468 
Hence it seems to me most probable that the same explanation 
holds throughout. Of course, where both nuclei are either of male 
(fig. 7) or else of female character (fig. 6), there is not the same ready 
means of settling the question as in the above instances. A point which 
in my opinion also weighs considerably in favour of the view that two 
individuals are concerned is this. Binary fission of adult or nearly 
adult sexually differentiated gametocytes (of either sex), to give rise to 
two intermediate-sized individuals is a phenomenon that has been hi- 
therto quite unknown among Haemosporidia (with one exception, to be 
mentioned shortly); indeed, I am not aware of anything exactly com- 
parable to such a feature among the Protozoa. 
On the other hand, in an ordinary infection (not including i in this 
category an extraor dinanily strong one like that discussed immediately), 
whenever I have observed a red blood-corpuscle invaded by two Halte- 
ridial parasites, these have been generally situated either on opposite 
sides of the host-cell nucleus, or else obliquely, towards the opposite 
ends. I have only rarely noticed instances where two (and only two) 
young individuals lie on the same side of the cell-nucleus, and fairly 
close together. i 
I may refer here, however, to a case which I observed while at 
Rovigno, of an extremely heavy infection of a little owl (Athene noctua) 
with Halteridium (Haemoproteus) noctuae, which is most instructive in 
this connection. In the bird in question, nearly every red corpuscle is 
infected with the parasites; and in general there are two, three or more 
individuals — sometimes as many as 6 or 7 small ones? — in one cor- 
puscle (cf. figs. 15, 18, 19, 21). In this case it is not at all difficult to 
find corpuscles containing a cytoplasmic mass which possesses three or 
four nuclei (fig. 20). Such a condition is the result, I am certain, of 
the fusion of the cytoplasm of three or four parasites as they have grown 
in size and come into contactwith each other, thus forming akind ofplas- 
modium (figs. 18—22), which may be indefinite or irregular in form. I 
cannot consider that such stages should be interpreted in the opposite 
sense, 1. e. as indicative of a schizogonic multiplication. For one thing, 
the growing plasmodial body contains numerous pigment grains;the young 
separate individuals in a cell possess little or no pigment. And in spite 
of the abundance of the material I have not found anything to suggest 
that such a multinucleate parasite divides up into, or gives off, small 
uninucleate portions, leaving behind a cytoplasmic residuum containing 
the pigment. Further, even when there happen to be only two parasites 
3 A similar instance of a multiple infection of a red blood-corpuscle with small 
Halteridial parasites is figured by Aragao. Arch. Protistenk. 12. 1909. pl. 3, fig. 24. 
