DESCRIPTION OF VORTICELL^. rcl 



We shall have occasion again to notice the Pro- 

 tophytes^ and now pass to the Protozoa., of which 

 we have a good illustration in the Vorticella already 

 spoken of. In the group before us a number of 

 elegant bells or vases stand at the end of long 

 stalks, as shewn at the top of the frontispiece, 

 while round the tops of the bells, the vibrations 

 of a wreath of cilia produce little vortices or whirl- 

 pools, and hence comes the family name. This 

 current brings particles of all sorts to the mouth 

 near the rim of the bells, and the creature seems 

 not entirely destitute of power to choose or reject 

 the morsels according to its taste. Every now 

 and then the stalk of some specimen is suddenly 

 twisted into a spiral, and contracted, so as to bring 

 the bell almost to the ground. Then the stem 

 gracefully elongates again, and the cilia repeat 

 their lively game. 



The general effect can be seen very well by a 

 power of about sixty linear, but one of from one 

 to two hundred is necessary to l>ring out the 

 details, and a practised observer will use still more 

 magnification with good effect. They should be 

 examined by a moderately oblique light, or most 

 of the cilia are apt to be rendered invisible, and 

 also by dark ground illumination. This may be 

 accomplished in a well-made microscope by turning 

 the mirror quite out of the plane of the axis of- 



