186 ORIGIN OF LIFE IN AMERICA 



that during early Tertiary times Antillean species were carried 

 even as far as New Jersey. At no succeeding Epoch, says Dr. 

 Dall, do we find such tropical and semi-tropical molluaks 

 extending northward to such a distance from their present 

 range. All these Tertiary deposits cease north of the Hudson 

 estuary, and I have shown in ,a previous chapter (p. 41) 

 that in later Tertiary times, at any rate, the coasts of New 

 Yor"k, Massachusetts and Maine extended far out into the 

 present Atlantic. The hypothesis of the latter land extension 

 having once joined Bermuda and the Bahamas, etc., seems to 

 me supported by a variety of circumstances which I shall 

 allude to later on. This would have excluded the Atlantic 

 Ocean either partially or wholly from the Gulf of Mexico and 

 the southern Atlantic States. Some time during the Miocene 

 Period, or earlier, a sudden influx of northern species into the 

 area hitherto occupied by southern forms occurred. Dr. Dall 

 and Mr. Harris * endeavoured to account for this phenomenon 

 by the supposition that the course of the Gulf Stream was 

 gradually turned more off shore than it was before or is at 

 present. 



If we assume, however, that a belt of land such as above 

 described had hitherto existed, the gradual breaking down of 

 its northern portion might have admitted the Atlantic waters 

 into the sea which covered the southern States and have 

 brought with it the new fauna, which had meanwhile deve- 

 loped in the northern Atlantic Ocean (see Figs. 14 and 16). 

 For a time these northern, cooler inshore waters were even 

 able to penetrate into the Gulf of Mexico. Even if we grant 

 the correctness of Messrs. Dall and Harris's supposition of the 

 altered course of the Gulf Stream, the cause of this deflection 

 is more likely to have been produced by a change in the con- 

 figuration of the northern land-masses than by that of Florida. 



Let us now study the flora and fauna of Bermuda, and 

 endeavour to ascertain whether it supports in any way the 

 theory I have advocated. f It is quite evident that the existing 

 flora of Bermuda is only a remnant of the original one, before 

 the early settlers, accompanied by hogs and rats, played havoc 



* Dall, W. H., and G. D. Harris, "Correlation Papers," pp. 185187. 

 t Heilprin, A., " The Bermuda Islands." 



