Stegomyia fasciata 
:a8 
Experiment XIX. 
A number of tubes were prepared and sterilized containing appropriate quantities 
of the following in distilled water; sterile filtrate from a culture of B. coli with white 
of egg, treated so as to form a fine precipitate; filtrate of B. coli with milk in which 
the casein particles had been increased in size; and B. coli filtrate without any 
addition. 
Larvae were taken from a sterile tube of peptone water in which they had hatched 
16 days previously; they were still in the first instar, having made barely per¬ 
ceptible progress during 16 days. Shght progress followed over a protracted period 
in the tubes (containing white of egg and milk) which remained sterile, but in aU 
cases it came to a standstill when the larvae wei’e still small, in the second or third 
skin, after which they pined aw’ay and died. In one or two instances sterility broke 
down and was generally followed by a sudden spurt of growth. In most cases, 
however, the growth of bacteria proved over-violent and killed the insects ere they 
had time to develop. 
Experiment XX. 
The treated milk was also added to tubes of yeast extract solution, peptone 
water and manure water, in which eggs had hatched and the larvae were unable 
to develop ow'ing to the sterile conditions. In no case did the addition of the 
milk produce any change in the scarcely perceptible progress that the larvae made. 
Sterile filtrate of B. coli in the proportion of about 1 in 10 was added to these tubes 
after the lapse of JO or 12 days, and also to sterile tube.s of insect broth and 3% 
yeast extract solution. During 5 days no change resulted from the addition of 
the filtrate, the scarcely perceptible growth that was taking place in some only of 
the tubes was not appreciably quickened, in other cases when the larvae had already 
arrived at the marking time phase no progress was induced. 
The following notes refer to some of the tubes mentioned above. 
Insect broth. A larva that had hatched under sterile conditions (see Experi¬ 
ment XIII) lived in the tube for 34 days when it was still in the first skin; 1 in 7 
of B. coli filtrate was added. Xo change took place in b days; then the tube was 
inoculated with B. coli ; eggs which had been lying dormant in the tube for 39 days 
hatched as a result. Rapid growth of the larvae followed, but it is not possible 
to say definitely if the larva which had been marking time for so long weis one of 
those which developed to adult stage within 10 days; 4 had pupated and 3 
and 1 $ emerged in due course. 
Peptone water. The two or three larvae which hatched from the eggs pipetted 
into the tube made no progress during 18 days; the treated milk was added— 
the larvae made no progress and died out within three weeks. Eggs had been 
lying dormant in this tube for 39 days. The tube was inoculated with B. coli and 
these eggs hatched within a few hours. The larvae commenced to make rapid 
progress, but their history was not followed up. 
Yeast extract in distilled water. Three or four larvae hatched from the eggs 
placed in this tube. They made no perceptible progress during a week; treated 
milk was added to the tube. After 20 days two of the larvae had passed the first 
moult; 76 days after the addition of the milk the larvae were still in the second or 
