REPORT OF THE MALARIA EXPEDITION. 
13 
were fertilized, while they could not be induced to feed copiously. All proved negative as regards 
the parasites. As, however, it was already certain that all the insects belonged to hospitable 
species, this result was interesting as tending to show that cultivation experiments may fail if not 
performed under natural conditions. The subject is discussed later [^paragraph 20], 
After our departure. Dr. Fielding-Ould examined numerous Anopheles caught at Wilber- 
force, and in the houses of natives suffering from fever, and found the parasites in 18 %. His 
observations on Culex were negative. 
We made no observations on Culex or other insects. 
We conclude that both Anopheles costalis and Anopheles funestus are hospitable to the human 
Haemamoebida?. We think that A. costalis is hospitable to all three of the human species ; and 
A. funestus certainly to H. malaria^ and probably to H. vivax. But we made no observations 
regarding the connection of the latter with H. precox. 
10. The Haemamcebidae in the Definitive Hosts. — The stages of the human parasites 
in Anopheles are essentially tiie same as those of H. relicta, first described by one of us in a gnat 
of the Culex pipiens type — a fact already recorded by Koch and the Italian observers. In Plates I., 
II., and III. we give a series of photographs of all these Ha?mamoebidas in the gnat. 
The following small differences between the human species and H. relicta were noted 
by us : — 
(i.) The capsule of the zygotes of the human species is somewhat thinner ; so that the 
youngest zygotes are more difficult to detect, and sometimes ruptiu e under pressure 
of the cover-glass — a thing which rarely happens in H. relicta. 
(2.) The mature zygotes seem to contain more blasts than do those of H. relicta. 
(3.) The melanin appears to remain longer in the human species. 
(4.) The blasts are shorter and thicker, and less bent and twisted, than those of H. relicta — 
but differences in the strengths of the salt solutions used may account for this. 
(5.) In the human species the blasts tend to lie in the salivary cells in bundles, like bundles 
of faggots, and not irregularly like those of H. relicta — at least this was very 
noticeable in two of the gnats, numbers 17 and 99. 
(6.) Owing to the dilatation of the proximal ends of the salivary ducts in Anopheles^ the 
blasts can be more easily distinguished within these channels. 
It is important to note that, though elements like those provisionally called " black spores " 
by one of us were frequently seen in the Freetown Anopheles., they were never detected within the 
capsule of the zygotes {^paragraph 24'\. 
The young zygotes of H. vivax were always immediately recognisable by the numerous 
minute granules of light brown melanin which they contained. The youngest zygotes were, in 
fact, almost identical in appearance with the mature gametocytes in the human blood. As the 
parasites advance in growth, the melanin seems to decrease in quantity and become slightly paler ; 
but it was sometimes still to be found even in the most mature zygotes — which, moreover, were 
of very large size, and contained very numerous blasts. 
