1908.] BLOOD-PARASITE OF WHITE MICE. 713 



Similar parasites were afterwards studied by Berestneff, Sacharoff, 

 Ziemann, and Laveran. The latter states that Danilewsky's 

 parasites really occur in immature erythroblasts. The parasite 

 was stated later by Schaudinn [12] in 1905 to be a stage in the 

 life-history of a Spirochsete. The matter is fully discussed by 

 James [10], and as it is very controversial, need not be dwelt on 

 further here. 



Bentley [3] and James [10] independently described a parasite 

 from the leucocytes of pariah dogs in India in 1905. This was a 

 true Leucocytozoon and is known as L. canis. A memoir by 

 Christophers [5] on the same parasite appeared in 1906, and the 

 following year he worked out the sexual cycle in the tick [6]. 

 Other Leucocytozoa have been described in mammals by Patton 

 [11] in the Indian palm-squirrel, Funamhulus pennantii, under 

 the name of L. funamhuli ; in Malay dogs by Gerrard [9] and 

 Wenyon [14] ; and in rats in various parts of the world by 

 Balfour [2] from leucocytes of 3Ius decuviamis at Khartoum, 

 by Adie [1] from Mus rattus in the Punjaub (as L. ratti), and by 

 Cleland [7] from rats in Perth, Western Australia. These para- 

 sites in rats are probably best known as L. tnuris (cf. page 704). 

 A form known as L.felis has been described, I believe, from the 

 Indian bazaar cat in Madras by Christophers and Patton. 



Outside mammals, from other vertebrates, we have recorded 

 L. ranarii,m from the Amphibian Leptodactylus ocellatus by 

 Carini [14] ; and quite recently L. lovati, a form from the leuco- 

 cytes of grouse by Seligmann and Sambon [13]. 



These are, I think, all or nearly all the Leucocytozoa recorded 

 to date (May, 1 908). Whether they have any intimate connection 

 with Flagellates, such asthat suggested by Schaudinn [12] remains 

 to be seen — probably they have not. 



These parasites are all gregariniform. Those in mammals are 

 much about the same size, and occur both free in the plasma or 

 endoglobular in the leucocytes. Schizogony is known in the bone- 

 marrow [5] and liver. 



Laveran suggested that the Leucocytozoa should be included in 

 the genus Ilcemogregarina. However, as they occur in a non- 

 hsemoglobin-containing host, viz. leucocytes, while strict Hsemo- 

 gregarines are found in erythrocytes, I think the generic name 

 Leucocytozoon should be retained. The name for the parasite 

 described in this memoir for the first time in the leucocytes of the 

 mouse is L. rtiusculi. 



Su7}imary, 



(1) The forms of L. micscidi here described occur in the 

 mononuclear and transitional leucocytes of white mice. 



(2) The free trophozoites in the plasma are gregariniform or 

 reniform vermicules, the average size being ]0"9/x long and 5"1^ 

 broad (cf. PI. XXXIX. figs. 1-12). 



(3) The free trophozoites sooner or later enter leucocytes of the 

 host and grow at the expense of the nucleus of the leucocyte 



