Ch. X] 



MICROSCOPIC ANIMALS AND PLANTS 



335 



Fig. 201. 



O 

 Tripod Magnifier. 



lect the bits to put on the slide for examination. Do not use distilled 

 water for these organisms, but water from the source of supply. 

 (For food see § 521). 



§ 521. Infusoria and bacteria; In- 

 fusions. — One of the best ways to 

 get a large variety of living forms, ani- 

 mal and vegetable, is to make such a 

 gathering as described above and to 

 put it into a small fruit jar or other 

 wide open vessel, and to put with it 

 some of the stems of the grass along 

 the stream. If in a moderately warm 

 place for a day or more this collection 



will be found swarming with living things. Soon, however, the 



numbers will lessen and finally there 

 will be very few left. These living 

 things need food. One of the good 

 foods for them is the soup made from 

 boiling up some of the grass and hay 

 found near the natural habitat. Any 

 good hay may be used, however. When 

 the soup is cool add some of it to the 

 vessel containing the organisms, or 

 what is better take another dish, add 

 the soup and a fair amount of the 

 liquid from the first gathering. Usu- 

 ally this new supply will be as rich in 

 life as was the original gathering. (See 

 under Neutral Red (§ 582) for experi- 

 ment in staining live forms.) 



§ 522. Diatoms. — These are plants 

 with silicious shells, and are found in 

 natural waters both salt and fresh. If 

 one goes to a pond or stream in May 



Fig. 202. Magnifier Sup- 

 ported by a Focusing, Jointed 

 Holder. 



Base The heavy iron base to 

 keep the apparatus steady. 



R P Rack and pinion for 

 focusing the magnifier. 



/ / Joints to make it possible 

 to put the lens in any desired 

 position. 



or June or July especially, the diatoms 



are very abundant. They may be found at any time, but in the 



spring most abundantly, as with most living things. The brownish 



