OBSERVATIONS ON THE ECOLOGY OF THE 

 PROTOZOA 



By LEON AUGUSTUS HAUSMAN 



A GREAT deal of excellent work has been done in census 

 taking among the Protozoa, and numerous catalogues of 

 species with descriptions and accompanying plates have 

 been issued for various states or portions thereof. This 

 present communication, however, is a slight contribution 

 toward census taking of a different sort, in that it aims to 

 set forth some facts regarding the different types of Pro- 

 tozoan habitats and the species usually associated with 

 each. It is well known that certain common forms, used 

 as type species in the laboratory (such as Amoeba proteus 

 and Paramoecium caudatum), can be found only in certain 

 fairly definite environments. The ecology of such forms 

 is well known, but the bionomics of the majority of the 

 Protozoa is still virtually a res ignota. The study of en- 

 vironmental units and Protozoan communities will con- 

 tribute to a more intimate knowledge of these elusive 

 forms. 



Although little is definitely known concerning the ecol- 

 ogy of the Protozoa, yet I think that we are in position to 

 say that Protozoan inhabitants vary with their varying en- 

 vironments. A record of the inhabitants of a marsh pool 

 will not include the same species normally found in clear 

 running streams, nor will cold waters yield the same forms 

 as warm. But we can go still farther, I think, and say that 

 the various portions of any given environmental unit, 

 even though they differ ever so slightly from one another, 

 will each have its own characteristic group of organisms. 

 The factors which are accountable for the variation in 

 species or numbers of individuals of any species in such 

 instances may be hardly discoverable, but they are none 

 the less potent. Thus the entrance point of a tiny thread 



