A NTAY IIKI.D METHOD OF INVESTIGATING THE 



HVDROTROPISMS OF FRESH-WATER 



INVERTEBRATES. 



% 



C. H. TURNER.' 

 TVER TEACHERS' COLLEGE. ST. Loris. Mo. 



INTRODUCTION. 



During the past quarter of a century the tropism idea has 

 stimulated intensive investigation of the factors that serve as 

 directive forces in the behavior of animals. Gravitation, light, 

 heat, contact, wind and water currents, as factors of orientation, 

 have been much investigated; but, the directive influence of 

 bodies of water as such has received scant attention. In her 

 learned textbook, 3 Professor Washburn does not discuss the 

 subject. In his book on animal intelligence 1 Professor Holmes 

 devotes a whole chapter to tropisms. He discusses; chemotaxis, 

 geotaxis, thigmotaxis, rheotaxis, phototaxis, thermotaxis and 

 electrotaxis; but, nut a wurd about hydrotaxis. Professor 

 Botivier. in a recent work, 1 says more on this topic than I have 

 seen in any other book on animal behavior. He writes: 



"No less than heat, water is necessary to living beings, for it 

 constitutes the greater portion of their protoplasm and plays a 

 part in almost all their internal changes. Also, all organisms 

 are sensitive to variations of humidity in the space surrounding 

 them, and with a great number this sensitiveness takes the form of 

 a directive orientation which is called hydrotropism. 



"We know the famous experiments made by Stahl. in 1884, 

 on the hydrotropism of the fungi of the genii- .Ktlmlinm (tanning 

 fungus). The plasmodial mass of thr-i- plants during the vege- 

 tation period, enters the tan, making fur the humidity necessary 



I. Xote by the editor. This parx-r v. >r luiMicaium J. ; s. 1923. 



The author died February 14. 1923. Dr. Turn, t tudent ol P -or C. O. 



Whitman, and received the degiee of DC ;li* University of 



1 .IKO in 1907. His thesis was on "Tin- Homini; <>f Ants: An Experimental 

 Stinly .-I Ant Behavior." He coiuimn-d his putimt. th i imlies of an 



urior to the time of his death, as the present o>iHrii>uti<>n will t--tify. Several 

 by Ur. Turner have api* .ufl in tin- p.i.yrs .>i the Hi' >i.< '<.! AL BULLETIN. 



