RESEARCHES ON K.ARYOKINESIS AND CELL DIVISION.
85
REVIEW of RECENT RESEARCHES on KARYQKINESIS 1 and
CELL DIVISION. By J. T. CUNNINGHAM, B.A., Scholar
of Baliol College, Oxford.
(With Plate VI.)
THE following is a short account of the latest investigations into the metamorphosis which nuclei undergo in the
process of indirect division, and of the present state of
knowledge and speculation concerning the structure of the
cell and the phenomena of its life.3
Methods of Examination.—The structure of the nucleus
and cell, and the forms which the elements of the nucleus
assume during.division, can only be made out clearly in
preparations from tissues which have been fixed and stained.
The reagents -which have been found most valuable for other
histological researches are not always to be relied on for the
demonstration of karyokinetic figures. Strasburger fixed
his vegetable tissues by placing them, when quite fresh, in
absolute alcohol. Others have used the salts of chromic
acid, which are so useful for the isolation and definition of
cells. Klein3 states that he has found chromate of ammonia
especially successful. Flemming, on the other hand, believes
that all fixing reagents are more or less untrustworthy,
except chromic acid, 1 per cent, solution, or saturated solution of picric acid. Alcohol and acetic acid usually produce
alterations, but the latter is useful in observations on fresh
tissues; and Peremeschko and Flemming have obtained good
results by treating fresh objects with acetic acid and Bismarck
brown. For staining permanent preparations various dyes
may be employed ; hsematoxylin is one of the most certain,
but Hermann's aniline fluid, methyl-green, saffranin, and
various carmine dyes, such as alum-carmine, borax-carmine,
are valuable in many cases. In the study of the ova of
Echinoderms Fol and Flemming obtained good preparations
with osmic acid and carmine, but most of Flemming's* new
1
This term wasfirstused by Schleicher (' Die Knorpel-zelltheilung, Arc.
mik. Anat.,' Bd. 16) to denote the stages in the process of division whioh
precede the formation of the equatorial plate; but it is now agreed that it
shall include the whole metamorphosis from the resting state of the mothercell to the return to that state in the daughter-cells (icdpvov, nucleus; and
Klvri<nQ, movement).
3
See Mr. Priestley's resume in this Journal, April, 1876.
3
This Journal, April, 1879.
4
" Beitrage zur Kentniss der Zelle," &c>, iii Theil. ' Archiv Mik.
Anat.,' Bd. xx, 1881.
36
J. T. CUNNINGHAM.
results were gained by colouring fresh eggs on the slide
with saffranin or some aniline dye, and then adding acetic
acid, or by using the compound acetic acid carmine, after
Schneider's method. Sometimes Flemming found that the
acetic acid carmine gave a better staining when the ova
had previously been treated with nitric acid of 40 or 50 per
cent, strength, and then carefully washed with distilled
water.
Concerning the main features of the process of karyokinesis there is a striking similarity in the descriptions of the
numerous observers, although the objects of observation
differ so widely, but there is great variety of opinion as to
the details. Some of the discrepancies will probably vanish
with increase of knowledge, but the process doubtlessly
varies to some extent with the character of the cell.
Flemming's Typical Case.—According to Flemming, who
took for the chief material of his careful researches the tissues
of Salamandra, the changes which take place in the indirect
division of a cell are those represented in figs. 1—15. The
nucleus in its resting state is enclosed by a membrane which,
in optical section, shows a double contour (fig. 1). Within
the membrane is a " reticulum " or framework (Gerust) of
fibrils, a homogeneous ground substance, one or more nucleoli,
and in some cases a few smaller granules. Flemming believes
the nucleoli to be connected with the fibrils of the reticulum,
and denies that there are any independent granules; but the
majority of investigators speak of nucleoli and granules
lying free in the ground substance. In the resting nucleus
all the elements are stained by dyes—the membrane, the
nucleoli, the fibrils, and the ground substance. When the
nucleus is about to divide the membrane disappears, together with the nucleoli and all granules and thickenings of
the fibrils. The mass of fibrils loses its reticular character
through the disappearance of the nodal points, which Klein
and Flemming believe to be in great part the cause of the
granular character so often ascribed to nuclei. There are
no free ends of fibrils to be seen, but an appearance such as
would be presented by long endless fibrils bent irregularly
in all directions. This stage is called by Klein3 that of the
" convolution," which seems to be the only short equivalent
in English of the expressive German word " Kuauel." In
this and all succeeding stages of the metamorphosis only the
fibrils are affected by dyes; the ground substance remains
transparent, and round the mass of fibrils is a clear space
1
3
' Virchow's Archiv,' Bd. 77,1879.
