INTRODUCTION 5 



and Plasmodium, which hve in man and also in blood- 

 sucking invertebrates. 



In the human protozoa which belong to Sarcodina and 

 Flagellata, sexual reproduction is not known, asexual re- 

 production by the trophozoite and in some in the cyst, 

 being the sole mode of multiplication. In the ciliate, Balan- 

 tidium coli, conjugation has been reported to occur by some 

 observers. In Plasmodium in addition to the schizogony 

 mentioned above, certain schizonts develop into macro- 

 gametes and microgametes which unite in pairs and pro- 

 duce numerous zveotes. The zvo"ote formation and subse- 

 quent development into an oocyst take place in the female 

 anopheline mosquito. 



As to the effects of the protozoa upon the human body, 

 information is at present not complete for all of them. In 

 the broad sense of the term, all protozoa living in man are 

 parasites. However, a ti'ue parasite is one which actually 

 lives at the expense of human body and brings about cer- 

 tain pathological conditions in it. The true protozoan para- 

 sites of man and the diseases for which they are responsible 

 are as follows: 



Entamoeba histolytica Amoebic dysentery, amoe- 



biasis 



Balantidium coli Balantidial dysentery, bal- 



antidiosis 



Trypanosoma gamhiense Central African sleeping 



sickness 



Trypanosoma rhodesiense East African sleeping sick- 

 ness 



Trypanosoma criizi Chagas' disease 



