528 BIOLOGY OF THE PROTOZOA 



gain develop in the crab (Portunus depurator) and the sexual stages 

 in the cephalopod (Sepia officinalis); vegetative stages of the malaria 

 organisms, Plasmodium, develop in the blood of man or birds and 

 the sexual stages in the mosquito. In these blood-infesting Sporozoa 

 a further adaptation is noted in the loss of the characteristic cap- 

 sules of the metagamic spores which are inoculated with the bite 

 of the mosquito directly into the blood. In some cases parasites 

 reach the blood by way of the digestive tract and infection is con- 

 taminative. The rat parasite Haemogregarina (Hepatozoon) pemi- 

 ciosa (according to Miller, 1908) forms its metagamic spores in the 

 rat mite (Lelaps echidninus) . Such infected mites are eaten by 

 the rat and the spores develop in liver cells through some agametic 

 generations, the agamic spores finally entering the blood where 

 they are taken up by leukocytes in which the parasites encyst. 

 Such encysted spores are taken with the blood into the gut of the 

 mite where sexual phases take place and metagamic spores are 

 formed (Fig. 211). 



For characterization of the homologous stages in the very diverse 

 life histories of Sporozoa a special and fairly definite terminology 

 has been adopted by all students of the group beginning with Schau- 

 dinn. These terms which are employed in classifications are as 

 follows : 



Sporozoite. The final product of metagamic divisions and the 

 beginning of a new life history. 



Trophozoite. A vegetative stage which develops from a sporo- 

 zoite or from a merozoite. (Also termed according to conditions, 

 agamont, gamont or schizont.) 



Schizont. A mature trophozoite preparing for multiple or simple 

 division without fertilization. (Also termed agamont.) 



Schizontocyte. A special type of schizont (or gamont) which by 

 multiple division breaks up into a number of germ-forming centers 

 as in Caryotropha and Klossiella. 



Schizogony. The process of simple or multiple division of a 

 schizont. 



Merozoite. A product of schizogony leading to spread of an 

 infection in the same host. (Also called Agamete.) 



Sporont. A trophozoite destined to form copulating gametes. 

 This may be derived directly (i. c., without schizogony) from a 

 sporozoite as in Eugregarinida, or from a merozoite. (Also called 

 gamont) 



Sporogony. The process or processes of reproduction leading to 

 the formation of gametocytes and gametes. (Also called gamogony.) 



Gametocyte. A mother-cell which will produce gametes. 



Macrogametocyte. A mother-cell which will produce macrogam- 

 etes (rare) or develops directlv into a macrogamete or female germ 

 cell. 



