124 
MURIEL ROBERTSON. 
and still motile. In othei' cases free flagella still actively 
motile were seen ; this has often enough been observed with 
Trypanosomes, but in this case the flagellum does not take 
the kinetonucleus with it. Uninucleate stages of this parasite 
have never been seen. One of these free motile flagella was 
seen to become secondarily attached to a resting individual. 
This animal was watched for many hours in case the process 
might prove to be of more than merely casual significance, 
but no development took place. Besides these flagellate 
creatures, others were present which had already discarded 
the flagellum (text-fig. 4). These were rounded egg- or 
pear-shaped individuals with a characteristic clearly visible 
nucleus. It is composed of a softly refractile circular body 
surrounded by a bright halo. I'he nucleus lies towards 
the broader end of the body. These animals pi’esent a very 
characteristic appearance, but, nevertheless, are easily over- 
looked in the mass of leucocytes and blood-corpuscles. 
These uou-flagellate organisms were already in a few in- 
stances undergoing division but no sign of the new flagellum 
was as yet forthcoming. 
Another leech (7a) opened forty-eight hours after it began 
to feed showed only resting forms. The blood in the crop 
had coagulated into a rather dry mass but the corpuscles 
showed no signs of degeneration. 
'I’hese resting stages of the Trypanosome are identical in 
appearance with those so frequently seen in Pontobdella 
found infected in nature. A resting pear-shaped individual 
was chosen as a subject for observation at 4.30 p.m. When 
it was first observed ^ the trophonucleus was clearly visible 
and had its usual appearance of a sphere suri’ounded by a 
halo. Half an hour later the animal was more rounded, the 
nucleus was less distinct, and a slight groove had appeared at 
the broad end. By 5.30 the nucleus, as such, had disap- 
peared, but a large clear oval space had appeared in its stead. 
At about 5.50 the two nuclei began to reappear, joined by a 
' I am inclel)ted to Mr. C. H. Mai-tiii for kind assistance in carrying 
out some of these continuous observations uiion the live specimens. 
