(1) At mitotic prophase unravelling of the chromosome spiral occurs without actual increase in length.(2) The opening out of the secondary split is at
mid -prophase. The actual split most probably does
not coincide with the opening out of the sister chromatids during mitosis.(3) The commencement of mitosis is the fission of
genes and this must occur during the resting stage.(4) The single structure of prophase spiral at mitosis is due to the close association of the homologous
genes, chromomeres, and chromatids. The cause of
the association is homology, most probably physicochemical in nature.(5) Unravelling of the chromosome spiral is a condition sine qua non for the building up of the matrix of each chromonema'separately.(6) Contraction operates from the undivided attachment constriction. This force acts upon the matrix,
causing it to decrease gradually in length. The
chromonema does not shorten but adjusts itself by
forming a spiral. This structure can be recognised in the prophase of the following division (persist - ance of chromosome individuality).(7) The tertiary split at metaphase was not found
in Vicia, Tulipa and Allium. Anaphase separation
is due to repulsion which operates between two homologous attachment constrictions.(8) The loci of pairing at zygotene between homologous chromosomes are at random, but always include
groups of chromomeres. Polarisation is caused by
special attraction between the ends of chromosomes
and centrosomes or nuclear Dole. It is most probably genetical in its or(9) At pachytene the homologous chromosomes twist
around each other.(10) The opening out of the secondary split is at
the end of pachytene.(11) The general rule of pairing - that association always occurs between pairs of homologues, and
repulsion always between pairs of paired homologous
constituents, - is demonstrated by several observations.(12) At the end of pachytene, attraction and contraction produce a torsion. The secondary split
introduces the repulsion and as a result of the interaction of these forces, breaks occur. The fusion
of partner chromatids produces the chiasma.(13) Chiasma frequency is not related to the size
of the bivalents.(14) The decrease in the number of chiasmata from
diplotene to metaphase is caused by two repulsions . The first is general, operating between pairs of
paired chromatids; the second is specific and acts
between two corresponding homologous attachment constrictions. If the latter is greater, the result
of interaction is movement of the chiasmata, towards
the distal end.(15) The following data supply evidence in favour
of Janssens' chiasmatype hypothesis: (a) Pairing of unequal chromosomes;
(b) Interlocking of bivalents at meiotic pro - :phase.
(ç) Twisting of sister chromatids on both
sides of chiasmata;
(d) Decrease in genetical crossing -over parallel
to a similar decrease in chiasma frequency.(16) The terminal association of bivalents depends
upon a special affinity between terminal chromomeres.
If intercalary chromomeres become terminal by trans - location, they attain this special affinity.(17) The movement of chromosomes towards the equatorial plate is a result of repulsion operating between poles and attachment constrictions only.(18) Metaphase equilibrium is a result of repulsion
between poles and attachments and between attachmen
of similar and dissimilar chromosomes.(19) In some cases the interal affinity of chromosomes will interact with the other forces and determine the mitotic or meiotic metaphase pattern, as
it is the case in secondary association and somatic
pairing.(20) The spindle mechanism is necessary for normal
chromosome movements before and after metaphase.
It guides the chromosomes by their attachment constriction towards equilibrium either at the metaphase plate or at the poles. The spindle can be
formed only in a normal cytoplasmic environment.(21) At anaphase there is a second period of equilibrium where the repulsion between the corresponding attachment constrictions and poles is equal. Further
separation is due to the expansion of the inter-chromosomal spindle, for which new evidence is put forward.(22) At anaphase there is no repulsion between the
similar or dissimilar attachments migrating towards
the same pole. Repulsion exists only between the
corresponding homologous attachment constrictions.(23) The similarity between effects of forces operating at mitotic and meiotic division and those
which act in an electro-magnetic field indicates a
close relationship in the nature of those forces
