infus6ria. 143 



always sought by the -microscopist when searching for 

 certain other forms of microscopic life, worms for in- 

 stance, or Hydra, but they are commonly disappoint- 

 ing when Infusoria are the objects sought. 



An old and water-soaked log, or a partly submerged 

 and decaying plank, are hailed by the microscopist 

 with delight, since they always prove to be treasures 

 when Infusoria are not desired. When they are 

 wanted the old log and the rotting plank are of but 

 little value. It is then usually a waste of time to 

 scrape their surfaces. If you want aquatic worms 

 these are the places to find them. If you want cer- 

 tain Polyzoa (Chap. IX.), these are the best of good 

 places to find them; but for Infusoria go elsewhere. 



A shallow pool whose bottom is covered with' last 

 year's dead leaves is commonly well supplied with 

 free-swimming animals, and some of the bottom should 

 be scooped up in the tin dipper and taken home to the 

 aquarium. Any pond whose surface bears much 

 Lemna is also the haunt of many of the free-swimming 

 Infusor.ia. 



The most prolific places are those little ponds fed 

 by slow springs at the bottom, or filled by freshets 

 from a creek or other stream and for the rest of the 

 year land-locked, shaded by trees and bushes, pro- 

 tected from too rapid evaporation, by a coating of 

 Lemna fronds, and filled with Nuphar (candock), and 

 Ceratophyllum, and perhaps with Myriophyllum, although 

 that is not very common in such places. The shade 

 should not be too dense, nor the sunshine on the sur- 

 face too bright; the proper conditions can be learned 

 only by experience and by experiment. In such a 

 pond the free-swimming Infusoria will abound, or its 



