REPRODUCTION OF CHLAMYDOMONAS 187 



noid) from the elements of carbon dioxide and water. 

 It is in fact in its manner of feeding essentially a 

 green plant, its constant active movement notwith- 

 standing. We have every reason to beUeve that the 

 main series of green plants are derived from similar 

 motile forms. 



Reprodaction of Chlamydomonas. — (a) Vegetative 

 Division. — In this, the commonest process of repro- 

 duction, the cell comes to rest, the protoplasm with- 

 draws from the wall, the nucleus divides into two, 

 and this process is followed by the division of the 

 cytoplasm, including the chloroplast, a furrow appear- 

 ing on the surface and extending inwards till separation 

 is complete (Fig. 20, b). Sometimes the process of 

 division stops there, and each new cell produces 

 iiagella and secretes a cell wall on its surface. The 

 two daughter individuals begin to move actively, by 

 lashing their iiagella, within the cell wall of the mother, 

 which they burst and then swim out into the water, 

 leaving the empty shell of the mother cell wall behind. 

 Each grows to the size of the mother individual. We 

 see that this process is essentially the same as the 

 division of an amoeba into two new amoebae, except 

 that here the dead rigid cell wall is left behind. Under 

 favourable conditions of life division takes place once 

 every day, towards evening, and is complete in a few 

 hours. 



Very often, however, division does not stop with the 

 first bipartition, but each daughter cell divides again 

 (Fig. 20, c), so that four daughter individuals are 

 formed instead of two (Fig. 20, d). These of course 

 are correspondingly smaller, but on escape from the 

 mother wall they quickly grow to the full size. 



(6) Formation of Gametes and Conjugation. — Some- 



