Strain of T. brucei from Zululand. 531 



a living non-infective fly, and probably earne through the labial cavity from 

 the proventriculus. Some of them may possibly have come from the 

 hypopharynx, and in that case they may have been proventricular forms on 

 their way to infect the salivary glands. Figs. 7-20 are various types found 

 in the salivary glands — crithidial, encysted, and immature "blood forms." 

 Figs. 21-28 represent the finished product — the infective or " blood forms." 



If this plate is compared with that representing the developmental forms 

 of the trypanosome causing disease in man in Nyasaland* in the proventri- 

 culus and salivary glands of G. rnorsitans, the extraordinary likeness between 

 the two is at once evident, and is another argument in favour of these two 

 strains being identical. 



Conclusions. 



1. T. brucei, Zululand, 1913, belongs to the same group as T. gambiense as 

 regards its cycle of development in the tsetse fly. 



2. It has been shown that the trypanosome causing disease in man in 

 Nyasaland also belongs to the same group. 



3. The cycle of development of the jSTyasaland and Zululand trypanosomes 

 in G. rnorsitans is so marvellously alike that it affords another reason for 

 believing in the identity of these two trypanosomes. 



DESCRIPTION OF PLATE. 

 Figs. 1 and 2. — Trypanosomes from proventriculus. 



Figs. 3-6. — Proventricular types which were extruded on to a cover-glass by a living 

 non-infective fly. 



Figs. 7-20. — Crithidial, apparently encysted, and immature " blood forms " found in the 

 salivary glands. 



Figs. 21-28. — The final stage in the salivary glands — the infective or "blood forms." 



Stained Giemsa. x 2000. 



* ' Roy. Soc. Proc.,' this vol , Plate 24. 



