Besides the undersigned, the following gentlemen will kindly receive
orders : G. F. Otto Muller, Koniggratzer Str. 21, Beilin W. ; Dr. E.
Hartnack and A. Prazmowsky, Rue Bonaparte, 1, Paris ; R. and J.
Beck, 31, Cornhill, London, E.C. ; Edmund Wheeler, 48, Tollington

* From the Annual Address of President Charles Brooke before the Royal
Microscopical Society, London, February, 1875.

t ‘ M. M. J.,’ March, 1874, p. 114.

% Ibid.

NOTES AND MEMORANDA.

91

Road, London, N. ; C. Baker, 244, High Holborn, London, W.C. ;
Janies W. Queen and Co., 924, Chestnut Street, Philadelphia. Orders
must be sent in, at latest, by September, 1875 ; in October the sub-
scribers will be informed whether or not the book will be published.
If the enterprise succeeds, each subscriber, by remitting the price to
the undersigned or to one of the above-named gentlemen, will receive
the book at the beginning of 1876.

“ Wedel in Holstein (Germany).” ££ J • L). Moller.

A Micro-Ophthalmoscope. — We learn from a contemporary that
“ in order to facilitate the microscopical examination of the eye in
cases of disease, M. Monoyer has contrived a modification of Siebel's
ophthalmoscope, so arranged with prisms, that three persons can make
simultaneous observations.”

Dr. Fleming’s Section-Cutter. — With reference to this instrument
(see p. 79) the following letter has been published in the ‘Lancet’
(July 3), from Mr. Lawson Tait: “A very serious objection to Dr.
Fleming’s machine will at once occur to anyone who has done much work
with the freezing method, in that the machine must require constant
attention until the tissues are frozen and the sections are cut. In a
University laboratory this is all very well ; but for workers who are at
the same time subject to the exigencies of practice the machine will
be a constant source of disappointment. In the last number of
‘ Humphry and Turner’s Journal ’ I describe a new section-cutter,
which obviates this objection. When the tissue has once been frozen,
it will keep so for at least twelve hours, and for a week if the machine
be placed in a Norwegian chamber. Having the section-cutter screwed
to the table has not been found by me to be a disadvantage : but, on
the contrary, a very great advantage, as it leaves both hands free — a
matter of the greatest importance in cuttiug foetal sections, Wrhere the
tissues are not continuous.”

The Salmon Ova that were sent to New Zealand. — These ova
were unsuccessful. That is to say, that the last shipment arrived in
New Zealand dead. But what is worse is — if the officers of the
Otago Association are to be believed — that microscopic examination
showed that many of the eggs had not undergone any fertilization.
It is strange that they should have arrived in a dead state, seeing
that a large quantity of the ice alongside them remained unmelted on
their arrival.

Microscopy at the American Association. — The American Asso-
ciation meets on the lltli of August, and it is endeavoured to get up a
large amount of interest in the microscope. The ‘American Naturalist ’
(July) gives the following notice: A full representation of those
interested in the microscope is especially desirable at the Detroit
meeting of the A.A.A.S., commencing on the 11th of next August, as
it is desired to take steps toward the organization of a Microscopical
Society, either as a separate society or club, or as a subsection of the
large Association. There is a very general desire for a society of
American microscopists, and it is believed that such a society can
VOL. XIV. H

92

NOTES AND MEMORANDA.

obtain general attendance from the whole country only at the time
and place of meeting of the A. A. A.S., to say nothing of the other
very great advantages of meeting in connection with that prominent
organization.

The Nutrition of the Protozoan. — Dr. Wallich, Hon. F.B.M.S.,
writes as follows to the ‘ Lancet’ (June 12) on this subject. He says:
“ Having for fifteen years stood alone in maintaining that the law of
nutrition which prevails in the case of the higher orders of the animal
kingdom, and constitutes the fundamental distinction between it and
the vegetable kingdom, fails in the case of the simplest and humblest
creatures, whose body substance presents no trace whatever of special
digestive apparatus, it is with no slight satisfaction that I am now able to
state that my views on this subject have very recently been confirmed
by evidence which seems to be incontrovei’tible. The fact is in itself
so important and so intimately connected with the biology of deep-sea
organisms, that it would be useless to attempt to indicate, within the
compass of a few lines, the nature of the evidence and reasoning
which influenced my conclusions. I must therefore content myself
for the present with observing that in my ‘ North Atlantic Sea-bed,’
published in 1862, pp. 130-132, as well as in various papers on the
Ehizopods and Protozoa generally, contributed since that period to
other scientific periodicals, I stated the reasons which appeared to me
to be sufficient to establish the belief that the lower rhizopods provide
for their nutrition and growth by eliminating from the medium in
which they live the inorganic elements that enter into the composition
of their protoplasm. What I contend for is, not that there exists in
nature a hard-and-fast line between the extremes of its two great
kingdoms, but a gradual transition and overlapping from both sides ;
and hence that the doctrine I have advanced is not the scientific
heresy which its opponents, under the influence of foregone and, as I
think, erroneous conclusions, have thought fit to consider it.”

Microscopy at the Bristol Meeting of the British Association. —
We are glad to see that Bristol is not going to be behindhand at the
meeting of the British Association, but is determined to illustrate her
local microscopy to the fullest. She has some men among her savants
who are by their knowledge and work qualified in the highest degree
to take a leading part in the discussions, and we trust they will not be
absent. At the soiree on August 26, the Bristol Microscopical Society,
assisted by the Naturalists’ Society and the Bath Microscopical
Society, has undertaken to give a systematic microscopic demonstra-
tion of the natural history of the neighbourhood ; a novel feature will
be the number of living objects which will be exhibited.

( 93 )

CORRESPONDENCE.

A Monstrous Form of Aulacodiscus.

To the Editor of the * Monthly Microscopical Journal .’

Baltimore, June 1G, 1875.

Dear Sir, — Allow me to offer you, for publication if you please, a
photo of a drawing of mine representing a disk of Aulacodiscus Ore-
rjonus with two centres, conveying the idea of two half disks, each
excentric, joined along a line of suture.

I am aware that this class of objects is not extremely rare, but
such a valve as the one in my possession must give rise to questions
of interest with regard to the manner of their production.

I have the honour to be, dear Sir,

Yours very truly,

Christopher Johnson.

[The photograph sent is not sufficiently distinct to make an en-
graving from. But it represents the two centres very well, and is
certainly a curious departure from the ordinary form. We learn,
however, from Mr. F. Kitton that monstrosities are not very rare in
this department of botany. — Ed. ‘ M. M. J.’]

Mr. Slack’s Paper on Angle of Aperture.

To the Editor of the ‘ Monthly Microscopical Journal .’

224, Regent Street, London, June 23, 1875.

Sir, — So long as the question of angular aperture was being dis-
cussed by rival opticians — the one anxious to have it believed that
everything worth knowing about the construction of objectives was
known to, or discovered by, himself ever so many years ago — while
the other, not content with having the splendid testimony of Dr.
Woodward and Professor Rcnel Keith in his favour, must needs venture
to speak in his own behalf with almost disastrous effect on his own
lucidity, — I say, so long as the question of angular aperture was
being discussed by rival opticians, we spectators might well stand by
and be amused by the prodigious display of personalities. But when
an Honorary Secretary of the Royal Microscopical Society comes for-
ward with a paper “ On Angle of Aperture in Relation to Surface
Markings and Accurate Vision,” we expect (at least some of us do) that
interesting information will be given, and that some of the latest de-
velopments in microscopy will be discussed with all the fulness of
knowledge to which his official position gives him access.

The interesting information in the Hon. Secretary’s paper seems
to be that he “ has a microscope in his library, opposite a north
window ; ” that the instrument “ is pointed like a telescope towards
the clear sky,” and, “ with Powell and Lealand’s immersion i-th, their
last but one, a perfect [?] definition is obtained of P. hippocampus.” (In

H 2

94

CORRESPONDENCE .

the next sentence he says it was “ drowned in light ” !) With sundry
other objectives, such as Zeiss’s C and D ( = ^th and ^th), he also
obtains admirable definition of this diatom. Further, that, taking a
delicate valve of P. angulatum that was not satisfactorily exhibited by
Zeiss’s C and D objectives with illumination from sub-stage mirror or
condenser, he has instantly increased the resolving power by the em-
ployment of the Reflex Illuminator. Later on he tells us he has had
an opportunity of trying experiments with Powell and Lealand’s new
-gdli, and he says the view he obtained of P. angulatum, with an ocular
giving a magnification of about 2000 linear, “ surpasses in beauty and
brilliancy anything seen before.” For all this information we are
thankful ; if it be rather vague and fragmentary, it comes from good
authority, and doubtless some of your readers will receive it with that
polite deference which such authority seems to require.

From the limited nature of the severity of the tests he mentions,
viz P. hippocampus (which Moller has thought to be too vulgar a
test to be admitted in his series on the Probe-Platte), and P. angula-
tum (which Hartnack exhibits with plane mirror axial illumination
with every ifh objective that leaves his hands), I am inclined to
think that Mr. Slack has reached that stage in microscopy when the
ardour of research palls, and we rest satisfied with mere amplification
of an easily obtained image, rather than search for an image that taxes
all our skill in manipulation and all the defining power of the finest
lenses at our command ; otherwise I should have thought he would
have selected some such admittedly difficult test as the Gnat’s body-
scale, in which there is structure that challenges the power of the finest
lenses to exhibit. It is clear, however, that Mr. Slack cared little for
settling knotty questions ; it was far easier for him to take the humbler
position of a reviewer of old — old tests, the definition of which is pretty
generally admitted : and this he has done. It is strange that he
learned only within the last year “ the amount of caution required ” to
regulate the quantity of light to be used with small and with large-
angled objectives. Even now he seems not to have mastered that
subject, for he speaks of a certain “ J-th with less aperture ” showing
P. hippocampus “ with same eye-piece rather better ” than Powell and
Lealand’s -gth “because not so much drowned in light.” Surely, a very
important part of the process of manipulation in microscopy consists
in duly proportioning the light to the capabilities of the lens ? If an
image appears to be drowned in light, it shoidd be the duty of the
microscopist to rescue it from that unfortunate j>redicament. He
favoured Zeiss’s C lens on the same object by carefully screening off a
little superfluous light “ by holding a sheet of white paper, so as to
stop some rays from entering the field ; ” and he makes suggestions
about placing the microscope “ some way from the window, where there
is a little shade,” and about surrounding the eye-piece “ with a screen
of black cotton velvet, to keep all glare from the eye,” with an air of
naive earnestness that is quite interesting.

I, too, have had an opportunity of examining some of Zeiss’s ob-
jectives— about twenty of them — and, while making the general admis-
sion of their excellence and evenness of quality, I must at the same

CORRESPONDENCE,

95

time say that, taking kis series from jtli up to A-th and testing them
against similar objectives by Powell and Lealand and by Hartnack
and Prazmowski, on the whole of those diatoms known as test-objects ,

• — on Podura, on Gnat's body-scale , on Dr. Carpenter’s “ thread-cells,” on
various specimens of tissue, on the double-star test, on Nobert’s Test-
plate, by the test of deep oculars, and with all the methods of illumi-
nation that are in vogue, — the English and French objectives carried
the palm. I do not here make allowance for any advantages there
may be in the ease of manipulation in consequence of Zeiss’s objec-
tives being of smaller angular aperture and having greater working
distance ; my judgment is upon the results obtained, which I under-
stand to be of the first importance. The mere item of one objective
being a little less difficult to manipulate than another does not appear
to me to weigh against superior clearness and definition in the imago
obtained.

And now, what, as to the latest developments in microscopy dis-
cussed by the Hon. Secretary ? When Professor Abbe is eulogized for
having “ minimized the angles of aperture,” it appears to me he is
receiving praise for a backward march. In high powers — all those
beyond }th — what we seek is magnification with clearness and defini-
tion. This is obtained if a lens be made that will support deep ocu-
lars. It is well known that the power of a lens for supporting deep
oculars is in proportion to the perfection with which the corrections
are made throughout a given angular aperture ; if these corrections
extend up to the maximum of possible aperture, such a lens bears the
deepest oculars before the optical image is broken up.

Professor Abbe is largely quoted, as though he were an impartial
authority criticising Zeiss’s work ; whereas, he is simply saying what
he can as an advocate for the work which Zeiss is producing under
his direction. When he says that “ corrections cannot be well made
with dry lenses exceeding 105° to 111° aperture, without a consider-
able reduction of working distance,” he is simply stating a fact ; but
this fact does not presume that Zeiss’s F lens ( = Txtk) with an aperture
of 105° can for a moment hold its own on the highest tests against
Dallmeyer’s or Powell and Lealand’s |ths with apertures beyond
140° : the working distance is different, and so is the quality of the
optical image. If Professor Abbe is satisfied with his result : so be it.
But when I and my most critical friends have made the comparison,
we first of all note that a deep ocular quickly finds the limit of light in
Zeiss’s lens, that it breaks up the crispness of image, that, in fact, the
lens has the qualities of similar low-angled lenses such as were pro-
duced in England many years ago.

Again, according to Mr. Slack, the most recent investigations and
experiments — those made by Professor Abbe — have led to the con-
clusion “ that even in immersion systems, for the normal requirements
of science, there would be no loss, but in many respects a gain, if they
were constructed with smaller angles of aperture.” I am unable to
determine what Professor Abbe means by the normal requirements of
science, but certainly one of the requirements is to render visible what
was before invisible in the object : how this is attained by diminishing

96

CORRESPONDENCE .

the angles of aperture is not explained and certainly not proved to
my mind by anything said or quoted by Mr. Slack.

In vol. xv. of ‘ Les Mondes ’ (p. 482 et seq.) Dr. Hartnack dis-
cusses the conditions under which the highest definition is obtainable,
and he lays great stress on the importance of the utmost limit of
angular aperture in high-power immersion objectives. Trying Zeiss’s
Nos. 1, 2 and 3 immersions ( = 4th, Tbth, and ?Vth) by the test of
deep oculars, I find Dr. Hartnack’s observations borne out ; the image
with these comparatively low-angled objectives breaks up with any
magnification beyond about 1000 diameters. On the other hand I
have found similar powers by Hartnack and by Powell and Lealand,
with their greater apertures, give far greater amplification, still retain-
ing fine definition.

Taking Mr. Slack’s summary of his results : — He says that
“ opticians have been encouraged to make excessive apertures substi-
tutes for good corrections if this means anything, I take it to mean
that opticians have been encouraged to make lenses that give bad
images ? In other phrase, the demand has been for lenses of inferior
rather than superior quality ? By way of absolute negation of this
dictum I point to his own criticism of Powell and Lealand’s new
-|4h, in which aperture has been carried to the highest limit con-
sistent with the accuracy of corrections for which these opticians are
renowned. Secondly, he says that “ naturalists and physiologists have
been too contented with feeble resolving powers.” If he had said that
many English opticians have been too contented with mediocre lenses,
that they slumbered over the introduction of improvements in high
powers until both on the Continent and in America lenses were pro-
duced that have fairly given microscopy a new start, then he would
have stated an important, though unpalatable, truth : as it is, the
naturalists and physiologists have been rapidly providing themselves
with high powers from Hartnack and others, so that the old objectives
that were formerly in use in the medical schools are now looked upon
as the stepping-stones to higher and more difficult investigations,
such as require the aid of more powerful objectives. Thirdly, he
speaks specially of the utility of the Reflex Illuminator. The Reflex
Illuminator is a very ingenious contrivance by which new and curious
effects of oblique illumination can be produced, both by reflexion and
refraction ; Dr. Woodward’s photograph of Poclura is the finest
example I have seen of one of its uses. Mr. Wenham has hitherto
seemed not to have observed that his Reflex Illuminator furnishes a
most elegant practical refutation of his own position with reference to
the “ aperture ” question. He has challenged “ anyone, to get, through
the object-glass with the immersion front .... any portion of the
.... rays ” that would “ be totally reflected ” with a pneumo-front
(vide ‘ M. M. J.,’ No. xxvii., p. 118). If he will try the experiment
on Moller’s Probe-Platte with his Reflex Illuminator and a high-
angled immersion lens, he will see a luminous field ; whereas, with
a pneumo-lens he obtains a darlc field. Whence comes the luminous
field in the immersion lens if not from its having the power to collect
rays which are totally reflected when the pneumo-lens is used ?

CORRESPONDENCE.

97

Lastly, I think Mr. Slack might well spare himself the trouble of
pleading ad misericordiam for those opticians whose specialty will be
to “ bring comparatively small-angled glasses to the highest degree of
perfection in resolving as well as penetrating power.” He may be
well assured these opticians do not attach an exaggerated value to the
“ honour ” of which he speaks as being within the power of the Royal
Microscopical Society to award to them ; what they ask for is a ready
sale for their wares ; what they deprecate is, that one who occupies the
position of Hon. Secretary of the Royal Microscopical Society should
give such an extraordinary meed of praise to the productions of a
foreign optician whose work cannot be said fairly to rival the highest
class of work produced by the best English opticians.

I am, Sir, your obedient servant,

John Mayall, jun.

Chromatic and Spherical Aberration.

To the Editor of the ‘ Monthly Microscopical Journal.’’

Bedford Square, July , 1875.

Sir, — The great interest and importance to microscopists of the
question discussed by Mr. Slack, “ On Angle of Aperture,” &c., in the
June number of the Microscopical Journal, is my excuse for asking you
to permit me to occupy a small portion of your valuable space on the
subject. On reference to the paper it will be found that it contains
statements which not only involve the use of the microscope, but also
certain intricate problems on the construction of the achromatic
instrument, which will appear to other of your readers, as they do to
myself, quite at variance with standard authorities on optical or rather
physical science. Eor instance, at p. 233, the following irreconcilable
statements are made, which for the purpose of discussing I place in
juxtaposition :

“No one could deny that up to a
certain date the best dot-displaying
glasses had considerable chromatic
errors, and that other glasses with
better chromatic corrections did not
show difficult dots so well.”

“Had it been considered that all
chromatic aberration involves spherical
aberration, the belief in any theoretical
necessity for leaving considerable chro-
matic error in order to ensure sharp
definition would scarcely have become
so prevalent.”

The first it will be seen involves a matter of fact, one which needs
no such qualification as “ that up to a certain date ” it obtained, since
it is perfectly true at this moment. In the next paragraph, however,
Mr. Slack says, “all chromatic aberration involves spherical aberration.”
Now this is simply a matter of theory, and for which I can find no
evidence or authority in any work on optics with which I am ac-
quainted. In Parkinson’s ‘Optics’ (p. 167) he will find it stated
that “ the conditions of achromatism depend only on the focal lengths
of the compound lenses, not at all on their forms, or the order in which
they are placed. By a suitable arrangement of these latter qualities
(i. e. forms and order), the conditions requisite for the destruction of
spherical aberration can be secured, and a compound object-glass

98

CORRESPONDENCE.

constructed which shall be at the same time both aplanatic and
achromatic.” An object-glass may therefore be achromatic and not
aplanatic ; so that all chromatic aberration does not involve spherical
aberration, and it necessarily follows that Mr. Slack’s theory is not
coherent, or consistent with actual observation and mathematical for-
mula. This he will the more readily admit from the fact that in
the objective which commands his admiration — the Powell and Lea-
land’s new |th — the point of best adjustment for achromatism is not
coincident with that of the best adjustment for aplanatism. I may say,
I have been unsuccessful in my endeavours to discover an optician who
believes “ in any theoretical necessity for leaving considerable chro-
matic error in order to ensure sharp definition.” I have, however,
heard opticians confess to the enormous practical difficulties in the
way of constructing a high-power objective combining aplanatism and
achromatism.

Mr. Slack is in error in supposing that “ large-angled glasses ”
were ever considered “nearly or quite useless for general purposes
of natural history and physiological research : ” physiologists were
among the first workers with the microscope to recognize the value
and importance of high-angled powers,* and in their investigations
constantly employ them to obtain a magnification of from one to ten
thousand diameters.

I remain, Sir, your most obedient servant,

Jabez Hogg.

Reply to Mr. Mayall and to Mr. Hogg.

To the Editor of the ‘ Monthly Microscopical Journal'

Ashdown Cottage, July 14, 1875.

Sir, — I am obliged by a sight of Mr. Mayall’s letter, as it enables
me to correct the misapprehension it might occasion without delay.
The first part is a wordy misrepresentation of my paper on angular
aperture. The question raised by me related to the smallest aper-
tures capable of showing lined objects. This would not be supposed
from the totally irrelevant comments of Mr. M. I showed that Zeiss’
C, angle 48°, resolved P. hippocampus , and that his D, angle 68°,
sufficed to exhibit Surirella gemma in dots.

I do not think Professor Abbe’s remarks will suffer from Mr. M.’s
erroneous statement that “ he is simply saying what he can as an
advocate for the work Zeiss is producing under his direction.” I feel
no doubt of their value, and believe our opticians will find them well
worth consideration. I can only attribute Zeiss’ higher powers
“ breaking dow n at about 1000 x ” to bad arrangement. His ^th,
Jg-th, and ^.th worked well in my hands, and in others’, with Eoss’s
L eye-piece, and even E.

Mr. M. is right in supposing me to mean that the demand of
English observers for extreme angles has encouraged opticians to

* [We certainly disagree with Mr. Hogg as to this point. — Eu. ‘M. M. J.’]

CORRESPONDENCE.

99

make lenses that do not give the best attainable images, but the term
“ bad images ” would be too strong. The lesson I have learnt from
Zeiss’ glasses is, that small and moderate-angled objectives can be
brought to a point of perfection far beyond what is generally sup-
posed, or what has been accomplished by any other optician whose
work I have seen. I have no doubt English opticians will excel with
small angles and great working distance when their customers ask
them to do it.

I remain, Sir, yours faithfully,

Henry J. Slack.

P.S. — Since writing the above I am further obliged by a sight of
Mr. Hogg’s letter. I regret that I am unable to understand some
parts of it, but it seems as if he had not borne in mind the effect of
the two kinds of aberration. In Ganot’s ‘ Physics,’ Atkinson’s trans-
lation, he will find that “ when the aperture is larger (than 10° or 12°),
the rays which traverse the lens near the edge are refracted to a point
nearer the lens than the rays which pass near the axis. The pheno-
menon thus produced is named spherical aberration by refraction.”
In chromatic aberration the violet rays are refracted to a point nearer
the lens than the red ones, and the effect is a distortion of the image.
The maximum of distortion will be where most rays are out of place,
from failure of either or both corrections.

The accuracy of my remark about considerable chromatic error is
proved by the fact that Messrs. Powell and Lealand’s last objectives,
and those next preceding them, are much more perfect in chromatic
correction than their earlier high powers, and likewise much sharper
in definition.

Mr. Hogg’s last sentence will astonish physiologists and many
others. With reference to the angles of the highest powers, Beck’s
.jg-tli was made with an angle (as per catalogue) of 140°, Powell and
Lealand’s T,Vth with 160°, 15° less than their old T^th, and their Jgth
has an angle of 150°, moderate in proportion to its focal length.
Mr. Wenham has informed us that the usual mode of estimating
angles of aperture considerably exaggerates them, and I find my
-djth of Beck to be about 128° when measured with Mr. Stephenson’s
scale, and the angle taken when the edges of two real objects are
distinctly seen.

High- angled versus Low- angled Objectives.*

To the Editor of the ‘ Monthly Microscopical Journal.’’

Memphis, Tenn., June 25, 1875.

Dear Sir, — Referring to your remarks j on a brief paragraph of
mine in a late number of 1 American Naturalist,’ I beg to offer the
following : not to enter into any controversy regarding it, but merely
as a fuller statement of the facts set forth in the previous note.

* This letter was hy a curious mistake addressed to Dr. Henry Slack.
t ‘ M. M. J.,’ p. 258.

100

CORRESPONDENCE.

I am sure I am correct iu stating that the generally received
opinion regarding glasses of very high angle of aperture is, that they
are “optical curiosities of no practical use ” (Dr. Pigott) ; “ their use
limited to particular classes of objects ” (Dr. Carpenter) ; in short,
that a glass of nearly 180° is per se good for nothing but to show
difficult test-objects under extreme obliquity of illumination, and
comparatively valueless for the study, under central light, of objects
coming properly within the sphere of the histologist and “ working
microscopist.” My friend, G. E. Smith, referred our Society to Mr.
Tolies’ new “ four-system ” objectives as a practical refutation of this
doctrine, and challenged us to the proof.

In my previous note I gave no names of makers of the various
objectives, lest I might appear desirous of “ puffing ” the work of some
favourite optician at the expense of others. Since this is considered
an error, I will now say that the glasses tried were by Tolies, Wales,
Zentmeyer, Smith and Beck, Powell and Lealand, Nachet, Scheik,
and Siebert. All were bought for first-class specimens of the various
makers’ skill. As our object was not to make a qualitative analysis of
the general merits of the various glasses, we confined ourselves to such
objects as properly come under the notice of the histologist, and used
only central illumination. After as full and fair examination as we
were able to make, we unanimously agreed that the new “four-system”
form of construction, as invented by Mr. Tolies, is an actual proof
that objectives of the highest attainable angle of aperture can be so
constructed as to meet the narrow-angled glasses on their own ground,
and not only equal but actually excel them. When I state that
certain glasses “ broke down ” under deep eye-piece, I meant that
the difference in favour of the wide-angled glass under these con-
ditions was so striking as to leave no room for comparison. In short,
this glass — Tolies’ new “ four-system ” J-0-th of 180° — so far from
being a mere “ costly toy ” of “ no practical use,” will, if properly
handled, give better results in the hands of the “ working micro-
scopist,” on any object suited to its magnifying power, than any of the
best glasses of moderate angle of aperture which I have yet examined.
In naming the angle 180°, I wish to he understood as simply giving it
as named by the maker.

I feel sure that the best and most thoroughly scientific “ working
microscopists ” in this country no longer discard an objective simply
because of high angle, as being therefore unfitted for the best work.
On the contrary, the narrow-angle is used for “ blocking out ” the
work, as it were ; the wide-angle for finishing it off. Whether their
work is “ valueless ” or not, let the pages of this valuable J ournal
testify.

In conclusion, I wish to state that I in no sense submit this note
as an official expression of the views of our committee on this subject ;
it is to be taken as a hasty expression of my own opinions alone.

Yours faithfully,

Albert F. Dod.

CORRESPONDENCE.

101

Mr. Taylor on Black Knot.

To the Editor of the 1 Monthly Microscopical Journal.’

Washington, U.S.A.. July 1, 1875.

Dear Sir, — Your Journal for May 1 has just come to hand. I
have read with pleasure the remarks of Charles B. Plowright, on
pp. 209 and 210, relating to my articles on Black Knot and Erysiphe
Tuckeri. He says of the latter : “ Of it in the ascigerous condition
we have seen no specimens, and therefore offer no remarks, but would
only suggest that Ffickel, in his ‘ Symbohe Mycologicie ’ places it in
the genus Sphcerotlieca, as a variety of S. Castagnei.” As I am not a
mycologist, but simply an observer, I would be much pleased to have
the views of the Kev. M. J. Berkeley and Messrs. M. C. Cook and
C. B. Plowright, and others who have given the subject particular study,
and to this end will forward by this day’s mail * a foreign grape-leaf,
on which about one hundred specimens will be found in good condi-
tion. I have had it in my possession for several years, and plucked it
from the grape vine of our foreign collection myself. I would like
the specimen now sent to be placed first in the hands of Mr. Berkeley,
as I understand he takes special interest in this subject, and he can
give such specimens as he desires to others. When I have time I
will review my experiments on Black Knot, and will forward specimens
of the asci containing the sporidia on microscopical slide for exami-
nation in London.

Faithfully yours,

Thomas Taylor.

A Proposed Prize for the best Objective.

To the Editor of the ‘ Monthly Microscopical Journal.’

Brighton, July 10, 1875.

Sir, — There seems to be now no longer any doubt that an object-
glass to suit all purposes cannot be made. Large angular aperture
is a necessity for diatom work and the like ; but on the other hand
moderate aperture is considered best for physiological and scientific
purposes. The names of Carpenter, Wenham, and Slack suffice to
settle that point.

The inducements to make glasses of the first kind are obvious,
and lie on the surface. They are such as are required by the largest
portion of the makers’ clientelle, the amateurs ; they can be easily
submitted to unanswerable tests, the resolution of difficult diatoms ;
and they can be judged of by everybody. Such glasses therefore
acquire a finer reputation.

Not so, however, with physiological glasses ; the facts in this case
are all the other way. Men really doing scientific work are compara-
tively few, and there is no standard by which the work required of

* Specimen Las not arrived. — Ed. ‘ M. M. J.’

102

CORRESPONDENCE.

their object-glasses can be either popularly, easily, or accurately
estimated.

Under these circumstances opticians can hardly be expected to
devote themselves with ardour to objectives of this sort. The finest
glass ever made would have but a limited sale, and probably would be
condemned by the public because it could not perform on a diatom so
well as other known glasses of even moderate excellence.

Still it is most desirable that makers should be encouraged to
throw their utmost skill into the manufacture of glasses best fitted
for scientific work.

With this view I would suggest that the Eoyal Microscopical
Society should appoint a committee to settle upon a standard for
physiological glasses. That the Society should offer a gold medal
every third year or oftener for such glasses, the same committee to
judge of those sent in for competition. The prize should be open
to all the world.

I have no doubt at all but that our great makers would add new
laurels to those they have so long and with such good right worn.
But whether that were so or not in the first instance, we may be sure
they would accept no defeat ; that they would be stirred up to new
efforts, and that science would thereby be the great gainer.

The glass bearing off the Society’s medal would be stamped in the
public mind as the best of its kind ; and while it would be a real and
immediate boon to science, it would by its reputation teach the in-
telligent amateur to look to a more instructive field than that presented
by mere diatoms, for the interest and pleasure he derives from his
microscope.

Dear Sir, yours truly,

E. Branwell, F.E.M.S.

The Bucephalus parasitic on the Fresh-water Mussel.

To the Editor of the ‘ Monthly Microscopical Journal.'

Stoke-upon-Trent, July 10, 1875.

Sir, — In the account of the ‘ Proceedings of the Eoyal Micro-
scopical Society ’ appended to your July number, a doubt is expressed
whether an instance has ever occurred of the genus Bucephalus being
found parasitical on the fresh-water mussel. Forty years back the
writer of this communication found them in the ovary of that animal
(Anodonta), and figured them in the ‘ Trans. Zool. Soc.,’ vol. ii.
pi. xviii. In the same year he found in the ovary of another
Anodonta, in vast numbers, the mother-cells of a Distomus, each cell
containing several individuals. This is figured in the same plate as
the Bucephalus. These Distomi, when excluded, are probably the
same which are found in the mantle or outer tunic of mussels
generally, and constitute the ordinary nuclei of pearls.

Your obedient servant,

Eobert Garner.

( 103 )

PROCEEDINGS OF SOCIETIES.

Queeett Microscopical Club.

Ordinary Meeting, May 28. — Dr. Matthews, F.R.M.S., President,
in the chair.

Mr. M. Hawkins Johnson read a paper" On the Organic Structure
of Flint and of Meerschaum.” He referred to numerous examinations
of the nodules found in sedimentary deposits, the structure of which,
he said, might easily be made visible by staining thin splinters with
acetate of rosaniline. The method adopted was to take a slice ^ inch
thick, to boil it in water to expel the air, then to boil it in a solution of
acetate of rosaniline, dry it, saturate it with balsam, harden the
balsam, and grind the sides, washing finally with oil of turpentine, but
not covering the specimens with glass. Nitrate of silver and acetate
of iron were stated to be sometimes even more successful than acetate
of rosaniline, the object being to render one portion of the substance
more opaque or more strongly coloured than the other. No less than
fifteen substances were considered to possess a structure of a decidedly
organic character, viz. : Meerschaum ; Kunkur of the Doab in India ;
Phosphatic nodules of the Crag of Suffolk ; Menilite from Menil
Montant, near Paris ; Septaria of London clay ; Race of the Woolwich
beds ; Chalk flints ; Iron pyrites of Chalk ; Green-coated nodules of
Chalk rock ; Phosphatic nodules of the Cambridge deposit ; Phosphatic
nodules from the Gault ; the Oolitic bodies ; Ironstone in Coal-measure
sandstones ; Chert of the Mountain Limestone ; Phosphatic nodules of
the Lower Silurian strata of North Wales. In addition to this he had
found that by the aid of acetate of rosaniline the pale green substance
in the green marble of Connemara could be shown to be a very
beautiful fossil sponge, as also the soluble silica rock from near
Farnham in Surrey.

The paper was followed by an animated discussion, in the course
of which Mr. Lowne strongly contested Mr. Johnson’s views.
Drawings and specimens of the stained substances were exhibited.

Adelaide Microscope Club, South Australia.*

The monthly meeting of the club was held on April 2, 1875.
Mr. Smeaton presided. A new instrument by Crouch was exhibited ;
the glass stage was much admired on account of its smooth gliding
movements. Dr. Whittell exhibited a new form of diatom he had
found in a collection from Edithburgh, S.A. He had been unable to
find anything like it in the drawings available in the colony, or on
Mdller’s typen platte, and promised to send it to England for identi-
fication.f The Chairman then gave a short address on the subject of

* Report supplied by Dr. Whittell, Adelaide.

f [This specimen, which was forwarded to us by Dr. Whittell, has been sent
to Mr. Kitton, who informs us that it somewhat resembles the specimen de-
scribed by the Rev. E. O’Meara (‘ Quart. Jour. Mic. Science,’ New Series, vol. xi ),
and which he calls Amphiprora ramosa. We believe, however, that Mr. Kitton
thinks differently from Mr. O’Meara, and we shall probably have an expression
of his decided views in an early number of this Journal. — Ed. ‘ M. M. J.’j

104

PROCEEDINGS OF SOCIETIES.

study for the evening, viz. Hydrozoa and Polyzoa. After giving a
lucid account of the general characters of each of these classes, illus-
trated hy some well- executed drawings, he proceeded to show a collec-
tion of about fifty varieties he had collected at different points of the
South Australian coast. Many of these he had been able to name,
but several differed so much from any illustrations in the books that he
was inclined to think they were peculiar to Australia. The collec-
tion was beautifully mounted, and about two hours were spent in
examining it under several microscopes brought hy members of the
club.

Memphis Microscopical Society.

April 15, 1875. — The Society met at the usual hour, with a full
attendance of members and visitors.

Donations were received ; several handsomely prepared slides of
various subjects from Mr. Frank Miller, of New York, and specimens
of a somewhat rare species of insect, from Mr. N. N. Mason, of Pro-
vidence, Rhode Island, for all of which a vote of thanks was passed.
A pamphlet was received from Mr. R. B. Tolies, of Boston, giving a
summing up of the angular aperture question, which of late has been
with so much bitterness discussed on both sides of the ocean. A letter
was read from Mr. Edwin Moulton, of Worcester, Massachusetts,
asking for information as to the best method of preparing sections of
coal, stating that the softening process described in the books proved
very unsatisfactory in his experience. On this point all the members
present agreed with his conclusion, and could offer no better way than
to grind down like any specimen of rock.

A communication was read from Professor E. W. Morley, of
Hudson, Ohio, giving in detail the measurements of another of
Moller’s probe plates. The results agree as closely as could he
expected with the probe plate previously measured, the average varia-
tion between the two measurements being only about 5 per cent.
The specimen of A. pellucicla on the last plate gives a measurement
of 95,000 lines to the inch. The care and patient skill of Professor
Morley render it sure that the figures given may he implicitly relied
on as correct.

The “ scientific evening ” of the Society having, from various
causes, been deferred, it was decided to bring the matter to a con-
clusion by appointing Drs. Willett and Morse and Messrs. Omhcrg
and Murray as a committee to carry out the plan and make all needed
arrangements, unless unforeseen obstacles prevent. A report is to he
presented hy them at the next regular meeting, the first Thursday in
May, when the Society can take final action.

A paper on “ Plant Crystals ” was read by Mr. A. F. Dod. All
microscopists are familiar with these objects, hut their place in the
vital economy of the plant seems yet undecided. Mr. Dod concludes
that they simply represent the waste of the plant’s life-processes ; in
brief, that the useless and effete matter which in the animal kingdom
passes off through the excreting organs, is in the vegetable kingdom
represented by these raphides, &c. After considerable discussion of
some of the points involved, the Society adjourned to first Thursday
in May.

The Monthly Microscopical Journal , Sept 1.1875. PI CXIII.

Flagella on Bacterium termo .

THE

MONTHLY MICROSCOPICAL JOURNAL.

SEPTEMBER 1, 1875.

I. — On the Existence of Flagella in Bacterium termo.

By YY. H. Dallinger, F.R.M.S., and J. J. Drysdale,
M.D., F.R.M.S.

( Taken as read before the Royal Microscopical Society.)

Plate CXIII.

In the huge Bacterium known as Spirillum volutans, Cohn
discovered, and figured in his ‘ Researches on the Bacteria,’ * the
presence of a pair of flagella, one at each end. This bacterium is
gigantic in proportions in relation to most other varieties, but
especially so to B. termo. An idea of their relative proportions is
given in Fig. 1, PL CXIII., where a represents B. termo and b
S. volutans. It is a spiral, and moves through the fluid by swift
revolution upon its axis.

In the summer of 1872 some very fine specimens of 8. volutans
came under our notice, and were carefully examined. We were
enabled fully to confirm Cohn’s discovery, and demonstrated re-
peatedly the presence of a pair of swiftly lashing flagella ; the
drawing at b, Fig. 1, was made from a specimen magnified 1300

EXPLANATION OF PLATE CXIII.

Fig. 1. — a. B. termo magnified with the same power as b, which is a specimen
of Spirillum volutans showing flagella at each end.

Fig. 2. — B. termo as seen with a power of about 600 diams.

Fig. 3. — The same, as seen with -g^th and second eye-piece (3700 diams.).

Fig. 4. — B. termo seen with flagellum at one end, the light coming in the
direction of the arrow.

Fig. 5. — The same object when it moved at right angles to its former position,
the light coming from the same direction, causing the sight of the flagellum to he
lost.

Fig. 6 represents one B. termo which was in a still condition, but one flagellum
moving. The light came in the direction of the arrow. When the end marked
2 6 was in focus flagellum was seen, but none at the end c. When the end marked
1 a was focussed carefully, the flagellum at that end was seen, and lost at the
end d.

Fig. 7. — The true form of B. termo.

Fig. 8. — The form as shown by the “supplementary stage” illumination
before flagella were found, showing the pointed termination of the body at a, b.

* ‘ Beitrage zur Biologie der Pflanzen.’ Zweites Heft, p. 127. Breslau.
VOL. XIV. I

106 Transactions of the Royal Microscopical Society.

diams. (diminished by \). The only difference between our speci-
mens and those drawn and described by Cohn was, that we rarely
saw them with so many turns in the spiral, and the granules were
not so regular in arrangement, and were often very large. But
these trifling differences may be accounted for in many ways.

It is extremely probable, as Cohn suggests, that Ehrenberg’s
Ophidomonas janensis is identical with Spirillum volutans ; and if
so Cohn only demonstrated what Ehrenberg inferred, from the
presence of vortical action in front of the creature, viz. that there
was a flagellum. But Cohn saw, and we confirm the fact, that
there were two flagella in this form — one at each end.

Having closed for the present our Monad researches, we have
been stimulated by the hope that the experience gained by these
might enable us to prosecute similar investigations into the true
life history of Bacteria. We have commenced the work this
summer, and guided by the analogy of S. volutans we have been
led to make several continuous efforts to find whether or not there
existed a flagellum or flagella in B. termo. The task of course
under the best circumstances must be a difficult one, from the
extreme minuteness of the object. We tried each of Powell and
Lealand’s powers successively, from the TVth to the -511th, but with
no definite result. Repeatedly we both saw vortical action at both
the distal and proximal end of the termo ; but could not absolutely
see the organ causing it. But in the process of our investigations
we made very close and careful observations on the fission of this
form : we do not purpose now to describe the process, but merely to
point out a phenomenon that further confirmed our suspicion of the
presence of an invisible filament. In separating into two, the jointed
rod of sarcode which is in process of division shakes to and fro at the
constriction, as if the constricted part were a hinge ; and at length
a clear separation takes place to quite the length of the original
termo (sometimes longer), and there is no visible connection between
them ; nevertheless they act as one creature, so that if one moves
in any direction the other goes with it just as the two parts did
before separation ; showing that although we cannot see the con-
nection there must be one ; and the presumption was that it was a
fine filament, such as we detected in the fission of some monads.*
We could make no further progress in the question apparently ;
but our attention was called to the new |th objective prepared by
Messrs. Powell and Lealand, with which we were soon supplied.
We used it at first with the “ supplementary stage ” for very oblique
illumination, supplied by the same makers ; and this has the advan-
tage of throwing the light in only from one direction. We were soon
convinced of the exquisite performance of the glass when used as an
immersion. Amphipleura peilucida was not merely seen to be

* ‘ M. M. J.,’ vol. x. p. 55 ; and vol. xi. p. 8.

Bacterium ter mo. By W. E. Ballinger and J. J. Drysdale. 107

striated clearly and sharply, but the striae were resolved into beads
with the third and fourth eye-pieces. In like manner the fine
striae in Surirella gemma were instantly shown to be beaded with
perfect and brilliant definition with the second eye-piece. Navicula
rhomboides, and an extremely delicate specimen of Pleurosigma
attenuatum which had resisted everything below a TVth immersion,
showed beaded striae perfectly. We were therefore encouraged to
try again to discover flagella in the termo. Some of our specimens,
nourished in Cohn’s nutritive fluid, were placed in a drop of distilled
water, and put upon the supplementary stage on an ordinary slide
covered with the thinnest cover. The utmost delicacy and tact in
manipulation of the light is the great desideratum; but with
this, enough may be secured to work with the fourth eye-piece.
The light may be made to enter the objective at almost every angle,
but it is always projected in a direction at right angles to the
stage ; and the first thing we observed when the objects were
sufficiently slow in their movements, and at right angles to the
light, was that the ends of the termo, which we (and all other
observers as far as we know) had taken for round proved them-
selves to be conical, terminating in a sharp point. The usual
appearance of B. termo, as seen with a magnification of about 600
diams., is seen in Fig. 2 ; whilst the same seen with a magnifying
power of 3700 diams. (sVth and second eye-piece) is seen in Fig. 3,
where a globular granule is seen in the end of each half. But with
the method above referred to, the best conditions being secured, the
two ends of the bacterium were distinctly pointed, as seen at a b,
Fig. 8, and after nearly five hours of incessant endeavour a flagel-
lum was distinctly seen at one end of each of two termo which were
moving slowly across the field. The discovery was not sudden and
transient, but lasted for at least twenty minutes ; the exquisitely
delicate flagellum was lashing rapidly the whole time, and one of
its frequent conditions is shown in Fig. 4, the arrow indicating the
direction of the light : but if the termo turned round at right
angles, as in Fig. 5, all trace of the flagellum was gone ; showing
that its discovery depended entirely, all things being equal, upon
its position in regard to the light.

But this observation was made only by one of us, the other not
being present ; and in pursuance of our plan we determined to see it
again, convincing ourselves separately, and then together. After
many hours of labour this was accomplished ; and Fig. 6 shows one
of two instances which we both saw together at the same time and in
the same instrument. It was lying still, obliquely across the field ;
the light coming in the direction of the arrow. Both ends were
not perfectly in focus at the same time, but in focussing the end
marked 2 b (Fig. 6) the flagellum was distinctly seen, and was seen
also to coil and lash ; but no flagellum was then seen at the end c of

i 2

108

Transactions of the Royal Microscopical Society.

the same object ; but by bringing it into delicate focus it presented the
aspect seen at 1 a (Fig. 6), which really represents the same object
at the same time only with the other end in focus, while the end
marked d corresponding to 2 b of Fig. 6 was in its turn slightly
out of foous and the flagellum lost to view. This observation, made
together, was as satisfactory as could be desired ; and it was 'thus
demonstrated that there was a flagellum at loth ends of the ordinary
B. termo.

It will of course be understood that it is by no means an easy
matter to secure the demonstration ; and whenever we repeat it, it
must always he with nearly the same amount of trouble and
patience, although we can now with the ordinary condenser detect
the vortical action both in front and (occasionally) behind the termo
as we never did before. But the demonstration of the ultimate
structure of a fixed object — as for instance Ampliipleura pellu-
cida — must be looked upon as a matter of great ease in comparison ;
and that for many reasons, the foremost being the motion and
minuteness of the object, the swift play of the flagella, their simi-
larity in optical properties to the fluid in which the bacteria live,
the difficulty of retaining them in focus, and of getting them in
such a position in relation to the light as to make demonstration
possible. Of course all this would be removed if dead bacteria
would answer, but they very rarely (indeed only once) have done
so with us. The flagellum needs to be in slow motion to properly
show itself ; for even with the more delicate and minute monads it
is a difficult thing to show the flagella in dead forms, since in the
majority of cases they appear to be attracted round the body of the
creature.

( 109 )

II. — A New Mode of Illuminating for Sigh Powers.

By Dr. Whittell.

I have lately been testing some bigh-power objectives, and have
discovered by accident a mode of illuminating which I have never
seen described, and which appears to be worth further trial.

I was working in a room lighted by a window to my left, which
is protected by a balcony so as to admit the sun’s rays during the
winter months only. The microscope was Beck’s larger model,
with rectangular prism and achromatic condenser, the central rays
being stopped. The object-glass was Powell and Lealand’s xVfh,
with immersion front. The test-object was the Surirella gemma,
and I had just succeeded in getting a fair view of the so-called
longitudinal markings, when the sun peeped from behind a cloud
and shone brightly on the microscope. The object became iridescent
and the outline rather indistinct, but I could still distinguish the
markings. I turned the prism towards another part of the sky,
but found that this did not affect the appearance. I could scarcely
imagine that the sun’s rays from above could affect the view of an
object seen under a glass working so close to the cover as a TVth,
but by way of experiment I shut off all light from below. I was
surprised to see the object, although not very brightly illumined,
showing all the markings as before. I now took the small con-
denser for opaque objects which fits into the stand, and condensed
the sun’s rays upon the upper surface of the cover. The field
became bright, and the object and its markings beautifully distinct.
The object was not white upon a dark field, as in what is called
dark-ground illumination, but had the same appearance as when
lighted by oblique light from below. The markings, however, were
more distinct. I substituted the dry front for the immersion one,
and found the result equally good.

I have since tried the same experiment with one of Zeiss’ ^th
immersion lenses, with splendid results. With this lens I found
that after obtaining a fine view of the longitudinal markings, I
could, by slightly altering the focus, cause them to disappear, and a
series of dots running transversely took their place.

I have also tried the experiment with one of Beck’s |-inch
objectives, and with No. 2 eye-piece I had a good view of the
longitudinal lines.

If any microscopist be desirous of testing the observation, I
must caution him not to be satisfied with a mere dark-ground
illumination, but to gently toy with the condenser until he obtain
a field having all the appearance of being illuminated from below.
In my last experiment I found the condensing lens close to the

110 The Resting Spores of the Potato Fungus. By W. G. Smith.

objective, and nearly parallel with the stage, the microscope being
in an upright position.

My present impression, which is open to correction, is that the
winter rays of the sun strike obliquely on the upper surface of the
slide, and some of these being reflected, pass through the object at
an oblique angle, and cause the same appearance as if the object
were illumined by light transmitted from the mirror.

Adelaide, South Australia.

III. — The Resting Spores of the Potato Fungus.

By Wobthington G. Smith, F.L.S.

Plates CX1V., CXV., and CXYI.

The Potato disease in this country is rarely seen before the month
of July, but this year I received some infected leaves for examina-
tion from the Editors of the ‘ Journal of Horticulture ’ at the
beginning of June, and my reply to the correspondent was printed
on June 10. The leaves were badly diseased, and I detected the
Peronospora in very small quantities here and there, emerging
from the breathing pores. This was a week or ten days before Mr.
Berkeley brought the matter before the Scientific Committee of the
Royal Horticultural Society ;* and when I heard Mr. Berkeley’s
remarks about the Protomyces, I immediately accused myself of
great carelessness in possibly overlooking it ; but I was equally
certain of the presence of the Peronospora in the specimens I
examined.

On receiving authentic specimens of diseased plants from Mr.
Barron of Chiswick, the brown spots on the Potato leaves at once
reminded me of the figures of some species of Protomyces, and the
dimensions agreed tolerably well with some described plants of that
genus ; but the spots, when seen under a high power, appeared very
unlike any fungus, and they were very sparingly mixed with other
bodies much smaller in diameter, and with a greater external
resemblance to true fungus spores. These latter spore-like bodies
were of two sizes — one transparent and of exactly the same size as
the cells of the leaf (and therefore very easily overlooked), and the
other darker, possibly reticulated, and smaller. A few mycelial
threads might be seen winding amongst the cellular tissue, and
these threads led me to the conclusion that the thickened and dis-
coloured spots on the leaves were caused by the corrosive action of
the mycelium, in the same way as Peach, Almond, Walnut, and
other leaves are thickened, blistered, and discoloured by the spawn

* See ante, vol. i., 1875, p. 795.

The Besting Spores of the Potato Fungus. By W. G. Smith. Ill

of the Ascomyces, as illustrated at the last meeting of the Eoyal
Horticultural Society.

My opinion, therefore, was soon formed that the “ new ” Potato
disease (as it has been called) was no other than the old enemy in
disguise, or, in other words, that it was the old Peronospora
infestans in an unusual and excited condition. That climatic con-
ditions had thrown the growth of this fungus forward and out of
season was probable; but the idea that the pest would not at length
attack all and every sort of Potato was to me most unreasonable,
though the more tender sorts might be the first to suffer.

Suspecting the two-sized small bodies before mentioned to be of
the nature of spores, and remembering my experiments during last
autumn with ketchup, in which I observed that the spores of the
common Mushroom might be boiled several times, and for lengthened
periods, without their collapsing or bursting, I thought I would
try to set free the presumed spores in the Potato leaves by macera-
ting the foliage, stems, and tubers in cold water. This maceration
was necessary because the tissue of the diseased leaves was so
opaque and corroded, and the cell- walls were so thickened, that it
was difficult to distinguish the threads and suspected spores from
the cellular tissue. I did not treat the leaves with boiling water,
because I wished to keep the threads and spores alive.

From day to day I kept the diseased leaves, stems, and tubers
wet between pieces of very wet calico, in plates under glass,
and I immediately noticed that the continued moisture greatly
excited the growth of the mycehal threads ; this to me was quite
unexpected, as I had merely wished to set the spore-like bodies free.
So rapid was now the growth of this mycelium that after a week
had elapsed some decayed parts of the lamina of the leaf were
traversed in every direction by the spawn. Thinking the close
observation of this mycelium in the now thoroughly rotten and
decomposed leaves might end in some addition to our knowledge of
Peronospora infestans, to which fungus I had no doubt from the
beginning that the threads belonged, I kept it under close observa-
tion, and in about ten days the mycelium produced a tolerably
abundant crop, especially in the diseased tubers of the two -sized
bodies I had previously seen and measured in the fresh leaves.
The reason why these objects, which undoubtedly occur in and
about the spots, are so extremely few in number in those positions
is, I imagine, because they require a different set of conditions for
their normal growth, and these conditions are found in abundant
and continued moisture.

The larger of these bodies I am disposed to consider the
“oogonium” of the Potato fungus, and the smaller bodies I look
upon as the “antheridia” of the same fungus, which are often
terminal in position. The filaments of the latter are commonly

112 The Resting Spores of the Potato Fungus. By W. G. Smith.

septate, and sometimes more or less moniliform or necklace-like.
Both oogonium and antheridium are very similar in nature and
size to those described as belonging to Peronospora alsinearum
and P. umbelliferarum, and this is another reason (beyond my
seeing undoubted P. infestans on Potato leaves at the beginning
of June) why I am disposed to look upon these bodies as the
oogonium and antheridium of the Potato fungus.

The larger bodies are at first transparent, thin, pale brown,
furnished with a thick dark outer wall, and filled with granules ; at
length a number (usually three) of vacuities or nuclei appear.
The smaller bodies are darker in colour, and the external coat is
apparently marked with a few reticulations, possibly owing to the
collapse of the outer wall. I have observed the two bodies in
contact in several instances. After fertilization has taken place,
the outer coat of the oospore enlarges, and soon gets accidentally
washed off in water. Both antheridium and oogonium are so
slightly articulated to the threads on which they are borne that
they are detached by the slightest touch, but with a little care it is
not really difficult to see both bodies in situ ; and my observations
lead me to think that conjugation frequently takes place after both
organs are quite free. The antheridia and oogonia are best seen
in the wettest and most thoroughly decomposed portions of the
tissue of the decomposing tuber, but they occur also in both the
stem and leaf. I consider Mr. Alexander Dean’s remark, as re-
ported in the ‘Gardeners’ Chronicle’ for June 19 last, p. 795, to
have a distinct bearing on this point, where he says, “ In all cases
where the seed tubers were cut they were quite rotten.”

Before I referred to De Bary’s measurements of similar organs
in other species of Peronospora I was disappointed with the results
of my observations, and felt disposed to refer the bodies and
threads in the Potato leaves to Saprolegnia, but a glance at the
figures now published and the similar figures copied from De Bary
to the same scale, will show that if the bodies observed by me are
Saprolegnia-like, the oogonia and antheridia figured by De Bary
show an exactly similar alliance. Still, as the Saprolegnieae are at
present defined, I am by no means inclined to describe the bodies
observed by me as really belonging to that tribe of plants.

The Saprolegnieae have the habit of moulds and the fructifica-
tion of Algae, and they live on organic matter, animal and vege-
table, in a state of putrefaction in water. One of the best known
of these plants is Botrytis Bassiana, the parasite which causes the
disease of silkworms. Now the genus Botrytis amongst fungi is
almost or quite the same with Peronospora, to which the Potato
disease belongs ; and I consider it a strong argument in favour of
my Saprolegnia-like bodies being the oogonia and antheridia of the

The Resting Spores of the Potato Fungus. By W. G. Smith. 113

Peronospora when such an authority as Mr. Berkeley * considers
one of the Saprolegniese (Achlya) “ may be an aquatic form of
Botrytis Bassiana ” — the silkworm disease.

The common fungus which attacks flies (so frequently seen on
our window-panes in autumn), Sporendonema muscie, Fr., is said
to he a terrestrial condition of Saprolegnia ferax, Kutz., which
latter only grows in water ; and if a fly infected with the fungus
be submerged the growth of the Saprolegnia is the result. It
would now seem to be somewhat the same with the Potato when
diseased, in the fact that when submerged a second form of fruit is
produced.

Between the two moulds, Botrytis and Peronospora, there is
little or no difference ; the characters of Corda, founded upon the
continuous or septate filaments, cannot be relied upon, and even
De Bary himself figures P. infestans with septate filaments, like
a true Botrytis. The intimate connection, however, between the
Saprolegnieae and some moulds cannot be denied, as the instances
above cited clearly show ; and I am therefore disposed to think that
the fungus which produces the Potato disease is aquatic in one
stage of its existence, and in that stage the resting spores are
formed.

Reference may here be made to the bodies found germinating
in the intercellular passages of spent Potatoes by Dr. Montagne
(Artotrogus), and referred by Mr. Berkeley to the Sepedoniei.
Ever since Mr. Berkeley first saw these bodies he has had an
unswerving faith in the probability of their being the secondary
form of fruit of Peronospora infestans , but unfortunately, as far as
I know, no one has ever found a specimen of Artotrogus since
Montagne.

The question may therefore be naturally asked, — How does
Artotrogus agree with the presumed resting spores here figured
and described? And has Mr. Berkeley been right or wrong in
clinging so tenaciously to his first idea ? Fortunately for the
investigation of the Potato disease (which can never be cured
till it is understood), Mr. Berkeley has given in the ‘ Journal
of the Ptoyal Horticultural Society’ the number of diameters his
figures are magnified to, and I have here engraved those figures
so as to correspond in scale with my own drawings, which latter
are sketched with a camera lucida. It will be seen that they
are the same with each other both in size and habit, with the
exception of the processes on the mature spore of Artotrogus —
which processes may possibly be mere mycelial threads, or due to
the collapsing of the inflated epispore. The reason these resting
spores have evaded previous search is that no one has thought of

* ‘ Hieroglyphic Dictionary,’ p. 6.

114 The Besting Spores of the Potato Fungus. By W. G. Smith.

finding them amongst leaves which had been macerated for a long
period in water. There is, however, nothing unreasonable in fruit
being perfected in water or very damp places, as it is common in
the Saprolegniese and amongst Algae in general. To sum up, there
are four reasons why the bodies here described belong to the old
Potato disease :

1. Because they are found associated with the Peronospora and
upon the Potato plant itself.

2. Because they agree in size and character with the known
resting spores of other species of Peronospora.

3. Because some other moulds are aquatic in one stage of their
existence.

4. Because they agree in size with Artotrogus.

Now that these drawings illustrative of the fungus which causes
the Potato murrain are reproduced in the following Plates,* it may
be as well to explain at once some of the terms used and the nature
and habit of the bodies hereafter referred to, for such readers as
may not be thoroughly acquainted with the life history of the de-
structive parasitic moulds to which the Potato fungus belongs.
For that purpose reference must be made to Fig. 1, which shows
(greatly enlarged) a transverse section through the leaf of a Potato
plant ; the two great bodies at A A represent two minute hairs on
the leaf, and at B B are seen the individual cells of which the leaf
is constructed. When these hairs and cells are compared with the
fine thread at C, which represents a branch of the Potato fungus
coming out of a breathing pore of the leaf, it will be seen how very
minute the fungus is in comparison with the dimensions of the leaf.
This fine thread is no other than a continuation of a thread of spawn
or mycelium which lives inside and at the expense of the assimilated
material of the leaf. When this thread emerges into the air, as
here shown, it speedily ramifies in different directions, and bears
fruit at the tips of the branches, as at D D ; these fruits are termed
simple-spores, or conidia, because from their smallness they are dust-
like. It is quite possible they may be an early state of the vesicles
which contain the zoospores as seen at E, F. However this may
be, they are commonly arrested in growth when still small, and
they germinate in an exactly similar manner with the zoospores
themselves, and may be considered somewhat analogous with seeds.
The Potato fungus has another method of reproducing itself in the
“ swarm-spores” shown at E, F. These are so called because, on the
application of moisture (as supplied by dew or rain, or when applied
artificially), the vesicles set free a swarm of from six to fifteen or
sixteen other bodies known as “ zoospores,” so named because they
are furnished with two lash-like tails, and are capable of moving
* Platus CXIV., OXV., and OX VI.

PLATE CXIV.

Fig. 1. — Transverse Section of a Fragment of Potato Leaf with Peronospora
infestans. Enlarged 250 diameters.

The Besting Spores of the Potato Fungus. By W. G. Smith. 117

rapidly about like animalcules. This rapid movement usually lasts
for about half an hour, and (like the dust-like conidia or “ simple-
spores” before mentioned) the swarm-spores generally enter the
breathing pores of the leaf, and there germinate. So potent, how-
ever, is the contents of these bodies when set free, that it is capable
of at once corroding, boring, and entering the epidermis of the leaf,
or even the stem or tuber itself. These zoospores are best seen when
within the vesicle F, where they arise from a differentiation of the
contents, but when once set free (Gr) they are, from the extreme
rapidity of their movements, very difficult to make out. In about
half an hour they cease to move, their lash-like tails (cilia) disap-
pear, and having burst at one end, a transparent tube is protruded,
which is a similar mycelium in every respect with that produced by
the simple-spore, and which grows, branches, and fruits in a pre-
cisely similar manner.

Now the great difficulty which has beset botanists for so many
years has been to account for the winter life of the Potato fungus.
Simple-spores and zoospores are lost in the production of the my-
celium or spawn, and this latter fine thread-like material cannot
of course survive the frosts and rains of winter, but must utterly
perish with the perished leaves and haulm.

A study of other species of Peronospora allied to the one which
produces the Potato disease, reveals the fact of a third mode of
reproduction. Simple-spores and zoospores are termed asexual,
because they are without sex, as distinguished from other bodies
called oospores, which are produced by the contact of two sexual
spore-like bodies, known as the antheridium, which is the male, and
analogous with the anther, H, and the oogonium, the female, and
analogous with the ovary of a flower, J. The oospores, not till now
seen for certain in the Potato disease, are the true resting spores.
Instead of being transparent and unenduring, as are the simple
and zoospores, these bodies are at length dense in substance,
black-brown in colour, and covered externally with reticulations
or warts. They are produced from the mycelium, by the contact
of the antheridium and oogonium in the substance of the decay-
ing plant ; they are washed into the earth, and there they rest
till a certain set of conditions makes them germinate in the year
following their production, just as a seed falls and rests in the
autumn and starts again into life during the following spring.

The terms here used will be better understood if the following
note is borne in mind : The oogonium is analogous with a pod, the
oosphere within answers to the ovule, and the oospore (or resting
spore) is the matured seed. The antheridium with its contents is
analogous with the anther and its pollen.

In various other fungi nearly allied to the Potato fungus these
resting spores have been seen, measured, and illustrated, but till

118 The Resting Spores of the Potato Fungus. By W. G. Smith.

now the resting spore of the Potato fungus has eluded all search.
The reason generally given and accepted for its absence is, that
the Potato is not the plant on which the fungus luxuriates to the
greatest extent, and that if we only knew the plant it most affects
(probably some South American species of Solanum) we should
then find plenty of resting spores easily enough, for it must not be
forgotten that the Potato fungus is by no means confined to the
Potato. It grows on various species of Solanum besides Solanum
tuberosum ; it is even not unfrequent on the woody Nightshade of
our hedges, and it grows upon the Tomato and other Solanaceous
plants, together with at least one plant which belongs to quite a
different natural order. On these latter, however, it makes less
headway than upon the Potato. As an instance in point the allied
pest of the garden Lettuce may be mentioned — Peronospora
gangliformis — first described by Mr. Berkeley. Here, if the
resting spores of the parasite are wanted, they must not be sought
for in the Lettuce itself, where they are only sparingly produced,
but in a plant belonging to the same natural order also commonly
afflicted with the same parasite, viz. the common Groundsel ; the
resting spores are said to be even more common in Sow-thistles
than Lettuces.

Therefore, although it is probable we shall have yet to look to
some other member of the natural order Solanaceae to find the
resting spores in any abundance, yet, as the resting spores of the
Lettuce mould can by searching be found in the Lettuce itself, so
the resting spores of the Potato fungus have without doubt been
found this year in the Potato plant.

How this came about is now pretty generally known. Mr. Murray
exhibited some specimens of Potato leaves badly diseased before the
Scientific Committee of the Royal Horticultural Society. In the
corroded spots of these leaves Mr. Berkeley’s sharp eye detected
dark-brown warted bodies (but no mycelium), which he referred to
the genus Protomyces. Assuming these bodies to be the true
resting spores, which they doubtlessly are, they were necessarily
free, as the coat of cellulose disengages them from the mycelial
threads. But some similarly spotted leaves had been previously
sent on to me, from the ‘ Journal of Horticulture,’ upon which I
detected the old Potato fungus, mycelial threads within the leaves,
and some circular transparent bodies of two sizes, new to me.

