HARDWICKE'S SCIENCE-GOSSIP. 



175 



2. With regard to the movements which result in | becomes globular. This is effected by the disc being 

 opening and closing of the bell, we have a very | drawn inwards {i.e. towards the centre of the cell) by 



Fig. in. — Vorticella nebulifizra. aa, expanded; b and c, contracting ; d, stained with methyl violet and more highly magni- 

 fied; c, cilia of disc; d, cilia of peristome; d, disc; cs, contractile space; ect t ectosare; end, endosarc;./^, food vacuole; 

 g, large granules ; m , muf cle of stalk ; «, nucleus ; oe, cesophagus : p, peristome ; s, sheath of stalk ; s£, stalk ; a, b, and c, 

 i inch ; d, i inch. 



Fig. 122. — Vorticella nebulifcra. a, stages in division ; b, free-swimming species ; b, basal cilia ; c, formation of basal cilia ; 



d t encysted species surrounded by bacteria, etc. 



complex mechanism. If you watch you will notice I the contraction of the protoplasm below it. At the 

 that when the stalk shortens, the bell closes and | same time the peristome closes over it and the cilia 



