308 PRACTICAL ZOOLOGY 



their food of small animals can be obtained for them only with 

 difficulty. 



Finally the fact should be mentioned that many of the things 

 we know about the physiology of animals have been learned 

 from experiment on frogs, in fact the frog seems to have been 

 " especially designed as a subject for biological research." 



REFERENCES 



The Biology of the Frog, by S. J. Holmes. — The Macmillan Co., N. Y. City. 

 The Frog Book, by Mar)' C. Dickerson. — Doubleday, Page and Co., N. Y. 



City. 

 Nature Study and Life, by C. F. Hodge. — Ginn and Co., Boston, Mass. 

 The Habits, Food, and Economic Importance of the American Tbad, by 



A. H. Kirkland. Bulletin 46, Hatch Experiment Station, Amherst, 



Mass. 



