In any case Ross (1898) had clearly established the importance of mosquitoes in the spread of malaria among birds. It was now only a question of proving whether, and how far, mosquitoes were concerned with human malaria. Ross himself worked to this end. Here the experiments of Italian investigators (Bignami, Bastianelli, Grassi)[196] were of importance. These investigators studied the fate of malarial parasites in man, produced malaria in men experimentally by the bites of infected mosquitoes, and established that only mosquitoes belonging to the genus _Anopheles_ were concerned, and not species of _Culex_. These latter are only able to transmit _Proteosoma_ to birds. It is true that _Culex_ can ingest the human malarial parasites, but the latter do not develop in them. Development only occurs in species of _Anopheles_. In _Anopheles_ (and similarly for _Proteosoma_ in _Culex_) sexual reproduction takes place; crescents, spheres and polymitus forms are necessary stages of development in the mosquito. [196] Grassi, B. (1901), “Die Malaria,” 250 pp., 8 plates. G. Fischer, Jena. With these discoveries the campaign against malaria became more definite. It was directed partly against the transmitters, whose biology and life-cycle were more thoroughly investigated, instead of merely against the infection of the adult _Anopheles_. The latter do not, as was believed for some time, transmit the malarial germs to their offspring. They always infect themselves from human beings, whereby the relapses appearing in early summer, and the latent infection, especially of children of natives, play a principal part (Stephens and Christophers, Koch). Further, the crusade was directed against the infection of man by the bites of _Anopheles_. Important results have been obtained in these directions. Low and Sambon in 1900 lived in a mosquito-screened hut in a malarial part of the Roman Campagna for three of the most malarious months and did not contract the disease. In the same year Dr. P. T. Manson was infected with malaria by infected mosquitoes sent from Italy. The rôle of mosquitoes having been proved, it may be hoped that ultimately the eradication of malaria, or at least a considerable restriction of it, will be achieved. It is of importance to record that, although malarial parasites occur in mammals (monkeys, bats, etc.) the human ones are not transmissible to mammals, not even to monkeys. The species, therefore, are specific to the different hosts (Dionisi, Kossel, Ziemann, Vassall). An important work dealing with the modern applications of the mosquito-malaria theory in all parts of the Tropics was published by Sir Ronald Ross in 1911. It is entitled “The Prevention of Malaria” (John Murray, London, 21s.). DEVELOPMENT OF THE MALARIAL PARASITES OF MAN.