Viii PREFACE 



many years, embodied in his masterly treatise upon this group 

 of organisms, will remain the standard for years to come. My own 

 obligation is manifested by the repeated references in these pages. 

 In common with other students of the group I am also indebted to 

 Professors R. Hertwig, Maupas, Klebs, Labbe, Verworn, Schaudinn, 

 Siedlecki, and a host of others whose labors have thrown so much 

 light upon the problems connected with the Protozoa. I regret that 

 I could not make use of Professor Lang's valuable addition to the 

 literature of the Protozoa, as it appeared after the present volume 

 had gone to press. 



, Many of the above investigators have given admirable figures of 

 the Protozoa which I have freely used, in addition to numerous 

 original drawings, in illustrating the present work. The majority 

 of the figures copied from other works have been made by my wife, 

 whose skilful penwork and unfailing help in preparing the manu- 

 script have been of the greatest assistance. 



In conclusion I wish to express my deep obligation to Professor 

 Henry F. Osborn for many valuable suggestions and for his gener- 

 ous assistance which has made the present volume possible. To Pro- 

 fessor Edmund B. Wilson finally, to whom I take the greatest pleasure 

 in dedicating this book, I owe a debt of gratitude not easily ex- 

 pressed. I wish to thank him, amongst many other things, for the 

 use of the electrotypes of several figures, for the generous interest 

 and friendly advice throughout, and, above all, for his invaluable 

 criticisms and suggestions based upon the careful reading of my 

 manuscript. 



G. N. C 



COLUMBIA UNIVERSITY, NEW YORK, 

 May, 1901. 



