84 
Blood Parasites 
be a very pale red colour. In the haeinogregarines which are pale red 
in colour no nucleus can be detected. 
Very commonly I met with two parasites lying together in a parallel 
way, or with their ends touching, and in these cases one is usually 
stained a deep blue colour, the other a pale blue colour. 
The parasite shows considerable variation in its size but the average 
measurement of 20 specimens gave the following figures; length, 13 to 
13‘5 fjL ; breadth, 4 to 4'5 fx ; the nucleus about 4 p, in both directions. 
I carefully examined several films from these rats but only once did 
I meet with a haemogregarine situated in the protoplasm of a leucocyte. 
In one rat the haeinogregarines were associated with T. lewisi and 
these were the longest and narrowest trypanosomes that I have met 
with in rats. 
Haemogregarine in the Field Mouse (Haemogregarina 
sylvatici sp. n. ?). 
In the blood of a long-tailed field mouse {Mus sglvaticus), caught 
in this neighbourhood, Apr. 7, 1912, I found haeinogregarines which 
differed considerably in appearance from those previously described. 
Unfortunately only two films from the peripheral blood were kept. 
Associated with these haemogregarines was a small number of parasites 
situated in the red blood corpuscles which are probably of the nature of 
Pirojolasma as will be evident when I describe them later on. 
The haemogregarines were not very numerous, only about 20 being 
found in two films measuring about f inch square. The parasites were 
only found free in the plasma; all the leucocytes in both preparations 
were carefully examined but none of the white cells harboured a 
parasite. 
The haemogregarines are oval, kidney or bean-shaped bodies 
sometimes straight, more often slightly crescentic, in appearance. The 
ends are rounded, usually equally, but in some cases one extremity is 
much more pointed than the other. 
They are not surrounded by a capsule. They measure on an 
average 15'5 g, in length by 6'1 g in breadth. (Plate II, fig. 14.) 
The protoplasm stains a deep blue colour with Giernsa and is very 
granular. It contains at one or both ends a large number of coarse 
chromatoid granules which stain deeply. In some there are fewer 
granules but these are much larger and even more deeply stained, and 
are often almost black in colour. Two haemogregarines were found in 
