OX THE TRYPANOSOME OF THE LITTLE OWL. 
149 
On the other hand, in the summer, for instance in owl 
23, the trypanosomes certainly occurred in the general circu- 
lation. They were seen for the first time in blood taken from 
the living bird on June 15th— 16th, in the night-time, after 
being five months at Rovigno ! This fact is mentioned just by 
way of illustrating the difficulties attending the path of the 
would-be researcher on these Avian parasites. The trypano- 
somes were found also in subsequent examination of the 
bird; and in permanent preparations made they are not in- 
frequent, averaging four to six on a good-sized film. Even 
at this time, however, the parasites are somewhat more 
numerous in the bone-marrow, as we have learnt from our 
preparations made after the death of this bird (which took 
place on June 29tli), while they appear to be extremely 
scanty in the smears made from the internal organs (lung, 
spleen, etc.). 
Living Observations on the Parasites. 
With a view of ascertaining whether we could find anything 
which pointed to the actual passage or transformation of the 
trypanosomes into Halteridia or Leucocytozoa, or vice-versa, 
careful living observations were made on several occasions, 
usually in the night-time. 
a. Trypanosomes. — The following notes were made at 
the time of the examination of the bone-marrow of owl 8 
after its death (February 26th, 1909), in which, of all our 
infected birds, trypanosomes were most numerous to this 
situation. The parasites observed were of three distinct 
kinds : (1) Slender, active forms, of medium size, with a finely 
drawn-out aflagellar extremity. In two instances such forms 
were seen attached by this end to a cell of leucocytic 
character; the trypanosomes were lashing about in every 
citrate added. Our tubes were, therefore, not very satisfactory ; but 
we were not prepared for the entire failure of the trypanosomes to 
appear in them, considering the readiness of these Avian parasites, as 
a rule, to develop in cultures. 
