OP ARTS AND SCIENCES. 133 



high antiquity, dating back to the post-tertiary, or even 

 to the later tertiary epoch, — and therefore must have been 

 subject to great climatic changes, accompanied or caused by 

 no inconsiderable changes in the relative extent and configu- 

 ration of the land, — the objections formerly raised against 

 such wide dispersion of species lose most of their force. 

 And the explanation of such anomalies in the actual distri- 

 bution of species is to be sought in the vicissitudes to which 

 the species must have been subject in their earlier days. 



Professor Gray proceeded briefly to intimate, that, if the 

 present flora of the northern hemisphere preceded the glacial 

 period, or even immediately succeeded it, the actual distribu- 

 tion of species, and the interchange between this continent 

 and Eastern Asia under similar parallels of latitude, could be 

 readily accounted for on the ordinary view ; or at least would 

 offer no greater difficulty than the Arctic ffora now does, — the 

 general homogeneousness of which round the world has never 

 been thought difficult of explanation. He proposed to illustrate 

 his views upon this part of the subject at a future meeting. 



Professor Agassiz remarked, that the animal kingdom pre- 

 sented a resemblance between its representatives of Eastern 

 North America and Eastern Asia similar to that mentioned 

 by Dr. Gray in the flora, and that he has especially pointed 

 out this correspondence in detail in the order of Testudi- 

 nata, in his Contributions to the Natural History of North 

 America. He acknowledged the correctness of the views 

 ascribed to him by Dr. Gray, and would defend them on 

 the ground that, connecting the present state of things with 

 that which prevailed in earlier geological periods, it could 

 be shown that the present distribution of animals was linked 

 with that of earlier periods in a manner which excluded the 

 assumption of extensive migrations, or of a shifting of the 

 florae and faunae from one area to another. 



He viewed the similarity between the fauna of North- 

 eastern America and that of Northeastern Asia, not as the 

 result of climatic changes over an area primitively more 



