162 Autonomy of Cell-Organs 



the cell-plate is smaller than the daughter-nuclei, this 

 view, of course, does not teach anything, because it has 

 not been possible to remove the nuclei. But as soon as 

 the cell-plate protrudes sideways from betwen the nuclei, 

 it can be seen that it is not, by any means, a continuous 

 plate, but only a rather thin ring. This ring lies in the 

 connecting tube that separates the interior of the figure 

 from its surroundings and has probably the same signifi- 

 cance as in Spirogyra.'^^ This "cell-ring," as we must now 

 call the cell-plate, enlarges until it unites, first on one, 

 then gradually on all sides, with the peripheral protoplasm 

 of the mother-cell. 



That the plane of the cell-ring is the place where the 

 dividing wall forms, is certain, and agrees essentially with 

 the previous conception of the cell-plate. But it has not 

 yet been possible to discover whether or not the secretion 

 of cellulose in the cell-ring begins before the latter has 

 joined the wall of the mother-cell at least on one side. As 

 soon as its presence can be proven by reagents, the new 

 membrane is already joining the wall of the mother-cell, at 

 least on one side.'^^ Likewise it has not been decided, 

 whether, in the plane of the ring there is extended a mem- 

 brane which crosses the vacuole situated there and sepa- 

 rates it into two separate sap-vesicles. But this is not 

 probable. 



It is clear that, with the discovery of the cell-ring, the 

 old conception of cell-division that contradicts the auton- 

 omy of the plasmatic membrane, is weakened. For its 

 final refutation, however, further researches are neces- 

 sary, especially such as will include the wall of the 

 vacuoles in the figures of division. 



70Cf. pp. 132-134. 



^^Strasburger, E. Bot. Praktikum, p. 597. 1884, and Ueher Kern- 

 und Zelltheilung. p. 171 ff. 1888. 



