EDMONDSON — PROTOZOA OF IOWA. 3 



has been done. In some instances individuals of the .same species 

 have been found in widely separated regions while the species was 

 not found in intermediate localities. This, however, is not con- 

 clusive evidence that the species did not exist in the intervening 

 territory. 



Judging from collections of material in various counties, so gen- 

 eral seems to be the distribution of Protozoa that it is quite prob- 

 able that a permanent body of water such as a small lake would, 

 during the different seasons of the year, furnish most of the species 

 that might be obtained from the waters of the entire state. 



Although perhaps the most successful group of animals because 

 of their minute size, the nature of their habitat, their power of 

 encystment, rapidity of reproduction and manner of distribution, 

 all forms of fresh water Protozoa do not indiscriminately find a 

 habitat in similar environments. After considerable experience 

 in collecting them one learns to know, with at least some degree 

 of accuracy, the conditions under which .species exist. Such 

 knowledge is of some value when certain forms are desired for 

 biological studies. Holotrichous and hypotrichous ciliates are 

 commonly found in stagnant and bacteria-laden water, while the 

 Ma.stigophora and shell bearing Rhizopods preferring a purer hab- 

 itat are commonly found among algae and other plants of low rank. 

 Stalked peritrichous forms may be found in fresh water in run- 

 ning streams or quiet pools, usually attached to stones, sticks, 

 leaves, etc. Vorticella, however, is commonly observed in stag- 

 nant pond water. For the most part, suctorians have been found 

 among aquatic plants in fresh water. 



Some species are bottom swimmers while others are found at the 

 surface ; some seek the shaded places while others are attracted b}- 

 the light. It should be noted that these are only general habitats 

 and a species may be found in very diverse environments when 

 conditions are correct for its existence. 



In making permanent preparations of Protozoa various methods 

 may be employed. Shelled Rhizopods and forms possessing well- 

 defined loricae may be readily and permanently preserved by allow- 

 ing, them to dry on the slide, then mounting in balsam. Glycerine 

 preparations of many forms of Protozoa may also easily be made 

 by draining off as much water as po.ssible after the organisms are 

 fixed, then applying glycerine, but it is often necessary to nullify 