'Atlas of Histology,' 1880.
RESEARCHES ON KARYOKINESIS AND CELL DIVISION.
37
separating it from the cell substance. Flemmiug concludes
from this that the nucleus is composed of two substances, of
which one is stained by dyes the other not, and he accordingly calls the former chromatin,the latter achromatin. He
believes that both of these substances are contained in each
element of the resting nucleus, while at the beginning of
karyokinesis all the chromatin is converted into fibrils, the
achromatin filling up the interstices between these and
forming the clear space round the fibrillar mass.
The convolution, by a change in the arrangement of the
fibrils, passes into the "wreath "form (fig. 3), the bends being
arranged, with move or less regularity, round a central space.
After this the mass of fibrils, in which no free ends have
hitherto been visible, breaks up into a number of V-shaped
loops, each with a bend and two diverging limbs. These
arrange themselves with the bends placed centrally and
the limbs directed peripherally, forming a star (mother
starj. Each of these loops, after it is formed divides itself,
according to Flemming, into two by a longitudinal splitting
of the fibril (fig. 5); but this statement is not accepted by
Klein (loc. cit.), who was unable to determine with the
highest powers whether the appearance referred to was due
to a longitudinal splitting or caused by the fibrils becoming
tubular. Flemming1 says that owing to this splitting the
loops become twice as numerous and only half as thick, and
that since the loops again become less numerous and thicker
after the formation of the daughter stars, a fusion of the
loops in pairs must occur at that stage.
Up to the phase of the mother star the karyokinetic figures
are of three dimensions, and the diagrams represent optical
sections ; but in the next stage the loops begin to be compressed towards the equatorial plane, so-called from its
relation to the nuclear spindle when this is present (fig. 6),
as in vegetable cells and segmenting ova of Echinodermata.
This movement Fleming has observed to be again reversed,
so that the figure recovers its previous form (fig. 7). He calls
the two stages of this movement " the systole and diastole
of the star," and illustrates its character by diagrams -which
are copied in figs. 34 and 35; the phenomenon does not
seem to have been noticed by other observers. Ultimately,
the loops form the characteristic''equatorial plate " (fig. 8),
in which the bends of the loops are directed away from the
equatorial plane, their limbs towards it. As the loops form
a broad ring, the space within which is empty, and as the
bends converge somewhat, they form on each side of the
11
Beitrage," ii Thei], • Archiv Mik. Aflat,,' Bd, xviii, 1380.
38
J. T. CUNNINGHAM.
equatorial plane a figure which may be compared to a
shallow basket, or half-opened daisy, with its opening
opposed to that of its fellow. These " baskets " now begin to
recede from one another, revealing often in the interval
between them delicate faint striae which represent the achromatic " nuclear spindle" so conspicuous in the dividing
nuclei of the endosperm in Phanerogamia (vide Strasburger,
' Zellbildung u. Zelltheilung,' 1880, Taf. i). When they
are separated for a certain distance the baskets open out
into stars forming the " dyaster " (fig. 10). The cell meanwhile begins to show an equatorial furrow, by the deepening
of which it is divided into two daughter cells, each containing a daughter nucleus. The daughter " star " becomes converted into a "'wreath" by the junction of the ends of the
loops to one another; the wreath passes into a " convolution," and this into a " reticulum," while a membrane appears
round the daughter nucleus, nucleoli are formed, and the
ground substance again becomes affected by dyes. This
inverse metamorphosis is shown in figs. 11—15.
From the part played by nucleoli in this series of changes
Flemming concludes that they are merely accumulations of
chromatin to form a reserve, which is drawn upon for the
formation of fibrils at the commencement of karyokinesis.
This view, as he points out, is opposed to all attempts to show
a connection between nucleoli and the ultimate branches of
nerves.
