CHLAMYDOMONAS 53 



plasm, within which a single nucleus resides. The 

 chloroplast is thicker at the posterior end — the bottom 

 of the cup — where it encloses a spherical pyrenoid. The 

 fore-part of the cell is colourless, being occupied by clear 

 protoplasm, in which one or two vacuoles may be seen 

 appearing and disappearing. A red or brownish pig- 

 ment, or " eye " spot, is also visible at one side of the 

 body towards the front. This tiny one-cell plant 

 swims in a jerky fashion, rotating on 

 its long axis as it proceeds, its direc- 

 tion being towards a light of moder- 

 ate intensity; and it is suggested 

 that the pigment spot has something 

 to do with the plant's sensitiveness 

 to light. But how is it enabled to 

 swim ? If we watch a cell that has 

 come to rest, we may be able to see 

 that a pair of flagella issue from the P^ 

 colourless protoplasm to the fore. ^o^ATAJna^Tsl 

 These exceedingly fine lashes are HighlyMagnifibb. 

 more easily obsen^ed when the cell /^rf^ruSl; o.. 



is stained, say, by iodine. It is chloroplast; A;,nueleus; 



by lashing the water with its two «. eye-spot; py, py- 

 flagella that Chlamydomonas swims. 

 Animal-like as this organism is in its movements, it 

 is certainly a plant. It has no mouth; it cannot ingest 

 solid food; it must feed upon the products of carbon 

 assimilation and salts in solution, all its requirements 

 reaching it in solution through its permeable wall of 



cellulose. 



Even in so small a plant as ChUmydomoms, both 

 asexual and sexual modes of reproduction are apparent. 



