556 



SCIENCE. 



[N. S. Vol. XIV. No. 354. 



of other marine life of that region points to 

 the same conclusion." 



"In 1881, Dr. Paul Fischer discussed 

 the same question in his ' Manual de Con- 

 chyliologie,' pp. 168-169, in a section on the 

 Molluscan Fauna of the Panamic Province, 

 and reached the same general conclusions. 

 He says : ' Les naturalistes Americians se 

 sont beaucoup preeoccupes des especes de 

 Panama qui paraissent identiquesavec celles 

 des Antilles, ou qui sont representatives. 

 P. Carpenter estime qu'il en existe 35. 

 Dans la plupart des cas, I'identite absolue 

 n'a pu etre constantee et on a trouve quel- 

 ques caracteres distinctifs, ce qui n'a rien 

 d'etonnant, puisque dans I'hypothese d'une 

 origine commune, les deux races pacifique 

 et atlantique sont separ4e depuis la periode 

 Miocene. Voici un liste de ces especes rep- 

 resentatives ou identiques. ' Here follows 

 a list of 20 species. ' Mais ces formes 

 semblables,' he says, ' constituent un in- 

 fime minorite (3 per cent.).' " 



" These facts have a very important bear- 

 ing upon certain geological questions, par- 

 ticularly upon the one concerning the cold 

 of the Glacial period. 



" In Dr. G. Frederick Wright's recent 

 book ' The Ice Age in ISForth America,' eight 

 dififerent theories as to the cause of the cold 

 are discussed. The particular theory which 

 seems to him quite reasonable is that one 

 which attributes the cold as due to a change 

 of diiferent parts of the countrj^, and a de- 

 pression of the Isthmus of Panama is one 

 of the important changes he considers. 

 He says:-^ "Should a portion of the Gulf 

 Stream be driven through a depression 

 across the Isthmus of Panama into the 

 Pacific, and an equal portion be diverted 

 from the Atlantic coast of the United States 

 by an elevation of the sea-bottom between 

 Florida and Cuba, the consequences would 

 necessarily be incalculably great, so that 

 the mere existence of such a possible cause 



* P. 409. 



for great changes in the distribution of 

 moisture over the northern hemisphere is 

 sufficient to make one hesitate before com- 

 mitting himself unreservedly to any other 

 theory ; at any rate, to one which has not 

 for itself independent and adequate proof." 



''In the Appendix to the same volume 

 Mr. Warren Upham, in discussing the 

 probable causes of glaciation, says, ' The 

 quaternary uplifts of the Andes and Rocky 

 Mountains and of the West Indies make it 

 nearly certain that the Isthmus of Panama 

 has been similarly elevated during the re- 

 cent epoch. * ^ * It may be true, therefore, 

 that the submergence of this isthmus was 

 one of the causes of the Glacial period, the 

 continuation of the equatorial oceanic cur- 

 rents westward into the Pacific having 

 greatly diminished or wholly diverted the 

 Gulf Stream, which carries warmth from 

 the tropics to the northern Atlantic and 

 northwestern Europe." 



" Any very recent means by which the 

 fishes could have passed readily from one 

 side to tlie other would have resulted in 

 making the fish-faunas of the two shores 

 practically identical ; but the time that has 

 elapsed since such a waterway could have 

 existed has been long enough to allow the 

 fishes of the two sides to become ^rac^ica% 

 distinct. That the molluscs of the two 

 shores are almost wholly distinct, as shown 

 by Dr. Fischer, is even stronger evidence 

 of the remoteness of the time when the 

 means of communication between the two 

 oceans could have existed, for ' species ' 

 among the molluscs are probably more per- 

 sistent than among fishes. 



" Our present knowledge, therefore, of 

 the fishes of tropical America justifies us in 

 regarding the fish faunas of the two coasts 

 as being essentially distinct, and believing 

 that there has not been, at any compara- 

 tively recent time, any waterway through 

 the Isthmus of Panama." 



It is thus shown, I think, conclusively, 



