in the Pollen- Mother- Cells of Larix . 305 
in the division of the central archegonial cell of Cycas by 
Ikeno (’96, ’98), of Finns by Blackman (’98), and of Zamia by 
Webber (’01) ; in the segmentation of the eggs of Cycas and 
Ginkgo by Ikeno (’98, ’01), and of those of Cephalotaxus by 
Arnold! (’00) ; and in the cells of wounded potato tubers 
by Nemec (’99 c). In the division of the generative nucleus 
of Potamogeton , Wiegand (’99) finds that one pole, attached 
to the cell-wall, is very broad, the other sharp. In the Larch 
we have seen that the fibres converge to a limited polar 
region, but not to a definite point. 
Evidently, if, by their contraction, the spindle-fibres are 
to pull apart the daughter-chromosomes, they must have some 
attachment or anchorage for their polar ends. This purpose 
we may imagine to be well served by a special body to which 
they all converge, provided that body have itself some means 
of attachment ; but the instances just cited show that the 
cells of many organisms, including those of higher plants, 
have secured means of insertion for their spindle-fibres in the 
absence of such a definite body, and often without even a 
marked convergence toward a polar region. Strasburger (’00) 
shows that in some cases a point of attachment is found in the 
plasma-membrane ; but in many others, the fibres seem to 
end in the cytoplasm, whose substance in this region we must 
suppose is adapted to furnish an anchorage for the contracting 
fibres. 
It would seem, then, that the cells of the higher plants have 
either found other organs to replace the centrosome, or that 
they have found means to dispense with its functions entirely 
and to arrive at substantially the same results by quite different 
methods. I shall not attempt to criticize the centrosome 
theory except as applied to the higher plants ; but it is evident 
that the whole centrosome question for the animal cell is at 
present an open one ; and such problems as the persistence 
of this organ through succeeding cell generations and its 
significance in nuclear division are still far from settled 
(Conklin, ’98 ; Gardiner, ’98 ; Mead, ’98 a). 
As to the energy manifested by the kinoplasmic fibres, it 