In attempting to wash the circular bodies out of the leaves and
stems, by maceration in water, I found the moisture greatly ac-
celerated the growth of the mycelium, and that the long-sought-for
oogonium and antheridium was at length the result. These bodies
were at first most sparingly produced, so that for many days, and
after most careful searching, I could only find one or two. After-
wards I found them more abundantly in different stages of maturity,

The Resting Spores of the Potato Fungus. By W. G. Smith. 119

especially in the very putrid stems and in the tubers when in the
last stage of decomposition. Mr. Berkeley afterwards found them
with abundant mycelium, after the meeting of the Royal Horticul-
tural Society on July 7, where he exhibited a drawing of one resting
spore still attached to its thread. Mr. Broome (from material sent
by me) has also detected and sketched, together with the immature
sphaerical bodies, one of these brown, coarsely-marked resting
spores, but it was so involved in the mycelial threads (so he writes
me) that he could not set it free. It is quite possible that the
condition of the Potato, as seen during the present season, is quite
exceptional, and that it may not occur again for a long series of
years. Mr. Broome has written me to say he has never seen any-
thing similar in diseased Potatoes.

In the accompanying illustration, which is an exact copy of the
first sketch taken, the oogonia and antheridia are seen in the sub-
stance of the lamina of the leaf, the two bodies being in contact at
H, J. In Fig. 5, PI. CXV., many more of the same bodies are shown ;
some in actual contact ; the two upper figures, K and L, show the
resting spores some time after fertilization, when a coat of cellulose
is the result. In K the spore is surrounded by this coat, whilst at
L the spore is accidentally washed out by maceration in water.
The semi-mature resting spores, as shown in these figures at M M,
are furnished with a dark coat or skin; this coat, when further
maturity is reached, clearly resolves itself into two layers, the
inner one being termed the endospore, and the outer, which in
Peronospora infestans is almost black in colour and warted, the
exospore. The latter resembles in outward aspect, instead of one
spore, a dense concreted mass of minute brown-black bodies. The an-
theridia are shown at N N. The perfected resting spores are slightly
egg-shaped, and on an average are one-thousandth of an inch in
diameter. The oosphere is fertilized by the contact of the anthe-
ridium ; when the two bodies accidentally touch the latter fixes a
small branch or tube, called a pollinodium or fecundating tube,
into the wall of the oogonium, and discharges part of its contents
into the protoplasm of the infant resting spore ; when these resting
spores are mature the mycelial threads soon vanish, and the spores
are free.

When I read my first notes before the Royal Horticultural
Society I had not been able to detect this fecundating tube, but
since then I have several times seen it. After the Potato plant
has been badly attacked and destroyed by the fungus, every part of
the plant and its parasite perishes, except the dark-brown warted
resting spores just described, and these find their way into the earth
and hibernate. When they awake to renewed life in the summer
they must germinate in the damp earth, and if no Potato plants
are near they perish, as the earth cannot support them ; in this

VOL. XIV. K

120 The Besting Spores of the Potato Fungus. By W. G. Smith.

they are not unlike the seeds of germinating Dodder, for if they
cannot find a proper host they die. But if Potato plants happen to
be near the corrosive mycelium, it at once penetrates and enters
the tuber or haulm. The tuber cannot produce simple or zoospores
if buried, but in the haulms the mycelium doubtless soon grows
and produces both these forms of fruit. These are at once carried
by the air into the breathing pores, and the whole history of the
fungus here described is re-enacted.

Since my observations on these bodies were published in the
‘Gardeners’ Chronicle’ for July 10, I have (by the courtesy of
the Bev. M. J. Berkeley) had an opportunity of carefully ex-
amining and measuring the original specimens of Dr. Montagne’s
Artotrogus, found long ago in the intercellular passages of spent
Potatoes, and from the first considered to be the secondary form of
fruit of the Peronospora by Mr. Berkeley. I have no hesitation
whatever in saying that the bodies lately seen and now figured by
me are positively the same with Dr. Montagne’s in every respect,
and when reflected and trac'ed with the aid of a camera lucida
no difference whatever can be detected. The bodies seen in Dr.
Montagne’s specimens are, without doubt, the fertilized and half-
mature resting spores, and therefore dense, uncollapsed, and exactly
the same in size, habit, and colour with mine when in the same
stage of growth. After the lapse of so many years the threads, as
might be expected, have more or less perished, but it is not difficult
to find traces of antheridia in the specimens.

For comparison, the original figure of Artotrogus (Fig. 3) is
here exactly reproduced to the same scale as my drawings, from
vol. i. of the ‘ Journal of the Boyal Horticultural Society,’ to show
the similar nature of the bodies illustrated. Since this was engraved
Mr. Berkeley has kindly forwarded Dr. Montagne’s original draw-
ings to me for examination, and I may as well say they contain
many more threads and oogonia than are shown in this cut, and
they are also more like my organisms now brought forward. As
for some of the bodies being shown as if within the threads by Dr.
Montagne, I consider this of little moment, as the oogonia are at
times almost or quite sessile, and consequently, when seen in some
positions, they put on an appearance of being within the mycelium,
whilst in reality they are upon or under it. As for the echinulate
body at 0, described as a “ mature spore,” it is not exactly like
Dr. Montagne’s original drawing, which is shown as furnished with
a thick wall, and there are no “mature” spores in his specimens.
After a most careful and searching examination of the latter I can
find no such bodies, but there are several spores on the two mica
slides which put on a spuriously echinulate appearance, which is
owing to the collapse of the coat of cellulose, as suggested by me as
a possibility when I read my first paper.

PLATE CXV.

O

Fig. 2. — Peronospora alsinearum.

Oogonia and Antheridia enlarged 400 diameters.

Fig. 3. — The Artotrogus of Montagne and Berkeley.
Enlarged 400 diameters.

Fig. 4.

Peronospora umbelliferarum.

Oogonia and Antheridia

enlarged 400 diameters.

Fig. 5. — Peronospora infestans.

Oogonia and Antheridia from badly diseased leaves of Potato, after a week’s maceration
in water; enlarged 400 diameters. Antheridium ^ = -0004 inch.
Oogonium = '001 inch. Coat of Cellulose = '00142 inch.

The Besting Spores of the Potato Fungus. By W. G. Smith. 123

It will be observed there is a little difference in size between
my oogonia (Fig. 5) and those copied from the ‘Journal of the
Royal Horticultural Society ; ’ this is because the figures in the latter
are somewhat incorrect. When the actual specimens are examined
and measured side by side they are in every way identical.

Mr. Berkeley has also most obligingly sent me a specimen of
another (new species ?) of Artotrogus, found in decayed Turnip by
Mr. Broome in 1849. Here the threads and semi-mature bodies
are in the same style as the oogonia and threads from the Potato,
and the mature spore is not truly echinulate ; it is globular, with a
slight tendency to an oval shape, and is covered with warts. It is
probably the resting spore of Peronospora parasitica, the pest of
the Cabbage.

In Figs. 4 and 2 are given copies of the oogonium and
antheridium of Peronospora umbelliferarum and P. alsinearum,
enlarged from De Bary to the same scale as the other figures,
to show the close similarity in size and habit.

Since this subject has been made public Mr. Carruthers has
kindly furnished me with a copy of Hr. Farlow’s paper on the
Potato Rot, extracted from the ‘ Bulletin of the Bussy Institution,’
part iv., a paper I had not previously seen. As some of Hr.
Farlow’s practical observations seem to have a direct bearing on
some of the points raised by me, I will conclude by extracting one
or two sentences : “ The disease is first recognized by brown spots
on the leaves ” (p. 320). “ If we examine any Potato plant affected
by the rot, even before any spots have appeared on the leaves, we
shall always find these threads in the leaves, stem, and, in fact,
nearly the whole plant ” (p. 322). “ The Peronospora is much

more easily affected by moisture than the Potato plant itself.”
“ Suppose the temperature to keep equally warm, and the atmo-
sphere to become very damp, then the absorbing power of the
mycelium is very much increased, while the assimilating power of
the leaf-cells is little altered. Thus it happens that a sudden
change from dry weather to moist will cause the mycelium to
increase so very much beyond the power of the Potato plant to
support it, that in the struggle for existence the latter blackens and
dies.” “ When the disease has arrived at a certain point, viz. just
about the time of the appearance of the spots on the leaves, these
mycelial threads make their way into the air ” (p. 323).

I give in conclusion an illustration of the perfectly mature resting
spore of Peronospora infestans, as seen imbedded in the substance
of the Potato leaf (PI. CXVI.). These resting spores, which carry
on the winter life of the fungus, are not restricted to the leaves, for
I find them sparingly in both haulm and tuber, although I have at
present seen the best specimens in the leaves. The engraving given

124 The Besting Spores of the Potato Fungus. By W. G. Smith.

herewith (Fig. 6) shows a transverse section through a black spot
of one of the leaves from Chiswick, and the resting spore is seen at
A nestling in amongst the cells of the leaf. An antheridium, 13,
and two oogonia (C, C), from which such resting spores arise, may
be seen in the cut, and the old common form of the fungus will be
noticed breaking through a hair on the upper surface of the leaf,
which is a very uncommon occurrence. The situation of the rest-
ing spores can generally be ascertained on the leaves by noticing
the slightly thickened and very dark spots, for the bodies are com-
monly in these spots. It is, however, an extremely difficult matter
either to get them out, or, indeed, to see them when imbedded, for,
when mature, they are black-brown in colour, and only a little
larger in size than the leaf-cells. These leaf-cells are also intense
brown-black in colour from contact with the hurtful mycelium, and
almost as hard as wood. The best way to see the resting spores
is to macerate the leaves for several days in water, and then set
them free by crushing the spot between two slips of glass. The
presence of the fungus in the leaf makes the cells very thick and
woody as well as black, so that in crushing the leaf-cells the
resting spore is not uncommonly crushed at the same time. With
care, however, they can be got at, when they will be seen, as at I),
covered with warts or coarse reticulations, and beautifully regular
and perfect in outline : when young they are of a pure warm
sienna colour, and when perfectly mature, brown-black and shining.
They are sphaerical or slightly egg-shaped, and measure on an
average about one-thousandth of an inch in diameter. I consider
it worthy of special note that these resting spores are almost
exactly the same in size, conformation and colour with Peronospora
arenarise, Berk., an allied species found parasitic on Arenaria
trinervis. In looking for these bodies care must be taken not to
confound them with corroded cells, granules of starch injured by
the disease, or foreign bodies.

At E is shown a semi-mature resting spore with pollinodium
attached, accidentally half washed out of its coating of cellulose by
maceration in water.

I may say as an addendum that to me there is a marked
analogy in size and habit on the one hand between the oogonia and
the vesicles which contain the zoospores, and on the other hand
between the simple-spores and the antheridia. 1 consider that the
oogonia and antheridia are merely the intercellular condition of the
vesicles which contain the zoospores and conidia, which latter are
the aerial state of the former.

The facts which point in the direction just indicated are
these : Sometimes there is no differentiation in the contents of the
vesicles, but the plasma is discharged in one mass and not in the
zoospore condition, the vesicle then resembles the oogonium. At

PLATE CXVI.

Fig. 6. — The Resting Spore of the Potato Fungus (A) imbedded amongst the Leaf-cells.

Enlarged 250 diameters.

Semi-mature Resting Spore (E) ; Mature ditto (D). Enlarged 400 diameters.

The Besting Spores of the Potato Fungus. By W. G. Smith. 127

other times the oogonium shows a distinct differentiation in its
contents, and matures from one to three resting spores, which to
me shows an approach to the condition of the vesicle which usually
gives birth to the zoospores. — See also the ‘ Gardeners’ Chronicle,’
July 17 and 24, from which the above Plates have been taken.

Since the above observations were printed, the following facts
have been observed by me, and recorded in the ‘Gardeners’
Chronicle’ for July 31.

1. Some plants sent to the Royal Horticultural Society by Mr.
Dean on July 21 were covered with the Peronospora far beyond
anything I had ever seen before. The haulm, the leaves (on both
sides alike), and the berries, were covered. Some of these plants,
after being placed on a garden bed, and covered with leaves (to
keep them moist), were the next day one white mass with the
Peronospora.

2. The Potato fungus (as commonly seen) bears a far larger
number of simple-spores than inflated vesicles containing the
zoospores or swarm-spores, but in Mr. Dean’s plants the fungus
produced zoospores almost exclusively, and in the greatest abun-
dance. As the zoospore is a higher development of the plant than
the simple-spore, this latter observation points to the unusually
robust health of the fungus this season.

3. On suspending the infected leaves over a glass of water for
from twelve to seventy-two hours, the swarm-spores fell in abun-
dance (either free or in the vesicle) on to the water, and there
germinated. No single drop of the water could be taken up for
examination without meeting with the germinating spores, the
threads radiating over the water in every direction, evidently in
quite a congenial element. It brought the following fact to light,
which is of importance — some of the vesicles which usually dis-
charge the zoospores discharged instead a thick mass of mycelium ;
and this cord, when it had proceeded a considerable distance over
the water, there had its contents differentiated in a necklace-like
manner, and gave birth to the zoospores far removed from the
original vesicles. The same thread also produced two true oogonia
on the water.

4. At the meeting of the Scientific Committee of the Royal
Horticultural Society, held on July 21, Mr. Renny showed a
species of Saprolegnia which, he said, might be mistaken for Pero-
nospora. But if reference is made to my original paper it will be
seen from the first that I have perceived the intimate connection
between the new condition of the Potato fungus and the Sapro-
legnieae. On my side I have the high authority of Thuret and
Berkeley for similar alternation in the diseases of silkworms, flies,
&c. I am quite prepared, therefore, to consider Mr, Penny’s plant,

128 The Besting Spores of the Potato Fungus. By W. G. Smith.

if not the same, some close ally with mine, even if it should turn
out to be a true Pythium, and its oogonia produce zoospores in
water, especially after what is known of the nature of Cystopus, the
close ally of Peronospora. Two strong points in favour of this
view are these : (1) The resting spores of Pythium are unknown,

but if I find Pythium inside Potato stems and leaves mixed up
with the Peronospora, and the same Pythium in the very centre of
the tuber of the Potato (as I have done), there maturing itself and
forming its resting spore, then the identity of the two may reason-
ably be assumed, and the resting spore of the Pythium, as well as
the Peronospora, is found. (2) The same cells in the Saprolegnieae
will alternately produce, under the same (or different) conditions,
zoospores or resting spores ; therefore, if zoospores are produced
in Mr. Kenny’s oogonia in water, it is reasonable to assume
that under different conditions resting spores would be formed by
similar cells. I have, from the first, believed the Saprolegnia con-
dition of the fungus to be widely diffused, and when in that state it
quite possibly grows on diverse plants and substances in watery
places, as was explained by me. The Saprolegnia is the caterpillar
condition (belonging to the water, like the larva of the dragon-fly),
the Peronospora somewhat analogous with the perfect butterfly,
and the resting spore with the dormant chrysahs.

5. I find by experiment, when badly diseased haulm, fruit, and
tuber are partly submerged for from one to four days, the Perono-
spora changes its character, and produces the Pythium or Sapro-
legnia-like growth on the submerged parts. On examination of
the plants this may be easily overlooked, as the Saprolegnia
commonly frees itself and floats on the surface of the water, and
must be carefully taken off (invisible as it is) with a camel-hair
pencil. If the oogonia now produce zoospores in the water, as in
Pythium, which is possible and even probable, it in no way invali-
dates my views, or makes the connection less probable between
Pythium and Peronospora.

6. The aerial spores of the Peronospora never become globular
in water, whilst the oogonia and antheridia are always so.

7. A superabundance of water excites the growth of the
mycelium, but it retards the proper production of the resting
spore, just as a superabundance of water in most plants makes
leaves and retards flowers.

8. In my calendar of the weather I find we had here only five
wet days from May 7 to June 10 (no wet between May 8 and 20),
and it was during this dry weather that the Potato fungus this
year lived inside, and at the entire expense of the plant, and there
perfected its resting spores. With the twenty-two wet days after
June 10 the Peronospora put on its usual shape, and came to the
surface.

The Microscopic Germ Theory of Disease. By E. C. Bastian. 129

9. I have got my most abundant materials from the tuber when
soft and almost transparent, like painter’s size ; in this state the
starch is utterly destroyed, and, what is most curious, there is no
offensive smell. The tuber frequently decomposes with a horrible
foetor, and turns whitish inside ; the starch is then present and
more or less injured, and very little can be seen of the fungus.

10. The season is too far advanced, and the fungus has already
caused too much destruction, to think of grappling with it this
season, but when it is remembered how the Vine, the Corn, and
Hollyhock parasites have been restrained, it certainly does not seem
impossible that means may be found to mitigate the damage done
every year by the Potato murrain.

IV. — The Microscopic Germ Theory of Disease ; being a Discus-
sion of the Relation of Bacteria and Allied Organisms to
Virulent Inflammations and Specific Contagious Fevers. By
H. Charlton Bastian, M.D., F.B.S., Professor of Patho-
logical Anatomy in University College.

(Continued from p. 79.)

Turning from these statements, therefore, as to the assumed
modes by which bacteria habitually gain an entry into the healthy
human body, I may say that many of the methods by which
Professor Kuhne, L)r. Sanderson, and others, have attempted to
ascertain whether the different tissues contain actual or ‘■potential”
germs are pointless in the face of the statements of heterogenists,
since their methods cannot enable them to say, when positive
results are obtained, that the “potential” germs from which, as
they assume, the organisms have been developed are other than
elementary particles of the previously healthy, though now altered,
tissues, or that they have not been produced from the fluids which
the tissues contain. These experimental observations are not only
almost valueless on this account, but they are altogether needlessly
complex. Why resort to heated knives, boiled thread, rapid move-
ments, frequent immersions in paraffin at 260° F., paper boxes,
warm chambers, &c., when precisely similar results might be
obtained by simply leaving the dead animal alone for three or more
days, and then subjecting the central tissues of either of the viscera
to microscopical examination? So far as the principle of the
method is concerned, or the kind of results which it may yield, it
makes no difference whether we keep an extracted portion of tissue
enveloped in paraffin in a warm chamber for hours or days, or
resort to the much simpler method of leaving the animal unopened
for several days before submitting its tissues to examination. In

130 The Microscopic Germ Theory of Disease. By H. G. Bastian.

either case where organisms are found this fact alone would give
ns no right to infer that they had developed from pre-existing
germs (in the natural history sense of that term) ; they may, on
the contrary, have arisen either by heterogenesis or by archebiosis.

The weight of probability in favour of either of these two
possibilities can only be judged of by resort to a different method
of procedure. Because in view of the observed absence of bacteria
from the tissues of such organs as kidney, liver, or brain, imme-
diately after death, the subsequent multitudinous presence of
organisms in these situations would, in the face of satisfactory
independent evidence, be more easily accounted for by heterogenesis
or archebiosis than by the hypothesis of pre-existing latent or
potential germs. By an appeal to evidence of this kind, moreover,
we are enabled to test the probability of the hypothesis previously
referred to as being supported by Dr. Beale and others— viz. that
which assumes the existence of invisible and mysteriously derived
germs of bacteria and fungi throughout the elements of the tissues —
an hypothesis somewhat wild in character, which has, I believe,
no other foundation than the frequently observed prevalence of
organisms in some of these situations.

With the view of settling these questions, therefore, we may care-
fully prepare an infusion from some animal tissue, be it muscle,
kidney, or liver ; we may place it in a flask whose neck is drawn
out and narrowed in the blow-pipe flame ; we may boil the fluid,
seal the vessel during ebullition, and, keeping it in a warm place,
may await the result as I have so often done. After a variable
time the previously heated fluid within the hermetically sealed
flask swarms more or less plentifully with bacteria and allied or-
ganisms, even though the fluids have been so much degraded in
quality by exposure to this high temperature, and have thereby,
in all probability, been rendered far less prone to engender inde-
pendent living units than the unheated fluids in the tissues would
be. We operate, however, under these disadvantageous conditions
in order to make thoroughly sure that, by the preliminary heating,
we have destroyed all pre-existing life within the flask ; and, not-
withstanding such adverse circumstances, we are able to obtain
evidence of the occurrence of archebiosis. The researches of
Kuhne and others have fully shown that the protoplasm entering
into the composition of the tissues of warm-blooded animals is
coagulated and killed at a temperature of about 111°F. ; whilst my
own investigations * also show that bacteria and allied organisms are
killed by exposure in the moist state to a temperature of 140° F.

Hence I contend that the wide distribution of bacteria through-
out the human body in connection with dying tissue-elements in
* ‘ Evolution and the Origin of Life,’ 1874, p. 101.

The Microscopic Germ Theory of Disease. By H. C. Bastian. 11

the most varied situations, and also in diseased fluids, is explicable
most easily by assigning for many of them an origin by hetero-
genesis and by archebiosis (though when so produced they multiply
rapidly in the ordinary fashion) ; and that my position — that
bacteria are pathological products — is one which may claim to have
been fairly established.

On this subject I would only add a word or two concerning the
point of view and reasoning employed by those who seem willing to
believe in almost any infringement of natural uniformity rather
than admit the occurrence of heterogenesis and archebiosis, or
either of them alone. The most remarkable recent utterances on
this subject are those of Dr. Sanderson, though it is only fair to say
that they are somewhat typical of the line of argument adopted by
many others.

Whilst admitting that bacteria in their “ ordinary state ” have
been proved to be killed at a temperature of 140 J F., and also by
immersion in absolute alcohol, Dr. Sanderson assumes that other
bacteria germs may exist in an extraordinary state, in which they
have the power of resisting the influence of this temperature, the
influence of absolute alcohol, and even the simultaneous action of
both these destructive agents. But if we ask on what amount of
evidence this assumption is founded, many may be astonished to find
that such an extraordinary belief has been adopted simply because
bacteria make their appearance in an organic infusion which has
been prepared by macerating an organic extract previously sub-
mitted to the influences above mentioned — just as bacteria make
their appearance within our closed flasks, whose contents have been
previously heated to the higher temperature of 212 F. Has it
ever occurred to Dr. Sanderson that another interpretation might
have saved him from the necessity of adopting this extraordinary
belief ?

Again, in his third lecture, the same investigator shows himself
for the time similarly oblivious of the point of view of those who
believe in archebiosis, whilst the argument made use of to support
his own position is of a very surprising nature. After remarking *
that “ of all perishable things, protoplasm is amongst the most
perishable,” he goes on to state that bacteria possess “ a wonderful
property of passing into a state of persistent inactivity or latent
vitality.” This is nothing more than an explicit expression of the
notion previously referred to, though I wish especially to call
attention to the additional “ evidence ” upon which the view is now
based. Dust, containing organic debris, in which, as Dr. Sanderson
confesses, he has no proof that anything living is contained, may be
added to a fluid at the time barren, though freely capable of sup-
porting life. One of the results of this addition is the appearance,
* ‘ British Medical Journal,’ March 27, p. 403.

132 The Microscopic Germ Theory of Disease. By H. C. Bastian.

after a short time, of bacteria. A physicist or chemist might con-
ceive it possible that, as a consequence of such admixture, a com-
pound not previously existing might have been more or less slowly
formed — as this, at all events, is one of the modes by which new
chemical compounds are engendered. But this point of view Dr.
Sanderson will not seriously entertain — indeed, his remarks seem
only explicable from the point of view of a foregone conclusion that
archebiosis is an impossible process, and therefore on no account to
be admitted as an interpretation of the facts. In reply to an
imaginary objection, alleging that he had no proof that the dust
contained anything living, he says with great naivete : “ True ; but
I have proof that it contains that which produces life, and express
this state of things — viz. the absence of manifestations of life on
the one hand, and on the other the fact that the stuff in question
possesses the power of impregnating something else which before
was barren — by saying that the dust possesses latent vitality.”
The legitimacy of the inference does not seem very apparent to me,
if it is to be taken in any other than a poetical sense ; yet this is
the only evidence adduced in favour of the assumed existence of an
extraordinary state in which bacteria may exist — a state in which
they are assumed to be capable of resisting influences which are
admitted to be destructive to all actually known forms of life. Of
course, on the same grounds, the physicist might argue that
“ friction possesses latent electricity,” or the chemist that “ oxygen
possesses latent acidity,” but it seems very questionable whether
such statements would be regarded as serviceable additions to
science. Neither can we consider that any further light is thrown
upon this notion of “ latent vitality ” by Dr. Sanderson’s concluding
observations upon the subject, in which he says : * “ The vital
activities of the organism are stored up for the future, the
individual being for this very end endowed with the power of
resisting external agencies, and thereby of enduring for an indefinite
period.” As to such teleological notions I have nothing to say ; I
prefer keeping to the region of fact and warranted inference.
These, however, are the arguments by which a belief in the occur-
rence of archebiosis and heterogenesis is for the time averted.

Before drawing my remarks on this section of the subject to a
close, I would point out that the views admitted by Dr. Beale, and
those who think with him, those admitted by Dr. Sanderson, Pro-
fessor Kiihne, and Dr. Tielgel, as well as those recognized by myself
and others, all coincide with one another on a certain common
ground. We are agreed as to the fact that bacteria are abundantly
present within the body, or that they may appear therein under
certain conditions independent of any immediate external contamina-
* ‘ British Medical Journal,’ April 3, p. 436.

The Microscopic Germ Theory of Disease. By II. C. Bastian. 133

tion — however much we may differ amongst ourselves as to the
interpretation of their presence, actual or possible. Yet this
common ground contains an admission which is decidedly inimical
to Mr. Lister’s theories. Following M. Pasteur, this distinguished
surgeon would have us believe that whilst bacteria are disease germs,
they do not naturally exist within the body. He has based his
antiseptic system of treatment on the assumption that air, or surfaces
which have been exposed to it, coming into contact with wounded
portions of the body, are the means by which his assumed animated
poisons are introduced into the system. But it is, I think, now
well known that the whole pyaemic process may be met with occa-
sionally, even where there is no abrasion of the surface of the body.
And, moreover, as regards the cause of the disease in persons with
open wounds, I may say that Pasteur never seriously attempted to
discriminate between the respective effects of the living and the
dead elements entering into the composition of atmospheric dust.
Effects which were often due to the action of mere organic debris,
he attributed to the influence of living germs,* and in this respect
M. Pasteur has been followed by Professor Lister.

But, as I take it, the essential practical fact which Professor
Lister wishes to enforce is that the putrefactive processes apt to
take place in wounds ought to he reduced to a minimum, because
it seems certain that during such processes poisons are liable to be
engendered whose absorption or local influence upon the system
may be attended by the most fatal results. Such a notion, which
is assuredly thoroughly well founded, may, however, he acted upon
by the adoption of the antiseptic system of treatment (or by free
exposure of wounds and frequent removal of secretion), quite inde-
pendently of the question whether mere organic debris may act as
ferments, and also quite independently of the further question
whether the poisons engendered in wounds are living entities or
complex chemical compounds not endowed with the attributes of
living matter.

Applicability of the germ theory to artificial tuberculosis, syphilis,

typhoid, typhus, relapsing fever, cholera, measles, scarlet fever ,

small-pox, and other contagious fevers.

I now pass to a consideration of the germ theory in its relation
to another class of diseases, although I do not wish to convey the
idea that there exists in nature a distinct boundary line, such as
my division of the subject might indicate. It must he clearly
understood that the local morbid processes or inflammations of a
virulent type — which may or may not gradually entail a more
general morbid condition — pass insensibly by means of such affec-
* ‘ Evolution and the Origin of Life,’ pp. 103-114.

134 The Microscopic Germ Theory of Disease. By H. C. Bastian.

tions as artificial tuberculosis and syphilis into that class of diseases
under which are included such affections as typhus, typhoid,
relapsing fever, cholera, measles, scarlet fever, small-pox, and other
contagious fevers. Affections like artificial tuberculosis and syphilis
might therefore have been placed with equal appropriateness in
either of the divisions I have adopted.

The treatment of the present part of my subject may be disposed
of in a more summary manner than the last, principally because
many of the facts and considerations which were advanced in refer-
ence to virulent inflammations and their sequelae, and the presence
of independent organisms in the altered fluids and tissues of the
body, are also applicable to the question of the relation of such
organisms to the more specific contagious fevers.

The case to be made out in favour of the germ theory as
applied to these latter fevers is also, in my opinion, much weaker
than it is in respect to the virulent inflammations and their sequelae,
since, although such contagious fevers have always been regarded
as general and essentially “ blood diseases,” in only one of those
occurring at all commonly in the human subject does it appear that
anything like an independent living organism is to be met with
in the blood. There is, therefore, here a primd facie inherent
weakness in the whole theory, which I think a thorough exami-
nation of the question will strongly tend to confirm rather than
dissipate.

The reasons relied upon in favour of the germ theory, as applied
to these diseases, are of a purely a priori or theoretical nature,
and such as I have already referred to. They are, in fact, based
upon the assumed nature of contagium, and upon its assumed mode
of increase within the body. How little conclusive such a priori
reasons are, and how the facts may be otherwise explained, I have
already endeavoured to show, and as the theory in its applicability
to these diseases rests upon absolutely no positive evidence that I
am aware of, I am compelled to leave a gap here, and pass on to a
brief enumeration of the facts and considerations which seem to tell
so strongly against the existence of any causal relationship between
organic germs and these specific contagious fevers :

1. The fact that, with two exceptions, no definite germs or
organisms are to be met with in the blood of patients suffering
from these diseases, during any stage of their progress.

2. The fact that the virus or contagium of some of these
diseases, whatever it may be, does not exhibit the properties of
living matter.

3. On the other hand, the virus of most of these contagious
diseases with which definite experiment has been made, is most
potent in the fresh state, whilst its power very distinctly diminishes
in intensity as organisms reveal their presence more abundantly

The Microscopic Germ Theory of Disease. By H. C. Bastian. 135

therein — facts which would seem to point to the conclusion, or at
least are quite consistent with the notion, that the contagious
poison may be a chemical compound which gradually becomes
destroyed or modified by the successive changes taking place in
association with processes of putrefaction.

4. There is the extreme improbability of the supposition that
this whole class of diseases should be caused by organisms known
only by their effects.

5. The fact of the sudden cessation, periodical visitations, and
many of the other phenomena of epidemics, however difficult they
may be to explain upon any hypothesis, seem to oppose almost
insuperable obstacles to the belief that living organisms are the
causes of such epidemics of specific contagious diseases.

It would seem little better than an ill-timed attempt at jesting
to postulate the existence of distinct germs for these several specific
fevers, and at the same time to endow such imaginary entities with
properties different from those of all known germs. To remain
always in the germ stage in media favourable for their multipli-
cation would, even if the imaginary germs were visible, be contra-
dictory to all previous experience ; but to suppose, in addition,
that such hypothetical invisible entities are capable of resisting the
influence of agencies which have been proved to be destructive of
all known living matter would seem to be going altogether beyond
the bounds of probability. And if we look at the question from
this point of view, we may regard it as a definitely established fact
that the virus of cholera, for instance, is not composed of living
germs or particles. Messrs. Lewis and Cunningham have shown*
that the virus is not appreciably impaired in activity when the
fluids containing it have been raised for a few minutes to a tempe-
rature of 212° F. ; and in reference to this subject they say, “ We
have seen no living object preserve its vitality after exposure in a
fluid to a temperature approaching to 212° F., nor have we been
able to satisfy ourselves that anyone else has done so.

In only one of the specific fevers commonly met with in the
human subject have organisms been found in the blood : this
exception is relapsing fever. There is, however, an affection occa-
sionally communicated from cattle (sang de rete, or splenic fever)
in which organisms are also met with in the same situation. But
the fact of the existence of actual visible organisms in these cases
seems altogether robbed of its significance after the occurrence of
archebiosis and heterogenesis in diseased fluid and tissues has been
demonstrated. The view, indeed, that the organisms found in
these affections owe their origin to certain changes prone at times

* ‘ Report, &c., into the Nature of the Agent or Agents producing Cholera,’
pp. 46 and 57, 1874.

YOL. XIY.

L

136 The Microscopic Germ Theory of Disease. By II. C. Bastian.

to occur in the fluids of the body is directly supported by some of
the most interesting results of Dr. Sanderson’s experiments con-
cerning pyaemia. He tells us that in some of the lower animals
artificial tuberculosis and pyaemia are often only different effects of
the same cause. That is, that some of the same inoculating ma-
terial may be introduced beneath the skin of two rabbits, and in
the one a slow and more chronic set of morbid changes is induced
(tuberculosis), whilst in the other more acute and rapidly fatal pro-
cesses are established (pyaemia) . In the former animal no organisms
are to be found in the blood, whilst the blood of the latter, according
to Dr. Sanderson, is swarming with them. Changes in the character
of the morbid process therefore may occasionally favour the presence
of organisms. Nay, further, we see the same kind of difference in
another way. Pyaemia and septicaemia as they occur in some of
the lower animals differ in one very notable respect from the
same diseases as they occur in man. Whilst in the lower animals
bacteria are to be found in the blood of the living animal, in man
they are always absent during life. With such facts as these before
us, and others previously referred to concerning the absence and
presence of organisms in blister-fluid from different individuals, it
need not excite much surprise if we find that organisms are to be
found in the blood of persons suffering from one or more of these
specific contagious fevers.

There are, however, three other diseases of this class in which
organisms, though absent from the blood, are to be met with in
those parts of the body which are severally the special seats of
morbid change. The three diseases are — vaccinia, ovine small-pox
(which seems to be altogether similar to the disease occurring in
man), and typhoid fever.

That the organisms of the vaccine vesicle have any significance
other than from being possible instances of heterogenesis or arche-
biosis, I find it difficult to believe. Even if the contagious property
of the fluid be resident in some of its particles, as the observations
of M. Chauveau and Dr. Sanderson seem to prove, still such
particles may exist and yet not be the independent organisms
existing in the same fluid. The fact that as the organisms increase
in the fluid with age the virus loses its intensity, and the fact that
it may remain potent even after prolonged periods of desiccation,
are both of them strikingly opposed to the notion that the living
organisms of the fluid are its active elements in a specific sense.
On the other hand, it does appear, from the experiments of the
late Dr. Henry, of Manchester, that vaccine virus loses its intensity
when subjected to a temperature of 140° F.

In ovine small-pox we have, as Dr. Klein’s very interesting
researches have shown,* a local appearance and active growth of
* ‘Proceedings of the Royal Society,’ No. 153, 1874.

The Microscopic Germ Theory of Disease. By II. C. Bastian. 137

organisms taking place in the skin in connection with its charac-
teristic pustules ; whilst in typhoid fever we have also an active
growth of rather different organisms in the substance of the ileum,
and more especially in the tissues constituting Peyer’s patches —
that is, in connection with the anatomical marks of this disease * But
just as a mere chemical irritant (ammonia) injected beneath the skin
of a rabbit produces, as Dr. Sanderson tells us, a local inflammation
in which the fluids effused swarm with bacteria, why may not the
morbid processes taking place within the skin in small-pox engen-
der irritants which may lead to the appearance of somewhat similar
products ? So that, in the face of the evidence already detailed
concerning the occurrence of heterogenesis, the presence of organ-
isms in connection with small-pox lesions may be readily accounted
for, without the necessity of attaching any very important role to
them. And as regards the presence of organisms in Peyer’s
patches and adjacent parts, in cases of typhoid fever, no greater
importance could be accorded to this association by any but enthu-
siastic germ theorists. For, even if the reasons above alluded to
were not very influential with them, there is another mode of
looking at the matter, from quite an orthodox point of view, which
would equally assign to the local development of organisms a very
subordinate role. Morbid tissues are generally admitted to form a
favourable nidus for fungoid growths, and the intestine is known
to contain the germs or spores of such bodies. The flourishing
growth of leptothrix and fungi in the diseased mucous membrane
may therefore be only another example of an already well-known
class of effects ; so that, looking at the question from all sides, it
seems to me, in the present state of our knowledge, to be extremely
improbable that these newly discovered organisms have any causal
relationship to typhoid fever.

It only remains for me now to make a few very brief concluding
observations concerning — (1) Pasteur’s recent important modifica-
tions of his germ theory of fermentation ; (2) upon the degree of
relationship existing between fermentation and zymosis ; and (3) as
to the probable mode of action of ferments and contagia.

1 . Pasteur has within the last two years made a most important
modification in his theory of fermentation.! Whilst he formerly
held that fermentations and putrefactions are chemical processes
initiated by independent organisms (bacteria and their allies), and
taking place in correlation with their growth and multiplication, he
has of late shown that similar phenomena may be initiated by the
chemical processes taking place in the tissue-elements of certain
fruits and vegetable tissues, when these are placed under certain

* ‘British Medical Journal,’ December 5, 1871.

f ' Compt. Rend.,’ 1873-4.

138 The Microscopic Germ Theory of Disease. By II. C. Bastian.

abnormal conditions. Grapes, for instance, suspended in an atmo-
sphere of carbonic acid will undergo fermentation, so as to generate
alcohol and other products, even without the presence of torulae or
allied organisms. Other fruits and vegetables treated in the same
way behave more or les3 similarly. Organic multiplication of
independent organisms has therefore now been shown by Pasteur
himself and his followers, not to be an essential factor in the
process of fermentation. With this admission I believe it will be
found impossible hereafter consistently to entertain an exclusively
“ vital ” theory of fermentation, and equally impossible to resist
accepting the broader physico-chemical theory, and with it the
almost inseparable correlative doctrines of archebiosis and hetero-
genesis.

M. Pasteur, in fact, now proves that fermentation takes place
under the influence of altered chemical (nutritive) processes taking
place in unhealthy vegetal tissue, just as we know that similar pro-
cesses may be initiated under the influence of a physico-chemical
process brought about by finely divided platinum. As Dobereiner
pointed out, this material “has the power — and many organic
substances have a similar power — of absorbing oxygen from the air,
and bringing it into a condition in which it can unite with other
substances with which it would not otherwise enter into combina-
tion at low temperatures/’*

And MM. Lechartier and Bellamy, following up the recent
experiments of Pasteur, have found | that in these modified processes
of fermentation, taking place in vegetal tissues, independent
organisms, though they are usually absent at first, not unfrequently
make their appearance after a time. In the process as it occurs in
beet-root and in the potato, on the other hand, bacteria habitually
spring into existence or reveal themselves in great abundance soon
after the commencement of a well-marked process of fermentation.
M. Pasteur will, I suspect, find it difficult consistently to account
for these facts without admitting his long-postponed acceptance of
doctrines of “spontaneous generation.”

2. Respecting the degree of relationship existing between fer-
mentations and zymotic processes, something more definite may
now be said. Between the ordinary previously known forms of
fermentation and zymosis, a most fundamental difference exists
which has hitherto been far too much lost sight of. It is this :
Whereas in an ordinary fermenting fluid the changes initiated by a
ferment take place in a mere isolated mixture of organic substances,
in zymotic processes the changes initiated by contagium occur in
the fluids and tissues of a complex living body. That this latter
fact does exercise a very important influence, and that the two

* * Beginnings of Life,’ vol. i. p. 409.

f ‘ Compt. Rend.,’ November 2, 1874.

The Microscopic Germ Theory of Disease. By II. C. Bastian. 139

processes are not so similar as they have been supposed, we may
now more readily recognize since the processes of fermentation
occurring in vegetal tissues have been investigated. The relation-
ship existing between zymosis and these modified processes of fer-
mentation taking place in fruits and tubers seems, indeed, far more
close than that between the zymotic processes in animals and ordi-
nary kinds of fermentation.

In the process occurring in vegetal tissues, as well as in those
morbid processes which take place in the animal organism, the pre-
sence of rapidly multiplying independent organisms is an occasional
rather than a necessary feature. Though usually absent in other
allied processes, yet we find organisms invariably manifest them-
selves throughout the tissues of beet-root and of the potato, when
these are placed under certain abnormal (“ unhygienic ”) conditions.
And though usually absent from the blood of persons suffering from
specific contagious fevers, yet do we also find organisms invariably
showing themselves in the blood of persons suffering from some of
them, such as relapsing fever and splenic fever. Nay, further,
under the influence of a “ change of conditions ” alone we may
initiate these modified fermentative processes in vegetables ; that is
to say, in ordinary parlance, the processes may originate “ sponta-
neously ” or de novo. But if the modified activity of tissue-elements
suffices to initiate such morbid processes in the vegetal organism,
why may it not occasionally do the same in the animal organism ?
This is a point of view which seems too valuable to be lost sight
of, more especially in the face of the results yielded by our flask
experiments.

3. In conclusion, I would maintain that the facts already known
abundantly suffice to displace the narrow and exclusive vital theory,
and to re-establish a broader physico-chemical theory of fermen-
tation.

Whether the “ ferment ” in any given case be an independent
living organism, a tissue-element, a fragment of not-living organic
matter, or some mere physico-chemical influence (as in the case of
the action of finely divided platinum), the initiated fermentative
change is in each case a result of chemical action. And similarly
with regard to “ contagium,” whether it be an altered though living
tissue-element, a fragment of dead organic matter, a chemical com-
pound (or even the more vague influence of a “ set of conditions ”
which may suffice to generate contagium de novo), we have in each
case to do with gradually initiated chemical changes, distinctive in
kind and gradually terminating in one or other of the recognized
varieties of zymotic affections. The changes in each case where
we happen to have to do with living ferments or living contagia
would be due only to an infinitesimal extent to the organic multi-
plication of such living units, though the decompositions set up by

140 The Microscopic Ger m Theonj of Disease. By II. C. Bastian.

them in their respective fluids may be such as to lead to the forma-
tion of a continuous new birth of independent organisms, all of
which exhibit most active powers of multiplication. The organisms
produced in such cases are therefore only to an infinitesimal
extent lineal descendants of the original living ferments or contagia
under whose influence such fermentative or zymotic processes were
originally established.*

Thus it would appear that the original notion borrowed from
the vital theory of fermentation, that all the organisms met with
in a fermenting mixture are in the strict sense of the term lineal
descendants of those originally introduced as ferments, would dis-
appear with the vital theory itself. Yet this has been the notion
upon which upholders of the germ theory of disease have always
relied so confidently in explanation of the mode of increase of con-
tagium within the body.

Looking, however, at this question from our new point of view,
may we not say that chemical changes established in some one
tissue, or in many, may, by dint of altered blood and other secondary
processes, spread so as to be initiated also in previously sound parts ;
and that thus throughout the body, or in some special regions of
it, living tissue endowed with peculiar and poisonous properties,
or complex alkaloidal compounds, may be engendered in enormous
quantities, some of which may be thrown off from this or that
surface, and act after the fashion of “ contagia” generally?

* ‘Beginnings of Life,’ vol. ii. p. 361.

( 141 )

PKOGRESS OF MICROSCOPICAL SCIENCE.

Atmospheric Dust. — The ‘Academy’ (May 8) says that a micro-
scopical examination of atmospheric dust which fell in parts of
Sweden and Norway on the night of March 29-30, 1875, has led
M. Daubree to believe that it proceeded from a volcanic eruption in
Iceland, as it closely resembled the pumice powder from that country,
and especially that of Hrafftnurhur. M. Nordenskidld, telegraphing
from Stockholm, said : “ Grey vitreous and fibrous powder fell here
with snow on March 30 : several grammes collected.” M. Kjerulf
sent to M. Daubree a specimen of the same dust collected from the
snow by Dr. Kars, between Sondmore and the valley of Romsdal in the
west, and Tryssil, in the direction of Stockholm, in the east. The dust
was found to be composed of fragmentary transparent grains, some
colourless, others more or less brownish yellow. Most of them were
finely striated, fibrous, and full of vesicles, round or elongated, the
latter being most common. Few of these reached the dimension
of t20 millimeter in length, and many were only from to

3^^ millimeter. M. Daubree also recognized minute crystals of
pyroxene and felspar. He reminded the French Academy of several
instances of dust being conveyed by air-currents to great distances.
Thus in February, 1863, sand, apparently from Sahara, fell in the
western parts of the Canaries, transported 32 myriameters ; and more
recently, ashes from the Chicago fire reached the Azores in four
days, accompanied with an empyreumatic odour, which made the in-
habitants suppose that a great forest was in conflagration. In 1783
the dry fog, which covered most of Europe for three months, was
occasioned by dust from an Iceland eruption.

The Functions of the Frontal Ganglion in Dytiscus. — The functions
of the frontal ganglion of Dytiscus marginalis are elucidated by
M. E. Faivre in a paper which will be found in ‘ Comptes Rendus ’
(May 31, 1875). After detailing a variety of experiments, he states, as
a result of his researches, that “ the frontal ganglion specially pre-
sides over the movements of deglutition, determining not only the
contraction, but also the dilatation of the pharyngeal sphincter,
while it reacts at the same time by the recurrent nerve on the
cardiac sphincter. The action of this nervous centre may be excited
by impressions from back to front or the opposite. It associates
together by means of its connection with the encephalon, acts of pre-
hension, mastication, pharyngeal deglutition, and ingestion of food to
the stomachs and the intestine. The suboesophagal ganglion is the
centre, under the influence of which it reacts with the most energy.
In fine, the frontal ganglion, distinguished by special functions from
all other nervous centres of the ganglionic chain, is allied to them
by its essential properties, and, as we may be assured, by its structure
also.” — See Academy, June 12.

The Development of the Nervous System in Limulus. — A very valuable
paper on this subject was read by Mr. A. S. Packard, jun., before the

142

PROGKESS OF MICKOSCOPICAL SCIENCE.

National Academy of Sciences (U.S.A.), and appears in tlio ‘American
Naturalist’ (July, 1875). Mr. Packard observes: After a good many
unsuccessful attempts at discovering tbe first indications of tbe
nervous system in tbe embryo of Limulus, I at length, in making fine
sections, with the aid of the skill of Prof. T. D. Biscoe, discovered
it in a transverse section of an embryo in an early stage of develop-
ment, corresponding to that figured on plate iv., fig. 10, of my essay
on the Development of Limulus Polyphemus , in the ‘ Memoirs of the
Boston Society of Natural History.’ The period at which it was
first observable was posterior to the first blastodermic moult, and
before the appearance of the rudiments of the limbs. The primitive
band now surrounds the yolk, being much thicker on one side of
the egg than the other, the limbs budding out from this disk-like
thickened portion which represents the outer or nervous layer of the
germ. At the time the nervous cord was observed it was entirely
differentiated from the nervous layer proper, and in section and rela-
tion to the nervous layer appeared much as in Kowalevsky’s figure (33)
of the germ of Hydrophilus.*

At a later stage in the embryo (represented by pi. v., fig. 16,
in my memoir), at a period when the body is divided into a head
and abdomen, and the limbs are longer than before, by a series of
sections parallel with the under surface of the body, I could make
out quite satisfactorily the general form of the main nervous cord.
It then forms a broad thick mass, the two cords being united with
small holes between the cords opposite the sutures between the
segments, and situated between the primitive ganglionic centres.
The nervous cord, as in the Acarina, is formed long before the other
internal systems of organs ; the development of the dorsal vessel
some time after succeeding that of the nervous cord, while the
alimentary canal is not formed until some time after the larva is
hatched.

The next stage observed, and one of exceeding interest, was
studied in longitudinal sections of the larval Limulus. If we make
a longitiidinal section of the young king crab when a little over au
inch long, the disposition of the cephalothoracic portion of the cord
is exactly as in the full-grown individuals. The nervous ganglia are
then united into a continuous nervous collar surrounding the oeso-
phagus, no ganglionic enlargements being observed, the collar in fact
consisting entirely of ganglia, the commissures being obsolete ; in
front of the oesophagus and in the same plane as the oesophageal collar
lies the supraoesophageal ganglion, or so-called brain ; not as usual
in the normal Crustacea, raised above the mouth into the roof of the
head. On the contrary, the oesophagus passes behind the brain and
through the collar at a right angle to the plane of the oesophageal
collar and brain taken collectively. Now a section of the larva
before moulting shows a most important and interesting difference as
regards the ganglia which supply nerves to the appendages of the
ccphalotliorax. These are entirely separate, the spaces between
them, where they are connected by commissures, being as wide as
* ‘ Embryologisclie Studnu au Wiirmen uud Arthropoden,’ 1871.

PROGRESS OF MICROSCOPICAL SCIENCE.

143

the ganglia themselves are thick. Five ganglia were observed corre-
sponding to five anterior pairs of members. It is probably not until
after the first moult at least that the adult form of the nervous cord
is attained.

Some interesting questions in the morphology of Limulus arise
in connection with this discovery of the original separation of the
ganglia of the head, which I will simply touch upon. The brain of
Limulus differs remarkably from that of the normal Crustacea,
i. e. the Decapods, in sending off no antennal nerves, but only two
pairs of optic nerves, there being in fact in Limulus no antennae.
In the spiders and scorpions the disposition of the nervous system
only resembles that of Limulus in the thoracic and cephalic ganglia
being somewhat consolidated, but the brain is situated far above the
plane of the thoracic mass, and the commissures are very long, and
here also there are no antennal nerves, no antenna} being present,
but a pair of nerves is distributed to the mandibles. The general
analogy in the form of the anterior portion of the nervous cord to
the Arachnidan, by no means proves satisfactorily to my mind that
the Limulus and Merostomata generally are Arachnida, as some
authors insist, for, besides the remarkable difference in the form and
position of the supraoesopliageal ganglion above mentioned, there are
other differences of much importance, which separate the Mero-
stomata from both the Arachnida on the one hand, and the Crustacea
on the other.

It will now be a matter of interest to study the development of
the nervous cord in the Arachnida, at the stage where the cephalo-
thoracic ganglia are separate, and compare them with the same stage
in Limulus.

The result may possibly show that the appendages of the anterior
region of Limulus are in fact cephalic appendages or mandibles and
maxillfe or maxillipeds, and in part truly thoracic ; as in the spiders
and scorpions the nerves to the maxilhe and legs are distributed from
a common cephalothoracic mass of concentrated ganglia.

The Siliceo-Fibrous Sponges. — A valuable paper has been read on
this subject before the Zoological Society of London, by Dr. J, S.
Bowerbank, F.R.S. It is styled, “A Monograph of the Siliceo-Fibrous
Sponges,” part iii., being the third of a series of memoirs on this class
of sponges. A second communication from Dr. Bowerbank to the
Zoological Society contained the seventh part of his contributions to
a General History of the Spongiadte.

The Spermatozoa of the Petromyzon have been investigated by
Mr. G. Gulliver, F.R.S. , who has recently read a paper on this subject
before the Zoological Society of London.

Structure of the Volcanic Dust of Barbadoes. — The structure of this
dust, which fell in such quantities in the island of Barbadoes in 1812,
has been examined by Professor Hull, F.R.S., who gives the following-
account in the ‘ Geological Magazine’ (June, 1875) : With an objective
power of fifty-five diameters, the dust is seen to consist of angular, or
subangular grains of a translucent reticulated mineral, amongst which

144

PROGRESS OF MICROSCOPICAL SCIENCE.

are dispersed black particles, sometimes angular, and a very few others
of a rounded form and bronze colour. On examining the translucent
grains with the polari scope, and under several different magnifying
powers, it became evident they consist of felspar. The structure is
reticulated and in a very few cases banded ; but owing to the irregu-
larity of the forms of the grains, I was unable to determine to which
class of the felspars they are referable. My impression is that they
are the dust of sanidine, and of a small proportion of plagioclase ;
such, in fact, as would result from the pounding up of trachyte. The
black grains are those of magnetite, and on placing a small magnet
near the dust, a movement is immediately observed amongst the grains,
which increases in intensity as the magnet approaches contact.

The Law of Embryonic Development in Animals and Plants. — We
take from the last number of the ‘ American Naturalist’ (July, 1875)
an important letter, in which Mr. C. R. Dryer, of Ontario Co., N.Y.,
objects in very strong terms to the views expressed in a paper pub-
lished by that journal (May, 1875). He says that the paper in ques-
tion opens with the startling proposition that “ it is a well-known law
in the animal kingdom, that the young or embryonic state of the higher
orders of animals resemble (sic) the full-grown animals of the lower
orders.” If such a law had ever been discovered to exist, the tadpole
and the caterpillar, which are cited in proof, would certainly be good
illustrations of it. But this statement is so far from being “ a well-
known law,” or “ one of the causes of the recent rapid progress in the
study of the animal kingdom,” that no eminent living naturalist or
biologist recognizes the existence of such a law ; or at least no one of
them gives a hint of it in his writings. Agassiz claimed that ancient
animals resembled the embryos of recent animals of the same class,
and that the geological succession of extinct forms is parallel with the
embryological development of existing forms. But if this principle
be true, it is far from meeting the requirements of the “ law ” of this
article. The writer of it may have had in his mind a vague idea of
the law of Yon Baer, which is well known, and which has enabled
naturalists “ to correct their systems of classification,” viz. “ That, in
its earliest stages, every organism has the greatest number of charac-
ters in common with all other organisms, in their earliest stages .” Or,
to put it in language parallel to that of the “ law” of this article, false
syntax excepted, the embryonic state of the higher orders of animals
resembles the embryonic (not the full-grown) state of the lower orders.
The germ of a human being differs in no visible respect from the germ
of every animal and plant : it never resembles any full-grown animal
or plant. It successively loses its resemblance to vegetable embryos,
then to all embryos but those of Vertebrates, then to all but those of
Mammals. Finally, it resembles only the embryos of its own order,
Primates ; and at birth the infant is like the infants of all human
races. But never at any period of its successive differentiations does
it resemble the adult form of fish, reptile, bird, beast, or monkey.

The principle stated is not a law of the animal kingdom. If it
be a law at all, it is a newly discovered one, and applies only to the
vegetable kingdom.

PROGRESS OF MICROSCOPICAL SCIENCE.

145

The proposition to be established then is, that the young or em-
bryonic state of the higher orders of plants resembles the full-grown
plants of the lower orders. The writer finds his first proof in a com-
parison of the fovillse of a pollen grain with full-grown Desmidiae.
The points of resemblance are these : both are minute ; each consists
of a single cell ; and both have an apparently aimless motion. Surely,
these resemblances are not numerous or striking enough to found a
law upon ; and if they were, they have not the remotest bearing upon
the supposed law. Admitting that the fovillte “ may be regarded as
one of the first steps towards the reproduction of plants of the highest
type,” yet they are not in any sense a young or embryonic form of a
plant. The fovillae constitute the male element, and are homologous,
not to the embryo, but to the spermatozoa of animals. The supposed
analogy between a Protococcus and a pollen grain is open to the same
criticism. Nor is the correspondence between a full-grown Botrydium
and a pollen tube of greater value. A pollen tube cannot, in any legi-
timate sense, be called embryonic. The superficial resemblance of
a mould fungus to a stamen is obvious enough ; but in reality no
analogy can exist between them. The spores of the mould are em-
bryos, and will develop, under favourable circumstances, into mould
again. But pollen grains are not embryos, and never, under any cir-
cumstances, grow into what, by any stretch of terms, can be called a
new plant. Neither stamens nor pollen constitute a part of the embryo ;
and no analogy drawn from them can have any bearing upon the laws
of embryonic development. If such a law as the writer claims really
exist, it must be found by studying the development of the ovule, the
true homologue of the animal embryo. In view of such facts, all
“ similar analogies ” and all similar “ proofs of the unity of design of
the Creator ” may be easily dispensed with.

The article proposes to extend the domain of a certain supposed
law of the animal kingdom, so as to include the vegetable kingdom
also. It has been shown, first, that no such law exists in the animal
kingdom ; second, that not a single fact cited as proving it to be a law
of the vegetable kingdom has the remotest bearing upon the question.
If such hasty conclusions as these, wildly jumped at from no data, are
to be allowed under the name of Science, her students will richly de-
serve all the ridicule and sarcasm which a certain class are so fond of
pouring upon them.

The Structure of Connective Tissue. — Dr. G. Thin has read a paper
on this subject before the Royal Society, of which the following is an
abstract: * Transparent animal tissues, when sealed up fresh in aqueous
humour or blood-serum, by running Brunswick black round the edge
of the cover-glass, undergo a series of slow changes, by which,
generally within a period of two to five days, anatomical elements
mostly otherwise invisible become distinct. The paper is chiefly a
record of observations made by this method. The author shows :

1. After a horizontal section of the cornea has been sealed up for
about twenty-four hours, the stellate branched cells are seen to

* ‘ Proceedings of the Royal Society,’ No. 158.

146

PROGRESS OF MICROSCOPICAL SCIENCE.

consist of a mass of protoplasma, sharply defined on every side,
except where it is continuous for a scarcely perceptible distance into
the processes. The nucleus is flattened. The processes become
very fine, glistening, and thread-like almost immediately after leaving
the cell, and, by dividing and anastomosing with the processes of
other cells, form a rich and very delicate network.

2. It sometimes happens, although only in rare instances, that, in
gold preparations, fine dark lines extend between the nuclei, and
correspond in outline and course with the processes seen in the
aqueous humour ; and it is then evident that they are surrounded by
the dark-coloured tracts which form the ordinary network seen in
gold preparations, and which correspond, in outline and varying
degree of development in different animals, ages, and pathological
conditions, with the corneal spaces.

3. Similar appearances to those described in paragraph 1 are seen
in sections of cornea which have been five to ten days sealed up in a
10 per cent, solution of common salt.

4. The quadrangular and long narrow flat cells shown by the
author to exist in the cornea by means of a saturated solution of
potash, are also rendered visible by the above method. They are
best seen in oblique sections, from which, after two to five days, they
fall out singly and in rows. A row of the long narrow cells is often
seen to terminate in quadrangular cells at either end. These cells
have a perfectly hyaline appearance ; their nucleus has a very faint
yellowish tinge, and projects beyond the surface of the cell.

In exceptional instances, in the uncut cornea of the frog, the
long flat cells may he seen, after several days’ maceration, lying on
the primary bundles.

5. In tendon, flat masses of cells are found, on the third to fifth
day, lying on the edge of the preparation and free in the fluid. The
cells are accurately fitted to each other, after the manner of an
epithelium. In the tendo A chillis of the frog they are seen of three
sizes : (a) large cells, corresponding to the flat cells seen on the
surface by nitrate of silver ; ( b ) smaller quadrangular cells, similar
in size to those described by Kanvier, and which have been described
by the author as investing the secondary and tertiary bundles in
double layers ; and ( c ) long, narrow, flat cells, similar to those
described by the author as being isolable by potash, and as covering
the primary bundles.

The masses of the cells of the surface, and of the secondary and
tertiary bundles, can be usually seen to consist of a double layer
separated by a very thin transparent medium.

6. The perimysium and neurilemma are respectively represented
by a double layer of quadrangular and hexagonal cells, identical in
general appearance with an epithelium. Between the two layers
there is a thin transparent medium.

7. From the neurilemma of the sciatic nerve of the frog, when
cut in narrow longitudinal strips, after a few hours, branched cells of
different types of form are seen isolated in the fluid near the cut
edges. These cells are of two well-marked general types. In one

PROGRESS OF MICROSCOPICAL SCIENCE.

147

a small smooth-contoured elongated mass of protoplasma is continuous
at both ends with a fine long thread-like fibre ; in another an
irregularly contoured, but generally somewhat elongated, mass gives
off numerous sharply defined, very fine glistening fibres in all direc-
tions. Sometimes a protoplasmic centre terminates at one end by a
single fibre, and by two at the other. These fibres are often of great
length, and the protoplasmic mass can sometimes only be found by
carefully tracing them whilst moving the object-glass.

8. Fibrillary tissue is seen to be composed of uniform flat ribbon-
like bands, whose breadth approaches the diameter of a human red
blood-corpuscle. These are seen in their simplest form when ex-
truded from the neurilemma of the sciatic nerve of the frog, which
takes place within twenty-four hours’ maceration. From their posi-
tion in this membrane they form part of the transparent medium
which exists between the two layers of quadrangular cells. They
are mostly marked by a puckered appearance transversely.

In skin and tendon, after a few days’ maceration in the sealed
fluid, the fibrillary tissue is seen to be composed of extremely fine
but sharply contoured fibrilke, arranged in parallel bands, which are
of the same breadth as the soft ribbon-like bands which are isolablo
from the neurilemma.

The respective appearances in the neurilemma and in tendon
indicate extremes in the condition of this tissue, and represent,
according to the author, primary bundles of connective tissue.

9. The primary bundles of the cornea are seen only exceptionally
by this method, but can be demonstrated with great precision by
sealing up a frog’s cornea in a mixture of equal parts of half per cent,
solution of chloride of gold and concentrated acetic acid.

10. In nerve-bundles, after twenty-four hours’ maceration in
aqueous humour, some of the medullated fibres may be seen to have
their contour broken transversely by straight hyaline spaces. The
author assigns this appearance to the peculiarity of structure described
by Eanvier.

11. The breadth and appearance of the rods of the frog’s retina
are nearly identical with those of the primary bundles of neurilemma.

The transverse markings described by Max Schultze as being
produced by the action of osmic acid on the rods and cones, resemble
the transverse puckerings in the primary bundles. In both rods and
primary bundles, after prolonged maceration in aqueous humour, the
free ends of each individual element bend in one direction until they
join, and the substance of the ring thus formed undergoes in both
a similar and peculiar process of disintegration. From these facts
the author infers that the rods and cones of the retina are composed
of fibrillary tissue in its simplest form.

12. Transverse sections of muscular fibre, when examined at
intervals, show varying appearances, only a small minority of such
preparations being successful. Successful preparations show one or
more of three appearances ; (a) primary bundles, corresponding to
Cohnheim’s fields ; ( b ) groups of these (secondary bundles), the
aggregate of which fill up the space bounded by the sarcolemma ;

148

NOTES AND MEMORANDA.

(c) a threadwork of fine fibres surrounding tbe primary bundles, in
mesbes.

13. Examination of connective tissue, in various stages of inflam-
mation, yields strongly confirmatory evidence in favour of tbe inter-
pretation given by tbe author to tbe appearances above described.

Lymphatics of the Choroid and Retina. — Tbe ‘Lancet’ (July 10)
says that tbis subject bas been recently investigated by Morano. He
last year announced tbe discovery of minute perivascular lymphatic
channels in tbe choroid, communicating with the perisclerotic space,
and penetrating to the chorio capillaris ; and be bas now ascertained tbe
presence of stomata in tbe pigment layer of tbe retina (formerly called
“ choroidal epithelium ” similar to tbe stomata described by Reckling-
bausen in tbe serous membranes. These retinal stomata are best
marked in tbe frog, and are mostly formed by tbe separation of three
or four of tbe epithelial cells ; they present internally a curious
valvular arrangement due to the presence of three or more small
processes from tbe sides of tbe orifice, and covered by a delicate endo-
thelium. In mammals they are less constant, and may be destitute
of valves, if present.

NOTES AND MEMORANDA.

Preparing Sections of Coal. — Dr. C. Johnson gives tbe following
as tbe method adopted by him in preparing sections of coal, in the
‘Cincinnati Medical News’ (July, 1875): — 1. Macerate suitable
pieces, jor| inch thick, in liquor potassa until they swell and soften.
2. Soak for a few hours in pure water, and drain. 3. Macerate in
nitric acid until tbe colour changes from black to brown. 4. Soak
for a few hours in water, and drain. 5. Put aside in alcohol for a
day or two. If for future use, let tbe pieces remain in alcohol.
6. Fasten in a cutter with paraffin, and make sections. 7. Place in
absolute alcohol. 8. In oil of cloves. 9. In balsam; and 10. Set
aside with a small weight or cover, having, before the mounting,
attached tbe label.

A Mode of Counting the White and Red Blood-corpuscles. —

Tbe ‘Medical Times and Gazette’ (August 14) gives tbe following
account of M. Malassez’s mode of counting tbe number of corpuscles
in blood : “ He draws tbe blood into a peculiar kind of pipette, in
which be dilutes it with a hundred parts of an indifferent liquid, so
that its constituents may be as equally distributed as possible. Tbe
liquid be uses consists of one volume of a solution of gum of specific
gravity 1020, and three volumes of a solution containing equal parts
of sodic sulphate and sodium chloride, also of specific gravity 1020,
to which one drop of a concentrated solution of sodic carbonate may
be added. The diluted blood is transferred from the pipette into a
fine capillary tube of elliptical section, whose dimensions are accu-
rately known ; this is brought directly under the object-glass of the

CORRESPONDENCE.

