INSECTS AND PLANTS IN MID-WINTER 7 



in the Lime Hawk-moth, Lacordaire in Leucania, 

 Xambeu in the Goat Moth. More than two hundred 

 years ago Lister had noted that caterpillars and pupae, 

 though frozen till they became brittle and tinkled 

 against glass, were capable of reviving completely. 

 It has even been found possible to freeze a Frog to a 

 rigid body without destroying life, but the trial rarely 

 succeeds. In all these cases it is probable that a part 

 only of the contained water turns to ice. Complete 

 freezing would remove water from the albumens and 

 other organic compounds of the body, and would be 

 certainly fatal. An extremely low temperature \vould 

 be necessary. Ten hours' exposure to 16 C. was 

 required to solidify the contents of a Fowl's egg, 

 which were even then, in all probability, only partially 

 frozen. 1 During the freezing of many solutions 

 and mixtures partial solidification sets in first, and the 

 fluid residuum becomes more and more difficult to 

 freeze, as solidification proceeds. 



Even when we are aware of the difficulty of freezing 

 an animal completely, we cannot but wonder that 

 Mammals, Birds, Insects, and many other living crea- 

 tures should survive the winter cold of the far north. 

 I would not undertake to explain how animals which 

 are unable to replenish their store of energy can 

 endure for months together a temperature at which 

 mercury freezes. 



The thawing of frozen tissues is in most cases even 

 more dangerous than the freezing itself. Diffusion- 

 currents break up the microscopic structures, and 

 change the composition of the fluids. In the same 

 1 Kochs, Biol. Centralblatt, 1892, 1895. 



