74 



0° without coii^c'latioii, or an exposure of 2 to 3 liours to 

 - 1.2° ill the eoiigealed state; they were killed after having 

 l)('('ii frozen at -2° for 2 hours. The authors, who are 

 interested in the study of the anabiotic state, consider the 

 temperature range from 0° to -2° as the favora])le one 

 for that pur})ose. They reported also the somewhat sur- 

 prising fact that dried worms, that is, worms in which 30 

 to 40 per cent of the normal water-content was removed, 

 were killed when the temperature was lowered below 

 - 1.2°, though drying alone did not affect their vitality. 

 (The normal water-eoiilent was 82.8 per cent of the body 

 weight.) 



5. Mollusl's. Koedel (1886), who exposed to low tem- 

 peratures land or water snails, either in the air or in 

 water, by immersing into freezing mixtures glass tubes 

 containing the animals, reported that PJauorhis and Lim- 

 }iaeus were killed in times varying from 15 minutes to 5 

 hours at air temperatures from -8° to -4°, the younger 

 and smaller animals offering less resistance, and that 

 Heli.r pomaiia was killed in 10 hours at -10°. None of 

 the mollusks investigated ever survived a complete freez- 

 ing. In the unfrozen state, in ice-water at 0°, Limnaeus 

 could be kept alive for days. It would follow from these 

 data that congelation is the main lethal factor. 



According to Yung (1888), (cf. also Pictet, 1893) the 

 snail, Helix pomatia, survived after having been for 20 

 hours at an air temperature of -130° in Pictet 's refrig- 

 erating ''well" {pu'its frigorifique). This surprising re- 

 sult is always described in the literature among the several 

 achievements on reviviscence reported by Pictet. 



Fischer (1930) found that Helix pomatia, kept for 8 

 hours at an air temperature of -5°, survived, while at 

 temperatures of -6°, -7° and -10° they always died in 

 less than 5 hours, in spite of all precautions for slow thaw- 

 ing. According to him, the air temperatures favorable 

 for hibernation are between 0° and - 5°. 



Kapterev (1936) asserts that he "often succeeded in 

 reviving mollusks (Planorhis) that had been frozen in the 