Relation of Nuclear Network to Cell-body.—The intimate
structure of the nucleated cell in its resting state is a
matter on which observers are still at variance. Klein holds
that the cell is composed, like the nucleus, of a reticulum and
an intermediate substance, or ground substance, which fills
up the meshes of the reticulum ; and that the trabeculae of the
nuclear reticulum are directly continuous with those belonging to the cell. Flemming, in his latest work, has made some
extremely interesting observations on the structure of the
resting nucleus. By the help of Seibert's homogeneous
immersion and Abbe's illuminating apparatus he has discovered a definite structure in the intermediate substance,
which had previously appeared smoothly stained or finely
granular. He found in it a much finer network of stained
fibrils in connection with the coarse, well-stained trabeculje
already known ; the fine granulation shown in the ground
substance by weaker lenses is the optical expression of the
fine network when not resolved. He thinks it probable,
though he was unable to determine the fact absolutely, that
the substance occupying the meshes of the finer network
RESEARCHES ON KARYtJKINESIS AND CELL DIVISION.
39
was unstained and consisted of achromatin; the finer network is not to be seen in living cells. Flemming studied it
in well-stained preparations from the Salamander. He also
discovered that the " nuclear membrane " was composed of
minute flat plates of chromatic substance in connection with
the fibrils of the chromatic network; these plates were
separated from each other by slight intervals, so that the
membrane seemed to be pierced with holes like a sieve, but
he was unable to decide whether the intervals between the
plates were really apertures or occupied by achromatic
substance. None of Flemming's new observations give any
support to Klein's statement that the intranuclear and
extranuclear networks are continuous one with the other.
Finer Structure of the Nuclear Network. —In a paper
which has recently appeared, Dr. W. Pfitzner (ref. 'Morph.
Jahrbuch/ vol. vii) of the Anatomical Institute at Heidelberg, states definitely what is brought forward as an
opinion by Flemming, viz.: that the chromatin and achromatin are distinct in the resting nucleus, but he makes
no mention of a finer as contrasted with a coarser lietwork. The preparations in which he determined this point
were sections of the epidermis of the larva of Salamandra
treated with a 1 per cent, solution of gold-chloride, either
examined without further treatment or after exposure to
light in a 5 per cent, solution of formic acid. In sections
thus prepared the meshes of the network were not stained.
Dr. Pfitzner also declares that the nucleoli in the resting
nucleus are never connected with the network, but lie
free in its meshes, and that there is no " nuclear membrane." The appearance which has been interpreted as due
to a membrane is caused by the contrast in optical properties between the achromatin and the surrounding cell protoplasm ; he argues that if a membrane were present it would
appear, on focussing the surface of the nucleus, as a flat
expansion, whereas in reality a network is seen in all optical
sections. These are points treated incidentally in this paper,
the object of which is to make known certain discoveries
iri the structure of the chromatic fibrils made by means of
a - ^ homogeneous immersion system by Seibert and Kraft.
Certain of these fibrils appeared to be composed of a series
of granules; and Dr. Pfitzner has come to the conclusion
that the chromatic fibril is not homogeneous in structure,
but always consists of a moniliform succession of minute
spherules of chromatin, held together by an unstained substance which is probably achromatin. He first observed
fibrils of this structure in ordinaiy preparations of the epi-
40
J. T. CUNNINGHAM.
isj glands, branchial epithelium, muscle, cartilage, &c.}
of the Salamander larva, or adult, stained with hsematoxylin
or saffranin, fixed with chromic or picric acid. The fibrils
exhibiting the phenomenon were not common in such specimens, but appeared the more commonly the better the conditions for studying the individual fibrils. It is necessary
to have division figures of large size and clearly stained, and
the fibrils must be as free as possible from one another. Dr.
Pfitzner believes that the granular structure is normal, and
that it is generally obscured by physical causes during
ordinary processes of preparation; he found that most
methods of embedding altered the structure of the fibril j
it was best preserved in sections of the epidermis, procured by
fastening pieces of the fresh skin of the larva, by means of
elder pith, in a microtome. Such sections were first treated
with 1 per cent, gold-chloride solution, and then either exposed to light in 5 per cent, formic acid solution, or stained
with hsematoxylin or saffranin, or first exposed to light in
the formic acid and then stained. Some fibrils he discovered to consist of a double row of spherules; this state
corresponds with the longitudinal splitting observed by
Flemming.
