362 



TR YPA NO SO MI 



The Herpetomoninse are distinct forms, and are not stages in 

 the life-cycle of a trypanosome. 



Hereditary Infection.— In an important paper O'Farrell in 1913 

 traced the infection of the ovum of 1 the tick Hyalcmma cBgyptium 

 by Crithidia Usually the flagellate stage is passed in 



Fig. 81.^ — The Life-Cycle of Crithidia hyalommo O'Farrell, 191 3. 

 (After O'Farrell.) 



It demonstrates hereditary infection. The arrows in the infection of the 

 ovum, except the two on the right-hand side, are wrong. The left upper 

 arrow should run from the adult to the ovum; the other two arrows should 

 be omitted. 



haemocoelic fluid of the tick, but about the time of and during 

 ovoposition a considerable number of the flagellates enter the ovary, 

 and some penetrate by their aflagellar extremity into the ova, where 

 they become the Leishmaniform stage, which may form large plas- 

 modial masses which break up into small resting forms. This flagel- 

 late is therefore strictly parasitic in the tick, and its life-history 



