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'three to five days, while the larvae appeared to feed in a desultory 
‘manner. The time for their natural transformation to the pupae 
‘comes and goes and they still remain as larvae. The foulness of 
‘the water, due to organic decomposition, appears not to affect 
‘them, but on the other hand the lack of proper food seems to cause 
‘them to remain in an indefinite larval state until after three weeks 
‘or more they gradually begin to die.’ 
A very simple and satisfactory method for keeping the breeding 
tanks fresh and clean and free from decomposition was devised. 1 he 
principle involved is that of aeration—preventing the development 
of an anaerobic condition in the water of the breeding tank by 
passing a fine jet of air through the water of the tank once or twice 
a day. It is well known, of course, that if natural water from 
streams, pools or ditches be placed in a glass tank, exposed to 
diffuse sunlight and undisturbed, after a few days the chloroph) 11- 
bearing plants begin to disappear, a pellicle forms on the surface of 
the water, which contains bacteria, spirilla, flagellated protozoa, 
amoebae, etc. Beneath this surface film decomposition goes on 
rapidly, chlorophyll-bearing forms are destroyed or become 
encysted, and the various insect larvae and water-bugs die. The 
bacteria in the deeper portions of the water aie largely anaerobes, 
and are associated with the putrefactive decomposition of the 
vegetable matter and animal matter in the tank. Banks describes 
exactly the effect on mosquito larvae of this putrefying vegetable 
matter. The odour arising from the tanks suggested the necessity 
of aeration to prevent the growth of the anaerobic bacteria. Acting 
on this suggestion an air jet was devised by attaching a thick g ass 
rod, having a fine capillary central canal to the double bulb o tie 
Pacquelin cautery apparatus and the breeding-out jars aerated tor 
a minute or two morning and evening. 1 he results w'cie lg 1 y 
satisfactory, for the tanks were by this means kept clean an 
wholesome. The algae remained green and vigorous, the larvae 
active and developed rapidly into pupae, the water remaine qui 
dear, in fact, with its floor of sand and clay and a few s P n S s ° 
green aquatic plant, such as Lenina, looked as tempting to rm 
as spring water. The temperature of the water in the tan^s ian fa e 
between 72° and 84°. 
