Laveran was the first to describe a member of the {103}ACYSTOSPORIDAE, in 1880, as an organism always to be found in the blood of patients suffering from malarial fever; this received the rather inappropriate name of _Plasmodium_, which, by a pedantic adherence to the laws of priority, has been used by systematists as a generic name. Golgi demonstrated the coincidence of the stages of the intermittent fever with those of the life-cycle of the parasite in the patient, the maturation of the schizont and liberation of the sporozoites coinciding with the fits of fever. Manson, who had already shown that the Nematodes of the blood that give rise to Filarial haematuria (see Vol. II. p. 149) have an alternating life in the gnats or mosquitos of the common genus _Culex_,[110] in 1896 suggested to Ronald Ross that the same might apply to this parasite, and thus inspired a most successful work. The hypothesis had old prejudices in its favour, for in many parts there was a current belief that sleeping under mosquito-netting at least helped other precautions against malaria. Ross found early in his investigations that _Culex_ was a good host for the allied genus _Haemoproteus_ or _Proteosoma_, parasitic in birds, but could neither inoculate man with fever nor be inoculated from man. He found, however, that the malaria germs from man underwent further changes in the stomach of a "dappled-wing mosquito," that is, as we have since learned, a member of the genus _Anopheles_. Thenceforward the study advanced rapidly, and a number of inquirers, including Grassi, Koch, MacCallum (who discovered the true method of sexual union in _Halteridium_[111]), and Ross himself, completed his discovery by supplying a complete picture of the life-cycles of the malaria-germs. Unfortunately, there has been a most unhappy rivalry as to the priority of the share in each fragment of the discovery, whose history is summarised by Nuttall, we believe, with perfect fairness.[112] The merozoite is always amoeboid, and in this state enters the blood corpuscle; herein it attains its full size, as a schizont, becoming filled with granules of "melanin" or black pigment, probably a decomposition product of the red colouring matter (haemoglobin). {104}[Illustration: FIG. 35.—Life-history of Malarial Parasites. _A-G_, Amoebula of quartan parasite to sporulation; _H_, its gametocyte; _I-M_, amoebula of tertian parasite to sporulation; _N_, its gametocyte; _O_, _T_, "crescents" or gametocytes of _Laverania_; _P-S_, sperm-formation; _U-W_, maturation of oosphere; _X_, fertilisation; _Y_, zygote. _a_, Zygote enlarging in gut of Mosquito; _b-e_, passing into the coelom; _f_, the contents segmented into naked spores; _g_, the spores forming sickle-germs or sporozoites; _h_, sporozoites passing into the salivary glands. (From Calkins's _Protozoa_, after Ross and Fielding Ould.)]