PREFATORY NOTE. 



Mr. V. A. Clark, as a student in horticulture in 

 the University of Vermont, first undertook a crit- 

 ical examination of Nageli's Mechanico-Physiological 

 Theory of Evolution as a part of his regular junior 

 work. After a half year's study and the prepara- 

 tion of a short thesis, Mr. Clark had become so far 

 intimate with Nageli's work as to make it seem 

 best for him to continue the study through his 

 senior year. This study involved extended trans- 

 lations from the text, including Nageli's Summary, 

 which, considering its difficult accessibility to Ameri- 

 can students, has been chosen for publication. The 

 work has been done chiefly by Mr. Clark, but has 

 all been under my immediate supervision, and I 

 have given the whole matter a final restudy and 

 revision. Those who have had any experience with 

 similar work will know how impossible it is that all 

 mistakes should have been avoided, and it would be 

 a kindness to the translators if readers would point 

 out any defects, in order that they may be cor- 

 rected. 



F. A. WAUGH. 

 University of Vermont, 

 July i, 1898. 



