12 The N.Z. Journal op Science and Technology. [Feb. 
erythrocytes containing adult parasites often showed an increase in breadth. 
The percentage of erythrocytes infected with plasmodia varied consider¬ 
ably : in some birds only three or four parasites were detected in a film, 
whilst in others as many as 20 per cent, of the erythrocytes harboured 
parasites. Three per cent, of the blackbirds from this district were infected 
with this parasite. 
Description of Six Successive Parasites. —(1.) Spherical in form ; measures 
4‘8 /x in diameter ; protoplasm deep blue ; nucleus composed of two fine 
purple strands, central in position ; one small mass of melanin towards 
one end. 
(2.) Spherical in form; measures 4°6/x in diameter; protoplasm pale 
blue ; nucleus appears as a small faintly stained purple granule situated 
at one end ; four compact granules of 
melanin opposite nucleus. 
(3.) Oval in form; measures 6'4 /x 
by 4‘8 /x ; protoplasm pale blue ; nucleus 
appears as a fine purple strand at one 
end ; six granules of melanin towards 
centre. 
(4.) Oval in form ; measures 8 /x by 
4*8 /x ; protoplasm deep blue ; nucleus 
unstained; seven granules of melanin, 
scattered. 
(5.) Spherical in form ; measures 3*2 /x 
in diameter; protoplasm pale blue ; 
nucleus unstained; four granules of 
melanin, central in position. 
(6.) Oval in form ; measures 6’4 /x by 3‘2 /x ; protoplasm pale blue ; 
nucleus appears as faintly stained purple granule situated towards one end ; 
five granules of melanin, scattered. 
The nuclei of the host cells were all displaced by the above parasites. 
Halteridium and plasmodium have been observed in both the thrush 
and blackbird. The foregoing observations were made on birds showing 
a pure infection, thus eliminating the possibility of confusing the various 
stages present in a double infection. The birds the victims of these para¬ 
sites were descendants of those imported about 1870. Many hundreds 
of native birds from various districts will be required to be examined 
for these parasites before deciding that these birds are free from infection. 
The possibility of the imported birds infected with halteridia transmitting 
these parasites to native birds must be borne in mind. 
Labbe considered the halteridia of different birds to be all one species, 
but other observers working on these parasites, noticing differences in 
regard to form, structure, and appearance, distinguished many species 
and named them after the birds in ^jhich they were found. Possibly a 
given species of halteridia might infect numerous species of birds. If the 
halteridia of birds belong to only one species, then infection of native birds 
should occur if the intermediate host were present. But, on the other hand, 
if the species of halteridia were restricted to one or numerous closely related 
species of birds, infection would probably be observed only if the imported 
birds were closely related to the native birds. 
In Australia several blood-parasites have been described in native birds 
during the past few years, and over thirty species showed infection by 
halteridia. 
Fig. 2. —- Plasmodium of the thrush. 
a, Multiple infection of erythrocyte 
by young forms ; b, formation of 
merozoites ; c, erythrocyte contain¬ 
ing two adult forms. 
