1906.] Encystation in Trypanosoma grayi Novy, etc. 



37 



fl. v.), which reminds one of the flagellar vacuole described by Leishman 

 during the formation of a flagellum in the Leishman-Donovan bodies in 

 cultures, but here the sequence of events is inverted, as it were. Finally 

 the pink vacuole disappears, but a streak, which gradually fades away, can be 

 seen for a time in front of the blepharoplast (fig. 6). The cyst closes up 

 round the pointed end of the body, and then changes in form, becoming 

 first oval (fig. 7) and then irregularly circular in outline (fig. 8). In the 

 circular cysts, which are the last stage, it is difficult to make out much detail, 

 but in favourable examples they can be seen to contain hyaline protoplasm, 

 staining faintly bluish, with the dark purple-stained blepharoplast and the 

 nucleus generally represented by irregularly scattered granules, staining a 

 purplish-red tint. The cyst- wall also stains strongly and appears slightly 

 redder than the nucleus. 



Fig. 1. 



Fig. 2. 



Fig. 3. 



Fig. 4. 



-Jt.s. 



Fig. 5. 



Fig. 6. 



N- 



Fig. 8. 



I will now state briefly the conditions observed in other parts of the gut 

 of the fly in which the cysts were found. The red blood was found teeming 

 with trypanosomes, nearly all large forms of indifferent type. Very few 

 young forms were found, and male forms were very scarce. No pronounced 

 female types were found in this region, though many of the large indifferent 

 forms approach the female type in the shortness of their free flagellum. In 