149

microscope, and the corpuscles are then counted by means of a
micrometer eye-piece. In counting the white corpuscles the blood is
only diluted fifty times instead of a hundred, and a longer capillary
tube is used than in the case of the red corpuscles. To count the
latter it is not necessary to use a tube longer than twice the breadth
of the field of the microscope, whereas for the former it is better to
use one about ten times as long. The number of corpuscles thus
counted gives what the author calls 4 the actual richness of the blood,’
i.e. the number of blood-cells in a unit of volume. To determine
the £ relative richness ’ in the two kinds of corpuscles for any par-
ticular blood, their number must be estimated separately, and then
their relative percentage calculated. M. Malassez has already ob-
tained the following results by his method. He finds that while the
number of red blood-cells is uniform throughout the arterial system,
in the venous it varies with the kind of organ from which the blood
comes. Thus there is an increase in their number in the veins of the
skin and muscles, especially during muscular action. There is also
an increase in the blood from the secreting glands ; but, curiously
enough, this is most pronounced, not during secretion, but when the
organ is at rest. The red corpuscles in the splenic vein are most
numerous when digestion is going on ; whereas, in the intestinal
veins, they are diminished at that time, and increased during fasting.”

CORRESPONDENCE.

Yon Baer’s and Mr. Badcock’s B. polymorphus.

To the Editor of the ‘ Monthly Microscopical Journal.'

3, Queen Street Place, Upper Thames Street,
London, July 30, 1875.

Sir, — In answer to Mr. Garner’s letter of July 10, 1875, in
your August number, I beg leave to say that, in the discussion to
which he refers, the “ doubt ” was not as to the Bucephalus poly-
morphus of Yon Baer being “ parasitical,” because it was well known
that the creature so named by him was found in that state only, and
had been so found by other observers since. There had been a doubt
previously expressed (see April number of Journal) as to whether the
creature I had found, and which was the subject of discussion at the
time alluded to by Mr. Garner, was really identical with Baer’s
Bucephalus, and this doubt begat another, viz. as to whether it was
parasitical or not. I had not found it as a parasite, but always free ;
and this perfectly free state, combined with certain structural and
functional differences in comparison with Yon Baer’s Bucephalus poly-
morphus, pointed to the bare possibility of its being another species
or variety. In addition to other differences already pointed out by
me to the Society, I may here mention that a few weeks since I found
the creatures with two additional balls, in size and shape exactly like

150

CORRESPONDENCE.

the two ordinary ones at the base ; but theso extra ones were at the
extreme tip of the long arms or appendages. Seen thus with four
balls, they were extremely curious.

Will Mr. Garner kindly inform us if he ever found the Buce-
phalus in a free state, and with the characteristic quick movements
which those I found possessed ?

Your obedient servant,

John Badcock.

On Mr. Slack’s Eeply to Mr. J. Mayall, jun.

To the Editor of the ‘ Monthly Microscopical Journal.'

224, Regent Street, London, August 2, 1S75.

Sir, — As you have allowed Mr. Slack to make criticisms on my
letter (before its publication), perhaps you will permit me to make a
few observations in reply to him ?

Mr. Slack is dissatisfied with my interpretation of his paper on
“ Angle of Aperture, Ac.” : I was neither so simple nor so sanguine as
to expect otherwise. I willingly admit that my notions of clearness
of thought and accuracy of language are often opposed to his. But I
had no wish to misrepresent him. As 1 read his paper, its general
tendency — whether avowed or not — was to make the unwary believe
that an optician had come into the field with new lenses of wondrous
excellence. He now says the question raised by him “ related to the
smallest apertures capable of showing lined objects.” Well, the new
lenses are supposed to be the practical embodiment of the smallest
apertures capable of showing lined objects ; to criticise them by their
results was therefore not irrelevant to the question at issue — but the
contrary.

He now points to his exhibition of Surirella gemma, with Zeiss's
D (g-th) lens at the recent Scientific Evening of the Royal Microsco-
pical Society, in confirmation of his views. I refrained from com-
menting on that exhibition, thinking, after his apology for its failure
on the evening, the least said about it the better. But, since he again
insists on referring to the exhibition, I venture to inform those of your
readers who did not witness it, that, compared with Dr. Woodward’s
photograph of Surirella gemma (which may be accepted as the finest
definition hitherto obtained of it), Mr. Slack’s image was only recog-
nizable by the general contours — not by the superficial definition. It
was the old story — Amplification versus Definition — and he seems to
prefer the former.

He says Zeiss’s lenses have taught him a lesson on the utility of
small apertures. The information he seems to have received from their
examination has been commonly accessible for at least forty years past :
for example: — In vol. ii. of the Natural Philosophy published in
1832 by the Society for the Diffusion of Useful Knowledge, p. 50 of
the Treatise on Optical Instruments by Sir David Brewster, we find
the lesson summarized :

“ It should be remarked, that when the objects arc used as opaque,

CORRESPONDENCE.

151

a smaller aperture will do best, viz. about -f of its focus, (for any power
less than 300 decimal standard,) but the magnifier requires to be more
free from aberrations.”

Thus far Mr. Slack has seemingly got with the help of the Reflex
Illuminator.

Sir D. Brewster then presages the most modern developments of the
microscope : “ For transparent objects a larger aperture is absolutely
necessary ; and for some tests it should be equal to its focal distance,
to show the cross strice between the lines on many of the scales, when
the power of the instrument or lens is considerable.”

The finest English, French, and American lenses are practical
examples of the truth of this statement.

Sir D. Brewster then says : “ It is worthy of remark, that the same
aperture that with advantage will develope one class of objects will not
show another with the same success.”

This is evidence that there is room for both large and small-angled
lenses.

Against this we have Professor Abbe quoted : “ that we should
look for improvement in the direction of making objectives of 3 or 4
millimetres focus do the work now done by higher powers.” I main-
tain in opposition to Mr. Slack that Zeiss’s lenses made “ under the
direction of Professor Abbe ” do not substantiate his position.

High -power microscopy has been hitherto very little indebted to
reasonings a 'priori, from the practical impossibility of working exactly
to formulae ; but the lenses, when made, can be put to the test of com-
parison : this is what I did in a series of trials which I endeavoured
to make exhaustive, and I placed the statement of them as evidence
for the consideration of your readers.

That Mr. Slack should seize upon Professor Abbe’s view of the
question does not surprise me ; it is novel, even if it be not suscep-
tible of practical proof. In these days of eager competition, novelty
is at a premium.

I am, Sir, your obedient servant,

John Mayall, jun.

To the Editor of the 1 Monthly Microscopical Journal .’

Ashdown Cottage, Forest Row, August 8, 1875.

Sir, — I am again obliged by your giving me an opportunity of
preventing a month’s misconception arising from Mr. Mayall’s in-
accuracy.

The statement regarding Surirella gemma, as shown by me at the
Scientific Evening referred to, does not correspond with facts. Nume-
rous Fellows saw the markings distinctly divided into beads, as in
Dr. Woodward’s photograph. My apology related to loss of time
in getting the illuminating apparatus into fair action, and to not
obtaining quite enough light for the D eye-piece. A public room and
a tremulous floor are not good conditions for doing, or seeing, any-
thing difficult. Several well-known microscopists have seen the object

YOL. XIV. M

152

CORRESPONDENCE.

perfectly at my Louse with the objective in question, angle 68°. I
find tbe Ligli opinion I expressed of Zeiss’ glasses abundantly con-
tinued by other observers ; and Messrs. Powell and Lealand have just
proved the correctness of Professor Abbe’s view by making a |tli, or,
more properly, a ith (for Mr. de Souza Guimaraens, and kindly lent
to me by him for trial), which with a moderate angle reconciles in a
remarkable manner the three demands for great working distance,
penetration, and resolution. I find the angle, when the objective is
corrected for pretty thick covering glass, about 105°. This glass,
while fit for looking right into a macerated potato leaf for fungi,
displays difficult diatoms very beautifully. I said that when our
opticians were asked to do so, they would make small angles preserve
their own special merits, and do what disproportionately large ones
have hitherto been required for.

I remain, Sir, your obedient servant,

Henry J. Slack.

Angle of Aperture, Chromatic and Spherical Aberration.

To the Editor of the ‘ Monthly Microscopical Journal

1, Bedford Square, August 5, 1875.

Sir, — I regret to find that Mr. Slack is “ unable to understand some
parts of my letter ” on Chromatic and Spherical Aberration. If he
will do me the favour to particularize the parts he does not under-
stand, I will endeavour to make my meaning clear. Let me assure
him, however, that the quotation he gives from Ganot’s 1 Physics ’
simply confirms my statement, that spherical aberration is due to the
forms of lenses ; and when he gave his own version of chromatic
aberration I most assuredly dissented, and now leave it to those
who are familiar with the subject to decide whether they will have
Mr. Slack’s definition of achromatism or that of well-recognized
authorities on optics, who not only assert, but prove, that the condi-
tions of achromatism depend only on the focal lengths of the compound
lenses.

With regard to Mr. Slack’s statement that the more recently made
objectives of Messrs. Powell and Lealand have more perfectly balanced
corrections, this, I presume, is a well-deserved compliment to these
opticians; but so far from its adding weight and strength to his
assertion that “ all chromatic aberration involves spherical aberration,”
it certainly proves quite the reverse.

If proof were needed as to the value of large-angled glasses, I
have but to refer Mr. Slack, and those who hold his views, to the
Jurors’ Keport on the Microscope and its accessories, exhibited in the
Great International Exhibition of 1851. He will there find a well-
digested expression of the opinions of the highest authorities in favour
of a new T4ffth, made by Messrs. Smith and Beck under Lister’s direc-
tion, angular aperture upwards of 75°, and which appears to have
called forth the wonder and admiration not only of the J urors, but of

CORRESPONDENCE.

153

rival opticians, who at once seized upon the improvement and imme-
diately set to work to produce similar lenses. I may remind Mr. Slack
that the best glasses of this period had only about one-half this
angular aperture for the same focal length. These are the object-glasses
of the past, and such as he would now resuscitate, and call improvements.
I would further remind Mr. Slack of the statement of an authority on
these matters : that the separating power, i. e. that which constitutes
the real power of discovery in the ultimate structure of muscular
fibre, tissue, or cell, increases with or is proportionate to the chord
of the angle of aperture, at least up to 150°. Has Mr. Slack any proof
to offer to the contrary? Is it that he sees P. hippocampus with
Zeiss’s |4h with an angle of 48° ? I am in possession of a J-tli by
Dallmeyer, angular aperture 125°, which exhibits none of the defects
Mr. Slack dilates upon as pertaining to large-angled objectives. This
lens has a fair working distance for a thick cover-glass ; it can be
converted into an immersion lens by means of another front, giving
about the same angle of aperture ; with the immersion front sufficiently
unscrewed the aberrations can be balanced for a dry object when the
angular aperture is reduced to 90° or thereabouts, and I detect no
chromatic aberration. Thus it appears to me that Mr. Dallmeyer has
succeeded in placing at our disposal a large-angled objective — for both
wet and dry objects, and also as a comparatively small-angled glass if that
be desired — nearer to perfection than any objective I have seen or
worked with. Nevertheless, I must confess my preference for the
large-angled glass, because of its precision of focus, the sine qua non,
as I deem it, of perfect corrections. With this new objective of 125°
I can see all that I have ever seen with any |4li of the same angle,
and I need not dilate upon the facility of using a 1th as compared
with an -|th.

As to the assertion that a Beck’s ^-0-th, advertised aperture 140°,
only measures 128°, I would much rather place my faith in the high
character of the optician and his experience in recording an exact
measurement than upon the amateur performances of Mr. Slack.

I do not apprehend anything like astonishment on the part of
physiologists who may read my letter. I may, however, refer those
unacquainted with the wTork of practical histology to the ‘ Transac-
tions of the Pathological Society of London,’ and extending over a
period of upwards of twenty-eight years. It is scarcely possible to point
to more able testimony to scientific microscopy, or to more important
evidence of the eagerness with which the medical profession has
availed itself of the latest improvements in high-angled powers, than
that contained in the twenty-five volumes of this Society. Again,
turn to Continental work ; take, for example, the splendid volumes of
Strieker, c Manual of Human and Comparative Histology.’ The main
results in high-power definition spoken of in these volumes have been
produced with high-angled lenses. It is scarcely necessary to say that
the greater part of the valuable pathological work of the schools has
been done with high-angled objectives ; for what are we to infer when
such a man as Dr. J . Hughes Bennett, the eminent Professor of Pathology
in the University of Edinburgh, tells us, in a lecture delivered to the

M 2

154

CORRESPONDENCE.

College of Surgeons of Edinburgh, January 17, 1868, “ On the Atmo-
spheric Germ Theory,” “ I have employed for these investigations the
th of Boss, and frequently a ^ tli by the same maker, and the immer-
sion No. 10 of Hartnack with varying powers of from 600 to 800
diameters linear, and I have confirmed my observations with a lens
made for me by Messrs. Powell and Lealand, of ^b-th of an inch focus,
whereby I obtained a magnification varying from 1250 to 2000 dia-
meters linear. My observations were made in 1841 and 1842, and
carefully repeated and extended to October, 1864, and they have been
since repeated by my assistant, Dr. Eutherford.”

The high powers used by Dr. Beale, Dr. Bristowe, Dr. Bennett,
Dr. Payne, Mr. Lister, Mr. Tomes, Dr. Burdon Sanderson, Dr.
Pritchard, Mr. Lankester, Dr. Michael Foster, Dr. Klein, &c., together
with a host of French and German physiologists, are, it is well known,
lenses of large angular aperture ; and they, in their published works,
constantly write of Boss’s |fh and TLth, of Powell and Lealand’s
T7jtk, ^b-th, and A(Jth, or of Hartnack’s Nos. 10, 11, and 12 immersions
(tVj tV> an<l -2t)> as being the lenses with which their finest work has
been done.* And, lastly, I would point to the wonderful series of
photographs of muscular tissue, blood-corpuscles, &c., by Dr. Wood-
ward, of America, all of which were produced by the aid of high
powers with the largest angle of aperture. Can Mr. Slack produce
or indicate any work done with low-angled powers that will for a
moment compare with these photographs?

I remain your obedient servant,

Jabez Hogg.

Observations on Mr. Slack’s Opponents.

To the Editor of the ‘ Monthly Microscopical Journal .’

Sir — “ Trying Zeiss's Nos. 1, 2 and 3 immersions ( = |th, -j^th,
and ^th) by the test of deep oculars, I find .... the image with
these comparatively low-angled objectives breaks up with any magni-
fication beyond about 1000 diameters.”

Such is the verdict of Mr. John May all, jun., in his observations
on Mr. Slack’s paper on Angular Aperture, which appeared in your
last number.

Would Mr. Mayall be “ surprised to hear ” that the linear magni-
fying powers of a Tbth and ^th are, with even a C eye-piece, 1500
and 2500 respectively, and that an |fh has, with a No. 4 eye-piece,
a power of 1440, according to Smith and Beck’s catalogue.

* On the question -whether an increase of angular aperture is a real advantage
to the physiologist, Dr. Leopold Dippel, in his work ‘ Das Mikroscop und seine
Anwendung,’ vol. i. p. 36, says : “ The result obtained by the immersion system
is therefore equivalent to an increase in the angle of aperture. This arrangement
is consequently a real step in advance, especially with, regard to the most difficult
physiological investigations , as the use of my Ilartnack’s object-glass convinces me
more completely every day.”

CORRESPONDENCE.

155

So much for Mr. Mayall’s notions of the magnifying power of deep
objectives.

Proceeding onward, in the same letter, Mr. Mayall naively remarks,
that if Mr. Wenham will try an experiment “ on Moller’s Probe-Platte
with his Reflex Illuminator and a high-angled immersion lens, he will
see a luminous field ; whereas, with a pneumo-lens he obtains a dark
field ” ; he then asks the following question : “ Whence comes the
luminous field in the immersion lens if not from its having the power
to collect rays which are totally reflected when the pneumo-lens is
used?”

If Mr. Wenham replied to the question put by Mr. Mayall, he
might very properly inquire what on earth “ Moller’s Probe-Platte ”
had to do with the question, and whether a plain glass slip would not
answer the same purpose. The answer to Mr. Mayall’s question
“ Whence comes the luminous field ? ” is obviously that there is nothing
whatever in his letter to show that any rays totally reflected when the
dry lens was used, were picked up by the immersion ; for anything
that appears to the contrary, the dry had a smaller angle than the
immersion lens, which would perfectly account for the phenomenon.

Following this amusing letter by Mr. John Mayall, jun., comes
one on the same subject from Mr. Jabez Hogg, in which we find a
most charming proposition. After quoting from Parkinson, who says
a compound object-glass can be constructed “ which shall be at the
same time both aplanatic and achromatic,” Mr. Hogg says : “ An object-
glass may therefore be achromatic and not aplanatic,” and hence he
concludes that some object-glasses which are not achromatic must be
aplanatic.

Mr. Hogg thinks Mr. Slack’s theory is not coherent.

Your obedient servant,

Crito.

Angle of Aperture of Object-glasses.

To the Editor of the ‘ Monthly Microscopical Journal '

London, August 10, 1S75.

Sir, — I have no intention of entering into the present object-glass
question as an advocate of any particular opticians. This I have
always avoided, even in the case of those who are guided by my advice
in optical matters. If a partisan comes forward to publish the merits
of an object-glass of one maker, an opponent is sure to appear in
favour of another, and the consequence is that a scientific question
becomes a party one, and degenerates into a mere trade squabble.

In the last ‘ M. M. J.’ we have a verbose letter from Mr. Mayall,
assuming the calm indifference of a looker-on amused at “ the pro-
digious display of personalities.” It may, however, appear to another
indifferent “ looker-on ” that his own letter, from its tone, may vie

156

CORRESPONDENCE.

with any of them in the failing that he deprecates in others,* and so
the cavil, embittered by feelings of rival interest, spreads to all who
use object-glasses.

My attention has been called to a letter from Mr. Stodder, appear-
ing in the ‘ Cincinnati Medical News ’ for July last, wherein he
attempts to claim pre-eminence for Mr. Tolies, and asserts that all
recent improvements have been taken from him. I cannot reply in
any of the American journals, particularly as the letter in question is
such a manifest puff of Mr. Tolies’ object-glasses, from one professedly
his agent, that I am surprised at its insertion as a scientific article. Not
to lose the chance that now offers, in the present small-angle con-
troversy, Mr. Tolies is there boldly put forward as the maker of the
best object-glasses in the world. It is imputed that Messrs. Powell
and Lealand have based their recent improvements on the fact of
having seen Mr. Tolies’ four-combination ^th (belonging to Mr. Crisp).
As these gentlemen make it a rule never to answer insinuations against
themselves, I venture to state that I have examined their new glass,
as well as the notorious ^th, and am in a position to say that they
have not copied, and further, that they also consider this much-
vaunted object-glass not a subject for imitation.

The four-system combination is claimed by Mr. Tolies as his in-
vention, but it is no novelty. Andrew Eoss made a great number of
them about twenty years ago. Mr. Tolies’ agent (Mr. Stodder) refers
to me with his characteristic rancour as claiming arrangements belong-
ing to others. That in which one single front works both wet and
dry is not “ copied from America,” neither do I claim it, as many of
the four-combination lenses just referred to by the late Andrew Eoss
having a single front, work equally well both wet and dry. The
effect partly depends upon the perfection of the correction, and
whether there is sufficient range in the adjustment to enable the
lenses to occupy a closer position than usual.

Having shown that the four-combination system is no novelty, I
must say the same of the doublet or “ duplex ” front now claimed by
Mr. Tolies as the great improvement of his lenses. This was tried
and suggested by myself years ago : I then formed a high opinion of
the arrangement, and consequently described and figured it in my
essay “ On the Construction of Object-glasses,” page 172 of the
first vol. of this Journal (March, 1869), which makers of object-
glasses may have noticed. I am gratified to find that my idea of its
merits is confirmed by practice, and that it will find a place amongst
improvements in the history of the object-glass.

The real question at issue at present, viz. the superior value of
small apertures versus large ones on a certain class of objects, appears

* I shall not revive the controversy of the theory of dry and immersion
apertures ; but in referring to my “ Keflex Illuminator ” Mr. Mayall has simply
mistaken the action as described by me. All rays are made to fall at such an
angle on the top surface of the slide (not the cover), that they are totally reflected,
and the only light that can pass through is at the contact points of the object,
vhich adhere to that surface. The total reflexion is the same irrespective of any
aperture of object-glass, and the field equally dark whether this is used with
water between the front lens or not.

PROCEEDINGS OF SOCIETIES.

157

to me to be a very simple one, and easily decided. I will undertake
to produce a series of objects that can be well shown with the small-
aperture glasses, upon which the higher ones will completely fail
(even the 1 80°) ; these must be left for dots and stria) on the flat and
most excruciating tests.

I need not look to, or care for the maker’s name, as this has nothing
to do with the question , provided the glasses are well made and corrected,
as so many of them are by different makers : thus all jealousies may
be avoided. Mr. Slack’s views concerning the use and value of
apertures considerably less than 180° for general observation, are so
obvious, and have been endorsed by eminent microscopists who have
really made all the most important investigations, that I am surprised
at the opposition which, however, is evidently biassed by trade
feelings.

As yet English makers need have no anxiety on the score of
superiority ; they will not be found behind either Continental or
American in the most recent improvements.

I am, Sir, yours very truly,

F. H. Wemham.

PROCEEDINGS OF SOCIETIES.

Quekett Microscopical Club.

Ordinary Meeting, June 25. — Dr. Matthews, F.R.M.S., President,
in the chair.

Nominations were made of candidates to fill the offices of Presi-
dent, Vice-Presidents, Secretaries, and vacancies on the Committee.
Dr. Matthews was proposed as President for the ensuing year.

The Secretary explained the method of using the scale for the
measurement of angular aperture devised by Mr. J. W. Stephenson,
who had kindly pi*esented to the club a number of copies for the use
of the members.

The Secretary described two lamps which had been patented by
Mr. Parkes, of Birmingham. One had a circular and the other a flat
wick, and in each case the light was placed in the focus of a parabolic
reflector, throwing a beam of approximately parallel rays. There was
also a tinted glass in the front of each reflector to correct the yellow-
ness of the flame.

Mr. B. T. Lowne gave a continuation of his lecture on the His-
tology of the Eye, treating principally of the minute structure and
functions of the retina, and giving the latest and most approved
methods of hardening, cutting, and mounting sections of it for micro-
scopical examination.

158

PROCEEDINGS OF SOCIETIES.

Adelaide Microscope Club, South Australia.*

The monthly meeting of the club was held on April 30. Dr.
Whittell presided.

Mr. Francis showed some glasses he had succeeded in ruling with
fine lines to show the effect of diffraction.

The Chairman said the subject for study that evening was “ The
Animal and Vegetable Parasites of the Human Body,” and after-
giving a general summary of the facts known respecting these bodies,
proceeded to show several varieties of them under the microscope. In
referring to the Microsporon furfur , he noticed the statement of some
dermatologists that it required considerable skill to demonstrate it.
He had not found this to be so. If some of the scrapings from a skin
affected by it be soaked in Beale’s staining fluid for a few hours, the
sporules will be found to be coloured, while the dead epithelial scales
will be scarcely touched. In referring to Hydatids, the Chairman
showed a slide containing a minute portion of the contents of a cyst
in the hepatic region. There were booklets of the echinococcus and
thousands of minute ovoid bodies, which Dr. Cobbold, of London (to
whom similar slides had been sent), had pronounced to be protospermial
bodies, although differing somewhat from any he had before met with.
The patient from whom they were obtained by tapping had ultimately
made a good recovery.

The Bev. Dr. Bleasdale, a distinguished visitor from Victoria,
called attention to the effect of oblique light obtained by removing the
mirror of the microscope and viewing an object illumined by the
direct light of a candle or lamp placed to the right or left of the ob-
server.

A committee was appointed to arrange for the holding of a
conversazione.

Microscopical Section of the Academy of Natural Sciences
of Philadelphia.

February 1, 1875. — Director W. S. W. Ruschenberger, M.D., in
the chair.

Dr. J. Cheston Morris, chairman of the committee appointed to
examine optically the Jgtli and J^th objectives displayed at the late
Exhibition of the Section, made a report, which was referred to a
committee, and of which the following is an abstract :

The lenses submitted for examination were a (Vth, iVrth, and ^th
made by Tolies, all immersion, a -^th immersion by Wales, and a
Ajth, dry, made by Powell and Lealand. The points which we con-
sidered it requisite for us to examine were, 1st, flatness and clearness
of field ; 2nd, definition ; 3rd, penetration ; 4th, resolution ; 5th, angle
of aperture ; 6th, achromatism ; 7th, amplification ; 8th, working focus.
Penetration or depthing is the property by which a lens shows us with
tolerable distinctness objects or structures lying just within or beyond
the best focal point or plane, and is of the greatest importance in

* Report supplied by Dr. Whittell, Adelaide.

PROCEEDINGS OF SOCIETIES.

159

tissue investigations. [As a method for testing penetration (hitherto
a desideratum), Dr. Morris proposes to examine a cover ground so as
to be T-jj^th of an inch thinner on one edge than its opposite, and to
measure with an eye-piece micrometer the breadth of the band of
ground glass distinctly visible (flatness of field being presupposed)].
Again, resolving power is the property of showing certain lines,
markings, or shadows on diatoms, &c., and may or may not coexist
with best defining power ; it depends in great measure upon angle of
aperture, and is to a great extent an antagonistic property to penetra-
tion. The dependence of resolving power upon angle of aperture is
very well shown by placing a Pleurosigma angulatum, for instance,
under a ith or T\jth, with such an eye-piece as will amplify suffi-
ciently, and putting the compound body horizontally in front of a
direct light. In this position no lines will be seen, but by rotating
the compound body on its axis an oblique light is obtained, which at
different angles, according to the power of the objective, will bring
out transverse or oblique lines, and finally dots appearing as hexagons.
The following results were thus obtained :

Power employed.

Trans-

verse

Lines.

Oblique

Lines.

Hex-

agons.

Total

Obscu-

ration.

Angle

of

Aper-

ture.

Spencer’s 1-inch, C eye-piece (lines begin-1

°

25

°

o

o

30

o

60

ning to show at 25°) f

Spencer's J-inch, C eye-piece

20

25

50

60

120

„ pinch, C eye-piece

0

40

65

130

Tolies’ yg-th, immersion (lines broken into!
dots) /

..

8

20

85

170

Wales’ ^th, immersion

0

70

140

Powell and Lealand's -^th, dry

ii>

20

63

126

Tolies’ g^th, immersion

0

70

140

We found that the A^th of Tolies gave good results as to flatness
and clearness of field, penetration, resolution, amplification, and
working focus or distance. Its definition is only fair, as also its
working angle of aperture, while as to achromatism there is much
improvement to be desired, and in working focus and general useful-
ness much might be gained by setting the front lens less deeply and
reducing the brasswork of the face. We were, however, agreeably
surprised by the facility with which it can be handled.

The Jyth of Powell and Lealand was not equal to the above in
clearness of field, nor in definition, nor in working focus. Its pene-
tration was equal, as also was its amplification, but its angle of
aperture was 14° less.

The yVth of Wales is a very superior lens, giving good defi-
nition, resolution, and penetration, while its other qualities are very
fair.

The y^th of Tolies, although constructed mainly for use with
oblique light, showed itself a good lens, with direct central rays,

160

PROCEEDINGS OF SOCIETIES.

as to flatness and clearness of field, definition, amplification, and reso-
lution ; its angle of aperture is wonderful, while its achromatism
and even its penetration are very fair, and its working focus sufficient.

From the observation noted above we deduce one very important
fact, viz. that the different appearances of lines, dots, hexagons,
&c., on Pleurosigma angulatum are not only the varied results of
angle of aperture, of amplification, and of illumination, but that
they may be obtained with less and less obliquity of light as we
increase the power of the objective ; thus making it evident that high
powers with direct central light show us clearly things which we
rather guessed at than saw (owing to the increased chance of spherical
and chromatic aberration and distortion from the employment of
oblique light) with lower ones.

We would conclude, therefore, by recommending these high-power
lenses to those engaged in microscopic research, not as capable of
doing all work — a 1-inch is as indispensable to a histologist as a
j-th — but as likely to be proportionately useful in unravelling the
mysteries of organic life.

Dr. J. Gibbons Hunt desired it to be distinctly understood that
he had nothing to do with the preparation of the report, and did not
wish to be held responsible as a member of the committee for the
views advanced in it. He considered that it embodied the obsolete
views of Carpenter and Beale in regard to penetration, which term
should be dropped from the vocabulary of microscopists. He believed
that penetration and resolution can be and have been combined in the
best objectives.

Dr. J. Cheston Morris stated that the report was based upon a
careful and conscientious examination of the objectives by the com-
mittee, and was in accordance with the well-known laws of reflexion
and refraction of light. He had submitted the report to Professor
George F. Barker (of the University of Pennsylvania), who had
approved it so far as the optical questions were concerned, except,
perhaps, on the subject of penetration, which he attributed to imper-
fect spherical correction. He could have wished that Dr. Hunt had
expressed his dissent from the document as freely in private, when it
was shown to him, as he had just done. All he did at that time was
to suggest some slight alterations and additions, which being made,
Dr. Morris was led to expect his adhesion to the report. As to the
question of penetration being a useless one, he considered the pre-
sence of this quality in the lenses of Tolies of great moment. High
angle of aperture and penetration have not been combined in the ob-
jectives of the German, English, and French makers to the same degree.

Dr. Hunt said that what one man calls penetration another does
not, terms often being used without an exact knowledge of the mean-
ing intended to be conveyed by them. He preferred a lens that will
give one absolute focus rather than three indistinct ones. The con-
ditions of testing are frequently fallacious, and imperfect illumination
is one of the most prolific sources of error. With low objectives, as,
for example, a 1th, used with the amplifier, very satisfactory and
reliable results can be obtained.

In conclusion, Dr. Hunt proposed that at some time during the

PROCEEDINGS OF SOCIETIES.

161

next year any resident member or members of tbe Section should
prepare one dozen microscopical preparations, extemporaneous or
otherwise, representing the many different departments of micro-
scopical work, and exhibit the same at a meeting or meetings of
the Section, under his own apparatus and in his own way, the
object being to test men in regard to their technological skill, he
offering to do the same. Those competent may compare and judge
the results.

On motion of Dr. Morris, it was resolved that the Curator be
authorized to purchase for the Section a Nobert’s test-plate.

San Francisco Microscopical Society.

The regular meeting of the Microscopical Society was held in its
rooms, on Thursday evening, March 4, with a full attendance of
members. President Ashburner in the chair. Messrs. Robert Munch,
C. Troyer, and Theo. H. Hittell, were present as visitors.

Dr. W. F. McAllister, United States Navy, was elected a cor-
responding member.

The Secretary announced the reception of the recent edition of
the ‘ Micrographic Dictionary,’ a very valuable work for reference.

Dr. D. V. Dean, city chemist and microscopist of St. Louis, pre-
sented a copy of the Seventh Annual Report of the Board of Health of
that city, which contained valuable reports of microscopic investi-
gations of meats and parasites.

A communication from the committee appointed to receive contri-
butions for the National Polish Museum was read, also interesting
letters from Messrs. W. H. Walmsley, of Philadelphia, J. W. Deems,
and Captain John H. Mortimer, of New York, corresponding
members.

Dr. A. Mead Edwards, of Newark, N.J., and Mr. A. F. Dod, of
Memphis, corresponding members, favoured the Society with lengthy
and valuable letters containing assurances of interest and assistance
in the good work, the latter gentleman accompanying his letter with
a very interesting paper on Mr. Tolies’ new four-system immersion
-jijjth objective. The notes prepared by Mr. Dod were a memorandum
of the tests made by him in the way of comparison with other first-
class objectives of a less angular aperture, both with central and
oblique illumination, and various test-objects. His results point
directly to the fact that when the low-angled objectives failed to give
as satisfactory results as the -j^th, using low eye-pieces, they were
utterly vanquished when increased eye-piecing was applied to amplify
the image ; and this too with central light. The generally received
doctrine that the wide angles are only valuable for work with oblique
light, would seem to be overthrown ; and the conclusion of Mr. Dod
and the gentleman who aided in the test was unanimous that this
tenth of Tolies’, with the highest attainable angle of aperture, can
meet the narrow angles in the field that has been hitherto regarded as
peculiarly their own, and not only successfully compete with, but
actually and undoubtedly surpass them, one and all.

So much has been said and written on this subject that any addi-

162

PROCEEDINGS OF SOCIETIES.

tional testimony is useful ancl interesting to all students in micro-
scopy ; and Mr. H. C. Hyde, Vice-President of the Society, who has
given the mechanical features of the microscope in their adaptability
to test objects a large amount of his attention, was called upon to
make some remarks on the subject. Using the black-board and accom-
panying his statements by the reading of a paper by J. Edwards
Smith, of Ashtabula, 0., published in the microscopical department
of the ‘ Cincinnati Medical News,’ Mr. Hyde was able to so explain
the matter as to interest and instruct all present.

Mr. Munch exhibited some fine drawings from the microscope, of
various minerals and rock sections, which were peculiarly beautiful
and valuable for their accuracy and detailed finish.

Mr. Hanks exhibited a binocular microscope which he had caused
to be made from a pattern of his own, and a number of which he had
imported for miners and mineralogists. The want of such an instru-
ment has long been felt, and the combination of its many features, in
the way of portability, movements, and cheapness, were noted satis-
factorily.

Mr. W. H. Pratt, corresponding member, donated four slides,
mounted by him with the anthers and pollen of sweet elysium, pollen
from the osage orange, fly’s foot, and fine gold.

Dr. J. W. Winter donated two slides with objects, prepared and
mounted by him in balsam, being a longitudinal and transverse section
of human cuspidata, showing very clearly the enamel, dental tubulars,
cementum, and periosteum.

Mr. Henry Edwards, honorary member, donated two specimens of
the Dytiscus marginalis, from Europe, and which is a favourite object
with microscopists for the tarsi ; also a great variety of material, for
examination and mounting, in the way of insects.

Mr. C. G. Ewing donated a slide, mounted with a microscopic
barnacle in glycerine taken out of a shell, found on the bottom of the
steamship £ Vasco de Gama.’

Perhaps the most valued acquisition for future research is that of
the donation by Mr. Fisher, of the U.S.S. c Tuscarora,’ of samples of
a series of twenty-three deep-sea soundings from Cape Flattery to the
Aleutian Islands, and of twenty-six from San Diego to Honolulu.
These have been arranged, numbered, and labelled, with statistics
regarding latitude, longitude, deptli and temperature, in each case, by
Dr. H. W. Harkness, assisted by Messrs. J. P. Moore and Kinne, and
form a field for study for months to come.

After the exhibition by Mr. Hyde of a series of very beautifully
and wonderfully arranged slides, particularly one, which was a picture
made up of butterfly scales, arranged as a bouquet of flowers in a vase
of diatoms, &c., with two birds, lizard, and various insects, mounted
by Dalton, London, the meeting adjourned.

The stated meeting was held at the Society’s rooms, Thursday
evening, March 18, with President Ashburner in the chair, and a fair
attendance of resident members. Dr. Eisen, corresponding member,
and Mr. W. A. Skidmore, visited the rooms.

Two proposals for resident membership were received, and Henry
Molineaux, Esq., was elected as such.

PROCEEDINGS OF SOCIETIES.

163

Under the head of donations to the cabinet, Mr. C. G. Ewing
presented a slide mounted with a colony of polyps, Sertularia, in
glycerine, from San Pedro Bay.

Colonel C. Mason Kinne donated five slides, mounted by him,
comprising the elytron of a beetle, showing very marked peculiari-
ties ; raw cotton from near Visalia, Cal. ; scale of salmon ; raw cotton
from New Mexico ; and white horse-hair ; the three last named being
mounted in balsam, for the polariscope, and which proved worthy
objects for observation with that accessory. Colonel Kinne exhibited
some living protococcus, which vegetable, moving freely in the same
drop of water with the animal forms Paramoecium vorticella and others,
aided to show how nearly the two great kingdoms are allied in the
so-called lower forms of life.

Dr. Eisen exhibited the tentacles of a barnacle ( lepas ), and a
variety of marine algrn ( ulva ).

An adjourned meeting was held at the rooms of the Society on
Thursday evening, April 8, with a full attendance of members,
Mr. H. Edwards, honorary member, Dr. A. Barkan, Dr. Geo. H.
Powers, Dr. A. P. Hayne, Prof. Wm. H. Brewer, and Messrs. S.
Heydenfeldt, jun., Chas. E. Case, Sam. B. Christy and B. B. Redding,
were present as visitors.

Messrs. Wm. A. Woodward and W. F. Myers were elected
resident members.

The Society was also the recipient of a valuable gift from Dr. J.
N. Eckel of this city, in the work of his distinguished countryman,
Ehrenberg, on microscopic geology. It is truly a great work — one
now very rare — embodying the results of the life-long labour of one
of the most celebrated scientists of the age on microscopic research,
illustrating the microscopic marvels of earth and ocean, as found in
various parts of the world, in a series of large and beautifully coloured
plates, with all that perfection of detail for which the German
engravers are so justly celebrated. The Society may be congratulated
on the acquisition of so valuable an addition to its library.

The following was unanimously adopted :

Resolved, — That the thanks of the San Francisco Microscopical
Society be tendered to Dr. J. N. Eckel of this city, for his magnificent
and valuable donation of Ehrenberg’s ‘ Mikrogeologie,’ and that the
trustees be authorized to extend to Dr. Eckel the courtesies of the
rooms and apparatus, with a cordial invitation to use them at his
pleasure.

Under the head of donations to the cabinet, Mr. C. D. Gibbes
presented a portion of a nest supposed to have been made from wild
hemp ; a sample of hard-pan, twenty-one feet below the surface of
the ground, and a fungus found on wild rose, all from Middle River,
San Joaquin.

Dr. Gustaf Eisen presented four slides, mounted by him with
fresh-water algte, palate of Pliysa radula, pedicellarium of echinus, and
sphoeridium of echinus. Dr. Eisen explained the position and forma-
tion of the latter, using the black-board, and stated that it was con-
sidered the organ of taste in the well-known sea-urchin.

Mr. Hanks called attention to a sample of infusorial earth in the

164

PROCEEDINGS OF SOCIETIES.

cabinet, and stated that a fragment of the same, placed in the hands
of a London microscopist by Captain Mortimer, corresponding
member, had proved exceedingly interesting, and to contain some rare
minute forms of fossil Diatomacese.

The feature of the evening was a lecture by Dr. Adolp Barkan
“ On the Construction and Uses of the Ophthalmoscope.” The Doctor
used the black-board with facility, giving a technical description of the
vai'ious parts of the human eye, aided by frequent diagrams, and
illustrated by reference to the eyes of a rabbit and a hog, from which
the light of other days had departed.

Commenting on the need of an instrument to enable one to see the
interior of a living human eye, he stated that up to 1845 no such had
been obtained ; but acting on the fact then discovered, that light
entering the eye was not absorbed but reflected, and that the interior
of the body could be made luminous, Professor Helmholtz, in 1851,
invented an instrument which had the desired effect of illuminating
the eye ; and catching the rays in the rebound, so to speak, the
observer found a new field for his scientific powers.

The practical uses of the ophthalmoscope are of enormous value,
as the diagnosis of a disease in and on the rear portion of the eye can
be made without guesswork, the various substances and coats of the
optic being shown with astonishing clearness.

After exhibiting patterns of the instrument, and stating that
although some forty odd varieties had been invented, none were of
any practical improvement on the one first produced by Helmholtz,
who had seemed to hit on the right thing at once, Dr. Barkan brought
out his menagerie of living animals and proceeded to demonstrate
what could be seen.

An immense frog, strapped to a piece of board, stared and blinked
at the interested scientists, and proved himself a tractable and worthy
aid to the evening’s study. A subcutaneous injection of a solution of
cinnabar filled his blood-vessels with minute crystals, and pouring
down the interior of the eye could be seen the coursing blood, with
now and then a flashing sparkle of the cinnabar.

A rabbit claimed its share of attention, and the instrument
brought out the peculiar construction of its eye, the absence of
pigment and insertion of the optic nerve being noticeable.

A cat, swathed and enclosed in a heavy sack for obvious reasons,
attracted her quota of observers, and richly repaid them all. The
peculiar manner in which the light was reflected in colours of red,
green, and yellow, made a picture not before deemed possible to the
casual observer.

A pleasantly disposed dog was interviewed with the instrument,
and quietly permitted an intelligent gleam to sparkle forth, showing
much the same beauties as were by his feline friend and co-labourer
in the good cause.

After voting the Doctor a hearty vote of thanks for his delightful
and interesting lecture, the meeting adjourned. — Cincinnati Medical
News.

r\r West Sc sc.

The Monthly Micro sc opi cal J onmal .0 c t .1.1 875.

TT . CXVTI

<00
* H

THE

MONTHLY MICROSCOPICAL JOURNAL.

OCTOBER 1, 1875.

I. — On Cephalosiphon and a New Infusorion.

By Dr. C. T. Hudson, LL.D.

( Taken as read before the Royal Microscopical Society.)

Plate CXVII.

Nature is certainly feminine, for she is the most capricious of
deities ; now refusing the slightest favour to her ardent worshipper,
and then, when he has lost heart and is about to give up the pur-
suit, overwhelming him with a lavish kindness that is almost as
embarrassing as it is tardy. For years I had hunted in every
brook, pond, and ditch, within some miles of my house, and always
with the hope that some day among my other captures I should
light on Cephalosiphon and Ptygura ; two rotifers that I had
never seen, and which, so far as they had been described, stood
sadly in the way of what seemed to be a tolerably satisfactory way
of classifying the Rotifera. So at last I determined to accept pro-
visionally some suggestions that had been made about these two
doubtful species, and to consider that Ptygura Melicerta and Cepha-
losi'phon Limnias had no right to their rank, but that the former
was the immature condition and the latter a temporary state of
some other species.

When I had struck out their names from the list of rotifers, my
classifying went gaily on ; and as I had got rid of two of my chief
stumbling-blocks I soon finished my scheme to my own satisfaction.
It was now Dame Nature’s turn. I had given up all hope of
winning her favour and of finding the creatures, and I had resolved
to do without both it and them ; I had made (as I thought) a
perfectly satisfactory classification in spite of her ; I had played my
best card and it remained for her to trump it ; which she promptly
did, proving to me in a trice that perfect classification is often but
another name for imperfect knowledge ; for on my going to Nailsea
ponds (an old haunt of mine) to get something fresh for my micro-
scope, on the very first weed I plucked were Cephalosiphon and
Ptygura, both on the same leaf ; and a short inspection gave me an
uneasy suspicion that the latter was probably a mature form, and
that the former was a permanent one ; .so that my knot was not to
be cut by the simple method of striking their names out of the list
of rotifers.

It seems a paradoxical thing to say that ignorance makes classi-

VOL. XIV. N

166 Transactions of the Royal Microscopical Society.

fication easy, but it will hardly be denied that after our knowledge
of a natural group of animals has reached a certain point, their
classification is made more difficult by a wider acquaintance with
the species that the group comprises. For the more common
forms, which are always the great majority, fall readily enough into
divisions and subdivisions whose boundaries have that delightful
sharpness which seems to make it so easy to study Nature in books,
but which unluckily Nature herself never offers to the observer.
Further research generally brings to light those rarer intermediate
forms (of which Cephalosiphon and possibly Ptygura are examples)
which are at once the despair of the classifier and the delight of the
naturalist ; and, when the attempt is made to fit these into the
original scheme, it is then found that Nature knows no sharp lines
of demarcation and has no symmetrical system.

The best classification of Nature’s facts will always lack that
precision and symmetry which is so dear to most men — who, if
they had had the maldng of their own skeletons, would have
substituted cylinders, spheres, and triangles for Nature’s free curves
and flowing surfaces.

What had made it so difficult to include Cephalosiphon in any
system of classification was this ; that while it appeared to be a
tube-making rotifer of the Mehcertan family, yet, unlike all other
tube-makers, it had only one antenna instead of two, and that one
on the wrong side of its body, namely on the side opposite to that
of the mouth.

Now the Philodines have only one antenna, and that antenna
is on the side opposite to the mouth : moreover (as Mr. Cubitt had
pointed out) some of the Philodines occasionally form tubes round
themselves. I have several times met with Rotifer macroceros so
encased. Its long flexible antenna seemed to resemble that of
Cephalosiphon, as also did its habit of moving it about from side
to side before emerging from its tube ; so that Mr. Cubitt’s sug-
gestion, that Cephalosiphon was a temporarily encased Philodine
and not a Mehcertan at all, seemed worth entertaining ; though
adopting it was to fall into another difficulty, as Mr. Slack’s picture
in ‘ Marvels of Pond Life ’ showed that the creature had only one
large wheel of cilia, and not two small ones.

In fact Cephalosiphon had no right to exist if there was to be
any comfort in classifying ; for its single antenna opposite to the
mouth seemed to throw it out of the Melicertans, and its large
single wheel to prevent its entering among the Philodines.

Ptygura too was a difficulty ; for here was a creature whose
form seemed to place it among the tube-makers, and yet which
made no tube. Ehrenberg’s description of it had made me think
that it was some young Mehcertan seen before it had begun to
construct its tube. I had overlooked Mr. Gosse’s statement (in the

On Cephalosiphon, &c. By Dr. C. T. Hudson. 167

‘ Popular Science Beview,’ vol. i. p. 490) that he had found two
specimens of a fine wheel-animal without a tube, and which he had
reason to think was Ptygura. “ One of the animals,” says Mr.
Gosse, “ laid a large egg actually under my eye, so that it was in
adult age. Its general figure was somewhat trumpet-shaped,
slightly swelling in the middle The disk was very large, forming
a nearly circular outline, and partially surrounded by a layer of
granular tissue. The foot terminated in an adhering sucker, whose
figure resembled that of a glass stopper in a phial ; the dilated ex-
tremity of this was capable of adhering to any foreign substance.”

The specimen I found at Nailsea — unluckily a solitary one —
tallied very closely with this description ; but it was very awkwardly
placed, half bent round a leaf, so that I could only get occasional
glimpses of the body and head, while of the foot I could see but
little. I satisfied myself however that it had no case, though I was
not quite sure whether there was not a sort of fluffy gathering at
the foot. The foot too was thicker than it is in other Melicertans,
and more coarsely wrinkled.

For the present, at all events, I am afraid that Ptygura must
be retained as a Melicertan that does not make a tube.

I was more fortunate with Cephalosiphon. There were many
specimens on the weed, and of various sizes ; and the very first I
looked at was a half-grown one protruding sufficiently from its
tube to show that it had a smooth, jointless foot, precisely like that
of a Melicertan, but quite unlike that of a Philodine.

The trochal disk was oval, with a gap in it on the side opposite
to the mouth. Two parallel rows , of cilia — the upper large, the
lower small — ran round the edge of the disk separated by a groove
which led down into the mouth (Fig. 1, a); and the lower row of
cilia were continued round the edges of the mouth after the usual
fashion in Melicertans. But what struck the eye at once was the
long flexible antenna. When the creature was withdrawn into
its tube the antenna generally projected above it like a thin wand.
It was turned too to a curious use; for when Cephalosiphon
had made up its mind to emerge from its retreat, it hooked its
antenna (see Fig. 1, b) over the side of its tube, and getting a
good purchase, hoisted up its body into a great curve, and then
letting go its grip of the case, unbent itself, and at once unfolded
its disk. The antenna bore on its end a brush of diverging
setae, and was often not quite straight. It was attached to the
animal in an unusual way, for it had a broad base something like
that of the thorn of a rose, as if its great length required extra
support. I am not aware that there is any Melicertan that at all
resembles Cephalosiphon in these two particulars — that is to say,
that makes so odd a use of its antenna, or that has its antenna
broadening out into a bracket-like base.

n 2

168 Transactions of the Royal Microscopical Society.

There were, as I have already said, many specimens of various
sizes ; and the variations in size were so great that I had little
doubt that they represented considerable variations in age, and that
it was in consequence most probable that Cephalosiphon was a
genuine Melicertan forming its tube from early youth, and not a
temporarily encased Philodine.

I searched therefore all over the weed in the hope of finding an
infant Cephalosiphon ; and I was not unrewarded. Close to a large
cluster of the tubes of Archimedea remex (a new infusorion, to he
described lower down) was a very tiny tube, barely the of an
inch long, and out of which protruded a wheel-animal (Fig. 1, c )
Plate CXVII., about 2I0 °f an inch in length, and like a Cephalo-
siphon only with a hump instead of the characteristic antenna. I
isolated the creature and kept it under daily observation for nearly
a fortnight, and during that time had the pleasure of seeing it
grow rapidly into the form of an adult Cephalosiphon (Fig. 1, cZ).

In twenty-four hours the hump had developed into a short
antenna ; in four days the young Cephalosiphon had grown from
5^0 of an inch to ; in six days to -dt ; in twelve days to -fs-

I was too busy to look at it during the next two or three days,
and when I did find the leisure the creature was gone — tube and
all. It was perfectly healthy on the twelfth day, and about half
grown. This conclusively shows that Cephalosiphon is not an
encased Philodine — even if there were no other reasons to be
brought forward.

Since I made the above observations I lighted on a reference to
papers of Mr. Gosse and Mr. Slack on Cephalosiphon in the ‘ Intel-
lectual Observer,’ vol. i., 1862. I have read these papers care-
fully, and can quite confirm Mr. Slack’s statement that the trochal
disk is not bi-lobed with a tendency to further division. It is, as
he says, nearly circular with a deep notch in front of the antenna.
Mr. Slack too is quite right in saying that the antenna carries
setae at its extremity. It is clear that Mr. Gosse’s specimens (sent
to him by Mr. Slack) were not in perfect health, and did not, in
consequence, give that admirable observer a fair chance. He him-
self says that his specimens “ were chary of exposing their facial
charms,” and that his “ delineation of the form of the disk rests on
a single individual.”

No doubt the rotifers had suffered in their journey ; for
when they are fresh from their pond they expand their disks
freely.

I have omitted to state that after numerous trials I succeeded
in getting nearly the whole of a full-grown specimen out of its
tube ; I could not see the extremity of the foot, but on the part
which I did see — quite seven-eighths of the whole — there was no
trace of any segmentation, nor of a telescopic joint, nor of any

169

On Cephalosiphon, &c. By Dr. C. T. Hudson.

processes whatever. There were a few faint transverse wrinkles
just as there are in ordinary Melicertans.

CepJialosvphon was not my only prize. I found attached to the
same weed ( — Anacharis alsinastrum — ) clusters of long thin
brown tubes which at first I thought to be those of Cephalosiyhon.
They proved however to contain a curious infusorion which I
believe to be new, and which I have named from its frequently
assumed corkscrew shape, and from its rows of cilia used like
banks of oars, Archimedea remex. It really makes its own
tube ; for I have seen very young specimens in tubes just begun,
and I have left a group of tubes each with its full-grown Archi-
medea in it, and after two days have found them still with their
inhabitants inside them, and each tube lengthened by about
of an inch. The full-grown Archimedea is about do of an inch,
and the longest tube I have met with is Ao of an inch. The
tube of course is far too long for its inhabitant, who as a rule
fives in the top of it, though occasionally it backs down the tube
nearly to the bottom. When inside the tube the animal is extended
to its full length as in Fig. 2, where a is the ciliated front down
which a groove ciliated on both sides leads to the entrance of the
mouth d. On protruding from its home it first remains straight
quivering its cilia : then, if not alarmed by any shake, or by any-
thing passing, it thrusts quite half its body from its tube, and
twists it up into the screw-like form seen in Fig. 3.

On watching the groove, along the edges of which the cilia are
in full action, tiny atoms may be seen hurried along to the mouth :
tap the table, and Archimedea flashes down the tube, quick as a
serpula ; and if it is in the upper and more transparent end it may
be seen moving itself gently to and fro as if hesitating whether
to return to the aperture or to seek a safer refuge down below.

These are very tantalizing creatures, for they readily desert
their tubes ; and in spite of all my care I frequently found every
tube empty after the third or fourth day’s captivity. Under
ordinary circumstances it is a great piece of good luck when a
tube -maker leaves its tube, as then the observer gets a capital
chance of making out points of structure that could not be seen
when the animal was encased ; but Archimedea' s tube is so frail,
and the animal so shy, that the leaf it is on must be transferred to
the glass cell on the stage of the microscope with the least possible
handling ; and as the leaf is broad the cell must be so too, so that
when the creature swims out of its tube (as I have seen it do) it
is almost impossible to keep in the field for more than a few seconds.
I tried the heroic method of scraping a group of tubes off the leaf
on to my compressorium, and after many failures did at last get
one animal out alive and uninjured, as well as free from the debris
of the tubes, the rubbish on the leaf, &c., &c. : all of which would

170

Recent Progress in our Knowledge of

have rendered it hopeless to try to confine it within reasonable
limits. I have already described its front. In the middle of the
animal and close to the side was a contractile vesicle, Fig. 2, b, which
opened and shut every two seconds or so. There was a clear space
c at the end, but this I did not see contract. The shaded portion
e might have been a stomach, but this I could not determine. The
whole of the surface was spotted with granules, and was such as to
impair greatly the definition of any internal organ. There was an
anus at the side, towards the end opposite to the mouth ; and twice
I saw the creature dart up the tube (so as to bring the vent above
the top of it), shoot out its excrement, and instantly dart back
again.

The groups in Fig. 3 are carefully copied from two that were
together on the same leaf, and which retained some of their
inhabitants for about four days, and then dropped to pieces
gradually, and disappeared in about four days more.

II. — Recent Progress in our Knowledge of the Ciliate Infusoria.
By G. J. Allman, M.D., F.R.S.

Plate CXYIII.

I believe that the object contemplated by the addresses which it
has been the custom of your Presidents to deliver year after year to
the Fellows of the Linnean Society will be best fulfilled by making
them as much as possible the exponent of recent progress in bio-
logical science. The admirable addresses with which my distin-
guished predecessor has during his long tenure of office so greatly
enriched our journal, afford an example as regards the exposition of
botanical research which may well be followed in biology generally.
The field, however, which thus offers itself is so wide, the activity
in almost every department so intense, that the necessity of restrict-
ing the exposition within a limited area becomes imperative if it be
expected to produce anything like a definite picture instead of a

EXPLANATION OF PLATE CXVIII.

Fig. 1. — Strombidium sulcatum. 2 a. Crystalline bodies which have been liberated
from it, and show amyllaceous reaction with iodine. After Biitschli.

„ 2. — Polykricos Swartzii. 2 a. Thread-cell-like body liberated from its outer
layer. 2b. The same with the filament ejected. After Biitschli.

„ 3. — Torquatella typica. After Lankester.

„ 4. — Silicious lattice-like case of a Dictyocysta. After Haeckel.

„ 5. — Didinium nassutum. 5 a. The same in the act of seizing a Paramcecium.

5 b. The same with the prey passing through the oral orifice into the
interior of the body. After Balbiani.

/ficroseopio al Journal

PI. C3VIII

\ 3 :>Q 3 f

7J. JVe6 i-ScCo. Iv&o .

the Ciliate Infusoria. By G. J. Allman. 171

vast assemblage of images confused and ill-defined by tlieir very
multiplicity and by the condensation -which would be inseparable
from their treatment.

While thus imposing on myself these necessary limits, it is
almost at random that I have chosen for this year’s address some
account of the progress which has recently been made in our know-
ledge of the Ciliate Infusoria — a group of organisms whose very
low position in the animal kingdom in no way lessens them interest
for the philosophic biologist, or their significance in relation to
general morphological laws.

To enable you to form a correct estimate of the value of recent
researches, it may be well to bring before you in the first place, as
shortly as possible, the chief steps which have led up to the present
standpoint of our knowledge of these organisms.

It is scarcely necessary to remind you that the first important
advance which during the present century was made in our know-
ledge of the Infusoria dates from the publication of the great work
of Ehrenberg,* whose unrivalled industry opened up a new field of
research when, by his expressive figures and well-constructed
diagnoses, he made us acquainted with the external forms of whole
hosts of microscopic organisms of which we had been hitherto
entirely ignorant, or which were known only by such figures and
descriptions as the earlier observers with their very imperfect micro-
scopes were able to give us.

Ehrenberg, however, as we all know, did not content himself
with portraying the external forms of the microscopic organisms
to whose study he had devoted himself, but sought also to deter-
mine their internal structure, of which scarcely anything had been
hitherto known. In this direction, no less than in the other, the
perseverance of the celebrated microscopist never flagged ; but,
unfortunately, at the very commencement of his researches he
slid into a misleading path, and was never again able to find the
right one.

Everyone knows how Ehrenberg, in accordance with precon-
ceived notions of the high organization of all animals, attributed to
the Infusoria a complicated structure ; how, while he rightly dis-
tinguished them from the Botiferm with which they had been
confounded by 'previous observers, he yet regarded them as inti-
mately related to these representatives of a totally different type ;
and how, in attributing to them a complete alimentary canal with
numerous gastric offsets, he took this feature as their most impor-
tant character, and designated them by the name of Polygastrica.
And it is probably a matter of surprise to many of us, that with the
overwhelming mass of evidence which subsequent research has
brought to bear against the truth of the polygastric theory, the

* ‘ Die Infusionsthierchen als vollkommene Orgamsmen.’ Leipzig, 1838.

172

Recent Progress in our Knowledge of

great Prussian observer should still adhere with undiminished
tenacity to his original views.

Among the authors who, since the publication of the ‘ Infu-
sionsthierchen,’ have contributed most to a correct estimate of the
morphology, physiology, and systematic position of the Infusoria,
the names of Dujardin, Yon Siebold, Stein, Balbiani, Claparede, and
Lachmann, and most recently, Haeckel, stand out conspicuous.

The way to a philosophic conception of the Infusoria and of
other beings which occupy the lowest stages of life was undoubtedly
opened up by Dujardin* when he drew attention to the existence of
a peculiar form of matter of semi-fluid consistence and of nitro-
genous composition, and which, though totally undifferentiated, is
yet endowed with properties essentially characteristic of vitality.
To this remarkable substance he gave the name of “ sarcode.”
The sarcode of Dujardin has of late years been described chiefly
under the name of protoplasm, and its wide extension and im-
portance in the economy of all living beings, whether plants or
animals, has been recognized as one of the most comprehensive
facts in biology.

After Dujardin, the first who from a strong position offered
battle to the authority of Ehrenberg was Carl Theodor von
Siebold.f Yon Siebold rejected in toto the polygastric theory,
and, so far from admitting a complexity in the organization of
the Infusoria, he regarded them as realizing the conception of
almost the very simplest form of life, and attributed to them the
morphological value of a cell.

Let us see what is involved in this most significant comparison.
The essential conception of a cell is, as you know, that of a more or
less spherical mass of protoplasm with or without an external
bounding membrane, and with an internal nucleus or differentiated
and more or less condensed portion of the protoplasm. It was to a
form of this kind that Siebold compared the body of an Infusorium.
He called attention to the soft protoplasmic mass of which the body
mainly consists ; to the external firmer layer by which this is
surrounded ; and to the variously shaped body differentiated in the
protoplasm, to which Ehrenberg had gratuitously attributed the
function of a male generative organ. Here then were, according to
Siebold, the protoplasm body-substance, the bounding membrane,
and the nucleus of a true cell.

The morphological value thus attributed to the true Infusoria
— under which were included the Flagellatse — was extended by
Siebold to Amoeba and its allies, and to the whole assemblage so
constituted he assigned the position of a primary group of the

* “ Sur l’organisation des Infusoires,” ‘Ann. des Sci. Nat.,’ 1838; and ‘Hist,
des Infusoires,’ Paris, 1841.

f Siebold, ‘Lehrbuch dor vergleichenden Anatomic,’ 1845.

the Cilicde Infusoria. By G. J. Allman. 173

animal kingdom, to which he gave the name of Protozoa, whose
essential character was thus that of being unicellular animals. He
then divided his Protozoa into those which had the faculty of
emitting pseudopodial prolongations of their protoplasm (Amoeba,
&c.), and those in which the place of the pseudopodia was taken by
vibratile cilia or by lash-like appendages. To the former he gave
the name of Ilhizopoda ; to the latter he restricted that of Infu-
soria ; and lastly, Be divided the Infusoria into the mouth-bearing,
Stomatocla (Ciliata), and the mouthless, Astomata (Flagellata).
From every point of view Yon Siebold’s conception of the mor-
phology of the Protozoa, and his sketch of their classification, how-
ever much this may have been subsequently modified, must be
regarded as marking out an epoch in the history of zoology.

Shortly after this the unicellular theory was strongly supported
by Kolliker,* and received further confirmation from the researches
of Stein, t who, however, was unable to accept it to its full extent.
With an industry almost equal to that of Ehrenberg, Stein had the
advantage of the more philosophic views of organization which had
emanated from the newer schools of biology, and to him we are
indebted not only for more accurate views of the structure of the
Infusoria, but for the first important contributions to our know-
ledge of their development ; and though the opinion which he at
one time entertained, that the true Acinetae are only stages in the
development of the higher Infusoria, has been abandoned by him,
he has nevertheless demonstrated the presence in an early period of
the development of certain species, of peculiar pseudopodial pro-
cesses resembling the characteristic capitate appendages of the
Acinetae, an observation of importance in its bearing on the rela-
tions of these last to the true Infusoria. No doubt can remain,
after Stein’s observations, that the Infusoria in their young state
have the morphological value of a simple cell, and it is only after
their development has become advanced, and that a marked diffe-
rentiation has begun to manifest itself in this primordial condition,
that there can be any difficulty in accepting their absolute uni-
cellularity.

About this time Balbiani drew attention to some very important
phenomena in the life history of the Infusoria. J It had been
known even to the early observers that the Infusoria multiplied
themselves by a process of spontaneous fission. They had been
frequently observed in the act of transverse cleavage, and had also
been noticed in what appeared to be a similar cleavage taking place
in a longitudinal instead of a transverse direction. Balbiani, liow-

* Zeitschr. f. Wissens. Zool., 1849.

f Stein, ‘ Der Organismus der Infusionstliiere,’ 1867.

X Balbiani, “Recherches sur les organes gene'rateurs et la reproduction des
Infusoires,” ‘Comptes Rendus,’ 1858, p. 383.

174

Recent Progress in our Knowledge of

ever, showed that this apparent longitudinal cleavage had in many
cases an entirely different significance ; that it was, in fact, not the
cleavage of a single individual, hut the conjugation of two distinct
ones ; and he connected this phenomenon with what he regarded as
a true sexual act.

It was then known that besides the nucleus which occupied a
conspicuous position in the protoplasmic mass, there existed in
many Infusoria another differentiated body similar to the nucleus
hut smaller, and either in close contact with it or separated from it
by a greater or less interval. To this body the ill-chosen name of
“ nucleolus ” had been given. Now, Balbiani’s observations led him
to believe that under the influence of conjugation this so-called
nucleolus underwent a change and developed in its interior a
multitude of exceedingly minute filaments or rod-like bodies, to
which he attributed the significance of spermatozoa ; while at the
same time the nucleus became divided into globular masses, which
Balbiani regarded as eggs, and in which he believed he could
recognize a germinal vesicle and germinal spot. We should thus,
according to this interpretation, have in the Infusoria the two
essential elements of sexual differentiation, the spermatozoa and
the egg.

