C. M. Wenyon 
65 
no knowledge of the Leucocytozoon of birds for her survey of the group is 
inaccurate and contradictory. With reference to the bird-parasites it is 
stated “Avian Leucocytozoa are said to exhibit sexual characters but 
this is somewhat doubtful” though earlier in the paper male and female 
forms are described. As a matter of fact the presence of both male and 
female forms in the peripheral circulation is one of the chief charac¬ 
teristics of the Leucocytozoon of birds. In this respect it agrees with 
the pigmented Halteridium. Again at the beginning of the paper 
Danilewsky’s records are completely misinterpreted. In writing of the 
bird-parasites Danilewsky mentions having observed two forms of 
Polymitus in birds’ blood, one of ordinary size and with grains of 
melanin, the other without grains of melanin but of very large 
dimensions. In a later publication he says he has found that the 
“leucocytozoaire ” is only an intracellular stage in the development of 
the large Polymitus but he goes on to say that not all the “leucocyto- 
zoaires” develop into Polymitus. This is exactly what is known to occur 
and speaks for the accuracy of observation of this investigator. The 
Leucocytozoon of birds exhibits marked sexual characters. The male 
gametocyte gives rise to male gametes in much the same manner as the 
male forms of the malarial parasites while the female forms become 
rounded preparatory to fertilization by the male gamete. We thus find 
that Danilewsky was quite correct in his observation that only some of 
the “leucocytozoaire ” develop into Polymitus. In view of these facts 
it is unfortunate that Miss Porter should state that “ It is now known 
that the Leucocytozoa and the Polymitus of malaria have no connection.” 
It is evident that Miss Porter has not read Danilewsky’s papers with 
sufficient care. 
For the sake of clearness I will give the characters of Leuco¬ 
cytozoon :— 
1. They are exclusively parasites of birds for though Carini has 
described a Leucocytozoon from an amphibian it is exceedingly doubtful 
if this is a Leucocytozoon as it does not exhibit the sexual dimorphism 
which is such a distinctive characteristic of the avian parasites. 
2. They are parasitic in cells which have been variously interpreted 
as leucocytes, red blood corpuscles, immature red blood corpuscles, etc. 
3. They have the peculiar property of causing the host-cell to 
assume a characteristic spindle form 1 . The parasites themselves sur- 
1 Miss Porter quotes me as admitting that sometimes the host-cell may have a spindle 
shape. If she will refer to my article she will see that I carefully state that there is practi¬ 
cally always a spindle shape. 
Parasitology in 
5 
