LOCALITIES. 13 



In all parts of the world, and in most waters 

 where aquatic plants in a healthy state abound, 

 these invisible creatures may be met with, and 

 not only in stagnant pools, but in running 

 streams, and the broad ocean. Among water- 

 plants these .little beings find shelter and food ; 

 therefore, when water is brought from these 

 localities, some of the vegetation peculiar to the 

 pool, or stream, should be procured at the same 

 time. They swarm amongst duckweed (Lemnd] . 

 Many are found also in clear shallow pools, par- 

 ticularly in the spring. When a pond is ob- 

 served to have a stratum of dust on the sur- 

 face, or a thin film, it wih 1 generally be found 

 almost entirely composed of living creatures. 

 This dust-like appearance consists nearly exclu- 



c 



