ASIATIC INVADERS IN AMERICA 
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basis for discussion of some of the problems referred to. 
Other attractive inquiries, such as the influence of the Glacial 
Epoch on animal migrations, might be elucidated. "With the 
climatic problem alone are connected so many important geo¬ 
logical speculations that the subject is well worthy of a most 
careful scrutiny. 
At a meeting of the Biological Society of Washington about 
ten years ago the theme chosen for discussion was the sup¬ 
posed former land bridge between Asia and North America. 
Dr. F. A. Lucas spoke in favour of a geologically recent brief 
land connection, and supported his theory by the geographical 
distribution of the wild sheep and the brown bears of North 
America, both of which have their near relations in Asia. 
He also pointed to the remains of mammoth and bison in 
Alaska as evidence of the same view. An older land connec¬ 
tion, he thought, was indicated by the occurrence of a fossil 
Nemorrhaedus in Colorado and of Elephas columbi. Dr. 
Theodore Gill concurred with the last speaker, and suggested 
that the presence in America of such species of fishes as the 
pike and Scaphirhvnchus tended in favour of the older land 
connection. Mr. F. V. Coville dwelt upon the importance of 
plants in sustaining the view of a transient and geologically 
recent land bridge. Additional testimony in favour of an 
old land connection of long duration was brought forward by 
Dr. Stejneger. He particularly emphasised the occurrence 
in Asia and America of the alligator and the salamander 
Cryptobranchus. Dr. W. H. Dali alone dissented from the 
opinions expressed, urging that such mammals as the 
mammoth might have crossed over Bering Strait by an ice- 
bridge which he thought might have joined North America 
and Asia during the Glacial Epoch.* 
Dr. Dali f gave no reasons for his aversion to the belief 
in a geologically recent land connection between North 
America and Asia; although, in acknowledging that north¬ 
eastern Asia and Alaska have certain species of land and 
fresh-water mollusks in common, he recognised the intimate 
relationship existing between the two areas. 
* Lucas, F. A., Th. Gill, and others, “Former Land Connections.” 
t Dali, W. H., “ Mollusk Fauna of Alaska and Eastern Siberia,” 
pp. 365—366. 
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