ECOLOGY 19 



ates, such as Frontonia, Lacrymaria, Oxytricha, Stylonychia, 

 Vorticella, etc., inhabit such waters. Mesosaprobic protozoans 

 live in waters in which active oxidation and decomposition of 

 organic matter are taking place. The majority of freshwater pro- 

 tozoans belong to this group : namely, numerous Phytomastigina, 

 Hehozoa, Zoomastigina, and all orders of Cihata. Finally poly- 

 saprobic forms are capable of living in waters which, because of 

 dominance of reduction and cleavage processes of organic matter, 

 contain at most a very small amount of oxygen and are rich in 

 carbonic acid gas and nitrogenous decomposition products. The 

 black bottom shme contains usually an abundance of ferrous sul- 

 phide and other sulphurous substances. Lauterborn (1901) called 

 this sapropelic. Examples of polysaprobic protozoans are Pelo- 

 myxa palustris, Eughjpha alveolata, Pamphagus armatus, Mastig- 

 amoeba, Trepomonas agilis, Hexamita inflata, Rhynchomonas 

 nasuta, Heteronema acus, Bodo, Cercomonas, Dactylochlamys, 

 Ctenostomata, etc. The so-called "sewage organisms" abound in 

 such habitat (Lackey). 



Certain free-hving Protozoa which inhabit waters rich in de- 

 composing organic matter are frequently found in the fecal mat- 

 ter of various animals. Their cysts either pass through the aU- 

 mentary canal of the animal unharmed or are introduced after 

 the feces are voided, and undergo development and multiplica- 

 tion in the fecal infusion. Such forms are collectively called copro- 

 zoic Protozoa. The coprozoic protozoans grow easily in suspension 

 of old fecal matter which are rich in decomposed organic matter 

 and thus show a strikingly strong capacity of adapting themselves 

 to conditions different from those of the water in which they 

 normally live. Some of the Protozoa which have been referred to 

 as coprozoic and which are mentioned in the present work are, as 

 follows: Scytomonas pusilla, Rhynchomonas nasuta, Cercomonas 

 longicauda, C. crassicauda, Trepomonas agilis, Dimastig amoeba 

 gruheri, Hartmanella hyalina, Chlamydophrys stercorea and Tilli- 

 na magna. 



As a rule, the presence of sodium chloride in the sea water pre- 

 vents the occurrence of the large number of fresh-water inhabi- 

 tants. Certain species, however, have been known to live in both 

 fresh and brackish or salt water. Among the species mentioned in 

 the present work, the following species have been reported to oc- 

 cur in both fresh and salt waters: Mastigophora: Amphidinium 