Stein, though differing from Balbiani in certain details, accepts
in its general facts the sexual theory, and maintains the spermatic
nature of the rod-like corpuscles to which the nucleolus appears to
give rise. But however real may he the phenomena described by
Balbiani and by Stein, the correctness of assigning to them a
sexual significance may he called in question ; and it is certain that
subsequent observation has not tended to confirm the hypothesis
that we have in the Infusoria true eggs fecundated by true sperma-
tozoa.

Claparede and Lachmann, two able and indefatigable observers
fresh from the school of the great anatomist Johannes Muller, now
entered the field, and their joint labours have given us a valuable work
on the Infusoria.* In this an entirely new view of the morphology
of the Infusoria has been introduced. Receding widely from the
unicellular theory of Siebold, they approximate towards- the views
of Ehrenherg in assigning to the Infusoria a comparatively complex
structure; but instead of adopting the polygastric theory of the
Prussian microscopist, they attribute to the Infusoria a single well-
defined gastric cavity occupying the whole of the space limited
externally by the outer firm boundary walls of the softer proto-
plasmic mass ; while this mass is regarded by them as nothing
more than a sort of chyme by which the gastric cavity is filled.
According to this view, the nearest relations of the Infusoria would

* Claparede et Lachmann, ‘Etudes sur les Infusoires et les Rhizopodes.’
Geneve, 1858-61.

the Ciliate Infusoria. By G. J. Allman. 175

be found among tbe zoophytes, and their proper systematic seat
would be in the primary group of the Ccelenterata.

Though few zoologists will now be prepared to accept the con-
clusions of the Genevan naturalist and his associate, the ccelenterate
relations of the Infusoria has recently found an advocate in Greeff.*
In an elaborate memoir on the Yorticellae, Greeff sees in the very
well-marked distinction between the external or cortical layer and
the internal soft body-substance, a proof of the views maintained
by Claparede and Lachmann ; and he considers this position still
further confirmed by the presence in Epistylis flavicans of nume-
rous oval or piriform, brilliant, well-defined capsules, which are
generally distributed in pairs below the outer layer, and which,
under the influence of a stimulus, emit a long filament, thus closely
resembling the thread-cells so well known as characteristic elements
in certain tissues of the Ccelenterata.

It must be here remarked that the presence of similar bodies in
the Infusoria, where they have been described under the name of
trichocysts, has long been known. Though varying in form, they
all possess a more or less close resemblance to the thread-cells of
the Coelenterata. Their presence undoubtedly indicates a step
upwards in the differentiation of the organism, but, as we shall
presently see, it offers no valid argument against its unicellularity.

In his admirable ‘ Principles of Comparative Anatomy,’ f
Gegenbaur expresses doubts as to the sexual nature of the repro-
ductive phenomena of the Infusoria, and is disposed to regard the
so-called embryo-sphere, to which the nucleus gives rise, in the
light of a proliferous stolon, from which several zooids are in some
cases thrown off. Arguing from the Acineta-like form of the
young in the higher Infusoria, as shown by Stein, and comparing the
transitory condition of this with the permanent condition of the true
Acinetae, he believes that we are justified in regarding the Acinetae
as the ancestral form from which the proper Infusoria have been
derived. He further compares the contractile vesicle and its canals
in the Infusoria with the water vascular system of the worms, and
believes that a parentage with these higher forms is thus indicated.
Gegenbaur, moreover, expresses himself strongly against the uni-
cellular theory. He regards, however, the absence of distinct cell
nuclei in the substance of the Infusoria as affording evidence of
their composition out of several “ Cytodes ” or non-nucleated proto-
plasm masses rather than out of true nucleated cells.

Still more recently, Biitschli has given us the results of obser-
vations on the conjugation of Paramoecium aurelia.% He is led,

* Greeff, “ Untersuckungen iiber den Ban und die Naturgeschickte der
Yorticellen,” £ Arckiv fur Naturg.,’ 1870.

t ‘Grundsiige der Vergleickenden Anatomie,’ 1870.

% O. Biitsckli, “Einiges iiber Infusorien,” ‘ Arckiv f. Microscop. Anat.,’ 1873.

176

Recent Progress in our Knowledge of

however, to doubt the validity of the sexual interpretation of the
conjugation. He found that in certain cases in Paramoecium
aurelia and in P. colpoda the so-called spermatic capsule into
which the nucleolus had become converted, had entirely disap-
peared without any evident change in the nucleus ; and he con-
cludes that fecundation of the bodies regarded by Balbiani as eggs
cannot be here entertained. Indeed, he will not allow that we
have evidence entitling us to regard the appearance of filaments in
the interior of the nucleolus as affording any indication of true
spermatozoa. He offers no explanation of this appearance, but he
calls attention to the fact that both Balbiani and Stein noticed that
in transverse division of the Infusoria — a phenomenon with which
conjugation can have nothing to do — the nucleolus frequently
enlarges and acquires a longitudinal striation like that of the
nucleolus in the supposed production of spermatozoa during conju-
gation. Balbiani maintains that this striation during cleavage is
only superficial, but it nevertheless affords an argument against
assigning any more important significance to the very similar ap-
pearance in the case of conjugation.

On the whole it would appear that the spermatozoal nature of
the striae visible in the nucleolus of the conjugating individuals —
even admitting that these striae represent isolatable filaments — has
not by any means been proved, while the phenomenon of conjuga-
tion in the Infusoria would seem to correspond rather with the
conjugation so well known in many lower organisms, where it takes
place without being in any way connected with the formation of
true sexual products.

In the same memoir the results of observations on some other
points in the structure and economy of the Infusoria have also been
given by Butschli. He records the occurrence of minute crystal-
like laminae in the interior of a marine Infusorium ( Strombidium
sulcatum) rendered remarkable by a conspicuous girdle of tricho-
cysts which surround its body (PI. CXVIII., Figs. 1 and 1 a). The
crystal-like corpuscles seem to be of the nature of starch, for on the
application of iodine they assume a beautiful violet colour. It does
not appear from Butschli ’s account of these bodies that they have
not been introduced from without, and the chief interest of the
observation seems to be in the discovery of an amyllaceous body
assuming a crystalline form. He had previously met with similar
bodies in a parasitic Infusorium ( Nyctotherus ovalis), as well as in
a Gregarina (G. blattarum).

He also describes, under the name of Polyhricos Sivartzii (Fig. 2),
a new Infusorium which he frequently found in the fjords of the
south coast of Norway and in the Gulf of Kiel, and which he regards
as especially interesting, from the fact that with a true infusorial
organization it contains, irregularly distributed in the outer layer

the Ciliate Infusoria. By G. J. Allman. 177

of the body, numerous capsules (Figs. 2 a and 2 h) indistinguishable
from the true ccelenterate thread-cells. These bodies, however, are
never included in a special investment, and he justly regards their
presence as affording no argument against the unicellular nature of
the Infusoria. He lays it down as a probable distinction between the
trichocysts of the Infusoria and genuine thread-cells, that the former
have the power of ejecting their contained filament from both ends of
the capsule, while we know that in the thread-cell it is only one end
which gives exit to it. This double emission of a filament appears
to have been observed by Butschli in the trichocysts of a large
Nassula, hut the distinction is certainly not a generally valid one.
There is no doubt that in the majority of cases the trichocyst emits
its filament from only one end of its capsule, exactly as in the
thread -cells of the Coelenterata, and it is hard to see in what
respect the bodies noticed by Biitschli in his Polylcricos Swartzii
essentially differ from true infusorial trichocysts. In conclusion,
he declares himself strongly in favour of the unicellularity of the
Infusoria.

The reproductive process was lately followed by myself through
some of its stages in a very beautiful Vorticellidan obtained
abundantly from a pond in Brittany.* The zooids which form the
colonies in this Infusorium are grouped in spherical clusters on the
extremities of the branches. They present near the oral end a
large and very obvious contractile vesicle, and have a long cylin-
drical nucleus curved in the form of a horseshoe.

In the internal protoplasm are also imbedded scattered green
chloropliylloid granules. No trace of the so-called nucleolus was
present in any of the specimens examined.

Among the ordinary zooids there were usually some which had
become encysted in a very remarkable way, and without any
previous conjugation having been noticed. These encysted forms
were much larger than the others and had assumed a nearly
spherical shape ; the peristome and cilia disk had become entirely
withdrawn, the contractile vesicle was still obvious, but had ceased
to manifest contractions ; brownish spherical corpuscles with
granular contents, probably the more or less altered chloropliylloid
granules of the unencysted zooid, were scattered through the
parenchyma, and the nucleus was not only distinct, but had
increased considerably in length. Round the whole a clear gela-
tinous envelope had become excreted.

In a later stage there was formed between the gelatinous
envelope and the cortical layer of the body a strong, dark-brown,
apparently chitinous case, the surface of which in stages still
further advanced had become ornamented by very regular hexagonal
spaces with slightly elevated edges. In this state the chitinous
* British Association Reports, 1873.

178

Recent Progress in our Knowledge of

envelope was so opaque that no view could be obtained through it
of the included structures, and in order to arrive at any knowledge
of these it was necessary to rupture it. The nucleus thus liberated
was found to have still further increased in length, and to have
become wound into a convoluted and complicated knot. Along
with the nucleus were expelled multitudes of very minute corpuscles
with active Brownian movements.

In a still further stage the nucleus had become irregularly
branched, and at the same time somewhat thicker and of a softer
consistence; and finally, it had become broken up into spherical
fragments, each with an included corpuscle resembling a true cell
nucleus in which the place of a nucleolus was taken by a cluster of
minute granules.

In this case the original nucleus of the Vorticellidan had thus
become broken up into bodies identical with the so-called eggs of
Balbiani, but this was unaccompanied by any conjugation or by the
formation of anything which could be compared to spermatozoal
filaments.

What I believe we may regard as now established in the
phenomena of reproduction in the Infusoria is, that besides the
ordinary reproduction by spontaneous fission of the entire body,
the nucleus at certain periods, and after more or less change of
form has occurred in the Infusorium body, becomes broken up into
fragments, each including a corpuscle resembling a true cell-
nucleus; and that this takes place without necessarily requiring
the influence of conjugation or the action of spermatozoa ; that
these fragments after their liberation from the body of the In-
fusorium become developed — still without the necessity of spermatic
influence — directly or indirectly into the adult form.

Whether proper sexual elements ever take part in the life
history of the Infusoria remains an open question.

Everts * has given an account of observations which, with the
view of testing the statements of Greeff, he made on Vorticella
nebulifera. Greeff, as we have seen, followed Claparede and
Lachmann in attributing to the Vorticellae a true coelenterate
structure ; and Everts, by his own investigations, has convinced
himself of the untenableness of this view, and has been led to
regard the Vorticellae as strictly unicellular.

He recognizes the distinction between the cortical layer (which
forms not only the periphery of the body but the whole of the
stalk on which this is supported), and the central mass in which
the nutriment is deposited, collected into pellets, and digested ; but
instead of regarding this central mass as chyme, he looks upon it
as an integral constituent of the entire body, like the central

* Everts, Untersucbungen an Vorticella nebulifera. Sitzungsberichte der
Physikalisch-Medicinischen Societat zu Erlangen. 1873.

the Ciliate Infusoria. By G. J. Allman.

179

portion of an Amoeba. The nucleus is imbedded in the inner side
of the cortical layer, which is itself differentiated into certain
secondary layers. He describes the deeper part of the cortical
layer as exhibiting a rotation of its granules independent of the
rotation which occurs in the central parenchyma, and moving in a
direction opposite to that of the latter. Everts’s account of the
structure of Vorticella is thus in accordance with the conception of
it as a cell with a parietal nucleus; a cell, however, in which
differentiation is carried very far without the essential character of
a simple cell being thereby lost.

Everts regards the external wall as corresponding with the
ectoderm, and the internal softer body-substance with the endoderm
of higher animals. If by this the author meant to indicate a
homological identity between the structures thus compared, it is
plain that he would have taken an entirely mistaken view based on
a misconception of the essential nature of an ectoderm and
endoderm. These membranes are essentially multicellular, and
are always results of the segmentation of the vitellus in a true
ovum. They can therefore never be attributed to a unicellular
animal, in which no true segmentation process ever takes place. In
his rejoinder, however, to an elaborate criticism of his memoir by
Greeff, he explains that he intended to compare the two layers of
the Infusorium body analogically, not morphologically, with an
ectoderm and endoderm.

The same author has further made some interesting observa-
tions on the development of Vorticella. He has noticed that repro-
duction is here ushered in by a longitudinal cleavage, in which
after division of the nucleus the body of the Vorticella becomes
cleft into two halves, still seated on the common stalk. Each of
these develops near its posterior end a wreath of vibratile cilia,
while the peristome and the cilia disk over the mouth are entirely
withdrawn, and then breaks loose from its stem and swims freely
away. These free-swimming Vorticellae now encyst themselves, the
cilia disappear, and the contents of the encysted animal acquire a
uniform clearness with the exception of the nucleus, which persists
unchanged. In the next place the nucleus breaks up into eight or
nine pieces, and then the wall of the cyst becomes ruptured and
gives exit to these fragments, which now appear as spontaneously
moving spherules. These increase in size, develop on one end a
cilia wreath, within which a mouth makes its appearance, and the
free-swimming nucleus-fragment becomes gradually changed into a
form which entirely agrees with the Trichodina arandinella of
Ehrenberg.

These Trichodina: now multiply by fission, first developing a
posterior wreath of cilia, and then dividing transversely between
the anterior and posterior wreaths. After this each fixes itself by

VOL. XIV. O

180

Recent Progress in our Knowledge of

the end on which the mouth is situated ; a short stem becomes here
developed, and the cilia wreath gradually disappears. Then upon
the free end the peristome and cilia disk make their appearance, and
the growth of the stem completes the development.

Everts remarks that in this process we have an example of
alternation of generations. There is one point, however, in which
he has overlooked its essential difference from a true alternation of
generations, namely, the absence of any intercalation of a proper
sexual reproduction. .

Eay Lankester * has subjected to spectrum analysis the blue
colouring matter of Stentor ceeruleus. This occurs in the form of
minute granules in the cortical layer of the animal, and Lankester
finds that it gives two strong absorption bands of remarkable
intensity, considering the small quantity of the matter which can
be submitted to examination. He cannot identify these bands
with those of any other organic colouring matter, and to the
peculiar pigment in which he finds them he gives the name of
stentor in.

He has also examined the bright green colouring matter of
Stentor Muller i, and finds that instead of giving the stentorin
absorption bands, it gives a single band like that of the chloro-
phylloid matter of Hydra viridis and of Spongilla.

Eay Lankester t has also described, under the name of Torqua-
tella typica (Eig. 3), a remarkable marine Infusorium, which, though
quite destitute of true cilia, can scarcely be separated from the
proper Ciliata. With the general structure of the ciliate Infusoria,
the place of a peristomal cilia wreath is taken by a singular plicated
membrane, which forms a wide, frill-like, very mobile appendage,
surrounding the oral end of the animal, and projecting to a con-
siderable distance beyond it. The author regards Torquatella
typica as the type of a distinct section of the Ciliata to which he
gives the name of Calycata.

Of all the authors who since Yon Siebold have applied them-
selves to the investigation of the Infusoria, Haeckel must be men-
tioned as the one who has brought the greatest amount of evidence
to bear on the question of their unicellularity. In a very elaborate
paper which has quite recently appeared, f and which is remarkable
for the clearness and logical acuteness with which the whole subject
is treated, Prof. Haeckel, resting mainly on the observations of
others, and partly also on his own, argues in favour of the
unicellularity of the Infusoria from the evidence afforded both by
the phenomena of their development and by the structure of the
mature organism. He confines himself chiefly to the Ciliata —

* ‘ Quart. Journ. Mic. Sci.,’ 1873. f Ibid., 1874.

I Haeckel, “ Zur Morphologic der Infusorien,” Jenaiscke Zeitschr., Band vii.
heft 4, 1873.

the Ciliate Inf usoria. By G. J. Allman. 181

which, indeed, he regards as the only true Infusoria — while he
considers the unicellular ity of the Flagellata as too obvious to
require an elaborate defence. The value of this paper will be
obvious from the analysis of it which I now propose to give.

In stating the argument derived from development, Haeckel
does not accept as established the alleged sexual reproduction of the
Infusoria, and he believes it safest to regard as non-sexual “ spores ”
the bodies ( Keimhugeln ) which result from the breaking up of the
nucleus, and which Balbiani regarded as eggs.

These bodies consist of a little mass of protoplasm usually
destitute of membrane, and including a nucleus within which one
or more refringent granules admitting of comparison with a true
nucleolus may sometimes be witnessed — characters which are all
those of a simple genuine cell. From this spore the embryo is
developed by direct growth and differentiation of parts ; but however
great may be the differentiation, there is never anything like the
formation of a tissue.

The development of the Infusoria is thus entirely in favour of
the unicellular theory. This theory, however, is just as strongly
supported by the study of their mature condition; and here
Haeckel gives an admirable exposition of the structure of the true
or Ciliate Infusoria.

The parts which are common to all Ciliata and which first
differentiate themselves in the ontogenesis or development of the
spore, are the cortical layer, the medullary parenchyma, and the
nucleus, which is situated on the boundary between the two. The
differentiation of the protoplasm of the naked spore into a clearer
and firmer cortical substance, and a more turbid, granular, and
softer medullary substance, corresponds entirely with what we see
in the parenchyma cells of higher animals. These two products
of differentiation are designated by Haeckel “ exoplasm ” and
“ endoplasm.”

The exoplasm is originally a perfectly homogeneous and
structureless, colourless hyaline layer distinguishable from the
turbid granular soft protoplasm of the internal body mass, by con-
taining in its composition less water, by absence *of included
granules, and by its high independent contractility. All the mobile
appendages of the body, the cilia, bristles, spines, hairs, hooks, &c.,
are nothing but structureless extensions of this exoplasm and partici-
pate in its contractility. In this respect they entirely correspond
to the cilia and flagellae of the cells which form the ciliated
epithelium of multicellular animals.

In many Ciliata we find this cortical layer or exoplasm itself
subsequently differentiated into distinct strata. In the most highly
differentiated Ciliata four layers may be distinguished as the result
of this secondary differentiation of the exoplasm. These are :

o 2

182

Recent Progress in our Knowledge of

(1) the cuticle layer, (2) the cilia layer, (3) the myophan layer,
(4) the trichocyst layer.

The cuticle is nothing but a lifeless exudation from the surface.
In the majority of Ciliata there is no true cuticle, and in those
which possess it, it presents itself under various forms, as seen in
the thin, chitine-like, hyaline homogeneous pellicle of Paramoecium
and Trichodina, the outer elastic layer of the stem of the Vorti-
cellinae, the protective sheath of Yaginicola, the chitine-like cases of
the Tintinnodeae and Codonellidae, the beautiful lattice-like silicious
shells of the Dictyocystidae (Fig. 4), and many other shells, cases,
and shield-like protections.*

The cilia layer occurs in all Ciliata ; it lies immediately beneath
the cuticle where this is present, and the whole of the cilia and
other mobile appendages are its immediate extensions. These must
therefore perforate the cuticle or its modifications when such pro-
tective coverings exist.

The myophan layer is identical with that which most authors
describe as a true muscular layer. It has been demonstrated in
most of the Ciliata. It appears as a system of regular parallel fine
striae in the walls of the body, and in the Vorticellidae occupies also
the axis of the stem, where it forms the characteristic “stem-
muscle ” of these animals. There can be no doubt that these striae
represent contractile fibrils, which, by their contraction, effect the
various form changes of the animal. They are thus physiologically
analogous to muscles. From a morphological point of view, how-

* In the same number of the ‘ Zeitschrift,’ Haeckel (“Ueber einige neue
pelagische Infusorien”) describes some highly interesting Infusoria which spend
their lives in the open sea and are distinguished by the possession of variously
formed shells. His attention was first directed to them by finding their elegant
empty shells in the extra-capsular sarcode of Kadiolarise. These pelagic Infusoria
appear to belong to two different groups, which stand nearest to the Tintin-
nodese of Claparede and Lachmann. He designates them as Dictyocystidcc and
Codonellidce.

The family of the Dictyocystidse is based on Ehrenberg’s Dictyocysta, and is
characterized by the possession of a silicious perforated lattice-like shell so closely
resembling that of many Radiolarise, that Haeckel at first mistook it for the shell
of one of these. The shell is in all the species bell-shaped or helmet-shaped, and
the body of the animal, which is fixed to the fundus of the bell, and can be
projected far beyond its margin, has a wide funnel-shaped peristome on whose
edge are two concentric wreaths of strong cilia. He describes four species, dis-
tinguishing them by characters derived from their silicious latticed shell.

The family of the Codonellidae, based on the genus Codonella, Haeckel, is also
provided with a bell-shaped case, but this, instead of being formed of a silicious
lattice work, consists of a chitine-like organic membrane, through which silicious
particles are scattered. The family is, however, chiefly characterized by the
peculiar form of its peristome. This is funnel-shaped and provided on its margin
with a thin collar-like expansion. The free edge of this collar is serrated, and
each tooth carries a stalked lobe of a piriform shape, regarded by Haeckel as
probably an organ of touch. At some distance behind the circle of piriform lobes
is situated a ring of long, strong, whip-like cilia, which form powerful swimming
organs. The three species described are distinguished by the form of their
chitinous cases.

the Ciliate Infusoria. By G. J. Allman. 183

ever, we must regard them as only differentiated protoplasm
filaments. In the morphological conception of true muscle, its cell
nature is absolutely indispensable. The so-called muscle fibrils of
the Infusoria never show a trace of nucleus. They can be viewed
only as parts of a cell due to the differentiation of the sarcode
molecules of its protoplasm ; and as they are thus only sarcode
filaments, Haeckel designates them by the term “myophan,” as
indicating a distinction from proper muscle.

The trichocyst layer occurs also in many Infusoria, but not in
all. It is a thin stratum of the exoplasm lying immediately on the
endoplasm, and including in certain species the trichocysts. The
presence of these bodies, which possess a striking resemblance to
the thread-cells of the Coelenterata, has, as we have already seen,
been urged as an argument in favour of the multicellularity of the
Infusoria. But, as Haeckel argues, no evidence of multicellularity
can be derived from this fact. The thread-cells of the Coelenterata
are themselves the products of a cell, and we often find many of
them originating in a single formative cell quite independently of
the nucleus ; the formative cell may in this respect be compared
with the entire body of the Infusorium.

It is the endoplasm, or internal parenchyma of the Infusoria
that has given rise to the most important differences of opinion, and
in his account of this part of the Infusorium organism Haeckel
chiefly directs his criticism against the views advocated by Claparede
and Lachmann, and by Greeff.

These authors, as we have already seen, compare the Infusoria
with the Coelenterata, and regard the endoplasm not as a real part
of the body, but merely as the contents of the alimentary canal —
as a sort of food mash or chyme contained in a spacious digestive
cavity whose walls are at the same time stomach wall and body
wall, and into which the mouth leads by a short gullet. As
Haeckel urges, however, it needs only a correct conception of the
intestinal cavity throughout the animal kingdom and of its distinc-
tion from the body cavity, in order to show the untenableness of
this position. The main point of such a conception lies in the fact
that the intestinal cavity and all extensions of it (gastro- vascular
canals, &c.) are always originally clothed by the endoderm or inner
leaflet of the blastoderm, while the body cavity is always formed on
the external side of the endoderm, and between this and the
ectoderm or outer leaflet of the blastoderm. The body cavity and
intestinal cavity of animals are thus essentially different ; they
never communicate with one another, and always arise in quite
different ways.

Again, the contents of a true intestinal cavity consist only of
nutritious matter and water, in other words, of chyme ; while the
fluid which fills the body cavity is never chyme, but is always a

184

Recent Progress in our Knowledge of

liquid which has transuded through the intestinal wall, and which
may be called chyle, or blood in the wider sense of the word.

Haeckel has thus taken, I believe, the true view of the intes-
tinal and body cavities of animals. He had already advocated it in
his work on the Calcareous Sponges. It necessarily involves a
belief in the homological identity of organization between very
distant groups of the animal kingdom, a belief which all recent
embryological research has only tended to confirm.

It follows from this view that the cavity of the Coelenterata
would represent an intestinal cavity only, while a true body cavity
would be here entirely absent. This way of regarding the cavity
of the Coelenterata is at variance with the conclusions of most other
anatomists who regard the coelenterate cavity as representing a true
body cavity, or a body and intestinal cavity combined. I had
myself long entertained the generally accepted opinion that the
cavity of the Coelenterata represents a body cavity. I must, how-
ever, now give my adhesion to the doctrine here advocated by
Haeckel, and regard the proper body cavity of the higher animals
as having no representative in the Coelenterata. I believe that this
is supported both by the facts of development and by the structure
of the mature animal. Indeed, the body cavity first shows itself,
as Haeckel has pointed out, in the higher worms, and is thence
carried into the higher groups of the animal kingdom.

If such be the real nature of a true intestinal cavity and of a
true body cavity, it is plain that neither the one nor the other can
exist in the Infusoria, for there is here nothing which can be com-
pared with either the endoderm or the ectoderm.

The whole, then, of the alleged chyme of the Infusoria is
nothing more than the internal soft protoplasm of the body. It is
quite the same as in Amoeba and many other unicellular animals.

The peculiar currents which have been long noticed in the
endoplasm of many Infusoria must be placed in the same category
with the rotation of the protoplasm observed in many organic cells.
Yon Siebold, indeed, had already compared the endoplasm currents
of the Infusoria to the well-known rotation of the protoplasm in the
cells of Chara.

The presence of a mouth and anal orifice in the ciliate Infusoria
has been urged as an argument against the unicellular nature of
these organisms. The so-called mouth and anus, however, admit
of a comparison not in a morphological but only in a physiological
sense with the mouth and anus of higher animals. They are
simple lacunae in the firm exoplasm, and have, according to Haeckel,
no higher morphological value than the “ pore canals ” in the wall
of many animal and plant cells, or the niicropyle in that of many
egg-cells. Kolliker had already compared them to the excretory
canal of unicellular glands. Since, therefore, they do not admit of

the Ciliate Infusoria. By G. J. Allman. 185

being homologically identified with the orifices of the same name in
the higher animals, Haeckel proposes for them the terms “ Cxjto-
stoma ” and “ Cytopyge.”

So also the presence of a contractile vesicle and of other vacuoles
affords no solid argument against the unicellularity of the Infusoria.
The physiological significance of the contractile vesicles has been
variously interpreted. In certain cases a communication with the
exterior appears to have been demonstrated, and Haeckel regards
them as combining two different functions of nutrition, namely,
respiration and excretion. They are in all cases destitute of proper
walls, and they have been long recognized as morphologically
nothing more than lacunae filled with fluid. Regular contractile
vesicles differing in no respect from those of the ciliate Infusoria are
often found in the Flagellata and in the swarmspores of many Algae.

Besides the constant and regular contracting vacuoles, there
occur also others less constant and less regularly contracting.
These are found in the softer endoplasm, while the constant and
regularly contracting vacuoles occur for the most part in the firmer
exoplasm. One is just as much a wall-less vacuole as the other,
and the difference between them is to be traced to the difference of
consistence in the surrounding protoplasm. Haeckel regards the
less constant ones as the original form from which the others have
been phylogenetically derived, that is, by a process of inheritance
and modification through descent.

The last and most important of the parts which enter into the
formation of the Infusorium body, namely, the nucleus, is next
discussed. Viewed from a morphological point, it has been already
demonstrated that the nucleus is in all Ciliata originally a single
simple structure, resembling in this respect a true cell-nucleus.
As the Infusorium body approaches maturity we find that with its
advancing differentiation peculiar changes occur in the nucleus just
as in the rest of the protoplasm, but these changes are entirely
paralleled by differentiation phenomena which are known in other
undoubted cell-nuclei, as, for example, in the germinal vesicle of
many animals, in the nuclei of many unicellular plants, the nuclei
of many parenchyma cells of the higher plants, and the nuclei of
many nerve-cells. The mature Infusorium nucleus is often vesicle-
like, and consists of a delicate investing membrane and fine granular
contents, precisely as in the differentiated nucleus of many other
cells. In many Ciliata, if not in all, there is within the young
nucleus a dark, more refringent corpuscle, which has quite the
same relations as the nucleolus of a true cell-nucleus.

Regarded from a physiological, no less than from a morphological
point of view, the Infusorium nucleus and true cell-nucleus admit
of a close comparison with one another. It may be considered as
established by the concurrent observations of all investigators, that

186

Recent Progress in our Knowledge of

the nucleus of the Infusoria performs the function of a reproductive
organ, though the opinions entertained as to the mode in which it
thus acts are extremely divergent.

It is now admitted that in the reproduction of unicellular
organisms both in the animal and vegetable kingdom, the nucleus
takes an important part, and by its division as a primary act ushers
in the division of the rest of the protoplasm. Even in the cells
which form constituents of tissues, the part played by the nucleus
is altogether similar, its division always preceding the division of
the cell itself.

In quite a similar way does the nucleus behave in the ciliate
Infusoria. The non-sexual reproduction of the Infusoria by division
is perhaps universal. In such cases the division always begins by
the spontaneous halving of the nucleus, and this is followed by a
similar division of the surrounding protoplasm, exactly as in the
ordinary simple cell.

Another phenomenon in which the nucleus plays an important
part is named by Haeckel “ spore formation.” Under this designa-
tion he comprehends all those cases in which — the idea of a previous
fecundation being rejected— the nucleus breaks into numerous
pieces, and each of these, apparently by becoming encysted in a
portion of the protoplasm of the mother body, shapes itself into an
independent cell — a so-called germ-globule ( Keimkugel ). Now this
is a true spore — just as much so as the spores which arise quite in
the same way in unicellular plants. The whole process is to be
regarded as a case of the so-called endogenous multiplication of cells.

Most authors, however, take a different view of the nucleus.
Following Balbiani, they regard it as an ovary ; and to the frag-
ments into which it breaks up they assign the significance of eggs ;
while the so-called nucleolus, which lies outside the nucleus, is, as
we have seen, believed to be a testis in which spermatozoa are
developed for the fecundation of the eggs.

We must bear in mind, however, that this “nucleolus” has
been hitherto found in but a disproportionately small number of
species, while the spermatozoal nature of the apparent filaments
which have been noticed in it has by no means been proved ; and
we have already seen that some observed facts, such as those
adduced by Butschli, are opposed to the view which would assign to
them the nature of true spermatozoa.

As Haeckel remarks, however, even though the so-called
nucleolus be really a testis fecundating the eggs or fragments
derived from the breaking up of the nucleus, this would afford no
valid argument against the unicellularity of the Infusoria, for pre-
cisely the same sexual differentiation and reproduction are found in
unicellular plants.

It may now, then, be regarded as proved that the process by

the Ciliate Infusoria. By G. J. Allman. 187

which the body of the ciliate Infusorium attains a certain degree of
differentiation is repeated not only in other unicellular organisms,
but in many parenchyma cells both of plants and animals. The
difference, as Haeckel with much force points out, between the
differentiation process of these parenchyma cells and that of the
Infusorium body consists in the fact that in the parenchyma cells
the differentiation is a one-sided one, conditioned by the division of
labour in the organism of which they form the constituents, while
in the Infusorium it is a many-sided one related to all the different
directions in which cell-life manifests itself, and resting on a physio-
logical division of labour among the “ plastidules ” or protoplasm
molecules. In other words, the differentiation processes which in
multicellular organisms are found distributed among different cells,
are united in the single cell of the ciliate Infusorium, thus leading
to the formation of an animal very perfect in a physiological point
of view, but which morphologically does not pass the limit of a
simple cell.

In some rarer cases the Infusorium body is found to enclose
two or more nuclei, and Haeckel admits that such Infusoria must
strictly be regarded as multicellular, since the nucleus in itself
alone determines the individuality of the cell ; but these exceptional
cases have no significance for the main conception of the infusorial
organism. The multiplication of the nucleus exerts almost no in-
fluence on the rest of the organization, and such “multicellular ciliata”
are to be compared with the colony-building forms of the Acinetae,
Gregarinae, Flagellatae, and other undoubtedly unicellular organisms.

In conclusion, Haeckel considers the systematic position of the
Infusoria. That they are genuine Protozoa, having no direct
relation to either the Coelenterata or the Worms, must be now
admitted. To this result we are led in the most convincing way by
all that we know of their development. In all the animal types
which stand above the Protozoa, the multicellular organism is
developed out of the simple egg-cell by the characteristic process of
segmentation, and the cell masses so arising differentiate themselves
into two layers — the endoderm and the ectoderm, or the two
primary germ lamellae.* Resting on the fundamental homology of
these two layers in all the six higher types of the animal kingdom,
Haeckel had already t directed attention to the fact that all these
types pass in their development through one and the same remark-
able form, to which he gives the name of Gastrula, and which he
regards as the most important and significant embryonal form of
the whole animal kingdom. This gastrula consists of a multi-
cellular, usually oviform uniaxial, body enclosing a simple cavity —

* The comparison of the endoderm and ectoderm of the Coelenterata to the
two primary germ lamellae of the Vertebrata was first made by Huxley.

f ‘ Hie Kalkschw'amme,’ 1872.

188

Recent Progress in our Knowledge of

the primordial stomach or intestine cavity, which opens outward on
one pole of the axis by a simple orifice — the primordial mouth, and
whose walls are composed of two layers, the endoderm or inner
germ lamella, and the ectoderm or outer germ lamella.

This larval form has now been shown by the researches of
Haeckel, Kowalevsky, Eay Lankester, and others, to occur in
members of all the six higher primary groups of the animal king-
dom ; and Haeckel, in conformity with what he has called the
biogenetic fundamental law* — the recapitulation of ancestral forms
in the course of the development of the individual — had already in
a former work | concluded in favour of a common descent of all the
six higher types from a single unknown ancestral form which must
have been constructed essentially like the Gastrula, and to which he
gives the name of Gastrsea.

From this common descent the Protozoa alone are excluded,
these not having yet attained to the formation of germ lamellae or
of a true intestinal cavity.

He regards this difference between the development of the
Protozoa and that of all the other animal types as so important,
that he founds thereon a fundamental division of the whole animal
kingdom into two great primary sections — the Protozoa and the
Metazoa. The former never undergo segmentation, never develop
germ lamellae, and never possess a true intestinal cavity ; the latter,
which include all the other types of the animal kingdom, present a
true segmentation of the egg-cell, have all two primary germ
lamellae— endoderm and ectoderm — a true intestine formed from the
endoderm, and a true epidermis from the ectoderm ; they all pass
through the form of the gastrula, or an embryonic form capable of
being immediately deduced from it, and (hypothetically) are all
descended from a Gastraea.

The only Metazoa which in their existing condition have no
intestine are the low worm-groups — Coestoda and Acanthocephala ;
but these form only an apparent exception, for the loss of their
intestinal canal is a secondary occurrence caused by parasitism, and
Haeckel regards them as having descended from worms in which
the intestine was present.

Several years ago Haeckel united into a separate kingdom,
under the name of Protista, certain low organisms, some of which
had been previously placed among the Protozoa, while others had
been assigned to the vegetable kingdom. To this neutral group
he refers the Monera, the Flagellatae, the Catallactae, the Laby-
rinthuleae, the Micromycetae, and the Acytariae and Eadiolariae.
After the elimination of these there remain as genuine Protozoa
the Amoebinae, the Gregarinas, the Acinetae, and, above all, the
true Infusoria or Ciliata.

* ‘ Gcuerelle Morpliologie.’ f ( Die Kalkscbwammc.’

the Ciliate Infusoria. By G. J. Allman. 189

The union of the Protista into a distinct kingdom equivalent in
systematic value with the animal or vegetable kingdom, can, how-
ever, scarcely be maintained. We already know enough of some
of them to justify our assigning these to one or other of the two
generally accepted organic kingdoms ; and there can be little doubt
that, did we know the whole history of the others, and were able
to formulate the essential difference between the animal and vege-
table kingdom, these, too, would be referred without hesitation
either to the one or to the other, some passing to the former and
others to the latter. The group of the Protista is thus at best but
a provisional one, based partly on our ignorance of the structure
and life history of the beings which compose it, and partly on our
inability to assign to the animal its essential difference from the
plant. Haeckel, however, has done well in specially directing
attention to it, and in his admirable researches on many of the
organisms which he has thus grouped together he has largely
contributed to our knowledge of living forms.

I have thus dwelt at considerable length upon this important
paper of Haeckel’s, because I think that it not only brings out in a
clear light the essential features of infusorial structure and physi-
ology as demonstrated by recent research, but that it goes far to
set at rest the controversy regarding the unicellularity and multi-
cellularity of the Infusoria.

Balbiani * has quite recently published a very interesting account
of the remarkable Infusorium long ago described by 0. F. Muller
under the name of Vorticella nassuta, and more recently taken by
Stein as the type of his genus Didinium.

The animal (Fig. 5), which is somewhat barrel-shaped, with an
anterior and a posterior wreath of cilia, has one end continued into a
proboscis-like projection which carries the oral orifice on its summit,
while an anal orifice is situated on the point diametrically opposite
to this. There is a very distinct cuticle, though the rest of the
cortical layer is very thin, and can scarcely be optically distinguished
from the internal parenchyma, which exhibits manifest currents of
rotation. These flow in a continuous sheet along the walls from
the anal towards the oral side, and on arriving at the mouth turn in
towards the axis and then flow backwards along this until they
complete the circuit by once more reaching the anal side of the
body. No trichocysts are developed in the walls of the body. The
contractile vesicle is large, and is situated near the anal end; it
presents very distinct pulsations, and Balbiani is disposed to believe
in a communication between it and the exterior.

During the act of digestion a tubular cavity can be seen running
through the axis of the body, and connecting the oral and anal
* ‘Arch. Zool. Exper.,’ vol. ii.

190 The Ciliate Infusoria. By G. J. Allman.

orifices. This is regarded by Balbiani as a permanent digestive
canal. The post-oral or pharyngeal portion of this tube possesses
a very remarkable feature, namely, a longitudinal striation caused
by rigid rod-like filaments which are developed in its walls, and
which can be easily detached and isolated by pressure or by the
action of acetic acid. They then resemble some common forms of
the raphides developed in the cells of plants. The function of these
rods becomes apparent when the animal is observed in the act of
capturing its prey. The Didinium is eminently voracious and
carnivorous, and when in pursuit of other living Infusoria, such as
Paramoecium, the prey may be seen to become suddenly paralyzed
on its approach. A careful examination will then show that the
Didinium has projected against it some of its pharyngeal rods, and
to the action of these bodies the arrest of motion is attributed. A
curious cylindrical tongue-like organ is now projected from the
mouth towards the arrested prey, to which it becomes attached by
its extremity (Fig. 5 a). By the retraction of this tongue the prey
is now gradually withdrawn towards the mouth, engulphed in the
distended pharynx (Fig. 5 h), and pushed deeper and deeper info the
axial canal, where it is digested, and the effete matter ultimately
expelled through the anus.

From all this Balbiani concludes against the unicellular doc-
trine. He sees in the axial cavity a permanent alimentary canal,
and in the surrounding parenchyma a true perigastric space filled
with a liquid which corresponds with the perigastric liquid of the
Polyzoa, and of many other lower animals. He is not, however,
disposed to make too broad a generalization, and to insist on the
presence of an alimentary canal distinct from a body cavity in all
the other Infusoria. Here, however, he falls in with the views of
Claparede and Lachmann and of Greeff, and maintains that as a
rule the digestive and body cavity in the Infusoria are confounded
into a single gastro-vascular system.

Independently, however, of the untenableness of the conception
of a united digestive and body cavity, it does not appear to me that
Balbiani makes out any case against the unicellularity of the
Infusoria. He admits that except in the pharyngeal and anal
portion there is no evidence of a differentiated wall in his so-called
digestive canal, and even though it be conceded that the middle
portion of this canal constitutes a permanent cavity in the
parenchyma, it would not differ essentially from other lacunae per-
manently present in the protoplasm of many undoubtedly unicellular
organisms. It has been already remarked that a communication
between these lacunae and the external medium is paralleled in
many simple cells, and these external communications in Didinium
present no feature essentially different.

The pharynx appears to be bounded by an inflection of the

Translation of Professor Abbes Paper on tlie Microscope. 191

cortical layer, and I believe we may regard tlie rod-like corpuscles
here present as a peculiar modification of tbe trichocysts which in
many other Infusoria are developed in the cortical layer of the
body. The projectile tongue-like organ is one of the most remark-
able features of Didinium ; we must know more, however, than
Balbiani has told us of it, before we can decide on its real import.
It is not improbably a pseudopodial extension of the protoplasm.

Balbiani has followed the Didinium through the process of
transverse fission. This is preceded by the formation of two new
wreaths of cilia, between which the constriction and division take
place, each half previously to actual separation developing within it
such parts as it had lost in the act of division. The only part
which in this act becomes divided between the two resulting animals
is the nucleus. The so-called nucleolus was not seen by Balbiani ;
and though he observed two individuals in conjugation by their
opposed oral surfaces, he never witnessed anything like the forma-
tion of eggs or embryos.

I believe I have now laid before you the principal additions
which during the last few years have been made to our knowledge
of the Infusoria. But though it will be seen that the labourers in
the special field of microscopical research, to which I have confined
this address, have been neither few nor deficient in activity, it must
not be imagined that the subject has been exhausted, or that many
questions, more especially such as relate to development, do not yet
await the results of future investigations for their solution. — Anni-
versary Address to tlie Linnean Society , May 24, 1875.

III. — Extracts from Mr. H. E. Fripp’s Translation of Professor
Abbe’s Paper on the Microscope.

A careful consideration of the means at the disposition of the
optician, and a critical comparison of the difficulties serving as a
guide to the discussion of the conditions influencing them, have
led me to the conclusion that lenses and systems of lenses of
which each part has prescribed dimensions, can be executed with
an exactitude that fairly ensures correct action, and with greater
facility than any other mode of procedure offers for the fulfilment
of tbe same conditions with equally good results.

In the workshops of C. Zeiss, of Jena, the construction of
objectives, from lowest to highest power, is regulated by strict
calculation for each single part, each curve, each thickness of glass,
each degree of aperture ; so that all guesswork and “ rule of

192 Extracts from Mr. II. E. Fripp's Translation of

thumb ” is avoided. The optical constants of each piece of glass
are obtained from trial-prisms by means of the spectrometer.
Each constituent lens is ground as nearly as possible to its pre-
scribed dimensions and accurately fitted. In the highest-power
objectives only is the lens distance left variable, in order that slight
deviations from accuracy may he adjusted. And thus it has been
shown beyond dispute that a well-grounded theory, combined with
rational techni al processes, may be successfully substituted for
empirical practice in the construction of the microscope.

The fact that an amount of angular aperture, which is un-
known in any other instrument, comes here into question, renders
the accepted ideas of “ aberration ” entirely useless, and the result
of investigations which were undertaken in order to bring the
question to some issue, was the discovery that an important feature
in the optical functions of the microscope had been hitherto over-
looked. In all previous explanations or interpretations it has been
accepted as a self-understood proposition that the formation of an
image of an object in the microscope takes place in every particular,
according to the same dioptric laws by which images are formed in
the telescope, or in the camera ; and it was, therefore, tacitly pre-
mised that every function of the microscope was determined by
the geometrically traceable relations of the refracted rays of light.
A rigorous examination of the experiences upon which the tradi-
tional distinction of “defining” and “resolving” powers is founded,
has shown that the proposition is not admissible. It holds good,
indeed, fur certain cases, capable of definite verification, but for the
generality of objects, and particularly for those objects on which
the microscope is supposed to exhibit its highest quality of per-
formance, it appears that the production of microscopic images is
closely connected with a peculiar and hitherto neglected physical
process, which has its seat in and depends on the nature of the
object itself, although the measure of its effect stands in direct
dependence upon the construction of the objective. It is hence
possible not only to fix the limits of the visible, beyond which no
further resolution of structure could be expected, but also to bring
to light the fact that a microscopic image which may be entirely
free from error in itself, and therefore be supposed to represent in
all cases the true structure of an object, nevertheless does not do so
for a whole class of objects and observations.

In addition to those images of the object which are thrown off
by the lenses of the microscope, a series of associated images of the
aperture are simultaneously thrown off, which together form an
image of the outwardly projected plane of aperture. This latter
(aperture image) is thus associated with the final virtual image of
the object, and appears at the eye-point, so called, above the ocular

Professor Abbe's Paper on the Microscope. 193

where it may be examined with a lens. But the image of the
object, so far as it is produced by the objective alone, lies in or
close to the upper focal plane of the objective, where also it may be
seen by looking down the tube of the microscope with the naked
eye. These two sets of images are interconnected by common
relations, the determination of which affords a key to the solution
of questions scarcely to be approached by any other means. All
the characteristics of the object images hang together with certain
characteristics of the aperture images, and vice versa.

The principle on which is founded the study of these aperture
images leads to various results, depending for their full develop-
ment upon a principle which constitutes at the same time a law of
fruitful application throughout the whole theory of the microscope,
and which may be thus formularized.

When an objective is perfectly aplanatic for one of its focal
planes, every ray proceeding from this focus strikes the plane of
the conjugate focus at a point, whose lineal distance from the axis
is equal to the sum of the equivalent focal length of the objective
X the sum of the angle which that ray forms with the axis.

Now as this condition must be fulfilled in every correct in-
strument, both for the objective and for the whole optical part of
the microscope, the formula above given establishes a relation of
quantity between the angle of aperture of the microscope and the
lineal diameter of the aperture images above the objective and ocular.

Moreover, it is thus possible to determine, by micrometric
measurement of the position in the upper focal plane of the objec-
tive which the track of any ray occupies, the direction which it
took before entering the microscope. Consequently the aperture
images formed above the objective, when examined with a suitable
micrometer eye-piece, can be used for measurement of the diver-
gence which the rays coming from the object undergo.

In the next place, we need a more characteristic exposition of
the optical functions which, in the case of images formed under
larger angles, by rays having a great inclination to the axis, differ
greatly from the abstraction by which theory represents the action
of a set of lenses in forming an image. And such an exposition
offers itself when we can define by axioms of general validity the
mode in which an image is focussed and spread out on the focal
plane of an optical system, and distinguish th e focussing function
and the extension of image over a surface as the two principal
factors of the image-forming process, alike independent in their
abstract idea, and distinct in actual specific function. Apart from
the fact that no exhaustive analysis of a faulty image nor any
means of perfect correction are possible until such characteristic
distinction can be laid down, we have no other means of determining

194 Extracts from Mr. II. E. Fripp's Translation of

the part taken by each constituent element of a compound system
of lenses in the joint performance of the whole. When then we
define the function of the objective to be the production of a real
image, and the function of the eye-piece the amplification of this
image, — such explanation does not by any means reach the essential
principle of action of the compound microscope. This is obvious at
once when we consider that by such a definition the combination
of objective and eye-piece is made only to indicate magnifying
power, whereas on the contrary the remarkable superiority of
compound over simple microscope consists in the quality of its
performance. By the objective an image is formed and spread out
in what is an almost perfect accordance with the laws by which
images of infinitely small elements of a surface are formed. By
the eye-piece a displacement of focus is effected ; that is to say, a
change of divergence of each separate pencil of light takes place till
the divergence is almost imperceptible, and the pencils infinitely fine.

The first step or act in the image-forming process consists, not
in the production of a reversed image by the objective in front of
or within the ocular, but rather in the production of a “ virtual ”
image at an infinite distance with parallel rays. The second act
comprises the last refraction through the posterior surface of the
objective, and the several refractions taking place in the ocular
by which the image is re-formed at the distance of clear vision with
diverging visual angles. The first act answers plainly to the
function of an ordinary “ magnifying glass ” ; while the second,
taking all the changes comprised therein together, answers as
obviously to the functions of the telescope (possessing only a small
objective aperture) to which the virtual image formed by the first
process serves as “ object.”

This interlocking of objective and ocular functions — presenting
the combined effect of a magnifying glass and that of a telescope —
must be laid down as the most general and correct characteristic
of the principle upon which the compound microscope of the
present day is constructed.

From the foregoing remarks may be gathered a theory of aberra-
tions, sound and strong enough to master the difficulties which the
application of exceptionally large angles of aperture to microscope
objectives has occasioned.

It appears that the faults of image formation are separable into
two distinct classes, one comprising faults of the focussing act
(aberrations in the strictest sense), the other comprising faults
of the amplifying function. To the first class belong those
spherical and chromatic aberrations commonly studied; in the
second class must be placed a series of peculiar deviations of rays of
light from their normal course, which arise from the circumstance
that the separate rays of a homofocal beam occupying the aperture

Professor Abbes Paper on the Microscope.

195

of the lens yield unequally magnified images, according as their
inclination to the axis varies, and according also to the unequal
refrangibility of the different colours — an inequality which obtains
just as much whether the several partial images are compared with
each other, or whether within the area of each image different
positions in the field of vision are compared.

This class of anomalies affects exclusively the constitution of the
image outside the centre of the field. The perfection with which
the rays unite in the central region, and therewith the maximum
capacity of performance, depends on the contrary entirely on the
real aberration spherical and chromatic, as commonly understood.

Chromatic aberrations, as they show themselves where a large
angular aperture is used, do not depend alone on those differ-
ences of focus which affect the image-forming beams as a whole ;
but quite as much in an unavoidable inequality of coincidence of
colours of variously inclined pencils of rays within the angle of
aperture, which manifests itself in this, that an objective which
is perfectly achromatic when direct illumination is used must be
more or less over- corrected for use with oblique illumination.
Although the first-mentioned ordinary form of colour dispersion
(primary and secondary) may be entirely removed or rendered
scarcely noticeable, the last-named source of chromatism cannot
be counteracted or removed by any known material or any known
technical treatment.

Spherical aberration on a stricter examination of its causes
resolves itself into a series of independent elements which as they
increase in number, follow, with the increasing inclination of the
rays towards the axis, a more and more unequal course. An
absolute effacement is only possible theoretically for the two first
members of the series. As soon as the angular aperture exceeds a
small number of degrees, the counteraction of spherical aberration
can be effected in no other manner than by compensating the
irremovable errors of the higher elements through intentionally
introduced residual aberrations of the lower ones. The accumulation
of unavoidable deficits which this method of compensation necessarily
leaves unremedied, compels a limitation of the angle of aperture.
For angles of aperture exceeding 60 J and a fortiori for the very
large angles of modern objectives, the pre-supposition of an adequate
compensation is found in the well-known type of construction where
a plain nearly hemispherical front lens is combined with a strongly
over- corrected system of lenses. The discovery of this mode of
construction must be looked upon as the basis of every improvement
which has been introduced since. For a system of lenses made to
use in air, the limit of serviceable aperture proves to be from 105°
to 110J, beyond which it is not possible to counteract sufficiently
the spherical aberration, except by lessening the focal distance of

VOL. xiv. p

196 Extracts from Mr. E. E. Fripps Translation of

front lens from the object to a degree which makes it practically
useless. The application of the immersion principle renders it
possible to overcome spherical aberration, where even the maximum
angular aperture is used. It is in this power of using very large
angles of aperture, and also in avoiding loss of light, that the real
advantage of the immersion plan lies. It will indeed be seen from
what follows, that these two facts fully explain the undoubted
superiority of the immersion lens.

Every appliance by which the amending of spherical aberration
has been attempted — whether by correcting lenses placed above
the objective or by construction of ocular — will produce no better
result than what is already effected by changing the distance of the
front lens of the objective from those behind it. They simply
permit the existing residual aberration to be transferred — shifted
backward or forward between the centre and outside border of the
aperture — and by this means to keep, for a time, some particular
zone of the objective more or less free from aberration, at the cost
of the rest !

In an analysis of the conditions which belong to a perfect con-
struction, it becomes obvious that the factors on which correctness
of image in the centre of the field, and the maximum of good
performance depend, namely, chromatic and spherical aberration,
pertain to the functions of the objective alone, upon which no
influence of the eye-piece, however constructed, can produce any
marked effect. Arguments advanced in favour of a long tube or
of a short tube are untenable in theory; and the supposed dif-
ferences of effect have no real existence when examined under
conditions which are truly comparable. There will be found in
every objective a particular angular amplification obtainable at will
by means of length of tube and strength of ocular, which must
exactly suffice to enable any eye possessing normal capacity of
vision to recognize all the details that can possibly be delineated in
the virtual image formed by the objective. And this, which may
be termed “necessary angular amplification,” may be looked upon
as the measure of the relative perfection of the objective.

Theoretical study of the aberrations of the image-forming rays,
and practical experience involving the application of methods to be
hereinafter described, and the careful testing of a considerable
number of objectives of recent date from the best workshops on
both sides of the Channel, have led Professor Abbe to the conclu-
sion that the numerical value of “ necessary amplification ” yet
arrived at or attainable at present, is altogether much lower than
might be supposed from the liberal way in which microscopists deal
with thousands and tens of thousands. According to his experience,
the capacity of the most perfect objectives, the usual forms of illu-
mination being assumed, is exhausted with an eightfold angular

197

Professor Abbe's Paper on the Microscope.

amplification, so that every detail that can he possibly delineated by
an objective in its “ virtual ” image is certainly accessible to any eye
possessing normal vision, when the tube and ocular, taken together,
represent a telescopic magnifying power of eight times. Even this
performance is only reached in the case of low and middle power
objectives ; for when the focal length is less than i inch, the rela-
tive perfection of construction perceptibly fails, on account of the
rapidly accumulating technical difficulties, and there certainly does
not exist an objective of inch focus whose optical capacity
exceeds a fivefold angular amplification.

From all this may be gathered how utterly futile any efforts to
obtain disproportionately high amplifications by means of specially
constructed eye-pieces must prove ; and, as regards any expectation
of exalting the performance of the instrument by further shortening
of the focal length of the objective, there stands in the way one
objection, which, in the present state of our knowledge, is absolute
and insuperable — namely, that the imperfections resulting from
residual aberrations and defective technical manipulation increase
with every addition of magnifying power. This form of diffraction,
likewise, turns the image of each point in an object into a dispersive
circle of greater or less diameter ; but the resulting diminution of
optical capacity, while scarcely noticeable in objectives of moderate
power, compared with the effect of residual aberrations, becomes
very serious with the higher powers. Assuming the magnitude of
angle of aperture 180° in air, which cannot be exceeded beyond a
few degrees, even by immersion systems, we find, e. g. for an
amplification of 1000, the diameter = sV inch, and for amplifica-
tion of 5000 = 2Ҥw inch, without reference to the mode in which
the amplification is obtained (through objective and ocular). And
if we would know what conditions are involved in such amplifica-
tions — as, for instance, 5000 fold — we have only to make a
puncture of Aso inch diameter with a needle in a card or piece of
tinfoil, and through this opening to look at some brightly illumi-
nated object, which has well-defined edges (e. g. a candle flame), and
we shall have before our eye of what must be the appearance of the
outlines of a microscopic object magnified 5000 times, even if the
microscope itself were absolutely perfect, the diffractive effect
excepted.*

Taking all these circumstances into consideration, it must be
concluded that no material exaltation of the absolute power of the
microscope, beyond what is attainable at present with objectives of
aV inch focal length, is to be expected in the future, either by
shortening of focus or by further improvement of construction.
And as there exists at this moment no microscope whose serviceable

* Due to smallness of aperture of a minute lens, and to be carefully distin-
guished from the diffraction which is caused by the structure of objects.

P 2

198 Extracts from Mr. II. E. Fripps Translation of

magnifying power reaches even to 4000, so will there he none in
the future. On the contrary, the facts just stated show that
amplifications of less than half 4000 — such as are readily obtained
with objectives of oV inch, and seem really serviceable — are never-
theless not available in practice. The final inference from these
data is that improvement of the microscope should no longer he
sought for by aiming at still higher magnifying power and amplifi-
cation, hut rather at a more correct performance of the middle
and moderately high powers. It will he a real advance of the
optician’s art, and of infinite service to the scientific use of the
microscope, when we succeed in accomplishing with objectives of
Jth and |th what is now only attained with much higher powers.
Such an aim is within the range of what is possible.

In the account of Professor Abbe’s researches, to be hereafter
published, new and exact methods will he given by which every
determinable point in the construction of the microscope, e. g. focal
length of each lens, angle of aperture, character and limits of
objective and ocular functions may be empirically ascertained ; and.
in addition to this, a mode of procedure described which renders it
possible, with very simple means, to examine in instruments already
made, every fault of definition of image, and thus to determine their
relative excellence. The methods commonly recommended for
testing the state of spherical and chromatic correction of the
objective are not adequate to the actual requirements of the case,
and quite fail to explain the true character of the aberrations.

The principle upon which the mode of proceeding to which
reference has been made above, may be here generally indicated.
As test-object, a preparation is used which presents only sharply
outlined black and white lines alternating with each other, and
lying in the same plane, so that no deviation can occur in the course
of the rays transmitted through it. A preparation of this kind,
sufficiently perfect for all practical purposes, may be made by ruling
groups of lines, with the aid of a dividing machine, on the metallic
film of silver or gold fixed by known methods on glass, and having
no greater thickness than a fractional part of a micro-millimeter
( 1 micro-mm. = o inch). Covering glasses of various thicknesses
(accurately measured) are ruled on their under surfaces with lines
to tsW to the inch, and cemented on a glass slide with
balsam, one beside the other. A preparation of this kind serves
for the highest as well as lowest powers. The illumination must
lie such that light may he reflected simultaneously from several
sides upon the object, and means provided for regulating at will the
course of any pencil entering within the angle of aperture of the
objective to be tested.

The testing process has for its aim to view the co-operation of
every zone of the aperture, whether central or peripheral, and yet,

Professor Abbe’s Paper on the Microscope. 199

at the same time, to be able to distinguish and recognize the images
which each zone delivers separately. For this purpose the illumi-
nation is so regulated that every zone of the aperture shall be
represented in the image formed at the upper focal plane by tracks
of the entering pencils of light, yet so that for each zone a small
streak only of light he let in, and that the tracks be kept as widely
apart from each other as possible. If an objective be absolutely
perfect, all these images should blend with one setting of focus into
a single, clear, colourless picture.

A test image of this kind at once lays hare in all particulars the
whole state of correction of the microscope, With the aid which
theory offers to the diagnosis of the various aberrations, a com-
parison of the coloured borders of the separate partial images, and
an examination of their lateral separation and their differences of
level, as well in the middle as in the peripheral zones of the entire
field, suffice for an accurate definition of the nature and amount of
the several errors of correction, each of them appearing in its own
primary form.

Assuming the theoretical knowledge and practical experience
necessary tb carry out such an inquiry properly, and to estimate
its results correctly, the mode of procedure above described affords
so exhaustive an analysis of the qualities of an objective, that when,
in addition, its focal length and angle of aperture are ascertained,
its whole capacity of performance may he determined beforehand.
Whoever has once examined in this manner even good objectives
which have proved to be excellent in practice, will be as little
disposed to accept childish assertions of their perfectness as to
advance on his part absurd pretensions which no one has yet made
good.

That the performance of the microscope does not always
depend solely on the geometrical perfection of the image, but also,
in addition to this, in certain classes of objects, upon amount of
angular aperture, is a fact long recognized. The exact significance
of this fact has nevertheless remained as problematical as the exact
nature of the quality of “ resolving ” or discriminating power. It
remained a question, What value might be assigned to the quality
thus related with angular aperture, and does its significance extend
any farther than to certain cases in which shade effects were sup-
posed to be produced by oblique illumination ?

In the endeavour to establish a theoretical basis for the con-
struction of the microscope, it was a matter of the first importance
to define the exact function of angular aperture in the normal per-
formance of the microscope, lest I should fall into a misdirection of
my labours towards aims of very problematical worth.

As, then, it was important above all things to ascertain more
exactly than has been hitherto set forth the actual facts respecting

200 Extracts from Mr. H. E. Fripp's Translation of

the operation and effect of angular aperture, I endeavoured to deter-
mine by experiment in what cases a distinct advantage resulted from
larger angular aperture, and in what cases no such advantage could be
perceived. For this purpose a series of objectives, differing widely
in focal length and angular aperture, were constructed, according
to my calculations, and their accuracy tested, so as to afford a
certainty of correctness. The test-objects employed included pre-
pared insect scales of various kinds, diatom valves, striped muscle
fibre, diamond-ruled lines on glass, groups of lines on silvered glass,
fine and coarse powdered substances, and, besides these, the minute
optical images of natural objects (lattice bars, wire-net) obtained
by means of air-bubbles, or, preferably, by objectives of short focus,
fitted to the stage of the microscope.

These experiments yielded the following results :

(i.) So long as the angle of aperture remains within such limits
that no noticeable diminution of sharpness of image results from its
diffraction effect, no sensible improvement in the delineation of the
outlines of the object takes place, provided these parts are not of
less size than ^sVo inch.

(ii.) On the other band, the difference is wholly in favour of
the larger aperture for every object which yields details minuter
than the limits above given ; and this quite irrespective of the
question whether such details are due to unevenness of surface or
to unequal transparency in an infinitely thin layer, or whether the
detail takes the form of stria tion, granulation, trellis work, or images
of natural objects reflected from bubbles or produced by refraction
of lenses.

(iii.) The smaller the linear dimension of such details, so much
the larger must be the angle of aperture of the objective, if they
are to be made out with any definite kind of illumination, e. g.
whether purely central or very oblique : and this irrespective of
the more or less marked character of the delineation and of the
focal length and necessary amplifying power of the objective.

(iv.) When the detail in the real object appears in the form of
striation, groups of fines, &c., a given angular aperture always
reaches much finer details with oblique than direct illuminations,
and this irrespective of the circumstance that the constitution of the
object admits or excludes the possibility of shade effects.

(v.) A structure of the supposed kind, which is not revealed by
an objective used with direct illumination, will not be rendered
visible by inclining the object itself at any angle to the axis of the
microscope, even when, lying at right angles with the axis, it is
perfectly resolved by oblique illuminations. Resolution, however,
follows at once when the incident light is directed perpendicularly
to the plane of the object, as it lies inclined to the axis. Hence
the increased effect of oblique illumination depends solely on the

201

Professor Abbe's Paper on the Microscope.

inclination of the rays towards the axis of the instrument, and not
upon the oblique incidence of light on the object.*

The facts here brought forward show, on the one hand, the
reality of a special optical quality, directly related with the angular
aperture of the objective, yet independent of any special perfection
or amplifying power possessed by it, and also show it to he a
“ resolving ” power or capacity of separating minute detail, conform-
ably with the literal sense of the term employed. On the other
hand, they show unequivocally that the delineation of images of
minute details of structure must take place under conditions essen-
tially different from those under which the contour outlines of
larger parts are formed. In all cases where a “ resolving ” power
of this kind is in operation, the reunion of rays proceeding from
the several points of the object in the focal plane of the image is
most certainly not to be accounted an adequate explanation of the
images of such details of the object, for on such a supposition the
differences would remain absolutely inexplicable. The result, then,
of this preliminary study is to give the following form to the
inquiry, namely, to find out the special causes outside the micro-
scope which operate in the formation of images of small structural
details, and then to determine individually the mode and manner
of their intervention.

* Vide Wenham, in ‘ Monthly Microscopical Journal,’ April 1, “ On a Method
of obtaining Oblique Vision of Surface of Structure,” &c. The optical principle
enunciated by Mr. Wenham is totally irreconcilable with Professor Abbe’s theory
and experimental investigations.

( To be continued.')

