A STUDY OF WELK 137 



Calculations of the total water content of the animals 

 in per cent of total weight exclusive of shell gave remarkably 

 uniform results, the percentages for five individuals with total 

 weights of 38.35, 8.25, 13.97, 16 5 and 36.07 grams each being 

 79 per cent, 81 per cent, 79 per cent, 82 per cent and 81 per 

 cent respectively. 



The interpretation of this curious piece of ecology is ap- 

 parently quite simple. In its normal habitat Buccinnm does 

 not become an inter-tidal animal since its upper limit of distri- 

 bution brings it only to the edge of the lowest low tides. In 

 the Bay of Fundy the exceptional tidal conditions created by 

 the converging coasts produce a tidal change so great that 

 during the spring phase those individuals of Buccinum that 

 have wandered shorevvard find themselves suddenly trans- 

 formed from animals continuously submerged deeply under 

 the waters of an unusually cold bay into animals exposed for 

 hours to the desiccating action of the sun. The reactions that 

 this exposure evokes from them are the reactions fitted for their 

 normal submerged existence. In the new dangers of the inter- 

 tidal zone exposure this behaviouristic response is the most 

 disastrous one possible and leads to the early death of the in- 

 dividuals unless they are soon covered again by the incoming 

 tide. This elimination of the upper, shoreward fringe of the 

 Buccinum population exerts no permanent modifying selective 

 action upon the species as a whole for the quite sufficient reason 

 that it affects only some of the animals of one sharply local 

 region. 



