MORE ABOUT WHEEL ANIMALCULES 169 



filaments, each of which shows a fine streaming current 

 in its substance, and is, in fact, a naked filament of living 

 protoplasm like one of the ray-like filaments of the sun- 

 animalcules. 



The most curious of the tube-building Rotifers are those 

 which form their tubes of little, equal-sized pellets of solid 



Fig. 37 {its). — Three tube-building wheel animalcules. j4, Floscularia 

 campanulata. B, Stephanoceros Eichhornii. C, Melicerta ringens. 



matter — as it were, " bricks " — which they first form by com- 

 pacting fine particles in a special pit on the head and then 

 build them up and cement them together in rows to form the 

 tube, adding row after row as the animal itself increases in 

 length (Fig. 37 (dis), C). These are known as Melicerta ; 

 and, though some kinds use any minute particles to make 

 their bricks, one kind is frequent which uses its own 



