ON THE TRYPANOSOME OF THE LITTLE OWL. 
157 
The only other explanation of our observations — on owl 11, 
for instance — would be that the great majority of the 
numerous gametocytes observed on March 19th-20th had 
died off by the 23rd, and that those seen again on March 
23rd-24th were an entirely fresh lot, which had been very 
rapidly developed as the result of a quite recent schizogouy. 
In the first place it is most unlikely that the gametocytes 
would die off in such numbers as soon as, or even before, they 
were quite ripe, especially at the beginning of the season — 
such a course would be very expensive and most unusual for 
a parasite. Secondly, if schizogony had been going on 
recently to produce the numerous forms seen in the blood 
March 23rd-24th, and again, subsequently, to give rise 
to those present on March 30th, we should certainly have 
expected a proportion of these forms to be small to inter- 
mediate in size, which is not the case ; and, moreover, we 
ought undoubtedly to have found some indications of the 
actual schizogonic process in our permanent preparations of 
the internal organs made on April 3rd, when the bird died. 
As a matter of fact in all our infected owls the schizogonic 
process seemed to be over and done with ; altogether we have 
only come across extremely few really small (young) gameto- 
cytes. Hence, the first explanation we have offered appears 
by far the most reasonable. 
It is interesting now to compare with our experiences those 
of Mathis and Leger in the case of the species parasitic in 
Tonkin fowls already alluded to. It is important to note 
that the periodicity described (occurrence for some days, 
alternating with apparently complete disappearance for a 
period of two or three weeks or more) was observed only in 
L. caulleryi; in L. sabrazesi from the same bird, which 
was made a distinct species on account of the gametocytes 
always having the spindle-like shape, this disappearance was 
not found. In a previous memoir ( 18 ) it has been remarked 
by one of us that those two species are most probably 
only different phases of one and the same parasite. The 
L. sabrazesi phase probably corresponds in a general way 