A large portion of the paper is devoted to the support of
the startling proposition that these chromatin spherules are
individual molecules in the chemical and physical sense of
the word. This idea is based on the argument that the more
highly differentiated a living substance is the higher is its
molecular weight, the larger the number of atoms the molecule
contains, and the greater its size. Proceeding on an assumption so slenderly supported, Dr. Pfitzner attempts to develop
a theory of the whole process of life and division in the cell,
but his pages are scarcely less difficult to comprehend than
the phenomena they are intended to explain.
Klein's view that the intranuclear network is continuous
with that of the cell is supported by Prof. C. Frommann, of
Jena ('Jenaische Zeitschr.,' Bd. 14, 1880), who has convinced himself that there is no membranous envelope enclosing either the nucleus or the cell itself. The contours
seen round the nucleus and the cell are due to the presence
of superficial fibrils (Grenzfaden), which run for a longer or
shorter distance along the surface, and are connected by
other fibrils with the contiguous networks.
Klein studied indirect division in the epithelial cells of the
bladder of the newt, in the lower layers of the epidermis of
the sheep, and other structures. According to his results,
the star- and wreath-form of the mother nucleus are of only
RESEARCHES ON KAR^OKINESIS AND CELL DIVISION.
41
two dimensions, not of three, as in Flemming's description;
he considers them to occur after the mass of fibrils has been
compressed into the equatorial plane. He states, too, that
the central points of the daughter nuclei may separate before
the fibrils have divided into loops, a division of the fibrils in
the equatorial plane occurring subsequently. Flemming
has observed in the cells of the testes of Salamander " cask
forms," in which the fibrils were continuous across the
equator; but he believes this to be the consequence of temporary fusion of the ends of fibrils previously separate; for
in earlier stages there were distinct loops only half as long
as the cask figure.
Nuclear Spindle.—The nuclear spindle, first described by
Butschli,1 is most conspicuous in the dividing cells of plants
and segmenting ova; it is formed of faint striae passing
between two poles, situated at equal distances from the equatorial plate; frequently at each pole there is a radiating figure
or " sun," composed of faint striae, like those of the spindle.
The spindle and suns are well shown in figs. 16—19 from the
segmenting ovum of Toxopneustes lividus. Flemming considers the spindle to consist of achromatin, and therefore to
belong to the nucleus, while Strasburger,2 with whom Klein
agrees, believes that it belongs to the cell protoplasm. It
is more probable that the suns at the poles of the spindle
are parts of the cell substance. This is proved for the ova
of Echinoderms by Flemming's figures in the third part of
his ' Beitrage.' Strasburger gives a typical figure of a
dividing nucleus with polar suns, spindle, and equatorial
plate, from the embryo sac of Viola palustris (ref. op. cit.,
Taf. ii, fig. 33).
The descriptions of other observers do not resemble
those of Flemming in giving such definite forms to the
chromatic constituents of the nucleus. Schleicher1 represents the chromatic elements in the cartilage cells
of Batrachian larvae as irregular granules and rods,
with a geneiai lcndency to lie parallel to the axis of
the spindle. These, when they begin to form the daughter
nuclei, fuse together into clumps of chromatic substance, which subsequently again break up into rods and
granules. Figs. 27, 28, and 29, which are successive
stages, illustrate this; figs. 30 and 31, from the cranial
cartilage of a toad, show the achromatic striae more
clearly.
Definite Number of the Chromatic Loops.—In three cases of
1
' Zeitschr. Wiss. Zoo).,' vol. 25, 1S75.
' Zellbildung it. Z.clllheilung,' JSSO, p. 388.
42
J. T. CUNNINGHAM.
cells from the epithelium of the mouth and branchiae of
the larva of Salamandra, Flemming, in his most recent
researches, was able to count the number of chromatic
loops present. The number in each case was twentyfour, and in other cases, where the number could not be
determined, twenty-four was the probable total. He has
also seen under Seibert's oil immersion a highly refractive
particle at the poles of the achromatic spindle, towards
which the threads of the spindle converge. This body has
the same relations as the polar corpuscle which Fol has
described in egg cells. In some preparations the chromatic
loops were seen to lie each with its bend on one of the
achromatic threads (figs. 41, 42, and 43).
