284 SPOHOZOA. 



236. Plasmodium knowlesi Sinton & Mulligan. (Fig. 127 

 (PI. II).) 



Plasmodium sp., Franchini, 1927, pp. 467-71, 2 figs. 

 Plasmodium kochi (?) (part), Napier & Campbell, 1932, pp. 246-9. 

 Plasmodium, sp. (part), Kjiowles & Das-Gupta, 1932, pp. 301-20, 



7 pis. & 6 charts ; Sinton & Mulligan, 1932 a, p. 324. 

 ■\Plasm,odium, knowlesi, Sinton & Mulligan, 1932 6, pp. 379-80, 



409-21, pi. V, figs. 1-35. 

 Plasmodium knowlesi, Coatney & Roudabush, 1936, p. 339. 



Youngest rings closely resemble those of Laverania malarise 

 and measure one-fourth to one-half of the infected corpuscle. 

 Cytoplasm shows sHght but definite thickening on the side 

 opposite the chromatin, and a well- developed vacuole. 

 Chromatin prominent, and occurs as a single round, oval or 

 elongate mass or in two (rarely three) smaller masses. One 

 or, rarely, two minute accessory chromatin dots may be 

 present. Older trophozoites rounded or only very shghtly 

 amoeboid, vacuole very inconspicuous or absent. Mature 

 schizonts of the same size, or smaller than the normal red 

 corpuscles. Number of merozoites commonly about ten. 

 Schizogony cycle takes twenty-four hours. Pigment appears 

 early, is relatively abundant, and granules are fairly coarse, 

 varying from greenish-brown to almost black. Infected 

 red corpuscles not enlarged, but often show characteristic 

 distortion, and stippling usually absent with ordinary stains. 

 Oametocytes spherical, like those of P. malarise, about the 

 size of normal red corpuscle, and with abundant coarse and 

 dark pigment. Cytoplasm of the female gametocyte stains 

 deep blue with Romanowsky's stain, and its chromatin is 

 dense and compact, is usually situated peripherally, and 

 frequently shows a more deeply staining inner area ; the 

 pigment is scattered irregularly. The male gametocyte 

 stains poorly, and its chromatin is large and diffuse, appearing 

 to merge into the cytoplasm. Dark brown or almost black 

 granules of pigment occur in both the female and the male 

 gametocytes. Sporogony not known to take place in mos- 

 quitoes. 



Remarks. — Napier and Campbell (1932) found a Plasmodium 

 in the blood of a specimen of Silenus irus in Calcutta, said 

 to have been imported from Singapore. Knowles and Das- 

 Gupta (1932) described it in greater detail after inoculating 

 S. rhesus with the strain, in which host it multiphed enormously. 

 Sinton and Mulligan (1932) came to the conclusion that the 

 original infection in S. irus was a mixed one of Plasmodium, 

 inui var. cynomolgi and of P. knowlesi, and by inoculating 

 8. rhesu,s an almost pure infection with P. knowlesi was the 

 result. A large number of specimens of Silenus rhesus 

 from Northern India, examined by Knowles and Das-Gupta 

 (1932) as well as by Sinton and Mulligan, have not shown 



