NOTES ON SPOROZOA IV. 
229 
ill figs. 33-35) ; at all events so Far as large or adult individuals 
are concerned. That tliis is really the case is borne out by a 
fact which I noticed several times, namely, that only a certain 
proportion of the larger female forms of H alter i di um (more, 
I should say, in H. fringillm, fewer in H. nootum) show 
this characteristic additional element, in Giemsa-stained pre- 
parations ; whereas practically all the female individuals of 
Leucocy tozoon zieinanni exhibit it. We arrive, there- 
fore, at the important result that when the female nucleus of 
Leucocy tozoon is compared with that of Halteridium 
in the same phase, the two are found to be of essentially tlie 
same type of structure. Their apparent dissimilarity, as 
frequently observed, is due to the fact that in Halteridium 
the karyosome retains its central position within the nucleus 
throughout the period of growth of the garaetocyte, and does 
not pass to the outside until the parasite is full-grown. On the 
other hand, in Leucocy tozoon the karyosome appears to be 
always at the edge of, or else outside the nucleus, even in 
young or intermediate-sized individuals ; I have never seen 
it within the central nuclear mass. This expulsion of the 
karyosome, which doubtless represents here, as in other 
cases, an elimination of unrequired chromatic material or 
“ nuclear purification,” thus takes place very early in the 
development of the macrogametocyte of Len cocy tozoon, 
but only at a comparatively late stage in that of Halteri- 
d i u m. 
The facts I have observed and described above finally 
settle, in my opinion, the question of the connection of 
Halteridium noctum (and equally, of course, of Leu- 
cocy tozoon zi email ni) with Trypanosoma uoctuiB. It 
appears to me that these parasites have no direct connection 
whatever, either ontogenetic or phylogenetic. As readers of 
my first study on avian parasites (loc. cit.) will be aware, I 
felt then compelled to relinquish the view that Halteridium 
and Trypanosoma were phases of one life-cycle, though I 
still considered that Halteridium was to be derived from 
a Trypanosome-like parasite, which had become permanently 
