VI INHKKITAM K. IT. UTILITY, AND SEX IN PIGEONS. 



ills which thus strongly impel to so radical a change in opinion concerning 

 the liases of hereditary phenomena will undoubtedly be subjected to the stoutest 

 opposition; the more so, inasmuch as admittedly these studies were not as complete 

 as i heir author had wished to make them. But it is believed that a full examination 

 of the data of the volume will go very far toward demonstrating that Whitman 

 found material and methods for shifting, changing, or reversing the developmental 

 and hereditary capacities of the germ-cells. The materials of Volume I, which treat 

 evolution as an orthogenetic process, afford also something more than full and 

 complete harmony with this result. 



To the general statement of the previous volume concerning a lack of full 

 treatment in these works of the pertinent literature a word should be added here. 

 It is in the present volume that this lack of adequate treatment of contemporary 

 lit erat ure will be found most evident. There are three facts to be noted in expla- 

 nation: (1) the materials of this volume were in a less advanced state of prepara- 

 tion than were those of the companion volumes; (2) the rather plentiful abstracts 

 and notes of current literature which came into the editor's hands were in such 

 form as to raise a question as to their utility, particularly since the main purpose 

 here has necessarily been to present the author's data and conclusions; (3) much of 

 the important work upon the general subject treated here has appeared during 

 the rather long period required for the preparation of these works for publication. 



1 1 would be unfair to the author to omit the further record that to him is cer- 

 tainly due the entire credit of having first demonstrated a "shifting of dominance" 

 series. His colleagues, in Chicago at least, were, during several years, quite well 

 aware of his results. 



In the preface to Volume I we make specific acknowledgments to those whose 

 assistance, sacrifices, interest, and generosity have made possible the preparation 

 and publication of this work. 



OSCAR RIDDLE. 



STATION FOR EXPERIMENTAL EVOLUTION, 



Cold Spring Harbor, New York, June 1915. 



