36 
REPORT OF THE MALARIA EXPEDITION. 
these bodies were never seen within the zygotes, wliile they often occurred, mixed with what 
looked like segments of a fungus, within the sheath of certain muscle-fibres {e.g-y of the stomach), 
and indeed appeared to have no relation at all with the Haemamoebidas. 
If these bodies are indeed forms of the parasites, they will certainly suggest another life- 
cycle. In this case they will probably infect larva?, for the purpose of continuing the species from 
gnat to gnat. The probability of one of them ever reaching man's digestive or respiratory tracts 
must be so remote that we can scarcely imagine that they are provided for this purpose. In the 
meantime it remains to be proved that they have any connection with the parasites at all. 
It siiould also be noted that many full-grown zygotes do not contain blasts, — a fact which 
suggests that they >na\ be set apart for some other purpose. At the same time they may merely 
be zygotes which for some reason have not been able to ripen as early as the rest. 
The method of diffusion of the disease by inoculation through the proboscis of gnats 
is so perfect a one that, now we are acquainted with it, it seems difficult to imagine the 
existence of any other — such, for instance, as the clumsy methods which in our ignorance we 
formerly imputed to nature. In the transference of the parasites from man to man by gnats, 
there is an economy which would not have existed had nature sown the organisms broadcast 
through the soil or air, on the chance of one of them occasionally infecting a human being. 
To sum up, then — there appears at present to be no strong evidence, based on our 
knowledge either of the disease or of the parasites, in favour of the view that the latter possess 
any other life-cycle besides the one which is already known. On the other hand, the fact 
that malarial fever is communicated from sick to healthy persons by Anopheles seems sufficient 
to explain all the well-established laws regarding the prevalence and diffusion of the disease. 
