BIBLIOGRAPHY 



A few of the books and articles that have been consulted in preparing 

 this work will be found in the following list. They have been selected 

 chiefly with reference to their accessibility and value to students, and 

 are arranged alphabetically under the headings of the various chapters. 

 Their numbers, corresponding to numbers in parentheses in the text, 

 will facilitate the finding of any particular source of information. 



CHAPTER I 

 INTRODUCTION 



1. Aspects of the Species Question. Papers read at a symposium at 



Chicago, Jan. i, 1908. 1908. Amer. Nat., vol. 42, pp. 218-281. 



2. Darwin, C., 1861. The Origin of Species by means of Natural Selec- 



tion. New York. 



3. Harmer, S. F., and A. E. Shipley. Editors. The Cambridge Nat- 



ural History. 10 vols. London. 



4. liertwig, R., 1902. Manual of Zoology. Translated by J. S. 



Kingsley. New York. 



5. Lankester, E. R. Editor. A Treatise on Zoology. London. 



6. Parker, G. H. 1908. Zoological Progress. Amer. Nat., vol. 42, 



pp. 115-133- 



7. Parker, T. J., and W. A. Haswell, 1897. Text-book of Zoology. 



2 vols. London. 



8. Thomson, J. A., 1906. Outlines of Zoology. 4th ed. London. 



9. Williston, S. W., 1908. What is a Species? Amer. Nat., vol. 42, 



pp. 184-194. 



10. Zittel, K. A. von, 1900-1902. Text-book of Paleontology. 2 vols. 



Translated by C. R. Eastman. London. 



CHAPTER II 

 PHENOMENA OF LIFE 



11. Biitschli, O., 1894. Investigations on Microscopic Foams and on 



Protoplasm. London. 



12. Dahlgren, U., and W. A. Kepner, 1908. Text-book of the Prin- 



ciples of Animal Histology. New York. 

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