A. W. Bacot 
71 
The first tube was clear after six hours but showed signs of becoming turbid 
in nine hours and were distinctly cloudy in 12 hours. The second tube was 
markedly turbid in nine hours. 
The remaining two pupae were similarly treated and gave an identical result. 
These experiments seem to prove that either the pupal gut or the 
inner surface of the puparium is contaminated. 
In view of the experiments about to be described it seems certain 
that the gut is infected but it may very well be that the puparium 
which contains the moulted portion of the larval gut is also to some 
extent contaminated, which would explain the slowness of growth in 
those controls which showed infection, since some passage of the broth 
might take place through the air passage after a lengthy soaking. 
(b) Experiments on Adult Flies. 
1. Several pupae were sterilized in 3 ®/o lysol for two minutes and then placed 
in clean sand in a clean tube, the object being to prevent any possibility of the 
flies on emergence becoming infected by sucking at the moist infected sand of the 
stock-pot or the outside of the puparium. 
Four flies taken from the above tube were placed in 5 ®/q lysol for five minutes, 
then placed in a tube of broth, shaken up and allowed to remain in it for five 
minutes; then they were removed to a second tube and torn up with .sterilized 
needles. Both tubes wei’e incubated at 29° C. In 12 hours there was no result, 
in 22 hours the second tube was turbid ; after a further period of 12 hours the 
first tube also showed signs of growth and finally became turbid. 
2. Four flies from the same tube were placed in 5®/o lysol, shaken up, and 
allowed to remain in the solution for seven minutes, they were then washed in 
sterile distilled water and transferred to a tube of broth in which they were shaken 
up and allowed to remain for five minutes ; they were then taken out, put into 
a second tube, and torn up with sterilized needles. Both tubes were incubated at 
29° C. In 12 hours there was no result, in 22 hours the second tube was turbid; 
the first remained sterile. 
3. Two pupae were kept in 10®/o lysol for seven minutes, then placed in clean 
sand in a clean tube. 
One fly emerged and was placed in 5 ®/o lysol for three minutes, removed to 
a tube of broth, shaken up, and allowed to remain in the solution for eight minutes, 
then put into a second tube and torn up with sterilized needles Both tubes were 
incubated at 29° C. In 22 hours the second tube produced a culture ; the first 
remained sterile. 
4. A number of pupae were taken from the general stock and placed on 
a sheet of paper. From one of them a fly emerged while under observation. It had 
no opportunity of sucking and was at once placed in 5 ®/(, lysol for four minutes, and 
then transferred to a tube of broth and shaken up. It sank to the bottom of the 
tube and was allowed to remain there for five minutes ; the fly was then placed in 
a second tube of broth after having been torn up with sterilized needles. {Note: 