Differences between Strasburger and Flemming.—In the
figures of vegetable cells given by Strasburger, rods and
granules almost universally take the place of the regular
looped threads described by Flemming. He differs, also, in
many other points from Flemming, who devotes a great
part of his latest paper to the discussion of Strasburger's
views. If Strasburger's observations are conclusive it follows that the karyokinesis of vegetable cells is a process
agreeing only in the most general features with that which
Flemming has seen in Salamandra, and that there is no
exact correspondence between the successive stages in the
two cases. The only stage where any close resemblance
exists is that of the equatorial plate, where the achromatic
spindle, with the disc of chromatic elements at its equator,
is obviously homologous with the corresponding stage
described by Flemming in Amphibia, and Fol and others in
segmenting ova. (For a complete series of the successive
changes, according to Strasburger, see figs. 85—108, Taf. 3
and 4, ' Zellbildung u. Zelltheilung,' 1880, from Lilium
martagon ; and figs. 60—69, Taf. 8, from Irispumilla.) The
resting nucleus is figured by Strasburger as consisting of
large round granules of chromatic substance irregularly distributed in a homogeneous unstained matrix. Out of these
granules is formed a structure having a distant resemblance
to a convolution which does not break up into regular loops,
and forms no mother star, either of three dimensions or of
flattened form, but by irregular changes assumes a spindle
form, which, in the embryo sac of Lilium martagon, consists
of a continuous mass of chromatic substance at the equator,
with threads of different lengths and thicknesses passing
from it towards the poles. A division of the chromatin
takes place at the equator and the threads travel towards
1
• Archiv. Mik. Anat.,' Bd. 16.
RESEARCHES ON KARYOKINESIS AND CELL DIVISION.
43
1
the poles, forming a dyaster , the strise of the achromatic
spindle at the same time becoming visible. The chromatic
threads at each pole then fuse together to form the daughter
nucleus, which ultimately becomes granular, like the resting nucleus from which the process commenced. The two
chief points in which this description of the process differs
from Flemming's are—1st. The division at the equator of
chromatic substance previously continuous; and 2nd. The
fusion of threads to form the daughter nucleus.
On the first of these points Strasburger is so satisfied that
he draws the general conclusion (op. cit., p. 331) that
whatever chromatic element lies in the equatorial plane, or
crosses it at the time of division, is divided in the position
it happens to have assumed. If there are any equatorially
placed threads they are divided longitudinally. The second
point is in direct opposition to Flemming's conclusion that
the daughter nucleus, in its return to the resting state,
passes through the same phases in reversed order as the
mother nucleus before division. Flemming has applied to
Strasburger's work a crucial test, the result of which showed
that the peculiarities in the observations of the latter were
due to imperfections in his methods of preparation and examination. Preparations of the protoplasm of the embryo sac
oiLilium croceum were sent to Flemming by Herr Soltwedel,
whose preparations were in part the material for Strasburger's work. These had been fixed with alcohol, stained
with borax-carmine and methyl-green, and mounted in
glycerine. Their appearance under the microscope corresponded exactly with Strasburger's figures. Flemming took
off the cover-glass from three of these, restained them with
alum-carmine, cleared them with oil of cloves, and mounted
them in dammar varnish. He then examined them with
Seibert's homogeneous immersion -r^-th, and Abbe's illuminating apparatus, and found that the structure of the
nuclear figures was the same as in those from Salainandra.
There was no chromatic substance continuous across the
equatorial plane, but an equatorial plate formed of two
1
This term I take from Klein in his 'Atlas of Histology,' 1SSO. Flemming usually distinguishes the same stage as that of the " Tochter-sterne."
It is not to be confused with the nuclear spindle having a polar sun at
each end, which, in the ovum of Asterias and other Eohinoderms, precedes
the formation of a directive vesicle, and which occurs again in the segmentation of the ovum. This appearance, which Auerbach called the
" karyolitic figure," corresponds to Flemming's phase showing an equatorial
plate. The earlier views on the subject of cell division were put before
readers of this Journal in the number for April, 1876, by Mr. Priestley, of
Manchester.
