5G, Roberg: Bacterial Infections 323 
organisms on their surfaces or in their intestinal tracts; and 
for what length of time do they remain infective? 
4. Which media are preferably chosen by these flies for 
breeding ? 
5. Biological features concerning the development of the fly. 
6. Ability of the flies to pass through small apertures. 
TECHNIQUE EMPLOYED IN EXPERIMENTS AND A CONSIDERATION OF 
THE FINDINGS ELICITED 
In the four series of experiments outlined here-are recorded 
the results of positive findings. For the purpose of brevity and 
clearness the positive findings are described separately from the 
negative. 
The obstacles encountered and the technique developed in the 
course of the experiments are best described before outlining the 
series of experiments. ; 
In series I, concerning the biological neceiine of Aphiocheta, 
little difficulty was met with. The minute Phoride were readily 
trapped, as the vessels used as traps were placed in a screened 
room which excluded the larger species of flies. As traps were 
covered with cloth gauze, only minute flies could gain entrance 
therein. When a considerable number of flies had been caught, 
they were kept imprisoned until they had laid their eggs. 
These imprisoned flies, when seen through the glass wall of 
the vessel containing them, for the most part presented abdomens 
of a brownish yellow ground color, with transverse blackish 
stripes. The thorax was characteristically hunched. These 
characteristically colored and hunched-back flies were uniform 
in size and averaged 2.5 millimeters in length. A number of 
these flies were removed from the traps by covering the traps 
with a glass funnel, and as the flies passed up the stem of the 
funnel they were caught in a glass Erlenmeyer fiask inverted 
over the upright funnel stem. When killed and mounted on 
needles, they were found to be Aphiocheta ferruginea, as 
previously stated and described. 
These flies, having a characteristic appearance and color, could 
be readily recognized in the vessels containing them; therefore, 
as they could be seen as the predominating flies contained in the 
traps, the eggs when laid and hatched out would give origin to 
a new generation of flies, of which Aphiocheta ferruginea would 
predominate greatly over others which might be present and 
not recognized on account of their similarity to Aphiocheta. 
Among these brownish yellow fiies could be seen a few which 
