SP1ROGTRA. 49 



(a) Thin colorless layer lining the cell-wall, 



primordial utricle. 

 To see the primordial utricle better, treat with 5 



per cent, or 10 per cent, salt solution. Watch 



carefully and observe : 

 The contraction of the primordial utricle away 



from the cell-wall (Plasmolysis). Sketch. 

 With afresh specimen observe : 



(b) One or more green bands, generally 



with jagged edges, imbedded in the 

 primordial utricle : the chromato- 

 phore. 



Changing the focus slowly, follow the band from 

 one end of the cell to the other. 



What is its length compared with that 

 of the cell ? How is it arranged ? 



(c) Biconvex disk-shaped bodies in the 



chromatophore : pyrenoids. 



(d) Near the centre of the cell a small mass 



of protoplasm suspended by fine 

 threads that connect it with the pro- 

 toplasm lining the cell-wall ; in its 

 centre is the nucleus, with a large 

 nucleolus (not always visible in the 

 unstained specimen). 



3. Enclosed by the primordial utricle and oc- 

 cupying most of the cell-cavity : a large 

 vacuole. 



