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CONTRIBUTION TO THE THEORY OF THE MOVE- 
MENTS OF DIATOMS. 
W. M. Kozrowsxi. 
THERE are, as is known, two principal hypotheses to explain 
the enigmatical movements of the cells of Diatomacee. The 
one advanced by Ch. Nageli seeks their cause in the osmotic 
currents between the cell and the surrounding water; the other, 
framed by Max Schulze, supposes that these movements are 
simply the creeping of the diatoms upon the surface of the 
object- or cover-glasses, performed by means of a protoplasmic 
pseudopodium issuing through a slit of the cell membrane. 
The view of Pfitzer, according to which the cell membrane of 
these algz is composed of two distinct halves, one of them 
being adjusted to the other as a cover upon a box, seemed to give 
support to Schulze’s explanation, and some observers have held 
that the movement can only take place when the cell is in con- 
tact with the glass and in a definite position with relation to it, 
and that, if that position be changed by shaking the glass with 
a needle, the movement will cease. Pfitzer himself believes 
that what is called the rhaphe of many Diatomacez is nothing 
but a slit through which the protoplasmic pseudopodium pro- 
trudes. No one has yet been so fortunate as to see the proto- 
plasm passing out through this slit. 
To these two old antagonistic hypotheses, each of which has 
found many apologists and opponents, Otto Miiller recently 
added a new one.'. After having studied the structure of the 
cell by means of thin sections,? he comes to the conclusion that 
the rhaphe is instrumental in transferring protoplasmic currents 
to the outside of the cell, and acts asa “propeller,” by giving 
to these currents a screw like direction. 
*Die Ortsbewegungen der Bacillariaceen. Berichte d. Deutsch. Bot. Gesell. 14: 1896. 
* Die Durchbrechungen der Zellwiinde, etc., ibid., 7.177. 1889. 
1897] 39 
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