THE PROTOZOA AS PARASITES OF MAN 



147 



to differ from that of E. colt chiefly in the number of the 

 amcebulae, which both in the free and in the encysted form 

 is only four. Binary fission takes place, and old, degener- 



Fig. 90. — Entamoeba dysenteries. — After Fantham. 

 A , Encysted form with four nuclei ; B, senile form with " buds." 



ating individuals are apt to undergo a process resembling 

 budding. 



A flagellate protozoon known as Trypanosoma is re- 

 sponsible for various very dangerous diseases 



Trypanosoma. K. , , J . ° 



of man and animals in warm countries. 

 Trypanosoma is parasitic in the blood and other fluids of 

 backboned animals, but also capable of living in an 

 invertebrate which sucks the blood of its vertebrate host, 

 and by this it is transferred from one vertebrate to 

 another. It has a worm-like body, about one-thousandth 

 of an inch in length, tapering towards the ends, but more 

 pointed in front than behind. The shape of the body is 

 maintained by a strong pellicle. A single flagellum stands 

 at the front end, and from its base an undulating membrane 

 runs along one side nearly to the hind end. The flagellum 

 is continued as a strongly-staining thread along the free 

 edge of the membrane, and terminates behind in a minute 

 " basal granule " or blepharoplast, embedded in the 'cyto- 

 plasm. By the working of the undulating membrane and 

 flagellum the animal swims rapidly with a graceful wavy 

 movement, either forwards or backwards. There is no 

 contractile vacuole. Near the middle of the body is an 

 egg-shaped nucleus, but a smaller mass, which stains like 

 the nucleus, stands close to the blepharoplast. This smaller 



