i86 



ORIGIN OF SEX AND OF THE SOMA 



colourless cytoplasm to which are attached two long 

 delicate flagella that protrude into the water in which 

 the organism lives : by the rhythmical lashing of the 

 flagella Chlamydomonas swims actively about, con- 

 tinually rotating on its long axis as it moves forward, 

 like a rifle bullet in flight. The protoplasm of the 

 cell is closely covered with a cellulose cell wall which 

 thins away at the front end to which the flagella are 

 attached. A red eyespot on the surface of the proto- 

 plasm, containing carotin (see p. 112), which renders 



FIG. 20. Chlamydomonas: a, diagram of swimming individual 

 (vegetative cell) ; b-d, stages of division to form four new 

 swimming individuals; c.w., cell wall; chl., chloroplast; pyr., 

 pyrenoid; c.c., central cytoplasm; n, nucleus; c.v., contractile 

 vacuoles ; St., eyespot ; fl, flagella. 



the organism sensitive to the direction of light, and 

 two very small contractile vacuoles just below the 

 insertion of the flagella, complete the equipment of 

 the cell. 



The nutrition of Chlamydomonas resembles that of 

 Protococcus (p. 73). It can live and flourish in a 

 weak solution of the proper inorganic salts (such as 

 that given on p. 123), which provide it with the neces- 

 sary elements for building up its protoplasm ; and it 

 makes sugar and starch (laid down round the pyre- 



