1908.] BLOOD-PARASITE OF WHITE MICE. 709 



mentioned varies with the specimen and with the stage of develop- 

 ment at which the parasite may be. At the initiation of the 

 trophic, intracellular phase of the life-history, the activity of the 

 organisms is very great, and, correlated with this, there is the 

 phase of most vigorous motion. The infected leucocyte figured 

 in text-figure 154, A-K, was observed for a period of seven hours^ 

 and even then the exit of the parasite from the leucocyte was 

 not seen, owing to the death of the leucocyte. 



An early stage is seen in text-figure 154, A, where the parasite 

 was lying in the leucocyte so that the nucleus of the latter 

 was practically in full view. About twenty-five minutes later, 

 the organism had spread itself out and become crescentic in 

 form (text-fig. 154, B, 0). The movements till then were very 

 vigorous, and much oscillation of granules in both parasite and 

 leucocyte nucleus was observed. Half an hour after the obser- 

 vation was commenced, the forward movements of the pai-asite 

 slowed very much, though the movements of the granules remained 

 much the same (text-fig. 154, D). About the same time the 

 protoplasm of the parasite began to move from the periphery 

 towards the anterior end, which became much more globose and 

 began to curve (text-fig. 154, E, F). An anterior end could be 

 distinguished definitely as such at the end of 55 minutes (text- 

 fig. 154, F). Two hours after the first observation was made the 

 parasite had assumed the " comma " form and a vesicle began to 

 make its appearance (text-fig. 154, F-J). It remained in this 

 condition for a long time, the only change that occurred being that 

 the protoplasm became much more granular and there was a 

 slight retraction of the posterior end, while the vacuole increased 

 in size and chromatin masses appeared in it (text-fig. 154, G-K). 

 Death of the leucocyte prevented further reliable observations 

 being made on this parasite, but the exit of the organism from its 

 host-cell was seen in other specimens (PI. XXXIX. figs. 18, 19). 



Extrusion of the parasite is brought about by internal pressure. 

 The Leucocytozoon moves forwards with a slow, gliding movement. 

 This continues steadily until extrusion is completed. There is 

 slight resistance at the periphery of the leucocyte, but on the exit 

 of the parasite, the protoplasm of the host-cell closes up and the 

 point of exit is invisible (PI. XXXIX. figs. 18, 19). The freed 

 parasite remains quiescent for a short time after leaving the 

 corpuscle. 



Stages of endoglobular parasites are figured in PI. XXXIX. 

 figs. 15, 16, 17. 



(b) Movements of the small, free Merozoifes, 



In some of the peripheral blood mixed with normal saline to 

 which a little methylene-bkie was added, sausage- or bean-shaped 

 bodies occurred (PI. XXXIX. fig. 13). These moved fairly 

 actively, the movements being much more energetic if the 

 organism were in the neighbourhood of a leucocyte. The body 

 of the parasite would seem to be somewhat flattened, for it is 



