E. E. Atkin and A. Bacot 
505 
The supply of washed B. coli in the pan was renewed. By the 6th day all the 
larvae were in the fourth instar. One pupated on tlie 8th day, and the remainder 
had pupated by the 10th day. Two specimens emerged on the 12th day and 
two more $$ and a cJ by the 13th. 
The pan was then restocked with 5 newly-hatched larvae, but no fresh food 
given. All the larvae were in their second instar by the 3rd day; they reached 
the third instar by the 7th day, having exhausted the food supply, and were still 
in the same stage 10 days later. 
Experiment VI {unsterilized conditions). 
Abiliti/ of larvae to develop on a diet of bacteria. 
Temperature 75° F. 
Into one of two beakers, each containing 200 c.c. of tap water, was placed 
sufficient of a washed culture of B. coli to cloud the water. 
20 newly-hatched larvae were placed in each beaker, and card covers placed on 
top to exclude dust. 
Control. No appreciable progress, beyond the expansion of the head, took place 
within a week, then 8 died within 24 hours. Seven days later only 6 of the 20 larvae 
were living, 3 of which had passed the first moult. After another week (21 days 
from start) these 6 were still living, and making slow progress. 
After 75 days there were two survivors, which by this time were slender larvae 
in the third instar. A little water mixed with faeces and therefore containing 
bacteria was added to the pan. Rapid growth was noticeable by next day; 1 
larva had pupated within 5 days, and by the 9th day—84 days after hatching— 
2 adults were bred. 
The larvae given B. coli made rapid progress; all were in the third instar by 
the 4th day; 16 had pupated b}^ the 9th day; 4 and 1 ? emerged on the 11th day 
and the remainder followed within a few days; the last, which had lagged in the 
larval stage, taking 16 days. 
Experiments under sterile conditions in tubes containing nutrient media. 
Experiment VII. 
Eggs sterilized by Method a were pipetted into a tube of peptone broth, after 
a night at 75° F., the tube was allowed to cool to 60° F., and some of the eggs 
hatched. The larvae showed no sign of growth after 48 hours at 75° F. The tube 
was then infected with B. coli; within 18 hours at 75° F. the broth was cloudy and 
the increase in size of the larvae was very obvious. 
A curious feature of the experiment was that small bubbles of gas which were 
liberated by the fermentative action of the bacteria, formed on empty eggs, frag¬ 
ments of egg-shell etc. lying at the bottom of the tube, floating them up to the 
surface, when, the bubble becoming detached, they sank to the bottom and th® 
process was repeated. Similar bubbles formed at the apex of the syphon tubes of 
the larvae, causing them Jo float upwards in spite of their struggles to swim down¬ 
wards. So regular and constant was this process that the larvae got .but little time 
for undisturbed feeding, and their growth was slow in comparison with their rapid 
start. 
