Observations on the Life-Cycle of Helkesimastix faecicola. 359 



movements of certain trypanosomes. Yet, in spite of all this activity, 

 the rate of progression is no greater than is obtained by the quiet surface 

 gliding. 



One other variety of movement — not of progression — remains to be noted. 

 An individual which has been gliding about will become anchored by the end 

 of its flagellum to some particle of debris or small clump of bacteria. The 

 body will then execute sharp bending or knicking movements about its 

 narrow, posterior end, where the flagellum becomes free, often turning 

 through nearly 180°, and then turning back again. This anchoring process 

 recalls the anchoring of some Bodos by the trailing flagellum, but the 

 body movement in Helkesimastix is not at all of the vibrating or dancing 

 character seen in the Boclo, because it lacks the anterior, vibratile 

 flagellum. 



Multiplication. — After the flagellates have been active for some hours 

 multiplication begins. We have not observed it occurring up to six hours 

 after excystation has taken place, but by the end of 20 hours it was 

 proceeding actively and had evidently been going on for some time. An 

 individual about to undergo division always comes to rest in the first place. 

 The body becomes ovoid and then practically spherical (figs. 22, 24, 27). 

 The subsequent course of events is not always quite uniform, though the 

 variations are only slight. In the great majority of cases, by the time 

 the body-form has become rounded, or even after it has been ovoid 

 for a short while, the flagellum is no longer visible. The free part has 

 entirely disappeared, and we are strongly inclined to think that the attached 

 part also goes, though we cannot write with absolute certainty because it 

 is extremely difficult to detect a motionless flagellum lying over, and 

 closely applied to, the body. However, we think that, in many cases, it is 

 probably entirely withdrawn and absorbed, especially as, just prior to this 

 stage, small " working " movements of the peripheral protoplasm occur at the 

 side where the flagellum lay. At this stage the clear nuclear area can 

 frequently be seen to be elongated and to possess now two karyosomatic 

 bodies (fig. 22), the parent-karyosome having already divided. Next, the 

 body begins to elongate again (figs. 23, 29), and in a minute or two more 

 becomes slightly dumb-bell shaped (fig. 25). The two daughter-nuclei are 

 practically reconstituted and have begun to separate by this time (figs. 23, 

 29) ; they can usually be seen because the body remains motionless during 

 this period. (We hope to give information with regard to the cytological 

 details both of multiplication and conjugation in a subsequent memoir, 

 when we have studied fixed and stained preparations). The time of 

 appearance of the first new (daughter) flagellum varies somewhat. As a 



