PHYSIOLOGY 



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end or the whole side in direct contact with the object, in which 

 position it ingests food particles through the cytostome. 



Reaction to gravity. The reaction to gravity varies among dif- 

 ferent Protozoa, according to body organization, locomotor or- 

 ganellae, etc. Amoebae, Testacea and others which are usually 

 found attached to the bottom of the container, react as a rule 

 positively toward gravity, while others manifest negative reac- 



FiG. 47. Reactions of Paramecium (Jennings), a, collecting in a drop 

 of 0.02% acetic acid; b, ring-formation around a drop of a stronger 

 solution of the acid; c, avoiding reaction. 



tion as in the case of Paramecium (Jensen; Jennings), which ex- 

 plains in part why Paramecium in a culture jar are found just be- 

 low the surface film en mass, although, according to Dembowski 

 (1929) the vertical movement of Paramecium caudatum is influ- 

 enced by various factors. 



Reaction to current. Free-swimming Protozoa appear to move 

 or orientate themselves against the current of water. In the case 

 of Paramecium, Jennings observed the majority place them- 

 selves in line with the current, with anterior end upstream. The 

 myoetozoan is said to exhibit also a well-marked positive reaction. 



