322 WOOLFORD B. BAKER. 



living organisms, their partaking in many instances of character- 

 istics of both plants and animals, their universal distribution and 

 their contributions to our knowledge of general principles of 

 biological phenomena. Many workers have engaged in such 

 investigation and much progress has been made. 



The present investigation was undertaken on the Euglenoidina 

 because of the primitive character of the organisms composing the 

 group, their wide distribution, their general use as types in 

 fundamental courses in biology and the fact that the literature 

 does not show a complete and critical account of the cycle of any 

 one of them with attention given to all of the organoids of the cell 

 during the successive stages in the cycle. 



Solutions have been sought to four main problems through the 

 study of: 



(1) the origin and behavior of the chromatic elements of the cell; 



(2) the nature and behavior of the endosome of the nucleus; 



(3) the origin and behavior of the locomotor apparatus during 

 mitosis; 



(4) the location of the division center. 



ACKNOWLEDGMENTS . 



The desirability of critical work on Euglena was originally 

 suggested to me by Professor Robert C. Rhodes of Emory Uni- 

 versity in 1919. I desire to express my appreciation to him for 

 much of the earlier criticism and suggestions as well as for the 

 original plan of the work. The investigation was completed 

 under the direction of Professor Gary N. Calkins of Columbia 

 University. I am indebted to him for his suggestive interpre- 

 tations and criticisms, both constructive and destructive, as well 

 as for his continued encouragement and inspiration, beginning at 

 Woods Hole in 1922, continuing at Columbia during 1924-25 and 

 at Woods Hole in the summer of 1925. I am especially in- 

 debted to my wife, Bernice Hall Baker for her painstaking care 

 in the preparation of the figures. 



MATERIAL AND METHODS. 



Several species of Euglena from wild cultures have been col- 

 lected and identified. Attempts have been made to cultivate all 



