34 GENERAL BIOLOGY. 



II. Structure. 



1. The thin transparent external layer, the 



cuticle. 



2. The finely granular layer next to the cuticle, 



the ectoplasm. 



3. The central portion, the entoplasm. 



4. Food-vacuoles. 



5. Water- vacuoles. 



6. The contractile vacuole : generally situated near 



the disk. 



7. The nucleus : a long slender curved body 



(not always visible in the living specimen). 



8. The stalk: by which the bell is attached, 



consisting of : 



(a) An outer transparent sheath continuous 



with the cuticle of the bell. 



(b) The contractile axial filament, the pro- 



longation of the ectoplasm of the bell. 

 Make a diagrammatic sketch much enlarged. 



III. Movements. 



1. Of the cilia. 



Note the way in which the cilia move, the 

 currents produced in the water (to see 

 this draw a few particles of finely pow- 

 dered carmine under the cover-glass), the 

 whirling of the carmine particles down 

 the oesophagus. 



2. Of the entoplasm : made evident by the 



carrying around of food-vacuoles, etc. 