( 202 )

PEOGEESS OF MICEOSCOPICAL SCIENCE.

Bony Tissue , not prepared Plain, but with Aniline Dye. — M. Ranvier
—no mean authority on the subject of bone tissue — recommends the
adoption of the following method in the ‘ Archives de Physiologie,’
which is abstracted by the ‘ Medical Record ’ : A portion of the shaft
of a long bone is procured, and immediately on removal from the body
is plunged into water. It is allowed to macerate in this for the space
of a year ; the water in the mean time being repeatedly changed. At
the end of that time the bone will be found to have become as white
as ivory, and quite free from any adhering tissue. The object of im-
mediately plunging the bone in water is to prevent the infiltration of
the canals and substance of the bone with fat.

When the bone is thoroughly macerated, sections of it are made
with a saw. These sections are ground down on pumice-stone, and
finally polished on a harder material. In order to remove the pow-
dered fragments of bone which have been ground off from the canals
and lacunae on the surface, it is sufficient to scrape the section with a
scalpel. It is then placed in a warm solution of the aniline, and
allowed to remain there for two hours, and afterwards dried on a
water-bath.

The section is next rubbed on a hone, moistened with a 2 per cent,
solution of common salt. It is then washed in this solution, and per-
manently mounted in a mixture of equal parts of the solution of salt
and glycerine.

In objects prepared in the above manner three important facts, not
previously noticed, may be observed.

The first is the existence of lacunae or corpuscles, consisting of a
simple slit, not much larger than a canaliculus. The fact of their
being lacuna) is proved by the relation in which they stand to the
canaliculi, which is precisely the same as that of other lacunae. The
name given to these fine atrophied corpuscles or lacunfe is confluents
lacunaries. They are lacunae either partially or completely atrophied.
This observation bears out the theory of the disappearance of the
lacunae with age. But this disappearance is not due to the lacunae
being filled up with fresh bone, but rather to a process of atrophy.

The second interesting fact rendered clear by this method is, that
the canaliculi which are given off from the outer sides of the external
lacunae of each Haversian system proceed for a short distance as though
they were going to inosculate with a neighbouring system. They then
turn on themselves, and inosculate with other canals belonging to their
own system. These are called canalicules recurrents. From this fact
we may conclude that each Haversian system forms a complete struc-
ture by itself, and represents the elementary bone.

The third fact relates to the structure which intervenes between
the Haversian system. In transverse section there may be observed,
in these islets of bone, certain small circles which represent the fibres
of Sharpey divided transversely. These circles are only to be seen in

PROGRESS OF MICROSCOPICAL SCIENCE.

203

the intermediate structure, never in the Haversian system. This fact
proves that the substance in these localities is developed from the
periosteum. The relation which the corpuscles and canaliculi bear to
the fibres of Sharpey may be briefly stated as follows. The corpuscles
are placed in the angles formed by the intersection of these fibres.
The canaliculi surround the fibres, but do not pass through them.
This last fact, taken into consideration with that of the recurrent
canaliculi of the Haversian system, proves that the canaliculi are
spaces left in the substance of the bone at the time of its develop-
ment, and not fissures made during the preparation of the section.

Fecundation ofThecaspore Fungi. — The ‘Academy ’ (Jidy 10, 1875),
in its occasional and very interesting microscopical notes, gives the
following account of a paper in the ‘ Comptes Rendus,’ to which the
author’s name is not appended. It gives a description of phenomena
of copulation observed in Hypomyces aster oplehor us, and Dotliidia
Bobertioni, the latter parasitic on Geranium Bobertianum (Herb
Robert). The generative process corresponds with what had been
previously observed by MM. de Bary, Woronin, andTulasne, in other
thecaspores. The report observes that “ these interesting facts gene-
ralize the phenomena already observed in a very different group, and
help to confirm the opinion that the fecundation of thecaspore fungi
is effected in the mycelium, and thus precedes the formation of the
organs that form the spores.” Speaking of spermatia, the report con-
tinues : “ It is known that M. Tulasne has given this name to bodies
of very great tenuity developing regularly on the surface of many
Thecaspores and Uredines, or in special conceptacles, and which have
been considered as concerned in the work of fecundation.” The dis-
covery of the fecundation of these fungi by organs springing from the
mycelium — a discovery to which M. Tulasne contributed — rendered
very problematical the fecundating action attributed to the spermatia.
The author of the memoir before us shows that the spermatia can
germinate when placed under suitable conditions, which, for hypo-
xylous species, consist in adding to water a little tannin and sugar,
and leaving them in contact with air. The spermatia of Uredines
germinate in pure water, but their development appears to be very
different from that of the hypoxylous sorts.

Development of the European Lobster. — A writer in a recent number
of ‘ Silliman’s American Journal,’ whom we take to be Mr. Samuel H.
Scudder, but whose signature is S. I. S., writes as follows on the above
subject : Dr. Sars has also recently published a paper of twenty-seven
pages, illustrated by two autographic plates, on the post-embryonal
development of the European lobster ( Homarus vulgaris, Edwards).
He describes and figures in detail the three larval stages correspond-
ing precisely with the first three stages which I have described in the
American lobster. Dr. Sars did not receive my papers until after a
part of his memoir was printed, so that his investigations were wholly
independent. In a short appendix, Dr. Sars calls attention to the re-
markable agreement in the results at which we had each arrived, and
to the excellent opportunity afforded for a careful comparison of the

204

PROGRESS OF MICROSCOPICAL SCIENCE.

early stages of these two closely allied species. Although the corre-
sponding stages agree so closely in form and structure, they are from
the first readily distinguishable by well-marked specific differences in
the form and armature of the appendages. In fact, the differences appear
greater in the larval stages than in the adults. Dr. Stars was not able
to trace the development beyond the third stage, which he had at first
supposed could not be the last stage of the larva, but after compa-
rison with the latter stage of the American lobster, he regards it as
quite probably the last true larval stage.

Comparative Anatomy of the Placenta. — Professor Turner, F.E.S.,
who has been lecturing on this subject before the Royal College of
Surgeons, devoted his second lecture to a consideration of the changes
which occur in the uterine mucous membrane during pregnancy. He
pointed out that as soon as the ovum was received into the uterus the
mucous membrane swelled. The epithelium often, though not always,
loses its columnar form, and the cells multiply in order to cover the
increased surface. The subepithelial tissue increases enormously, which
is due to the multiplication and development of the corpuscles already
stated to be abundantly distributed through its tissue. The tubular
branched glands are separated to a much greater distance from each
other in consequence of the growth of the subepithelial tissue. They
are augmented in size. The whole membrane becomes much more
vascular. On its surface pit-like depressions may be seen, which were
formerly thought to be the enlarged mouths of the glands, but which
the Professor himself had ascertained to be new-formed pits or crypts
in the interglandular tissue. The relation of these pits he next pro-
ceeded carefully to describe, taking the diffused form of placenta of
the pig, which is the simplest form of placenta, as an example.

When the mucous membrane of the pig is examined after the entry
of the ovum, it was found to present a series of folds, which, however,
like the rug* of the stomach, are only preparatory to its great subse-
quent dilatation, since they disappear in the distended state. On ex-
amination with a hand lens fine furrows are seen, which correspond to
the ridges on the chorion. Also a series of spots corresponding to the
spots of the chorion ; these spots are feebly vascular. Between these
are a number of crypts, which are highly vascular. The glands in
the pig are tubular and much branched ; they open upon circumscribed
areas free from crypts ; and hence, which is a very important point,
there is no relation between the glands and the crypts. The crypts
are lined by columnar and probably by ciliated columnar epithelium.
The villi of the chorion are received into the crypts, and not into the
mouths of the glands. The secretion of the glands is not brought into
direct relation with the villi of the foetus.

In the mare the mucous membrane is also thrown into folds, and
there are here also polygonal areas with intervening ridges. Each
area presents a pattern formed by numerous crypts ; the walls of the
crypts are highly vascular, the ridges between the collections of crypts
are but feebly vascular ; the glands here, again, do not open into the
crypts, but irregularly upon the ridges ; the crypts, therefore, as in
the pig, which receive the villi, are interglandular, and are not the

PROGRESS OF MICROSCOPICAL SCIENCE.

205

glands themselves. Professor Turner has not satisfied himself that
the cells in the crypts are ciliated, but they are more or less columnar,
swollen, and sometimes binucleated. In the cetacean, Orca gladiator,
which Professor Turner has studied specially, the ridges are tolerably
regularly arranged in parallel rows. But the crypts exist both on the
ridges and on the furrows, and Professor Turner at first thought the
glands opened into some of the crypts, and it seemed as if the crypts were
only the enlarged mouths of the glands, but he soon found that, as the
crypts are pretty uniformly distributed, the glands must open into some
of them, and that here again the crypts cannot be regarded as the
mouths of the glands.

Professor Turner observed that some of these points had been
clearly seen by Eschricht in the porpoise many years ago, the crypts
being named by him cellulae, and the bare comparatively non- vascular
spots areolae.

The cotyledonary placenta of the ruminants was then considered.
It was shown that here also the crypts, with the intercryptal sub-
stance, enlarged immensely at certain spots, forming the cotyledons,
whilst the glands were pushed aside, as it were, and the foetal villi did
not penetrate into their interior.

Effect of Curare on the Emigration White of Blood-globules. — An
anonymous writer says that if the blood of a frog poisoned by curare
be examined on the second or third day of immobility, it is found to
contain no leucocytes ; these, however, reappear as the power of
voluntary movement is restored, and gradually resume their customary
proportion to the red corpuscles. This observation was made by
Drozdoff, who attributes the phenomenon to a specific poisonous
action of the drug on the colourless corpuscles; he found that the
addition of a minute proportion of curare to a drop of blood, after its
removal from the body, speedily arrested the amoeboid movements of
the leucocytes, and rendered their protoplasm granular. Tarchanoff,
working under Kanvier’s direction,* repeated Drozdoff’ s experiments,
the results of which he partially confirms, while explaining them in a
very different way. The gradual disappearance of leucocytes from
the blood of the curarized frog is an undoubted fact ; but the pheno-
menon cannot be ascribed to any specific action of curare upon
protoplasm. The addition of curare to drops of blood in the moist
chamber yielded results which were by no means constant ; some
samples of the drug speedily destroying the colourless corpuscles,
while others appeared in no way to influence their vitality. What
then is the cause of their disappearance (which is never really abso-
lute) from the circulating fluid ? They migrate into the perivascular
spaces, and accumulate in the lymphatic sacs and serous cavities.
This emigration is associated with a considerable transudation of the
fluid constituents of the plasma, so that, pari passu with its increasing
poverty in leucocytes, the blood is observed to contain an abnormally
large proportion of red disks. Both processes may be accounted
for by the paralyzing effect of the drug upon the vasomotor nerves ;

* ‘Archives de Physiologie,’ Janvier-Fe'vrier, 1875.

206

PROGRESS OF MICROSCOPICAL SCIENCE.

the arterioles are everywhere dilated, the intravascular tension
lowered, and the blood-current uniformly retarded. Exactly similar
phenomena may he produced by destroying the cerehro-spinal axis,
and so paralyzing the vasomotor nerves. But why does the lymph,
after its escape from the vessels, accumulate in the serous and
lymphatic cavities ? Why does it not make its way back into the
current of the circulation ? For this there are two reasons : first, the
paralysis of the voluntary muscles, whose contractions are largely
instrumental in the onward propulsion of the lymph ; secondly, the
arrest of the lymphatic hearts. As the effects of the poison pass off,
these causes cease to operate, and the exuded constituents of the
blood return to their normal home within the vessels.

Cause of a Disease in Cabbages. — A recent writer says that whilst
seeking for the cause of the swellings which occur so often in the roots
of the cabbage tribe and injure their growth, Herr Woronin found a
fungus in the parenchyme cells. He describes it, when young, as a
plasmic body with a lively motion. After a time it settles down and
grows ; “ the granules of the plasma collect into small bodies lying
close together, and form a round mass covered with a membrane.”
These are spore-cells, and as the plant rots, “ zoospores or small
amceb* escape from the fungus, and, penetrating young sound rootlets,
cause fresh plasmic bodies to be formed in their paren chyme cells.”
When seed from healthy plants was sown in soil containing the
decaying matter of sick plants, and wetted with water containing the
fungus spores, the fresh plants were attacked, and their roots exhibited
the characteristic swellings. M. Woronin supposes this fungus to
belong to the Mucedines or the “ Chytrideneen.” *

The Germination of Ohara. — The ‘ Academy ’ (August 28) says that
in the 4 Botanische Zeitung ’ Professor de Bary has recently contri-
buted an exhaustive article on the germination of the Characece in
general. In the main the results of his researches confirm Pring-
sheim’s views, as published in 1864, f especially with regard to the
nature of the pro-embryo, which is not a direct prolongation of the
oospore, but the outgrowth of one of two divisions of the latter
equal in all respects at the time of partition, though subsequently
exhibiting a different development. The direction and nature of the
earlier divisions, formation of nodes, appearance and development of
adventitious pro-embryos and roots, &c., are fully described and
illustrated. But it is impossible to epitomise an article of this
nature, or rather the article itself is unintelligible without the accom-
panying figures. It contains, however, some additional notes on
parthenogenesis in the genus Chara, which, the author asserts, is
established beyond doubt.

* “Der Naturforscher,’' No. 24, 1875, cited from ‘Botanische Zeitung,’ 1875,
No. 20.

f ‘ Jahrbuch fur Wissensckaftliclie Botanik.’

( 207 )

NOTES AND MEMORANDA.

Powell and Lealand’s new g inch. — The ‘Academy,’ which oc-
casionally has valuable microscopical notes, states that the new |4h of
Powell and Lealand is a decided advance in accuracy of correction,
and if, as there is some reason to expect, the glass-makers can suc-
ceed in producing a material rivalling the refracting powers of the
diamond, still further progress would be within the reach of skilful
optical artists. An aluminium glass is sjtoken of as likely to fulfil
the requisite conditions.

Glass ruby-tinted with Gold, seen with the Micro-spectroscope.

— The writer of the microscopical paper above mentioned says that his
attention has been called by Mr. Lettsom to the remarkable spectrum
afforded by glass ruby-tinted with gold. In a slide prepared by him,
kindly forwarded to us, we find the luminous part of the green and
blue darkly clouded by a very thin slice of the glass while the red
and violet portions of the spectrum remain clear. At night, with the
micro-spectroscope and a paraffin lamp, the cloudy band has a peculiar
red tint, well seen if the lamp is screened so that little light can
reach the eye except what passes through the spectroscope.

Microscopical Soiree at the British Association. — This is said
by a contemporary to have been a very great success, and the Asso-
ciation owes its hearty thanks to Messrs. W. Tedder and J. W. Morris,
the secretaries respectively of the Bristol and Bath Microscopical
Societies, and to the members of those societies. A bold idea was well
carried out, viz. that of exhibiting chiefly living objects. The 110
microscopes were arranged in classified divisions, devoted to Crustacea,
Arachnidans, Insecta, marine and fresh-water fauna, ciliary action,
vertebrate circulation, vegetable circulation, fertilization of flowers,
Cryptogamia, micro-spectroscopes, &c. The idea of practically illus-
trating Sir John Lubbock’s ‘ Fertilization of Flowers by Insects ’ was
novel, and so far carried out as to give a vivid idea of the processes to
those who were previously unfamiliar with them. The geological
division included an exhibition of the perennial Eozoon canadense,
which must be exhibited again and again to live down the hostility to
its animal nature. Altogether the exhibition was a great evidence of
scientific enthusiasm, which had led many ardent students to make
special dredging and fishing expeditions both in inland and marine
waters.

Anatomical Micro-photographs. — At the meeting of the British
Association, Mr. H. B. Brady, F.R.S., exhibited a series of photo-
graphs, chiefly from physiological and pathological preparations,
taken by a new and simple process devised by Mr. Hugh T. Bowman,
of Newcastle. The apparatus was also shown, and described to consist
of a simple mirror of spectrum metal placed at an angle of 45° in
front of the eye-piece of the microscope, directed downwards. The
image was received upon a collodion plate set in the frame of a

208

CORRESPONDENCE.

common photographic camera, and photographs taken in the usual
way. About eleven seconds was stated to he sufficient exposure for
the purpose.

Professor Abbe’s new Book on Optical Instruments. — We are
informed that Professor Abbe intends to give his papers on the
microscope — one of which appears in print in the present number
of this Journal — in the form of a complete book “ on the theory of
optical instruments.”

CORRESPONDENCE.

Observations on Mr. Branwell’s Letter.

To the Editor of the ‘ Monthly Microscopical Journal

Boston, Mass., U.S.A., August 10, 1875.

Mr. Editor, — I have been much interested in the proposition by
Mr. R. Branwell in the August number of this Journal. Some micro-
scopists may at once accept his dictum that the opinions of certain
persons named settle at once and for ever a certain disputed point ;
most others equally as competent may not accept that dictum, and the
pages of that same number of the Journal afford ample evidence of
the fact.

Mr. Branwell says, “ The finest glass ever made would have but a
limited sale, and probably would be condemned by the public because
it could not perform on a diatom so well as other known glasses of
even moderate excellence.”

I challenge Mr. Branwell’s theory. I claim that the “ finest glass
ever made ” or yet to be made will perform best on the diatom, and I
maintain the converse proposition that the glass that will not perform
best on the diatom is not the best for all other work. These pro-
positions I am ready to prove by glass that are the best. No opinion
to the contrary can be of any value unless the parties giving the
opinion have tried them.

It is time the humbug was exposed and done with, that glasses fit
for the study of diatoms are only fit for them. The fact is, the
diatoms are the best objects in nature for the study of microscope
objectives.

Charles Stodder.

[Mr. Stodder, if not remarkably clear in some of his utterances, is
at least bold in his expression of opinion. We fear, however, that
those who have most studied microscopic anatomy will not accept his
propositions. — Ed. ‘ M. M. J.’J

CORRESPONDENCE.

209

An Error in Mr. Dod’s last Letter.

To the Editor of the ‘ Monthly Microscopical Journal

Memphis, Tenn., U.S.A., August 17, 1875.

Dear Sir, — Please do me the favour to correct a typographical
error in my note published in the August number of £ M. M. J.,’
p. 100. The Tolies’ “ four-system ” glass of ^th of an inch, should
be -j^tli of an inch, only.

Yours truly,

Albert F. Dod.

A Query as to the Luminous Field in the Immersion Lens.

To the Editor of the ‘ Monthly Microscopical Journal.'1

Boston, August 24, 1875.

Sir, — Your correspondent, Mr. Mayall, in the ‘ M. M. J.,’ p. 96,
alluding to the testimony of Mr. Wenham’s Reflex Illuminator as
deciding the “ aperture question,” says : “ If he will try the experi-
ment on Moller’s Probe-Platte with the Reflex Illuminator and a
high-angled immersion lens, he will see a luminous field ; whereas,
with a pneumo-lens he obtains a dark field. Whence comes the
luminous field in the immersion lens if not from its having the power
to collect rays which are totally reflected when the pneumo-lens is
used ?”

I beg to suggest that this is not quite so definite a statement as is
needed to make the conditions of the case clear. Will Mr. Mayall
tell us what is the very least angle of such “ a high-angled immersion
lens ” as will give the effects he names ; that is to say, of a dark field
when dry (thus a “ pneumo-lens ”), and a luminous field when “ wet,”
and becoming thus an immersion lens ? I hope for an explicit state-
ment of the fact.

Yours respectfully,

R. B. Tolles.

English and Foreign Preparers of Microscopic Specimens.

To the Editor of the ‘ Monthly Microscopical Journal

August 25, 1875.

Sir, — Although in some instances foreign preparers supersede the
English, it is but fair to state that the English excel in several
instances the foreign preparers.

Among the English preparers, Barnett, Cole, Enoch, Norman, and
Amos Topping take the lead in their specialities, although several
amateur preparers produce preparations of the highest quality.
Among foreign preparers, Bourgogne’s (Charles, Eugene, and J.

210

CORRESPONDENCE.

Pere) preparations are well known for tlieir great excellence, anti
several of them are not obtainable, of equal perfection, from any other
source. C. Rodig’s botanical preparations, above all the sections of
Fungi in situ, are well worth recommending — they are superb.
J. D. M oiler’s Platten are well known, and they are undoubtedly
marvels of manipulative skill. H. Dalton’s arranged scales are
deservedly admired as “ pretty and showy ” preparations. Some
American microscopic specimens are extremely well mounted.

Moller has recently increased some of his prices to an enormous
extent, although the quality of his productions has, to say the least,
remained stationary. Several species of diatoms quoted in his (M.’s)
catalogue at prices ranging from 2s. to 6s. can be obtained here from
the different opticians at from Is. to 2s. each, according to the per-
fection of the specimens and the hands in which they are. Moller may
be looked upon by some as an authority on Diatomacece, but according
to Mr. Hickie (£ M. M. J.,’ No. lxxix., p. 34), “ wrong naming seems to
be his speciality,” and authenticity is not, therefore, the inducement
to pay the increased prices for M.’s preparations.

Since this increase of prices has taken place, Moller generously
offers to the microscopical world to divulge his procedure to prepare
Diatomacese, for a corresponding indemnification, by publishing a
little work, with illustrations, at the moderate price of 32s.

In such a state of things, one must look for some source whence
reliable preparations, of excellent quality, and moderate prices, may
be obtained.

In regard to the English preparers, Cole and Son, of Liverpool,
the well-known preparers of Diatomacese, have recently extended their
productions to series of pathological and physiological preparations,
which are highly recommended by several authorities.

Among the physiological series will be found excellent pre-
parations of the so much looked for injected human cerebellum and
cerebrum, and many other first-class injections, which will be, no
doubt, of great interest both to the professional and to the amateur
microscopist.

Cole and Son have also produced lately series of Diatomaceai,
some of the specimens being of great rarity, mounted in their usual
clean style, at very moderate prices.

When specimens like the above are met with, there should be no
fear, when calling attention to them, that the idea of “ puffing ” may
be, for a moment, justly entertained.

I bring the above before your readers, believing that several of
them do not wish to pay fancy prices, and therefore deprive them-
selves from adding certain specimens (which they would have bought
at reasonable prices) to their cabinets.

I am, Sir, your obedient servant,

A. de Souza Guimaraens.

CORRESPONDENCE.

211

On Improvements in Illumination.

To the Editor of the ‘ Monthly Microscopical Journal.'

27, Montague Street, Edinburgh,
August 30, 1875.

Sir, — Whether the present controversy on angular aperture and
the rival merits of English and foreign lenses may, or may not, result
in enlarging the defects while minimizing the excellences of our
objectives, or whether the differences between the dot-showers and the
Yalentin-knife men, where the one party looks for glasses having only
one definite focal plane, and the other for such as have half-a-dozen
planes at once, are likely to be adjusted by a prize glass to be con-
structed under the superintendence of the “ R. M. S.,” which shall in
some mysterious way combine both those idiosyncrasies, is a question
I care not to meddle with. My purpose here is, not to obtrude
opinions on others, but rather to seek advice and assistance in a
matter, the importance of which is incontrovertible. I am alluding
to improvements in illumination.

There are, of course, other points in which I should like to see
improvement, or, at least, the liberty of choice afforded us ; for
instance, I should like to see some portion of that careful correction,
which is said to be lavished on our objectives, extended also to eye-
pieces ; and some contrivance hit upon to enable the diaphragm with
its iris arrangement, instead of being a fixture, as at present, to be
smoothly traversed from left to right,* at right angles to the axis of
the tube, so as to combine oblique illumination with complete exclusion
of all extraneous rays, and this without adding materially to the
thickness of the stage.

But these, I suppose, are things rather to be hoped for than
expected.

With regard to illumination, though I have hunted through divers
works to find what I wanted, my search has hitherto been fruitless.
They either recommend specialities of limited application, or their ex-
periments are like those of Mejnour in Bulwer’s ‘ Zanoni,’ — successful,
it is true, in their own hands, but with the finishing touch concealed.

Many persons have a strong prejudice against all sources of
illumination with which glass, — especially quicksilvered glass, — is
mixed up, as invariably introducing disturbing elements, which it is
the worker’s business immediately to get rid of. Compare Dr. Pigott’s
remarks in the ‘ M. M. J.,’ vol. xiii., pp. 152, 177. Therefore I have
been thinking whether some improvement in this direction might not
be effected by substituting for our present concave mirror of quick-
silvered glass, — at least as an optional alternative, — a concave surface
of some material perfectly white, and yet perfectly free from glistening,
the surface to be brought to a state of absolute smoothness. As polished
silver would probably be quite as offensive as our present arrangement,
it occurred to me that the surface might be covered with white enamel,

* In the better German microscopes the diaphragm certainly does slide in
on the right side (cf. ‘Nageli u. Schwendener,’ p. 93); but there is nothing
answering to the above requirements, — at least I have seen nothing.

VOL. XIV.

Q

212

CORRESPONDENCE.

after the manner of watch faces, though I am doubtful how far such
a material would be susceptible of polish : but upon this point I would
fain have the opinion of others. The amount of polish required and
the difficulties in the way may be inferred from the following extract
from Dr. Miller’s ‘Chemical Physics’ (5th ed., p. 161): “Bodies
in general do not possess surfaces actually flat. To common observa-
tion they may ho flat ; but, when optically examined, their surface is
found to consist of an indefinite number of minute planes inclined to
each other at all possible angles, and therefore receiving and reflecting
light in all possible directions. When by the operation of polishing
they are so much reduced as not to be elevated or depressed more
than about the millionth of an inch, they appear to become incapable
of acting separately, and produce the effect of a uniform surface.”
Compare also ‘ Nageli u. Schwendener,’ p. 86.

It will be seen from this that the degree of smoothness required to
convert the surface I have spoken of into an efficient reflector is to
the millionth of an inch. I have seen it stated that, if put under the
microscope, the surface of few microscope lenses would fail to show
lines and scratches left by the polishing material. Perhaps some
may be tempted to submit their objectives to this ordeal, and then to
calculate how far the marks so found exceed the millionth of an inch,
that is, how far the polishing of their glasses comes short of perfection.

The difficulties, then, are considerable. On the other hand,
popular report credits Mr. Whitworth with having constructed a
machine to measure to the millionth of an inch ! If this be anything
better than a stupid canard, and if to measure to the millionth of an
inch be really within the ability of our ordinary mechanics, surely to
polish, to that degree of exactness cannot be an insuperable difficulty
to our London opticians, who are confessedly the very flower of
artistic skill. At any rate, I think the attempt ought to be made ;
and what has been done in the way of reflecting telescopes may serve
as a guide. It is just possible that such reflecting simfaces might
fail to furnish sufficient light for very high powers; but they certainly
would be a comfortable and trustworthy aid to all powers under a

inch.

Speaking of opticians reminds me that, though I found most of
the German opticians knew little more of Schacht, Harting, Frey,
and Dippel than their bare names, yet I always found them furnished
with a well-thumbed copy of ‘ Nageli u. Schwendener,’ and some of
them were especially emphatic in their opinion of its merits, giving me
to understand that, in their estimation, it was the book par excellence *
I set it down at the time for just an ordinary German book on optics,
copiously dotted with trigonometry and optical diagrams, exhibiting
a fair quantum of good sense, — and certainly of botany, — by two
editors at once, one of them apparently supplying the good sense, and
the other the botany. Perhaps there is a trifle too much of botany
and crystallography, and what the editors call “ Mikrochemie ” ; but

* ‘Das Mikroskop, Tlieorie und Anwendung desselben, von 'Karl Nageli,
Prof, in Miinchen und S. Schwendener, Docenten der Botanik in Miinclien.
Mit 276 Holzscknitten. Leipzig, 1867.’

CORRESPONDENCE.

213

this will be a venial fault with those of kindred tastes, — those, I mean,
who believe with the poet,

“ The proper study of mankind is — fungi.”

I have since endeavoured to know it better.

It would be superfluous to call it profound ; for all German
scientific works at least try to be that. It is that, and something
more. It is a thoroughly practical treatise on applied optics, that is,
on optics applied specially to the construction and correction of micro-
scopical instruments, — a regular optician’s vade mecum, with all the
whys and wherefores reasoned out to the end, — in short, a veritable
book after Mr. Wenham’s own heart. Indeed, in many passages its
language is almost identical with some of Mr. Wenham’s recent utter-
ances ; so that the editors might seem rather to have been translating
than composing, only that they happened to publish their remarks a
few years earlier. And throughout the book there is an absence of
that spirit, so general in German writers, of affecting to ignore all
that has been written on the subject by other nations. They quote
Scotch, French, English, American, and Dutch authorities with perfect
impartiality, thus recognizing that science, like goodness, is the pro-
perty of no particular nationality. In their chapter, “ How to deter-
mine Angular Aperture,” after discussing the various methods proposed,
and Mr. Wenham’s amongst them, they remark, “ This [Wenham’s]
method has indisputably the great advantage, that we are enabled by
it to determine, not only the aperture of the objective in respect of
the whole amount of light it admits, but also the really available part
of it, that is, the part which supplies sharp and correct images.”
See p. 168.

I may add, that the work is written by men of acknowledged
eminence as mathematicians, who are at the same time notable micro-
scopists, and of high repute for their microscopical researches in their
own particular line ; so that their statements wrill hardly be open to
the sarcasms that might be levelled at microscopical assertions by
writers on optics ignorant of microscopy, or at optical remarks by
microscopists careless of optics.

I do not mean that all their theories will be acceptable to our
London opticians. The following, for instance, will, I know, be very
unpalatable : “ The use of condensers is in most cases superfluous,
where the mirror is sufficiently large, and can be brought up near
enough. The use of such things has a meaning only where one pur-
poses to enlarge the apertiu'e of the incident cone of light.” . . .
“ Condensers, therefore, are efficacious only in two directions ; they
give to the cone of light, which illuminates a particular area of the
field of view, an equal intensity in its entire cross-section ; and, in the
nest place, enlarge its angle of aperture. As for the other assertions
regarding the effects of condensers, that they dissipate the interference
lines at the margin of the object, and resolve difficult details pro-
portionately better, the more completely the correction of their
aberrations has been carried out, that is pure imagination.” See
pp. 91, 255. This, of course, is rank heresy ; but I suspect that

Q 2

214

CORRESPONDENCE.

the editors, if assailed on this point, would be quite equal to the
occasion.

But there is one passage (p. 169) so pertinent to the controversies
of the day, that I must give it in the authors’ own words : “ Es ist
vollkommen gleichgiiltig, ob der Oeffnungswinkel eines Mikroskops
beispielsweise 70 oder nur 68 Grad betrage. Es ist geradezu lacker-
lick, wie Harting mit Becht bemerkt, wenn man bei starkeren Objec-
tiven, wie es Manche gethan haben, die Grosse des Oeffnungswinkel s
bis auf Bruclitheile eines Grades angiebt. Und ebenso lacherlich
und unpraktisch ist es, Objective mit Oeffnungswinkeln bis zu 160°
und dariiber kerzustellen, wenn hievon wenigstens 40-50° auf einen
total unbrauchbaren peripherischen Theil des Systems fallen, wie
diess bei manchen englischen Systemen wirklick vorkommt.”

A translation of the entire work would be out of the question,
owing to its great bulk, — 628 pages large octavo. Of these about 358
belong to the microscope proper, while the rest of the book is devoted
to an exposition of their own peculiar views on gases, crystals, pro-
toplasms, cell-formation, plant-life, and what not ; all very learned
and very interesting, but which would have gone much better into a
separate volume, to be entitled, ‘ The application of the Microscope to
things in general.’

Yours faithfully,

W. J. Hickie.

Mr. J. Mayall, jun.’s, Critics; and the “Balsam Aperture

Question.”

To the Editor of the ‘ Monthly Microscopical Journal.'

224, Regent Street, London, September 2, 1875.

Sir, — Mr. Slack’s defence of his apology amounts to this : He
affirms that with Zeiss’s -jUli pneumo-lens, angle 68°, and C eye-
piece, with artificial light, he was able to rival the definition of
Surirella gemma as seen in Dr. Woodward’s photograph produced
with Powell and Lealand’s T^tk immersion, with sunlight. I am
content to leave that statement to carry its own conviction.

“ Crito’s ” attempt to answer my question “ Whence comes the
luminous field in the immersion lens if not from its having the power
to collect rays which are totally reflected when the pneumo-lens is
used?” lacks the sagacity he would affect, and does not “perfectly
account for the phenomenon.” He suggests, the luminous field might
have been obtained by the immersion lens having a larger angular
aperture than the pneumo-lens used. The very point of the experi-
mental proof furnished against Mr.Wenkam’s position in the “Balsam
aperture question ” by his Reflex Illuminator is, that when the pneumo-
lens is used on a balsam-mounted object (viz. Moller’s Probe-Platte),
the field rays are totally reflected by the cover-glass, — there are none
to be “ picked up,” — the total reflexion at the cover-glass is a barrier
that excludes the pneumo-lens whatever increase might be given to
the angle of aperture ; but when the high-angled immersion lens is

CORRESPONDENCE.

215

used, field rays enter tlie lens, giving a luminous field — rays from
balsam of greater angle tlian 41° — the very rays “ challenged ” by
Mr. Wenham. The optical law that forbids the pneumo-lens to
gather the field rays from the Illuminator also excludes it from all
rays nascent from the object of greater obliquity than 41° ; and con-
versely the law that has permitted the field to be luminous in tho
immersion lens with rays beyond 41° permits image-forming rays to
pass from the object beyond 41°. Whether the rays pass direct from
the total reflecting surface of the prism, or from the object, if they
reach the posterior surface of the front lens at equal angles of inci-
dence, they both follow the same process of refraction. That image-
forming rays deflected by the object, or nascent therefrom, of greater
angle than 41° do enter the immersion lens and are refracted into
the optical image is, I conceive, abundantly proved, — theoretically
by Professor Keith’s computation, experimentally by the fact that
definition entirely invisible to the pneumo-lens and manifestly the
product of earfra-oblique rays is visible with the immersion. Those
who care to follow the subject will at once note that the increase
of angular aperture due to the immersion principle is not the increase
“ Crito ” speaks of.

The answer to my question is, as Dr. Woodward and Professor
Keith demonstrated : That immersion lenses made on certain formulae
transmit a greater angle of rays than corresponds to the maximum air-angle.

I take this opportunity of saying that shortly after the arrival of
Dr. Woodward’s photographs of Professor Keith’s computation, I
drew rip a brief history of the “ Balsam aperture question,” and sub-
mitted it with the computation to one of the highest mathematical
authorities in England : the result was against Mr. Wenham. I should
have made this known, but I understood Mr. Wenham to reject the
experimental proof as being inadmissible in deciding the question of
image-bearing aperture. It remained to provide means by which rays
beyond 41° from balsam should be refracted through the immersion
lens ; and this was required to be done with legitimate means— such
as admitted of no cavil on the score of being made only for the
purpose of proof and of no moment in practical microscopy. The
Keflex Illuminator is surely not open to this kind of objection ?

I am, &c.,

' John Mayall, jun,

Mr. Garner’s Bucephalus.

To the Editor of the ‘Monthly Microscopical Journal.'

3, Queen Street Place, Upier Thames Street,
London, September 7, 1875.

Sir, — Having sent a copy of my letter to you of July 30th date
to Mr. Garner, he has in return kindly lent me the paper published
in the ‘ Zoological Transactions,’ December 8, 1835, to which he
referred in his communication to your Journal of July 11, and
accompanied the same with the following note to me, viz :

“ Dear Sir, — I send you my paper in which I figure a parasite which

216

CORRESPONDENCE.

I presume is allied to your Bucephalus ; possibly not identical with
it. I never found it free , but the individuals I found were remarkable
for sucb rapid and sudden movements as were described in your
animal. My short communication was written under the impression
that the assertion of the non-parasitism of Bucephalus was not con-
fined to your species or variety, whatever it is. I leave the matter
in your hands, and remain,

“ Dear Sir, yours very faithfully,

“R. Garner.”

With Mr. Garner’s permission I now enclose copy of the figure
in his paper.* In reference to it he says that he found it in the foot
of an Anodonta, and that it presented the following characters, viz :
“ In the mature state the body is more or less cylindrical in its shape,
but varied much at the will of the animal. At one extremity it has
two very long appendages, which are spiniferous at their terminations,
and which in some individuals have a row of round bodies attached
to one side for part of their length ; these appendages are contracted
with great rapidity, and are then very short. There is an opening by
a circular lip between these appendages. A contraction separates
this part, on which they are situated, from the rest of the body.
There appears to be another opening at the opposite extremity of the
animal.” I think it will be seen from the above as compared with
my animal, and also with the Bucephalus polymorphus and Haimeanus,
that although there is some resemblance in form and character, yet
that it more nearly approaches the B. Haimeanus than either, and
that all three differ very much from the creature I have found, and
which so far remains unique.

I remain your obedient servant,

John Badcock.

Remarks on Crito’s Letter.

To the Editor of the ‘ Monthly Microscopical Journal .’

Dalston Vicarage, near Carlisle,
September 11, 1875.

Sir, — In “ Crito’s ” letter, in the last number of the ‘ M. M. J.’
there are some passages which must, I conceive, excite surprise in the
minds of many of your readers.

Mr. Mayall had observed that, tried by the test of deep oculars,
the image with certain specified comparatively low-angled objectives
breaks up with any magnification beyond about 1000 diameters. In
reply, “ Crito ” quotes the nominal linear magnifying powers of lenses
of the same focal length as those referred to by Mr. Mayall, with
different eye-pieces, as though that were a conclusive answer. But
surely he forgets that the whole question at issue is not as to possible

* [We have received a copy of the figures from Mr. Badcock, but as they have
already appeared elsewhere wc think their reproduction here is unnecessary. —
Ed. 1 M. M. J.’]

CORRESPONDENCE.

217

amplification, but as to actual definition. Of course, the nominal
magnification can by the use of deep oculars be run up to almost any
figure ; but what practical worker with high-power lenses does not
know by experience how useless and deceptive is the further enlarge-
ment of an object by such means, after that point is reached at
which, for want of defining power in the lens employed, the image
begins to lose its sharpness and crispness, and to become indistinct
and woolly ?

Mr. Mayall had further noticed that, with Wenham’s Reflex
Illuminator, a high-angled immersion objective gives a luminous field,
when a pneumo-front gives a dark field ; and he asks, Whence comes
the luminous field ? In reply, “ Crito ” makes the singular suggestion,
that the dry may have had a smaller angle than the immersion lens.
But what has the angular aperture of the dry lens to do with the
question ? If the rays were totally reflected from the upper surface
of the cover, which they would reach after passing through the
balsam-mounted slide, but beyond which they could not get according
to the well-known optical law, there could be none to be picked up by
the dry objective, whatever its angular aperture might be. What
then could make the field,1 luminous when the immersion front was
used, but the entrance into the objective of rays which, with the
pneumo-front, were totally reflected? But “ Crito ” asks whether a plain
glass slip would not answer the same purpose as the Moller’s Probe-
Platte ? No doubt it would, so far as the mere brightness of the field
goes. But the Probe-Platte serves another purpose. For the objects
it contains, though attached to the cover and not in contact with the
glass slip, are brilliantly illuminated, thus proving that the rays
which enter the object-glass do not arise from mere diffusion of light,
but that they are bond fide image-forming rays. In the one case the
image of the diatoms is not there ; in the other it is there. This is,
as it strikes me, Mr. Mayall’ s answer to Mr. Wenham’s challenge.

The pleasantry which “ Crito ” discharges at Mr. Hogg at the close
of his letter arises, I think, from a misapprehension of his meaning.
Certainly he misrepresents his conclusion, which he could not do if he
rightly understood his abridged line of reasoning. And yet the argu-
ment, when fully stated, appears to be simple enough. Dr. Parkinson
proves that chromatic and spherical aberration, which arise from dif-
ferent causes, are to be corrected by different and independent means.
Theoretically, therefore, as Dr. Parkinson states, both may be corrected
together, and a perfect lens obtained. It is equally true from the rea-
soning that theoretically either of them may be corrected whilst the
other is left uncorrected. In other words, a lens may be achromatic and
not aplanatic, or aplanatic and not achromatic. From this the infer-
ence drawn by Mr. Hogg is, not, as “ Crito ” incorrectly states it, that
“ some object-glasses which are not achromatic must be aplanatic,”
which is simply absurd, but “that all chromatic aberration does not
involve spherical aberration,” which was the conclusion to be esta-
blished.

I am, Sir, your obedient servant,

Edmund Carr.

218

CORRESPONDENCE.

Mr. Branwell’s proposed Prize for the best Objective.

To the Editor of the ‘ Monthly Microscopical Journal .’

Sir, — Your Brighton correspondent, Mr. Branwell, F.R.M.S.,
makes a suggestion that “ the Royal Microscopical Society should
appoint a committee to settle upon a standard for physiological
glasses. That the Society should offer a gold medal every third year
or oftener for such glasses ”

It appears to me the appointment of a committee for that purpose
would he fraught with danger to the existence of our Society. Every
optician would have his candidate. Every optician’s friend or ac-
quaintance would be touted for his vote with such uncompromising
energy, that the whole subject of microscopy would become tainted to
the core with party spirit ; and in the chaos of our bickerings we
should lose all chance of getting access to the palatial realms of
Burlington House, which many Fellows have yearned for as the one
hope of reviving our declining reputation as a Learned Society.

When I endeavour to represent to myself in imagination the
probable effect, among the opticians, of the sight of Mr. Branwell’s
suggested gold medal to be competed for every third year, I seem to
see a whole Hogarthian series of delineations of human character
flitting in and about our cheerless assembly room at King’s College,
scarcely one of them having the least confidence beforehand in the
impartiality of the committee ; and only one of them to he gratified
every third year !

Such a prospect fills me with dismay. I much prefer our present
anarchical system, where every optician who has a friend among the
Fellows may induce him to swear by his — and only his judgment
in recommending optical work. Thus competition is kept alive.
Thus has every optician an interest in furnishing every one of us
with choice lenses. Thus may we pride ourselves in thinking we
each possess lenses of extraordinary excellence. The present system
favours us all individually, — that is why I like it.

If Mr. Branwell’s proposal were carried out, the very first award
might put me out of conceit with my lenses. I should sell them at a
loss, and get others from the “ gold medallist.” At the next award I
might be driven back to my discarded lenses ; and so on, until my
microscopical proclivities would be so tortured by anxiety — hoping
against hope ever to possess the very best lenses in existence (of
which at present I am undoubtedly assured by Messrs. X., my op-
ticians)—that, in despair, I should send the whole paraphernalia to the
auction room. It would probably be sold for an “ old song ” to some
dealer in second-hand apparatus, who would select out the valuable
portions, replace them by thoroughly worthless ones, and resell to one
of those aspiring amateurs who have perfect confidence in their own
judgment.

I remember some years ago a large sum of money was subscribed
to the “ Quekett Memorial Medal Fund,” to provide “ a medal, to be
called the 4 Quelcett Medal,’ and to be given at the discretion of the

PROCEEDINGS OF SOCIETIES.

219

Council (if possible annually) to sucli member of tbe Society who, in
the opinion of the Council, has best promoted tbe interest of Micro-
scopical Science ; ” but the Council have considerately stored it away
for some other purpose. If they were to revive the subject, we should
all put in our claims with such daring ambition, the Council might be
forced to award the medal alphabetically, according to seniority, — or,
perchance, have it scrambled for : the justice of the award would
probably be as likely to satisfy us one way as another.

Your obedient servant,

F.R.M.S.

PROCEEDINGS OF SOCIETIES.

Quekett Microscopical Club.

Annual Meeting, July 23. — Dr. John Matthews, F.R.M.S., Pre-
sident, in the chair.

The Tenth Annual Report of the Committee was read, giving a
very favourable account of the progress of the club during the year,
which was fully borne out by the details entered into.

The President read the Annual Address, in the course of which,
after reading the prospectus of the original constitution of the club,
he proceeded to consider how far the intentions of its founders had
been carried out. After a rapid review of the nature and motives of
their work, and of the eminently social character of their meetings,
he deprecated the supposed necessity for original research on the
part of a society composed principally of amateurs and students,
maintaining that the best thing they could do was to make themselves
well acquainted — before all — with the labours of their predecessors
and others, taking nothing for granted until personally verified as far
as possible. That, he considered, was the nature of real scientific
training. Adverting to the Re])orts of the Committee and Treasurer,
he congratulated the members on the prosperous state of the Society,
numerically, financially, and scientifically ; and concluded with the
inference that the Society had amply fulfilled the intentions of its
founders.

The elections then took place for officers and members of com-
mittee. Dr. Matthews was re-elected President for the ensuing
year.

Dr. Lionel S. Beale, F.R.S., &c., a past President of the club,
was balloted for and unanimously elected an honorary member.

Votes of thanks to thte President and officers were passed, also
one of a very cordial character to the Council of University College,
for the continuation of their permission to hold the meetings in the
College library, a favour which had been accorded to the club from
an early period of its existence.

220

PROCEEDINGS OF SOCIETIES.

Ordinary Meeting, August 27 — Dr. John Matthews, E.R.M.S.,
President, in the chair.

A paper was read by Mr. William Cole, M.E.S., on Sphoerularia
Bombi, an entozobn parasitic in Humble-bees. This was first de-
scribed by Leon Dufour in the £ Annales des Sciences Naturelles ’
for 183G, and subsequently formed the subject of two very instructive
memoirs by Sir J ohn Lubbock, in the ‘ Natural History Review.’
Mr. Cole gave a resume of the facts connected with the anatomy and
morphology of this extraordinary creature. It is found in the abdo-
minal cavity of the bee, in the form of a white worm-like animal
nearly an inch long and thickly covered with wart-like projections or
spherules, whence the name of the genus. Mr. Cole drew particular
attention to the great abundance of the parasite in females of Bombus
terrestris during the past spring. In several instances every indi-
vidual examined contained one or more specimens, and as many as
thirty-three were once found in a single bee. The young nematoids
also occurred in immense numbers — as many as from 50,000 to
100,000 in each insect. Near the end of each adult Sphoerularia is
invariably attached a small nematoid worm, which was described by
Sir John Lubbock as a male, passing an epizoic existence on the body
of his giant consort. By Schneider, however, it is held to be the true
female — the immense structure to which it is affixed being regarded
by him as a prolapsed uterus. Mr. Cole gave a brief account of the
facts on both sides of the question, and after sketching the probable
life history of the young Sphocrularioe, pointed out the direction
which investigation should take in an endeavour to solve the very
interesting questions connected with this anomalous creature, which
he recommended to the careful consideration of members in search of
a subject. The paper was illustrated by enlarged figures, and specimens
under the microscope.

The Fairmount Microscopical Society of Philadelphia.

This Society held its regular meeting on Thursday evening, April
15, 1875. The main topic of the evening was the kidney and its
diseases, particularly “ Bright’s disease.” It was illustrated by many
fine and unique sections of the human kidney, stained by means of
carmine. The explanations, volunteered by a member of the Society,
were remarkably clear and to the point. Quite a series of drawings,
made direct from the instrument, of urinary deposits, wTas shown at the
same time, tracing the course of the above disease in several patients
under treatment by the demonstrator. — Cincinnati Medical News.

Memphis Microscopical Society.

At the meeting of this Society, April 3, several matters of in-
terest were presented. A communication was received from corre-
sponding member, E. W. Morley, of Hudson, Ohio, giving his method
of measurement, under, very high magnification, of the striae on the

PROCEEDINGS OF SOCIETIES.

221

entire series of diatoms on tlie Midler’s test-plate. A pamphlet was
also received from Dr. Geo. E. Blackham, of Dunkirk, New York,
giving the history of the cases of trichiniasis caused by eating the
diseased pork, of which specimens had previously been sent to the
Society. From this article it appears that the dreaded trichina is by
no means so uniformly fatal in its effects as is ordinarily supposed.
Nevertheless, cases are on record where competent medical men
estimate that 1 cubic inch of muscular fibre contained 85,000 of this
parasite.

A pamphlet was also received containing an article by Dr. Chris.
Johnston, of Baltimore, identifying a deposit of earth found on the
banks of the Patuxent, in Maryland, as being of the same origin and
composition as the well-known Bermuda “ tripoli.” The microscope
at once demonstrated the identity of the two deposits, both being
made up of the fossil shells of diatoms, invisible to the naked eye,
but here aggregated in such countless numbers as to form extensive
tracts of land. Prepared specimens were also received from Mr.
Frank Miller, of New York, and Mr. H. G. Hanks, of San Francisco ;
for all which a vote of thanks was passed.

The President, Dr. Cutler, read a paper “ On the Microscopy of
the Cyclops,” and also gave some new and interesting facts regarding
certain diatoms found in the same specimen of water. Dr. Cutler
states that he has detected in these organisms undoubted cilia, by
means of which their peculiar and puzzling movements are effected.
In this connection an interesting discussion was had as to how far
motion is to be accepted as undoubted evidence of animal life. —
Cincinnati Medical News.

San Francisco Microscopical Society.

The regular meeting of the San Francisco Microscopical Society
was held in its rooms on Thursday evening, April 22, President
Ashburner in the chair. In addition to a very full attendance of
members, Professor Wm. H. Brewer, of New Haven, J. B. Bond,
of New York, Dr. J. N. Eckel, Dr. Henry Terrer, Dr. Murray More,
D. J. Staples, H. L. Hosmer, and W. N. Lockington, were present as
visitors.

The Secretary announced the receipt of the April number of the
‘ Cincinnati Medical News,’ containing valuable microscopical items ;
three numbers of the £ World of Science’; and from Mr. R. H. Ward,
the ‘ Kules of the American Postal Micro-Cabinet Club,’ with a letter
desiring that a circuit be organized on the Pacific coast. Messrs. J.
H. Carmany and Co. donated the May number of the ‘ Overland
Monthly,’ and Dr. Harkness presented a printed copy of his paper
read before the Sacramento Society for Medical Observation, in April,
1868, regarding Salisbiu’y’s Ague Theory, which is a very interesting
article to all microscopic botanists, and controverting the theory
advanced. Mr. H. Edwards presented ten papers of a series on
“ Lepidoptera of the Pacific Coast.”

To the object cabinet, Mr. W. II. Walmsley, of Philadelphia,

222

PROCEEDINGS OF SOCIETIES.

donated twelve beautiful slides, mounted with the following objects,
viz. : Scales of Lepisma saccharina, wolffia, Columbiana, fertile frond
of maidenhair fern, fertile frond of Lygodium palmatum, coccinella,
spinnerets of garden spider, American podura, culex (male and
female), head and tongue of horse-fly, gizzard of cockroach for
polariscope, and ovipositor of saw-fly.

Mr. W. G. W. Hartford donated seven slides, mounted with
Hhdbdomena arcuatum (Scotland), Aulacodiscus scaber, Gyrosigma
Spencerii (New York), guano (Gulf of California), diatoms from San
Francisco, transverse section of Indian corn, and wool from the Cape
of Good Hope.

Mr. H. G. Hanks donated a slide mounted by him with a section
of magnesian rock from Healdsburgh, and a number of seeds of
Papdrium somnifera from Turkey, the peculiar marking of the latter
being interesting and making a beautiful opaque object.

Mr. C. G. Ewing donated a slide mounted by him with the palate
of a land mollusc (Arion).

Mr. C. Mason Kinne donated four slides mounted by him with
Tingis liyalina, obtained by Mr. Edwards from Calaveras county,
California, and which proved to be a most beautiful object, the entire
upper portion of the insect being covered with a curiously woven
network of glassy appearance ; the very remarkable egg of a Cali-
fornia butterfly, Polyommattus xanthoides, and the cell structure of
the pith of elder. The fourth slide was mounted with what was
claimed to be worms taken from diseased teeth ; and in presenting
this slide Mr. Kinne read a short paper, which explained the matter
fully.

Mr. Henry Edwards donated twelve additional specimen's of the
Tingis liyalina taken from the flowers of the coeonothis, mammoth
trees, Calaveras county, California; two specimens of parasite from
the chrysalis of a species of brassolis, Panama ; and a gordius, class
entozoa, from Colusa, California, which was accompanied by a paper
giving a technical description of the characteristics of the genus ; and
if, as suggested by Mr. Edwards, this be a new variety, a careful
study of its habits, life history, and microscopic examination, would
furnish the material for a very valuable paper.

Dr. Harkness, who has just returned from a short trip to the
Sandwich Islands, exhibited several slides representing different
phases in the life history of the blight which is believed to have
been the cause of disease in the coffee plant of those islands.

The Doctor was unable to obtain, at the time of his visit, any
coffee leaves which were afflicted by the fungus, but brought with him
several leaves of the guava plant, which were infested with a blight,
said to be identical with that found on the coffee tree. These speci-
mens belong to the genus Hyphomycetes, which appears upon the
upper surface of the leaf as a black mould, and is a true fungus, the
mycelium forming a network over the surface of the article, aud its
filaments dipping downward into the cell beneath. From the surfaco
of the mycelium aerial hyphae are thrown off in branches, made up of
globose cells, adhering to each other, sometimes rising in a single

PEOCEEDINGS OF SOCIETIES.

223

stem, in others dividing into two or more branches. From these
branches arise, on the one hand, a capsule ( sporange ), with its cluster
of stylospores, and on the other spermagonia, with imprisoned sper-
matia. The slides exhibited showed different portions of the plant,
and proved that it was not the coffee blight — Hemileia vastatrix —
which proved so injurious in the island of Ceylon.

The Doctor also exhibited a specimen of confervoid algre, the
cedogonium, from Saucelito, and explained the marvellous manner
of the formation of its pores ; also from the same locality the
filaments of Zygnerna cruciata in a state of conjugation. His lecture
was listened to with interest, and was made plain by diagrams on the
black-board, at the conclusion of which he was requested to speak of
matters of microscopical interest which fell in his way at the islands.

Among them he mentioned that of the organization of the Royal
Microscopical Society of Hawaii, and which, from the interest mani-
fested by its members, will prove an adjunct to science ; while it and
our Society, its nearest neighbour, can maintain an intercourse to
their mutual advantage.

After the unanimous adoption of the following, the meeting
adjourned :

Resolved, — That the thanks of the San Francisco Microscopical
Society be tendered to Dr. Adolf Barkan for his interesting and
instructive lecture on the “ Ophthalmoscope ” at the last meeting, and
that the trustees be and are hereby authorized to extend to him the
privileges of the rooms and apparatus for one year.

The regular meeting of the San Francisco Microscopical Society
was held on Thursday evening, May 6, with a large attendance of
members and the following visitors: John H. Caswell, of New York,
a corresponding member ; John W. Young, Salt Lake City ; J. M.
Red way, Placerville ; S. B. Christy, Berkeley ; Henry Taylor, M. do
Kirwan, Chas. G. Yale, and Arthur Hayne, of this city.

Under the head of donations the library received many important
additions, among them being four numbers of the ‘ Monthly Micro-
scopical Journal,’ April number of the ‘American Naturalist,’ and
three scientific works, entitled ‘ Fungi, their Nature and Uses,’

‘ Chemistry of Light and Photography,’ and ‘ Nature of Life.’

Dr. Christopher Johnston, of Baltimore, donated material for
mounting, in the way of spicules of Eupledella speciosa, rosette form,
and teroxide molybdenum for the polariscope.

Mr. D. Mason Kinne presented two slides mounted by him with
diatoms, Istlimia nervosa, Cliff House beach ; and seeds of Paparium
somnifera.

Letters from Drs. C. Johnston, R. H. Ward, J. A. Thacker,
Messrs. Eugene Bourgogne and J. Edwards Smith, were read, each
containing matters pertaining to microscopy, and evincing interest in
our Society, after which Mr. H. G. Hanks placed on the table his
spectroscope, and proceeded to make a few remarks relative to the
construction and use of this instrument. His remarks were devoid of
technicalities, and with the use of the black-board he made the subject
quite clear.

224

PROCEEDINGS OF SOCIETIES.

After showing tho characteristic absorption bands of various
coloured solutions, the spectra of flames in which different sub-
stances were volatilized were shown, and their beauty and fixed
position noted.

Perhaps there is no single discovery of the last quarter of a
century of so much scientific interest, and which has enabled the
educated observer to learn of the constituents of bodies unapproach-
able, as the spectroscope, and combined as it now is with the micro-
scope, the student in spectrology has a wide field for original and
interesting work.

After an announcement by the President that the annual recep-
tion of the Society would be held in Mercantile Library Hall some
time during the last week of this month, the meeting adjourned.

Adelaide Microscope Club, South Australia.*

The monthly meeting was held on May 28, 1875, Mr. G. Francis
in the chair. The following objects were exhibited : Pollen from one
of the Wattle trees growing in the far north, by Mr. Babbage ;
peculiar forms of Foraminifera (?) from the salt lakes on the penin-
sula, by Mr. Young ; thin sections of the bitumen-like substance
found near the Coorong and called here Coorongite, by the Chairman.
The consideration of the time for holding the annual conversazione
was postponed till the July meeting. The Chairman then introduced
the subject for the evening’s study, viz. Ferments, and gave a succinct
account of the views held by different sections of the scientific world
in reference to fermentation. The subject was a difficult one, but he
thought the balance of evidence was in favour of Pasteur's theory.
The various kinds of fermentation were briefly referred to, and the
saccharine, acetous, and lacteous were more fully discussed. Numerous
specimens of the organisms found in yeast, beer, “ diseased ” wines,
and other fermenting fluids, were shown during the Chairman’s
address.

* Report supplied by Dr. Whittell, Adelaide.

“he Monthly Microscopical Journal Novr 1. 1875

Pl.CXDC

Mel icerta, tyro .

THE

MONTHLY MICROSCOPICAL JOURNAL.

NOVEMBER 1, 1875.

I. — On a New Melicerta.

By C. T. Hudson, LL.D., F.R.M.S.

( Read before the Royal Microscopical Society, Oct. 6, 1875.)

Plate CXIX.

In a review, that I read some time ago, of Mr. Wood’s interesting
book ‘ Homes without Hands ’ the critic remarked that the author
had omitted to notice one of the most curious of such structures,
namely “ the tube of Melicerta.”

The criticism was just, and yet the critic was inaccurate ; and
while pointing out an omission in Mr. Wood’s book he was guilty
of a blunder in his own review, for he spoke of “the tube of
Melicerta,” just as one would of the cestus of Venus, or of the
club of Hercules ; — as if the rotifer had as inalienable a title to
his tube, as the hero had to his weapon, or the goddess to her
girdle.

No doubt the critic erred in good company ; for what micro-
scopist has not viewed with delight the opening of this living
flower, and who has ever seen it set otherwise than in a pelleted
tube, and who would have hesitated to assent to the proposition
that all Melicertae have these marvellous homes ? Nature however
seems to have hut one law that knows no exception ; and that is
that all general statements are untrue. Fifty years ago every
naturalist would have considered it an axiom that every vertebrate
animal had a skull ; and yet all the while burrowing in the sands of
Cornwall there was the headless Lancelet, a vertebrate animal with
the heart of a worm and the lungs of a mollusc, apparently created
for the express purpose of driving classifiers mad.

EXPLANATION OF PLATE CXIX.

Fig. 1. — Female of Melicerta tyro ; oral view.

„ 2. — „ „ aboral view.

„ 3. — „ „ side view.

a, a third antenna ; b, ciliated cup.

„ 4. — „ „ side view, from below.

„ 5. — „ „ a young specimen.

„ 6. — Supposed male of M. tyro.

All the figures are on the same scale, and all are magnified about 125 times
linear.

VOL. XIV.

R

226 Transactions of the Royal Microscopical Society.

Who would once have scrupled to say that no monkey has the
teeth of a rat, or that no rat has the hands of a monkey ? Yet
the Aye Aye presents the systematizer with either absurdity he
pleases.

That every rotifer has a rotary apparatus seemed an absurdly
self-evident proposition, till Gosses Taphrocampa, Claparede’s
Balatro and Mecznikow’s Apsilus, showed that Nature will not
submit even to the widest generalization, and that rotifers may exist
without the very apparatus to which the whole class owes its name.

In truth Nature has no such fancies as those Man is ever
ready to credit her with. She has hut one law — endless variety ;
and her varieties blend into one another by such fine gradations
that no natural system of classification can be other than unsatis-
factory ; doomed to he destroyed and re-cast by every succeeding
generation of naturalists, as fresh discoveries destroy the value of
those differences which earlier classifiers have relied upon for
separating allied forms.

So long as the tube -makers were represented only by Melicerta
with its four-lobed disk and pelleted tube, Limnias with its two-
lobed disk and smooth compact tube ; and (Ecistes with its one-
lobed disk and irregular fluffy tube, the genera of the Melicertidae
were comfortably distinct from each other. But the discovery of
several new species, and the more thorough investigation of the
older forms, have been steadily bringing all these genera closer and
closer.

Gosse, Huxley, Leydig, Williamson, Claparede, and others have
studied the structure and use of their trochal disks, their internal
organization, and the nature and mode of secretion of their gela-
tinous sheaths ; and the result of their labours is that such a
similarity of structure and habits is seen to run through the whole
group that Gosse has even proposed to make but one genus of
them all.

The new rotifer, which is the subject of this paper, will, I think,
prove a notable ally in helping to break down the barriers that have
hitherto separated the genera of the Melicertidae.

I found it this autumn on a piece of Anacharis given to me by
Mr. W. Fiddes of Bristol, who had brought it from Sutton Park
in the hope of getting something worth exhibiting at our Micro-
scopical Soiree. I placed a bit of the weed at random in a zoophyte
trough, and on bringing down my inch objective on it, had the
pleasure of seeing this charming rotifer fully expanded in the very
centre of the field. It is a Melicerta with a gelatinous sheath, very
like that which invests the Floscules, and yet with a distinct cha-
racter of its own. Two striking peculiarities at once catch the eye ;
namely, the great size and butterfly shape of the trochal disk
(Fig. 1), and the wonderful length, backward setting, and great

227

On a New Melicerta. By Dr. G. T. Hudson.

flexibility of the antennae. The animal reminds one at once of
Mr. Davis’ (Ecistes longicornis. Of course I was very curious to
know if it possessed its kinsman’s ciliated cup for making pellets.
Whether it was a Melicerta without a pellet-cup, or whether, having
the apparatus for making pellets, it failed to make use of it, — in
either case its condition was a strange one. With some difficulty I
so clipped the leaf which a specimen was on, as to get the creature
comfortably placed in a compressorium ; and although it was
limited to a very thin plate of water, it still continued to come out
of its sheath and to unfold its disk. I then distinctly saw that it
possessed a ciliated cup (Fig. 3, b) with thick edges, but without a
trace of any extraneous matter revolving in it. Now the gelatinous
sheath is excreted in some way by the animal, but as similar sheaths
are excreted by Stephanoceros, (Ecistes, and Floscularia, which
have no ciliated cups, what is the use of the cup in this new Meli-
certa ? Has it really had the organ given it not for its own use,
but in order that a more highly developed relative might have an
improved and effective form of it, without too great a break in the
ascending series of animal life ?

I think it possible to give a simpler solution of the riddle.
Most of the rotifers have in some parts of their bodies organs for
secreting a viscous fluid ; in the great majority of cases they lie at
the extremity of the foot ; either at the ends of the pincers as in
Synchseta or Euchlanis, or in a ciliated cup as in Pterodina, or on
two ciliated projections at the posterior end of the body as in
Pedalion. The Philodines can secrete this fluid in great abun-
dance ; and, as Mr. Davis has conclusively shown, so encase
themselves with it as to resist the destructive effects of a high
temperature and absolute dryness. The tube-makers have this
secreting organ below the mouth and nearly midway between the
antenna?, and on or near it fall atoms which have made the circuit
of the trochal disk in the groove leading to the mouth, and which,
rejected by the organs of taste at the entrance to the buccal funnel,
have been hurried over the ciliated chin.

