BY T HARVEY JOHNSTON AND J. BURTON CLKLAND. 505 



Plasmodium passeris, n.sp., from the Sparrow, Passer domesticus. 

 (Plate xlviii., figs.19-24.) 



In March, 1909, a sparrow fell dead from its roosting-place 

 one evening, and was picked up and submitted for examination 

 by Mr. R. Grant, of the staff of the Bureau. Blood-films showed 

 the presence of Plasmodia. In the early stage, these appeared 

 as small amoeboid masses, of slightly irregular outline, faintly 

 stained bluish with Giemsa, and situated at or quite near one end 

 of the host-cell. In double infections of one cell, the two parasites 

 were found together at one end, one lying usually a little more 

 laterally to the other, or at opposite ends of the host-cell. 



As they increased in size, small melanin-granules became dis- 

 cernible, and the nucleus of the red corpuscle was gradually 

 displaced to one side to make room for large, more or less 

 spherical, bodies. Eventually, in the older forms, the host- 

 nucleus had l)een extruded, the rounded parasite occupying its 

 jDlace in the distorted red cell. Finally, some examples of this 

 stage of the parasite were found free in the plasma. In these 

 large forms, one or two vacuoles were occasionally to be seen, and 

 melanin in varying amounts was present in all. This pigment 

 seemed to occupy no particular position, being scattered irregu- 

 larly as small granules or aggregated in larger masses in various 

 situations. 



Two types could be distinguished in the large parasites : a very 

 pale form and a well-stained, somewhat granular form. Appa- 

 rently these represent, the former male gametocytes, the latter 

 female. No definite difference in the amount or disposition of 

 the pigment could be detected between the two forms. No 

 parasites were seen in any stages suggestive of schizony. 



The following is a description of ten consecutive full-sized 

 parasites, arranged according to the types presented : — 



(1) Very pale. Host's nucleus has disappeared. A few small 

 scattered grains of melanin. 



(2) Very pale. Host's nucleus displaced. Pigment as four or 

 five small masses. 



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