THE BEHAVIOR OF OTHER INFUSORIA 127 



ward, and at the same time to circle to the right (Fig. 85). But they do 

 not alternate this with movement forward, as Paramecium and Oxytricha 

 do, and they do not revolve on the long axis. Bursaria simply continues 

 the reaction once begun, and this of course has little tendency to remove 

 the organisms from the heated region. They circle about till they die. 

 Among different infusoria all gradations may be found, from the inef- 

 fective reaction of Bursaria through the moderately rapid but effective 

 behavior of Oxytricha to the quick movements of Paramecium, which 

 can be followed only with much difficulty. 



Mendelssohn (1902) has determined the optimum temperature for a 

 considerable number of infusoria. He finds the-following values : Para- 

 mecium aurelia, 24-28 degrees; P. bursaria, 23-25; Pleuronema, 25-27; 

 Colpoda, 25-31; Spirostomum teres, 24-33; Coleps, 28-31; Stentor, 

 25-28; Chlorogonium, 23-30. As a rule the organism is stimulated by 

 temperatures both above and below the optimum, so that it seeks the 

 optimum region. But in rare cases a higher temperature acts as a 

 stimulus, while a lower temperature does not. This is true, according 

 to Mendelssohn, in Pleuronema. 



If the entire vessel containing the infusoria is heated, or if the ani- 

 mals are dropped into heated water, the avoiding reaction is produced, 

 just as when the heat is apphed from one side. The animals swim back- 

 ward and turn to one side. It is thus evident that there need not be dif- 

 ferences of temperature in different parts of the body in order to produce 

 the avoiding reaction. In the experiment just mentioned the animal 

 "tries" swimming in many different directions, but of course does not 

 find a direction that takes it away from the heated region. 



LITERATURE VII 



Behavior of Infusoria in General 



A. Action systems, methods of movement and reaction : Jennings, 1900, 1899 6, 

 1902; Putter, 1904; Naegeli, i860; Rothert, 1901. 

 £. Reactions to contact with solids: Putter, 1900. 



C. Reactions^to_chemicals^: Pfeffer, 1884, 1888; Massart, 1889, 1891 ; 

 Rothert, igei, 1903; Garrey," 1900 ; Dale, 1901 ; Greeley, 1904; Jennings, 

 1900 a, 1900^; Jennings and MooRp, 1902. 



D. /Reactions to heat and cold: Jennings, 1904; Mendelssohn, 1902, 1902 a, 

 1902 6. 1 



