170 RUTH L. PHILLIPS 



rather than to any toxicity of the bacteria used for food. In 

 such cases as the cultures L' and K'L', however, it is very prob- 

 able that the bacteria were toxic, since all Paramecia died within 

 twenty-four hours. 



HISTORICAL AND DISCUSSION 



Whatever the title of the article or scope of the investigation, 

 all who have worked with Paramecium have been concerned 

 directly or indirectly with some phase of the life-history of this 

 animal. Earlier workers did not conceive the complexity of 

 function and behavior revealed by later studies of its metabolic 

 processes. The sum total of these results reveals a striking 

 similarity to the vital processes of many-celled organisms. The 

 food of an animal is not the least important factor in determining 

 its behavior, yet this has sometimes been ignored, sometimes 

 obscured by too great emphasis of other factors by workers with 

 Paramecium, and still remains to be clearly understood. 



The reason for this neglect lies in the fact that since the food 

 of Paramecium consists mainly of bacteria, any study of this 

 factor must necessarily overlap the field of bacteriology. Ac- 

 cordingly, the zoologist has left it alone almost completely, 

 either because of lack of technical skill or because of hesitation 

 to enter unknown territory. Hargitt- and Fray ('17) have de- 

 vised a technic which makes possible the study of the relationship 

 of Paramecium to food. The technic of getting pure cultures of 

 bacteria is the only part of the work essentially new to the pro- 

 tozoologist, and this can easily be learned. 



One of the most striking things met with in reading the litera- 

 ture is that the earliest worker to apply experimental methods to 

 the study of Paramecium (Maupas, '88) had possibly a clearer 

 idea of the importance of food than any who followed him until a 

 few years ago. He says: "Possibly the use of Pasteur's methods 

 for culturing bacteria would prove to be more suited to the needs 

 of the CiUates, but I have never made any attempt in this direc- 

 tion." It seems strange that this very pertinent suggestion 

 should have been so long overlooked, but again it may be that 

 the technical difficulties of obtaining such cultures discouraged 