44
J.T.CUNNINGHAM.
collections of regular loops with their free ends turned
towards the plane; and there was no fusion of the loops
after their removal to the poles ; they formed the wreath and
convolution as in typical cases.
In the formation of endosperm in the embryo sac of
Phanerogamia, the division of the nucleus is not immediately
followed by that of the cell, but after the full number of
potential cells has been formed, cell walls arise in a peculiar
way. Each pair of nuclei is connected by the striae of the
achromatic spindle, and at the equator of this there appears
a series of thickenings, which Strasburger believes, from
their behaviour to iodine, to consist of starch or some allied
substance; out of these is formed the partition wall of
cellulose between the newly formed cells. Strasburger
names this series of thickenings the " cell plate," a term
which Klein has used to denote the body of the cell as
distinguished from its nucleus. In the dividing testicular
cells of Salamandra, in which the achromatic spindle is
very conspicuous, Flemming has seen equatorial thickenings corresponding to the cell plate of plants; but as
neither these nor the spindle were to be seen in the living
cells, he was unable to determine their function. He also
found a corresponding structure at the equator of the
achromatic spindle of the first dividing nucleus in Echinoderm ova (f Beitrage,' iii Theil) ; this was figured by Fol x
under the name " filaments connectifs.J> The appearance
seemed to Flemming to be caused by a bending and winding
of each fibril of the spindle for a short distance, and not to
be due to swellings or thickenings.
Development of Spermatozoa.—Flemming succeeded in following the nuclear changes in actual progress in living
cells from the testes of Salamandra; the fibrils when first
observed were already in the form of numerous loops,
these passed towards the poles of the nuclear space and
back towards the equator in alternate systole and diastole
before the formation of the equatorial plate. The following stages took place in accordance with his general
description, except that no longitudinal splitting was observed j of this phenomenon he was unable to obtain evidence in Triton, Batrachia, plants, and mammals. Peremeschko2 has observed the division of living cells in situ
in the larva of Triton cristatus. Epithelium cells, stellate
connective-tissue cells, white blood-corpuscles, and the
spindle-shaped cells of vasifactive tissue, showed the same
• ' Fecondation et commencement de l'henogenie/ Geneva,' 1879.
* ' Arcbiv Mik. Auat.,1 Bd. 16.
RESEARCHES ON KARYOK.INESIS AND CELL DIVISION.
45
series of changes. The resting nucleus enclosed by a
membrane was invisible, but nuclei about to divide contained granules and threads which assumed the characteristic
forms.
Division of Nuclei into more than two parts.—Several observers have described cases of the karyokinetic division
of nuclei into more than two parts. Eberth 1 studied indirect
division in tissues which were in process of regeneration
after artificial injury. He either cut with a scalpel or
destroyed with chloride of zinc portions of the epithelium
of the cornea, and of Descemet's membrane in the rabbit
and the frog, then, after some days, made chloride of gold
preparations from the injured parts. He believed that some
of the appearances he saw were due to the simultaneous
division of a nucleus into several parts. The four young
nuclei, which he figures lying close together and apparently
of the same age, may have all proceeded from a single
mother nucleus, but there is little reason to suppose that
the nucleus he describes with seven pointed processes (fig.
32) was preparing to divide into seven parts.
More detailed evidence has been brought forward by
Julius Arnold,2 whose preparations were from examples
of epithelioma, carcinoma, and sarcoma of the human
subject. He describes nuclei with three and four processes
(figs. 20 and 21) which have a distinct membrane, the
interior being filled with short rods thickened at one end.
The character of these is very abnormal. More convincing
are other figures he gives of spherical nuclei with a distinct
membrane, and containing a triradiate arrangement of
granules in double rows; from the granules pale strise pass
towards three foci or poles (figs. 25 and 26).
Dr. Louis Waldstein was kind enough, at the request of
Prof. Lankester, to show me his preparations from tumours
of the same kind as those which Arnold used. In these
triradiate figures were to be found similar to those described
by Arnold. Their appearance is shown in fig. 39. The
rays of the figure did not consist of double rows of granules,
but indications of fine fibrils proceeding towards three poles
were visible. I saw no membrane around nuclei in this
state. From the appearance of these triradiate forms it
seems probable that in the figures of Arnold, which I have
copied in figs. 20 and 21, only the chromatic part of the
nucleus is represented corresponding to the granules in figs.
