179 
in Dictyota dichotoma. 
this nor any other doctrine hitherto proposed is without 
objection. Any theory dealing with what we call a centro- 
some, wherever that may be found, must deal also with the 
kinoplasmic radiations and spindle-fibres associated with it, 
and any theory assuming the morphological unity of the 
centrosome similar to that of the nucleus, without at the same 
time taking into account the kinoplasmic fibres of the karyo- 
kinetic figure in higher plants, is inadequate. 
The Formation of the Cell-Plate. 
Within the last few years our knowledge of cell-formation 
has been greatly extended, and in some respects revolu¬ 
tionized, especially as regards the so-called processes of free 
cell-formation. The method by which the cell-plate or 
plasma-membranes are laid down in higher plants no longer 
finds such universal application as was formerly attributed 
to it. 
The investigation of Strasburger (’97) and Swingle (’97) on 
the Phaeophyceae, and those of Harper (’97, ’99) on the 
Ascomycetes and Phycomycetes, have opened up a new field 
of research. 
The type of cell-plate formation in the Brown Algae differs 
from those described by Harper in the Fungi as well as from 
that in the higher plants. It seems possible, however, that 
in all of these apparently diverse types the plasma-membranes 
are laid down through the agency of the kinoplasm, although 
this may not be demonstrable as sharply differentiated radia¬ 
tions or as connecting fibres. 
In Fncus , according to Strasburger (’97, p. 358 ), when the 
eight nuclei are distributed in the cytoplasm of the oogonium 
and the formation of the cell-plate begins, the centrosomes 
are no longer to be recognized and the kinoplasm cannot 
be distinguished from trophoplasm. The cell-plate arises 
in the trophoplasm, whose alveolar walls so arrange them¬ 
selves as to form a continuous plasma-membrane. 
c Die Verbindungsfaden zwischen den Tochterkernen werden 
O 