These atoms mix with the viscous secretion and accumulate
round about the neighbourhood of the gland ; till the animal,
apparently annoyed by their presence, contracts itself with a
sudden twist and rubs them off on to its tube by a sideway motion
of the head, which is characteristic of the Melicertidas. In this way
the gelatinous sheaths are strengthened and frequently rendered
quite opaque. When the creatures grow in very clear water their
sheaths are so free from foreign bodies as often to be quite trans-
parent. If paint is put into the water (as has been often shown)
it soon appears in the newly formed portion of the case. In the
‘ Transactions of the Boyal Microscopical Society,’ 1867, Mr. Davis
has given an excellent drawing of the tubes of (Ecistes enlarged by

228

Transactions of the Royal Microscopical Society.

the addition of atoms of carmine. Both Melicerta rinyens and my
new rotifer, which I have named Melicerta tyro, have their secre-
ting gland below a ciliated cup, the cilia doubtless in their case,
as in that of Pterodina, acting to keep the sticky surface of the
gland free from constant clogging. But the cup of M. tyro differs
from that of M. rinyens in its not being united by lines of cilia to
the ciliated chin. In M. rinyens two constant streams of very fine
particles may he seen to trickle through two notches on either side
of the chin, and to he conducted gently into the ciliated cup
there to be converted into pellets ; while the larger ones are hurled
furiously over the ciliated chin. M. tyro has not got these lines of
fine cilia from the notches in the chin to its ciliated cup, and so all
the atoms large and great rejected at the mouth fly swiftly off
together over the chin, and never reach the cup which lies just
beneath. It is the lack therefore of these special cilia which seems
to prevent M. tyro from making the same use of its cup that
M. rinyens does.

The sheath of M. tyro is generally tolerably transparent, and
like that of all the tube-makers, it is not a hollow cylinder, but
(if I may use the term) a solid one with a tubular axis of very
small bore, up and down which the rotifer moves. Viewed as a
transparent object, it is sometimes difficult to make out the real
structure of the tube, but with dark-ground illumination and with
the binocular there can he no doubt about it for a moment.

The central tube down which the stem of the rotifer passes is
often widened at the top into an inverted cone by its frequent semi-
contractions ; and this portion too is often rendered conspicuous by
the debris of confervae, or by diatoms rubbed off on it by the twisting
Melicertan. When the creature contracts wholly it does not tend
to make such a cone ; and as now and then it has fits of complete
contractions, and afterwards of semi-contractions, so at one time it
forms a dirty cone at the top of its tube, and at another buries the
cone with fresh accumulations of evenly distributed viscous secre-
tions. Thus it happens that as the animal ages and the tube
grows, tiers of discoloured cones occur one above another ; and all
of these, as the animal works up and down in its tube, are pushed
at last into horizontal layers. This is seen in all the figures in the
Plate, but especially in Fig. 2, in which the layers — the flattened
surfaces of the discoloured cones — are sprinkled with diatoms.

The troclial disk acquires its butterfly shape from a habit which
the creature has of bending the corners of the two top lobes of the
disk. The four lobes are really all rounded just like those of
M. rinyens, and are often seen fully expanded and round. The two
antennae are of prodigious length; and, owing to their size and
transparency, it is easy to see how the muscle that runs up to the
bunch of setae at the top can withdraw them, by infolding the tube

229

On a New Melicerta. By Dr. G. T. Hudson.

even till tlie knob on which the setae are placed comes right down
to the very base of the antenna.

When the animal is contracted and shrank down into its sheath,
the antennae are closely applied to its club-shaped body ; and as it
rises they slowly rise also from their curved and recumbent position,
while the action of the transverse muscles at the same time expands
the animal, and (by forcing its perivisceral fluid into the tubes)
pushes up the setae-bearing knob till the antenna attains its full
length. This too is almost always the signal for the unfolding of
the trochal disk.

The internal organs are so like those of M. ringens that there
is hut little to say of them. One point however is worth noticing,
and that is that I have no doubt that the lower stomach acts in this
animal as the contractile vesicle.

The majority of rotifers, as is well known, have twisted tubes
on each side of their bodies carrying ciliated tags, and these tubes
generally open into a contractile vesicle which in its turn empties
itself into the cloaca, or into the lower stomach. But some
rotifers have no contractile vesicle ; and some, as Pterodina, have
apparently the ends of the tubes enlarged in lieu of it. It has been
made out in one or two cases that where there is no contractile
vesicle the tubes open directly into the cloaca ; but in the case of
M. tyro I distinctly saw on two occasions the empty lower stomach
expand and become very transparent, just as the contractile vesicle
does periodically; and after being slowly dilated to its utmost
expansion, it shot out its perfectly fluid contents through the vent.

While this was going on the passage from the upper to the
lower stomach appeared to he completely closed.

Of course it is impossible to see any fluid pass from the tortuous
tubes into the lower stomach, nor indeed did I quite succeed in
satisfying myself that I had seen their points of junction with it :
hut the tubes themselves are readily seen, and so with a little care in
focussing are the ciliated tags, of which I counted five on either
side.

My specimens all died before I had finished my investigations,
hut Mr. Bolton of Stourbridge most kindly came to the rescue and
sent me a small piece of Anacharis on which there were nearly a
score of the new rotifers, most of which had bred in his own tank.
There were also many eggs attached to them, and I eagerly
scrutinized all the specimens in the hope of finding eggs whose size
and shape might denote males. While doing this I saw a young
male rotifer circle round the female which I had under observation,
and then dart off in their usual headlong fashion. This was too
great a prize to he willingly surrendered, so I removed the zoophyte
trough from the stage, and with eye-lens and pipette explored the
vast Atlantic in which the little creature was disporting itself, till

230 Transactions of the Eoijal Microscopical Society.

I found and captured it. When it was transferred to a com-
pressorium and gently held captive, it proved to be a newly hatched
specimen barely the Tio of an inch long, and with so granular
and corrugated a skin that I could not clearly make out the whole
of its internal structure. Not indeed that there is ever much in a
male to make out ; but it ought to have shown both the water
vascular system and its muscles — and neither was to be seen owing
to the unfavourable condition of the surface. The brain lying
between the head and dorsal antenna was plainly visible, and so
were the spermatic sac and penis — in the former of which could be
seen the constant motion of the spermatozoa, though it was im-
possible to make out the spermatozoa distinctly.

As I did not see this animal hatched from one of the eggs of
M. ttjro, I cannot be certain that it is the male of that rotifer ; but
there was no other rotifer in the trough except M. ringens of which
it could be the male.

I have however little doubt that it is the male of M. tyro,
for I received soon afterwards from Mr. Wills, President of the
Birmingham Microscopical Society, some excellent drawings of
M. tyro, among which was figured a male animal very like the one
I have just described, and which I have drawn at Fig. 6. Mr.
Wills had very kindly assisted me to find the pool from which the
new rotifer had originally been taken, and on examining the speci-
mens which he had taken home for himself had observed a male
whirling round one of the females, and had secured a characteristic
drawing of it.

In both cases I believe M. ringens was also present ; — so that
this male might belong either to M. ringens or M. tyro, but in
either case it adds the genus Melicerta to the dioecious rotifers.

It has been suggested to me that my new rotifer is possibly
Tubicolaria ; and if this suggestion be correct a good many of
my remarks at the commencement of this paper would lose their
point. Now the genus Tubicolaria was formed by Ehrenberg to
receive a Melicertan that had no eyes at any time of its life, and
lived in a gelatinous sheath. But I have seen the young female of
M. tyro hatch from the egg, and have seen its two pink eyes when
in the egg, and also when it has first escaped. Fig. 5 represents a
very young one which I found just beginning to construct its
sheath, and it too had two well-marked eyes : so that even if. my
rotifer is the same as that to which Ehrenberg gave the name
of Tubicolaria, it ought not, according to Ehrenberg’s system, to
be placed in a different genus from Melicerta ringens. It is true
that Ehrenberg says he is not sure about the eyes, and he never had
seen but two solitary specimens ; but without the distinction of its
being eyeless there would remain only that of the gelatinous sheath,
which is utterly insufficient to rest a new genus on.

On a New Melicerta. By Dr. C. T. Hudson.

231

There only remains the question as to whether or no it is a
newly discovered animal. Now Ehrenberg’s figure is egregiously
unlike M. tyro. The antennae of Tubicolaria naias are short,
those of M. tyro are very long ; and while the trochal disk of the
former is barely more than the width of the body, that of M. tyro
is at least three times as wide.

Moreover Ehrenberg states that his Tubicolaria naias is in his
opinion the adult form of Dutrochet’s Rotifer albivestitus. Now
I have read Dutrochet’s paper which appeared in 1812 in the
‘ Annales du Museum d’Histoire Naturelle,” and while his written
description is very vague, his figures are so bad that it is impossible
to determine anything from them. He however distinctly states
that the antennae of Rotifer albivestitus were much shorter than
those of Melicerta ringens, while those of M. tyro are very much
longer. To sum up then, I think it not unlikely that Ehrenberg
would have called M. tyro a Tubicolaria, but I do not think that
either he or Dutrochet ever saw it : — and it is clear that whether
they did or no, it has no right to a different generic title from
that of Melicerta ringens ; for if the difference in the tube is to be
held sufficient to constitute a new genus, then must Melicerta
jpillula, Mr. Cubitt’s new Melicertan, have a new generic name.

1 ought to mention that Mr. Bolton tells me he found this new
rotifer some twro years ago in his prolific pond at Stourbridge.

232

Transactions of tlie Royal Microscopical Society.

II. — On the Identical Characters of Chromatic and Spherical
Aberration. By Dr. Koyston-Pigott, M.A., F.B.S.

{Read before the Royal Microscopical Society, Octc^r 6, 1875.)

During the experience of the last twenty-five years I have had
opportunities of hearing a number of persons express opinions about
spherical and chromatic aberration as though they were totally
different things.

To show how identical they are in the nature of things : Take
an ordinary burning-glass and expose it, first, to blue solar light,
and secondly, to red.*

Here, the spherical aberration of white light will now he changed
into the spherical aberration of the blue and red rays. It will be
found first of all with the blue, that the image of the sun is formed
nearer to the lens ; and secondly, that the red rays form an image
farther from it.

This should he well known ; hut another point will strike the
accurate observer, that the size of the image differs in the two cases.

Lastly, if the marginal rays of the burning-glass he compared
with those of the centre the image will be formed at very different
places, showing the spherical aberration of the blue ray ; and the
same experiment determines the spherical aberration of the red.
This is for convenience called chromatic aberration, but all the
time it is really and intrinsically the chromatic spherical aberration.
For it is the aberration caused by the spherical forms of the lens,
according as the light is blue or red.

I have noticed that in recent numbers of the ‘ M. M. Journal ’
a confusion has been made as regards spherical and chromatic
aberration. Thus, one writer makes the somewhat startling
statement that all chromatic aberration does not involve spherical
aberration. It may be safely declared, in direct contradiction to
this, that the aberration of every coloured ray passing through a
glass lens is wholly due to the spherical curves of the lens. Chro-
matic aberration, in fact, being really the spherical aberration
of the particular colour passing.

There is no other method of finding the chromatic aberration
of a given coloured ray except by using the refractive index of the
colour instead of that of mean rays in the expression for spherical
aberration : mean rays meaning white light.

It is true that Parkinson says achromatism depends on focal
length. But he also says that only as many lines of the spectrum
can be united as there are systems of lenses : so that if there were
eight lenses of different refractive powers, eight fixed lines of the
spectrum only could be united.

* Using blue glass or red as a shade.

Chromatic and Spherical Aberration. By Dr. Royston-Piyott. 233

And speaking of irrationality of dispersion, he says, “ if it had
no existence we might simultaneously unite lights of all species.
But since the colours are disproportionately dispersed in different
media, the other colours will in such a case he very nearly but not
exactly united. A pencil therefore of light refracted through an
achromatic combination will illuminate a screen with light still
slightly coloured, and give rise, as we have stated before (Art. 167),
to a secondary spectrum. A combination of different media achro-
matic for all kinds of light being thus in general unattainable, it
is customary to unite rays which are powerfully illuminating and
also differ much in colour, the rest remaining partially united.” *

Another familiar example of chromatic aberration being merely
the spherical aberration of a coloured ray is given by Sir John
Herschel’s explanation of the achromatism of the Huyghenian eye-
piece. |

Finally, to give examples, the spherical aberration of the blue
ray is very different from that of the red ray.

Whenever spherical aberration exists, there also exists for mono-
chromatic light a least circle of aberration or the smallest ring
through which all the rays from a given lens pass.

For the same lens, aperture, and same conditions of focal distance
or origin of light, considered as a point, the size of this ring is
directly proportionate to the dispersion of the glass for that par-
ticular colour.

When photographs were taken by Dr. Woodward with blue
light, the spherical aberration of the other coloured rays was entirely
got rid of. Dr. Woodward would have found a much more blurred
image with ordinary compound solar light.

A blurred image or indistinctness can be produced by residuary
spherical aberration alone. This very aberration varies notably for
different colours. It may be as well to state that every funda-
mental expression or calculated formula for determining aberration
is used only for homogeneous light, that is, light of only one
refractive index ; but that may be any value found in nature.
In this way the chromatic aberration of a given colour is found
from the spherical : by substituting the refractive index of the said
colour in the formula for the spherical aberration.

It is quite plain, to common sense, that the spherical curvature
of a lens must produce spherical aberration whatever homogeneous
coloured ray shall be transmitted through it. So that all chromatic
aberration does involve spherical aberration : and is identical with it
so far, that every coloured ray on passing through spherical surfaces
of refraction (as in an ordinary lens ) actually produces its own

* Page 160, Parkinson’s ‘ Optics,’ 2nd edition,
f See Herschel on the Telescope, page 56.

234 Transactions of the Royal Microscopical Society.

peculiar spherical aberration, dependent on the nature of the glass
employed.

One other point should be stated, and that is, aplanatism is
usually calculated only to a first approximation, though it is
capable of being done to a second and third still nearer approxima-
tions: consequently the conventional expressions now loosely in
use of aplanatism and achromatism are approximate terms: the
greater the number of lenses of different kinds of glass, the greater
number of the lines of the spectrum can be united in one focus.
And for those lines or1 rays so united there exists no absolute
achromatism and aplanatism, but a residuum more or less delicate
must remain. Some of these ununited rays produce corresponding
aberrations. Hence the extraordinary precision of definition pro-
duced by stopping out the refractory spectral lines.

( 235 )

III. — Perforating Proboscis Moths. By Henry J. Slack.

{Read before the Royal Microscopical Society, Oct. 6, 1875.)

At the meeting of the Royal Microscopical Society, on the 6th
October, Mr. Slack, Hon. Sec., called attention to a slide of the
perforating proboscis of a moth given by Mr. Mclntire to the
Society in April, 1874, and described by him in a short paper
of that date as having been purchased amongst damaged speci-
mens, and said to have come from West Africa. Mr. Mclntire
appears to have been the first observer who described this object,
and thus opened a new chapter in the history of lepidopters, none
of which had been supposed to be furnished with such an apparatus.
Mr. Slack read some portions of a paper on this subject by M. J.
Kiinckel which appeared in ‘ Comptes Rendus ’ of the French
Academy for August 30 of this year, and the following extracts
are supplied by him.

M. Thozet, a French botanist, established in Australia, at
Rockhampton, a little town on the Tropic of Capricorn, called
M. Kiinckel’s attention, in 1871, to a lepidopter of the genus
Ophideres which he accused of perforating oranges to feed upon
their juice. Convinced, as all naturalists were, that lepidopters
without exception had flexible probosces destitute of rigidity,
M. Kiinckel doubted M. Thozet’s observation, and put aside the
alleged devastators, intending to examine them at leisure.

Lately he received a copy of the ‘ Capricornian,’ No. 9, 8th
May, 1875, published at Rockhampton, and found in it an
anonymous paper confirming M. Thozet’s account, and establish-
ing beyond doubt that 0. Fullonica perforated the oranges, as
stated before.

M. Kiinckel then examined his specimen, and says, “ By a
strange exception lepidopters of the genus Ophideres Boisd. have
a rigid proboscis and a veritable auger and he describes it as
capable of piercing the most resisting envelopes, and quite a model
for an artisan’s tool. It is incorrect to call the proboscis rigid, as
it curls up in the usual way; but instead of a soft terminal portion,
it has a hard one which he thus describes. “ The two adpressed
maxillae terminate in a sharp triangular point furnished with two
barbs. They then swell out and present on the lower surface three
parts of the thread of a screw, while their sides on the upper surface
are covered with short spines springing from a depression with
sharp hard sides. These spines are to tear the cells and the pulp
of the oranges, as a rasp opens those of beetroot, to extract the sugar.
The upper portion of the proboscis is covered from below and on
the sides with fine serrated striae disposed in a half helix, which
give it the qualities of a file. These striae are from time to time

236 Transactions of the Boyal Microscopical Society.

interrupted by small non-resisting spines which serve as tactile
organs. The orifice of the canal by which the liquid's ascend is
situated on the lower face below the first thread of the screw. The
figures beneath render sufficiently intelligible this short description.

A B C

A, profile view ; B, seen from beneath ; C, from above ; t, internal canal ;
o, aperture of canal.

“Not content with examining 0. Fullonica, I studied 0. Sala-
minia, 0. materna, and 0. imperator, which all had auger-like pro-
bosces. The structure of these maxillae affords a generic character
of great value ; it moreover establishes a closer relation between
the lepidopters, the hemipters, and certain dipters which have
maxillae adapted to pierce tissues.”

^lcalJ°urn,a,l Nov. 1. 18 /5 .

Pl.CXX.

wy/^st icC-o. so

The Monthly Microscopical Journal Nov.1.1875. PI .CXXI

( 237 )

IV. — Trochosphsera (equatorial is, a spherical Rotifer found in
the Philippine Islands. By Herr Semper.

Plates CXX., CXXI., axd CXXII.

It is well known that the farther we descend in the scale of animal
life a gradual abolition of all climatic contrasts becomes apparent ;
whereas among the higher animals these contrasts are exhibited
in innumerable species and varieties. The Botatoria on the
whole follow this rule. My surprise was therefore considerably
heightened when in a very limited space on the Philippine Islands
I discovered a specimen differing from all its kin in .the highest
degree. The strange relations existing throughout its organiza-
tion will perhaps justify a more minute description.

This creature is found among worms (for the most part naids),
copepoda, other rotifers, infusoria, &c. (all of which resemble the
European forms more or less), in the fresh water of the ditches
which surround and intersect the rice-fields of the plain of Zam-

EXPLANATION OF PLATES CXX., CXXI., AND CXXII.

Figs. 1 and 2. — Trochosphsera slightly magnified. Fig. 1 seen from the side.
Fig. 2 as seen from the anal pole, a, mouth; b , mastax with jaws; c, brain-
ganglion ; d, pharynx (oesophagus) with the two glands r ; e, stomach ; /, cloaca ;
g, anus; A, ovary; i, oviduct; h, excretory duct ; l, muscle-layer; m, eye; nn, the
two problematical lateral sense-organs ; p, middle nerve for the middle sense-
organ o ; q, equatorial circular fringe.

Fig. 3. — Section of mouth largely magnified, o, mouth ; m, pharyngeal muscle ;
c, cilia of the equatorial fringe (not represented in front of the mouth to show the
finer cilia of the buccal funnel) ; g, ganglion ; I and 2, nerves to the pharynx and
front part of the equator ; 3 and 4, nerves to muscles, eyes, and sense-organ ;
5, nerve of the excretory organ ; 6, unmatched single nerve of the sense-organ o.

Fig. 4. — Muscle surface of one side, a, equatorial fringe ; 6, muscle-hollow
along whicli the muscle surface l lies ; /, its passage into the aboral hemisphere ;
3 and 4, nerves to the muscles ; 3 6, nerve to the lateral sense-organ ; 4 a and b,
nerves to the eye and another ganglion-shaped organ (cp. Fig. 5).

Fig. 5. — 4 a, nervus opticus ; a, lens of the eye ; 6, pigment covering of the
eye ; c, ganglion opticum ; d, uncertain organ, final swelling of the nerve 4 b.

Fig. 6. — Part of the equatorial fringe, where it is broken at a point immedi-
ately opposite the mouth, a a', blunt ends of the circular fringe ; 6, its connecting
bridge not ciliated ; n 6, middle nerve ; /, ganglion-like swelling belonging to it ;
g, middle nerve to the sense-organ h with its final body i ; g g', nerves of the back
part of the equatorial fringe.

Fig. 7. — Organ of excretion, a, duct ; b b, the two glandular lobes ; c c, the
two ciliated channels, which cross (or unite ?) at d\ c\ extreme end of the ciliated
channel to nerve 5 ; n 3 b, nerve to the problematical lateral sense-organ c ; /, its
extreme body.

Fig. 8. — Jaws of the mastax.

Fig. 9. — a, rectum ; b, contractile bladder ; c, cloaca ; d, stomach ; l, oviduct ;
m, muscular band of the ovary ; o o, ovary ; n n\ excretory ducts.

Fig. 10. — Cloaca and sexual organs with developed eggs, a, an egg in the
cloaca; 6, egg in oviduct; c, oviduct; d, point of junction with the cloaca;
l, rectum ; /, eggs in the ovary with star-shaped nuclei.

Fig. 11. — A developed young Trochosphsera found in the cloaca of another
specimen.

238 Trocliosphtera sequatorialis. By Herr Semper.

boanga. In tbe months of October and November, 1859, it was
not rare there. Of a perfectly spherical shape (Figs. 1, 2, and 11),
without any perceptible front or back end, this animal, in
diameter, moves with a continuous rolling and circular motion ; no
fixed axis of direction, however, can be distinguished. It is never
at rest, and never fastens itself on any stone or plant, for it possesses
no organ whatever, which serving such a purpose might be regarded
as a homologue to the foot of rotifers. In fact, motion is caused
simply by its strangely altered trochal disk. Just as the animal
itself forms a perfect sphere, so with mathematical symmetry the
rotatory organ surrounds the sphere in the shape of a fringed
equator, and thus divides the creature into two hemispheres exactly
equal in size. The remaining organs certainly somewhat disturb
this symmetry. The greater part of the inner organs lie in the
one hemisphere, whilst the other contains hardly any. The perfect
transparency of the skin renders it possible to perceive their relative
positions. In the following description I shall give the name of
“ oral ” to the hemisphere containing the mouth and anus, of
“ aboral ” to the other. The surface of both hemispheres is per-
fectly smooth, yet exhibits certain cavities leading to the mouth
and anus (Figs. 1, 2 a and g) as well as certain places of junction
of other organs, which, on more minute investigation, are found
to be organs of sense and muscles. As almost all the internal
organs are situated in the oral half, their orifices and places of
junction of course belong to the same hemisphere. The equatorial
line of fringe is not quite complete. If we call a meridian touching
the mouth (Figs. 1, 2 a), which lies close by the equator, the first,
then one diametrically opposite to it would mark the centre of a
small interruption in the fringe, and also give the position of an
organ (Figs. 1, 2 o) to which a nerve is joined (1, 2 p) that may be
traced straight to the brain, and runs along the aboral hemisphere
in a great circle. The anus, its circular edge slightly swollen
(1.2 g), is situated almost exactly at the oral pole ; and the two
simple eyes (1,2 m) are so placed on the circular equatorial fringe
that a great circle passing through them and the anus cuts the
first meridian connecting the mouth and the problematical sense-
organ at right angles. Thus the mouth and the eyes exactly
divide the equatorial fringe into four quadrants.

The remaining organs, distinguished by their points of junction
with the outer skin, are so situated that the mathematical symmetry
becomes considerably disturbed by them. First of all on either
side above the eye, and at the same time rather farther towards
the mouth, we have two organs (1,2 n), which both by reason of
their connection with nerves as well as in form and appearance
correspond exactly to the already mentioned problematical sense-
organ. Farther on towards the mouth is a wide, ribbon-like

The Monthly Microscopical Journal. Nov. L .187 5. Pl.CjjXXll.

WWeertfcCo.sc

y,6o.h.

IrockospliKra. sequa-t onaJis .

Trocliosphsera eequaforialis. By Herr Semper. 239

organ (1 T) taking its rise, with a broad edge, from a flat hollow on
the oral hemisphere close under the skin, but free in the cavity
of the body ; it lies obliquely under the equator, then crosses into
the aboral hemisphere, and here fastens itself to the skin by means
of a number of thin filaments. Besides the nerve already men-
tioned, this is the only organ which in part lies in the aboral
hemisphere. I now pass on to a particular description of the
several organs.

As regards the histologic composition of the skin, I can give
but little information, I am sorry to say. On the whole it is very
thin, yet the cuticle is tolerably resistent, and can still be observed
in animals preserved since 1859 in glycerine. It is only at the
equatorial fringe that any noteworthy thickening appears (Fig. 6).
Here I could easily detect two layers, which will no doubt allow of
being taken for cutis and epidermis, although I have taken down
no written notes on their connective or cellular nature. With the
exception of the circular fringe and a second small fringe leading
to the mouth, the skin is perfectly free from hair. A real layer of
skin muscles is entirely wanting. The circular fringe itself is, as
already said, interrupted at one place (6b) diametrically opposite
the mouth, yet only partially interrupted. Whilst the fringed arc
on each side ends in a blunted point (6 a, a'), both these are joined
by a narrow bridge (6 b), which shows the same two layers as the
circular fringe itself, but is thinner and has no cilia. The cilia of
the equator are tolerably long, and under the microscope exhibit
the motion belonging to all snail larvae, but no rotatory phenomenon .
Still, through its relation to the second small fringe leading to the
mouth (3 o), it is proved that this equatorial fringe really is the
homologue of the rotatory organ of the Rotatoria. It further
follows that the aboral hemisphere corresponds to the flat part
situated between the creeks made by the fringe in Floscularia, i. e.
to the forehead, whilst the oral corresponds to the real body of all
other footed and footless Rotatoria. It thus becomes impossible to
denote the parts of the body in a way that would apply to all the
different forms of Rotatoria.

The muscular system is very meagrely developed. Besides those
which, situated at the pharynx and at the head of the pharynx,
belong to the tractus, undoubtedly developed muscles are only
found at the mouth and anus. Two broad muscle-bands at the
head of the pharynx, which have places of junction with skin in
the oral hemisphere, have a forward pull (3 m, m). A single
(unmatched) muscle in the oral hemisphere acts as suspensory
ligament to the oviduct and anus, both of which it joins simul-
taneously (9 m). The muscles are smooth, and of a yellow trans-
parency. Probably the two broad ribbons mentioned above, which
lie in the two quadrants nearest to the mouth yet connect the

VOL. xiv. s

210 Trochosphsera sequatorialis. By Kerr Semper.

oral hemisphere with the aboral (1 1, 4 1), belong to this point.
With a broad end each joins to a hollow in the oral surface
(4 b), then close under the skin, hut yet suspended freely in the
corporal cavity, it passes under the equatorial fringe and fastens
itself (4/) to the aboral hemisphere by a number of long, thin
filaments, which in their course are divided up and join the skin
with ends somewhat broader. I have never noticed contractions
of these ribbons : yet in appearance they correspond to the pharyn-
geal muscles. Among them some nerves (which shall he described
immediately) pass along, which are partly lost in them, in the part
nearest to the hollow of junction.

The central nerve-system consists of a large brain-ganglion,
lying over the pharynx (if the aboral hemisphere is regarded as the
upper, i. e. as the forehead), with deep inlets in front and drawn
out into large points towards the hack in the middle as well as on
the sides (3 g). Altogether five pairs of nerves leave the brain,
and one single (unmatched) nerve from the middle point behind (6).
The first two (3 — 1, 2) pass, the first to the opening of the mouth and
the head of the pharynx, the second to the front part of the circular
fringe. The third nerve with the fourth arise in common from a
lengthening of the brain, still they separate so soon that they cannot
he regarded as branches of the same nerve. At first they run
almost parallel till they reach the problematical muscle-layer and
its hollow (4 b, c ). Here it seems they both send off branches
into this organ, but both pass on under it in their main branch.
Then they separate ; the third nerve turns suddenly downwards at
an obtuse angle, i. e. up towards the oral hemisphere (1 n; 4 — 3 b)
and passes into a problematical organ (1 n), that will be more
minutely described immediately. The nerve No. 4 divides into
two branches immediately behind the muscle-band (4 a and b),
which, passing on close by one another, end near the circular fringe
in the eye and in a problematical organ lying close by this. The
fifth nerve (3 — 5) begins at a short cylindrical appendage of the
brain, passes across the cavity of the body, and joins the end of
the organ of excretion, which will be described later on. Lastly,
the sixth single nerve crosses the equator — differing in this from all
the remaining nerves that lie in the oral hemisphere — then exactly
at the meridian it passes close under the skin of the aboral hemi-
sphere (1 p), again crosses the equator opposite the mouth (1 q) —
at least in its main branch — after first (6/) exhibiting a ganglion-
like swelling of one cell, sends out on the sides symmetrical branches
towards the encircling fringe which just here is interrupted (6 g ),
and at last through the said main branch passes into a peculiar
organ (6 h) lying on the oral surface.

Of the organs of sense the eye is easily found. It hes close by
the equatorial fringe (1 m ), and, in conjunction with the mouth and

241

Trochosphsera seqiiatorialis. By Herr Semper.

the break in the fringe, divides it into four quadrants exactly. The
optic nerve is the one branch of nerve No. 4 (5, 4 a) ; this swells
into a very lengthened club-shaped ganglion (5 c ) ; close upon it
stands the eye furnished with a round lens (5 h) and with a semi-
spherical covering of pigment closely enveloping it (5 b). The
second branch of the same nerve also swells into a ganglion (5 d)
situated near the eye-ganglion ; in this, however, in spite of all my
pains, I could find no particular final organs or elements, which
might have explained the meaning of this organ.

Just as little do the other already mentioned final organs of
nerves 3 and 6 allow of a certain explanation. The two nerves 3
bend round, as I have already said, behind the muscle-layer to the
anal pole and end here (1, 4 3 b), crossing the canals of the organ
of excretion (7), in an oval swelling (7 e) with a number of large
ganglion-cells and a very small bright body of dark contour {If),
which is situated on the rather pointed end of the ganglion, and rises
close upon the skin. Whether a fine hair (for feeling or hearing
perhaps ?) is upon it, I could not distinguish, having no immersion
lens. Quite similar too is the structure of the final organ of the single
nerve No. 6 (6 h). The ganglion is here less large, deeply indented,
and contains ganglion-cells both fewer and smaller ; on the blunt
end, rising close upon the skin, the bright extreme body is here too
found, as in the two other organs. Even though a more minute
specification of the nature of these bodies is impossible, yet there
can be no doubt, after the description just given, that they belong
to that series of sense-organs, still somewhat problematical, which
have lately engaged such especial attention. One may well think of
the pedunculated sense-organ situated behind the forehead in many
Botatoria, and, as is well known, more minutely described by Leydig ;
its position too allows it to be treated as homologous with these, for
the three organs of the Trochosphasra all belong to the oral surface,
and do not therefore lie on the forehead, but outside the circle of
fringe : just as in the case of Rotifer {vulgaris), &c., the organ adduced
does not lie on the surface of the rotatory organ — the forehead —
but behind it. For the rest, the morphological comparison of sense-
organs, at least in the case of animals without a vertebra, is always
unsatisfactory, since it is well known that among them organs
physiologically equivalent — eyes, ears, Ac. — may often occur in
the most various parts of the body, that can be by no means mor-
phologically compared together. I will only instance here the
most striking example, the occurrence of eyes on the belly of
Euphausia ; a discovery, however, which was not, as Gegenbaur
in the second edition of his Comparative Anatomy wrongly states,
first made by Claus, but by me.

Close under the equatorial fringe lies a small indented fringe of
hair (3 o) which leads into the hollow of the mouth and serves only

s 2

242 Trocliosphasra aequatorialis. Bij Herr Semper.

for the introduction of food, whilst the first is only a rotatory
organ.

Claparede, the excellent zoologist of Geneva, whose early death is
much to be deplored, lately showed that this mouth fringe occurs
in all other Rotatoria as well. The mouth is succeeded by a funnel-
shaped thickly fringed cavity, joined by the mastax (lb) furnished
with the characteristic jaws of the Rotatoria (8). With this mastax
is connected a longish, thin pharynx (1 d), which passes straight
inwards, and at the place of passage into the stomach itself (1 e)
gives rise to two gastric glands (1 r), such as occur in other Rotatoria
in the same place. The thick hair in the pharynx is in the direc-
tion of the stomach. The latter is broad, cylindrical, and has a
thick coating formed by large colourless cells ; it stretches a‘ little
over the (1 e) middle of the oral hemisphere, turning a little
towards the aboral, then bends sharply round and passes in a
straight line towards the anus. The last part of the intestines,
that can be perfectly separated from the small final intestines (9 a)
by a muscular sphincter, must be considered as the cloaca (1/, 9 c),
since the excretory ducts (9 n, n) as well as the simple oviduct
(9 e ) and a contractile vesicle are in connection with it. The final
intestine is thickly covered with hair as well as the stomach ; the
direction of the hairs in the former is towards the latter.

Although the contractile vesicle at the cloaca certainly is no
continuation of the two excretory ducts, yet I suppose it must be
compared with the excretory bladder of the other Rotatoria. Its
contents are always of a glassy brightness, it is free from cilia, and
its contractions are not rhythmical, their duration being between
five and fifteen seconds. The contraction takes place by jerks.
Although the colourless contents of the bladder cannot be followed
farther in its motions directly, yet from conditions of contraction or
expansion of the cloaca and intestines connected with the narrowing
of the bladder, we may conclude that the liquid coming from that
bladder does not — or at any rate does not always — empty itself
away, but passes straight into the stomach. For upon every con-
traction of the bladder an expansion of the cloaca immediately
follows, and on the close of the latter immediately, with perfect
regularity, an opening of the sphincter of the final intestine occurs,
and an expansion of the latter. The expansion of the cloaca is not
simultaneous in all its parts ; but the part of it where the bladder
leads into it is first expanded, and the expansion then is propa-
gated in waves till the commencement of the intestines, and passes
on into this in the same way. This always takes place whilst the
anus is perfectly closed. The coats of the intestines and cloaca
remain expanded a short time, that of the first for a longer time
than that of the latter, which soon falls together again. Lastly, if

Trochosphsera sequatorialis. By Herr Semper. 243

the intestines are contracted, the sphincter immediately closes, com-
pletely separating it from the cloaca.

Though I have never observed an opening of the anus after a
contraction of the bladder, hut, on the other hand, have noticed the
contractions and expansions as described above in the case of many
specimens, and in the same individual specimen for a long time,
yet I will not assert that the contents of the bladder are not at
times transmitted to the anus. Still, from what has been said
above, I think it certain that it is far oftener driven back into the
stomach instead of being emptied away. If then the liquid from
the excretory organ really gets into this bladder — as is probable
— it would follow that it cannot be considered pure excrement ;
it must, on the other hand, be regarded as in a certain way necessary
or serviceable a second time for the nourishment of the creature,
since in the manner described it is again driven back into the
resorbent apparatus. The so-called excretory organ then is not
what its name implies, at any rate not entirely such ; and thus this
organ — physiologically regarded — would be intimately connected
with the kidneys of the molluscs, i. e. of those living in water, in
the case of which this organ undoubtedly serves for passing water
into the blood. The excretory organ is double, as usual, and
exhibits the well-known formation of this organ in Rotatoria. At
the cloaca begin the two ducts (1 k) in such a manner as to be
situated pretty nearly in the meridian plane passing through the
two eyes ; they then bend forwards towards the mouth, and at the
same time towards the equator, and pass under the muscle-band at
the side into the glandular part. The duct has a coat of con-
siderable thickness (7 a) ; beneath the muscle it divides off, and
quickly swells to the two irregularly formed glandular flaps (7 b, b )
in which the upper part of the canal winds. Each glandular flap
passes into the two ciliated channels (7 c), which exhibit four or
five of the characteristic ciliated tags rising upon them (7 g). At
cl the two channels c cross ; here one of the two must end or they
become joined ; for from this place only a single channel c can be
traced up to the before-mentioned nerve 5 ; by this it is held fast.
In this last section a single ciliated tag occurs.

Of the sexual organs I only recognized the female. They are
exceedingly simple ; from a single ovary a thin oviduct takes its
rise (1 A and i). The ovary (1 h, 9) is a flat band, rather broad,
which is situated close above the equator in the two back quadrants
away from the mouth (2 h) ; with its flat surface it places itself
along the skin through almost its whole length, only the free end
bends away a little (2/i), as also does the end from which the
oviduct originates (2 i). The whole band of the ovary is filled
in its undeveloped state with small granular cells, three or four of

244 Trochosphsera sequcitorialis. By Herr Semper.

which make up the width of the band (9 o o). As the animal grows
older this stretches itself lengthwise, the cells arrange themselves
in a single row, so that the breadth of the ovary, i. e. at the end
belonging to the oviduct, is always filled up by a single egg (10/).
Of the small nuclei (9) originally round, constituting the un-
developed eggs, which afterwards were no longer recognizable by
their varying contours, the star-shaped ones (10 /) grew large ;
the eggs themselves, although without any covering, separated
themselves sharply from one another, especially towards the oviduct.
This is uncommonly delicate, but capable of stretching to an extra-
ordinary extent ; it is formed directly by the lengthening of the
exceedingly thin tunica propria of the ovary, and appears not to
possess an epithelium. It joins the cloaca (9) so as to be just in
the middle (1) between the points of junction of the excretory
ducts.

As soon as the egg passes into the oviduct, the nucleus con-
tracts to a round bladder (10 b) ; but even here no egg-skin forms
itself. Then it reaches the cloaca (10 a) without an egg-shell being
formed even here, and here it develops into a young animal, which
corresponds exactly to the mother in all particulars, even in the size
and manifest separation of several inner organs (11). At the
beginning of my investigations, October 14-16, 1859, I found a
number of specimens with developed eggs in the ovary and oviduct,
but only occasionally one with an egg in the cloaca. From October
18-20 all the larger specimens had eggs already developed, with
generally one in the cloaca, sometimes two, in one case even three ;
then they were always in different degrees of development. Lastly,
from October 25 to the beginning of November almost nothing but
young. Development then seems to progress exceedingly rapidly,
as was to be expected from the high and uniform temperature
of the streams in the Philippine Islands.

My reason for calling these female was because the principle
of the contrast formerly supposed between the real egg and the
germ (ovum and pseud ovum) cannot be maintained unswervingly
according to the latest investigations on parthenogenesis. I cer-
tainly believe that I only discovered female Trochosphaera, which
multiplied by parthenogenesis ; for in all the hundreds of speci-
mens which I observed, I never succeeded in discovering undoubted
males nor zoosperms in the cloaca of specimens containing eggs.
A short time after making these observations I was obliged to
leave Zamboanga ; and on returning three months later, and look-
ing for my Trochosphaera in the same ditches, I could not find a
single specimen. If we might suppose that in this interval sexual
generation had begun, the succession of the two modes of genera-
tion there would correspond to ours here, i. e. in the heat of summer
parthenogenetic generation, on the approach of the cold season

Translation of Professor Abbe’s Paper on the Microscope. 245

sexual, the germs of which, there as here quiescent in the mud,
wait to he revivified by the increasing warmth of next year’s sun.
Unhappily I never succeeded in again discovering the Trocho-
sphaera either at Manila or on Bohol, so that I must leave it to
future visitors of Zamboanga to solve the questions here proposed,
and to discover really sexual specimens of this the most interesting
of all liotatoria, — Siebold and Kolliker’s Zeitschrift, drittes Heft.

Y. — Extracts from Mr. H. E. Fripp’s Translation of Professor
Abbe's Paper on the Microscope.

(i Continued from p. 201.)

The undulation theory of light demonstrates in the phenomena
of diffraction a characteristic change which material particles,
according to their minuteness, effect in transmitted rays of light.
This change consists, generally, in the breaking up of an incident
ray into a group of rays with increased angular dispersion within
the range of which periodic maxima and minima of intensity (i. e.
alternation of dark and fight) occur. But these angular distances
are for each colour proportional to its wave-length, and increase,
therefore, in size from violet to red, and are also inversely propor-
tioned to the distances between the particles in the object which
cause diffraction.

This effect, which is not only such as might be theoretically
predicted, but also capable of exact calculation, may be readily
observed. Having placed some object of the kind in question
under the microscope and got its detail in focus, the ocular must be
removed and the image of the object in the open tube viewed with
the naked eye, or a suitably arranged microscope of weak power
(t* to r°) which can be let down in the tube to the upper focal
plane of the objective. The image of the mirror or whatever illu-
minating surface may be used will be seen as it is formed by the
undiffracted rays, and surrounded by a greater or less number of
secondary images in the form of impure coloured spectra, whose
sequence of colours, reckoning from the primary image, is always
from blue to red. Objects consisting of several systems of fines
which cross each other show not only a series of diffraction images
of each group in the direction of then perpendicular, but also other
additional series in the angles between the perpendicular groups.
Insect scales and diatom valves exhibit these phenomena in the
greatest variety.

This method of direct observation of pencils of fight coming
from the object enables us to determine by experiment what part

246 Extracts from Mr. E. E. Fripps Translation of

is played by diffractive phenomena in forming the image of the
structure in question. A suitable test-object being placed in focus,
and the light being suitably regulated by diaphragms placed imme-
diately above the objective, as closely as possible to its upper focal
plane, for the purpose of excluding at will one or another portion
of the groups of rays exhibiting diffractive effects, the image of the
preparation, as formed by those rays only which were not so shut
off, could be readily observed with the ordinary ocular. The imme-
diate result of experiments carried out in this manner was as follows,
it being first premised that every trial was made with very correct
low-power objectives (1^ to J inch) and corresponding weak ampli-
fication : Higher powers, an immersion lens of inch in particular
being used only to control the results obtained already with coarse
objects, by experiments on the finer diatoms. The preparations for
all decisive trials were of such a kind that their structure was
accurately known beforehand, system of lines scratched in glass,
whose linear distance varied from inch to ttutt inch ; similar
groups of lines ruled on silvered glass, the silver coating being
immeasurably thin; groups of lines crossing each other without
any difference of level were obtained by laying upon each other two
glasses, the surface in contact being separately ruled.

The facts thus ascertained are —

(i.) When all light separated from the incident rays by diffrac-
tion was completely shut off by the diaphragm, so that the image
of the preparation was formed solely by the remaining undiffracted
rays, the sharpness of outline at the confines of the unequally trans-
parent parts of the field was not affected, provided the opening of
the diaphragm remained sufficiently large, so that no diffraction
arising from the reduction of its opening should occasion any visible
lowering of the “ necessary amplification ” ; nor will the clear recog-
nition of separate structural particles be sensibly hindered, provided
that not more than 30 to 50 of such particles are found in inch.*
But the more this number is exceeded, so much the more of detail
disappears; so that when the fineness of detail reaches 100 parts to
the millimeter (that is, when their interspace is only -2-5J0o inch)
nothing remains visible except a homogeneous surface whatever
magnifying power be used, or whatever mode of illuminating
(direct or oblique). Even a couple of fines ruled on a glass will,
under the circumstances above stated, be not otherwise distinguish-
able than as one broader line with sharp outlines. With the most ,
powerful immersion lens nothing at all can be seen of the markings
of Fleurosigma angulatum, and even the coarse lines of Eipparchia
Janeira remain unrecognizable with a power of 200. In the case

* The definition of number is here uncertain, because the exclusion of dif-
fracted rays, whose diffraction is slight, can only be obtained by using a diaphragm
pierced with small openings.

Professor Abbe’s Paper on the Microscope. 247

of granular objects and other irregularly shaped particles, diffracted
light cannot be completely separated from undiffracted light, and
accordingly there is no absolute disappearance of all the particles ;
but such indefiniteness of image ensues that the finer particles of
the preparation fuse into a homogeneous grey cloud.

(ii.) When all light is shut off, excepting a single pencil of
diffracted rays, a positive image of the particles in the object which
caused the diffraction is formed, and appears more or less brightly
on the dark field, but without any detail. Ruled lines appear as
uniformly clear flat stripes on a dark ground.

(iii.) But when not less than two separate pencils are admitted
the image always shows sharply defined detail, whether it appears
in the form of system of lines, or of separate fields ; nor does it
matter whether undiffracted light passes in with the incident cones
or not : that is to say, whether the image appears on a bright or a
dark field. If fresh pencils be set in operation fresh details appear,
but always different, according to the degree of minuteness, or to
the nature of the markings; and this detail is not necessarily
conformable either with that of the image as seen by ordinary illu-
mination, or with the real structure of the object as known or
ascertained in other ways. In respect to this last point the follow-
ing particulars are noteworthy.

(iv.) A simple series of lines will be always imaged as such
when two or more illuminating pencils are set in operation, but the
lines will appear doubly or trebly fine when, instead of the pencils
being consecutive in order of position, one, two, or more intervening
pencils are passed over. Thus a group of two lines only in the
object appears as if composed of three or four separated sets. The
phantom lines thus created cannot be distinguished by help of any
magnification from the normal image of actual lines of double or
treble fineness, either in respect to sharpness of definition or con-
stancy of appearance, as may be shown by a conclusive experiment,
in which namely, the falsely doubled image appears side by side with
the image of an object actually ruled with lines of double fineness.

(v.) When two pieces of simple lattice cross each other in the
same plane at any selected angle, the systems may, by suitable
regulation of the admitted pencil of light, be rendered visible
together or separately, and by varying the form of illumination
numerous fresh systems of lines and variously figured fields which
do not exist at all as such in the object may be made to appear with
equal sharpness of delineation. These new systems of lines always
correspond in position and distance from each other with the pos-
sible forms in which the points of intersection of the real lines of the
object may arrange themselves in equidistant series.

With a network crossing at an angle of 60°, there appears,
besides several smaller systems of lines, a third set marked just as

248 Extracts from Mr. E. E. Fripp's Translation of

strongly as the real network of the object, and with equal distance
between the lines, inclined also 60° to the others ; and when the
three sets are seen together there will he seen perfectly sharply
defined six-sided spaces (fields) of the kind observed on Fleur o-
sigma angulatum, instead of the rhombic fields. It may be added
that all the appearances unconformable with the structure of
known objects which are here described were observed with exactly
the same focussing under which the normal image appeared well
defined, and that they occurred under various combinations of ob-
jectives and oculars with regular constancy whenever the illumina-
tion was regulated in the same way.

The constant increase of resolving power resulting from oblique
illumination, and the greater prominence of what was before visible
with central illumination, is in every instance solely produced
either by the entrance of diffracted rays into the larger aperture
(with oblique illumination), which would otherwise not have en-
tered into the objective on account of their greater divergence, or
because diffraction pencils which were but imperfectly taken up
when direct illumination was used now enter more completely and
work with greater effect, whilst the direct rays are relatively less
operative.

The facts here recounted appear sufficient, when taken in con-
nection with incontestible laws of the theory of undulation, to
warrant a series of most important conclusions which affect the
doctrine of microscopic vision, as well as the composition and mani-
pulation of the microscope.

Firstly, as respects the vision of objects under the microscope.
Any part of a microscopic preparation which, either from its being
isolated, or from its relatively large dimensions, produces no per-
ceptible diffracted effect, is delineated in the field of the microscope
as an image formed according to the usual dioptric laws of rays
concentrating in a focal plane. Such an image is entirely negative,
being dependent on an unequal transmission of light which partial
absorption of the rays (e. g. coloured rays), or divergence of the
rays (from refraction), or diffraction of the rays (produced by par-
ticles of internal structure), severally occasion. The absorption
image thus produced is an unquestionable similitude of the object
itself , and if correctly interpreted according to stereometric rules,
admits of perfectly safe inferences respecting its morphologic con-
stitution. On the other hand, all minute structures whose elements
lie so close together as to occasion noticeable diffraction phenomena
will not be geometrically imaged, that is to say, the image will not
he formed, point for point, as usually described by the reunion in
a focal point of pencils of light which, starting from the object,
undergo various changes of direction in their entrance and passage
through the objective.

Professor Abbe's Paper on the Microscope. 249

Now to anyone who clearly realizes in his own mind what are
the assumptions upon which a similitude between an object and its
optical image is commonly accepted, the foregoing facts must
suffice to lead to the conclusion that, under the circumstances above
indicated, such acceptance is a purely arbitrary supposition. As a
positive instance of the contrary stands the conclusion to which
experiments lead by rigorous deduction, namely, that different
structures always yield the same microscopic images as soon as the
difference of diffraction effect connected with them is artificially
removed from the action of the microscope ; and that similar
structures as constantly yield different images when the diffractive
effect taking place in the microscope is artificially rendered dis-
similar. In other ivords, the images of structure arising from the
operation of the diffractive process stand in no constant relation
with the real constitution of the objects causing them, but rather
with the diffraction phenomena themselves, which are the true
causes of their formation. As this is not the place to enter into a
physical exposition of such phenomena, it may suffice to say in brief,
that the conclusions here deduced from facts won by direct observa-
tion, are fully substantiated by the theory of undulation of light,
which shows not only why microscopic structural detail is not imaged
according to dioptric law, but also how a different process of image
formation is actually brought about. It can be shown that the
images of the illuminating surface, which appear in the upper
focal plane of the objective (the direct image and the diffraction
images), must each represent, at the point of correspondence, equal
oscillation phases when each single colour is examined separately.

The delineation of structure seen in the field of the microscope is
in all its characters, — those which are conformable with the real
constitution of the object as well as those which are not so — nothing
more than the result of this process of interference occurring where
all the image-forming rays encounter each other. The relation
existing between the linear distances from the axis of the micro-
scope of constituent elements of the aperture image, and the
various inclination of rays entering the objective, taken together
with the dioptric analysis of the microscope, afford all the data
necessary for complete demonstration of the above positions. From
them may be deduced that in an achromatic objective the inter-
ference images, for all colours, coincide, and yield as a total effect
achromatism, thus differing from all other known interference
phenomena.

The final result of these researches may be thus stated :

Everything visible in the microscope picture which is not
accounted for by the simple “ absorption image,” but for which the
co-operation of groups of diffracted rays is needed — in fact all
minute structural detail — is, as a rule, not imaged geometrically,

250 Extracts from Mr. H. E. Fripp's Translation of

that is, conformably with the actual constituent detail of the object
itself. However constant, strongly marked, and so to speak
materially visible, such indications of structure may appear, they
cannot be interpreted as morphological, but only as physical
characters ; not as images of material forms, but as signs of certain
material differences of composition of the particles composing the
object. And nothing more can be safely inferred from the micro-
scope revelation than the presence, in the object, of such structural
peculiarities as are necessary and adequate to the production of
the diffraction phenomena on which the images of minute details
depend.

From this point of view it must be evident that the attempt to
determine the structure of the finer kinds of diatom valves by
morphological interpretation of their microscopic appearances, is
based on inadmissible premises. Whether, for example, Pleurosigma
angulatum possesses two or three sets of striae ; whether striation
exist at all ; whether the visible delineation is caused by isolated
prominences, or depressions, Ac., no microscope however perfect,
no amplification however magnified, can inform us. All that can
be maintained is the mere presence of conditions optically necessary
for the diffraction effect which accompanies the image-forming
process. So far. however, as this effect is visible in any microscope
(six symmetrically disposed spectra inclined at about 65° to the
direction of the undiffracted rays, ordinary direct illumination being
employed), it may proceed from any structure which contains in its
substance, or on its surface, optically homogeneous elements arranged
with some approach to a system of equilateral triangles of 0 • 48/r
dimensions ( = circa ^hro inch). Whatever such elements may
be — organized particles or mere differences of molecular aggregation
(centres of condensed matter) — they will always present a delineation
of the familiar form. All ground for assuming these elements to
be depressions or prominences fails, after proof that neither the
visibility of the markings nor their greater distinctions under oblique
illumination has anything to do with shadow effects. The dis-
tribution of light and shade on the surface of the valve in the form
of a system of hexagonal fields, is the mathematically necessary
result of the interference of the seven isolated pencils of light which
is caused by diffraction, whatever may be the physical condition of
the object causing this diffraction : the position of the hexagonal
fields, with two sides parallel to the middle ribs, has its sufficient
reason in the visible disposition of the diffracted spectra towards
the axis of this valve, and can be deduced by calculation without
any necessity for knowing the actual structure of the object.

That the same state of things obtains in numerous instances of
organic forms, the study of which belongs to the province of
histology, we may learn from the instance of striated muscular

Professor Abbe's Paper on the Microscope. 251

fibre. The manifold changes in the characters of the images which
present themselves account, to a certain extent, for the notorious
discordance between the representations of different observers.

In connection with the foregoing conclusions, which have an
important bearing on the scientific application of the microscope, it
appears, further, that the limits of “ resolving ” power are deter-
minate for every objective and for the microscope as a whole.

No particles can be resolved when they are situated so closely
together that not even the first of a series of diffraction pencils
produced by them can enter the objective simultaneously with the
undiffracted rays. As even with immersion objectives the angular
aperture cannot, by any possible means, be increased beyond the
degree which would correspond, in effect, to 180° in air, it follows
that whatever improvement may be effected in regard to serviceable
magnifying power, the limit of resolving power cannot be stretched
sensibly beyond the figure denoting the wave-length of violet rays
when direct illumination is used, nor beyond half that amount when
extreme oblique illumination is used. The last limit is, in point of
fact, already reached by the finest lines of the Nobert plate and the
finest known markings on diatom valves, as far as seeing is con-
cerned. Only in the photographic copy of microscope images can
resolution of detail be carried any farther.

From these facts it appears that the microscope image — ex-
cluding two cases of a similar and exceptional kind — consists, as a
general rule, of two superimposed images, each being equally dis-
tinct in origin and character, and also capable of being separated and
examined apart from each other. Of these, one is a negative image,
in which the several constituent parts of an object re-present them-
selves geometrically, by virtue of the unequal emergence of light
which is caused by their mass affecting unequally the transmission
of the incident rays. This image may, for shortness sake, be called
the “ absorption image f because partial absorption is the principal
cause of the different amount of emergent light. It is the bearer of
the “ defining ” power, whose amount is determined by the greater
or less exactitude with which direct incident light is brought into
perfect homofocal reunion. Consequently, it is always the direct
light which “ defines,” no matter in what direction it arrives at the
objective, i. e. whether the central or peripheral zones of the objec-
tive receive it. But, independently of the “ absorption image," all
such parts of the object as contain interior structure will be imaged
a second time, and this time as a positive image, because these parts
will appear as if self-luminous, in consequence of the diffraction
phenomena which they cause. Now this “ diffraction image” is ma-
nifestly the bearer of “resolving” power, that is, the discriminating
or separating faculty of the microscope. Its development depends,
therefore, in the first and chief place upon angular aperture, in so far

252 Extracts from Mr. II. E. Fripp's Translation of

as this alone determines, according to rules above given, the limits of
its possible operation. But its actual amount will, at the same time,
depend upon the exactitude with which the partial images blend
together : for it is through this last act that the detail which indi-
cates the existence of positive structural elements in the object is
rendered visible. Now, inasmuch as these isolated pencils, whose
confocal reunion is the necessary condition of the formation of dif-
fraction images, occupy different parts of the aperture, and vary
constantly in position according to the character of the object and
the mode of illumination : it is obvious that a perfect fusion, in
every case, of the several diffraction images, and then an exact
superposition of the resultant “diffraction image” upon the “absorp-
tion image,” is only possible when the objective is uniformly free
from spherical aberration over the whole area of its aperture.

In consequence of the onesidedness with which, in modern
times, the improvement of the microscope has been directed towards
the increase of angular aperture, the conditions under which ab-
normal appearances, and especially deceptive alterations of level are
produced, occur abundantly in the new high-power objectives, as
repeated experience has shown me, and I assuredly do not err in
expressing my conviction that the consequences of this state of
things affect to an unexpected extent the numerous questions in
dispute amongst microscopists concerning the interpretation of
minute structures.

Since everyone must admit that the first and most imperative
claim which can be made, in the interest of scientific microscopy,
upon the performing power of the instrument is this — that parts
which belong together in the object shall also appear as belonging
together in the microscopic image, it follows that uniform correc-
tion of spherical aberration throughout the whole area of aperture
must be the absolute criterion and rule of guidance in the construc-
tion of a microscope. Now, it has been shown that with a dry
objective an adequate compensation of spherical aberration is, as a
matter of fact, impossible when the angular aperture exceeds 110°.
Hence it must be concluded that a dry objective will be less suited
for ordinary scientific use in proportion as it renders visible such
finer systems of lines as exceed the limits of resolving power
answering to that angle (namely, O' 35 /a for oblique light). The
greatest possible increase of resolving power can be obtained in a
rational way only by means of immersion objectives, as these alone
admit of the largest possible (i. e. technically practicable angular)
aperture, without contravening the very first requirement of cor-
rected spherical aberration.*

* The dry objectives made on Abbe’s calculations, founded upon the princi-
ples before explained, have only 105° to 110° of angular aperture for the highest
powers, and cannot pretend therefore to compete, in resolving diatoms, &c., with

Professor Abbe’s Paper on the Microscope. 253

A inode of testing which turns upon the determination of the
utmost limit of “ resolving power,” whether tried upon a “ Nobert ”
plate, a diatom, or an insect scale, brings into play a quite excep-
tional direction of rays of light into the microscope, such as is,
indeed, required for this purpose by the physical condition of the
problem. Theory and practice teach us that every objective which
is not a total failure — however imperfect in respect to correction of
spherical aberration — if its lenses be hut moderately well centered,
can always be made to work with one of its zones, e. g. the outer-
most, if during its construction it has been tried on a similar test.

The proof that an objective can resolve very minute striae on a
diatom or Nobert’s test-plate, attests, strictly speaking, nothing
more than that its angular aperture answers to the calculable angle
of diffraction of the interlinear distance of the striae on the test,
and that it is not so badly constructed that a sufficient correction
of its outer zone is impossible. A trial of this sort offers no means
of ascertaining what conditions for the correct fusion of aperture
images such an objective would present in the much more unfavour-
able case of the ordinary observing position. Nor can the result
be considered as sufficiently characteristic even of the “ resolving
power ” in its more general attributes.

Nor can the test of “ resolving power ” by direct light be
estimated at a much higher value. In the neighbourhood of the
limit of resolution corresponding to this form of illumination, all
direct light passes through the central zone, and all diffracted fight
through the peripheral zone of the aperture.

From the point of view presented by the theory here propounded,
another method offers itself, which, while employing the usual tests,
brings directly into fight the particular points which mainly in-
fluence the quality of performance during ordinary use of the
microscope. If it be desired to test, in a most critical way, the
conditions of exact co-operation of pencils of fight which pass
through every part of the aperture, there are truly no better means
than those afforded by natural objects of the diatom class and
insect scales, provided that the mere fact of accomplished “ resolu-
tion ” is not made the chief consideration, but that the exact consti-
tution of the total image produced by the objective is studied.

The considerations adduced lead to certain rules respecting the

objectives of much higher angle. The immersion lens is constructed with a free
aperture of about 100° in water, i. e. somewhat more than would correspond
to 180° in air, because this is attainable without serious disadvantage. Pro-
fessor Abbe is, however, convinced that even the immersion lens would not lose
any of its value for ordinary scientific purposes, whilst it would be materially
improved in many respects if its construction were based upon calculations for a
smaller aperture, “ but,” he adds, “ in view of this universally accepted standard
of valuation, the practical optician can scarcely be expected to trouble himself
about qualities of performance which would be very certainly ranked amongst
those of a secondary order ! ”

254 Translation of Professor Abbes Paper on the Microscope.

right proportion between focal distance and angular aperture,
which are opposed in many points to the hitherto prevalent
practice.

Since theory demands a limitation of angular aperture of 110°
for all dry combinations, the calculation of minutest detail accessible
to such objective is readily made ; and it may be shown that
if “ resolving ” power be not unfairly exalted at the cost of the
general excellence of the lens, there can be no question of detail
which a practised eye would not recognize with a good amplifica-
tion of from 4 to 500. Now according to the present standard of
technical constructive means, such an amplification may be gained
with an objective of 3 mm. (§- English inch), even if the attribute
good be interpreted a little more strictly than is often done. With
immersion lenses, the physical limit of “ resolution,” even where
the angular aperture is the highest attainable, does not extend so
far that an amplification of from 7 to 800 will not be fully equal
to it ; and this amplification would be gained with ease with a well-
constructed objective of TV inch focal length. It may be admitted
that an amplification exceeding the minimum here given as theoreti-
cally necessary, might greatly facilitate observation and render it
more certain if the additional amplification be as correct as can be
possibly made, although it would not occasion any new facts to be
seen. Yet one can scarcely estimate the significance of this empty
amplification far beyond the limits stated, and I therefore come to
the conclusion that the scientific value of an objective whose focal
length (if a dry system) is much shorter than TV inch, or if an
immersion system, than inch, is altogether problematical.

The actual powers of the microscope (in the strict sense of
correct and useful power) are, in my opinion, exhausted at these
limits, so long, that is, as no circumstances of moment are brought
forward which change the bearing of present theory. There exists
no microscope in which there has been seen, or will be seen, any
structure which really exists in the object, and is inherent in its
nature, that a normal eye cannot recognize with a sharply defining
immersion lens magnifying 800 times. Reports of extraordinary
performances (especially from England) of unusually high power
fa, inch ?) are not of such a character as to induce me to change
my opinion and lead me into similar error, for the superiority of
such lenses is said to have been proved upon objects to which the
results of my observations unreservedly apply, and which are said
to appear under such amplification as everyone who can understand
and give an account to himself of the optical conditions of such
performances must know to be wholly illusory. — From Proceedings
of the Bristol Naturalists' Society, New Series, vol. i., part 2.

( 255 )

PROGRESS OF MICROSCOPICAL SCIENCE.

Dr. Hudson's Paper on the Botifera. — Dr. Hudson’s paper at the
British Association gave an elaborate account of the structure and
affinity of these animals. There was considerable discussion upon the
author's views, some opposition being exhibited to his tendency to
group them with the Entomostraca. However, Dr. Hudson’s views
are the result of a considerable study of the group, he himself being
the discoverer of some very extraordinary novel forms.

An Animal-like Diatom. — The following letter has been addressed
to ‘ Nature’ (Oct. 14), by a gentleman who writes from Manila. The
cut has been kindly lent to us by the editor. The writer, Mr. W. W.
Wood, observes : — I have reason to think that I have made a dis-
covery which may change the ideas of naturalists as to the nature of
some diatoms. In collecting Diatomacete I have found a species of
Navicula (?) which is invested with a gelatinous envelope, and from
the edges of the frustule project a number of long processes or arms
of the same soft nature. These
vary much in number, in some
specimens being eight or ten, and
in others as many as twenty-five
or even more. They are longer
than the frustule, and radiate
from it with much regularity.

The diatoms when detected (upon
a floating fucus common in the
sea hereabout) were dead, and I
was unable to detect any move-
ments. I have examined so many
individuals of this diatom that I
think it hardly likely that I have
been deceived, as they are by no
means very minute. Dr. Car-
penter, in the fifth edition of his
admirable work on the Micro-
scope, speaks of some observa-
tions by Mr. Stephenson on the
genus Coscinodiscus, which hint
at the possibility of some diatoms
having appendages projected
through apertures of the frustule.

