BY F. ROLAND HAYES, B. SC. 157 



that the former were in any way larger than the latter. In 

 other words the climbing habit is just as strongly developed 

 in young winkles as in older ones." 



This assertion is not in agreement with that of Kanda 

 (1916-2), who states that in his experiments on the negative 

 geotropism oi h. litiorea, he used animals about 1.5 by 1.1 

 centimetres because the larger ones were noticed to be more 

 sluggish in commencing locomotion after being handled. "The 

 younger animals are more active and quicker to respond to 

 stimuli." Results from a series of preliminary experiments 

 conducted with the object of determining if possible, a re- 

 lationship between size and activity, support the view of Tatter- 

 sall. 



A "physiological agreement" has been shown to exist 

 in many animal groupings in nature (Shelford 1913). By this 

 agreement species may be said to be automatically directed 

 toward their appropriate habitat. Studies have indicated 

 that a directive mechanism exists, consisting of a remarkable 

 assemblage of delicate adjustments of organism to environment. 

 This mechanism results in cases where choice is possible, in a 

 return of the animal to its optimum habitat. 



The investigations here described were designed in an 

 attempt to analyze in quantative terms, the influence of a 

 separate environmental factor namely gravity, in determining 

 the natural distribution oi Liitorina litiorea. 



Experiments were conducted in an effort to determine in 

 quantative terms, whether there existed in specimens of L. 

 littor e a coWecled at different levels of the littoral zone, a variation 

 in the negative geotropism which could be directly correlated 

 with vertical habitat. The results indicated that such a varia- 

 tion does exist and an analysis was then made of the effects of 

 desiccation and immersion on negative geotropism. 



Desiccation and immersion serve as clues to the study of 

 littoral ecology since, in Littorina for example, the essential 

 difference in habitat of individuals in upper and lower littoral 

 zones is a difference in the length of time they are successively 

 submitted to the influence of these two conditions. 



