40 
Blood Parasites 
seen. Very usually an extremely fine line, not easily seen, extends from 
the nucleus across the centre to the other side of the organism, whilst 
at other times a strand of nuclear chromatin, much thicker than the 
above mentioned line, extends J to the distance across the body. 
Distinct pear-shaped parasites were extremely rare, but one example 
was seen in which the narrow end was drawn out to a fine point. A 
few examples of dividing parasites were met with, shaped somewhat 
like a loat of bread, but these were round or oval and not at all pear- 
shaped. Usually the dividing forms appeared like a loaf of bread or 
figure 8, or in some instances like a trefoil leaf. 
Irregular or amoeboid forms were very infrequent. One of these 
showed a fine line extending from the nucleus into the protoplasm of 
the red cell and terminating in a deeply stained red dot. In no case 
did I meet with two parasites in one red cell. No definite free parasite 
was seen, but I can quite imagine that these minute structures might 
easily be overlooked. 
The average diameter of the red corpuscle in the field mouse is 
about G yu., and the small parasites measure about 1/r by 2’3 ya, some 
probably less. The average size of the commonest parasite, which is 
round or oval, is rather less than 3 /r. 
'The red corpuscles in which the parasites are situated show no 
appreciable alteration in size or staining reaction and the parasites 
have no pigment. 
As I thought these unpigmented ring-like parasites might represent 
the early stage of a larger intracorpuscular haemamoeba, very careful 
search was made for such but with entirely negative results. 
It would seem therefore as if these intracorpuscular parasites belong 
to the piroplasms used in its fullest sense. 
Recently I find that Fran 9 a (1912) has described somewhat similar 
pai'asites in Microtus incertus which he has named Smithia microti, but 
unfortunately I have been unable to see his original article. If the 
parasite found in the field mouse be a new species I should rather 
incline to the opinion that it belongs to the Nuttallia and would 
suggest the name Nuttallia muris sp. n. 
Piroplasms in the Water Vole—Nuttallia microti sp. n. ? 
I found in the blood of a water vole, Microtus amphibms, caught in 
this neighbourhood, April 15, 1912 (but not in the same district as 
the field mouse), similar unpigmented intracorpuscular bodies closely 
resembling those of the field mouse. 
