MOVKMKNTS, ETC., OF FEI']SH-WATRR TLANARJANS. 511 



b. Reactions to Chemical Stimuli — Cliemotaxis 



1. Reactions to Localised Chemical Stimuli 



a. Methods 

 j3. Results 



2. General Summary 



3. Unlocalised Action of Chemical 

 ITT. Thifjmotaxis and the Ri^htinj? Reaction 



a. Thiii;motaxis 



b. The Riifhtinj^ Reaction 



The ]\[echauism of the Reaction 



c. Summary 

 TV. Elect rot ax is 



a. Methods 



b. liesults 



c. Mechanism of the Reactions 



d. Summary 

 V. Tieaction to Desiccation . 



VT. Rlieotaxis 

 G. General Summary and Di.scussion of Results 

 H. List of Literature 



page 

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 670 

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 676 

 684 

 685 

 685 

 685 

 690 

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 695 

 697 

 698 

 7T0 



A. Introduction. 



The present study has for its purpose the analysis of the 

 l)ehaviour of the coinniou fresh-water planarian into its com- 

 ponent factors. It is well known that, aside from the 

 researches of a few investigators on a small number of forms, 

 we have little detailed knowledge of the behaviour of lower 

 organisiiis. It is coming to be realised, too, tliat knowledge 

 of what an animal does is just as important in the general 

 study of life phenomena as a knowledge of how it is con- 

 structed, or how it develops. But it must be admitted that 

 until quite recent times the study of the activities of living 

 things was a much neglected field in biology. The 

 publication of the ' Origin of Species ' gave the biological 

 pendulum a swing towards the study of phylogeny, from 

 which it is onl}' just beginning to return. 



As a consequence of this concentration of interest on other 

 subjects, we possess an accurate and full knowledge of the 



