158 THE NEGATIVE GEOTROPISM OF THE PERIWINKLE 



Situated on an estuary of the Bay of Fundy, the Atlantic 

 Biological Station where the greater part of the work here re- 

 corded was carried out, presents ideal conditions for a study of 

 the littoral zone. A tidal change of over 8 metres exposes at 

 low tide, an area of considerable width, exhibiting very clearly 

 all the features associated with an inter-tidal graduation of 

 fauna and flora. 



The littoral zone, in the area where the greater number of 

 collections were made, was comprised of a series of rocky ledges 

 forming an ideal habitat for the periwinkle. L. littorea exists 

 in considerable numbers from a short distance above the lowest 

 tidal level to slightly above the mid tide level. It exists below 

 low tide level in smaller numbers to depths of at least 20 fathoms 

 (Huntsman, 1918), and above mid tide level in tide pools and 

 under permanently damp conditions. 



Sincere thanks must be given to Prof. J. Nelson Gowanloch 

 of Dalhousie University, for his interest and counsel and for 

 personal direction of a great part of the investigation. I am 

 also indebted to Dr. A. G. Huntsman, Director of the Atlantic 

 Biological Station for advice and assistance at every stage of 

 the work. Certain lines of the investigation were continued 

 throughout the winter at the Zoological Laboratories of Dal- 

 housie University, Halifax, N. S. 



