PREFACE 



The following pages are the slightly expanded notes of 

 a course of lectures which the writer has been giving to 

 agricultural students for the past ten years. They con- 

 stitute an introduction to plant and animal breeding, sub- 

 jects of great and growing importance in modern agriculture. 



The treatment is from a biological standpoint for the 

 student who desires to specialize in animal husbandry, 

 cereal husbandry or horticulture should have clear concep- 

 tions of the more important problems of organic evolution 

 and of the main laws and theories relating to variation, 

 heredity and related subjects. The discussion of the more 

 direct application of the principles discussed has been left 

 to the special departments. 



The general public is taking an intelligent interest in 

 many genetic problems, especially those relating to Eu- 

 genics. While the discussion may at times appear too 

 technical for the average reader, it is believed that even 

 these parts may be understood by him after a little careful 

 study. - 



Frequent references are made to larger works which 

 contain fuller and more extended discussions of many of 

 the topics treated, and it is the writer's hope that this 

 Introduction, condensed as it is, may be instrumental in 

 persuading a larger number of persons to pursue their stud- 

 ies of this very interesting subject for its informational, 

 educational and practical values. 



The writer lays no claim to originality, except it may 

 be in the presentation of the topics. He has had little 

 opportunity for experimentation, but for many years his 

 lot has been cast where breeding experiments have been 

 carried on and important results secured. 



In the new and rapidly expanding field of Genetics 

 where results are being presented to the world by thou- 

 sands of investigators it is extremely probable that many 

 important phases have been overlooked, some misinter- 

 preted, and others left obscure by reason of the condensed 

 treatment. 



The writer is under deep obligation to many friends 

 who have had an opportunity of reading the manuscript 

 for their criticism. 



Macdonald College, W. LOCHHEAD. 



August, 1920. 



