164 



THE NEGATIVE GEOTROPISM OF THE PERIWINKLE 



essity of conserving their supply of moisture till they are once 

 more immersed by the incoming tide. A general consideration of 

 all the "dry" group experiments here recorded will be found 

 elsewhere in this paper. 



In Table 3 figures are found showing the effect of a longer 

 period of desiccation on negative geotropism. It will be ob- 

 served that there are no "dxy" group results given. The rea- 

 son is that after a relatively short period of desiccation there 

 was a total absence of activity of the periwinkles except under 

 the stimulus of water. The animals whose performance is re- 

 corded in Table 3, were desiccated in a laboratory on a shelf 

 over a large aquarium through which salt water was flowing. 

 They were thus in an atmosphere containing a considerable 

 quantity of moisture and at no time exposed to excessive heat. 



Table 3 





"IMME 



RSED" GROUP 



DESICCATION 

 TIME 

 HOURS 



PERCENTAGE 

 RESPONDING 



AMOUNT OF RESPONSE 

 PER ANIMAL PER TEN 

 MINUTES IN CENTIMET- 

 ERS 







90 



16.8 



7 



30 



15.8 



27 



30 



9.3 



45 



50 



6.0 



91 



50 



0.7 



118 



50 



0.8 



141 



40 



0.7 



172 



20 



2.8 



262 



30 



0.6 



335 



10 



1.6 



