180 BIOLOGY: GENERAL AND MEDICAL 



is one of the first functions to make its appearance in the 

 lower forms of life. No separation of the two branches of 

 the nervous system into sensory-motor and sympathetic 

 systems can be made out in animals lower than the arthro- 

 pods, with the single exception of the leeches. 



REFERENCES. 



THOMA.S H. HUXLEY: "Anatomy of Invertebrated Animals," 



N. Y., 1885. "Anatomy of Vertebrated Animals." 



N. Y., 1886. 

 W. T. SEDGWICK AND E. B. WILSON: "An Introduction to 



General Biology," N. Y., 1895. 

 A. S. PACKARD: "Zoology" N. Y., 1895. 

 A. T. MASTERMAN: "Elementary Text-book of Zoology," 



Edinburgh, 1902. 



T. W. GALLOWAY: "First Course in Zoology," Phila., 1906. 

 ANTON KERNER VON MARILAUN: "The Natural History of 



Plants." Translated by F. W. Oliver, N. Y., 1894. 

 E. STRASBURGER, F. NOLL, H. SCHENCK, AND G. KARSTEN: "A 



Text-book of Botany," translated by W. H. Lang, N. Y. 



and London, 1908. 

 J. Y. BERGEN AND B. M. DAVIS: "Principles of Botany," N. Y., 



1906. 

 T. J. PARKER: "Lessons in Elementary Biology," London, 1893. 



