182 The Philippine Journal of Science i9i8 



of pond or tap water ; a heterogeneous mixture of protozoan, bac- 

 terial, and fungoid organisms mixed with lower metazoan forms 

 such as Rotifera, Crustacea, and so forth. In such cultures a 

 complex series of reactions can be generally observed accom- 

 panied by cyclic changes in the floral and faunal composition of 

 the culture. 



Pure mixed cultures. — These involve the cultivation of one 

 species of protozoa in association with a pure strain of one other 

 microorganism, such as a bacterium or some other protozoon. 

 Although this is frequently referred to as a condition of symbio- 

 sis, such is not the case, for the associated organism serves as 

 a source of food for the protozoon. 



Pure cultures. — These are cultures of protozoa grown on a 

 medium containing no other organism. The technic involved in 

 the construction and maintenance of such cultures necessitates 

 a close attention to conditions of asepsis and the employment of 

 the methods of the bacteriologist. 



Transitional between the last two methods may be said to be 

 that by which certain protozoa may be grown in media sown 

 with killed bacteria. 



A great impetus was given to work with the parasitic protozoa 

 through the introduction in 1903 by Novy and MacNeal ^° of 

 bacteriological methods in the cultivation of parasitic protozoa. 

 The general tendency among protozoologists to-day is to adapt 

 the methods of the bacteriologist to the cultivation of free-living 

 as well as parasitic protozoa. The strange thing about the 

 whole affair lies in the neglect to do this to a greater extent 

 in the past. 



It would require too much space to detail the various methods 

 for cultivating protozoa in a paper such as this. So far as may 

 be possible, methods for cultivating individual species will be 

 given in connection with the descriptions that will follow. 



Study of the living organism. — A moderate degree of fami- 

 liarity with the use of the microscope is presupposed in studies 

 of this kind. The relatively quiescent forms such as the Sar- 

 codina, sessile flagellates (Mastigophora), Sporozoa, and Suc- 

 toria (Infusoria) are kept in the microscopic field with com- 

 parative ease, particularly if the observer is using a mechanical 

 stage. Actively moving flagellates and ciliates are often very 



" Novy, F. G., and MacNeal, W. J., On the cultivation of Trypanosoma 

 lewisi. Contribution to medical research, dedicated to V. C. Vaughan. 

 Ann Arbor, Mich. (1903), 549. 



