C. M. Wen yon 
69 
The group Leucocytozoon of birds is a homogeneous one, the indi¬ 
vidual members of which show only slight variation so much so that it 
is exceedingly difficult to separate the species. There is no possibility 
of confusing any Leucocytozoon with the pigmented parasites with which 
Patton would group them so that the inclusion of such distinct forms in 
a single genus seems quite unnecessary. On the same line of argument 
one would be compelled to do away with all generic distinction in the 
Haemosporidia and to establish a single genus for the whole heterogen¬ 
eous assemblage. It is certain that some of the Piroplasmata could be 
more easily confused with the malarial parasites than an avian Leuco¬ 
cytozoon should escape recognition. However it is to no purpose to 
pursue the argument further as Patton states that he prefers to consider 
the avian parasites as Haemamoebae. We find however that when 
Patton comes to consider the leucocytic parasite of the palm-squirrel 
though it “agrees in every detail with the haemogregarines ” it is placed 
in a separate genus. I do not think even Patton would maintain that 
the Leucocytozoon of birds agrees in every detail with the parasites of 
malaria 1 . 
The most complete account of the development of a haemogregarine 
is that of the late Dr Miller of the parasite which he found in the 
leucocytes of rats. He seems to have been singularly fortunate in 
having at his disposal an unlimited amount of material. As a result of 
his researches he was able to follow the complete cycle of this parasite 
both in the rat and in the intermediate host —Letups echidninus. Now 
it occurred to him that the life cycle of this parasite of the rat would 
most probably be found to be very different from that of the type 
species of haemogregarine namely Haemogreyarina minima of the frog, 
1 In the ease of the Leishman-Donovan bodies and the allied parasites, Patton has 
suggested that the generic name should be Herpetomonas and that the name Leishmania is 
to be abandoned. The evidence in support of this action is that certain Herpetomonas of the 
intestinal tract of non-biting arthropods exhibit stages in their development which are indis¬ 
tinguishable from the Leishman-Donovan bodies. There is no question of thi s Herpetomonas 
passing any part of its life-history in different hosts. The infection of an arthropod is by 
the accidental ingestion of cysts which have escaped from the intestine of an infected 
individual of the same species. In the case of the Leishman-Donovan body the condition is 
quite different. Part of its life-history is passed like a Herpetomonas in the intestine of 
some biting arthropod (bed-bug) but the other as a parasite within certain cells of a mam¬ 
malian host. In the life-history of the Leishman-Donovan body there is then a definite 
alternation of hosts in one of which it exists as an intracellular parasite. This is a 
profound distinction which undoubtedly justifies its inclusion in a distinct genus. As 
the generic title of the Leishman-Donovan body and its allies the name Leishmania may 
well remain. 
