STUDIES IN THE LIFE-HISTORY OF EUGLENA. 337 



In Euglena agilis, the origin of the motor apparatus can be 

 traced to the budding off of the kinetic complex from the endo- 

 some during the early prophase. As a rule, the new flagella do 

 not begin to grow until the nucleus has migrated anteriorly to 

 the lower border of the reservoir, and the blepharoplasts have 

 been produced from the kinetic mass. In a few cases what 

 appear to be the new flagella have been observed previous to this 

 time. The growth of both branches of each new flagellum 

 progresses rapidly and by the time the body begins to separate 

 into two daughter animals the main branch at least, has pene- 

 trated to the exterior. 



It has been impossible to trace the origin of the lens shaped 

 thickening on the main branch of the flagellum. It seems to 

 arise gradually from the blepharoplast while the latter remains in 

 connection with the kinetic mass on the nuclear membrane. 

 When first observed during the quiescent period after division, it 

 appears as a thick fiber extending toward the blepharoplast. 

 Later it seems to condense at about the region of the stigma, 

 increasing in size as the reorganization process is completed. 



The significance of this thickening has not been determined. 

 It appears to have no connection with the mitotic phenomena, 

 but disappears and a new one is reconstructed with each division. 

 Its association with the stigma suggests that it functions in some 

 way as a sensitive area to perhaps both heat and light. It 

 perhaps initiates the motor reflex in Euglena as described by 

 Mast, Jennings, Bancroft and others. Steuer describes a similar 

 thickening on both the flagella of Eutreptia, in approximately the 

 same position with relation to the stigma. This may represent 

 a mere duplication of the structure as found in Euglena and serve 

 the same function for the two flagella, the one directed anteriorly 

 and the other posteriorly. 



DISCUSSION. 



The importance of the flagellates as objects of study has long 

 been recognized by students of the Protozoa. Biitschli (1878), 

 Klebs (1883), Fisch (1883), and many other earlier workers did 

 much to stimulate such research. The Euglenoid nucleus has 

 proved to be a very favorable object for study of nuclear phe- 



