1914] 
Jackson; Land Vertebrates of Ridgeway Bog 
ol 
is from the south and is represented in part in the Roadside Asso- 
ciation; this last ingression is still in process, several members 
of it having ingressed the region during the past few years. 
VII. ACKNOWLEDGMENTS 
It is a pleasure for me here to express my gratitude to all who 
have in any way aided me in my present studies. I am especially 
obligated to Dr. L. Stejneger for identifying a specimen of Rana 
septentrionalis and for allowing me access to card catalogues in the 
U. S. National Museum, to Dr. C. E. Allen for identifying certain 
specimens of plants, to Mr. H. C. Oberholser for suggestions con- 
cerning faunal affinities of birds, to Dr. C. A. Davis for suggestions 
and criticisms in regard to centers of plant dispersal, to Dr. Paul 
Bartsch for kindly criticisms and for reading the entire manuscript, 
and to my wife, Anna M. Jackson, who collected many of the 
plants and who has done much of the routine work connected 
with the investigation. 
VIII. BIBLIOGRAPHY 
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graphic Distribution of Flora and Fauna. Biol. Bull., vol. 3, 
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1902 b Postglacial Origin and Migration of the Life of North- 
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357. 
1905 The Postglacial Dispersal of the North American Biota. 
Biol. Bull., vol. 9, pp. 53-71. 
1913 Guide to the Study of Animal Ecology. New York. 
Adams, C. C., and others 1909 An Ecological Survey of Isle Royale, 
Lake Superior. Report Geol. Surv. IMichigan, 1908. 
Bailey, Vernon 1896 Tamarack Swamps as Boreal Islands. Science, 
new series, vol. 3, pp. 250-251. (Abstract of paper presented 
at the 254th meeting of the Biol. Soc. Washington, January 25, 
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Brown, A. E. 1904 Post-glacial Nearctic Centres of Dispersal for Rep- 
tiles. Proc. Acad. Nat. Sci. Philadelphia, vol. 56, pp. 464-474. 
Clements, F. E. 1905 Research Methods in Ecology. Lincoln, Nebraska. 
Colton, H. S. 1908 Some Effects of Environment on the Growth of 
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