28 
April, 1934. 
The Queensland Naturalist. 
especially during the period when the latter was free to 
devote time to scientific enquiry, naturally was imbued 
with the importance of Filaria spp. and their relation to 
disease. The elder naturalist, as is well-known, working 
independently, had not only confirmed in 1876 by investi- 
gation, Dr. T. R. Lewis’s earlier discovery of microfilaria 
inhabiting human blood; but also in the same year, 1876, 
had found occurring in a lymphatic abscess in man the 
sexually mature form Fill aria Bancrofti , and that Lewis 
himself also met with in a blood clot in the following year. 
Further, a third worker, Dr. P. Manson, had discovered 
the larval haematozoon in the stomach of mosquitoes and 
exhibiting new higher life phases than those characteris- 
ing the microfilaria or larvae in the blood, and that pointed 
to the genetic relation between larvae and adult, as occur- 
ring in man. Its further transformations, and the migra- 
tion of the nematode Filaria with the mosquito need not 
now be detailed. But these discoveries created far-reach- 
ing world interest, since Filaria infestation of man im- 
plied the incidence of widely occurring serious ailments 
of one kind or another in man, and new factors relating to 
their causation awaited research. It still remained to be 
found out, however, how the now shortened and thickened 
filaria-worm was transferred from the insect to man. Many 
conjectural explanations were advanced, the one most fav- 
oured being the emigration of the still immature filaria 
from the mosquito-host to drinking water and thence to its 
final host — man. Experiments conducted by many workers, 
however, failed to show that, any one of the suggested 
methods held good. 
It was Dr. T. L. Bancroft who, in bringing his own 
observation on the mosquito-economy to bear on the ques- 
tion, discovered how this passage from mosquito to man 
was brought about. He demonstrated that a certain num- 
ber of days must elapse after the mosquito had acquired the 
larval filaria (microfilaria) from man’s blood before effec- 
tive transference could ensue, since it was necessary that it 
must first have atttained to a certain stage of development, 
covering a period of 16-17 days, and that a time limit was 
thus involved. He further was able to show that in experi- 
ments conducted by others the filaria-infested mosquitoes 
had died prior to this event, and to this time limit being 
reached, and also that this fatality had happened since the 
necessity of feeding the mosquitoes had been lost sight of. 
The foods they required, he had discovered, was not blood, 
but simply ripe bananas, or, better still, dry dates as sold 
by the grocer. He found also that any larval filaria from 
mosquitoes would soon die on entering water, but that, on 
the other hand on attaining the proper stage of growth 
