490 
Stegomyia fasciata 
Ejfect of acidity—sterile conditions. 
Experiment IX. Early in the course of the experiments the possi¬ 
bility of the effects resulting from the addition of living bacteria to 
media such as peptone water or peptone broth being due to acidity 
was considered. A dilute solution of HCl adjusted to give an acid 
reaction similar to that in a tube in which the growth of bacteria caused 
the eggs to hatch produced no response during three days while the 
eggs were lying dormant in tubes of peptone water and peptone broth, 
but within 18 hours of the inoculation of these tubes with bacteria all 
the eggs hatched. A further trial with another tube of peptone water, 
belonging to the same series, in which the eggs had been dormant for 
8 days, also showed a negative result during a period of 48 hours. The 
acid addition to this tube was increased so as to cause a much more 
marked reaction than that in the first trial. After inoculation with 
bacteria one egg hatched within 18 hours and another on the following 
day, and the remaining two on subsequent days. This halting response 
was apparently due to the slow and feeble development of the bacteria, 
owing to the extreme acidity of the tube. The larvae in the tube 
made relatively very slow progress. 
We conclude from the results of the five experiments that the marked 
response of the eggs was due to the presence of bacteria or their pro¬ 
ducts, apart from either the acidity or alkalinity produced. 
Ejfect of introduction of different living bacteria into tub/^s of sterile 
media such as peptone water in which the eggs are lying dormant. 
Staphylococcus pyogenes aureus. Experiment IX (page 506). A 
tube of peptone water in which eggs had been lying dormant for 
15 days was inoculated from a culture of S. aureus. The bacteria 
failed to grow and the eggs did not hatch. Two days later the inocu¬ 
lation was repeated from the same culture, this time with success and 
the eggs all hatched within 16 hours. 
Bacillus coli communis. Experiment XI (page 508). A tube of 
peptone water in which eggs had remained dormant for 11 days was 
inoculated from a culture of B. coli. All the eggs hatched within 18 
hours. 
Experiment XX. In a tube of sterile broth, made from dead 
insects, only one egg out of a number hatched. On the 34th day a 
quantity equal to about 1 in 7 of filtrate from a broth culture of B. coli 
was added. This had no effect on the dormant eggs, and the tube on 
