572 RONALD ROSS AND R. FIELDING-OULD. 



which are known to be comuiuuicated among oxen by the 

 cattle tick, Boophilus bovis. 



Group II. Organisms apparently allied to the Gregari- 

 nidfe ; found in reptiles; numerous species. 



Group III. Intra-corpuscular amoebEe or myxopods found 

 in man, monkeys, bats, birds, and possibly frogs. Four 

 species are known to undergo further development in gnats. 



It is this last group which claims our attention at present. 

 The diagrams are meant to illustrate a discourse delivered 

 by one of us at the Royal Institution {' Proceedings of the 

 Roy. Inst.,' 1900, and also 'Nature,' March 29th, 1900); but 

 we shall now give a description sufficient to enable the 

 reader to follow the life-history from this paper alone. The 

 figures show the appearance of the parasites as seen in 

 unstained preparations — the cytology of some of the stages 

 (figs. 53 — 60) in the gnat not yet being sufficiently estab- 

 lished to warrant illustration in a scheme of this kind. 



We adopt the name Hgemamoebid^, Wasielewsky, for 

 the whole group. At least three species occur in human 

 beings (producing the different varieties of malarial fever) ; 

 one species in monkeys, three in bats, and two in birds. We 

 illustrate only the species found in man and birds, those of 

 monkeys and bats being closely similar to the human species, 

 (but, so far as we know at present, not identical). The deve- 

 lopment of four of the species has been followed in gnats. 

 The three human species develop in gnats of the genus 

 Anopheles, while one of the avian species (Hfemamoeba 

 relicta) lives in gnats of the Culex pipiens type. The 

 insect hosts of the remaining species have not as yet been 

 found. 



So far as we know, the life-history of all the species is 

 practically identical, and is as follows. The youngest 

 parasites are found as minute amoebul£e living within or upon 

 the red corpuscles of the vertebrate hosts. Each contains a 

 nucleus, which stains by the Romanowsky method. Growing 

 rapidly in size, the amoebulse convert the haemoglobin of the 

 containing corpuscles into a varying number of brown or black 



