35 



According to Pictet (1893), the eggs of Bomhyx can be 

 stored at - 40° ; this temperature is not only non-lethal to 

 the eggs but it is injurious to the germs which might 

 infect the eggs. 



Donhoff (1872) exposed for 5 hours Bomhyx eggs con- 

 tained in small glass vials to the temperature of -15° to 

 -21° of an ice-salt mixture. The eggs were then placed 

 into little bottles tied shut with linen and the bottles put 

 into a box which Donhoff carried on his breast by day and 

 took to bed with him by night. After a few weeks all the 

 eggs hatched. 



On the other hand, according to Pictet (1893), ant eggs 

 are extremely sensitive to cold. They are all killed be- 

 tween 0° and -5°. The sensitivity increases with the 

 stage of development and some more advanced eggs died 

 when exposed to 5° for a few hours. 



Bach and Pemberton (J. Agr. Res., 5, 657, 1916) found 

 that no eggs of the Mediterranean fruit fy survived cold 

 storage at 4.5° to 7.2° for 7 weeks, or at 0.5° to 4.5° for 3 

 weeks or at 0.0° to 0.5° for two weeks. (From Uvarov, 

 1931.) 



According to Hase {Ztschr. /. Parasitenli., 2, 368, 1930), 

 an exposure of bedbug eggs for 3 to 20 days to a tempera- 

 ture of 2° was harmful enough to prevent the hatching of 

 a number of eggs, in which only an initial development 

 was found to take place. 



According to Eahm (1920 and 1923), the eggs of the 

 tardigrad, Echiniscus, in moist moss, survived two suc- 

 cessive freezings of 35 minutes each at - 81° and those of 

 another tardigrad, Maerobiotus, were not killed by a sud- 

 den immersion, in the moist condition, in liquid air or in 

 liquid hydrogen. 



Schenk (1870) exposed fertilized eggs of Rana tempo- 

 raria to - 3° for one hour during w^hich time the jelly layer 

 had frozen hard; he found that, after thawing, the eggs 

 developed. Fertilized eggs exposed for one hour to - 7° 

 showed no further development after thawing. ^Mature 

 unfertilized eggs of Bufo cinereus, taken from the body of 



