206 
as the harvest of the eggs of the year 1915—1916 took place in the 
spring and the summer, and that of the succeeding year in the autumn 
and the winter. The room was heated, it is true, and, with a single 
exception, the cultures were transferred into the incubator, but both 
the former and the latter were done only when the cold became 
unpleasant. In the experiment year 1917—1918 the winter was 
severe, with long continued frosty weather. The following experience 
was obtained. 
A small series of cultures, which could not be accommodated in 
the incubator, stood free in the laboratory. In the daytime the room 
was heated, and during the frost it was heated slightly at night 
too, so that the minimum temperature was never below 7° C. This 
is known with perfect certainty as the temperature of the room and 
the incubators was regularly noted down 3 times a day. From these 
notes it appeared that the temperature in the early morning and 
late at night never sank below 7° C. 
If one assumes, to be certain, that the temperature, at a given 
moment may have gone down to 5° C. before the thermometer 
indicated this sinking, it may be stated as a fact that this tempera- 
ture is already deadly to the eggs. In the above-mentioned series of 
cultures the mortality was so high that only a few eggs were hatched. 
From two jars, each of which contained 1250 eggs, not a single 
larva was got from one of them, and only two larvae from the other, 
even after the eggs, which still looked rather normal, had been kept 
in the incubator for a long time. This great sensitiveness of the eggs 
to low temperatures, was not further studied. On another occasion 
this circumstance will be reverted to. These observations have been 
recorded only to point out that the abnormal mortality of the year 
19i16—1917 may possibly be connected with temperature influences. 
The 66517 eggs experimented on in that year were distributed 
over 5 series of 101 separate cultures in total. 
In one series of 7 cultures 24500 eggs had been put, and in 4 
series 42017 eggs in 94 cultures. 
The average mortality of the first series with 7 cultures amounted 
to 53.7°/. For that of the 4 other series the figures were 
2nd series of 7 cultures 8500 eggs with 32.2°/, dead 
SNC" hee seal) 3 4661 „ > OS ee 
AO vanen An in 21472 „ zt Aedes 
Oth. 2 svet eee 5 7384 „ ze OO SLATE 
Total — 94 cultures 42017 eggs with 34.4°/, dead. 
—_ ss CUM 
