348 OHIO BIOLOGICAL SURVEY 



The vegetative reproduction consists of either a longitudinal 

 division of the normal individual or the division of the individual 

 after having undergone an encystment stage. In the latter case 

 the cyst often divides a number of times, forming many small 

 cysts more or less closely connected. The small individual escap- 

 ing from the cyst may grow into a mature form or undergo the 

 complicated process of a sexual cycle by the copulation of the 

 individuals. 



The form of the spores, particularly among the Euglena, is 

 of considerable systematic importance. 



4. Economic Importance. 



(a) GENERAL RELATIONS TO WATER SUPPLIES. 



The practical importance of the Euglenoidina in their rela- 

 tion to man is based upon several considerations. They constitute 

 one of the principal groups of the unicellular organisms which 

 possess chlorophyl and are able to absorb the various inorganic 

 salts as well as the oxygen and carbon dioxide contained in the 

 water and thus produce starch-like substances. These substances 

 in turn through the intermediate Crustacea, etc., form the basis of 

 the food supply of the fishes and other animal organisms living 

 in an aquatic environment. Economic phases of this nature, 

 which pertain to the fishing industry as well as to water fowl. 

 etc., particularly of the region of the Great Lakes, will be more 

 appreciated as time brings about a diminishing supply of such 

 animal organisms and threatens the commercial importance of 

 the industries dependent thereon. 



Water from both public and private supplies often has un- 

 pleasant tastes or odors and in the majority of cases the result is 

 due to the presence of organisms of microscopic size which reach 

 their maximum development, so far as numbers are concerned, in 

 reservoirs, ponds, and lakes. Inasmuch as such conditions are 

 usually due to the substances — oil globules, etc. — set free when 

 the minute forms of life are in a state of disintegration, the filtra- 

 tion of the water, particularly mechanical filtration, does not nec- 

 essarily remove the unpleasant taste, although the proper kind of 

 filtration accompanied by aeration usually proves successful. 

 When ground waters from infiltration galleries — deep wells in 



