4 DISEASES DUE TO PROTOZOA 



is) Spore Formation. 



A quiescent body, the schizont, is formed. The nucleus and 

 cytoplasm divide into a number of asexual spores known as merozoites, 

 leaving, as a rule, a " nucleus de reliqual," or rest-bodv. These 

 merozoites enter new cells in the host, where they grow into tropho- 

 zoites, and complete ?.n asexual life-cycle or the cycle of simple 

 schizogony. 



Under adverse conditions, such as scarcity of food in the host, &c., 

 the merozoites develop into more resisting forms or gametocytes. In 

 these latter female and male elements are separated. Such elements, 

 nuclear, may remain in the same cell or separate cells. Usuallv the 

 male element of one fuses — zygosis — with the female element of 

 another and forms a new individual, with a single new nucleus known 

 as a sporont. This reproduces itself rapidly by binary fission or spore 

 formation, the resulting spores being known as sporozoites. 

 (4) Parthenogenesis.. 



This is a form of reproduction from the female type of parasite as 

 may take place in malaria. The female gametocvte can resist drugs 

 in the body and lie dormant until taken up by a blood-sucking insect, 

 when the nucleus and protoplasm will divide, one portion disappearing, 

 while the other forms merozoites, and starts the cycle of schizogony 



agam. 



PATHOGENICITY. 



The pathogenicit}^ of protozoa is considered under the diseases 

 caused by them. 



CLASSIFICATION. 



There are live groups : — 

 (i) The Sarcodina (Rhisopoda). 



These move by a protrusion of protoplasmic processes, broad and 

 blunt or thin and sharp. They may or may not be covered in part 

 with shells. They multiply by budding or fission. Occasionally 

 spores are formed. 



(2) The Mastigophora (FJagellata). 



These have specialized motile protoplasmic processes known as 

 flagellum or flagella. The shape of the parasite is defined and covered 

 with a membrane. 



They multiply by longitudinal fission. 



(3) Sporozoa. 



(A) Telosporidia. 



In these the spore formation is distinct from and later than the 

 trophic phase of the life-cycle. 



