n6 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
The parasite, as seen in stained specimens, presented itself under two forms. 
Whether we are dealing with two haemogregarines or developmental forms of the 
same species I am unable to declare with certainty, but incline to the former view, 
as the two forms were practically constant in shape and staining reactions, and I 
could not observe intermediate stages. 
1. The first form consists of a parasite only slightly longer than the red cell, 
its pointed end being bent into a slight crook (Fig. i). 1 In this form there is not 
observed the great enlargement and decolouration of the red cell seen in the case of 
the second form. With Romanowsky the nucleus stains typically, reddish rose 
colour, and the protoplasm shows a number of coarse reddish granules mainly 
collected at the pointed end. In its staining the nucleus differs from that of the 
other form, which very rarely is stained red but only blue. The nucleus of the cell 
is displaced, but not nearly to the same extent as in the second form. Younger forms 
than this I have not observed. 
2. The second form consists of a typically folded vermicule (Fig. 2). They 
vary somewhat in size, and in the larger forms several peculiarities of structure are 
noticeable. 
The parasite itself has a well-developed nucleus situated in the thicker half of 
the parasite in the stained specimen. The nucleus commonly has a rhomboidal or 
elongated triangular shape (Fig. 5). It stains blue with Romanowsky and very 
rarely red. Not uncommonly at the tip of the ' tail ' end of the parasite there is a 
blue stained spot (Figs. 2 and 3). The large U-shaped forms are surrounded by a 
well-defined cyst which separates the parasites from the cyst wall. This cyst 
frequently shows some peculiarities of structure ; at the end corresponding to the 
bend of the haemogregarine there is an area staining a deep dull red (Fig. 3). This 
area is concave on the side facing the parasite, so that it appears to fit over the 
parasite as a cap. It is not, however, actually attached to the parasite, for sometimes 
a clear line can be seen separating this reddish area from the parasite (Figs. 4 and 5). 
The larger forms of the U-shaped parasite invariably show this stained (capsular) 
area, but it is not developed in the smaller forms, when also the cyst is not clearly 
defined. A certain amount of staining reaction (red) also is seen in other portions 
of the cyst. It is, however, in these encysted forms of the parasite, when found 
entirely free from red cells, that the cyst contents surrounding the parasite show a 
more diffuse staining. In these the conical area, at one end, is often lost and instead 
the cyst shows a general mottling with rather coarse granules (Fig. 6). 
Forms diverging somewhat from these typical forms are occasionally seen. 
Thus — 
(i) We have forms showing as many . as three adjacent nuclei, with 
indications of a corresponding division of the protoplasm (Fig. 7). 
I. The figures illustrating this paper have unfortunately been lost. 
