Tlie Moon Snail 49 



in solution to the ocean by rivers and unclergrouiul 

 streams, there unites witfi its proper proportion of 

 chlorine, the chemical union forming the salt of the sea. 

 It becomes obvious, then, that as we go farther and 

 farther back in point of time, the primordial waters 

 become rarer and rarer in those earth-derived elements 

 that make up the content of the present existing sea. 

 In other words, to put it conversely, the sea became 

 more salty with each succeeding age. Therefore, it 

 is extremely probable that the early mollusks had their 

 beginning in a fresh-water sea. And then, also, of 

 course, as well as now, the tides prevailed. 



