162 
E. A. MINCHIN AND H. M. WOODCOCK. 
using an oil-immersion lens. Such an infection was present 
in owl 19. And in owl 23 nearly every red blood-corpuscle 
is infected; very few uninfected red cells can be found in 
the permanent preparations ; there are nearly always two or 
three parasites in a single host-cell, and frequently their 
number is four to six, when they are mostly small or quite 
minute forms. 
No pronounced variation in the number of the Halteridial 
parasites present on different occasions of examination was 
observed, contrary to what was so markedly the case in 
Leucocy tozoon. It was observed several times, however, 
that there was distinct, often considerable variation in the 
number of individuals which were ripe enough to flagellate or 
become rounded off. Thus, at some examinations, by the 
time a drop of pure blood could be mounted and put under 
the microscope numerous male gametocytes would be seen 
actively liberating free microgametes, rounded-off female 
forms also of course being present ; at other times scarcely 
any such, or none at all, would be found. Another noticeable 
point of difference from Leu cocy tozoon was that not only 
adult or nearly adult individuals, but also young or small 
forms and forms of intermediate size, were nearly always 
present at the same time in the blood. 1 
On the whole, comparing the results of our observations 
on Halteridium and Leucocy tozoon, we think the 
following conclusions are suggested. The schizogonic process 
in the former parasite must be on a considerably larger scale 
than it is in the latter, even if we suppose that there is a 
stronger original infection. 2 Further, it is probable that the 
schizogony in Halteridium may be of longer duration, i. e. 
that it may continue to go on for a longer period than is the 
case in the Leu cocy tozoon ; this seems to us to be indi- 
1 This agrees with the condition which was found in the case of 
H . f r i n g i 1 1 se , in the cl affinch . 
2 If schizogony in the parasite of the little owl is similar to the 
process described by Aragao (1) in the Halteridium of the pigeon, 
it is indeed on a lavish scale. 