25 and 26.
1
2
' Virchow's Archiv,' Bd. 67,1876.
Ibid., Bd. 78,1879.
46
J. T. CUNNINGHAM.
Dr. Waldstein has found both ordinary and. triradiate
karyokinetic figures in a tissue where they have not hitherto
been discovered, viz. in the marrow of human bone. The
marrow in question came from a man who died of leucocythsemia, and was much hypertrophied, as also were the
spleen, liver, and lymphatic glands. Dr. Waldstein intends
to publish shortly his observations on this case.
Strasburger found indications of the division of one
nucleus into three in the endosperm of Reseda odorata. In
all these cases cell multiplication is taking place very
rapidly; in animals no instance is recorded of karyokinetic
figures with more than two poles in healthy tissues, they
occur only where the rate of growth is abnormally high.
Polar Cells or Directive Corpuscles of the Ovum.—The
formation of polar cells in many ova, like the segmentation of the ovum after fertilization, has been recently
discovered to depend on a process of karyokinesis. The
germinal vesicle, which was previously believed to degenerate, was seen by Fol and Hertwig in the ovum of Asterias
glacialis to pass into the spindle form, and one end of the
spindle was traced into the polar cell.3 Since this process
is, as Hertwig has pointed out, essentially a cell division by
the indirect method, it may be homologous with the division
1
Since the above was written, new observations on the multiple division
of nuclei have been published in ' Virchow's Archiv,' Bd. 86, by W. A.
Martin. The observations were made at the Pathological-anatomical Instistute of Heidelberg University, and were confined to preparations from a
single cancer of the mammary gland, which had developed with extreme
rapidity. Two of the most striking figures given by Mr. Martin are
copied in Pigs. 45 and 46 of the Plate illustrating this review. Mr. Martin
figures the nuclear plate in the same way as Arnold, i. e. as double rows of
granules; but he also figures and describes typical convolutions between
the limbs of the nuclear plate. It is difficult to reconcile the coexistence
of nuclear plate and convolutions with the conception of karyokinesis
formed by other observers, especially that of Hemming. Mr. Martin
makes no attempt to lessen the surprise caused by his description ; he
seems to regard the convolutions as formed of the same substance as the
half spindles, which occupy some of the spaces between the rays of the
nuclear plate. This would be the first observation of achromatic fibrils in
the form of the convolution. It is to be noted that Mr. Martin's material
was hardened only by spirit. It is much to be desired that some pathologist should consider the cell division in tumours from the same point of
view as Hemming and others, who wish to discover a universal type of
karyokinesis. Mr. Martin has advanced the knowledge of multiple division in tumours a step further, and has proved that a cell may give rise to
four and even seven daughter cells simultaneously by karyokinetic chauges;
but more work upon this interesting subject will be very welcome.
2
Balfour," 'Comp. Embryology/Pt. 1. Also 'On the Phenomena accompanying the Maturation and Impregnation of the Ovum,' this Journal,
ol. xviii, 1878.
RESEARCHES ON KARYOKINESIS AND CELL DIVISION.
47
of the spermatospore to form several spermatozoa. The
difference between the two processes could be explained by
the fact that the ovum requires for its development a large
supply of food material. One of the daughter ova has been
selected to develop, and possesses all the food material,
while the others remain small and incapable of forming an
embryo. On the other hand, fertilization is more certainly
ensured by a number of small spermatozoa than by a few of
larger size, and thus the division of the mother cell of the
male element is a process of functional importance, while in
the Female it has become rudimentary.
Do Cells Divide without Karyokinesis ?—Since the process
of karyokinesis occurs in such diverse parts of both the
animal and vegetable kingdoms, there is ground for inquiring whether it is universal. Flemming doubts whether
cell multiplication by any other method has yet been
definitely proved. Klein, in a recent number of this
Journal (July, 1879), attempted to prove from the observed ratios of karyokinetic figures to resting nuclei in
preparations from the epithelium of the newt, that the
number of indirect divisions was insufficient to account for
the rapid regeneration of that epithelium. To this Flemming
replies by calculating from the same data and proving that
the ratios are sufficient. Van Beneden believed that multinuclear cells arise by direct division of the nucleus of a
uninucleate cell, but the indirect division of a nucleus has
been often observed to take place without any division of
the cell containing it. Multinuclear cells are frequently
found with all their nuclei in process of indirect division;
they are generally all in the same phase though not invariably. The division of Amoebae and amoeboid cells seems
to be unaccompanied by karyokinetic changes, but the
nuclei of these are very small and difficult to observe.
