No. 3-] BIOLOGY OF THE STENTORS. 551 



to indicate that the plane of fission is determined before the 

 slightest sign of bipartition is visible, and that the plane is not 

 altered, nor division prevented by the removal of part of the 

 cytosome. 



In closing, I would express my sincere thanks to my former 

 instructor, Prof. E. L. Mark, of Harvard, for many favors and 

 valuable suggestions ; and to my present instructor. Prof. C. 

 O. Whitman, through whose courtesy it was my privilege to 

 occupy, during the summer of 1 891, an investigator's room in 

 the Marine Biological Laboratory at Wood's Holl. I would 

 also acknowledge my indebtedness to Prof. S. F. Clarke, of 

 Williams College, and to Mr. W. S. Nickerson, of Harvard, for 

 sending me material. 



Morphological Laboratory, 



University of Chicago, April, 1893. 



