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The Genus Leucocytozoon 
discovery by Bentley of the leucocytic parasite of dogs similar parasites 
have been described from the rat, mouse, cat, palm-squirrel and hare and 
for these the name Leucocytozoon has generally been employed, in spite 
of the fact that it has been constantly pointed out by Mesnil, Sambon 
and others that this name strictly belongs to the totally distinct parasite 
of birds. 
Patton who has described several of these leucocytic parasites of 
mammals employs for them the generic name Leucocytozoon. Neither 
he nor James regards the leucocytic parasite of mammals as allied to 
the Leucocytozoon of birds. As James incorrectly justifies his use of 
the generic name Leucocytozoon for the dog-parasite by pointing out the 
doubt existing as to the true nature of the host-cell of the bird-parasite 
so Patton considers he is also justified in so doing, and he agrees with 
Laveran in considering the bird’s parasites as belonging to the genus 
Haemamoeba, a genus in which Laveran includes the pigmented 
malarial parasites and their allies. It is evident that Patton thinks 
this would liberate the name Leucocytozoon from the bird-parasite. 
This is quite out of accord with the rules of nomenclature. Even if 
Laveran and Patton who follows him are correct in their view the 
name Leucocytozoon would remain as a synonym of the bird-parasite 
and could not be employed for any other form. As we shall see below 
the view that the Leucocytozoon of birds is really of the same genus as 
the pigmented parasites of malaria cannot be accepted. 
Quite recently in Science Progress Miss Porter has reviewed our 
knowledge of the Leucocytozoa. She has attempted, as no one has 
done hitherto, to describe under this one name both the parasites of 
birds and the totally distinct parasite of mammals, with what success 
those who read the review will see. Such a grouping, it must be 
evident to anyone who has studied and compared both these parasites, 
can lead to nothing but confusion. Towards the close of her paper 
Miss Porter makes this statement “the name Leucocytozoa should be 
retained for all protozoal parasites of the leucocytes of vertebrates ” in 
spite of the fact that the leucocytes of mammals are known to harbour 
several totally distinct parasites 1 . It is evident that Miss Porter has 
1 The following parasites have been described from the leucocytes of mammals :— 
1. Leishman-Donovan bodies. 
2. The haemogregarines of dog, cat, rat, etc. 
3. The Toxoplasma gondii of Nicolle and Marceaux. 
4. A similar parasite described by A. Splendvie from the rabbit. 
5. The curious trypanosome described by Cruz in Brazil. 
6. The parasite of equine lymphangitis described by Doucloux. 
