138 Journal of Comparative Neurology and Psychology. 



THE BASIS FOR TAXIS AND CERTAIN OTHER TERMS IN THE BE- 

 HAVIOR OF INFUSORIA. 



In the directed reactions of lower organisms we find repeat- 

 ed attempts by various authors to distinguish in one way or an- 

 other two great classes of phenomena, and for these two classes 

 different terms have been used. Thus Rothert^ distinguishes 

 two sorts of taxis, strophic and apobatic, depending on the 

 manner in which they are brought about. Strophic taxis cor- 

 responds to the typical taxis or tropism of Verworn or Loeb. 

 It is conceived as brought about by a turning of the organism 

 toward or from the source of stimulation, due to a difference in 

 the intensity of action of the stimulus on the two sides or ends of 

 the organism. Apobatic taxis is defined as produced by a back- 

 ward movement at passing from one concentration to another.'* 

 The typical case for this is the reaction method of bacteria. Roth- 

 ert includes under apobatic taxis the reaction of Paramecium and 

 other infusoria to chemicals, etc., though for this his definition 

 is inadequate, since the backward movement is only a compara- 

 tively unimportant detail of the behavior, and is often omitted.^ 



Pfeffer^ rejects Rothert's terms, substituting for stroph- 

 ic taxis the word topotaxis, for apobatic taxis the word phobo- 

 taxis. Massart^ applies the term taxis only to the phenomenon 

 called by Rothert strophic taxis, while the word phobism is 

 proposed for the backward movement called by Rothert apo- 

 batic taxis. 



Davenport" makes in his discussion of the reactions to 

 light a distinction corresponding to a certain extent with those 

 already mentioned. He distinguishes reactions whose direc- 

 tion is determined by the direction of the rays of light, from re- 



^ Flora, 88, 1901, p. 393. 



"^Rothert, I. c. p. 393. 



'See the account by the present author, this Journal, 14, 1904, pp. 458-460. 



*Pflanzenphysiologie, Bd. 2, 1904, p. 755. 



^Annaks de r Institute Pasteur, 1901, p. 25. ' 



^Experimental Morphology, vol. 1, 1897, p. iSo. 



