68 A HALF-HOUR WITH THE 



The wheel-animalcules abound in our ponds and 

 rivers, and sometimes occur in great numbers in 

 the aquarium. The common wheel-animalcule, 

 Rotifer vulgaris, is most frequently found in lead 

 gutters and the drinking-fountains used for birds. 

 If a little of the deposit which usually accumu- 

 lates in the former is placed in a test-tube with 

 water, and exposed to the light, in a short time the 

 rotifers will be found swimming about in great 

 numbers, and may be transferred to a live-box by 

 means of a dipping-tube : if allowed to dry, they 

 can be afterwards revived by adding a little water. 

 Several of the wheel-animalcules are fixed, forming 

 on the outside of their bodies a little case or tube 

 in which they dwelh These forms are beautifully 

 seen when illuminated by the spot lens. 



