96 Trypanosoma Diseases of Domestic Animals in Nyasaland. 



Figs. 11-19, 29 clays. Fig. 19 has an encysted appearance. 



Figs. 20-22, 30 days. It will be seen that most of the flagellates found in 

 the labial cavity are crithidial in type. They are generally ribbon-shaped, 

 with well-defined nuclei and micronuclei and free flagella. 



Figs. 23-30 are from the hypopharynx and have been obtained, as a rule, 

 by causing the fly to salivate on to a cover-glass. They represent the final 

 stage in the cycle of development — the reversion to the infective or " blood 

 form." They are smaller than those found in the blood of the vertebrate 

 host, but resemble them closely in every other way. 



Conclusions. 



1. Trypanosoma caproe is capable of passing through a cycle of develop- 

 ment in G. morsitans, the flies becoming infective some 19 days after feeding 

 on an infected animal. 



2. Trypanosoma caprce belongs to the same group as T. vivax and 

 T. uniforme, the development taking place only in the proboscis. 



3. The final stage of the development takes place in the hypopharynx 

 where the trypanosomes revert to the original " blood form " and become 

 infective. 



DESCRIPTION OF PLATE. 



Pigs. 1-3. — Common type of torpedo-shaped flagellates found attached in small single 

 groups or clusters to the labrum, near the bulb, after 19 to 21 days. 



Figs. 4-22. — Various other developmental forms found in the labial cavity in flies 

 dissected 24 to 30 days after their first infected feed. They are mostly crithidial in 

 type. 



Figs. 23-30. — " Blood forms " from the hypopharynx. These represent the final stage in 

 the cycle of development. 



Stained Giemsa. x 2000. 



