CELL-CONTENTS OP CLOSTERIUM LUNULA. 187 



NOTE ON THE MOVEMENT OF THE CELL-CONTENTS 

 OF CLOSTEEIUM LUNULA. 



BY A. W. WILLS, F.C.S. 



It is well known that at each end of the fronds of certain 

 Desmidieae there is a clear oval or spherical space, within which are 

 seen a number of minute particles in more or less active motion, at any 

 rate during some periods of the life of the plants. This is especially 

 the case in the genus Closterium, and conspicuously so in the largest 

 species, Closterium lunula. 



In this plant there is also, as has been often observed, a certain 

 motion of the colourless granular liquid cell-contents which form a thin 

 film between the deep green endochrorne mass and the cell wall of the 

 frond. This motion has been described as a circulation, but the term 

 is incorrect. The actual, character of the movement is one of ebb and 

 flow, alternately towards and from the ends, and, in favourable 

 specimens, careful examination under a J or a objective and B eye-piece, 

 shows that it takes place in delicate longitudinal lines or bands, and 

 that in different hues the flow may be actually in opposite directions at the 

 same time, while in any one line the direction of flow is usually reversed 

 every few seconds, a moment of rest or of confused movement of the 

 particles among one another preceding the reversal of the direction. 



The cause of this peculiar ebb and flow is simple enough, but I am 

 not aware that it has been previously recorded. 



The clear spaces at the ends of the fronds of Closterium lunula are 

 really contractile vesicles, and careful observation under the powers 

 indicated above shows that they are undergoing incessant though slight 

 change of form. 



The contraction of any part of the surface of the vesicle is followed 

 by an immediate rush of the surrounding fluid to fill the vacuum thus 

 formed, and the direction of the currents, where the transparent spaces 

 allow them to be observed, may be clearly connected with the corres- 

 ponding contraction of one or other part of the vesicle. I have spoken 

 of their flow being in lines or bands. The expression is merely intended 

 to describe the general appearance of the action. The whole space 

 between the endochrorne and the cell wall is, doubtless, filled with the 

 fluid ; but the transverse section of the former would probably present 

 a fluted or corrugated form, corresponding to its longitudinal disposition 

 in belts of denser matter ; and the flow of the surrounding fluid 

 may probably be determined by the channels formed by this fluted 

 structure. 



The movements I have described may probably be found to have 

 their parallel in the smaller species of Closterium, and in other genera 



