C. M. Wenyon 
211 
viewed from the blunt end (Text Figures 1 and 2). Within the cyto- 
stome could be made out a flagellum or membrane displaying a constant 
undulatory movement. It was continued for the whole length of the 
cytostome from the insertion of the three flagella to the posterior end. 
Fig. 1. Living flagellate viewed towards the blunt end. The lips of the large cytostome 
with the undulating membrane inside are well shown. 
Fig. 2. Appearance of living animal. 
It was very difficult to obtain a clear view of this structure so that some 
doubt exists as to whether this was an undulating membrane or a 
flagellum lying in the groove of the cytostome. If it had been a free 
flagellum it might have been expected that occasionally it would come 
out of the groove and give the flagellate the appearance of having four 
flagella. This was never found to occur nor did any of the appearances 
seen in the stained specimens lend support to this view. It seems safe 
therefore to conclude that the large cytostome had within it an 
undulating membrane. The general characters of the flagellate can be 
seen from Text Figures 1 and 2, which were drawn from life. The largest 
forms seen were about 15 p, long and 7 p. broad. Very much smaller 
forms were also met with and some not more than 3 or 4 /t across the 
longest diameter. The smaller forms were at first considered to be 
distinct organisms hut from the stained specimens this was found not to 
be the case. 
