No. 400.] REACTIONS OF INFUSORIA TO CHEMICALS. 265 
metrical organisms, such as are a large proportion of the 
Infusoria. 
3. Observation of the movements of the Infusoria, both the 
unsymmetrical and the symmetrical, shows that they do not 
orient themselves even approximately in the manner above ex- 
pressed, but that they swim as a rule in spirals, and orientation 
usually takes place through a motor reflex, characterized by 
the fact that the organism, when it turns, turns toward a 
structurally defined side. 
4. A sudden change in the stimulus is not necessary to pro- 
duce a motor reaction, as Garrey has stated, for the organism 
itself, by moving, comes into new relations with a constant 
stimulus, and by these new relations the motor reflex may be 
caused, resulting in a readjustment of orientation. 
5. The gatherings of Chilomonas in drops of organic acid, 
described by Garrey, take place, according to my observations,! 
through the mechanism of the motor reaction of Chilomonas, 
described in the Fifth of my Studies. Whether this is “true 
chemotropism” or not depends on the definition of chemo- 
tropism. 
6. The orientation of Chilomonas takes place through this 
motor reaction, and in general it is impossible for an unoriented 
organism to become oriented except through a motor reaction 
of some sort (except where passively moved, like a dead body). 
ANN ARBOR, MICH., Feb. 6, 1900. 
1 The observations on which this statement is based are detailed in a paper by 
the author in the April number of the American Journal of Physiology. 
