by f. roland hayes, b. sc. 

 Table 2. 



163 





"IMMERS 



^D" GROUP 



"DRY" 



GROUP 



Desiccation 

 Time 

 Hours 



Percentage 

 responding 



Amount of 



response per 



animal per ten 



minutes 



Centimeters 



Percentage 

 responding 



Amount of re- 

 sponse per 

 animal per ten 

 minutes 

 Centimeters 



0.0 



70 



7.2 



10 



5.0 



•1.0 



70 



11.2 









1.5 



100 



14.0 



20 



5.0 



2.0 



100 



6.5 









2.5 



70 



5.4 



20 



7.5 



3.0 



100 



9.2 









It will be seen from the "immersed" group figures of this 

 table that the result of desiccation for a short time is at first 

 to increase both the percentage of individuals exhibiting nega- 

 tive geotropism and the amount of response. 



This correlates with what might have been expected from 

 a consideration of the face that animals living at higher tidal 

 levels, and therefore subjected to longer periods of intertidal 

 desiccation than individuals lower down in the littoral zone, 

 exhibit a higher figure for their negative geotropism. Thus 

 the effects of short periods of desiccation entirely confirm the 

 results recorded in Table 1. 



The figures in the "dry" group column are seemingly 

 irregular and a suggested explanation is that they are in ac- 

 cord with the observed facts of the life of this form, where 

 there exists a decided lack of activity when the tide is out. 



Periwinkles do not move about in search of food after the 

 substratum has thoroughly dried. They are under the nee- 



