182 



STRUCTURE OF CHLAMYDOMONAS 



The movement of the Chlamydomonas -individuals is accom- 

 plished by means of two delicate thread-like outgrowths, the 

 cilia (Fig. 96, a and d), which can be detected arising close 

 together at the front end, and are usually as long, or longer 

 than, the body of the cell. They are recognisable under the 

 high power in stationary individuals, but are more readily 

 seen after adding a drop of iodine, which has the effect of killing 



FIG. 96. Individuals and vegetative reproduction of Chlamydomonas. 

 a, single individual of C. reinhardii ; d, ditto of C. angulosa ; b and 

 c, Palmella-sta.ge of C. monadina ; e, front end of a cell of C. reinhardii, 

 greatly magnified ; /, g, h, and i, stages in the vegetative propagation 

 of C. media, ch., chloroplast ; C.V., contractile vacuole ; n., nucleus; 

 p., pyrenoid ; s., eye-spot. (a-cand e after Goroschankin, d after 

 Dill, f-i after Klebs.) 



the organisms without much change, and not only brings out the 

 cilia, but also makes the nucleus more distinct. The cilia, as 

 a matter of fact, are whip-like prolongations of the cytoplasm 

 which, by their rapid backward strokes, pull the plant through 

 the water, the movement being accompanied by a rapid rotation 

 of the organism upon its axis. In returning to the front position, 

 the cilia are not stretched out, and thus do not counteract the 

 effect of the back stroke, the movements being thus comparable 



