THE BUILDING ROTIFER 177 



men, however, tell us that the illusion is due to 



the cilia lashing the water with regularity in one 

 direction. 



Fig. 50. Building Rotifer (Melicerta ringens). ^th of an inch in length. 



This rapid motion performs a wonderful duty for 

 rotifer. Together with the creature's swallowing 

 power, it produces a tiny vortex or whirlpool, so that 

 particles of food and building material are brought 



M 



