THALLOPHYTA 



357 



(Fig. 266). When starved for a lengthened period an encysted 

 form is assumed. The chromatophores diminish in size and colour, 



Fig. 265. 

 Euglena gracilis. A. Form with green chromatophores {ch) ; n = nucleus; v== 

 vacuole and red eye-spot; g = flagellum. £ = hemi-saprophytic form with small 

 green chromatophores. C = colourless saprophytic form occurring in nutrient 

 solutions, in absence of light. D = resting cyst of the form C : r=red eye-spot. 

 E= germination of the resting cvst of the form A . by division into four daughter cells, 

 which later escape. (After Zumstein.) (A, C x 630 ; 5x650; D, E ■< 1000.) 

 (From Strasburger.) 



and storage materials appear in the contracted protoplasm, which is 

 then surrounded by a thick wall (Fig. 265, D). In this state it can 



IS 



Tic. 2 



-C5. 



Successive stages of fission of Euglena : semi-diagrammatic. 



resist conditions that are adverse. But when these are favourable 

 again the cyst germinates ; its wall becomes mucilaginous ; the 



