469 
in a corpuscle, stages can be found showing clearly that as they grow 
and elongate in the direction of the length of the corpuscle, the two in- 
dividuals may come into contact (cf. figs. 15 and 16). 
It is this feature in regard to which this particular infection of a 
little owl has an important bearing on the case of the chaffinch-infection 
under consideration. If fig. 17 is compared with figs. 5 and 6, it will be 
realized, I think, that the same explanation will apply equally to both 
cases. If different stages in the relation of two individuals in one cor- 
puscle to each other (such as are drawn in figs. 15 and 16) had been met 
with alone, it might have been more difficult to decide in which order 
the series should be taken; but when in the same smear and within a few 
Fig. 15. Fig. 16. Fig. 17. Fig. 18. 
Figs. 15—22. Halteridium (Haemoproteus) noctuae, from the blood of a little owl, 
showing different stages in the growth and cytoplasmic fusion of two or more indivi- 
duals in a single corpuscle. In the case of these small forms, and particularly where 
there are three or more parasites in one cell, it is difficult to distinguish whether 
they are male or female. X 2000. 
fields all manner of plasmodial appearances are seen, the result of 3, 4 
or more individuals being crowded in a single corpuscle, one is quite 
unable to regard the process in the former case as binary fission. All 
things considered, therefore, we must conclude that figs. 1—8 of the 
condition seen in the chaffinch represent a double infection of a cor- 
puscle, just as it is almost certain that figs. 11, 16 and17 represent a 
similar condition. 
The interesting and peculiar features about this case, and the rea- 
sons which made me hesitate at first as to its true meaning, are these: 
In the chaffinch in question, the infection is not, comparatively speaking, 
