SPOROZOA 105 



which induces the common malarial fevers of temperate regions, 

 certain of the full-grown germs, instead of behaving as schizonts, 

 pass, as it were, to rest as round cells; while in the allied 

 genus Laverania (Haemomenas, Ross) these resting -cells are 

 crescentic, with blunt horns, and are usually termed half-moons 

 (Fig. 35, O, T), characteristic of the bilious or pernicious 

 remittent fevers of the tropics and of the warmer temperate 

 regions in summer. These round or crescent-shaped cells are 

 the gametocytes, which only develop further in the drawn blood, 

 whether under the microscope, protected against evaporation, 

 or in the stomach of the Anopheles : the crescents become round, 

 and then they, like the already round ones of Haemamoeba, 

 differentiate in exactly the same way as the corresponding cells 

 of Goccidium sehubergi. The female cell only exhibits certain 

 changes in its nucleus to convert it into an oosphere : the male 

 emits a small number of sperms, long flagellum-like bodies, each with 

 a nucleus ; and these, by their wriggling, detach themselves from 

 the central core, no longer nucleated. The male gametogonium 

 with its protruded sperms was termed the " Polymitus form," and 

 was by some regarded as a degeneration -form, until MacCallum 

 discovered that a " flagellum " regularly undergoes sexual f? sion 

 with an oosphere in Halteridium, as has since been found in the 

 other genera. The oosperm (Y) so formed is at first motile 

 (" ookinete "), as it is in Haemosporidae, and passes into the 

 epithelium of the stomach of the gnat and then through the wall, 

 acquiring a cyst-wall and finally projecting into the coelom (a-e). 

 Here it segments into a number of spheres- (" zygotomeres " of 

 Ross) corresponding to the Coccidian spores, but which never 

 acquire a proper wall (/). These by segmentation produce at 

 their surface an immense quantity of elongated sporozoites 

 (the " zygotoblasts " or "blasts" of Ross, Fig. 35, g), these are 

 ultimately freed by the disappearance of the cyst-wall of the 

 oosperm, pass through the coelom into the salivary gland (h), 

 and are discharged with its secretion into the wound that the 

 gnat inflicts in biting. In the blood the blasts follow the 

 ordinary development of merozoites in the blood corpuscle, 

 and the patient shows the corresponding signs of fever. This 

 has been completely proved by rearing the insect from the egg, 

 feeding it on the blood of a patient in whose blood there 

 were ascertained to be the germs of a definite species of Haem- 



