488 
Stegomyia fasciata 
Methods. 
Sterilization. One section of the experiments with eggs and larvae 
was carried out with unsterilized eggs, and larvae newly hatched from 
eggs put into clean water which were invariably found to be infected. 
In the other section attempts were always made to render the eggs 
sterile before use, and in spite of a number of probably unavoidable 
failures experience showed that with careful precautions it is quite 
possible to work under sterile conditions. 
The following methods for sterilizing eggs were employed : 
(а) Eggs were placed in a minute cotton bag, dipped into 2 % 
lysol for 5-10 minutes and washed in boiled water. The bottom of 
the bag was then snipped off and allowed to fall into a tube of broth. 
This method gave a few successful results, in many cases, however, 
sterility broke down. 
(б) Eggs were washed in warm (about 90° F.) soft soap and water 
for 15 minutes, then in 2 % lysol for 5-10 minutes; in boiled water for 
5 minutes and then transferred by Pasteur pipette to tubes containing 
the sterile water or media. 
This method gave many successful results, but there were some, 
breakdowns in sterility, chiefly due to moulds and sporing bacteria. 
(c) Eggs were washed in tap water by using a fine jet in a deep 
pan of water; they were then pipetted into weak lysol, about 0-5 %, 
and vigorously washed round by a jet; after a few minutes they were 
transferred to 2 % lysol and the stirring by jet repeated. After this 
they were again placed in 0-5 % lysol and then into boiled water. 
Methods (6) and (c) were varied in minor detail from time to time. 
(d) A method of sterilization by formalin vapour was tried, but it 
was too drastically applied in the first instance, the larvae dying on 
emergence from the egg. Although after suitable development it would 
possibly have given favourable results, it was not proceeded with, 
owing to the successful results obtained with (c). 
Towards the close of the experiments it was found that the work 
of sterilization was rendered more certain, and less elaboration of the 
sterilizing process was necessary if more care was bestowed on obtain¬ 
ing eggs less liable to be covered^ with a number of species of bacteria, 
more especially those forming spores. Arrangements were therefore 
made to rear the parents from which it was proposed to obtain eggs 
for experiment under conditions which rendered the presence of an 
infection of sporing bacteria and moulds less likely. A breeding pan 
