REACTIONS OF PLANARIA TO WATER. 125 



4. Reversal of reaction from positive to negative can be in- 

 duced by changing the composition of the water; and from nega- 

 tive to positive by return to the former conditions. 



5. Similar reversals of reaction can be induced by sudden 

 changes in temperature. 



6. Rheotropic reactions are given by Planaria dorotocephala 

 in nature. 



7. Rheotropic reactions are very characteristic of these animals 

 in the laboratory, rather than unusual as has been supposed. 



IX. BIBLIOGRAPHY. 

 Alice, W. C. 



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