The highest power of my microscope is one of Messrs. R. and J. Beck’s,
-),th, a very fine glass. I propose to forward as soon as possible the
sticks, dry and in balsam, as well as the “ gathering ” in spirits, to a
competent diatomist, who will confirm my observations if correct.

The Origin of the Bed Clay found by the 1 Challenger. ’ — Dr. Car-
penter made some remarks of interest on this subject at the Bristol
Meeting of the British Association. He said that when it was first

YOL. XIV.

T

256

PROGRESS OF MICROSCOPICAL SCIENCE.

found Dr. Wyville Thomson thought ho could trace it to some great
river, such as the Amazon, or to the fine deposit brought down by
somo great river ; but he found on further research that he did not
get it near the land, for where the water shallowed he did not get it,
and he came to the conclusion that it could not be accounted for by
any river action whatever. He then formed an idea that it might be
what lie called the ash of the shells of the Foraminifcra, which was
now believed to be diffused in enormous masses over the whole bottom
of the deep Atlantic. There was first on the surface what Dr.
Carpenter believes to bo living Globigcrimc ; then, below that, what
was called ooze, in which not so much the shells as fragments of
them wero found, and a large quantity of white impalpable matter,
forming a very fine white mud, which was certainly the result of the
gradual disintegration of the shells. Then at further depths below
that, Dr. Thomson, finding this red mud, formed the hypothesis that
at great depths there was an excess of carbonic acid, and under great
pressures with this excess of carbonic acid the calcareous portion of
the shell was dissolved and any mineral matter that was not calcareous
was left behind. This mud silicate of iron and alumina was analyzed,
as also a portion of the ooze, when it was found by Dr. Thomson that
after removing the. calcareous portion and dissolving it by dilute acid,
a residue of the same kind was obtained, namely, silicate of iron and
alumina, and upon that basis he put forward the speculation that this
red ash was simply the ash of the shells of these Globigerinae and Fora-
minifera. It seemed to the lecturer that this was not the most likely
explanation of it. In the first place he had no reason to believe that
any ash at all was left behind when the pure shells were dissolved in
dilute acid. He believed they would give as pure carbonate of lime
mixed with animal matter as could be obtained anywhere. But then
another source occurred to him. It was shown many years ago that
most green sands occurring in all geological periods from the Silurian
downwards, when examined by the microscope, were found to be
really internal casts of Foraminifcra. In consequence of this dis-
covery, and of the discovery by the late Professor Bailey, of New
England, that the same thing was found in recent Foraminifera, Dr.
Carpenter and others associated with him found exactly the same
thing with foraminiferous forms, namely, that by dissolving away
the shell, they could get in some instances green silicates, and in
other instances ochry silicates, giving the form of the animal.
Chemists all agreed that this deposit took place by a process of
chemical substitution, although they were not all agreed as to the
precise mode in which it occurred. They all agreed, however, that
it was through the decomposition of the animal that the silicates were
precipitated from sea water, and that they took the place of the
animal substances particle by particle, filling completely the cavities
of these minute shells with green or ochry silicates, and thus giving
perfect models of the animal. Among Admiral Spratt’s dredgings in
the ‘ iEgean ’ it happened that Dr. Carpenter had some internal casts
which were a bright red, and also some which showed the transition
from green to oclireous — a green core and a sort of ochreous eftlores-

NOTES AND MEMORANDA.

257

cence on the surface. On another of Admiral Spratt’s specimens
there was a transition from green to red — that is, in the very same cast
he found red in one place and green in another. It occurred to him
that it was not improbable that this was the real origin of the red
clay. He thought he might say it pretty certainly — and he said it on
the authority of Professor Hofmann, who had gone carefully through
his series — that these three colours, the green, the ochreous, and the
red, were simply dependent on the stages of the oxidation of the iron.
They could not be analyzed, because they were so excessively minute.
He might mention that the ‘ Challenger,’ near the Cape of Good Hope,
came upon a bed of green clay, which was found to be entirely com-
posed of these internal casts, and when that came home materials
might be expected for a very thorough chemical analysis of these very
curious formations. His own suggestion was that this red clay was
not the ash of the shell, hut the result of the disintegration of internal
casts. He thought it not at all improbable that what was originally
green or ochreous was acted upon by carbonic acid, just in the same
manner as every chemist knows that felspar was decomposed by
carbonic acid ; so that in the carbonic acid of the deep strata of the
ocean, under the influence of pressure especially, there would be a
decomposition or disintegration of these internal casts, and a higher
oxidation of the iron giving it the red colour. It appeared to him
that that was far more likely to be the origin of this red clay than
its being left as an ash from the foraminiferous shells, which, as far
as he had examined them, did not leave any ash at all. That Dr.
Thomson should find a residue in the ooze was likely enough, because
if some of these internal casts were formed in the Foraminifera layer,
when all the decomposed shells were dissolved there would of course
be the residue of these casts. It would be curious if it was referable
to the Foraminifera at all. It was referable rather to the process by
which the internal casts were formed, and the higher oxidation of the
iron of them, and the disintegration formed by the action of the
carbonic acid so as to form this deposit of red clay at the bottom.
This seemed to him more likely than that it was formed by the
solution of the foraminiferous shells themselves.

NOTES AND MEMOKANDA.

Use of the Microscope in Mineralogy. — A paper on this subject
was read before the San Francisco Microscopical Society, and it
appears reported in full iu the ‘ Cincinnati Medical News’ (September).
He uses the binocular instrument and a 7f-incli objective, and he
makes the following remarks on the subject of preparing and ex-
amining specimens : — My method of preparing them is as follows :
The slide is placed on a card of the same size, upon which a dot of
ink has been made to indicate the centre. A scale of shellac is held

T 2

258

NOTES AND MEMORANDA.

in the flame of a spirit lamp ; when nearly dropping it is touched to
the glass over the dot. This ensures a central position for the object
when mounted. The slide is then heated over the spirit lamp until
the cement is liquid and the specimen placed on the melted shellac,
with the best surface uppermost. It is then gently pressed down and
the slide set aside to cool. It has then only to be labelled and placed
in the cabinet. Pulverulent minerals, small crystals, concentrated
washings, &c., are best mounted in cells and covered with thin glass
in the usual manner. In some cases the dust from powdered minerals
adheres to the glass cover if loosely mounted. In such cases I find it
better to coat the slide within the turned circle with gum arabic, in
rather thick solution. When dry, if breathed upon, the powdered
mineral will attach itself to the gummed surface. The glass cover
may then be replaced and cemented. Those minerals of which rocks
are composed, as, for example, albite, ortlioclase, mica, labradorite,
epidote, quartz, &c., should not only be mounted as opaque objects,
but also in thin sections, to admit of their being examined by polarized
light. The study of rocks by the aid of the microscope is growing
yearly in favour, and no geologist will now decide on the character of
a specimen without first submitting it to the optical test. To fully
understand the rocks, which are composite, the student must familiarize
himself with the optical properties of the minerals composing them.
He must learn to distinguish on the first turn of the polarizer the
difference between quartz and felspar, and to decide as quickly if the
felspar bo ortlioclase or albite. This can only be done by careful
study of minerals. For opaque minerals I find that the best illumi-
nation to be that produced by the parabolic illuminator, although the
large bull’s-eye condenser will be found to produce good effects when
the former apparatus is not at hand. The advantage of the illu-
minator is, that the light is thrown downward into the cavities of the
specimen, which are often filled with beautiful crystals. In trans-
parent sections in which opaque minerals are imbedded, the parabola
is indispensable. The most beautiful effects are often obtained by its
use. Thin sections should also be examined by polarized light ; the
details of the inner structure are by this means often brought out in
an unexpected manner. The microscope can hardly be dispensed with
in determinative mineralogy. If the mineralogist is called upon to
decide upon the fusibility of a mineral and finds the result doubtful,
he has only to strongly heat a thin fragment in the blowpipe flame,
and place it in the field of his instrument. If at all fusible the thin
edges will be seen to be rounded. A fragment of a mineral containing
alumina, if wet with nitrate of cobalt, and strongly heated, will often
show the prominent parts tinged blue under the microscope, when the
unassisted eye fails to distinguish the reaction.

( 259 )

CORRESPONDENCE*

On a New Form of Object-glass.

To the President of the London Microscopical Society.

Rue Mazarine, Paris.

Sir, — We have the honour (Mr. Thuet, ingenieur-opticien, of
Paris, 19, Rue Mazarine, and I, microscopist, of 113, Chaussee du
Maine) to offer you two new mechanical appliances for objectives
corrected for immersion. These appliances have suggested them-
selves to us from our desire to facilitate the cleaning of the optical

arrangement. Even using the immersion front with glycerine, it is
seldom that moisture does not pass the front lens into the correcting
lenses, and thus the frequent cleaning of the objective. We submit
our systems to the Society, and we will conform to the decision that
may be passed upon this new idea.

* Several letters are ‘‘crushed out ” of this number, but will appear in our next.

260

CORRESPONDENCE.

The above objectives are for various objects : the moisture has
very little tendency to collect in them ; but it is not the same in the
immersion working in various fluids. Also, would it not be an advan-
tage to get over this inconvenience by facilitating the cleaning of the
optical arrangement without unscrewing the collar ?

One of our systems is based upon the correction by Wenham,
adopted by Nachet and others ; and the other is based on the move-
ment alone of the last lens, or second corrective. The first is more
handy for quickness of adjustment, and the second offers greater
facility for the centering of the optical arrangement.

Fig. 1 represents my objective corrected by Wenham. A cone
fixed to the interior tube E E E E, into which are screwed the
corrective lenses A B, A B. The collar E F advances or withdraws
the front lens H from the two correctives. The front lens H is fixed
in a ring, screwed at 1 1 to the lower extremity of the exterior tube
Q Q Q Q, in the part G G of which is screwed the tube of the front
lens H. The correctives A A, B B screw into the cone of the interior
tube E E E E. When it is necessary to clean these, this tube must
be unscrewed as the piece G I, G I, then the two correctives A A, B B
from the cone C D. To clean the front lens H, the ring of the tube
G I, G I, in the centre of which it is fixed, must be unscrewed. This
operation does not necessitate any undoing of the collar E F.

Fig. 2 represents my new objective, with movement by the second
corrective. B B and D D represent the mounting of the front lens C,
and of the first corrective B B ; but the second corrective is mounted
in a screwed tube A S, A S, put in motion by the collar R R. The
optical arrangement is easily cleaned, without undoing the collar R R,
by first unscrewing the two lenses, placed under the second corrective
A A, the front and the first corrective.

This system appears to us more simple than the Wenham system.

Your obedient servant,

Clement Thuet.

[We insert the above as possibly containing an idea of practical
value, but it is so obscurely described that we fear our readers will
scarcely be able to comprehend it. — Ed. 4 M. M. J.’j

Professor Hasert’s New Objective.

To the Editor of the 4 Monthly Microscopical Journal

Denstone, Uttoxeter, October 3, 1875.

Sir, — Professor Hasert of Eisenach, who, as the readers of this
Journal will probably recollect, manufactured the lenses with which
Dr. Schumann performed those truly wondrous feats recorded in his
‘ Diatomeen der hohen Tatra,’ has been for a considerable time
engaged in devising an altogether novel species of lens, which will, I
expect, form an epoch in microscopy. The problem he proposed to

CORRESPONDENCE.

261

himself was to construct an objective which should completely satisfy
the conflicting requirements of scientific microscopists and of genuine
‘ Naturforscher,’ — which should be so absolutely perfect in its correc-
tion as to dispense with screw-collar adjustment for different thick-
nesses of cover, so as to work through a wide range of covering glass
without any perceptible deterioration of the optical image, and com-
bine the utmost beauty of definition with a depth of penetration
amply sufficient for all medical purposes, and, while giving a perfect
resolution of all known tests, including even those terrible puzzlers
Stcturoneis spicula * and Amphipleura pellucida , be capable of being
worked up by deep eye-pieces to 3500 diameters without detriment to
the definition.

In his correspondence he says : “ I hope to bring my new lenses
to such a point of perfection that they will not want any correction-
screw for different thicknesses of glass cover. I tried a power of
2000 diameters on very fine organic objects with covering glass of
•1- and -jL- of a millimeter, side by side, without being able to find any
difference in distinctness. I also tried Grammatophora subtilissima
with cover of ^ and without perceiving any difference.” ....
“ My old dry lenses show longitudinal dotted lines on Amphipleura
pellucida, and lateral of the same kind ; and in very bright light the
little corpusculi can be seen standing diagonally on the longitudinal
lines, being of a rectangular form,| as you will find them on P. balti-
cum and P. attenuatum. My new immersion lenses will resolve the
object with ease, even with direct light, as they will also show the
little corpusculi on the lines of Gram, subtilissima and S. gemma.”

. . . . “ It [the new pattern immersion lens] will, even with direct
light, resolve Frustulia Saxonica and the real Grammatophora sub-
tilissima, which has never been resolved by any instrument which I
compared with mine, neither English, German, nor French, all of
which I compared at various times. But my slide of Grammatophora
(in Canada balsam) was never resolved by any glass of the best
makers. You will also see the puncta of Amphipleura pellucida with
direct light.”

And in his recent catalogue, which appeared within the last three
weeks, this new species of lens is thus described : “ Objectives of
newest construction, on the immersion system, requiring no correc-
tion-adjustment for different thicknesses of glass, which, at a magni-
fication of 2000 diameters, and on covering glass from TJT to i of a

* A veteran microscopist of great skill as a manipulator, in his letter to me
dated Sept. 27, 1875, says: “ I have this morning succeeded in resolving Stciuroneis
spicula to my satisfaction. I have had a great deal of trouble with it. It is
undoubtedly the very hardest object I ever had to deal with, — Amph. pellucida not
excepted. I could, however, do nothing with St. spicula by lamplight. I soon
found morning was the only light that would enable me to deal with it; and I
have now seen it resolved, — I may say ‘brilliantly,’ — all over the lorica.” Com-
pare also Mr. Leifchild’s letter in the ‘ M. M. J.,’ vol. xiii. p. 174.

f Without professing to follow the learned Professor in his views of the mark-
ings of Amph. pellucida, I may mention that a notable microscopist of my acquaint-
ance sent him an especially difficult slide of that diatom, with a request that he
would resolve it, and received in a few days a pencil drawing of it, corresponding
in all its details with the above description. This drawing I have seen.

262

CORRESPONDENCE.

millimeter, exhibit equal distinctness, and hear a magnification of 3500
diameters with clearness and sharpness, and show the dots on Amphi-
pleura pellucida, Surirella gemma and Grammatophora subtilissima even
without oblique illumination, but with oblique light, with great pro-
minence, and the most delicate organic objects superbly.” So much
for the man’s own account of the matter. I may now state what I
have done with it myself. I tried it with respect to the several
points of screw-collar, resolution, penetration, depth of eye-piece, and
definition, with the following results :

(1) Screw-collar. — So far as I have been able to examine it on this
point, — and I tried it on covering glass ranging from • 003 to * 008, —
the maker is fully justified in his statement. I found no difference
whatever.

(2) Resolution. — It worked upwards, with comparative ease, through
S. gemma, P. macrum, Frustulia Scixonica, and Navicula crassinervis,
resolving them with great beauty and sharpness ; but at Staurmeis
spicula it stopped ; and no coaxing could draw it onwards. On this
occasion I used a C eye-piece with oblique light from an ordinary
concave mirror. Next night, having substituted a peculiar arrange-
ment of my Abraham’s prism, and again using the C eye-piece, the
resolution was absolutely perfect from end to end, and the object as
colourless as water. In both cases I used a Bockett lamp. Its reso-
lution, then, I must pronounce excellent.

(3) Penetration. — In this respect also it was perfectly satisfactory,
showing layer after layer of tissue to a good depth ; and I can only
conceive its failure where the operator cuts his sections too thick.

(4) Depth of Eye-piece. — In this trial I had at command B and O
eye-pieces by Baker, I) by Powell and Lealand, and E and F by Ross.
The third of these I was soon obliged to discard, as it gave much in-
ferior images to those presented by the E and F eve-pieces.

On P. angulatum , with E eye-piece, the resolution was only
moderately good, and there wras a certain amount of unmistakable
“ fuzziness,” which was not pleasant. On S. gemma with E and F
eye-pieces, the result was simply nil, though it had but a minute
before resolved this diatom beautifully with a C eye-piece.

In my own practice I should never think of using it with any
higher eye-piece than C. I also came to the conclusion that there was
ample room for improvement in our eye-pieces. It will be seen, then,
that I have come far short of doing with it all that the maker pro-
mised it should do. This the reader may, if he likes, attribute to
my want of manipulative skill. But there is something also in the
fact that this glass, — confessedly one of a novel and singular con-
struction,—had only been in my hands some thirty-six hours, — too
short a time to enable one to become acquainted with all its little
whims and peculiarities. For lenses too have their little whims as
well as human beings ; and these have to be studied, and humoured,
if one is to succeed in making a lens do its very best.

(5) Definition. — This I conceive to be the distinctive feature and
special excellence of Hasert’s new system. Indeed, I seem to myself

CORRESPONDENCE.

263

never to have known what the word definition really meant till I saw
this glass, so beautifully clear, sharp, and distinct were all the details.
I certainly never saw any objective that even approached it !

I may add that, throughout the whole trial it was matched with my
•jTth immersion, which is a glass of no mean capabilities.

On the other hand, this description of objective can never
seriously compete with English manufacture, and for the three
following reasons :

1. Its inordinately high price.

2. The strong prejudice in England against all objectives unpro-
vided with correction-arrangement.

3. Its comparatively weak magnification.

I ought to have mentioned that, though nominally a inch, it
is really only a T~- inch ; and that there is a great lack of neatness
and finish in the brasswork.

Yours faithfully,

W. J. Hickie.

Mr. Mayall’s Letter.

To the Editor of the 1 Monthly Microscopical Journal.'

London, October 11, 1875.

Sir, — Mr. Mayall appears to have been afflicted with the desire
that I should be wrong in the immersed angle of aperture question,
and now relieves his mind by attempting to revive the controversy.
In this I have said all that I consider necessary, or intend to say.

Mr. Mayall admits his inability to deal with the question, and
consequently submits it to “ one of the highest mathematical autho-
rities in England.” If the high mathematical authority, instead of
taking his information second-hand from Mr. Mayall’s version, had
looked directly at my writings on the subject, he would have found
at the root and foundation of it all, a paper dated more than twenty
years ago, in the £ Quarterly Journal of Microscopical Science,’ wherein
I pointed out that any angle in an object-glass must necessarily be
reduced by immersion in fluid or balsam, and showed how by means
of a special frontal adaptation full aperture on balsam objects could
be obtained. Therefore, however consoling to Mr. Mayall the opinion
of the high mathematical authority may be, his anonymous verdict
will not be considered important by others.

As Crito observed, Moller’s Probe-Platte used with the reflex illu-
minator has so little to do with the question, that a slip of plain glass
would answer the same purpose, supposing that there is anything
important in the experiment. The diatoms in Moller’s Probe-Platte
are mounted in balsam, and whether they adhere to the cover, or slide,
or float in the medium, practically there will be no difference ; and

264

PROCEEDINGS OF SOCIETIES.

when fluid is introduced between the lens and cover not a feature
in the principle of the reflex illuminator exists — all total reflexion
has gone, and I should expect light to pass into the object-glass, and
the field would no longer be a dark one.

Yours truly,

F. H. Wenham.

P.S. — Fix a very thick piece of plate glass on stage of microscope
with body set horizontally. The upper side of the plate is polished,
the under side fine ground. Focus the top surface with an immersion
■|th or ^th having the highest available aperture. Place a lamp at eye-
piece end, and a disk of light will appear on the under ground surface.
The diameter of this is the base of a cone, the apex of which is on the
upper surface, and the angle of the cone is the diminished aperture of
the object-glass — the angle that the extra immersion partisans will
have it is increased by a water connection between the front lens and
object surface. Therefore look sharply while an assistant introduces
the water intermedium. According to their notion the disk should
at once increase in diameter, but not the slightest change is visible ;
all that the water has done is to straighten the sharp bend of the rays
that before existed between the disunited surfaces. The angle in the
plate of glass remains just as before.

I need scarcely say that I am wearied with describing these simple
demonstrations. They are quite in vain, because the spirit of much
of the opposition has shown more of a desire to have the satisfaction
or credit of stating me to be wrong than to aid in establishing a
scientific truth.

PEOCEEDINGS OF SOCIETIES.

Eoyal Microscopical Society.

King’s College, October 6, 1875.

H. C. Sorby, Esq., F.E.S., President, in the chair.

The minutes of the preceding meeting were read and confirmed.

The subjoined list of donations to the Society was read, and the
thanks of the meeting were voted to the donors.

Mr. Slack drew attention to the turn-table which had been presented
to the Society by Mr. Cox, and which was placed upon the table for
the inspection of the Fellows. Also to a new form of microscope
which had been kindly sent by Messrs. Beck for exhibition ; it had a
strong and firm stand, and a set of powers up to a dry ^ inch, and
packed in a moderate-sized case which contained all that was really
necessary for a complete student’s course. Also to a new form of
pocket lens by Mr. Browning, and which seemed to be a great
improvement upon those generally in use ; it was an achromatic
triplet, with an unusually large, flat field, and very fine definition. He

PROCEEDINGS OF SOCIETIES.

265

also reminded the meeting that in April, 1874, Mr. Mclntire exhibited
a slide of the proboscis of a moth which had a perforating organ
appended to it, and which had been discovered amongst a collection of
insects said to have come from West Africa. In ‘ Comptes Rendus *
for last August a paper appeared on Lepidoptera with perforating
trunks, which were said to do much damage to oranges in tropical
countries. They belonged to the genus Ophideres of Australia. As
the paper was of considerable interest, he would send a translation of
it to the Journal. The credit of being the first European observer of
a moth with such a proboscis certainly belonged to Mr. Mclntire, and
it would be very interesting if entomologists in this country would
take the trouble to look through their specimens, and see if anything
similar could be found amongst British Noctuidte.

Mr. Mclntire, after looking at the drawing, believed it represented
precisely the same object as the one he had shown, except that the
drawing gave a view of both sides of the proboscis, whereas his
specimen only showed half.

The President hoped that the subject would not drop, and quite
agreed wit a Mr. Slack that English entomologists should take the
matter up.

The thanks of the meeting were voted to Mr. Slack for his com-
munication.

Mr. Beck said lie wished to present to the Society a specimen of
the blood of the Amphiuma, which was remarkable for the great size
of the blood-disks, being the largest known. The creature from which
it was obtained was about 18 inches long, of a dark colour, something
like an eel, with rudimentary legs. It was found in the Mississippi,
and in times of flood they came up the gutters, and were said to bite
and kill the negro children. There was, however, nothing in the
anatomy of the creature to confirm this idea, and he had heard from
naturalists that there was no foundation for the idea that these reptiles
were venomous. He received his specimen from a friend in New
Orleans. It seemed quite healthy on arrival here, and fed freely on
worms, &c. After a time he cut off the tip of its tail, and got a quan-
tity of blood from it, the same as mounted on the slide. After the
creature was killed it was injected ; and on dissection it was found to
contain a great quantity of eggs. Many of the vessels were found
to present interesting peculiarities, owing to the large size of the
blood-corpuscles which had to pass through them ; and he hoped at
some future time to be able to present to the Society some slides of
the ova, and also of the various organs.

The microscope which he had brought for exhibition was one
further step in the direction of carrying the microscope within the
reach of those whose means were limited. He had taken such points
of the cheap foreign microscopes which commended themselves ; he
had also taken the best points of English instruments. The rack-
and-pinion adjustment, though discarded by some foreign makers,
had been retained. The stage was made particularly thin ; and the
diaphragm had an extremely small hole in it, and this was of great
value in physiological study.

266

PROCEEDINGS OF SOCIETIES.

The thanks of the meeting were voted to Mr. Beck for his com-
munication.

A paper by Dr. G. W. Royston - Pigott, “ On the Identical
Characters of Chromatic and Spherical Aberration,” was read by the
Secretary.

The President thought that some of the statements in the paper
appeared to require a little limit ; for he imagined it would be quite
possible to produce a lens having the spherical aberration correct for
each ray, and yet still having a different focus for each ray.

Mr. Slack suggested that the paper obviously opened up a very
important question as to the finest possible point of correction for
lenses ; and this reminded him that Herr Hasert, of Eisenach, adver-
tised a new objective, which he said magnified 2000 or 3000 diameters,
required no corrections for covering glasses of different thicknesses,
and with which, it was stated, Amphipleura pellucida could be seen
“ without the use of oblique light.” Now if he had done this, he had
certainly done a most astounding thing ; but whether it was all true
or not, it showed the direction in which foreign makers were moving.

Mr. Beck said he had tried to understand Dr. Pigott ’s paper, but
could not do so at all ; perhaps when printed he might be able to
comprehend the meaning of it.

Dr. Lawson said he had received a letter from Mr. Hickie respect-
ing the objective referred to by Mr. Slack, to the effect that he had
examined it, and had found it produced very remarkable effects ; also
that it was perfectly true that it did not matter within certain limits
what covering glass was used with it.

Mr. Curties said that Mr. Hickie would be very happy to send this
lens to the Society for examination.

Dr. Pigott said he had not much to say in reply. The matter
seemed very simple. He had lately been studying Professor Litrow’s
remarks on the achromatism of lenses for telescopes, and he there
shows that he has calculated the marginal, central, violet, and red
rays, and carried them out to five places of decimals, and found that
they all came to the same point.

Dr. C. T. Hudson gave a highly interesting communication “ On
a New Species of Melicerta,” illustrating the subject by a large
number of very beautiful diagrams in coloured chalk, and by drawings
on the board.

The President felt sure that all would unite in passing a cordial
vote of thanks to Dr. Hudson for his very interesting paper, and he
could not himself refrain from complimenting him upon the very
great artistic taste displayed in the drawings exhibited in the room.
He had not studied that class of objects much, but felt there were
many persons in the room who would be glad to say something on the
subject.

Dr. Pigott said he should like to ask Dr. Hudson what power he
used in making these investigations ?

Dr. Hudson replied that he usually worked with a \ inch and a
B eye-piece, but he preferred A. When looking at the objects with
a ^ inch through the side of a trough, he often found that lie could

PROCEEDINGS OF SOCIETIES.

267

not reach them. He had seen it mentioned that by the introduction
of a ^-inch lens into the body of the microscope the focal length of
the objective was increased without detriment to the power or the
definition. He was glad to have the opportunity of asking Dr. Pigott
if it was possible to do this, as it would be a very great advantage to
him if he could.

Dr. Pigott said he had often got into similar difficulties himself,
particularly with the ^ inch ; but by using lenses in the body of the
tube he had obtained the advantage mentioned, and had saved the
covering glasses of many valuable slides. With regard to Dr. Hudson’s
question, he presumed that the power employed would be about
200 diameters with a C eye-piece. In that case, if he would take
another i-inch objective to pieces, and put the back lens of it between
the objective and the eye-piece, he would find that it would have the
effect which he desired to obtain.

Mr. Jas. Smith recommended the method of putting an object-glass
below the stage and then working through it with a 3 inch above
the stage in the ordinary manner. By this means a series of powers
varying from 2 to 150 diameters could be obtained with a considerable
leugth of focus, and with the advantage of the objects being seen erect.
With a ^ inch below and a 1 inch above a different range of powers
would be obtained ; they would in this way get not only a splendid
range of objectives and definition, but could use it very well in tanks
more than half an inch in depth.

Dr. Pigott said if good definition was desired, the lower the lens
was put down in the tube the better.

Mr. Beck would be sorry to pass away from the very beautiful
drawings before them to matters of detail without asking whether the
variations from Ehrenberg’s figure were more important than the fact
that the creature did not build up a tube ? Was not this tube building
one of the characteristics of Melicerta ? And if so, could they be
right in classing equally as Melicerta a creature which did not build
itself a tube ?

Dr. Hudson said there was in all cases a gelatinous sheath, with
foreign particles lying evenly or unevenly upon it.

Mr. Slack said it seemed to him that if the secreting organ
described by Dr. Hudson had a structure like that of the brick-making
organ, the creature might be put under the same genus as Melicerta
ringens ; but if it was not so, he thought this would be sufficient to
make quite a generic distinction. He had suspected the existence of
a Melicerta besides M. ringens. Ordinarily the pellets of M. ringens
were round in shape, but by pressure together became hexagonal ; but
he had once found a number of pellets which were quite conical in
form, and he thought that they must have been the work of another
species. The identification of rotifers was often rendered extremely
difficult by their peculiar behaviour. The Cephalosiphons sent by
him to Mr. Gosse some years ago, and figured in the ‘Intellectual
Observer,’ only partially expanded their disks, and looked like some
other species. Other specimens sent to an excellent naturalist pre-
sented only misleading appearances.

268

PROCEEDINGS OF SOCIETIES.

The thanks of the meeting were then voted to Dr. Hudson for his
paper.

The President announced that it was proposed to have another
Scientific Evening on Wednesday, the 24th of November, provided the
rooms could be obtained on that date for the purpose.* Due notice of
this or of any other arrangement would of course be given.

Donations to the Library, &c., from J une 2 to October 6 :

From

Nature. Weekly The Editor.

Atkemeum. Weekly Ditto.

Society of Arts Journal. Weekly Society.

Proceedings of the Bristol Naturalists’ Society, 1871-5 .. Ditto.

Journal of the Quekett Club. No. 29 Club.

Transactions of the Watford Natural History Society. No. 1 Society.

Smithsonian Report for 1873 Institution.

Transactions of the Woolhope Club for 1871-3 Club.

List of Elevations West of the Mississippi River. 3rd Edit.

Journal of the Linnean Society. No. 80 Society.

Bulletin de la Socie'te' de Botanique de France. Three parts Ditto.

The Harveian Oration for 1875. By Dr. W. Guy Author.

Popular Science Review Ditto.

Quarterly Journal of the Geological Society. No. 123 .. Society.

Report of the U. S. Geological Survey. Yol. VI. By

F. Y. Hayden U.S. Government.

A Report of the Hygiene of the United States Army, &c. U.S. Surgeon-General.

A Turn-table C. F. Cox, Esq.

Two Slides of Diatoms F. Kitton, Esq.

A Slide of Blood of Amphiuma means J. Beck, Esq.

J. Birdsall Jones, Esq., was elected a Fellow of the Society.

Walter W. Reeves,

Assist. -Secretary.

* Permission has since been given.

The Monthly Microscopical Journal, 'Dec? 1. 187 5

PI CXXffi

WWastt C°ltk.

THE

MONTHLY MICROSCOPICAL JOURNAL.

DECEMBER 1, 1875.

I. — On a New Method of Measuring the Position of the Bands
in Spectra. By H. C. Sorby, F.R.S., &c., Pres. B.M.S.

( Read before the Royal Microscopical Society, November 3, 1875.)

Plate CXXIII.

In various papers published during the lost few years I have
described a small piece of apparatus by means of which we can
obtain a spectrum with a number of dark bands that can be used
as a standard scale for measuring the position of those seen in any
spectra compared with it side by side. For ordinary purposes,
when very great accuracy is unnecessary, nothing could be more
convenient ; since the position of the bands can be read off at once.
The only serious objection is that it is difficult to accurately appre-
ciate the fractional parts of the intervals between the different
bands of the scale. Thus, for example, it may be difficult to say
whether the centre of a band were situated at of or 3f. When
there is any such difficulty I take the intermediate value, ; but
even with every care, and after having acquired all the skill that
comes from long practice, it may be looked upon as impossible to
measure the position of the centre of any absorption band to less
than one-eighth of the interval between the bands of the scale. In
many cases this is of very little importance, but when it is necessary
to measure the position with sufficient accuracy to enable us to
ascertain the true laws of the relative wave-lengths of a number of
bands, such a source of uncertainty is very objectionable, and it is
most desirable to adopt some method that may give the wave-
lengths true to a millionth of a millimeter.

For some years past I have been fully alive to the importance
of some plan which would enable us to obtain a spectrum in which
a well-marked band could be made to travel up and down, and ad-
justed exactly in the line of the centre of any hand in the spectrum
under investigation. There is no difficulty whatever in seeing
when one band is in exactly the same line as the other. It is a
totally different thing to estimate by the eye alone the exact value
of a fractional interval. This will be more easily understood by

VOL. xiv. u

270 Transactions of the Royal Microscopical Society.

referring to PI. CXXIII., Fig. 2. I have constantly had this question
before me, but for years felt that it was a thing more to be desired
than hoped for, and I had almost come to the conclusion that it
could not be accomplished, when all at once I hit upon a plan which
is even better than anything I could have wished for.

In studying the spectra due to different kinds of interference in
connection with the colour of feathers, insects, and minerals, I was
led to examine the spectrum of crystals of quartz cut so that the
light passes along the line of the principal axis. As is well known,
the light then experiences no double refraction, hut is circularly
polarized. When viewed in a polariscope, a slice of about one-
fourth of an inch in thickness gives fine colours, and when rotated
no change whatever results ; but if either the polarizer or analyzer
be rotated, the colours vary much and return to the same tint at
each half revolution. On studying the spectrum of this light, one
or more well-marked black bands will be seen, and on rotating the
polarizer or analyzer these move over the spectrum, and again
occupy the original positions on the completion of each half revolu-
tion of the polarizer or analyzer. The number of these bands in-
creases with the thickness of the plate of quartz, and their width
diminishes, so that by using a very thick piece they may be made
as numerous and narrow as may be desired. The question then is
to choose such a thickness as may not be practically inconvenient,
and yet give sufficiently numerous and well-defined black bands.
The thickness which I have adopted is 1 ^ inch. With this the
whole visible spectrum is divided into eight spaces by seven well-
defined bands, which in a prism spectrum are apparently at very
uniform intervals, as shown by I of PI. CXXIII., Fig. 2, but at a
much less wave-length interval at the blue end than at the red end,
as will be seen from the table given below.

In order to make use of these properties of quartz it is necessary
to have it mounted between two Nicol’s prisms, in the manner shown
by PI. CXXIII., Fig. 1. The upper can be rotated for accurate
adjustment, and the lower is permanently fixed in a mounting with
an ivory circle 2\ inches in diameter, each half of which is divided
into ten parts, and these again into five smaller divisions, so that
there is no difficulty in reading off to y^th of a half revolution.
After placing this circle at the zero point, the upper Nicol is rotated
so that the centre of the second dark band from the red end of the
spectrum exactly coincides with the sodium line, or with the solar
line D, as shown by I of PI. CXXIII., Fig. 2. All the other dark
bands are then of course in perfectly constant and definite positions,
depending on the action of quartz on light of various wave-length.
On rotating the ivory circle each band gradually passes from the
red end towards the blue, until when the circle comes to the next
zero point, commencing the next semicircle, the series of bands is

The Position of the Bands in Spectra. By II. C. Sorby. 271

exactly the same as at first. Supposing then that when the circle
is placed at zero an absorption hand seen in some spectrum were
situated between the bands 3 and 4 of the scale, as shown by II of
Fig. 2, by rotating the circle the baud 3 can he made to pass
upwards until its centre exactly corresponds with that of the hand
whose position is being measured, as shown by III, and if this
occurs when the point used for reading off is at ’54 of the circle,
we at once know that the true position is 3 '51. In a similar
manner the situation of bands in any other part of the spectrum,
can he referred to other bands of the scale.

If it were necessary only to compare one spectrum with another,
this alone would suffice ; bat, as I pointed out in a paper read before
this Society last Aporil, it is very desirable to express everything in
wave-lengths. In order to do this a table must he constructed,
giving them in millionths of a millimeter for each tenth of a
division between all the hands. For this purpose it is necessary to
employ a diffraction spectroscope and strong illumination. I first
made use of direct sunlight, hut the movement of the light was
found to be very inconvenient, and to cause some uncertainty in
the measurements. I therefore finally adopted the results obtained
by using a limelight, since it could be fixed in a proper position
and kept immovable during all the measurements. The angle of
the inclination ( 0 ) of the telescope hearing the eye-piece with cross
wires was read off to half-minutes of a degree in the case of all the
bands. If two measurements differed by more than I-', other observa-
tions were made, and the mean of all adopted. This was repeated for
each Toth division of the ivory circle of the apparatus, since other-
wise the irregular action of the quartz on light of different wave-
lengths would have given rise to serious errors. All the calculations
were based on the wave-length of the centre of the two principal
sodium lines (D), which, according to both Angstrom, Huggins,
Kirchhoff, and Thalen, is 589 • 2 millionths of a millimeter. The
diffraction grating used was a photograph, for which I am indebted
to the kindness of Lord Eayleigh, which by calculation must con-
tain 6003 lines in a French inch, and the distance between each
two lines must be ‘004509 millimeter. The wave-lengths were
calculated by means of the following equation :

X = '004509 sin. 0,

since I made use of the spectrum of the first order. On the whole,
I think the results may he looked upon as true to a millionth of a
millimeter.

Of course it must be borne in mind that these measurements
apply only to the quartz exactly H inch in thickness, cut and
mounted exactly in the proper direction.

u 2

272

Transactions of the Royal Microscopical Society.

Table of the Wave-lengths in Millionths of a Millimeter corresponding
to each -J^tii Division between the Various Bands, and of the Quantities
to be deducted for each intermediate xg^th of the Half Revolution.

Readings of
the Scale.

Wave-lengths
for each Tlsth.

Deduction for
each x5oth.

Readings of
the Scale.

Wave-lengths
for each y5th.

Deduction for
each j-^jth.

•7

687

•8

43

488

•3

•8

679

•9

4-4

485

•3

•9

670

•9

4-5

482

•3

10

661

•8

4-6

479

■3

11

653

*8

47

476

•3

1-2

645

•8

4-8

473

•3

1-3

637

*7

4-9

470

•2

1-4

630

•6

5-0

468

•4

1-5

624

*7

51

464

•3

1-6

617

•8

5-2

461

•2

1-7

609

■6

5-3

459

•3

1-8

603

•6

5-4

456

•3

1-9

597

•8

55

453

•2

2-0

589

•5

5-6

451

•2

2-1

584

•6

5-7

449

•2

2-2

578

•5

5-8

447

•2

2-3

573

•6

5-9

445

•2

2-4

567

•5

6-0

443

•2

2-5

562

•5

61

441

•3

2-6

557

•5

6-2

438

•3

2-7

552

•5

6-3

435

•3

2-8

547

•4

6-4

432

•2

2-9

543

•5

6-5

430

•1

3-0

538

•5

6-6

429

•1

31

533

•4

6-7

428

•3

3-2

529

•5

6-8

425

•2

3-3

524

•4

6-9

423

1

3-4

520

•3

7-0

422

•3

3-5

517

•4

7-1

419

•1

3-6

513

•5

7-2

418

•1

3-7

508

•3

7-3

417

■1

3-8

505

'3

7'4

416

•3

3-9

502

•4

7'5

413

1

4-0

498

•3

7-6

412

•2

41

495

•2

7-7

410

•2

4'2

493

•5

7-8

408

•1

The chief objections against this apparatus are, that it is some-
what difficult to obtain a suitable piece of quartz, and to cut it so
that the light may pass exactly in the line of the principal axis of
the crystal. Very often, though it may be perfectly clear and free
from visible flaws, it may contain imperfections in the form of
crystals arranged in a different optical position, easily seen with
polarized light. Then again, though a tolerably well-formed crystal
may be selected, much care is necessary to so cut and mount it that
the two parallel faces are exactly perpendicular to the principal
axis, along which there is no double refraction, but only true and
perfect circular polarization. However, with care this can be done,

The Position of the Bands in Spectra. By H. C. Sorby. 273

and the piece finished off true to less than T^oth of an inch.
When once made, the only material objection is that since the
quartz must be If inch thick and there must he Xi col’s prisms at
each end, the entire length becomes about 3 b inches. For this
reason it is the most convenient to place it in the position of the
condenser under the stage of the microscope, and to make use of it
with the binocular apparatus described in the paper alluded to
above, care being taken to reflect the light directly through the axis,
since otherwise there is a slight change in the position of the
hands. By arranging a movable plano-convex lens over the upper
Nicol’s prism, as shown by Fig. 1, the light may be made equally
bright in the two tubes of the microscope. The position of the
hands seen in the spectrum of any object placed before the small
reflecting prism can then be measured with great facility to some-
thing like the millionth of a millimeter, since with well-marked
bands consecutive measurements do not differ more than T{5th of
the half revolution of the circle, and when they do differ more the
mean of several observations may he taken.

As an example, I give the measurements in the case of the
hands seen in the spectra of oxidized haemoglobin and of the same
substance in which the oxygen is replaced by carbonic oxide.

Oxidized haemoglobin . .
Carbonic oxide haemoglobin

Measurements
by Scale.

Wave-lengths.

2-19

584 - 9 x -6 = 579

2-88

547 — 8 X -4 = 544

2-28

57S - 8 x -5 = 574

2-96

543 - 6 x -5 = 540

274

Transactions of the Royal Microscopical Society.

II. — Note on the Markings of Frustulia Saxonica.

By Assistant-Surgeon J. J. Woodward, U. S. Army.

{Read before the Royal Microscopical Society, November 3, 1875.)

Plates CXXIV. and CXXY.

On returning from my last summer’s vacation my attention was
directed a few days ago, for the first time, to a letter by Mr. W. J.
Hickie in the July number of the ‘ Monthly Microscopical Journal’
(p. 32), on the subject of the markings of Frustulia Saxonica,
which seems to call for some comments from me.

Mr. Hickie refers to a paragraph in the ‘ Monthly Micro-
scopical Journal’ (vol. ix., p. 86) headed “ Frustulia Saxonica as a
Definition Test,” which he, however, thinks may possibly misrepre-
sent my views, and remarks — “ What is there said is by no means
very clear ; but it certainly does make him assert one of two
things : either (1) that Frustulia Saxonica is a one-lined object
(i. e. has transverse, but no longitudinal lines) ; or (2) that,
though it undoubtedly has transverse, and may possibly have
longitudinal lines as well, no one as yet has succeeded in seeing
the latter, hut that those who fancied they saw them, as Dippel
and others, have been deceived by ‘ diffraction phenomena.’ ” I will
frankly say that the second of these views very fairly represents
my opinions on this subject, although it is not precisely what I
said.

The paragraph quoted by Mr. Hickie is abridged from a “ Note
on the Frustulia Saxonica as a Test of High-Power Definition,”
which I published in the ‘ Lens’ for October, 1872 (p. 233), and
of which I send herewith two copies, with the request that one of
them may be forwarded to Mr. Hickie. The original article was
illustrated by a Woodbury type plate, of which I have now no
spare copies ; I send, however, two silver prints (marked A) from
the negative used in its preparation. In this “ Note ” I quoted
Dippel’s description,* which attributes to Frustulia Saxonica both
longitudinal and transverse striae, and estimates the first at 18 to
20, the second at 34 to 35 in the one hundredth of a millimeter.
I stated that I myself found the transverse striae count 85 to 90 in
the one thousandth of an inch, which agrees substantially with
Dippel’s figures, but said, “ The longitudinal striae of Dippel, how-
ever, I must regard as diffraction phenomena,” and went on to
assert that as I observed them “they varied too much in their
distance apart, with varying obliquity of illumination, to bear any
other interpretation.” It will be observed that I did not, in my

* From ‘ Das Mikroskop und seine Anwendung.’ Erster Theil. Braunschweig,
1867, s. 132.

WWest&Co lith.

TheMontMyMicroscopical Journal. Deel.1875. PI. CXXIV

The markings onkrustuKa Saxomca

The MonthlyMicroseopicai J ournai .D ec .1 187 5 . PI . CXXY .

WAV s st & Co .lith. .

TTie markings bnFrastuliaS-axomca.

Markings of Frustulia Saxonica. By Dr. J. J. Woodward. 275

“ Note,” speak generally, as Mr. Hickie does, of what “ Dippel and
others ” fancied they saw, but specifically of the longitudinal striae
of Dippel. My reason for this limitation was, I confess, that I did
not at the time know that any authority but Dippel had described
longitudinal striae on this diatom. So far as Dippel was concerned,
I had not merely his description and his statement of the number
of lines he observed to the inch, but the excellent and truthful
woodcut in his book * on which to form an opinion. This wood-
cut, moreover, enabled me both then and now to know that the
specimens I studied belonged to the same species as that which
Dippel described.

In my “ Note,” then, I spoke only of the longitudinal striae
of Dippel, but now, in response to Mr. Hickie’s letter, I willingly
express my belief that the longitudinal lines which he describes are
of the same character. At the same time I shall be very glad if he
can convince me, by satisfactory evidence, that this belief is erro-
neous, for analogy inclines me towards the opinion that in both
Frustulia Saxonica and Amphipleura pellucida the striae are
really rows of beads, as is so easily to be seen in Navicula rhom-
boides, and that, consequently, we ought to be able to see longi-
tudinal striae when the illuminating pencil has the proper direction,
if only our glasses had the requisite defining power.

In favour of his opinion that he has actually seen these longi-
tudinal striae on Frustulia Saxonica, Mr. Hickie states, in the first
place, that Herr Seibert showed him in the summer of 1872 “a
couple of very beautiful photographs of that diatom, one of which
exhibited the transverse, and the other the longitudinal lines, with
far more clearness, sharpness, and distinctness than the printer will
be able to reproduce the words I have here written.” If I had
these photographs before me, they might, perhaps, though I confess
I do not expect it, show me that Herr Seibert has seen something
I have been unable to see, and I must therefore express the hope
that Mr. Hickie, in return for the package of photographs I send
him herewith, will take the trouble to obtain copies of them for me
to study. I hope also that he will obtain copies of them for the
Royal Microscopical Society, to compare with those I send. In the
absence of Herr Seibert’s photographs, however, I would remark,
that spurious lines, due to diffraction and interference, can be photo-
graphed quite as readily as real lines, from which they can only be
distinguished by observing precautions which Mr. Hickie’s letter
does not show to have been considered either by himself or any of
the distinguished gentlemen to whom he tells us he exhibited the
longitudinal striae in question.

Mr. Hickie tells us further, that “In Rhomboides also the
transverse lines are much closer than the longitudinal, whereas in
* Op. cit., fig. 103.

276 Transactions of the Royal Microscopical Society.

Frustulia Saxonica it is just the reverse.” This statement directly
contradicts the description of Dipped, whose measurements, quoted
above, make the longitudinal lines nearly twice as coarse as the
transverse instead of finer, and it might at first be thought that the
two gentlemen were describing different things, but, in point of
fact, as I stated in my “Note,” these spurious longitudinal lines
vary greatly “in their distances apart with varying obliquity of
illumination,” and also, I may now add, with varying positions
of the fine adjustment, so that I have had no difficulty in photo-
graphing them, as seen on the same frustule, and with the same
objective and distance, both finer than the transverse ones as
described by Mr. Hickie, and coarser than the transverse ones
as described by Dippel, and in both cases they appeared to me, as
Mr. Hickie says they did to him, “ as plainly and visibly as any of
us are ever likely to see our own faces in our looking-glasses.”
The distinctness with which these lines can be seen has nothing to
do with the question of their objective reality, for diffraction pheno-
mena are often quite as distinctly visible as the optical images of
actual objects.

The question of the real nature of these longitudinal lines
appears to me to be one of considerable interest, because it brings
up the matter of recognizing lines due to diffraction and inter-
ference, when observed in the field of the microscope, and because
these phenomena have been a fruitful source of error in the inter-
pretation of microscopic images. I have therefore thought it worth
while to prepare a series of photographs of Frustulia Saxonica for
the purpose of illustrating my meaning.

The first of these photographs (marked B) represents a frustule
of Frustulia Saxonica adjusted to show the transverse striae. This
frustule measured of an inch in length, with eighty-six striae
to the xoVo au inch. The negative is magnified 1830 diameters
very nearly, and to this of course the paper print closely approxi-
mates.*

The second photograph (marked C) represents the same frustule
with its left end raised so as to bring it obliquely to the light. In
its lower half, besides the transverse lines, a series of longitudinal
fines can be seen, which give rise in places to a distinct appearance
of dots at their intersections with the transverse striae. The nature
of these fines will be best understood after a study of the third and
fourth photographs.

In the third photograph (marked D) the same frustule is shown
with its left-hand angle still more elevated. The transverse striae
have disappeared; but in the left-hand half of the frustule we have a
beautiful series of longitudinal fines which very closely resemble

* Silver prints after mounting are usually a trifle larger than thc_ negatives
from which they are printed.

Markings of Frustulia Saxonica. By Dr. J. J. Woodward. '217

those shown in Dippel’s woodcut above referred to. Such longi-
tudinal lines as these, I suppose, Mr. Hickie himself has observed and
recognized as spurious, for he says in his letter — “ I had also no
difficulty in bringing into view those wide-spaced, spurious lines
alluded to by Dr. Woodward.”

Let us observe the character of these lines. They run parallel
to the midrib, handsomely following its sweeping curves, and it
will be seen that they become progressively closer and closer
together from the midrib towards the margin of the frustule. It
will also be seen that they do not terminate at the edges of the
frustule, but sweep off into the open space outside, where they
form a series of rhombic figures by crossing a fresh series of diffrac-
tion lines conditioned by the margin of the frustule, as the former
series was by the midrib. These characters would be sufficient to
show these lines to be spurious, but if, now, the fine adjustment be
toyed with, or the illumination changed, or both, they pass, by the
most insensible transitions, into new combinations, one of which is
shown in the next photograph. I would also call the attention of
those who examine this photograph to three shadows on the left of
the lower part of the frustule, which are cast by three out-of-focus
fragments of dirt adhering to the under surface of the glass cover
of the preparation. Each of these shadows is surrounded by a
series of lines due to diffraction and interference. The lower two
sets of these lines especially very closely resemble the longitudinal
lines on the frustule in number, distance apart, distinctness, and
general character.

In the fourth photograph (marked E) the same frustule is
shown standing vertically with the light coming from the right
side of the picture. On both sides of the frustule, but especially
on the right side — the left being in shadow — there are a series of
fine longitudinal lines, which I suppose to be similar to those Mr.
Hickie has described. They are rather closer together than the
transverse striae (counting eleven, on the negative, in the space
occupied on the negative of the photograph marked B, by ten of the
transverse striae), and their distance apart is more equable than is
the case with the longitudinal lines in the last photograph. Still,
if the paper print be examined with a hand-lens, I think it will be
plainly seen, as can readily be measured on the negative, that the
lines become progressively closer towards the margin, those nearest
the midrib being farthest apart. It will also be seen, on both sides
of the frustule, and especially at its upper end, that these longi-
tudinal lines are not limited to the surface of the frustule, but pass
off into space outside, where they cross a fresh series of beautiful
diffraction lines conditioned by the margin of the frustule. I would
particularly invite attention to this last series of lines, especially as
seen towards the top of the right-hand margin of the frustule. The

278 Transactions of the Royal Microscopical Society.

fine longitudinal lines shown on the frustule in this photograph,
then, like the coarse ones shown in the last, have all the characters
of diffraction fringes ; hut if any doubt remains, it is only necessary
to toy with the fine adjustment, when the number of the lines and
their distance apart will be found to vary continually, while in the
case of the transverse striae, or of any other real lines, the number
remains constant as long as they can be seen at all.

Besides the principal frustule shown in these pictures, part of
another frustule is shown in each, which affords still further illustra-
tions of the longitudinal lines in question. I may add that, although
I endeavoured to take the four pictures witli the same power,
trifling differences exist due to the necessary variations in the focal
adjustment.

As a still further illustration of the spurious longitudinal lines
of this diatom, I add a print (marked F) of a negative magnified
1600 diameters, made November 10, 1872, by Tolles’s immersion
xVth, in which the central frustule shows the transverse striae,
while portions of two others exhibit longitudinal lines, similar, as
I must suppose, to those Mr. Hickie sees. I would call attention
on this print, and, indeed, on the two others (marked A and B)
which show the transverse striae, to a curious series of diffraction
lines just outside of the margin of the frustule, which appear to he
conditioned by the transverse striae themselves. These spurious
lines are at exactly the same distance apart as the transverse striae,
hut form a sharp angle with them.

I send copies of all these photographs for Mr. Hickie, and also
a set for the Royal Microscopical Society. If the longitudinal lines
which Mr. Hickie sees are, as I suppose, similar to those which I
have photographed, these pictures will enable those who examine
them to decide whether his interpretation or mine is correct. If he
thinks he sees something of a different nature, I shall he happy to
consider the evidence on that head when he presents it.

These photographs will, moreover, enable those interested in
the subject to decide another question raised by Mr. Hickie in his
letter, viz. whether what I have photographed and described is
really Frustulia Saxonica, and also, whether I have, as he suggests,
“ merely been wasting” my “time on a bad slide.” It is quite true
that I have been using M oiler’s slides; it is also quite true that,
like Moller, I suppose Frustulia Saxonica to be identical with
Favicula crassinervis. I do not pretend to any special personal
knowledge of the proper classification of the diatoms, and derive
my opinion entirely from my friend Professor Hamilton L. Smith,
of Hobart College, Geneva, New York, who I suppose to be more
thoroughly acquainted with the subject of the Diatomaceae than
anyone on this side of the Atlantic, and who wrote me, January 9,
1872 : “ Navicula crassinervis has long been recoguized as =

Markings of Frustulia Saxonica. By Dr. J. J. Woodward. 279

Frustulia Saxonica.” Mr. Hickie asserts that there is a difference,
but does not make clear in what the difference consists. I should
be happy to learn further from him on this head, if he has any-
thing to teach. If, on examining my photographs, he thinks they
represent something different from his slides of Frustulia Saxonica ,
I should he glad to receive one of these from him to study. I have
the less hesitation in asking this favour, as he tells us his collection
of these slides is a very extensive one.

I conclude these remarks with the hope that Mr. Hickie will
find them as courteous as I acknowledge his own to be.

List of Photographic Prints accompanying Dr. Woodward's “ Note on the Markings of
Frustulia Saxonica.”

A. — Print from the negative used to illustrate Dr. Woodward's paper in the

‘Lens,’ X 1750 diam.

B. — Frustule photographed for the present paper to show the transverse striae,

X 1830 diameters.

C. — Same frustule, same power, showing both transverse and longitudinal lines.

D. — Same frustule, same power, showing the longitudinal lines of Dippel.

E. — Same frustule, same power, showing longitudinal lines similar to those

described by Mr. Hickie.

F. — Print from a negative made in 1872, showing the transverse striae on one

frustule, and longitudinal lines on parts of others.

EXPLANATION OF PLATES CXXIV. AND CXXV.

These Plates contain figures the same size as those in the several admirable
photographs which Dr. Woodward transmitted to us. The various figures are
given in the same order — A, B, C, &c. — as those above. Whereas, however, in
the photographs more than one diatom is occasionally introduced, in the Plate
but a single frustule is represented.

[The following remarks are contained in the ‘ Lens,’ October,
1872.]

Note on the Frustulia Saxonica as a Test of High-Power
Definition.

The genus Frustulia (Agardh) includes several species of diatoms
which possess bacillar or navicular frustules, “ immersed in an
amorphous gelatinous substance.” * The species are divided by
Pritchard into two groups, the first with “ evident strife,” while
in the second the striae are “ wanting or very indistinct.” In the
second group Pritchard places the species Saxonica (Eabenhorst), so
called from having first been noticed in Saxony, where it “ forms
dirty, olive-brown, tremulous jelly-like masses in little cavities of
damp rocks.” The c Micrographic Dictionary ’ (second edition)

* ‘A History of Infusoria.’ By Andrew Pritchard. 4th edit., London, 1861,
p. 924.

280 Transactions of the Royal Microscopical Society.

gives a brief description of this species, but does not mention the
striae.

The first description of the striae with which I am acquainted
was given by Professor Reinicke,* who saw fine transverse lines,
but found no objective capable of bringing them out clearly enough
to count them. (He used immersion objectives of Hartnack.)

The markings on the Frustulia Saxonica are described and
figured by Dippel, f whose description is as follows : “ The Frus-
tulia Saxonica possesses longitudinal and transverse striae, of
which the first are tolerably far apart (from eighteen to twenty to
the hundredth of a millimeter), the latter, on the contrary, some-
what closer than those of Grammatophora subtilissima (from
thirty-four to thirty-five to the hundredth of a millimeter). Both
systems of striae are very pale ( schivach gezeiclinet ), so they cer-
tainly require an excellent objective for their resolution. Never-
theless, with oblique light, and on bright days, they can be seen
with objectives of the highest power almost as well as those of the
Grammatopkora, if the object is only properly prepared, the valves
separated ( gespalten ), and mounted dry. In balsam, on the other
hand, the transverse striae are very difficult to see : nevertheless, I
have recognized them, even in this case, with the System No. 10 of
Hartnack.”

During the summer of 1871, a slide of Frustulia Saxonica,
mounted dry, was presented to the Museum by Dr. J. J. Higgins,
of New York, and subsequently two other slides, also dry, were
obtained from J. D. Moller, of Wedel, Holstein. I found no diffi-
culty, on these slides, in seeing and counting the transverse striae,
both with monochromatic sunlight and with the light of a small
coal-oil lamp. The longitudinal striae of Dippel, however, I must
regard as diffraction phenomena, similar in character to the longi-
tudinal lines which some have described in the central portion of
Grammatophora frustules ; they varied too much in their distance
apart, with varying obliquity of illumination, to bear any other
interpretation. The transverse striae, on the other hand, I found
very definite in character. I counted on different frustules from
eighty-five to ninety to the thousandth of an inch, which agrees
substantially with the results of Dippel, whose figures correspond
to from eighty-six to eighty-nine to the thousandth of an inch.
The frustules themselves varied in length from ’0018 to '0029
inch.

I subsequently removed the cover of one of the dry slides
obtained from Moller with the diatoms adherent to it, and

* See a review of his “ Beitr'age zur neuern Mikroscopie,” in the ‘ Quarterly
Journal of Microscopical Science,’ vol. ii., new series, 1862, p. 292.

f ‘Das Mikroskop und seine Anweudung.’ Erster Theil. Braunschweig,
1867, p. 132.

Markings of Frustulia Saxoniea. By Dr. J. J. Woodtvard. 281

mounted the specimen in Canada balsam. The striae were then
paler than before, but I cannot say that 1 found them more
difficult to resolve. Both in balsam and dry I could get resolu-
tion by the Tolles’s immersion itli belonging to the Museum, and
that by lamplight as well as by monochromatic sunlight. With
immersion objectives of higher powers the lines were still more
distinctly separated, and I obtained the finest results with the
immersion front of the xVth of Powell and Lealand, and with
the new immersion ^th recently made for the Museum by
Mr. Tolies.

On the whole, the Frustulia Saxoniea is an easier test than
the Amphipleura pellucida, as may be inferred from the above
measurement of its striae, and the difference is especially marked by
lamplight. Those therefore who work by lamplight only will find
this test more extensively useful than the Amphipleura.

The Woodbury print [see Plate CXXIY., Fig. A] illustrating
this article is copied from a negative made by the immersion front
of the Powell and Lealand -lYth belonging to the Museum. The
power used was 1750 diameters. It displays the transverse striae
as seen when the utmost pains are taken to avoid the longitudinal
diffraction lines.

282 Transactions of the Royal Microscopical Society.

III. — Appendix to the Paper on the Identical Characters of
Spherical and Chromatic Aberration.

By Dr. Royston-Pigott, F.R.S., &c.

( Taken as read before the Royal Microscopical Society, Nov. 3, 1875.)

The actual calculation of the difference between the spherical
aberrations of the extreme red and violet rays may easily be
obtained as follows, for an equi-convex lens.

For the spherical aberration of any ray whose refractive index
is jx is

— " — 7 • - 4 0* - 1) + (3m + 2) Gu - l) . «* + -£-}

fi . fi — 1 K/i — 1 fj. — 1) 8 J3

In the case of an equi-convex lens, a = 0 and x = 0 in this
expression and the spherical aberration becomes

1 fj.3 y 2 /x2 y1

M 0-1) * ‘ 8? = (M-l)2 ‘ 8/3’

y being the semi-aperture and / the focal length of the equi-convex
lens. In order therefore to get the spherical aberration for coloured
rays, the refractive index of the particular ray is substituted for fx
in this expression, viz.

m2

(m - 1)2 '

Now take the rays B and H in the solar spectrum representing
the extreme red and violet rays from Fraunhofer’s celebrated table
of refractive indices for crown and flint glass :

Kind of Glass.

Red Ray B.

Violet Ray H.

Crown glass, No. 9
Flint glass, No. 13

/x = 1-52583
/x = 1-62775

1-54657 = /x
1-67106 = /x

Hence the spherical aberration of the red ray for the crown is

y 3

proportionate to the coefficient of ~ , viz.

yfi ( 1 - 52583)2 2-328157

80- l)2 8C0-52583)2 2-211976

or red aberration in crown .. .. = 1-05252

so violet „ „ ....=!" 00082

Difference in aberration

•05170

Spherical it* Chromatic Aberration. By Dr. Royston-Pigott. 283

Also the spherical aberration for flint for red ray is proportionate
to

_ (1-62775)2 _ 6-723.i0

SO-1)2 S (0‘62775)2 8

or red aberration in flint .. .. = 0-840450

violet „ ,, = 0-775124

Difference = 0-065326

If these results be put in plain language, the spherical aber-
rations of the red and violet rays in crown glass No. 9 are as

105 to 100;

and in the flint glass as

84 to 77, nearly.

Entirely calculated, be it remarked, from the spherical aberra-
tion of the extreme red and violet rays in the two cases, which
thus show the proportions of the chromatic spherical aberration.

Moreover, the focal lengths of the same equi-convex lens, if of
crown, are

For the red and violet rays as

190 to 183,

and for the flint as

159 to 149, very nearly.

VOL. XIV.

X

( 284 )

IV. — The Slit as an Aid in Measuring Angular Aperture.

By Professor K. Keith.

It has recently been proposed to use a very narrow slit, on the
stage of the microscope, to prevent the supposed effect of stray
light in measuring the aperture of objectives.

This device could hardly mislead anyone who keeps in mind
the nature of spherical aberration. Most observers with the micro-
scope, however, give but little attention to the abstract principles of
the instrument, and therefore a graphic representation of the effect
of aberration will probably be of interest.

I present two figures, which correctly show the direction of the
light in the two cases specified : all the angles being calculated and
measured.

The objective is adjusted in both cases so as to be free from
aberration when the under surface of the glass cover is in focus, and
the upper surface touches the objective. The lines marked 40°,
38°, &c., represent the direction of the rays of light, the figures in-
dicating the angles that they make with the axis, and a h represents
the face of the objective.

Pm. l.

In the first figure, with the glass cover interposed, rays from
a small luminous object near the eye end of the tube, will all be
collected into a very small image at the point g. In this case there
is no aberration, and no stray light, and any of the devices for mea-

Measuring Angular Aperture. By Professor B. Keith. 285

suring agb, which is the balsam aperture, can he easily applied. If
the shutter be now placed on the under surface of the glass cover,
it is evident that, whether it be closed up more or less, it cannot
affect in any way the measurement of agb, because every point in
the image at g is the apex of a cone with a b for the diameter of
its base.

Fio. 2.

In the second figure, the glass cover is removed, and the effect
of aberration becomes strikingly apparent. The rays now, instead
of all crossing at g, aberr all the way from F to C, and for every
point along that distance the objective has a different aperture.
The point at which the light is maximum does not coincide with
the point at which the aperture is maximum. The shutter can now
be placed so as to reduce the aperture, hut can nowhere be placed
so as to take it all in, except almost in contact with the objective
and opened nearly as wide as its diameter.

