TRYPANOSOMA VIVAX 



563 



they are long and scroll-like. The posterior end is seldom truncated, as 

 in the corresponding forms of T. congolense. At a later stage the nucleus 

 and kinetoplast are close together at the posterior end of the body, and 

 it is these forms which invade the hypoj)harynx. The nucleus then 

 moves forward, and the infective metacyclic trypanosomes are produced. 

 These are slender, markedly undulant trypanosomes with sharply-pointed 



Fig. 



!33. — Developmental Form of T. vivax in Qlossina tachinoides (x 2,000). 

 (After Lloyd and Johnson, 1924.) 



1-2. Degenerate forms in mid-gut and crop. 



3-4. Crithidia forms from fixed colonies in labial cavity. 



5-6. Pre-infective forms in labial cavity. 



7-9. Infective forms in hypopharjTix (G. morsiians and G. palpalis). 



posterior ends and a free flagellum, which is from one-third to one-fourth 

 the length of the body. Measurements of a number of infective forms 

 from three species of tsetse fly gave the following average dimensions: 



J- .J Length of the Breadth at 

 ijengm. ^lagellum. Nucleus. 



Glossina tachinoides 

 Glossina palpalis 

 Glossina morsitans . 



14-4 

 14-9 

 14-8 



3-9 

 4-3 

 4-1 



1-8 

 1-9 

 1-6 



By means of the above characters it is possible to recognize a T. vivax 

 infection in tsetse flies without the necessity of infecting animals (see p. 515). 



Mechanical transmission by means of Stomoxys was effected by 

 Boufiard (1907) and by Bouet and Roubaud (1912a). 



