654 Balls .— The Mechanism of Nuclear Division. 
The large amount of ‘ achromatin ’ in the nuclei of the cotton-plant 
has enabled me to study there some processes which are not readily seen 
elsewhere. The interpretations which I have placed upon these observations 
appear to correlate several parts of the problem of the achromatic structures, 
but the work needs to be tested by other observers. 
If the results about to be described are confirmed, it will probably be 
found that the principle of the matter holds good for the whole organic 
world. 
Historical Summary. 1 
Btitschli, Van Beneden, and Strasburger (in his early researches) be¬ 
lieved that the whole mitotic figure was formed from nuclear substance. 
Fol also considered that the spindle was derived from the nucleus, but 
regarded the asters as of cytoplasmic origin. 
Strasburger changed his opinion at a later period and formulated the 
conceptions of £ kinoplasm * and ‘ trophoplasm ’. Both of these were cyto¬ 
plasm in origin ; the former being seen as threads which invade the nucleus 
when the nuclear wall disappears, and acting as the motor mechanism in 
cell-division. 
The Spindle Fibres . 
The mode of origin of the spindle fibres has been explained in almost 
every conceivable way by those who hold them to be tangible structures. 
Further confusion is introduced by those who do not see their way to 
accepting them as real, but regard them as manifestations of some physical 
stress in the protoplasm. 
The popular comparison of the spindle to a field of force between two 
opposite magnetic poles is only persuasive when the observed organism 
develops centrosomes and asters. We can conceive of the centrosome as 
a storm-centre of metabolism which radiates lines of metabolic disturbance, 
although the centrosome is a very minute organ ; but when the astral rays 
are missing, and the single centre has broken up into a score, or more, must 
we not then assume that the single line from the inner side of each of these 
is the sole manifestation of this intense metabolic change ? There seems to 
be no reason why this change should be confined to one side of a granule 
which is smaller than the wave length of sodium light. 
Even if vve grant the existence of these lines of metabolic stress, we 
still lack an explanation of the way in which the chromosome is moved. 
Strasburger’s suggestion that the chromosomes are chemotactically 
sensible seems rather unlikely. The chromosomes would have to be self- 
motile. Now, the chromosome is so closely concerned with the trans¬ 
mission of heritable characters—a function of fundamental importance—that 
1 For references see E. B. Wilson, The Cell in Development and Inheritance. 
