110 
Haematozoa in Wild Animals 
elsewhere, the African P. canis appears to be peculiarly specific since 
infection experiments made with it upon jackals and foxes ( Parasitology , 
Yol. II. p. 211) have given negative results. Should future investigation 
prove that the parasite of the jackal differs from the types of P. canis 
encountered in “salted” dogs, I would propose to refer it to a new 
genus Rossiella 1 (Rossia is preoccupied) in view of its specific name. 
The following description is based upon the examination of 90 para¬ 
sites encountered after a complete search had been made of the stained 
preparations at my disposal. The spleen contained 84 parasites, the 
liver smears only six parasites. 
P.rossi occurs as a large intracorpuscular parasite of rounded, ovoid, 
sub-pyriform or irregular shape, possessing a single large nucleus, and 
occurring singly, in pairs or in fours, within the infected corpuscles. The 
parasite produces no pigment and appears to multiply by simple division 
into two parasites, which may in turn subdivide. Simple division of the 
nucleus precedes the separation into daughter cells. Judging from the 
stained preparations there is evidence that the parasite is capable of 
amoeboid movement at various stages of its development. The parasite 
causes no apparent changes in the corpuscles which it inhabits. 
Measurements. The smallest uninucleate parasites measured 15 /x, the 
largest 33 x 5 3 fx. Since the large parasites subdivide to form two or 
four smaller parasites intermediate sizes are encountered with nuclei of 
corresponding size. Both the infected and uninfected red blood cor¬ 
puscles varied in size, from 6 to 9 \x in diameter. 
General structure. The general form of the parasite varies consider¬ 
ably. It may be spherical and sharply defined (PI. X, Figs. 1, 5, 16) or 
ovoid (Figs. 4, 10, 25) to sub-pyriform (Figs. 7, 13, 14), or it may be 
irregular in outline owing to the protrusion of amoeboid processes which 
are lobose (Figs. 3, 15) or more or less pointed (Figs. 8,12,19, 26). The 
protoplasm takes a clear blue colour, when stained by Giemsa, with a 
tendency for the staining to be more intense at the periphery, as in 
Piroplasma, but there is less evidence of vacuolar structure; in fact the 
protoplasm may at times assume a uniformly blue tint. In all the para¬ 
sites a clear unstained halo surrounds the chromatin mass. At times 
clear vacuolar areas are seen in the blue staining protoplasm (Figs. 1,3,15), 
at other times fairly definite achromatic lines traverse the parasite 
(Figs. 16, 17). The nucleus is striking because of its relatively large 
size. It is situated centrally or peripherally; in the latter case it is in 
most instances bounded on the outside by a band of blue-staining pro- 
1 In honour of Professor Ronald Ross, C.B., F.R.S. 
