63 
SOME REMARKS ON THE GENUS 
LEUCOCYTOZOON. 
By C. M. WENYON, B.Sc., M.B., B.S. 
Protozoologist to the London 
School of Tropical Medicine. 
Note. A reply to the criticisms contained in Dr Wenyon’s paper will be 
published by Miss Porter in the next number of “ Parasitology 
A GOOD deal of doubt still exists in many quarters as to the exact 
meaning of the term Leucocytozoon applied to certain Haematozoa. The 
term Leucocytozoaire was first used by Danilewsky in writing of certain 
parasites he had found in the blood of birds. In a later publication he 
uses the term Leucocytozoon for the same parasites though he does not 
employ it as a true generic title. In this latter sense it was first 
employed by Ziemann who named the parasite of an owl Leucocytozoon 
danilewskyi, thus establishing this parasite the type species of the new 
genus Leucocytozoon. It is perhaps hardly necessary to mention that 
Danilewsky and Ziemann both used this name because they considered 
the parasite in question to inhabit a leucocyte of the bird’s blood. 
There has arisen some doubt as to the exact nature of this host-cell. 
Some authorities consider it to be a very much altered red blood 
corpuscle, some perhaps more correctly an immature red blood corpuscle, 
while others adhere to the original view of Danilewsky as to its 
leucocytic nature. It must be clearly borne in miud that the nature of 
the host-cell does not in any way affect the generic name Leucocytozoon. 
If it could be conclusively proved that the host-cell is in every case a 
red blood corpuscle the name Leucocytozoon would still remain as the 
generic title though it would have ceased to be descriptive. 
Apparently it was a want of knowledge on this point that led 
James to apply the name Leucocytozoon to a totally distinct parasite 
which had been found by Bentley in India to attack certain leucocytes 
in the blood of dogs. In his paper describing this leucocytic parasite 
of dogs James discusses the various views as to the nature of the host¬ 
cell of the Leucocytozoon of birds and as he can find no agreement on 
this point he erroneously considers this sufficient ground for removing 
the name Leucocytozoon from the bird-pai’asite and applying it to the 
parasite of the dog which undoubtedly is within a leucocyte. Since the 
