Marvels of Pond- Life. 19 



In the group before us a number of elegant bells or 

 vases stand at the end of long stalks, as shown at the 

 top of the frontispiece, while round the tops of the bells, 

 the vibrations of a wreath or cilia produce little vortices 

 or whirlpools, 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 ac- 

 cording 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 them from one to two 

 hundred is necessary to bring 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 

 the instrument, that is to say, on one side of the space 

 the body would occupy if it were prolonged. By this 

 means, and by placing the lamp at an angle with the 

 mirror, that must be learnt by experiment, all the light 

 that reaches the eye has first passed through the object, 

 and is refracted by it out of the line it was taking, 

 which would have carried it entirely away. Or the 

 object may be illuminated by an apparatus called a 

 spotted lens, which is a small bulPs eye placed under 



