THE PROBLEM OP MITOSIS. 
575 
growth. He believed that the objection of crossed rays is 
removed by Hartog’s distinction of material chains and 
theoretical lines of force, and said that not only had tripolar 
figures been produced magnetically, but that his theory is 
consistent with their occurrence in mitosis. He allowed, 
however, that chai-ges of opposite signs must be assumed for 
the centrosomes of spindles that can-y no chromosomes. 
Two years later Baltzer published the results of his investi- 
gations upon multipolar mitoses in Echinoderm ova. He 
pointed out that, if centrosomes carry charges of unlike 
signs, Hartog’s explanation of chromosome divergence fails; 
for each daughter-rod must be inducted by the near pole 
more strongly than by the farther, and the presence of 
unlike charges in sister rods will consequently cause attrac- 
tion and not repulsion. Moreover, he repeated that the 
assumption of unlike poles cannot be reconciled with the 
occurrence of either typical triasters or tetrasters that have 
diagonal spindles. He remarked that Gallardo’s qualifica- 
tion in the case of chroinosomeless spindles involves opposite 
explanations for apparently similar data, and is incompatible 
with the occurrence of mitotic triasters in which two spindles 
containing chromosomes are united to one that contains none. 
Furthermore, he showed an eai-ly stage of an Echinoderm 
triaster in which three distinct spindles are formed while the 
chromosomes are still lying in the centre of the figure: and 
affirmed that the early stage of every mito.sis is represented 
by a chromosomeless spindle; for the last named is stretched 
between 'the two poles for some time before the chromosomes 
take up their positions upon it. In criticising the conclusions 
of Keinke he pointed out that in Echinoderm mitosis the 
chromosomes can be equally distributed to the two poles 
wlien these are obviously unequal, and suggested that 
abnormal distribution is due to insufficient plane surface 
offered by the smaller aster. He i-emarked, in conclusion, 
that Rhumbler’s explanation seems to be the most probable, 
and accords with multipolar mitoses and the occurrence of 
asters of various sizes. 