F. Schmitz1 has described a direct division in vegetable
cells without karyokinetic changes.
Flemming found karyokinetic figures in colourless cells in
the blood of a man suffering from leucocythsemia, but these
were not sufficiently common to account for the whole number
of such cells, and he thinks it doubtful whether the numerous
colourless cells of the blood in leucocythsemia are the same
as the colourless blood cells of normal blood; they are more
probably young stages of red cells derived from the spleen
and bone-marrow. On the other hand, Franz Schultze8 was
fortunate enough to observe a living specimen of Amoeba
1
S. B. Niederrhein, Ges. Naturwiss. u. Heilkun. Bonn, 1880.
a
' Aroliiv,' Mik. Anat.,' Bd. 11,18/5.
48
J. T. CUNNINGHAM.
polypodia in the process of division, and the changes which,
according to his description, took place in the nucleus, were
very different to those of karyokinesis. The nucleus, which
was large, single, and well defined, first became dumb-bellshaped, and then divided by an increased tension of the
central part. Other infusoria, which have been observed,
conform in dividing more or less closely to the karyokinetic
laws. The dividing nucleus of the flagellate Anisonema
sulcatum, figured by Biitschli,1 is not unlike an achromatic
spindle with a chromatic figure at each end. The large
nucleus of the peritrichous species Spirochona gemmipara,
according to R. Hertwig,2 is longitudinally striated during
division, though it differs widely from a typical nuclear
spindle. The shape of the nucleus of the acinetan Podophrya
quadripartita, figured by Biitschli,s is unlike anything found
in karyokinesis; but here also the cellular bud encloses a
segment of the nucleus.
Dr. Gruber, in his recent memoirs on the process of
division in monothalamous Rhizopoda (' Zeitschr. wiss.
Zool.,' Bds. 35 and 36), has discussed the relation of the
peculiar phenomena discovered by him to indirect celldivision. He shows how the rapid formation of a new
animal at the mouth of the mother, out of protoplasm and
shell-plates accumulated for the purpose beforehand, is
easily derived from a division like that of Amoeba. The
presence of a firm shell prevents the actual division of the
animal, while by the previous formation of shell-plates in the
maternal protoplasm the new individual is provided with a
protective covering at the commencement of its separate
existence. The division of the nucleus does not take place
till the new animal is already complete, and this Dr. Gruber
considers supports Strasburger's view that the division of
the cell is independent of that of the nucleus ; and it also
shows that the whole process proceeds from the activity of
the cell-protoplasm, the nucleus playing a subordinate part.
In Etiglypha alveolata the nucleus, before dividing, either
became granular or " gewundene Linien" appeared in it,
then it elongated and showed longitudinal lines. Dr.
Gruber thinks that these changes represent Flemming's
convolution and equatorial plate. If so, the resemblance
between the indirect division in Rhizopods and the cells of
Salamandra is not very close.
Free Formation of Nuclei.—Another question which pre1
'Zeitschr. Wiss. Zool./ Bd. 30,fig.18e.
2
3 ' JenaiscLe Zeitschr.,' vol. xi.
Ib., vol. x.
RESEARCHES ON KARYOKINESIS AND CELL DIVISION.
49
sents itself in connection with this subject is, whether
there is any free formation of nuclei independent of preexisting nuclei. Such a free formation would seem to
take place, according to the researches of Van Beneden,
in the endodermal cell of Dicyetnidse. F. Schmitz (loc.
cit.) was unable to find nuclei in the cells of Phycochromacese, so that these at present form an exception to the
general rule, that when a cell divides each portion includes
a portion of the original nucleus. But it is not long since
the independent origin of nuclei in the ovum of animals
and the embryo-sac of Phaneiogamia was generally accepted ;
and it is probable that future researches will enable the
questions still unsettled, with reference to the multiplication of cells in cases which now seem, exceptional, to be
more definitely decided.
VOL. XXII.
NEW SER.