PEEFACE BY THE AUTHOR 



The purpose of these lectures is to point out the means 

 and methods by which the origin of species and varieties 

 may become an object for experimental inquiry, in the 

 interest of agricultural and horticultural practice as well 

 as in that of general biologic science. Comparative 

 studies have contributed all the evidence hitherto adduced 

 for the support of the Darwinian theory of descent and 

 given us some general ideas about the main lines of the 

 pedigree of the vegetable kingdom, but the way in which 

 one species originates from another has not been ade- 

 quately explained. The current belief assumes that spe- 

 cies are slowly changed into new types. In contradiction 

 to this conception the theory of mutation assumes that 

 new species and varieties are produced from existing 

 forms by sudden leaps. The parent-type itself remains 

 unchanged throughout this process, and may repeatedly 

 give birth to new forms. These may arise simultaneously 

 and in groups or separately at more or less widely dis- 

 tant periods. 



The principal features of the theory of mutation have 

 been dealt with at length in my book " Die Mutations- 

 theorie" (Vol. I., 1901, Vol. II., 1903. Leipsic, Veit 

 & Co.), in which I have endeavored to present as com- 

 pletely as possible the detailed evidence obtained from 

 trustworthy historical records, and from my own experi- 

 mental researches, upon which the theory is based. 



The University of California invited me to deliver a 

 series of lectures on this subject, at Berkeley, during the 



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