128 
MURIEL ROBERTSON. 
tions. They adopt a dumpy spiral shape, or the posterior end 
may become much thickened at the expense of the rest of the 
body (text-figs. 2 and 3). Sometimes the most fantastic shapes 
are seen, finally the flagellum breaks free but may remain 
attached to the Trypanosome by its posterior end. It may 
then become tangled round the body and stick out iu stiff 
loops. The Trypanosomes in these phases on the sealed slide 
made from the skate’s blood are absolutely identical in appear- 
ance with the motile forms described in leech 5a (cf. text- 
fig. 1). The time at which the Trypanosomes come to rest 
varies much. 
On another occasion a rounded non-motile Trypanosome 
which had discarded its flagellum was chosen for continuous 
observation on a slide of skate’s blood which had been 
mounted for fourteen hours. The animal was seen to divide 
into two about 11 o’clock in the forenoon. During the after- 
noon, at about 4 o’clock, these two individuals each divided 
thus forming four little rounded animals lying more or less in 
contact. By 7 the same evening they had become more oval 
and were identical in appearance with the resting phases in 
the leech. By 9.30 p.m. short pi'ojectious were seen at 
the broad end of two out of the four creatures under obser- 
vation. The slide was left about 10 o’clock that night 
as the animals wei’e not motile. Next morning at 9.30 
— thirty-six hours after mounting the slide, observation was 
a'min resumed and it was found that the creatures had each 
divided. The eight resulting individuals wei'e still closely 
apposed but not connected with each other. Unfortunately 
these creatures were lost owing to a careless movement. The 
slide was, however, iu the following condition. Unaltered 
'rrypanosomes, still actively moving, were to be seen, non- 
motile groups of four and also a few groups of six and eight 
individuals Avere present. 
I had often noticed that the Trypanosomes on a sealed slide 
of skate’s blood altered their shape, but, thinking this was 
merely a pathological manifestation, had not persevered with 
the observation. The process is easily enough passed over 
