298 Major Bonald Ross [March 2, 



and is the cause of Texas cattle-fever ; the third — for which I adopt 

 the name of Haemamcebidse Wassielewski — is found in man, monkeys, 

 bats and birds. It is to this third group — the Haemamcebidas — to 

 which we must now direct our attention, because it includes the 

 parasites of malarial fever. There are at least two known species 

 found in birds, two in bats, one in monkeys, and three in man. The 

 human parasites are those which respectively cause the threo varieties 

 of malarial fever — quartan, tertian, and remittent or pernicious fever. 

 For these three species I adopt the names Hsemamceba malariss 

 (quartan), Hsemamceba vivax (tertian), and Hsemomenas prsecox 

 (remittent fever).* According to Metchnikoff the group belongs, or 

 is allied, to the Coccidiidae. All the species have a close resemblance 

 to each other, and all contain the typical melanin of malarial fever. 

 The youngest parasites are found as minute amcebulse living within 

 the red corpuscle and generally containing granules of this melanin 

 (which, indeed, is derived by the parasite from the haemoglobin of the 

 corpuscle within which it makes its abode). The amoebulaB grow 

 rapidly in size, until, after one or more days (according to the species) 

 they reach maturity. At this point many of them become sporocytes 

 — that is, give rise to ordinary spores by vegetative reproduction. 

 These spores presently attach themselves to fresh corpuscles, become 

 fresh amcebulas, and so continue the life of the parasites indefinitely 

 within the vertebrate host. Others of the amcebulas, however, instead 

 of becoming sporocytes like the rest, become gametocytes. 



Now it is to these gametocytes that an extreme interest attaches, 

 because it is to them, and to Manson's study of them, that we owe the 

 solution of the malarial problem. Numerous observers had examined 

 them before Manson's time, but all had failed in arriving; at a correct 

 idea as to their function. It had been often observed that they circu- 

 late in the blood of the vertebrate hosts without apparently perform- 

 ing any function at all. As soon, however, as they are drawn from 

 the circulation — as when the blood containing them is made into a 

 fresh specimen for microscopic examination — they undergo the most 

 remarkable changes. They swell up and liberate themselves from the 

 enclosing corpuscle ; and then some of them are suddenly seen to 

 emit a number of long motile filaments. These filaments can easily 

 be watched struggling violently, and may sometimes be seen to break 

 from the parent cell and to dart away among the corpuscles, leaving 

 the residue of the gametocyte, with its melanin, an inert and apparently 

 dead mass. 



Now it is not to be supposed that such an extraordinary pheno- 

 menon as this — which was observed by Laveran during his first 

 investigations — could be witnessed without exciting the liveliest 

 curiosity. As a matter of fact a hot controversy rose regarding it. 

 Laveran, Danilewsky and Mannaberg maintained that the phenomenon 

 is a vital one — that the motile filaments are living organisms, and 



* Nature, August 3, 1899. 



