110 PLANT-ANIMALS [CH. 



be found, but a larger or smaller, colourless body may 

 be seen lying in a central vacuole in such a situation 

 as to suggest that it has been taken up through the 

 mouth. The larger body consists of two closely 

 apposed cells, the smaller of a single cell. In 

 either case, the colourless body is surrounded by a 

 mucilaginous wall which swells considerably as its 

 contents divide, in the case of the single cell into 

 four, in that of the large cell, into eight daughter 

 cells. The colourless cells, each from 15 to 16 p in 

 length (= about y^ inch), are discharged by the 

 bursting of the vacuole and take up positions similar 

 to those in which the four green cells are found. 

 Though colourless and of granular content, a large, 

 oily looking pyrenoid may be made out in each cell (cf. 

 Fig. 22, B, Pyr.j p. 125), and by appropriate methods 

 of staining, the presence of a nucleus may be demon- 

 strated. The colourless cells increase in size and, in 

 each, a red eye-spot makes its appearance as a little, 

 lateral patch near the margin. Soon a distinction is 

 to be seen between a colourless plug of protoplasm 

 and a cup-shaped, granular mass which occupies the 

 major part of the cell (Fig. 22 O). A faint yellow 

 colour steals over the cup-shaped, granular mass, the 

 yellow colour deepens and, becoming green, enables 

 us to identify the cup-shaped, granular mass as a 

 chloroplast. The cell, now a green cell, has no cell- 

 wall, and differs only from a green cell of an adult 



