CHARA— STRUCTURE OF CELL 329 



an arrangement — I mean the state of things in the Charm. 

 As is well known, there exist in the protoplasm lining the wall 

 of the elongated thread-like cells of these algse two so-called 

 interference streaks, which pass along the longitudinal sides 

 of the cells opposite to one another, and in which the 

 chlorophyll-free protoplasm is in a resting state. Since the 

 neighbouring protoplasm is in energetic streaming movement, 

 it must be assumed that the protoplasm of these streaks is 

 of a firm consistence. Now if, as seems quite possible, a 

 rigid bridge was stretched from the ends of these interference 

 streaks to the surfaces at the extremities of these cells (see 

 Fig. 22), then the conditions would be to some extent 

 realised which we postulated for the origin of the rotational 

 current. Whether a similar state of things can be made 

 probable in other cells also with rotational currents, remains 

 of course an open question. Nevertheless one further difficulty 

 may be considered here, which we meet with in the explana- 

 tion attempted for the rotational current of the Charce. It is 

 to be expected that under the suppositions we have made 

 the current might go on unaltered even after plasmolytic 

 separation of the protoplasm from the cell wall. It is, 

 however, well known that a long Ghara cell can be con- 

 stricted by ligatures in several places, and that when this 

 is done, after a temporary pause a regular rotational current, 

 corresponding to the original one, appears in each of the 

 constricted portions. As has been said, this phenomenon 

 presents new difficulties. Of course the two interference 

 streaks also become constricted by the ligatures, and thus 

 at the ends of the constricted pieces of the cell the required 

 bridges are to a certain extent furnished by these streaks. 

 Since, however, these firm bridges, as is easily intelligible, 

 need not penetrate the whole lining of protoplasm, but 

 ought to be present only at its inner surface, in order to bring 

 about a rotational current in the required manner, the 

 previous conditions could not be simply renewed by bending 

 together of the interference streaks, if at least, as is 

 probable, these streaks traverse the whole lining of proto- 

 plasm. Now whether we may picture to ourselves interrup- 

 tions of the interference streaks as already present from the 



