OX THE TRYPAXOSOME OF THE LITTLE OWL. 
163 
cated by the fact that in our early owls as well as in our 
later ones quite small forms, which cannot have been long set 
free from the parent schizont, occur as well as others of 
medium size in the red blood-cells; also because the later the 
bird, the greater the number, as a rule, of Halteridia present 
(owls 8, 13, 19 and 23 form a regular series in this respect). 
In the birds in which Halter idium was fairly numerous 
or abundant (Nos. 13, 19 and 23) parasites were seen in the 
living cover-slip preparations which were quite free from a 
blood-corpuscle, although they were not rounded-off or 
flagellating individuals. Only a few of these free Halteridia 
were noticed in owl 13, they were less scanty in No. 19, 
while in No. 23 they were quite common. In the last case 
these free forms varied considerably in size, from small 
individuals up to forms of intermediate size or larg’er. These 
free forms appeared, so far as could be seeu, perfectly 
similar to those in the corpuscles. It is important to note 
that they were quite motionless and were not observed to 
undergo any change. Particular individuals, fairly large 
ones, were watched for two or three hours at intervals, and 
at the end of that period had not altered at all. Not the 
least indication was seen of the development of any of these 
free Halteridia into a trypaniform condition. In the living 
blood from owl 23, examined at night, one or two trypano- 
somes were found; these were distinctly larger than the free 
Halteridia. In spite of much searching, no parasites were 
seen to become actually liberated from the corpuscles. It is 
certain, however, that most, if not all, of these free indi- 
viduals had been parasitic in a red cell, for the great majority 
contain pigment-grains. 
The same state of affairs observed in the living preparations 
from these three owls is found in the permanent smears 
made from them respectively. Here and there in the pre- 
parations from owl 23, where, as already mentioned, several 
parasites often occur in a single corpuscle, three or four free 
individuals are found grouped around or else close to the 
isolated nucleus of a red cell ; in such cases one may assume 
