496 
Stegomyia fasciata 
did as a matter of fact emerge rather freely from these eggs under 
sterile conditions, the evidence from Experiment XXIII, in which also 
they were not allowed to dry before sterilization, is entirely negative, 
the number hatching under sterile conditions being small; while in 
Experiment XXV in which dried eggs were used the percentage hatch¬ 
ing in some of the tubes was considerable. It is probable that the 
problem is a complex one, two or more factors being concerned. 
The results of the experiments on eggs is so far clear and decisive 
in regard to the fact that the presence of bacteria, yeasts and, less 
definitely, moulds, does exert a stimulus causing eggs to hatch that 
would, apart from their presence, have remained dormant for a longer 
period. It also seems definite that this stimulus is less powerful, or 
may be altogether ineffective, if killed cultures or sterile filtration and 
extracts of bacteria or yeasts are used. The difference is apparently 
one of quantity not quality, its extent being chiefly dependent upon 
some variation in the susceptibility of the eggs. 
Section B. Larvae. 
Unsterile co7iditions. 
The fact that the larvae greedily consume clumps of bacteria or 
yeasts [S. cerevtsiae) removed from agar cultures has already been men¬ 
tioned in the introductory remarks. This rough test is open to the 
objection that what the larvae struggled for was not the organism but 
the organic matter on which they were living, or by-products produced 
in their development. 
In Experiments V and VI, B. coli washed by centrifuging were given 
as food to a batch of larvae, while to an equal number in a similar 
({uantity of water no food was supplied ; the unfed batches constituting 
controls. The results show conclusively that the larvae cannot only 
live, but thrive on the bodies of bacteria. 
Sterile conditions. 
These early trials, followed by a series of experiments (VII, 
VIII, IX and XI), afford examples, in which the eggs were sterilized 
and transferred by Pa.steur pipette into tubes containing various sterile 
media, the object being to ascertain if it was possible for the larvae to 
develop under sterile conditions. In the main the results are clear and 
decisive; while sterility is maintained, larval development is either 
inhibited or proceeds excessively slowly in conjunction with a high, or 
