H. Henry 
191 
Morphology of the parasite. 
The haemogregarine was found in six out of sixteen fish examined 
but in all of these the infection is very slight. It never occurs free in 
the plasma but is always intracellular. Infected red corpuscles harbour 
only one haemogregarine, so that multiple infections have never been 
observed. The nucleus of the host cell is frequently pushed to one 
side, particularly by the larger forms of the parasite, but no other change 
in shape, size, or staining reactions of either the nucleus or the 
protoplasm of the host cell is evident. The parasite is not surrounded 
by a capsule or cyst. It is met with in the blood in several different 
phases of development, which for descriptive purposes may be roughly 
divided into three main types, viz. 
1. A short, broad, oval or pear-shaped form. 
2. A long, thin form, thickened at one pole and more or less 
pointed at the other, and slightly bent so as to be comma-shaped. 
3. A long, thick, slightly curved type which is reniform. 
These types are not to be looked upon as sharply demarcated one from 
the others. For instance, there are very numerous phases of development 
between types 1 and 3, or between types 2 and 3. Moreover these 
types are not to be found in equal proportion throughout the whole 
series of films. In two of the infected fish type 1 largely preponderates, 
and in another two, type 3 is predominant. In the remaining two 
infected fish specimens of type 1 and type 3 are about equally 
distributed, whereas in all type 2 occurs but rarely. 
Type 1 (PI. VIII, figs. 1 to 10.) 
The earliest stage consists of small, oval or pyriform bodies varying 
from 5 yti to 6'8 y. in length, the average being 6 g, and varying from 
3'3 g to ^ g m breadth, the average being 3'7 g. The nucleus, which is 
always situated at the narrower pole of the parasite, varies from 2 g to 
4 yu, in its longest diameter, the average length being 2'8 g. It does not 
occupy the whole thickness of the lesser pole, but is usually separated 
from the margin of the parasite by a thin rim of protoplasm, and 
appears to consist of a varying number of coarse, deeply staining 
chromatin granules, which tend to remain loosely bunched together. 
Occasionally a string of chromatin granules may be found wandering 
away from the main nucleus into the body of the parasite (fig. 2). The 
