The Negative Geotropism of the Periwinkle: A Study 

 IN Littoral Ecology. — By F. Ronald Hayes, B. Sc, 



Assistant in Histology and Embryology, Dalhousie Uni- 

 versity, Halifax, N. S. 



(Presented 18 January, 1926) 



Table of Contexts 

 SECTION PAGE 



I Introduction '. 155 



II Experimental Technique 159 



III Correlation of Negative Geotropism with Vertical Habitat 161 



IV Variation in Negative Geotropism Due to the Effects of Desiccationl62 

 V The Effect of Continued Immersion on Negative Geotropism. . . . 167 



VI The Effect of Temperature on Negative Geotropism 169 



VII Summary and Conclusions 171 



I. Introduction 



Various investigators have interested themselves from 

 time to time in an investigation of the anatomical and phy- 

 siological features associated with the negative geotropism 

 of snails (Parker 1911; Kanda 1916-1), and various theories 

 have been set forth in an attempt to account for this pheno- 

 menon. 



As early as 1897 Davenport and Perkins experimenting 

 on Limax maximus, came to the conclusion that "the precision 

 of orientation in the slug varies directly with the active com- 

 ponent of gravity" and "this tendency (to go either up or down) 

 must be ascribed to some internal condition of the individuals, 

 for it varies in different individuals and in the same individuals 

 at different times." It was early suspected moreover, that 

 response to gravity might be associated with the center of 

 gravity of the body of the individual, and Frandsen (1901), 

 also speaking of Limax, makes the assertion that the essential 



