Gut of an Insect during Metamorphosis. 4.99 
in which the ends of the puparia were varnished or waxed. 
The larvae from which the puparia were reared were again 
supplied with food infected with B. pyocyaneus, but the 
possibility of infection by other species of Bacteria by way 
of their food was not specially guarded against. 
The ends of a number of puparia were varnished, and a 
few had the ends dipped in hot beeswax, the object being 
to seal the stigmata and any possible opening that might 
exist by way of the scar of the larval anus. 
These puparia were then soaked in 10 per cent. solution 
of lysol or formaline for periods of from 9 to 39 hours, in 
most cases 10 or 12 hours. In some instances they 
were washed before the transference to tubes of broths, 
in others the washing was omitted. Events prove that 
washing was devoid of significance so far as the result 
is concerned. 
After allowing the puparia to remain in the tubes of 
broth that formed the controls for periods of from 2$ to 
194 hours they were pierced or cracked in the culture 
tubes. In two instances second controls were used. These 
had respectively 14 hours first control, 12 hours second ; and 
3 hours first control, 8} hours second. 
In all, ten experiments were made: nine with varnished, 
and one with waxed puparia. 
Every culture tube produced a growth, even after so 
long a sterilisation as 39 hours in 10 per cent. formaline. 
Nine cases in which broth was used show clear evi- 
dence of B. pyocyaneus being present. One experiment 
in which an agar slop was used in place of the broth is 
not definite. 
Of the controls, seven tubes were sterile, and five were 
infected. This number includes the two second controls, and 
that of the experiment where the puparia were allowed to 
remain in the control tube for 194 hours. 
One tube alone, however, shows B. pyocyaneus in a 
control. In the other four instances the growth is 
apparently that of a strictly aerobic organism, as the 
broth, after the formation of a scum, became clear and gave 
sterile slides under the microscope. It would seem, there- 
fore, that varnishing or waxing, if efficiently carried out, 
prevents the broth being infected from the interior by 
way of the stigmata; and supports the contention that 
the infection of controls in various experiments was due 
to soakage through the air passages of the puparia. 
