516 A MANUAL OF BACTERIOLOGY 



higher animals. The female cells or female gametocytes 

 or gametes are non-flagellated, and are fertilised by the 

 entrance of one of the flagella of a male gametocyte. This 

 fertilisation takes place in the stomach (middle intestine) of 

 certain species of mosquito, and after fertilisation a series of 

 changes ensues resulting in the formation of spore-like 

 bodies, which are injected when the insect bites its victim, 

 and thus the infection of fresh individuals with the malaria 

 parasite takes place. The first demonstration of the nature 

 of " flagellated bodies " was given by Opie and MacCallum 

 on the Halteridium, a parasite of pigeons (p. 528), and this 

 forms a good example of the value of abstract research 

 to practical medicine (see p. 528). Ross also followed the 

 development of the malaria-like Proteosoma of sparrows, 

 etc., in the mosquito, Culex fatigans. The development 

 of the malaria parasite of man in the mosquito is as follows, 

 according to Ross and Fielding- Ould. 1 It is not known 

 what determines whether an amoebula will become a 

 sporocyte or a gametocyte. When the sexual cells or 

 " gametocytes " are ingested with the blood by the mos- 

 quito, they pass into the middle intestine. Within a few 

 minutes the corpuscles enclosing them break down, the 

 parasites are set free, and quickly become spherical or 

 ovoid (Fig. 59, c, e, and/). One or two spherical granules 

 are often attached to the naked parasites, and may repre- 

 sent polar bodies (Fig. 59, c and /). Very soon the male 

 cells become flagellated (Fig. 59, c), and before long the 

 flagella or " microgametes " break away from the parent 

 cell, and by their own motility make their way through 

 the liquor sanguinis. Should one come in contact with 

 a female cell or " macrogamete," it fuses with the latter, 

 uniting with the nucleus (Fig. 59, /), fertilisation is com- 

 pleted, and a " zygote " is formed. As the zygote at this 

 stage is motile it is known as a " travelling vermicule " or 



* Thompson Yates Laboratories Report, vol. iii, pt. ii, p. 183. 



