PREFACE 



IT is inevitable that each work planned as a member of 

 a series of biological monographs should be somewhat 

 technical. Of necessity each must be concise. In view of 

 the difficulties these limitations involve, one may hardly 

 expect to escape the criticism that the subject matter 

 often tends to be esoteric in its nature, for few can say in 

 Shaw's odd fancy, "I tried to do too much and did it." 

 Nevertheless, there has been a serious effort to avoid' a 

 mere record of the development of a specific problem in 

 Genetics as an aid to the general biologist. No one could 

 have a professional interest in a subject of this kind with- 

 out the desire that there be some practical application 

 of the results to agriculture and to the many phases of 

 sociology where a knowledge of the laws of heredity is a 

 first requisite. Though such applications of the genetic 

 conclusions are touched but lightly here, there is the hope 

 that the non-biological worker interested in problems of 

 human welfare will find some new thoughts and pertinent 

 suggestions in the compelling logic of the controlled 

 experiments described throughout the pages. At least 

 it was with this idea in mind that the authors prepared 

 the first four chapters. For the zoologist and botanist 

 the well-known facts and elementary principles there dis- 

 cussed would have been unnecessary. 



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