180 



PROTOZOOLOGY 



production usually initiates the production of the spores (Fig. 76). 

 The spores which are protected by a resistant membrane are capa- 

 ble of remaining viable for a long period of time outside the host 

 body. 





Fig. 76. Diagram illustrating the life-cycle of Thelohania legeri (Kudo), 

 a, extrusion of the polar filament in gut of anopheline larva; b, emerged 

 amoebula; c-f, schizogony in fat body; g-m, sporont-formation; m-x, 

 stages in spore-formation. 



Sexual reproduction and life-cycles 



Besides reproducing by the asexual method, numerous Protozoa 

 reproduce themselves in a manner comparable with the sexual re- 

 production which occurs universally in the Metazoa. Various types 

 of sexual reproduction have been reported in literature, of which a 

 few will be considered here. The sexual fusion or syngamy which is a 

 complete union of two gametes, has been reported from various 

 groups, while the conjugation which is a temporary union of two 

 individuals for the purpose of exchanging the nuclear material, is 

 found almost exclusively in the Ciliophora. 



Sexual fusion. The gametes which develop from trophozoites, may 

 be morphologically alike (isogametes) or unlike (anisogametes) , 



