PIROPLASMA MURTS. 509 



order Hsemosporidia-, of the class Sporozoa, They were 

 not found to be numerous in the peripheral circulation, but 

 occurred in greater numbers in the internal organs above 

 mentioned. 



The trophozoites are ovoid (fig. 3) or pear-shaped (figs. 

 1, 2, and 7), the former varying from 0"5ju to TSjuin dia- 

 meter, the latter being from 2 fx to S fx long and I fi to 1*5 // 

 broad, and devoid of melanin pigment (fig. 8). There is 

 usually only one chromatin body or dot which may be peri- 

 pherally or centrally placed, more usually near one end, A 

 clear zone of protoplasm often surrounds this chromatin 

 body (fig. 17), and a vacuole (fig. 5) may occur in the cyto- 

 plasm of the parasite. Pairs of trophozoites often occur in a 

 host- corpuscle, but single trophozoites are also not infrequent. 



Some so-called " anicBboid " trophozoites (fig. 14) were 

 seen in the spleen. 



Endogenous multiplication takes place inside the rat's red 

 blood-corpuscle by simple fission. Double infection (fig. 10) 

 of a blood-corpuscle may occur, while free ovoid forms of the 

 parasite have also been seen in the plasma (figs. 20, 21). 

 Sometimes four parasites may be found in a corpuscle of the 

 peripheral circulation, and as many as six or eight in cor- 

 puscles in the spleen (figs. 13, 14). 



Some of the pathological effects in the white rats, very 

 probably directly due to this parasite, were ulcers on the ears, 

 alopecia, emaciation, anaemia, biliary fever, enlarged spleen, 

 etc., and in each case death resulted. 



From the foregoing characteristics the parasite may be 

 placed in the genus Piroplasma. A short account of my 

 exhibit of this parasite before the Zoological Society of 

 London appeared in the ' Proc. Zool. Soc.,' 1905 (12), where 

 I proposed the new specific name of muris, from its occur- 

 rence in a member of the Muridas. I would, then, call this 

 parasite Piroplasma muris. 



The appended list of literature cannot be set forward as in 

 any sense complete. To compile a complete list would need 



