355 



halteridia are simply stages in the life history of 

 a trypanosome. The ' halteridia ' undergo their 

 development in Culex ptpiens. (Vide note, p. 368). 

 The following stages occur : — 



(i) The blood is sucked into the stomach, the gametes 

 become spherical, and the mikrogametes (flagella), (which 

 themselves are built on the same fundamental plan as trypano- 

 somes) fertilise the makrogamete (female). 



(2) The result, as in the case of the malaria parasite, is a 

 zygote or copula which in eight to thirty-six hours becomes a 

 vermicule or ookinet/ 



(3) These ookinets are of three kinds — hermaphrodite, 

 male, and female. 



A. Development of the ookinet into an indifferent trypanosome. — 



The ookinet now develops into a typical trypanosome with 

 nucleus, blepharoplast, undulating membrane, and flagellum. 



[The locomotor apparatus of a trypanosome arises, accord- 

 ing to ScHAUDiNN, from the mitotic processes which take place 

 in , the nucleus of the ookinet. Three nuclear spindles are 

 formed by successive divisions. The third of these becomes the 

 locomotor apparatus. The excentric spindle fibres become the 

 thickened edge of the undulating membrane, the central fibres 

 form the free flagellum, while the contractile mantle fibres, 

 eight in number, which direct the movements of the nuclear 

 chromosomes on the spindle, become ' myonemes,' four of which 

 run on either side in the (Ektdplasmic) undulating membrane]. 



We thus get an indifferent trypanosome. 



B. Development of the indifferent trypanosome in the stomach of 

 Culex pipiens. 



'(i) Multiplication by longitudinal division takes place ; a 

 fresh locomotor apparatus is developed, the old one remaining 

 unchanged. The resulting trypanosomes are small in size. 



(2) The trypanosome has a resting or ' gregarine ' stage. 

 It bores its way into and even through the epithelial wall of 

 the stomach, contracts, and the flagellum becomes a short rod- 

 like process of attachment. It ma}' divide in this stage, forming 

 extensive clusters. This stage is adopted when the blood 

 supply is scanty in the stomach. If blood is imbibed the 

 parasites again become actively motile. 



