Thus far I have passed over. a further curious phenomenon, which
will have impressed the reader in the cited figure3: the threads [chromosomes] divide themselves in ha.If longitudinally. This can happen already
at the end of the cluster stage or during the course of the third phase
described now. Thus, one sometimes encounters single threads, sometimes
double ones, in all these conditions. The threads can even still remain
single.during the state of transformation·of the star [arrangement]. That,
however, their longitudinal splitting is a typical occurrence is beyond
all doubt for Salamandra, on account of the large number of such figures .
.The halves of the threads lie almost precisely parallel in epithelial
nuclei anclred blood cell nuclei; in endothelial cells and· often in connective tissue cells they lie slightly diverging: Their ends are completely free,
o~casionallyvery slig·htly thickened, and often both thread ends of a pafr
are curved around in the same direction.
Later the threads push apart from each other along their.. whole
length and thus a fine-rayecl star arises with twice as many and half· .as
thick rays as before. That this longitudinal division of the threads (at
least in Salamandra) is a fundamental and constantly occurring stage is
simply shown in as much as also in the following stage (equatorial plate)
the thi~eacls are always only about half as thick as in the single-rayed star.
Until now, 110 investigator of nuclear division has reported anything.
about such a division of the threads; therefore,, '1 first asked myself if the
action of the reagents could perhaps be involved, inconceivable as this
must seem to the person who repeatedly finds the same appearance in
picric and chromic acid preparations. I cari dispel every snch thought
since l succeeded in several cases also to see the clmible. threads in living
form. Success in this occurs only in very flatly spread-out cells, which lie
drawn over younger more deeply positioned Leydig mucous cells or nn.der
which a. vacuole had fonneclin a cell .of the deep layer, as vacuoles .often
come and again disappear during .observat.ion without affecting the·
course of cell division.
It is possible that the separation of .the two nuclear halves can have
taken place earlier than in the equatorial plate stage. In this case one
would pointto 011.e phenornencm above all: the longituclinal splitting of
the threads. ·what; afte1' all, does this mean? When I discovered them I
first thought that they perhaps could represent a homoJogy, although
very modified form, of the division fo. two which the elements oE the
"nuclear-plate" undergo in the cells in question, according to results of
Strasburger, Bi.itschli and 0. Hertwig. That is, that one longitudinal half
of each thread could move into one half of the nuclear figure, the other
longitudinal half of thread into the other half of. the nuclear figure, in
other words, each into a future daughter nucleus. if we asume that one
in
..
Walter Flemming (1879) Contributions to the knowledge of the cell and its life appearance .
. From~.f1J:kivfiir Mikroskpsiche Anatomie, 16: 302-406.
longitudinal half of the double ... [chromosome] ... is predestined for
the one young nucleus, the other thread for the other nucleus, and that
this will occur similarly for all threads, and, if we also assume-which to
be sure is unproved-that before the beginqing of phase 1 all the central
loops have separated so that every double thread has come apart into
four quarters, then no further division is required. The four quarters
Fig. I. Sclcct.cd stages of mitosis in the salamander.
lvfikroskopischc Anatomic, volume 16.
WAI.1'ER FLEMMING,
1879. Archiv fur
Walter Flemming (1879) Contributions to the knowledge of the cell and its life appearance.
From Arkiv fiir N!ikro!_kpsiche Anat~n:_ie, 16:__~02-406.
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need only· shHt in: such a .. way th<tt two ofeach arrive•in each nucl~ar 11alf
ancl this could happen in the equatorial plate phase. Each thread element
whiCh reaches from the pole side of the nuclear figure to the equatoi:ial
plane could· con~espond to Sllch q:, quarter ray.
· ·
This would presiune. that the connectioris of threads on both sides of
the.equator-which one observed at this stage-must be only secondary
contacts or temporary fosions of the thread ends and ai:e of no spedal
significance: .
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... · ·
l have. presented. this hypothesis here becaµse the loBgitudinal
splitting of the threads seems to me tqo noteworfu.y no~ to. try to. prov1de,
. some thought concemingit. for the moment LtJ1row out ·thiS purety asa,
possibility w'ithout.in any ·way insiSt:lng, l.lpqrdt.
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Walter Flemming (1879) Contributions to the knowledge of the cell and its life appearance.
Rro~_Arkiv fil!_}.!ikf'oskpsiche Anatomie, 16: 302-406.