It thus appears that, if the objective is corrected for aberration,
the shutter placed in the plane of its focus has no effect whatever.
And if the objective is not corrected, the shutter can only shut out
light too much affected by aberration to pass through the slit, which
is the very light of most importance, and that upon which the max-
imum aperture depends.

The extreme air angle (in this case 170°) is very properly given
by the makers as indicating the extreme capacity of the objective.
It is the only easily measured quantity that will answer the purpose.

x 2

286 Measuring Angular Aperture. By Professor B. Keith.

It is further plain from the figure that if light about 1° outside of
40° could pass through ab the maximum air angle would he
180°.

Objectives are constructed allowing light making an angle of
several degrees outside of 41° to pass through the front, if water or
balsam is interposed between the objective and the cover. It is
evident that for such objectives something more than a maximum
air angle of 180° is required to indicate their extreme aperture.
To simply state the maximum air angle at 180° does not do them
justice because the balsam angle corresponding to that air angle is
only 82°, and the objectives alluded to have a balsam angle of 100°
and upwards.

Alexandria, Virginia.

( 287 )

NEW BOOKS, WITH SHORT NOTICES.

Practical Hints on the Selection and TJse of the Microscope. Intended
for beginners. By John Pliin, New York, U.S.A. The Industrial
Publication Company, 1875. — The author of this little book, Mr. Phin,
states that he has endeavoured to put together some remarks that may
be useful solely for the beginner. He does not ambition anything
higher than this, and we must certainly admire his modesty. We have
gone carefully through the work, and we are glad to be able to say that
in all respects it is a book which may be read by the junior student with
pleasure and advantage. Almost the only fault we have to find with it
is its very imperfect illustration. Indeed we might almost say its
entire absence of illustration, for the few cuts widely scattered through
its pages are out of all proportion to the wants of the reader. This is
a serious disadvantage, and we trust it will be avoided in the next
edition which this little book is sure to pass through. We must take
exception to some of the author’s observations on lenses. In the first
place, it is exceedingly objectionable to divide all objectives into
English and French varieties. His principle of classification is too
old and exceptional. However, we quite agree with him in his remarks
on the subject of naming lenses. The English mode is unquestionably
the best, and the system of Hartnack and other foreign makers, of
numbering them 1, 2, 3, and so forth, is most inconvenient, and
the more so inasmuch as all Continental makers differ more or less
from each other in numbering the object-glasses. The division he
should have adopted is that of immersion and dry objectives. We
must likewise call his attention to the observations on immersion
lenses, which contain several misstatements in regard to their optical
qualities. We observe also that some of our more recent and withal
popular additions to microscopic apparatus are omitted. But on the
whole we must give Mr. Phin very high praise for his excellent
addition to our rudimentary works on the subject of the microscope.

Outlines of Practical Histology. Being Notes of the Histological
Section of the Class of Practical Physiology held in the University of
Edinburgh. By W. Rutherford, M.D., F.R.S.E., Professor of Physiology
in the University of Edinburgh. London: Churchill, 1875. — While
we are very glad to have such a book as the present one, and while it
will save those of us who have classes an immense deal of trouble, still
we cannot but utter our dissatisfaction with the general character of the
volume, and we hope to see it altered if it should go through another
edition. In the first place we must say that the author has been
careful to admit every subject which the ordinary medical student —
for it is for the medical student alone — requires. He gives him ample
advice as to what animal is to be killed for the tissue to be obtained
from ; then he tells him what he is to mount it in, and how he is to
look at it. But then, unfortunately, he has given no illustrations
whatever of the tissues — a circumstance that we consider extremely
unwise. Then, again, he has used Hartnack’s glasses alone, and the

288

PROGRESS OF MICROSCOPICAL SCIENCE.

student is only informed whether it is No. 7 or No. 3 objective he
is to use. This might have done very well for Dr. Rutherford’s
own class alone, hut as not a few teachers prefer to employ the objec-
tives of Ross, or Powell and Lealand, or Smith and Beck, as being
better than Hartnack’s, there is an omission which we fear will tell
against the volume. Then, again, why does the author, in referring to
the three unquestionably best makers in this country, omit Messrs.
Smith and Beck? We may say, too, that his mode of teaching the
student the estimation of the magnifying power he is employing is
clumsy in the extreme. On this point he would have done well to
have consulted Beale’s excellent volume. We observe that some very
valuable advice is given on the subject of epithelium, which shows
that the writer is thoroughly practical : it is in reference to the
question of killing the animal, which must not be done with chloro-
form. One passage on p. 23 is not quite clear, in which the author,
who has all along been speaking of Hartnack’s object-glasses, says
that a tissue is “ most evident with a -^th lens.” What does it
mean ? And again, what is the use of describing for the junior student
what he admits can only be seen with a power of 1000 diameters ?
and even then his description is not quite clear as to direction of striae
in muscle, we mean, of course, clear to the young beginner. Further,
Beale’s glycerine and Prussian blue is referred to on p. 27, without
any reference to where the description of its contents is to be found,
though afterwards an account of it is given on p. 66. The best chapter
in the volume is that in which the author’s microtome is described
and figured. In this he very fully explains his very useful instru-
ment, which works so well that we quite agree with Dr. Rutherford in
the opinion that the alterations proposed by others have been “ but
the reverse of improvements.” In the author’s observations on cements
we think he has spoken wisely and well, and we think his last obser-
vations to the student most valuable advice. We like the plan he has
adopted of interleaving the book with pages of plain paper, on which
the reader can write any remarks he may have to make. On the
whole then, with these few disparaging sentences we have already
written, we think the book is a valuable addition to our literature,
which we trust to see much improved after the next edition has gone
to press.

PROGRESS OF MICROSCOPICAL SCIENCE.

Microscopic Work of the ‘ Challenger .’ * — Professor Huxley writes
as follows to ‘ Nature ’ (August 19), enclosing a letter from Professor
Wyville Thomson : — The following extracts from a letter dated Yeddo,
June 9, 1875, addressed to me by Professor Wyville Thomson, will, I
think, interest the readers of ‘ Nature ’ :

“ In a note lately published in the ‘ Proceedings of the Royal

* This note lias been ‘‘ crushed out ” of several successive numbers of the
‘ M. M. J.’

PROGRESS OF MICROSCOPICAL SCIENCE.

289

Society ’ on the nature of our soundings in the Southern Sea, I stated
that up to that time we had never seen any trace of the pseudopodia of
Globigerina. I have now to tell a different tale, for we have seen
them very many times, and their condition and the entire appearance
and behaviour of the sarcode are, in a high degree, characteristic and
peculiar. When the living Globigerina is examined under very
favourable circumstances, that is to say, when it can at once be trans-
ferred from the tow-net and placed under a tolerably high power in
fresh, still sea-water, the sarcodic contents of the chambers may be
seen to exude gradually through the pores of the shell and spread out
until they form a gelatinous fringe or border round the shell, filling
up the spaces among the roots of the spines, and rising up a little
way along their length. This external coating of sarcode is rendered
very visible by the oil-globules, which are oval and of considerable
size, and filled with intensely coloured secondary globules ; they are
drawn along by the sarcode, and may be observed, with a little care,
following its spreading or contracting movements. At the same time,
an infinitely delicate sheath of sarcode containing minute transparent
granules, but no oil-globules, rises on each of the spines to its ex-
tremity, and may be seen creeping up one side and down the other of
the spine, with the peculiar flowing movement with which we are so
familiar in the pseudopodia of Gromia and of the Radiolarians. If
the cell in which the Globigerina is floating receive a sudden shock,
or if a drop of some irritating liquid be added to the water, the whole
mass of protoplasm retreats into the shell with great rapidity, drawing
the oil-globules along with it, and the outline of the surface of the
shell and of the hair-like spines is left as sharp as before the exodus of
the sarcode. We are getting sketches carefully prepared of the details
of this process, and either Mr. Murray or I will shortly describe it more

in full Our soundings in the Atlantic certainly gave us the

impression that the silicious bodies, including the spicules of Sponges,
the spicules and tests of Radiolarians, and the pustules of Diatoms
which occur in apjireciable proportions in Globigerina ooze, diminish
in number, and that the more delicate of them disappear, in the transi-
tion from the calcareous ooze to the ‘ red clay ’ ; and it is only by this
light of later observations that we are now aware that this is by no
means necessarily the case. On March 23, 1875, in the Pacific, in
lat. 11° 24' N., long. 143° 16' E., between the Carolines and the
Ladrones, we sounded in 4574 fathoms. The bottom was what might
naturally have been marked on the chart ‘ red clay ’ ; it was a tine
deposit, reddish brown in colour, and it contained scarcely a trace of
lime. It was different, however, from the ordinary ‘ red clay,’ — more
gritty — and the lower part of the contents of the sounding tube
seemed to have been compacted into a somewhat coherent cake, as if
already a stage towards hardening into stone. When placed under
the microscope, it was found to contain so large a proportion of the
tests of Radiolarians, that Murray proposes for it the name ‘ Radio-
larian ooze.’ This observation led to the reconsideration of the
deposits from the deepest soundings, and Murray thinks that he has
every reason to believe (and in this I entirely agree with him) that,

290 PROGRESS or MICROSCOPICAL SCIENCE.

shortly after the ‘ red clay ’ has assumed its most characteristic form,
bv the removal of the calcareous matter of the shells of the Forami-
nifera, at a depth of say 3000 fathoms, the deposit begins gradually to
alter again by the increasing proportion of the tests of Radiolarians,
until, at such extreme depths as that of the sounding of the 23rd of
March, it has once more assumed the character of au almost purely
organic formation, the shells of which it is mainly composed being
however in this case silicious, while in the former they were cal-
careous. The ‘ Radiolarian ooze,’ although consisting chiefly of the
tests of Eadiolarians, contains, even in its present condition, a very
considerable proportion of red clay. I believe that the explanation of
this change, which was suggested by Murray, and was indeed almost
a necessary sequence to his investigations, is the true one. We have
every reason to believe, from a series of observations, as yet very
incomplete, which have been made with the tow-net at different depths,
that Radiolarians exist at all depths in the water of the ocean, while
Foraminifera are confined to a comparatively superficial belt. At
the surface and a little below it the tow-net yields certain species ;
when sunk to greater depths, additional species are constantly found,
and in the deposits at the bottom new forms occur, which are met
with neither at the surface nor at intermediate depths. It would
seem also that the species increase iu number, and that the individuals
are of larger size as the depth becomes greater; but many more
observations are required before this can be stated with certainty.
Now, if the belt of Foraminifera which, by their decomposition,
according to our view, yield the ‘ red clay,’ be restricted and constant
in thickness, and if the Radiolaria live from the surface to the bottom,
it is clear that, if the depth be enormously increased, the accumulation
of the Radiolarian tests must gain upon that of the ‘ red clay,’ and
finally swamp and mask it.” Professor Wyville Thomson further
informs me that the best efforts of the £ Challenger’s ’ staff have failed
to discover Batliybius in a fresh state, and that it is seriously sus-
pected that the thing to which I gave that name is little more than
sulphate of lime, precipitated in a flocculent state from the sea water
by the strong alcohol in which the specimens of the deep-sea sound-
ings which I examined were preserved. “ The strange thing is, that
this inorganic precipitated is scarcely to be distinguished from pre-
cipitated albumen, and it resembles, perhaps even more closely, the
proligerous pellicle on the surface of a putrescent infusion (except in
the absence of all moving particles), colouring irregularly but very
fully with carmine, running into patches with defined edges, and in
every way comporting itself like an organic thing.” Professor
Thomson speaks very guardedly, and does not consider the fate of
Bathybius to be as yet absolutely decided. But since I am mainly
responsible for the mistake, if it be one, of introducing this singular
substance into the list of living things, I think I shall err on the right
side in attaching even greater weight than he does to the view which
he suggests.

( 291 )

NOTES AND MEMORANDA.

The Spinal Chord seen with the Polariscope. — In a recent
number of the ‘ New York Medical Journal ’ is a report of one of this
year’s meetings of the Boston Society of Medical Science, in which it
is stated that Dr. Webber had accidentally found, in using the polarizer
with the microscope, that granular corpuscles from preparations of the
spinal chord, hardened in chromic acid or bichromate of potassium
and preserved in glycerine, react peculiarly to polarized light, taking
on a crystalline appearance. Neither cholesterine nor any other
tissues or substances to be found in a number of sections of the brain
and chord affected the light in a similar way. and Dr. Webber thought
that this characteristic might serve to distinguish the granular cor-
puscles in doubtful cases. Dr. Webber agreed with the suggestion of
Dr. White that this behaviour of the granular bodies did not, neces-
sarily, imjfly any physical change in them, since the preparations
examined had been passed through one or more solutions of crystal-
line substances. Dr. Webber had also found, on examining sections
of brain-substance, that the nerve-fibres affected the light differently,
according to their direction.

Examination of Coal for Diatoms. — It will be remembered that
some time ago we announced the discovery of these forms in coal by
Count Castracane. As some of our readers may wish to follow up the
subject, we give the following method, which is described by Count
Castracane himself: — The course to pursue is decided by the flinty
nature of the diatom valves, and in order to separate them from the
mixture of calcareous or organic matter with which they are found
united, it is usual to put the whole into a glass test-tube with hydro-
chloric acid, adding caustic potash from time to time, keeping all
slowly dissolving by heat, in order to isolate the silex, destroying the
remainder. But in unburnt coal it is too difficult to dislodge the
carbon, and the acids have little effect upon it. I must, however, refer
to the calcination I effected by grinding up the substance, and then,
collecting it in a china vessel, placed upon a stove in a glass tube,
subjecting the whole to the action of the heat, while, at the same time,
a slight current of oxygen crossing the tube combined with the carbon
in creating carbonic acid. Experience has taught me, however, the
necessity of conducting this operation at a lower temperature, in
order to prevent the alkaline or earthy bases and metallic oxides,
which may be amongst the ashes, from forming vitreous silicates by
melting and mixing with the valves of the Diatomaceae. It is also
well to leave the glass tube, in which the fusing is going on, un-
covered, in order to watch its progress. The small residue obtained
through this process is to be put into a clean test-tube, adding nitric
acid and hydrochloric acid, and caustic potash, assisted by the heat of
a lamp to eliminate any alkaline or earthy base, and every trace of
metallic oxides. The last operation over, it only remains to wash
repeatedly with distilled water the very light clust Avhieh is left

292

NOTES AND MEMORANDA.

behind, letting it stand for some hours each time to settle, in order
to be sure of not losing the smallest particle of it in pouring off
the water. Those wrho follow this method exactly cannot fail to
succeed. The object may then be mounted with Canada balsam, or
in any other suitable medium ; and steadily and closely watching it
under the microscope, they will not be long before they see some
valves of diatoms, entire or broken.

Examination of the Animal Tissues for Starch — Mr. T. Taylor,
in the monthly Report of the Department of Agriculture to the
American Minister, makes some very astonishing statements. Those
who have been accustomed to examine the human tissues with powers
of from 300 to 800 diameters will be somewhat surprised at the
following assertion: — If about a cubic inch of liver, spleen, heart,
brain or muscle of the higher animals be immersed in two fluid-
ounces of caustic potash about twenty-four hours, at a temperature of
about 80° Fahrenheit, it will dissolve completely. On the addition
of acetic acid in excess, the potash will be neutralized, and a flocculent
precipitate will fall, which, by ordinary filtration, may be separated
from the liquid. Remove the filtrant by means of a sable-hair pencil,
taking care not to remove any of the fibre of the paper with the
animal matter. Place a- small portion of the filtrant on a capsule, and
add to it a drop of concentrated sulphuric acid, followed by one of the
tincture of iodine. Then place a portion of the composition on a
microscopic slide, covering it with a disk in the usual manner, and
examine it with a power of about 100 diameters Under these con-
ditions blue granules of animal starch and structural cellulose will
sometimes be seen, combined with amber-coloured albuminous matter.
Frequently starch and cellulose, although present, are not seen, but
by subjecting the composition to friction, and adding a little more
sulphuric acid and iodine, well-defined blue-coloured structural forms
become apparent.

An Instrument for Cleaning Thin Covering Glass has been thus
described by Mr. W. W. Jones to the Quekett Club. The paper is
fully published in the ‘Journal of the Quekett Club.’ The following
is the account of the instrument : — It consists of a small tube of brass
or steel, of about an inch in diameter and the same in height, into
which fits loosely a weighted plug. To the lower end of this plug is
cemented a piece of chamois leather. Another piece of leather is
stretched upon a flat piece of wood or plate glass to form a pad, which
completes the apparatus. The mode of using it is this. You place
the tube on the pad, breathe on the glass, drop it into the tube, put
in the plug, and then holding the tube well down on the pad you can
rub as much as you like with perfect safety, the weight of the plug
giving sufficient pressure. With this simple arrangement you will
find it almost as difficult to break the glass as many have hitherto
found it easy.

( 293 )

CORRESPONDENCE.

Mr. Stodder’s Defence.*

To the Editor of the ‘ Monthly Microscopical Journal.'

Boston, September 20, 1875.

Sir, — Mr. Wenham having introduced my name into his letter in
the September number of this Journal, with comments on some writing
of mine, I claim the privilege of replying, not from any personal feel-
ing in the matter, but that the history of the microscope object-glass
in the third quarter of the nineteenth century may be understanding^
read by our successors, say in the year 1925, which it could not be if
statements of that letter remain uncontroverted.

Mr. Wenham writes that Mr. Stodder “ refers to me with his
characteristic rancour as claiming arrangements belonging to others.”
I had not before been informed that rancour was one of my charac-
teristics. I certainly do not possess implacable personal malice, or
stedfast hate, synonyms of rancour, to Mr. Wenham ; on the con-
trary, I have great admiration of his ingenious mechanical and optical
appliances for the microscope, and have given him full credit for
them, and now feel under great obligations to him for originating the
discussion or controversy, which has done so much to bring into notice
both in America and Europe the merits of American workmanship. I
am not aware that I have heretofore charged Mr. Wenham with “claim-
ing arrangements belonging to others : ” perhaps I shall find before
I close something like that in his last paper. I have made that charge
against other parties, and am ready to substantiate the charge at the
proper time.

I have assuredly from time to time called attention to some of
Mr. Wenham’s mistakes, misrepresentations, and instances of forget-
fulness, endeavouring always to do so in as courteous terms and
phrases as Mr. Wenham uses himself. Surely he will not ask me to
select a more accomplished model. I now propose to specify without
“rancour” those in his last lucubration of September 1.

First, Mr. Wenham says his “ attention has been called to a letter
from Mr. Stodder, appearing in the £ Cincinnati Medical News ’ for
July, 1875, wherein he attempts to claim pre-eminence for Mr. Tolies,
and asserts that all recent improvements have been taken from him.”
There is no such letter from me in that issue of that journal ! or in
any other to which Mr. Wenham’s remarks can truly apply. There is
certainly a letter of mine in the May number of that periodical,
written in consequence of some editorial observations in an earlier
number (April, 1875), on the improvement of objectives in England,
in which I use Mr. Tolies’ name only as a consequence of its having

[* Our readers have by this time been fully informed on all points of this
discussion — if so it may be termed — which Mr. Stodder has been involved in.
"We must therefore positively decline the insertion of any further correspondence
on this subject. — Ed. 1 M. M. J.’]

CORRESPONDENCE.

204

been used by the editor. The paper cannot be fully understood except
in connection with the prior editorial.

This paper in the May number is possibly the foundation for the
text of Mr. Wenliam’s discourse ; but why such a mistake in the date?

I will now take up seriatim Mr. Wenham’s misrepresentations of
that paper, supposing it to be the one subject to his criticisms, know’-
ing of no other to which they can possibly apply.

“ Mr. Tolies is there boldly put forth as the maker of the best
objectives in the world.” Nothing from me in the paper that will
bear such an interpretation. The editor had said in the April article
on object-glasses, “ that since the superiority of R. B. Tolies’, of
Boston, new four-system lenses has been demonstrated, the distin-
guished English makers of objectives are abandoning their old formulas
and instituting new ones.” My paper used Mr. Tolies’ name only, as
a necessity after that remark.

When I put forth the claim attributed to me it must be supported
by such evidence as will be satisfactory to Mr. Wenham himself, and
to the next generation of microscopists.

“ It is imputed that Messrs. Powell and Lealand have based their
recent improvements on the fact of having seen Mr. Tolies’ ^th. . . .
I am in a position to say that they have not copied.”

I did not “ impute ” or “ insinuate ” that that highly respectable
firm, wliose work is the admiration of two continents, had “ copied.” *
I did say that their new j— inch glass was made after seeing the Tolies’
l-th, and I knew nearly a year before it was exhibited at the exhibition
of the Royal Microscopical Society that it was promised.

“ And further .... that they also considered that much-vaunted
object-glass not a subject for imitation.” Neither do I ! That £tli
possesses a peculiar characteristic, which has not been repeated in the
same degree in any one of the kind that I have seen, made since,
a characteristic in regal’d to which there is a difference of opinion
among experts, one, however, that was specified by a late writer in
England as proof positive of the surpassing excellence of a certain
object-glass of Andrew Ross.

Messrs. Powell and Lealand can learn my estimation of their work
by referring to the very paper in the May number of the ‘ Cincinnati
Medical News.’ If they thank Mr. Wenham for his championship, so
be it.

“ The four-system combination is claimed by Mr. Tolies as his
invention.” Never ; Mr. Tolies has made no such claim. He was
perfectly aware — perhaps before Mr. Wenham — that A. Ross had
made four-system objectives. It does not follow, however, that he
made the same combinations.

“ That in which one single front lens works both wet and dry is
not copied from America.” Does Mr. Wenham make that denial of
his own knowledge ? I repeat and insist on the statement as made in

* It would be as impossible for them to copy that ^th as it would be for
Mr. Tolies to copy any one of the many objectives of their make which have been
shown to him, without taking it entirely apart, dissecting it, i. e. destroying it.

CORRESPONDENCE.

*295

my paper in tlie May number of the ‘ News’ (will Mr. Wenham have
that copied in this Journal, that his readers may know the whole story?).
I there give the evidence that T. Ross saw Tolies’ work before he put
immersion fronts to his objectives. Will Mr. Wenham say that
Andrew Ross ever made immersion objectives intentionally ? Many dry
objectives will accidentally work immersion ; Mr. Wenham himself
explains why. That is a different thing from making them so inten-
tionally. So also many object-glasses may (as Mr. Wenham says of
A. Ross’s) work “ equally well ” both ways ; but both ways may be
very poor.

“ Having shown that the four-combination system is no novelty, I
must say the same of the doublet or duplex front now claimed by
Mr. Tolies as the great improvement of his lenses.” I challenge Mr.
Wenham, or anyone else — I rather like that formula — to produce any
evidence that Mr. Tolies has ever made any claim whatever about the
duplex front. Mr. Wenham has committed the mistake of thinking
that the duplex and the four-system are two different things, whereas
they are but two terms, either correct, for the same thing, one being
more euphonious than the other. Of course Mr. Tolies has not done
the ludicrous thing of claiming a name as an improvement of his
lenses !

But Mr. Wenham adds of the duplex, “ This wTas suggested by
myself years ago.” Indeed ! Who is “ claiming arrangements be-
longing to another ” now ? I am authorized to say that the “ duplex
front ” is unlike anything that Mr. Wenham has published ; has a
different optical function to perform, and must produce other results.
So Mr. Wenham must reserve for some future time his “gratifi-
cation ” for learning that his suggestion is coming into practical use,
by anything that Mr. Tolies has made.

So much for Mr. Wenham’s observations on my paper. I have
pointed out some eight or ten errors in his. I regret the necessity
of doing so, but it is due to history that they should not pass
unchallenged, for they would be accepted as true otherwise.

Charles Stodder.

Mr. Wenham’s Reflex Illuminator.

To the Editor of the ‘ Monthly Microscopical Journal .’

Boston, Mass., September 23, 1S75.

Dear Sir, — As the reflex illuminator of Mr. Wenham promises to
be one of the most valuable and useful of all the recently invented
adjuncts of the microscope, destined, I believe, to receive more atten-
tion than it yet has, I wish to ask Mr. Wenham, through this Journal,
a brief explanation, for the benefit of all microscopists, of his note,
page 156 of the September number.

Mr. Wenham writes, “ The total reflexion is the same irrespective
of any aperture of object-glass, and the field equally dark whether

296

CORRESPONDENCE.

this is used with water between the front lens or not.” Mr. Wenham
is here referring to the effect produced when the object is mounted
dry. Will he explain what will be the result if the object is mounted
in balsam, or other fluid ? Also, what is meant by “ water between
the front lens ” ?

Respectfully,

Charles Stodder.

Benech£’s No. 7 Objective.*

To the Editor of the 1 Monthly Microscopical Journal.’’

Baltimore, September 27, 1875.

Sir, — The flattering notices of Beneche’s No. 7 objective which
appeared in the ‘ M. M. J.’ induced me to order that objective from
its maker, and also, about the same time, to determine the purchase
of another by the Section of Microscopy and Biology of the Maryland
Academy of Sciences. The following letter was read and delivered
to Mr. L. Beneche by an agent of the Berlin bankers on the 16th
August last, but Mr. B. refused to make any reply. The Academy
of Sciences also has had no advices from the German optician,
although, as in my case, a sight draft for the money accompanied the
order.

“Baltimore, U.S.A., July 26, 1875,
“No. 82, Franklin Street.

“Sir, — On the 18th February, 1875, I sent you by mail my first
of exchange, No. 6621, drawn by Messrs. Kiimmer and Becker, of
Baltimore, in my favour, on Messrs. Anhalt and Wagener, of Berlin,
for the amount of forty-five rix marcs (45 R. mx.).

“ The money was in prepayment of a first-rate Beneche No. 7
objective and an adapter to the Society screw, leaving a possible
balance, which was to be returned to me.

“ On the 6th March, current, you drew the money, as your receipt
for it shows.

“ Not hearing from you, I wrote you on the 26th May, and again
on the 25th June ; but up to present date I have had no advices from
you, either about the money or the goods.

“ I now write to ask an explanation of conduct apparently so dis-
honourable, and to say that if you thus deal with your would-be
customers I will not fail to make the fact known. I wrote for the
objective on account of recommendations I saw in the London
‘ Monthly Microscopical Journal,’ and, trusting you, as I do all English

[* Mr. Johnston’s note arrived in time for insertion in the November number.
We, however, withheld it for a while, and in the meantime we wrote to Herr
Beneche', thinking it right to give him an opportunity of replying to certain
inquiries we made of him. Herr Beneche' has not had the common politeness to
acknowledge the receipt of our communication ; in fact, he has treated us as
he has dealt with Dr. Johnston, and therefore we consider the publication of
Dr. Johnston’s letter perfectly justifiable. — Ed. ‘ M. M. J.’]

CORRESPONDENCE.

297

tradesmen, I ordered from you, and also urged the Maryland Academy
of Sciences, Microscopical Section, to do the same. But your conduct
is alike in both cases, and reflects no credit on your house.

“ I leave this letter open that the gentleman delivering it may
know its contents and demand an answer.

“ Respectfully, &c.,

“ Christopher Johnston, M.D.

“Mr. L. Beneche, Berlin, Prussia.”

The Proposed Medal.

To the Editor of the ‘ Monthly Microscopical Journal .’

Montpelier Place, Brighton, October 8, 1S75.

Sir, — I am obliged to F.R.M.S., who, in your issue for the present
month, has drawn attention to my proposal of a prize medal for
objectives showing the best histological work. It is true we differ
widely upon the subject as yet ; nevertheless, I hope to bring him
over to my way of thinking ; for I am sure so good-humoured an
opponent will be amenable to reason, and will not be influenced by
any motives not in the true interests of the microscope.

The objections of F.R.M.S. to my suggestion seem to be chiefly
directed to the practical difficulty of carrying it out, and fairly and
impartially awarding such a distinction. He has, I regret to see, no
confidence in the integrity of the opticians themselves, nor in that
of those who would be selected as judges, and as little, I presume,
in the efficacy of any safeguards that might be adopted to secure
a real and unbiassed competition. Hence his opposition.

If, however, it can be shown that he is probably mistaken upon
the first of these points, and certainly so upon the second and third,
his hostility will, I am sure, cease ; and in that case I even trust
to claim him as a coadjutor in my scheme.

For my own part, I quite fail to see why the honour of the makers
of objectives is to be impugned ! I cannot believe that our cele-
brated opticians, the world-wide reputation of whose firms is the
well-earned guarantee at once of the thoroughness of their work and
the reliability of their word, would be at all likely to exhibit other
than the most upright conduct in the matter. I am now, without dis-
paragement of foreigners, speaking of English opticians, being
naturally best acquainted with them. But if their brethren of
repute in other countries resemble them, then I feel no doubt that
all those sad, and let me say humiliating apprehensions of backstair
interest and underground motives entertained by F.R.M.S. will be
found to vanish when submitted to the test of actual trial.

If, however, my confidence in the independence and concurrent
straightforwardness of the opticians were unhappily not justified by
the facts, we should still have the security of the unimpeachable
ability and fairness of the judges. These would naturally be not

298

CORRESPONDENCE.

mere amateurs with crotchets, but gentlemen professionally engaged
in scientific histological work : men like Beale, Burdon Saunderson,
Carpenter, Braxton Hicks, Klein, and others of the many compe-
tent teachers of histology in our medical schools and colleges. I
apologize for using the names of these gentlemen without permission ;
but it will be understood that I do so because they are representative
men, and belong to a class in whom all concerned would have the most
complete confidence.

Further than this, in the interest of all parties, competitors, judges,
and the scientific public, it would be well to observe the precautions
adopted in judging prize essays. Thus the competing objectives
should be sent in with a motto, accompanied by a sealed letter con-
taining the maker’s name and the same motto, but not to be opened
until after the award. It would be an easy matter to make it a con-
dition of competition, that all lenses sent in should be mounted in
brasswork of a given pattern. Makers could adhere to such pattern
afterwards or not, as they pleased.

F.R.M.S. hints that such a medal, if given at all, should be offered
more frequently than once in three years. I have no objection to its
being made an annual prize; but that is matter of detail, and does not
touch the principle. It should be left for the consideration of the
Society presenting it.

These are a few of the observations which occur to me as a fitting
reply to the objections of F.R.M.S., and I hope he will not only
think them a propos, but also that they fairly meet what he has said
against the proposition.

With regard to Mr. C. Stodder’s remarks, although I can make no
abatement whatever from the weight of the authorities given in my
former letter, I freely acknowledge that under the actual circumstances
I have perhaps stated too broadly the view that objectives best calcu-
lated for the display of diatoms are not equally suited for histological
work. On the other hand, it will be sufficient to remind him that
what he claims to have settled, as I understand him with his own
glasses, is exactly the point in dispute ; and that no mere claim, how-
ever confidently made, can of itself settle anything. Epithets like
that he has chosen to characterize my views, he will hardly expect
to be complimented upon ; they are inapplicable, and greatly to be
deprecated as destructive of the mutual confidence and esteem which
should exist amongst scientific men.

To return. Whether Mr. Stodder and those who still think with
him, or those of the opposite school, are right, is of no consequence at
all to the matter in hand. The gold medal should not be offered for
objectives constructed upon any particular principles, but for such
as are capable of doing the best histological work, according to a
standard fixed by the Society. The aperture, and all other circum-
stances affecting the optical question, should be left entirely to the
competing opticians. Those of them who believe that the highest
angles are best under all circumstances, will no doubt send their most
approved diatom lenses; while those who think that there is a material
difference between the work which is confined to the examination of

CORRESPONDENCE.

299

surfaces, and that which deals with the interior substance of tissues,
will no doubt construct glasses to meet that difference.

In common with all really interested in the perfection of micro-
scope objectives, I cannot but greatly admire the beautiful perform-
ance of recent high-angled lenses in the display of diatoms. There
cannot be a doubt we owe very much to their constructors, and it
is to my mind probable we shall owe more still. On the other hand,
as a practical histologist I confess with regret that these lenses,
whether equal to others or not in histological work, are at least greatly
inferior in this respect to the power they themselves exhibit in the
case of diatoms. If this be so, and high-angled glasses have so to say
already done their best for histology, it is imperative that other
constructions be fairly tried, and the catalogue exhausted if need be,
in the attempt to arrive at the greater excellence, which is still so
much to be desired. I see no other way in which this is likely to
be done than by the encouragement and reward of makers in such a
competition as I suggest.

I am, Sir, obediently yours,

R. Branwell, M.R.C.S.E., F.R.M.S.

The Immersion Aperture Question: Reply to Mr. Wenham.

To the Editor of the ‘ Monthly Microscopical Journal.''

224, Regent Street, London, November 11, 1875.

Sir, — Mr. Wenham states that the root of the present immersion
aperture question is to be found in his contributions to the Quarterly
Journal of twenty years ago : I must express my dissent. The question
then discussed had reference to the illumination of balsam-mounted
objects, — had no reference whatever to the matter now in hand, which
concerns immersion lenses only, in relation to their image-forming
aperture capacity.

The argument maintained by Dr. Woodward is confirmed by the
use of the Reflex Illuminator with those immersion lenses which claim
from their construction to refract via water image-forming rays of
greater obliquity than those corresponding to the maximum trans-
missible by a dry objective. In the experiment alluded to by me,
the Illuminator is used as a means of providing rays incident on
the object in balsam (and consequently on the field) at greater in-
clination than the angle of total internal reflexion between balsam
and air ; these rays emerge from the cover-glass conditionally on
there being water contact between the cover and the objective front,
but with air as the external medium they do not emerge. Mr. Wen-
ham says that when fluid is introduced between the lens and cover
“ . . . .all total reflexion is gone ; ” it is this very fact which gives
its value to the experiment. For what is the inclination of those
rays which pass through the water and are so refracted by the ob-
jective as to produce a luminous field? Is it greater than corresponds
to the maximum transmissible by a dry objective ?

In describing the action of the Reflex Illuminator, Mr. Wenham
said, “ . the most oblique [light] that we can obtain by ordinary

VOL. XIV. Y

300

CORRESPONDENCE.

means, cannot strike on tlie object at an angle greater than 41° if it is
either in balsam or on tbe slide, but on this principle we are dealing
with rays entirely7 beyond this angle.” *

If, by suitable adjustment of the mirror, we can ensure tbe illu-
mination of tbe object solely with rays from tbe Illuminator of greater
obliquity than 41° — which is admitted by tbe construction — tbe field
rays must also be of greater obliquity than 41° ; and if, with pneumo-
lenses these rays are necessarily lost by total reflexion at tbe cover-
glass, whereas with certain immersion lenses a portion is refracted
into a luminous field ; it follows that rays beyond tbe “ critical ”
angle from balsam to air are “ got through ” tbe immersion lens, and
Mr. Wenham’s dictum that “no object-glass can collect image-forming
rays beyond this limit ” is confuted.

With reference to tbe “ simple demonstration” cited in Mr. Wen-
bam’s postscript for my special benefit, I observe be bad already
favoured us with tbe method of procedure.! I try tbe experi-
ment : — He says, “ Focus tbe top surface of tbe plate glass with an
immersion -|tb having tbe highest available aperture;” be must here
mean to request me to focus tbe immersion lens used as a dry lens,
because later on be asks me to look sharply while tbe water inter-
medium is applied. I take up Hartnack’s No. 9 immersion having
tbe highest available aperture, and find it will not focus tbe definition
with air as tbe intermedium : tbe experiment fails when tried with such
an immersion lens ! But in order to meet him, I take Dallmeyer’s new
^ in which tbe immersion front can be used wet or dry, and, adjusting
it to tbe “ dry ” point, focus sharply tbe image of tbe line on the sur-
face of tbe plate glass. I remove the ocular and allow tbe rays from
tbe lamp-flame to traverse tbe optical body and tbe objective, they
cross at tbe focus and form a luminous disk on tbe ground side of tbe
plate glass ; tbe angular diameter of this disk is about 55°. I intro-
duce tbe water film ; but it occurs to me I shall no longer be mea-
suring tbe angle of tbe image-forming cone of rays,— tbe focus is no
longer on tbe glass surface,— tbe lens must be adjusted for “ immer-
sion.” As I do this, tbe angular aperture increases, and when I reach
tbe point at which tbe image-forming rays are sharply focussed, tbe
disk of light has increased to 70° ! With air as tbe intermedium, tbe
image-forming aperture is 55° as shown by tbe disk of light ; with
water it is 70°. But Mr. Wenbam asserts that whether there is water
or air as tbe intermedium “ not tbe slightest change is visible in tbe
diameter of tbe disk ” ! and in bis account of the experiment in
No. lxiii., p. 116, be stated “ It made no difference in tbe angle
whether water is admitted in front lens or not .... but in each case
the object-glass must be focussed on the glass surface .” I must leave
him to explain tbe discrepancy between bis result and mine.

When Dr. Woodward forwarded Professor Keith’s diagram and
trigonometrical computation to London in support of bis position, be
wrote : ! “I cannot be expected to pay attention hereafter to tbe
assertion of anyone who may continue to bold that it is ‘ theoretically
impossible ’ to construct immersion objectives with a balsam aperture

* ‘M, M. J.,’ No. xlii., p. 241. f Ibid., No. lxiii., p. 4! 6.

I Ibid., No. lxix., p. 127.

CORRESPONDENCE.

301

greater than 82° of ‘ image-forming ray’s,’ unless he can show some
material error in Mr. Keith’s computations.”

In replying,* Mr. Wenham discovered no better ground on which
to base his objections than to suggest that the data given by Mr. Tolies
were uncertain. He said, “ Mr. Tolies, from whom all measurements
come, has repeatedly supplied diagrams to suit his purpose ; ” and
again, “ Of course Messrs. Woodward and Keith are not responsible
for data, but the former gentleman tells us it is ‘ a diagram accurately
constructed in accordance ivitli the computed results ’ ; having therefore
been drawn to suit the proposition, it may be dismissed ” ! This
estimate of the value of his opponent’s diagram differed from that he
gave of his own with his “New formula,” thus : j “Diagrams, how-
ever, are surprisingly accurate in their capability of indicating causes
and results in the microscope and object-glass.”

For my part, the question being put in the form of a mathematical
demonstration, I considered no authority would be recognized as of
value in criticising it except that of a professional mathematician ; I
therefore placed it in competent hands. Mr. Wenham says that
“ however consoling to Mr. Mayall the opinion of the high mathe-
matical authority may be, his anonymous verdict will not be considered
important by others.” Let me assure Mr. Wenham the verdict is none
the less consoling to me, nor will it be considered less important by
Dr. Woodward, Professor Keith, and others, from the fact that it was
given by Professor G. G. Stokes, Secretary of the Royal Society.

Your obedient servant,

John Mayall, jun.

The Aperture Question.^

To the Editor of the ‘ Monthly Microscopical Journal .’

Sir, — Nothing can be easier than to dispose of Mr. John Mayall,
jun.’s, claim to have discovered a “ most elegant practical” refutation
of Mr. Wenham’s position on the aperture question.

His claim is based on the supposition that in the Reflex Illumi-
nator none of the rays are transmitted when a dry objective is used
on “Moller’s Probe-Platte ” (!) ; or, in other words, that all the rays
fall within the critical angle, and are consequently totally reflected
from the upper internal surface of the slide.

If your readers will refer to the seventh volume of the ‘ Monthly
Microscopical Journal,’ page 241, they will find in Mr. Wenham’s
own paper, when describing his new appliance, the most complete and
conclusive refutation of this assumption ; for after saying that he
will anticipate a few objections to the arrangement, he adds :

“It may be said that the rays reflected from the lower end of
the facet are just without the angle of total reflexion, and might
enter true, and I had intended to stop off a small segment of the lens
at this place, but found it so desirable, in many objects, to admit a little
light, that I preferred it without alteration. It is easy to get a black
field in all cases by mere mirror adjustment.”

* ‘ M. M. J.,’ No. lxxi., p. 221. f Ibid., No. lii., p. 1G4.

[J This letter has stood over from the last number. — En. ‘ M. M. J.’]

Y 2

302

CORRESPONDENCE.

The answer to Mr. John Mayall, jun.’s, question, Whence comes
the luminous field in the immersion lens if not from its having the
power to collect rays which are totally reflected when the dry lens is
used ? is thus abundantly answered. It may come from the rays
reflected from the lower end of the facet intentionally left to admit
the light.

I must decline to argue with Mr. Carr whether when the image
under a ^th breaks up by the test of deep oculars its amplifying
power is “about 1000 diameters” only? The answer is so obvious
that the discussion is puerile: the initial power is greater. Equally
unprofitable would it be to debate as to what Mr. Hogg did* or did
not say in his letter ; at pages 97 and 98 of your Journal it will be
found at full length, with the “ non sequitur ” at which he has arrived.

Your obedient servant,

Crito.

Chromatic and Spherical Aberration.

To the Editor of the 1 Monthly Microscopical Journal'

1, Bedford Square, November 12, 1875.

Sir, — Dr. Pigott’s contribution on the question of chromatic and
spherical aberration has at least the demerit of introducing confusion
into this subject. Would he have us believe he has discovered that
everyone up to the present time, save himself, has held erroneous
views on the well-recognized distinctions between these aberrations ?
Dr. Pigott’s attempt to persuade us that they “ are identical in the
nature of things,” requires some explanation; for it appears to me
he makes “ confusion worse confounded,” by calling two properties
of lenses by the same name ; whether by so doing this will add to the
clearness with which the subject is usually apprehended is a matter
demanding further consideration.

H, as he says, “ all chromatic aberration involves spherical aber-
ration,” will he tell us how it happens that in the mathematical
formula given by Herschel and other writers on optics, for the elimi-
nation of chromatic aberration, the expressions for forms and order
arc not found ? And again, if these aberrations “ are identical,” why
have they been discussed under separate and distinct propositions ?
and why do practical opticians continue to treat them as separate and
distinct matters, knowing well that the conditions essential to the
correction of chromatic aberration do not necessarily involve those of
spherical aberration, and vice versa ? They may, as Professor Parkin-
son says, be corrected in one and the same combination ; nevertheless,
the aberrations are in themselves perfectly distinct phenomena.

I cannot well give Dr. Pigott a higher authority on this subject
than the Astronomer Royal, whose words are, “ The laws of spherical
aberration and of chromatic aberration both in microscopes and tele-
scopes are totally different .”

I remain yours, &c.,

Jabez Hogg.

( 303 )

PROCEEDINGS OF SOCIETIES.

Royal Microscopical Society.

King’ College, November 3, 1875.

H. C. Sorby, Esq., F.R.S., President, in the chair.

The minutes of the preceding meeting were read and confirmed.

The subjoined list of donations to the Society was read, and the
thanks of the meeting voted to the donors.

The President called attention to a series of photo-micrographs —
included in the list of donations — presented by Dr. Rollins, and taken
with a Tolies’ objective. They represented a number of dental
sections, and were handed round for the inspection of the Fellows.

The President gave a highly interesting account of a new method
of measuring bands in spectra, illustrating the subject by drawings
upon the black-board. (A paper upon the subject will be found at

p. 269.)

A vote of thanks to the President for his communication was put
to the meeting by Mr. Slack, and carried unanimously.

A paper by Dr. J. J. Woodward, of the United States Army
Medical Department, was read by the Secretary ; it was entitled,
“ Notes on the Markings of Frustulia Scixonica ,” and had reference
to some observations in the £ Monthly Microscopical Journal,’ vol. ix.,
p. 86 ; but more particularly to a paper by Mr. Hickie, published in
the number for last July. Photographs in illustration accompanied
the paper, the text of which will be found printed at p. 274.

Mr. Slack said that in the July number of the Journal there was
a figure of this diatom copied from Dr. Schumann’s work. The figure,
from ‘ Die Diatomeen der Holien Tatra,’ was rather broader in the centre
than Dr. Woodward’s photograph, and slightly constricted just before
the nodules at each end. In his text he, Dr. Schumann, said, “ Frus-
tulia Saxonica occurs in the following forms : Naviculia crassinervia,
Brebisson ; Navicula cuspulata, Ktitzing. (Sie tritt in fulgenden
Fcrmen auf), “ one like the first form, but which showed two strong-
marginal border stripes on each side,” is thus described : “ In refer-
ence to the kind and number of the striae ( Biefen ), all these forms
agree in the chief characters, so that the formula which describes the
first suits the others. With oblique light the walls of a single cross
stripe appear like distinct strife, and thus the number of the strife is
apparently doubled.” After some remarks about focussing, he says,
“ I agree with Grunow as to the nodules.” In Pritchard, N. cus-
pidata, Ktz., is given as identical with N. fulva, Em.

The President, in proposing a vote of thanks to the author of the
paper, thought the subject was one of great interest, because it was
certainly most desirable for all to know -whether things which they
saw really existed or not, because many things which were seen
might under certain circumstances be due to interference. He
thought that the photographs sent in illustration fully bore out
Dr. Woodward’s remarks. He had not himself paid very great atten-

304

PROCEEDINGS OF SOCIETIES.

tion to the study of diatoms, though quite enough to enable him to
see the importance of Dr. Woodward’s observations.

Mr. J. Mayall, jun., said : Dr. Woodward has made an exhaustive
examination of one of the finest known test-diatoms by means of pho-
tography, and he has supplemented this by critical observations on
the true definition of the diatom, which, coming from so practised an
observer, must together go far to settle the question — so far as it can be
settled with the optical means at present available. I am particularly
interested by what appears to me an original observation of Dr. Wood-
ward’s,— I refer to his suggestion for readily distinguishing diffraction
lines from real lines existing in the object. He observes the diffrac-
tion lines have this peculiarity, that they appear to increase or
decrease in number as we approach to or recede from the focus of the
real lines ; whereas really existing lines in an object do not appear to
vary in number when viewed slightly within or without the true
focus. This is, I think, a highly important distinction, and if care-
fully mastered by microscopists will lead to greater certainty of inter-
pretation. Dr. Woodward also calls our attention to the fact that
photography gives as much apparent reality to the images of diffrac-
tion lines as to those of lines actually existing in the object : this is
manifest in the photographs of Frustulia Saxonica which he has for-
warded to us in illustration of his remarks. With regard to the
distinction attempted to be drawn by Mr. Hickie between the de-
finition of the diatom Frustulia Saxonica and what he alleges to be
another diatom going by the name of Navicula crassinervis, I know
the diatom well, and have always regarded the two names as applying
to the same object. Moller uses either or both names in describing
it, and I venture to think his opinion is far more valuable than
Mr. Hickie’s.

Mr. Slack said he did not know the object, but he thought that the
fact mentioned by Dr. Schumann that there were two marginal edges
was quite sufficient to account for the diffraction lines.

The President announced that arrangements had been made for
carrying out the proposal to hold a scientific evening on the 24th
instant ; also, that at the next ordinary meeting a paper would be read
by Professor T. Kupert Jones, entitled, “ Remarks on the Forami-
nifera, with special reference to their Variability of Form, illustrated

by the Cristellarians.

Donations to the Library from October 6, 1875 :

From

Nature. Weekly The Editor.

Athenaeum. Weekly Ditto.

Society of Arts Journal Society.

Transactions of the Linnean Society. Five parts Society.

Journal of the Linnean Society. No. 8 Ditto.

Transactions of the Royal Irish Academy. Fourteen parts Academy.
Proceedings of the Royal Irish Academy. Five parts . . . . Ditto.

Canadian Journal. No. 83.

Bulletin de la Socie'te Royale de Botanique de Belgique.

Five parts Society.

Ten Micro-photographs of Sections of Teeth, illustrative of
Dental Surgery, by Dr. W. H. Rollins, of Boston, U.S.A.,
produced by Tolies’ lenses Chas. Stodder, Esq.

PROCEEDINGS OF SOCIETIES.

305

The following gentlemen were elected Fellows of the Society : —
George Manners, Esq. ; William Hadden Beeby, Esq. ; George
Hastings, Esq., M.D.

Walter W. Beeves,

A ssist. -Secretary .

Medical Microscopical Society.

Oct. 15, 1875. — Jabez Hogg, Esq., Vice-President, in the chair.

The Cochlea in Birds. — Dr. Pritchard explained and exhibited
specimens illustrative of the structure of the cochlea in birds.

Artificial Fibrillation of Hyaline Cartilage. — Mr. Cresswell Baber •
exhibited specimens illustrating his paper in the ‘Journal of Ana-
tomy and Physiology ’ on the above subject. His observations were
based upon a statement by Tillmanns, in Max Schultze’s ‘ Archives,’ to
the effect that fresh hyaline cartilage can be fibrillated by macerating
it for several days in a solution of permanganate of potash, or in
10 per cent, solution of chloride of sodium. Mr. Baber showed that
fibrillation of the matrix can be produced by macerating sections of
hyaline cartilage in solution of chloride of sodium (both 10 and £ per
cent.) in lime water, or in baryta water, and in each case after the
maceration applying momentary pressure to the glass covering the
section before examining it. The fluid that acted most rapidly was
baryta water, which produced the fibrillation in half an hour ; while
permanganate of potash that Tillmanns prefers, he had found uncertain
in its action. Mr. Baber had found the fibrillation of the cartilage
matrix in all cases in which he had searched for it, and concluded
therefore with Tillmanns, that the hyaline matrix is composed of fine
fibres held together by an interfibrillar cement substance that can be
dissolved by certain reagents. A discussion followed, and the meeting
then resolved itself into a conversazione.

Quekett Microscopical Club.

Ordinary Meeting, September 24. — Dr. John Matthews, F.B.M.S.,
President, in the chair.

A paper by Mr. James Fullagar, Hon. Assistant-Secretary to the
East Kent Natural History Society, “ On the Development of Actino-
phrys Sol,” was read. In this paper the results of four months of con-
tinued observation upon a number of those organisms — kept carefully
isolated — were recorded. The various changes which took place can-
not be fully described without drawings, but may be shortly indicated
as follows : A group of eight, which Jaad become closely united, were
isolated and examined. In this state they were seen to feed voraciously.
The author considered the fusion of several specimens to be a prepara-
tion for encystment. When fully fed, they separated into their
original number, assuming their well-known form, the pseudopodia
becoming greatly extended. After some time the pseudopodia were
gradually withdrawn, and in about six hours had disappeared, the
centre of the body became darker, and the contractile vesicle ceased
to pulsate. The central part of the body then divided into two equal

306

PROCEEDINGS OF SOCIETIES.

globular masses, surrounded by the original spherical casing, outside
of which was a thin transparent film. In twelve hours this casing lost
its spherical form, the central globes altered in shape, became gibbous,
and separated from each other. After some time they again ap-
proached, and in an hour from the time of touching they again became
fused into one globule, much smaller than the original size. To this
point the same changes took place in each of the eight specimens.
One of the group was then observed to move about among the others,
gliding between and around them, and throwing out branched pseudo-
podia. This movement was continued, with short intervals of rest, for
more than forty-eight hours. The other seven also exhibited slight
movements from time to time, and protruded amoebiform pseudopodia,
somewhat resembling Amoeba bilimbosa. From some of the specimens
a cloudy translucent matter exuded, from which issued minute globules
and clear and transparent amoeboid bodies, sometimes resembling
Amoeba princeps, and at others A. porrecta, A. Umax, and A. actino-
phora.

In a note to his paper, Mr. Fullagar describes other changes,
indicating the development of young Actinophryans from encysted
specimens by segmentation, and a change from the amoeboid form to
that of an oval or pear-shaped body with one very thick and long
pseudopodium. In some cases also the globular bodies in approaching
each other became flattened, and again separated without coalition.

The paper was illustrated by a large number of drawings, showing
every stage of development.

Beading Microscopical Society.*

October 12, 1875. — At this, the first meeting of the Society for
the winter session, after the transaction of the usual business, and the
reading of a letter from Major Lang, the following resolution, moved
by Mr. J. G. Tatem, and seconded by Dr. Shettle, was unanimously
passed :

“ That this meeting receives with the deepest regret Major Lang’s
resignation of the office of President, which, from the very commence-
ment of the Society, he has with so much courtesy, and profit to the
members, kindly filled.

“ That the members of the Society regret that the only return they
can make for the frequent self-denial which their late President’s
regular attendance at the monthly meetings must have involved, and
for his constant devotedness to the interests of the Society in every
way, is to express their hearty and unanimous recognition of all the
services he has so long rendered, for which they tender their best
thanks ; and they also indulge the hope that he will allow them to
consider him honorary Vice-President and Corresponding member,
which they trust they may for many years be permitted to do.”

At the conversazione, which closed the meeting, many objects of
interest were exhibited.

* Report supplied by Mr. B. J. Austin.

( 307 )

INDEX TO VOLUME XIV.

A.

Abbe’s, Professor, Extracts from Mr.
H. E. Tripp’s Translation of, ‘ On
the Microscope,’ 191, 245.

Aberration, on the Identical Characters
of Chromatic and Spherical. By
Dr. Royston - Pigott, F.R.S., 232,
282.

Allman, G. J., M.D., Recent Progress
in our Knowledge of the Ciliate
Infusoria, 170.

Angular Aperture, the Measurement
of. By J. W. Stephenson, Esq., 3.

the Slit as an Aid in

Measuring. By Professor R. Keith,
284.

Animals and Plants, the Law of Em-
bryonic Development in, 144.

Aperture, Angle of, 90.

Archer, Mr., his Opinion of the Ame-
rican Ouramoeba, 87.

Archimedea remex, 169.

B.

Bacterium termo, on the Existence of
Flagella in. By W. H. Dallinger
and J. J. Drysdale, M.D., 105.

Bastian, Dr. H. Charlton, The Micro-
scopic Germ Theory of Disease;
being a Discussion of the Relation
of Bacteria and Allied Organisms to
Virulent Inflammations, Fevers, &c.,
65, 129.

Beale, Dr. Lionel S., on the Origin
of Life, 81.

Beatty, Dr. D., on Double Staining of
Wood and other Vegetable Sections,
57.

Blood-corpuscles, a Mode of Counting
the White and Red, 148.

Globules of a Nemertian Worm,

17.

Effects of Curare on the

Emigration of White, 205.

Bony Tissue prepared with Aniline
Dye. By M. Ranvier, 202.

Brain of the Insane, Minute Structure
of the, 16.

Braithwaite, Dr. Robert, on Bog
Mosses, a Monograph of the Euro-
pean Species, Sphagnum Portoricense ,
47 ; Sphagnum macrophyllum , 48.
Bucephalus polymorphus, Notes on.
By Charles Stewart, F.L.S., 1.

C.

Cabbages, Cause of Disease in, 206.
Carpenter, Dr., on the Origin of the
Red Clay found by the ‘ Challenger,’
255.

Ceplialosiphon and a New Infusorion.

By Dr. C. T. Hudson, 165.

‘ Challenger,’ the Microscopic Work of,
288.

Chara, the Germination of, 206.

Coal, Preparing Sections of, 148.
Correspondence : —

Badcock, John, 149, 215.

Branwell, R„ 101, 297.

Carr, Edmund, 216.

Crito, 154, 301.

Dodd, Albert F., 99, 209.

Garner, Robert, 102.

Guinaraens, A. de Souza, 35, 209,
260.

F.R.M.S., 218.

Hickie, W. J., 32, 211.

Hogg, Jabez, 97, 152, 302.

Johnston, Christopher, 93, 296.
Mayall, John, jun., 93, 150, 214, 299.
Piffard, Dr. H. G., 37.

Slack, H. J., 98, 151.

Sorby, H. C., 37.

Stodder, Charles, 208, 293, 295.
Taylor, Thomas, 101.

Thuet, Clement, 259.

Tolles, R. B., 209.

Wenham, F. H., 155, 263.

D.

Dallinger, W. H., and J. J. Drysdale,
M.D., on the Existence of Flagella in
Bacterium termo, 105.

Diatomace;p, How to Prepare the, 90.

308

INDEX.

Diatom-lines, on Dr. Schumann’s For-
mulae for. By W. J. Hickie, 6.

Diatom, an Animal-like, 255.

Diatoms, the Examination of Coal for,
291.

Disease, the Microscopic Germ Theory
of. By Dr. H. C. Bastian, 65, 129.

Dust, Atmospheric, 141.

Volcanic, of Barbadces, the Struc-
ture of, 143.

Dytiscus, the Functions of the Frontal
Ganglion in, 141.

E.

Edwardes, Kev. D., on the Unit of
Linear Measurement, 49.

Einee, Dr. T. H., on the Structure and
Motion of the Spermatozoa, 25.

Epithelium, on Conjoined. By Dr. S.
Martyn, 59.

F.

Fleming, Dr. W. J., a Modification of
Dr. Rutherford’s Freezing Micro-
tome, 79.

Fripp’s Translation of Professor Abbe'’s
Paper on the Microscope, Extracts
from, 191, 245.

Frustulia Saxonica, Note on the Mark-
ings of. By Dr. J. J. Woodward,
274, 279.

Fungi, the Fecundation of Tliecaspore,
203.

G.

Glass ruby-tinted with Gold, seen
with the Micro-spectroscope, 207.

H.

Harrington, Professor, on the Cha-
racter of the Starch-granule, 18.

Hickie, W. J., on Dr. Schumann’s
Formulae for Diatom-lines, 6.

High Powers, on a New Mode of Illu-
minating for. By Dr. Whittell, 109.

Hudson, Dr. C. T., on Cephalosiphon
and a New Infusorion, 165.

• on a New Melicerta, 225.

I.

Immersion Objective, Poweil and Lea-
land’s New a tb, 207.

Inflammation of Connective Tissue, the
Microscopic Appearances in, 19.

Infusoria, Recent Progress in our
Knowledge of the Ciliate. By G. J.
Allman, M.D., 170.

Instruments, Optical, Professor Abbe’s
New Book on, 208.

J.

Jones, Mr. W. W., on an Instrument
for Cleaning Thin Covering Glass,
292.

K.

Keith, Professor R., the Slit as an Aid
in Measuring Angular Aperture, 284.

Kitton, F., on the Number of Striae on
the Diatoms on Moller’s Probe-
Platte, 45.

L.

Leidy, Professor, Observations on some
Marine Rhizopods, 26.

Life, on the Origin of. By Dr. L. S.
Beale, 81.

Limulus, the Development of the
Nervous System in, 141.

Lobster, Development of the European,
203.

Lymphatics of the Choroid and Retina,
148.

M.

Martyn, Dr. S., on Conjoined Epithe-
lium, 59.

Measurement, on the Unit of Linear.
By Rev. D. Edwardes, 49.

Melicerta, a New Species of. By
C. T. Hudson, LL.D., 225.

tyro, 225.

Michels, John, the Microscope and
its Misinterpretations, 52.

Micro-ophthalmoscope, a, 91.

Micro-photographs, Anatomical, 207.

Microscope, the, and its Misinterpre-
tations. By John Michels, 52.

Microscopic Work of the 4 Challenger.’
A Letter from Professor Huxley to
‘ Nature,’ 288.

Microscopy at the American Associa-
tion, 91.

at the Bristol Meeting of the

British Association, 92.

Microtome, a Modification of Dr. Ruth-
erford's Freezing. By Dr. W. J.
Fleming, 79.

Mineralogy, Use of the Microscope in,
257.

Moths, Perforating Proboscis. By
Henry J. Slack, 235.

INDEX.

309

N.

New Books, with Short Notices: —
Outlines of Practical Histology. By
\V. Rutherford, M.D., 287.
Practical Hints on the Selection and
Use of the Microscope. By John
Phin, U.S.A., 287.

O.

Object-glass, on a New Form of. By
M. Clement Thuet, 259.

of Professor Hasert, 260.

Powell and Lealand’s Jth,

207.

Objectives of the Academy of Natural
Sciences of Philadelphia, an Ameri-
can View of the recently expressed
Opinion as to, 82.

Ouramceba, Mr. Archer’s Opinion of
the American, 87.

Ova, the Salmon, that were sent to
New Zealand, 91.

Ovule, the Minute Structure of the, 19.

P.

Packard, Mr. A. S., jun., on the Deve-
lopment of the Nervous System in
Limulus, 141.

Petromyzon, the Spermatozoa of, 143.
Pigott, Dr. Royston-, F.R.S., on the
Identical Characters of Chromatic
and Spherical Aberration, 232, 282.
Placenta, Comparative Anatomy of the.

By Professor Turner, 204.

Potato Fungus, the Resting Spores of
the. By Worthington G. Smith, 110.
Powell and Lealand’s New ■§■ inch, 207.
Probe-Platte, the Number of Strife on
the Diatoms on Moller’s. By F.
Kltton, 45.

Proceedings of Societies: —

Adelaide Microscopical Clilb, South
Australia, 103, 158, 224.

Academy of Natural Sciences, Phila-
delphia, 15S.

Faiimount Microscopical Society,
Philadelphia, 220.

Medical Microscopical Society, 41,
305.

Memphis Microscopical Society, 104,

220.

Quekett Microscopical Club, 42, 103,
157, 219, 305.

Reading Microscopical Society, 306.
Royal Microscopical Society, 37, 264,
303.

San Francisco Microscopical Society,
161, 221.

Protozoan, the Nutrition of the, 92.

R.

Red Clay, the Origin of the, found by
the ‘ Challenger,’ 255.

Reflex Illuminator, Notes on the Use
of Mr. Wenham’s. By Henry J.
Slack, F.G.S., 5.

Wenham’s. By Mr. S.

Wells, 30.

Rhizopods, Observations on some Ma-
rine. By Professor Leidy, 26.
Rotifera, Dr. Hudson’s Paper on the,
255.

S.

Semper, Herr, on Trochosphera aiqua-
torialis, a Spherical Rotifer found in
the Philippine Islands, 237.

Slack, Henry J., Notes on the Use of
Mr. Wenbam’s Reflex Illuminator,
5.

on Perforating Proboscis

Moths, 235.

Smith, Worthington G., on the Rest-
ing Spores of the Potato Fungus,
110.

Soire'e, Microscopical, at the British
Association, 207.

Sorby, H. C., F.R.S., on a New Method
of Measuring the Position of the
Bands in Spectra, 269.

Spectra, on a New Method of Measuring
the Position of the Bands in. By
H. C. Sorby, F.R.S., 269.

Spermatozoa, Structure and Motion of
the. By Dr. T. H. Einer, 25.

Sphagnum Portoricense, 47.

macrophyllum, 48.

Spinal Chord as seen with the Polari-
scope. By Dr. Webber, 291.“

Sponges, the Siliceo-fibrous, 143.

Starch, the Examination of the Animal
Tissues for, 292.

Granule, the Character of the,

18.

Stephenson, J. W., Esq., on the Mea-
surement of Angular Aperture, 3.

Stewart, Charles, F.L.S., Notes on
Bucephalus polymorphus, 1.

T.

Thin, Dr. G., on the Microscopic Ap-
pearances in Inflammation of Con-
nective Tissue, 19.

on the Structure of Con-
nective Tissue, 145.

Thin Covering Glass, an Instrument
for Cleaning. By W. W. Jones, 292.

310

Index.

Tissue, the Structure of Connective.
By Dr. (4. Thlnt, 145.

Inflammation of Connective. By

Dr. Thlnt, 19.

Trochosphaera sequatorialis, a Spheri-
cal Rotifer found in the Philippine
Islands. By Herr Semper, 237.

W.

Wells, Mr. S., on Wenham’s Reflex
Illuminator, 30.

Whittell, Dr., on a New Mode of
Illuminating for High Powers,
109.

Wood and other Vegetable Sections,
the Double Staining of. By Dr.
D. Beatty, 57.

Wood, Mr. W. W., on an Animal-like
Diatom, 255.

Woodward, Dr. J. J., Note on the
Markings of Frustulia Saxonica, 274,
279.

END OF YOL. XIY.

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET AND CHARING CROSS.

New York Botanical Garden Library

3 5185 00287 2206