ORGANIC MOVEMENTS 19 



near to the views sketched here, though he was (and is) far 

 from admitting the resolution of all kinds of " taxis ' in 

 this way. 1 



Chemotaxis thus is proved by Jennings to be a mere 

 resulting effect of many different single performances, and is 

 not a simple and immediate process of orientation at all. 2 



And what holds with regard to chemicals is also true 

 with regard to heat, light, contact, and any other stimulus 

 except the galvanic current, and applies not only to Infusoria, 

 but also to Flagellata, and Bacteria, and Rotatoria, and all 

 other sorts of invertebrate animals ; as far at least as 

 experiments in the style of Jennings have been carried out. 

 Therefore, though we cannot say at present that no case 

 whatever of " taxis " exists (except galvanotaxis), we shall 

 not, I believe, be very far wrong in saying that probably 

 the range of " taxis " will prove finally to be at least very 

 restricted. 



It now might seem that the typical motor reaction 

 shown by Paramccium, either in leaving or in entering the 

 solution applied in the experiment, is of the type of a true 

 reflex of the most simple kind, and that, therefore, in spite 

 of the resolution of the concept of " taxis," as maintained 

 by Jennings, the simple reflex would be the actual basis of 



1 I cannot agree with Walter (Journ. exp. Zool. 5, 1907. Here full 

 literature on the subject), when, in his studies on the reactions of Planaria 

 to light, he applies the term " Phototaxis " to reactions of this worm towards 

 differences of the intensity of illumination. The word "taxis" strictly 

 depends on the theory that refers to the direction of a stimulus exclusively. 



2 I should not believe that the resolution of "taxis," according to the 

 analysis of Jennings, would apply to the phenomena of the wandering of 

 embryonic cells to specific localities in the case of " directive stimuli " (see 

 vol. i. p. 104). The old theory might also hold perhaps in cases of "in- 

 flammation " and the protective migrations of cells in general (Metschnikoff ; 

 see also vol. i. p. 206). 



