96 THE ANIMAL PARASITES OF MAN 



extracted from the body, not, however, in entirely fresh cases, 

 but only after the illness has persisted for several days. Expe- 

 rience has also demonstrated that the crescents, which* are only 

 observed in malignant tertian fever, increase greatly if the disease 

 is of long duration, and finally are the only forms present ; they also 

 do not retain their shape, but become shortened to ovals, and at 

 last become spheres. This process can be regularly induced by 

 the addition of distilled water [Marshall (i)], or by breathing on the 

 slide [Manson (2)]. Frequently also one may observe that some 

 of the spheres (in abstracted blood) develop " flagella " that 

 actively lash about and thus become the " polymitus " : the fla- 

 gella detach themselves, leaving behind an immovable lump of 

 protoplasm with grains of melanin. 



As all these processes were found to take place outside the cir- 

 culating blood and to lead to final disintegration, and as nuclei were 

 not visible, most investigators regarded the spheres, sickles and poly- 

 mites as forms of degeneration of the malaria parasites. Only 

 Mannaberg (3) stated that having seen indications of the union 

 of two crescents he regarded these at any rate as representing 

 conjugation forms. 



The assumption of the absence of the nucleus was, however, 

 erroneous. Sacharoff (4) first demonstrated the nucleus in spheres 

 from the blood of crows, and also showed that the entire nuclear 

 substance passes into the flagella when polymitus formation takes 

 place. The experiments also undertaken by Ross on Hanson's 

 suggestion were very important ; they demonstrated that crescents 

 sucked up by mosquitoes from the blood of a man soon turned 

 to spheres in the stomach, and about half of them were trans- 

 formed into polymites. MacCallum (5) recognised the significance of 

 the "flagella" in the Haemosporidia of crows; he, like Opie(6) 

 before him, found that there were two kinds of spheres, one kind 

 with a coarsely granular protoplasm which became a vivid blue 

 when stained with methylene blue, the other hyaline and scarcely 

 stainable : the latter only becoming polymites. He observed 

 that the actively moving flagella which detached themselves 

 penetrated into the coarsely granular spheres, and thus the 

 enigma was solved. The " flagella " whose origin and composi- 

 tion Bignami and Bastianelli (7) had traced in the plasmodium of 

 the aestivo-autumnal fever are, accordingly, microgametes ; the 

 spheres are partly macrogametes, partly, so far as they become 

 polymites, microgametocytes ; and the polymitus is a microgameto- 

 cyte at the moment of the development of the microgametes. 



