C. M. Wen YON 
327 
tlie nuclear multiplication in the scliizout of Haemogregarina lutzi. 
This process of division is repeated for each of the daughter nuclei or 
■for only one of them. The nuclei resulting from the second division 
may again divide in a similar manner. There results a schizont filled 
with refractile sphei’es (Text-fig. 7) and having nuclei varying in number 
according to the exact progress of the nuclear divisions. From this are 
Figs. 4-8. Reproductive cysts of Haemogregarina canis in the spleen of the dog, drawn 
from fresh material. 
Figs. 4 and 6. Cyst containing merozoites and residual body drawn from fresh spleen 
material. 
Fig. 5. Cyst containing one merozoite and residual body. 
Fig. 7. Cyst containing schizont with protoplasm filled with refractile spheres. 
Fig. 8. Cyst containing sexual forms with large residual body. 
separated off large sausage-shaped merozoites having a fine reticular 
protoplasm while the refractile spheres are left behind in a large residual 
body. The number of merozoites correspond to the number of nuclei. 
In some cysts only a single merozoite is present (Text-fig. 5) with a 
large residual body. Here increase in size of the schizont can only have 
taken place without any nuclear multiplication, or only one of the 
nuclei resulting from the multiplication has given rise to a merozoite. 
Very commonly there are three merozoites but there may be four or 
twice this number (Text-figs. 4 and 6). The merozoites are about 15 /a 
in length. The nucleus varies in appeai’ance with the extent of extrac¬ 
tion of the stain. When fully extracted there is seen to be a nuclear 
membrane over which are arranged fine deeply staining granules. At 
the centre of the nucleus is a karyosome (PI. XVI, figs. 3 and 6). I have 
not been able to decide whether the merozoites are able to again pass 
through a similar process of schizogony or whether each one passes on 
to the production of the sexual forms. I think the latter is more 
probably correct. If the asexual cycle could be repeated indefinitely, 
the infection of the dog would be much lai’ger than it ever is. The dogs 
ai’e covered with ticks and these ticks are constantly infected with the 
