TRYPANOSOMA 



43 



m.. 



Besides this main nucleus known as the trophonucleus there is present 

 a small rounded or rod-like particle regarded by some as being also com- 

 posed of nuclear material and believed to have to do with controlling 

 the movements of the creature. This particle, commonly termed the 

 kinetonueleus (Fig. i8, k), is in typical cases situated near the " posterior '' 

 (non-flagellar) end of the body although its position varies at different 

 stages in the life-history. The flagellum originates close to the kineto- 

 nueleus, usually in a small granule (basal granule — Fig. i8, b.g). 



The trypanosome multiplies by a characteristic process of longitudinal 

 fission in which basal granule (and ? flagellum), kinetonueleus, tropho- 

 nucleus and protoplasmic body divide in the order named. Whether 

 during this process the flagellum undergoes 

 longitudinal splitting, commencing at its 

 basal end, or whether on the other hand 

 only the basal granule splits and a new 

 flagellum sprouts out from one of the two 

 resulting granules, seems to be still a matter 

 'of doubt. 



As is the case with Euglena there appears 

 to be no process of syngamy in the life- 

 history of Trypanosoma. 



The Trypanosome is typically a parasite 

 of the blood of a vertebrate. Its convey- 

 ance from one host to another is typically 

 carried out through the agency of some 

 blood-sucking animal, such as a blood- 

 sucking fly or flea in the case of terrestrial 

 animals or a leech in the case of those 

 inhabiting water, and, in accordance with 



this, part of the life-history is specially adapted to existence in the body 

 of this intermediate host. 



As an example of a trypanosome life-history we will take that of 

 Trypanosoma gambiense — the parasite of sleeping sickness. This is 

 essentially a parasite of mammalian blood, in which when abundant it may 

 be seen readily with a high power of the microscope, wriggling through 

 the fluid and knocking about the corpuscles in its course. When infection 

 takes place the few trypanosomes inoculated into the blood multiply 

 rapidly and they may become very numerous. The numbers in the 

 blood do not remain constant at any maximum but at varying intervals 

 undergo great reduction, all except comparatively few dying off. When 

 the blood is examined at this time, before the trypanosomes again increase 



Fig. i8: 



Trypanosoma gambiense. 

 b.g. Basal granule ; /, flagellum ; 

 A, kinetonueleus ; m, membrane 

 t, trophonucleus. 



