626 MUJilEL ROBERTSON AND E. A. MlN(;iIIN. 



to say, the fiag-elluin may disappear completely before the 

 Llepharoplast divides or may persist until after this has 

 taken place. In either case the two daughter-blepharoplasts 

 migi-ate inwards and place themselves on opposite sides of the 

 nucleus in order to become, as will be seen, the two centro- 

 somes in the mitosis. If the flagellum persists during this 

 process of events it remains attached to one of the two 

 blepharoplasts (figs. <> and lU), and becomes drawn into the 

 body of the cell, as seen in figs. 7-9; in each of these 

 three specimens the flagellum, though greatly shortened, is 

 still persistent, and can be seen passing into the body of the 

 collar-cell and terminating in one of the two blepharoplasts, 

 Avhile the other blepharoplast can be seen on the other side of 

 the nucleus quite independent of the flagellurn. On the other 

 hand, figs. 5, 11, and 12 show the two blepharoplasts very 

 close together at tiie apex of the cell and apparently very 

 recently separated from one another, with no tiace of a 

 flagellum. 



The exact method in which the flagellum disappears is 

 difficult to determine simply by comparison of different stages 

 in sections ; it could only be made out satisfactorily by 

 watching the process in the living cell. In collar-cells in 

 which the upward migration of the nucleus is taking place, 

 the flagellum almost always appears much shorter than in 

 the surrounding cells, an appearance too constant in occur- 

 rence to be explained simply as due to artificial curtailment 

 of the flagellum iu the process of section-cutting, especially 

 when the collar is intact and the flagellum does not project 

 beyond it (figs. 9 and 10). But a remarkable feature of 

 this stage is the frequent occurrence of a protoplasmic 

 pi'ojection, like a small pseudopodium, from the apex of the 

 cell round the base of the flagellum (figs. 7, 9, 39, 40) ; this 

 process persists for a time after the flagellum has completely 

 disappeared (figs. 14, 41). The appearances suggest that 

 the cell throws out a pseudopodial process, by the help of 

 which the flagellum is retracted and absorbed at its base ; 



