ALONG THE STREAM 235 



bridge existed it is certain that with the advent 

 of tropical plants a large number of Cuban snails 

 would have migrated to our region. As it is one can 

 almost count on his fingers all such species living 

 within our territory or which by any possibility 

 could have been derived from them. This is 

 exactly the condition we would expect to find 

 if life from Cuba had been brought to Florida by 

 ocean currents. 



Florida is so lacking in any striking natural 

 features that the few it possesses receive exagger- 

 ated names, and so it happens these short water 

 courses have been called "rivers." They are all 

 divided into two quite distinct parts first an 

 upper, fresh-water stretch reduced to a rivulet or 

 a dry bed in winter or becoming a powerful 

 stream in the rainy season; and second, a lower, 

 estuarine part of generally brackish water in which 

 the tide ebbs and flows. A few of them on the 

 east coast flow between low limestone walls, hav- 

 ing doubtless begun their existence as water 

 passages under the rock. Cutler and Snapper 

 creeks were examples of this before their channels 

 were artificially opened, and Arch Creek still 

 passes under a natural bridge. 



